KR20160014641A - Foamed multilayer polyethylene resin sheet, and glass-panel slip sheet - Google Patents

Abstract

(A), a polymeric antistatic agent, and a physical foaming agent, and a second melt for forming a foamed layer, wherein the first melt for forming a foamed layer and the polyethylene resin (B) Wherein the polyethylene-based resin (A) and the polyethylene-based resin (B) each have a n-heptane extraction amount of 0.5% by weight or less at 50 캜, and the second melt for surface layer formation is a polyolefin- And the polymeric antistatic agent is present in the foam layer in an amount of 3 to 15% by weight based on the total of 100% by weight of the polyethylene resin (A) and the polymeric antistatic agent, and the thickness of the surface layer is 2 to 10 탆.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a polyolefin-based resin multilayer foamed sheet,

The present invention relates to a polyethylene-based resin multilayer foam sheet and its use as a sheet for a glass plate.

Conventionally, a polyethylene-based resin foam sheet has been used as a material for cushioning materials, packaging materials and the like. Particularly, a polyethylene-based resin foam sheet having antistatic properties has not been subjected to damage due to poor dust adhesion and flexibility, and thus has been used as a preferable material for a packaging material.

In recent years, the polyethylene-based resin foam sheet having antistatic properties has been used in the fields of packaging of electronic devices and its materials, such as glass plates for liquid crystal panels.

If the glass plate for a liquid crystal panel is contaminated due to the migration of organic substances contained in the foam sheet or the like, it is connected to cause deterioration of the electronic circuit on the glass plate and deterioration of yield at the time of production, .

As the organic material transferred from the foam sheet to the package, antistatic agents of the surfactant type blended for imparting the antistatic property can be exemplified. For this reason, Japanese Patent Laid-Open Publication No. 2005-194433 discloses a polyethylene-based resin foam sheet in which a polymer-type antistatic agent is blended as an antistatic agent. Japanese Patent Application Laid-Open No. 2004-181933 discloses a polyethylene-based resin multilayer foam sheet in which a polymer-type antistatic agent is blended in a surface layer laminated on a foam layer. Compared with a conventional foam sheet using a surfactant, the foam sheet using these polymer-type antistatic agents significantly reduces the amount of migration of organic substances and the like to the article to be wrapped.

The polyethylene-based resin foam sheet using the above-mentioned polymer-type antistatic agent is used as a preferable packaging material and separator for electronic devices and materials thereof because of its excellent antistatic property and low degree of contamination due to migration.

However, even in the case of the foam sheet using the above-mentioned polymer-type antistatic agent, the low molecular weight component contained in the polymer-type antistatic agent itself may be transferred to the article to be wrapped. In addition, It has been found that the molecular weight component may be transferred.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a polyethylene-based resin multilayer foamed sheet having an antistatic property and a very small amount of transfer of a low molecular weight component into a package.

According to the first aspect of the present invention, there is provided a surface layer-forming molten resin obtained by kneading a melted resin for forming a foamed layer obtained by kneading a polyethylene resin (A), a polymeric antistatic agent and a physical foaming agent with a polyethylene resin A multilayer foamed sheet obtained by co-extruding a surface layer laminated on at least one surface of a foamed layer,

The polyethylene-based resin (A) and the polyethylene-based resin (B) are all polyethylene based resins having an n-heptane extraction amount of 0.5 wt%

The blending amount of the polymeric antistatic agent to the foamed layer is 3 to 15% by weight based on 100% by weight of the total of the polyethylene-based resin (A) and the polymeric antistatic agent,

And a thickness of the surface layer is 2 to 10 占 퐉.

In a second aspect, the present invention provides the multilayer foamed sheet of the first aspect of the present invention, wherein the surface resistivity of the multilayer foamed sheet is less than 1 x 10 < ¹⁴ >

In a third aspect, the present invention provides the multilayer foamed sheet of the first or second aspect of the present invention, wherein the multilayer foamed sheet has an apparent density of 15 to 300 kg / m 3.

In a fourth aspect, the present invention provides a glass sheet for a glass plate comprising a polyethylene resin multilayer foamed sheet of any one of the first to third aspects.

The polyethylene-based resin multilayer foam sheet of the present invention (hereinafter, simply referred to as a foam sheet or multilayer foam sheet) is a laminate of a polyethylene-based resin foam layer (hereinafter simply referred to as a foam layer) and a polyethylene Based resin layer (hereinafter, simply referred to as a surface layer). As the polyethylene resin (A) constituting the foam layer and the polyethylene resin (B) constituting the surface layer, a polyethylene resin having a heptane extraction amount of 0.5% by weight or less at 50 캜 is used. The polymeric antistatic agent is present in the foam layer in an amount of 3 to 15% by weight based on 100% by weight of the total of the polyethylene-based resin (A) and the polymeric antistatic agent. The thickness of the surface layer is 2 to 10 mu m. With the above-described constitution, the foam sheet has antistatic properties, and the amount of migration of organic substances such as low-molecular-weight components into the article to be packaged is very small.

