TWI683848B - Polyethylene based resin foamed sheet - Google Patents

Abstract

Provided is a polyethylene resin foam sheet exhibiting an excellent antistatic performance and having a small thickness by including a polyethylene component having a specific melting point and an antistatic component.

Description

Polyethylene resin foam sheet

The present invention relates to a polyethylene resin foamed sheet.

Conventionally, flat panel displays such as liquid crystal displays and plasma displays have been manufactured using glass substrates having transparent electrodes formed on their surfaces.

This glass substrate is usually not stored separately during the manufacturing process of a flat panel display or the like, but is stored in a state of a laminate in which a plurality of glass substrates in a horizontal posture are stacked.

At this time, if the glass substrate is directly laminated, the transparent electrode may be injured. Therefore, in the past, sheets called "backing paper" and the like were interposed between glass substrates and used as cushioning materials.

Because of its softness and excellent cushioning properties, such a cushioning material sheet uses a resin foam sheet (see Patent Document 1 below).

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2005-329999

Regarding the resin foam sheet used in the above-mentioned applications, it is considered to use a polyethylene-based resin foam sheet that is relatively excellent in softness.

When the glass substrate is coated with such a resin foam sheet, when the resin foam sheet is removed, static electricity may be generated.

A glass substrate that generates static electricity may adhere to foreign objects.

In this way, the resin foam sheet needs antistatic properties.

Therefore, in the past, it has been continually studied to include a polymer antistatic agent that can continuously exhibit antistatic properties for a long period of time.

However, in the past, as long as the polyethylene-based resin foamed sheet contained a relatively large amount of polymer-type antistatic agent, there was a problem that it was difficult to exert sufficient antistatic properties.

In addition, the general polymer type antistatic agent is composed of a polymer having a high-polarity portion with a low affinity for the polyethylene-based resin in the molecular structure as a main component, and does not show sufficiently high affinity for the polyethylene-based resin as a whole Sex.

Therefore, the polymer antistatic agent has a problem that it is difficult to exhibit good dispersibility in the polyethylene resin foamed sheet.

If the polymer type antistatic agent is not sufficiently dispersed and exists in the shape of agglomerates in the polyethylene resin foam sheet, it is difficult to exert the antistatic effect.

In addition, if the polyethylene resin foamed sheet has agglomerates of a polymer-type antistatic agent, it may not exert sufficient mechanical strength.

Having said that, when storing the glass substrate in the form of a laminate, it is generally required to reduce the height of the laminate.

However, the effect of the coagulum on the strength of the sheet will decrease as the polyethylene The thickness of the resin foam sheet becomes significant.

Therefore, in order to obtain a polyethylene resin foamed sheet excellent in antistatic properties and thin in thickness, problems such as sheet cracking are likely to occur during the sheet manufacturing stage.

Therefore, in the past, it has been difficult to obtain a polyethylene-based resin foamed sheet excellent in antistatic properties and thin in thickness.

In addition, the need to obtain a thin polyethylene resin foam sheet with excellent antistatic properties and a thin thickness is not limited to the case of being interposed between glass substrates, but all of the polyethylene resin foam sheets are commonly required. Matters.

The present invention is to meet such a demand, and to provide a polyethylene-based resin foam sheet excellent in antistatic properties and thin in thickness.

The inventors conducted intensive investigations to solve the above-mentioned problems, and found that it is possible to set the melting point of the polyethylene-based resin contained in the polyethylene-based resin foam sheet and the polymer antistatic agent to a predetermined relationship. During its manufacture, the dispersibility of the polymer antistatic agent in the polyethylene resin foamed sheet is improved.

Therefore, the present inventors found that by improving the dispersibility of a polymer-type antistatic agent, it is possible to make a polyethylene-based resin foam sheet excellent in antistatic properties and thin in thickness easy to manufacture, and completed the present invention.