The foam sheet of the present invention has a multilayer structure in which a surface layer is laminated on at least one surface of a foam layer and comprises a first melt for forming a foamed layer composed of a polyethylene resin (A), a polymeric antistatic agent and a physical foaming agent, And a second melt for surface layer formation, which is composed of the component (B). In a preferred embodiment, the first melt is prepared by feeding an additive such as a polyethylene resin (A), a polymeric antistatic agent and a foam modifier, if necessary, to an extruder, heating, kneading and melting, , And the second melt is obtained by heating, kneading and melting the polyethylene-based resin (B). The foam sheet is obtained by introducing the first and second melts into a co-extrusion die, laminating them together, and co-extruding them. The surface layer may be laminated on one side or may be laminated on both sides of the foam layer.

Each of the polyethylene-based resin (A) and the polyethylene-based resin (B) has a heptane extraction amount of 0.5 wt% or less at 50 캜. The content of the polymeric antistatic agent in the foam layer is 3 to 15% by weight based on 100% by weight of the total of the polyethylene-based resin (A) and the polymeric antistatic agent, and the thickness of the surface layer is 2 to 10 占 퐉. By the combination of these constitutions, the foam sheet of the present invention is capable of exhibiting antistatic performance, while reducing the organic matters such as low-molecular-weight components derived from the polyethylene-based resin present on the surface thereof, Inhibiting the organic substances such as low molecular weight components normally inevitably contained in the inhibitor from bleeding out on the surface of the foam sheet, thereby suppressing the migration of the organic matter into the package. Since the amount of the polymeric antistatic agent to the polyethylene-based resin (A) does not substantially change before and after the co-extrusion, the polymeric antistatic agent is contained in the first melt for forming the foamed layer, Of the total amount of the polyethylene-based resin (A) and the polymeric antistatic agent is 3 to 15% by weight based on 100% by weight of the total of the polymeric antistatic agent and the polymeric antistatic agent. To 15% by weight.

(PE-LD), linear low density polyethylene (PE-LLD), and the like. The polyethylene-based resin (B) used in the surface layer has a content of ethylene component units in the resin of 50 mol% , High density polyethylene (PE-HD), ethylene-vinyl acetate copolymer (EVAC), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEAK) and mixtures thereof. In general, low-density polyethylene is a polyethylene resin having a long-chain branching structure with a density of 910 kg / m 3 or more and less than 930 kg / m 3. The linear low-density polyethylene is a copolymer of ethylene and an α-olefin having 4 to 8 carbon atoms Wherein the polyethylene resin is a polyethylene resin having a density of 910 kg / m 3 or more and less than 930 kg / m 3 in which molecular chains are substantially linear, and the high-density polyethylene is a polyethylene resin having a density of 930 kg / m 3 or more, do. Of these, low-density polyethylene is particularly preferable in terms of buffering properties.

The polyethylene-based resin (B) and the polyethylene-based resin (A) need to have a heptane extraction amount at 50 ° C of 0.5% by weight or less. When the heptane extraction amount of the polyethylene-based resin (A) and the polyethylene-based resin (B) is less than 0.5% by weight, the amount of the foamed material such as organic matter such as low molecular weight components contained in the polyethylene- Sheet. Further, since a part of the low-molecular-weight component derived from the polyethylene-based resin (A) is transferred to the resin melt of the polyethylene-based resin (B) constituting the surface layer during co-extrusion, migration of the low- It is necessary to use not only a polyethylene resin (B) having a small amount of heptane extraction but also a polyethylene resin (A) having a small amount of heptane extraction. From this viewpoint, the heptane extraction amount is preferably 0.4 wt% or less, more preferably 0.3 wt% or less, and particularly preferably 0.2 wt% or less.

Examples of the polyethylene-based resin having the heptane extraction amount of 0.5% by weight or less include those obtained by extracting and removing low molecular weight components from the polyethylene-based resin with a solvent such as heptane. Among the above-mentioned polyethylene-based resins, those produced by the slurry method or the solution method can be used. Since the polyethylene-based resin produced by the slurry method or the solution method has a low molecular weight component removed in the desolvation step at the time of production, the extraction treatment with a solvent such as heptane is unnecessary, . Even if the polyethylene resin having a heptane extraction amount of more than 0.5% by weight is mixed with the polyethylene resin having a heptane extraction amount of 0.5% by weight or less, the polyethylene resin (A) and the polyethylene resin B).

The heptane extraction amount of the polyethylene-based resin is obtained as follows.

The polyethylene-based resin pellets are pulverized. Approximately 2 g of a 200 mesh-pass sample of the obtained pulverized product is weighed. This was charged into a flask, 400 ml of n-heptane was added, and the mixture was heated under reflux at 50 占 폚 for 48 hours. The resulting solution is filtered, and the solvent is removed from the separated collected residue under heating vacuum. The difference between the weight of the obtained residue and the weight of the injected polyethylene resin is obtained. The amount of n-heptane extracted is the weight percentage based on the amount of the polyethylene-based resin into which the tea was added.

The polyethylene resin (B) preferably has a surface layer laminated thinly and uniformly on the surface of the foam layer. Therefore, it is preferable that the melt mass flow rate (MFR) measured based on the condition D of JIS K 7210-1999 is 1 to 30 g / 10 minutes. More preferably 1.5 to 20 g / 10 min, and even more preferably 2 to 15 g / 10 min, for more evenly laminating.

The polymer layer type antistatic agent may not be contained in the surface layer. However, in a range that does not impair the desired purpose of the present invention of inhibiting the migration of an organic substance such as a low-molecular-weight component into a packaged product, that is, a mixture of a polyethylene resin and a polymeric antistatic agent -Heptane extraction amount is 0.5% by weight, the polymeric antistatic agent may be blended in the surface layer. The blending amount thereof is generally 1% by weight or less in the surface layer. As a result, migration of the organic material from the polymer-type antistatic agent into the package is suppressed to a low level.

Examples of the polyethylene-based resin (A) used in the foam layer include the same ones as the polyethylene-based resin (B). However, the polyethylene resin (A) and the polyethylene resin (B) may be different resins.

As the polyethylene-based resin (A), among the above-mentioned polyethylene-based resins, the melt tension at 190 캜 is preferably 20 mN to 400 mN. The melt tension at 190 캜 is preferably 20 mN or more, more preferably 30 mN or more, and still more preferably 40 mN or more, since it is easy to obtain a foam layer of low apparent density. The melt tension at 190 캜 is preferably 400 mN or less, more preferably 300 mN or less, and still more preferably 250 mN or less, since it is easy to obtain a foamed layer having a low open cell ratio.

The melt tension can be measured, for example, by capillograph 1D manufactured by Toyooko Kikai KK. Specifically, a cylinder having a diameter of 9.55 mm and a length of 350 mm and a nozzle having a diameter of 2.095 mm and an orifice having a length of 8.0 mm were used to set the cylinder and the orifice at a set temperature of 190 占 폚, After leaving for 4 minutes, the molten resin was extruded from the orifice at a piston speed of 10 mm / min, and the resulting cord was hooked to a tension detecting pulley having a diameter of 45 mm, and the retraction speed was 0 m / min The pulling speed is increased by a constant speed so as to reach 200 m / min, and the pulling roller pulls the pulling body to obtain the maximum value of the tension immediately before the pulling body is broken. The reason why the time taken until the draw speed reaches 200 m / min from 0 m / min is set to 4 minutes in order to suppress thermal deterioration of the resin and increase the reproducibility of the obtained value. The above operations were carried out ten times in total by using different samples, and three values in order from the greatest value of the maximum value obtained in ten times and three values in order from the smallest value in the maximum value were subtracted, Is a melt tension (cN).

However, when the melt tension is measured by the above-described method and the string is not broken even if the take-up speed reaches 200 m / min, the melt tension (cN ). Specifically, in the same manner as the above-mentioned measurement, the molten resin was extruded from the orifice in a string, and the string was hooked on the tension detecting pulley and taken out at a constant speed so as to reach 200 m / min at 0 m / While increasing the speed, the take-up roller is rotated to wait until the rotation speed reaches 200 m / min. After the rotational speed reaches 200 m / min, the input of the melt tension data is started, and the input of data is terminated after 30 seconds. The average value (Tave) of the tension maximum value (Tmax) and the tension minimum value (Tmin) obtained from the tension load curve obtained in 30 seconds is referred to as the melt tension in the method of the present invention.

Here, Tmax is a value obtained by dividing the sum of detected peak (acid) values by the detected number in the tension load curve, and Tmin is a value obtained by dividing the sum of detected dip values by the tension load curve Divided by the detected number. Naturally, when the molten resin is extruded from the orifice in the string in the above measurement, bubbles are prevented from entering the string as much as possible.

The polyethylene type resin (A) constituting the foamed layer is blended with a polymer type antistatic agent. The blending amount thereof is 3 to 15% by weight based on the total of 100% by weight of the polyethylene-based resin (A) and the polymeric antistatic agent. If the blending amount of the polymer-type antistatic agent is too large, there is a fear that the low molecular weight component permeates through the surface layer and is transferred to the article to be packed. The blending amount of the polymer-type antistatic agent is preferably as small as possible in the range where the antistatic property is exhibited. When the polymeric antistatic agent is blended in the foamed layer, an equivalent antistatic effect can be obtained even if the blend amount is smaller than that in the non-foamed layer. The reason for this is that if a polymeric antistatic agent is added to the foam layer, not only the polymeric antistatic agent is stretched when the foam is widened and drawn, but also when the foam is extruded from the die and foamed, the polymeric antistatic agent is stretched , It can be considered that the polymer antistatic agent forms a more complex network structure among the polyethylene-based resin. From this point of view, the upper limit of the blending amount of the polymer-type antistatic agent is preferably 12% by weight, more preferably 10% by weight. On the other hand, if the blending amount of the polymer-type antistatic agent is too small, there is a fear that sufficient antistatic performance can not be obtained. From this point of view, the lower limit of the blending amount of the polymeric antistatic agent is preferably 4% by weight.