That is, in order to solve the above-mentioned problems, the present invention provides a polyethylene-based resin foamed sheet containing a polyethylene component composed of one or more types of polyethylene-based resins, and one or more types of polyethylene components The antistatic agent component composed of the polymer antistatic agent, wherein the DSC curve of the polyethylene component and the DSC curve of the antistatic agent component One or more endothermic peaks are shown, and the peak temperature of the endothermic peak appearing on the highest temperature side in the DSC curve of the polyethylene component is set to Tm1, while the DSC curve of the antistatic agent component is on the highest temperature side. When the peak temperature of the developed endothermic peak is Tm2, the following relational expression (1) is satisfied.

(Tm1-10)≦Tm2≦(Tm1+17). . . (1)

According to the present invention, it is possible to provide a polyethylene-based resin foamed sheet excellent in antistatic properties and thin in thickness.

1‧‧‧polyethylene resin foam sheet

2‧‧‧Glass substrate

10‧‧‧Layered body

Fig. 1 is a schematic view showing a usage form of a polyethylene resin foamed sheet.

Fig. 2 is a schematic diagram showing a method of measuring the "sag amount" of the foamed polyethylene resin sheet.

Hereinafter, an embodiment of the polyethylene resin foamed sheet of the present invention will be described.

The polyethylene resin foamed sheet of this embodiment is used as a buffer material for a glass substrate for flat panel displays.

The polyethylene resin foam sheet is used to contact the surface of the glass substrate.

As shown in FIG. 1, the polyethylene resin foamed sheet 1 of the present embodiment is used to interleave adjacent layers when the laminated body 10 is formed by stacking a plurality of glass substrates 2 in a horizontal posture in a vertical direction, for example. Between the glass substrate 2 By.

The thicker one of the polyethylene resin foamed sheets 1 can more reliably prevent contact between the glass substrates 2.

In addition, the polyethylene resin foamed sheet 1 having a large mass per unit area can exhibit excellent compressive strength and more reliably prevent contact between the glass substrates 2.

On the other hand, if the thickness of the polyethylene resin foamed sheet 1 is thin, the laminate 1 can be simplified.

Therefore, those having a small mass per unit area in the polyethylene-based resin foamed sheet 1 are easy to form those with a thin thickness and excellent cushioning properties.

From such viewpoints, the polyethylene resin foamed sheet 1 of the present embodiment preferably has a thickness of 0.15 mm or more and 0.4 mm or less.

Then, the polyethylene resin foamed sheet 1 of the present embodiment preferably has a mass per unit area of 15 g/m ² or more and 30 g/m ² or less.

In addition, it is preferable that the polyethylene-based resin foamed sheet 1 is appropriately compressed to exhibit cushioning properties when the laminate is subjected to pressure from the weight of the glass substrate 2 and to ensure a certain thickness or more.

From such a viewpoint, the polyethylene-based resin foamed sheet 1 preferably has a thickness of 45% or more and 70% or less before compression when compressed in the thickness direction with a pressure of ² N/cm ² .

Furthermore, the polyethylene resin foamed sheet 1 preferably has a thickness of 0.1 mm or more when compressed in the thickness direction with a pressure of ² N/cm ² .

Polyethylene resin foam sheet 1, preferably from glass base When the surface of the board 2 is removed, no static electricity is generated.

More specifically, the polyethylene-based resin foamed sheet 1 preferably has a surface resistivity of 1×10 ⁸ Ω or more and 1×10 ¹² Ω or less.

In addition, the thickness and surface resistivity of the polyethylene-based resin foamed sheet 1 of the present embodiment mean values obtained by the method described in the examples.

In order to exert the above-mentioned characteristics, the polyethylene resin foamed sheet 1 of the present embodiment contains: a polyethylene component composed of one or more polyethylene resins, and one or more polymers Antistatic agent component composed of type antistatic agent.