Specific examples of the polymeric antistatic agent include a hydrophilic polymer having a volume resistivity of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω · cm (hereinafter simply referred to as a hydrophilic polymer), a block polymer of a hydrophilic polymer block and a hydrophobic polymer block , Ionomers, and the like. Examples of the hydrophilic polymer include polyether, cationic polymer, anionic polymer, and the like. The hydrophilic polymer block may be a block of the hydrophilic polymer, and the hydrophobic polymer block may be a polyolefin or a polyamide. Examples of the combination of the hydrophilic polymer block and the hydrophobic polymer block include ester bond, amide bond, ether bond and the like. Among these, a block copolymer having a polyether block and a polyolefin block as a hydrophobic polymer block is preferable in order to give an excellent antistatic effect and to suppress the deterioration of physical properties by adding an antistatic agent . In addition, since the amount of the polymeric antistatic agent to obtain the desired antistatic effect is minimized, the amount of migration of the organic material can be reduced, and therefore, the surface resistivity is preferably 1 x 10 ⁷ Ω or less.

The thickness of the surface layer is required to be 2 to 10 mu m. When the thickness is smaller than 2 占 퐉, the migration of the low molecular weight component derived from the polymeric antistatic agent contained in the foam layer can not be suppressed by the surface layer. When it is larger than 10 m, the distance between the surface of the foam layer containing the antistatic agent and the surface layer becomes large, and it becomes difficult to neutralize the charge generated on the surface layer surface, so that it is difficult to exhibit sufficient antistatic performance. The thickness of the surface layer can be adjusted by adjusting the discharge amount and the take-off speed.

The thickness of the foam sheet of the present invention is preferably not more than 10 mm, more preferably not more than 8 mm, since the foam sheet is easy to handle when the foam sheet is packed or wrapped More preferably 5 mm or less, and particularly preferably 2 mm or less. On the other hand, in the case where a multilayer foamed sheet is used in a particularly demanding buffering property, the thickness is preferably 0.05 mm or more, and more preferably 0.1 mm or more, from the viewpoint of obtaining sufficient buffering property.

The thickness of the surface layer and the thickness of the foamed sheet are measured as follows.

First, the foam sheet is cut along the width direction (direction orthogonal to the extrusion direction), and the cut surface is divided into 10 equal parts in the width direction. The widthwise center of each of the 10 portions of the cut surface is defined as the measurement point. 10 are photographed by a microscope, and the thicknesses of the surface layer and the foam sheet at the measurement points are measured on each image taken. The arithmetic mean value of ten measured surface layer thickness values obtained is taken as the thickness of the surface layer and the arithmetic mean value of the ten measured foam layer thickness values is taken as the thickness of the foam sheet. In addition, either one of the foam layer and the surface layer may be colored to facilitate measurement of the thickness of the surface layer.

The thickness [탆] of the surface layer is a value obtained by dividing the total amount X [kg / hour] of the surface layer, the width W [m] of the obtained foam sheet and the length per unit time When L [m / hr] is known, the density ρ [g / cm 3] of the polyethylene resin constituting the surface layer can be obtained by the following equation (1).

Thickness of surface layer [占 퐉] = [1000 占 X / (L 占 占 占〕)] (One)

The apparent density of the foam sheet of the present invention is preferably 15 to 300 kg / m 3. When the apparent density of the foam sheet is in the above range, the balance between the strength and the cushioning property is excellent. From this point of view, the apparent density is more preferably not less than 18 kg / m 3, more preferably not less than 20 kg / m 3, and more preferably not more than 300 kg / m 3 and not more than 250 kg / And even more preferably 200 kg / m 3 or less.

In the present invention, a method of measuring the apparent density of the foam sheet is as follows. First, the thickness of the foam sheet is measured by the above-described method. Next, in order to measure the basis weight, a test piece of (total width of the foam sheet) × (length in the extrusion direction of 10 cm) × (thickness of the multilayer foam sheet) is cut out from the foam sheet, and the mass [g] of the test piece is measured. The basis weight [g / m 2] is obtained by dividing the mass by the area of the test piece [m 2: total width (m) of the foam sheet x 0.1 m]. In addition, the apparent density [kg / m 3] of the foam sheet can be obtained by dividing the obtained basis weight [g / m 2] by the thickness [mm] of the foam sheet and converting it into units.

In the foam sheet of the present invention, the closed cell ratio thereof is preferably 10% or more, and more preferably 20% or more.

The closed cell ratio S (%) of the polyethylene-based resin foam sheet was measured in accordance with a procedure C described in ASTM D 2856-70, using a foam comparator 930 manufactured by Toshiba Beckman Co., Can be obtained by calculating from the following equation (2) from the actual volume (the sum of the volume of the independent bubble and the volume of the resin portion): Vx (L).

S (%) = (Vx - W /?) 100 / (Va - W /?) (2)

In the above formula (2), Va, W, and p are as follows.

Va: apparent volume (㎤) of the foam sheet used for the measurement

W: Mass (g) of the foam sheet in the test piece

ρ: density of the resin constituting the foam sheet (g / cm 3)

The foam sheet of the present invention has antistatic properties. Specifically, for use as an electronic device or a packaging material or a separator for the electronic device, the half-life period of the initial voltage at the surface layer side is preferably 60 seconds or less, and more preferably 30 seconds or less. The half-life is a value measured according to Method A (half-life method) of JIS L 1094-1988. Specifically, the state of the test piece is adjusted by leaving the test piece (40 mm long × 40 mm wide × thickness: thickness of the foaming sheet to be measured) cut from the foam sheet for 36 hours under an atmosphere of a temperature of 23 ° C. and a relative humidity of 50% . Next, in accordance with method A of JIS L 1094 (1988), the turntable was rotated at a rotational speed of 1300 rpm and applied for 30 seconds under (+) 10 kV or (-) 10 kV, Determine the half-life (in seconds) until the initial voltage drops to 1/2 after stopping. The initial electrification voltage is preferably within ± 2.0 kV, more preferably within ± 1.5 kV.

In the foamed sheet of the present invention, when a higher antistatic effect is required, the surface resistivity of the surface layer side is preferably less than 1 x 10 ¹⁴ Ω, more preferably 1 × 10 ⁸ to 1 × 10 ¹³ (Ω) Is more preferable. The surface resistivity of the foam sheet is a value measured in accordance with JIS K 6271 (2001). That is, the state of the test piece was adjusted by allowing the test piece (100 mm long × 100 mm wide × thickness: thickness of the foamed sheet) cut from the foam sheet to stand in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours, Under the condition of a voltage of 500 V, the voltage application to the surface layer side of the test piece is started and the surface resistivity after 1 minute is measured.

Next, preferred examples of the method for producing the polyethylene-based resin foam sheet of the present invention will be described.

The laminated foam sheet of the present invention is produced by coextruding a polyethylene-based resin surface layer on one side or both sides of a polyethylene-based resin foam layer containing a polymer-type antistatic agent. Specifically, using a device in which a co-extrusion die is mounted at the outlet of an extruder for forming a foam layer, and an extruder for forming a surface layer is connected to the die for co-extrusion, The melt and the second melt for surface layer formation are joined together and extruded and foamed to produce a foamed sheet.

First, an additive such as the polyethylene resin (A), a polymeric antistatic agent, and a foam modifier as required is fed to an extruder for forming a foam layer, heated and kneaded, and then the physical foaming agent is press- do.

On the other hand, the polyethylene-based resin (B) is supplied to an extruder for forming a surface layer and heated and kneaded to obtain a second melt.

Cooling the first melt to a temperature suitable for foaming and cooling the second melt as close as possible to the appropriate foaming temperature of the foam layer so as to introduce them into the co-extrusion die, A second melt is laminated on at least one side of the first melt, co-extrusion is performed to pull the first melt while foaming, and a surface layer is formed on the surface of the foam layer to obtain a foam sheet .

Methods for forming a foam sheet by a co-extrusion method include a method of pneumatic delivery using a flat die for co-extrusion and a co-extrusion using an annular die for co-extrusion to form a cylindrical foam , And then the foamed sheet is cut into a foamed sheet in the form of a sheet while taking out the foamed article along the circumferential widening device while drawing it out. Among these methods, a method using a ring-shaped die for co-extrusion is a preferable method because it suppresses the occurrence of a wave-like shape called a corrugation or the heat shrinkage ratio of the foam sheet can be controlled within a preferable range.

The extruder, the coextrusion annular die, the circumferential widening device, the device for cutting the ordinary foam, and the like can be used, which are conventionally known in the field of extrusion foaming.

Examples of physical foaming agents to be press-fit into the extruder include aliphatic hydrocarbons having 2 to 7 carbon atoms, halogenated aliphatic hydrocarbons having 1 to 3 carbon atoms, aliphatic alcohols having 1 to 4 carbon atoms, aliphatic ether having 2 to 8 carbon atoms, carbon dioxide , Or a combination of two or more thereof.

The physical foaming agent is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 30 parts by weight, per 100 parts by weight of the total of the resin constituting the foam layer of the polyethylene resin (A) and the polymeric antistatic agent, to be.

To the first melt for forming the foam layer, a foam adjuster is usually added. The bubble adjusting agent may be organic or inorganic. Examples of the inorganic bubble adjusting agent include metal borates such as zinc borate, magnesium borate and borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate and the like. Examples of the organic bubble adjusting agent include sodium phosphate, sodium 2,2-methylenebis (4,6-tert-butylphenyl), sodium benzoate, calcium benzoate, aluminum benzoate and sodium stearate.

Also, a combination of citric acid and sodium bicarbonate, a mono alkali salt of citric acid and sodium bicarbonate, or the like, may be used as a cell foam regulator. These foam modifiers may be used by mixing two or more kinds thereof.

It is preferable to add a volatile plasticizer to the second melt for surface layer formation. Even when the extrusion temperature of the second melt is brought close to the proper foaming temperature of the foam layer by co-extruding the second melt and the first melt by the addition of the volatile plasticizer, the melt elongation of the second melt at that temperature becomes remarkable , So that the elongation of the second melt can be followed by the elongation of the first melt.

The volatile plasticizer is volatilized or lost from the foam sheet after the foam sheet is produced. The volatile plasticizer can lower the melt viscosity of the polyethylene-based resin in the state in which it is present in the second melt and form a resin melt suitable for co-extrusion, and after the extrusion foaming, the volatile plasticizer is vaporized from the surface layer, Is easily lost and remains on the foam sheet, and is less likely to cause migration.

Examples of the volatile plasticizer include saturated aliphatic hydrocarbons having 2 to 7 carbon atoms, halogenated aliphatic hydrocarbons having 1 to 3 carbon atoms, aliphatic alcohols having 1 to 4 carbon atoms, aliphatic ethers having 2 to 8 carbon atoms, or the like, or 2 It is preferable to use a material composed of more than one species.

As examples of the volatile plasticizer, saturated hydrocarbons having 2 to 7 carbon atoms include ethane, propane, n-butane, isobutane, n-pentane, isopentane, isohexane, cyclohexane and heptane.

Examples of the halogenated aliphatic hydrocarbon having 1 to 3 carbon atoms include methyl chloride, ethyl chloride, 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane.

Examples of the aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol.

Examples of the aliphatic ether having 2 to 8 carbon atoms include methyl ether, ethyl ether, propyl ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, methyl isopropyl ether, methyl butyl ether and methyl isobutyl ether , Methyl amyl ether, methyl isoamyl ether, ethyl propyl ether, ethyl isopropyl ether, ethyl butyl ether, ethyl isobutyl ether, ethyl amyl ether, ethyl isoamyl 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 is preferably 80 占 폚 or lower, more preferably 60 占 폚 or lower, from the standpoint of volatilization from the surface layer. If the boiling point of the volatile plasticizer is within this range, the volatile plasticizer is naturally volatilized and removed naturally from the surface layer by heat after the co-extrusion or subsequent gas permeation at room temperature. The lower limit of the boiling point is generally -50 ° C.

The addition amount of the volatile plasticizer is preferably 0.1 to 100 parts by weight, more preferably 1 to 50 parts by weight, based on 100 parts by weight of the polyethylene-based resin (B).

The polyethylene-based resin foam sheet of the present invention has antistatic properties and is suppressed to a small amount of migration of organic substances to the package. Therefore, the polyethylene-based resin foam sheet is preferably used as an electronic device such as a glass plate for a liquid crystal panel, You can.

Example

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

The polyethylene-based resin, the foam modifier, and the evaluation method used in the examples will be described below.

(1) Polyethylene resin

(LDPE1, density 922 kg / m 3, MFR 1.9 g / 10 min, melting point 111 캜, heptane extraction amount 1.15% by weight) manufactured by Dow Chemical Japan Co.,

(Ii) "Low density polyethylene: trade name 10S54A" (abbreviation LDPE2, density 925 kg / m 3, MFR 1.8 g / 10 min, melting point 111 캜, heptane extraction amount 0.15% by weight)

(Density: 961 kg / m 3, MFR 8.0 g / 10 min, melting point: 134 캜, heptane extraction amount: 0.2 wt%) manufactured by Toso Co.,

(Iv) LDPE1 was immersed in n-heptane at 50 占 폚 for 48 hours to obtain low molecular weight components (abbreviated as LDPE3, density 922 kg / m3, MFR 1.7 g / 10 min, melting point 111 캜, )

The heptane extraction amount of the polyethylene-based resin was determined by the above-described method. The heptane extraction amount of the mixed resin in Table 1 is the n-heptane extraction amount of the mixed resin kneaded at 200 캜 by the extruder.

(2) Polymer type antistatic agent

Polyester-polyolefin block copolymer: Pelektron HS (melting point: 134 占 폚, surface resistivity: 2.0 占⁰⁶ ?) (Abbreviation: PAA1) manufactured by Sanyo Chemical Industries,

(Ii) Polymer type antistatic agent VL300

Trade name: Pelestat VL300 " (melting point 133 캜, surface resistivity 1.2 x 10 ⁸ Ω) (abbreviation PAA2) manufactured by Sanyo Chemical Industries, Ltd., polyether-polyolefin block copolymer

(3) Foam adjusting agent

Manufactured by Matsumura Industry Co., Ltd. " Taluk: Product Name HiPiller # 12 "

[Device]

A tandem extruder in which a first extruder having a diameter of 90 mm and a second extruder having a diameter of 120 mm were connected in series was used as the extruder for forming the foam layer and a third extruder having a diameter of 50 mm was used as the extruder for forming the surface layer , And the outlet of the second extruder and the outlet of the third extruder were connected to the annular die for co-extrusion. The annular die for co-extrusion has a structure in which a second melt for surface layer formation, which will be described later, is laminated on both surfaces of a first melt for forming a foamed layer, and the diameter of the lip at the die outlet is 94 mm. In Example 5, a die having an outlet lip diameter of 70 mm was used.

Example 1

The polymeric antistatic agent shown in Table 1 was added to the polyethylene-based resin (A) shown in Table 1 in an amount shown in Table 1, and 1 part by weight of talc (trade name " High filler # 12 " manufactured by Matsumura Industrial Co., The raw material mixture was supplied to the raw material inlet of the first extruder and heated and kneaded to obtain a molten resin mixture adjusted to about 200 DEG C. Mixed butane in an amount shown in Table 1 as a physical foaming agent (n-butane / Isobutane = 70% by weight / 30% by weight) was fed to a second extruder connected to the downstream side of the first extruder to obtain a first melt for forming a polyethylene resin foam layer having a resin temperature shown in Table 2 .

At the same time, the polyethylene resin (B) shown in Table 1 was fed to a raw material inlet of a third extruder and heated and melted to prepare a molten resin mixture adjusted to about 200 캜. As the volatile plasticizer, (Normal butane / isobutane = 70% by weight / 30% by weight) was pressed, and then the resin temperature was adjusted to the resin temperature shown in Table 1 to obtain a second melt for forming a polyethylene-based resin surface layer.

Each of the first and second melts was introduced into a annular die for co-extrusion using the discharge amount shown in Table 1, and the second melt was laminated on both sides of the first melt and coaxially extruded from the annular die, Layer foamed body having a surface layer laminated thereon. The extruded normal laminated foam was widened by a normal widening apparatus having a diameter of 350 mm and the pulling speed was adjusted so that the total basis weight shown in Table 3 was obtained to obtain a polyethylene resin multilayer foamed sheet.

Example 2

A polyethylene-based resin multilayer foamed sheet was obtained in the same manner as in Example 1 except that the polyethylene-based resin for forming the foamed layer and the surface layer used were those shown in Table 1.

Example 3

A polyethylene-based resin multilayer foamed sheet was obtained in the same manner as in Example 1 except that the polyethylene-based resin for forming the foamed layer and the surface layer used were those shown in Table 1.

Example 4

A polyethylene-based resin multilayer foamed sheet was obtained in the same manner as in Example 1 except that the discharge amount was changed as shown in Table 1 to the thickness of the surface layer shown in Table 4.

Example 5

Extruded annular die having a lip diameter of 70 mm was used and the raw materials shown in Table 1 were used as the polyethylene resin (A), and mixed butane as a foaming agent was both press-fed as shown in Table 1, And the mixed raw materials shown in Table 1 were used as the polyethylene-based resin (B), and the mixed butane as the volatile plasticizer was both press-injected as shown in Table 1 and adjusted to the resin temperature shown in Table 1, Extruding the molten resin for forming the surface layer in the discharge amount shown in Table 1 to form a generally laminated foam, and the laminated foam thereof was adjusted to a basis weight shown in Table 3 in accordance with a normal cooling device having a diameter of 212 mm In addition, a polyethylene-based resin multilayer foamed sheet was obtained in the same manner as in Example 1.

Comparative Example 1

A polyethylene resin single-layer foamed sheet composed of only a foam layer containing a polymer-type antistatic agent was obtained in the same manner as in Example 1, except that the surface layer was not laminated.

The obtained single-layer foamed sheet had a high antistatic property, but had no surface layer, and thus had a large amount of migration of a low-molecular-weight component derived from a polymeric antistatic agent into the package.

Comparative Example 2

Except that the surface layer thickness was changed to the thickness shown in Table 4 and the discharge amount and the withdrawing speed of the molten resin for forming the foam layer and the molten resin for forming the surface layer were adjusted so as to have the total basis weight shown in Table 4, Thereby obtaining a resin multilayer foamed sheet.

The obtained multilayer foamed sheet had a large amount of migration of low-molecular-weight components derived from the polymeric antistatic agent into the article to be packaged because the thickness of the surface layer was too thin.

Comparative Example 3

A polyethylene-based resin multilayer foamed sheet was obtained in the same manner as in Example 1 except that the polymeric antistatic agent of the amount shown in Table 2 was blended.

The obtained multilayer foamed sheet had a low antistatic property because the amount of the antistatic agent contained was too small.

Comparative Example 4

A polyethylene-based resin multilayer foamed sheet was obtained in the same manner as in Example 1, except that the foamable layer-forming resin was blended with the polymeric antistatic agent shown in Table 2.

The multilayer foamed sheet thus obtained had a large amount of the antistatic agent incorporated therein, and therefore the amount of low-molecular-weight components to be transferred was large.

Comparative Example 5

Polyethylene resin multilayer foamed sheets were obtained in the same manner as in Example 1 except that a resin having a large heptane extraction amount shown in Table 2 was used as the polyethylene resin (A) and the polyethylene resin (B).

The resultant multilayer foamed sheet had a large amount of migration of low molecular weight components derived from the polyethylene-based resin into the article to be wrapped.

Comparative Example 6

Polyethylene resin multilayer foamed sheets were obtained in the same manner as in Example 1, except that a resin having a large heptane extraction amount shown in Table 2 was used as the polyethylene resin (A).

The resultant multilayer foamed sheet had a large amount of migration of low molecular weight components derived from the polyethylene-based resin into the article to be wrapped.

Comparative Example 7

A resin having a high heptane extraction amount as shown in Table 2 was used as the polyethylene resin (A) in the foamed layer, and the resin shown in Table 2 was used as the polyethylene resin (B) in the surface layer without blending the polymer type antistatic agent , A polyethylene-based resin multilayer foamed sheet was obtained in the same manner as in Example 1, except that the polymer type antistatic agent of the kind and the compounding amount shown in Table 2 was blended.

The resultant multilayer foamed sheet was excellent in antistatic property but had a large amount of migration of the low molecular weight component into the package.

Comparative Example 8

A polyethylene-based resin multilayer foamed sheet was obtained in the same manner as in Example 1 except that a polymer-type antistatic agent was not added to the foamed layer, and a polymeric type antistatic agent of the kind and amount shown in Table 2 was added to the surface layer.

The resultant multilayer foamed sheet was excellent in antistatic property but had a large amount of migration of a low molecular weight component derived from a polymeric antistatic agent into a package.

Table 1 shows the production conditions of the examples, and Table 2 shows the production conditions of the comparative examples. The physical properties of the foam sheet obtained in the examples are shown in Table 3, and the physical properties of the foam sheet obtained in the comparative examples are shown in Table 4.

Various physical properties measurement and evaluation in Tables 3 and 4 were carried out as follows.

(1) The apparent density, basis weight, total thickness, and thickness of the surface layer were measured as described above.

(3) Initial voltage and half-life

The initial electrification voltage was measured by cutting five sheets at random from the foam sheet at a size of 45 mm × 45 mm (thickness of the foam sheet), and using these as the test pieces, adjusting the state at 23 ° C. and 50% RH for 24 hours The turntable was rotated at a rotational speed of 1300 rpm in accordance with JIS L 1094 (1988) A method under an environment of 23 ° C and 50% RH using a static Ernest meter (manufactured by Shishido Electric Co., Ltd.) (-) 10 kV for 30 seconds, and the initial voltage was measured when the application was stopped. Subsequently, the time (half-life period) until the half of the initial voltage was measured. These measurements were performed on both sides of each test piece (10 times in total), and the respective measured values were averaged to obtain the initial voltage and half-life.

(4) Surface resistivity

A test piece (100 mm in length × 100 mm in width × thickness: foam sheet thickness) cut out randomly from three sheets of foam sheet was sampled. The surface resistance value after one minute after applying with an applied voltage of 500 V according to JIS K 6271 (2001) was adopted. The measurement was carried out on both surfaces of the test piece (six times in total), and the surface resistivity was determined from the average value of the obtained measurement values. "TR8601" manufactured by Takeda Riken Kogyo Co., Ltd. was used as the measuring device. The surface resistivity of the polymeric antistatic agent is a value measured by using an antistatic agent heat-pressed at 200 캜 at 0.1 mm as a test piece.

(5) Performance evaluation

The contact angle of the pre-clean slide glass manufactured by Matsunami Glass Industries Co., Ltd. was evaluated in advance based on the static method described in JIS-R 3257-1999 using the contact angle DM500R manufactured by Kyowa Interface Science Co., A sample (a foam sheet obtained in Example and Comparative Example) to be evaluated on the slide glass was kept still at 60 캜 for 24 hours while being closely contacted at a pressure of 3.8 g / cm 2. Thereafter, the sample was removed from the glass, and the contact angle was again measured with respect to the surface on which the sample was contacted. The difference between the contact angles before and after the test was 10 (or less), and the difference was 10 (or less).

Claims (4)

A polyethylene resin multilayer foamed sheet obtained by co-extruding a first melt for forming a foamed layer and a second melt for forming a surface layer, having a foam layer and a superficial layer laminated on at least one surface of the foam layer, wherein
The first melt is composed of a polyethylene resin (A), a polymeric antistatic agent and a physical foaming agent,
Wherein the second melt is composed of a polyethylene-based resin (B)
Each of the polyethylene-based resin (A) and the polyethylene-based resin (B) has an n-heptane extraction amount of 0.5 wt% or less at 50 캜,
The polymeric antistatic agent is present in the foam layer in an amount of 3 to 15% by weight based on the total of 100% by weight of the polyethylene-based resin (A) and the polymeric antistatic agent,
Wherein the surface layer has a thickness of 2 to 10 占 퐉. The method according to claim 1,
Wherein the surface layer has a surface resistivity of less than 1 x 10 < ¹⁴ > OMEGA. 3. The method according to claim 1 or 2,
Wherein the polyethylene based multilayer foamed sheet has an apparent density of 15 to 300 kg / m < 3 >. A sheet for glass plate comprising the polyethylene-based resin multilayer foamed sheet according to any one of claims 1 to 3.