The polyethylene component and the antistatic agent component of the polyethylene-based resin foamed sheet 1 exhibit a predetermined DSC curve when subjected to differential scanning calorimetry (DSC).

Specifically, in the polyethylene resin foamed sheet 1 of the present embodiment, the DSC curve of the polyethylene component and the DSC curve of the antistatic agent component show one or more endothermic peaks.

Furthermore, in the polyethylene resin foamed sheet 1 of the present embodiment, the peak temperature of the endothermic peak shown at the highest temperature in the DSC curve of the polyethylene component is set to Tm1, and the highest temperature in the DSC curve of the antistatic agent component When the peak temperature of the displayed endothermic peak is Tm2, the following relational expression (1) is satisfied.

(Tm1-10)≦Tm2≦(Tm1+17). . . (1)

As described later, the polyethylene resin foamed sheet 1 is preferably obtained by combining the polyethylene component and the antistatic agent component with appropriate The foaming agent is formed by extruding and foaming together.

Since the melting point (endothermic peak) of the polyethylene component and the melting point (endothermic peak) of the antistatic agent component in the polyethylene-based resin foamed sheet 1 will have similar values as described above, when the foam is extruded, the antistatic agent The component will show good dispersibility with respect to the polyethylene component.

That is, in this embodiment, it is difficult to form agglomerates of antistatic agent components in the polyethylene resin foam sheet 1.

Therefore, the polyethylene resin foamed sheet 1 of the present embodiment has a high antistatic effect on the content of the antistatic agent component.

Furthermore, the polyethylene resin foamed sheet 1 of the present embodiment is easy to manufacture even if it is a thin sheet.

In order to exert such effects more conspicuously, the polyethylene resin foamed sheet 1 of the present embodiment is preferably such that the DSC curve of the antistatic agent component shows an endothermic peak of 2 or more, and the DSC curve is shown at the highest temperature The heat of fusion of the endothermic peak is below 30J/g.

That is, in the polyethylene resin foamed sheet 1 of the present embodiment, it is preferable that the antistatic agent component not only needs to approximate the polyethylene component to the melting temperature range, but the antistatic agent component needs to be rapidly melted.

By the rapid melting of the antistatic agent component, the polyethylene-based resin foamed sheet 1 of this embodiment can more reliably exert the effect of suppressing the formation of agglomerates.

In order to exert such an effect more conspicuously, the polyethylene resin foamed sheet 1 of the present embodiment is preferably such that the DSC curve of the antistatic agent component shows an endothermic peak of 2 or more, and the DSC curve is the most The difference between the peak temperature of the endothermic peak displayed at a high temperature and the peak temperature of the endothermic peak displayed at the lowest temperature in the aforementioned DSC curve is 95° C. or less.

As described above, in this embodiment, the peak temperature of the endothermic peak displayed at the highest temperature in the DSC curve of the antistatic agent component will show the peak of the endothermic peak displayed at the highest temperature in the DSC curve of the polyethylene component The value of temperature.

The difference between the peak temperature of the endothermic peak shown at the lowest temperature and the peak temperature of the endothermic peak shown at the highest temperature in the DSC curve of the so-called antistatic agent component is a certain value or less, which means that the polyethylene-based resin will be formed. When the resin composition of the foam sheet is heated, the time when the entire antistatic agent component melts is close to the time when the polyethylene component melts.

That is, the difference between the peak temperature of the endothermic peak displayed at the highest temperature and the peak temperature of the endothermic peak displayed at the lowest temperature in the DSC curve of the antistatic agent component becomes a predetermined value or less, which can cause the polyethylene resin to develop The dispersibility of the foam sheet becomes even better.

In addition, the antistatic agent component is preferably composed of a plurality of polymer antistatic agents containing a first polymer type antistatic agent and a second polymer type antistatic agent.

By using two or more types of polymer antistatic agents with different melting points, the endothermic peak displayed at the highest temperature in the DSC curve of the antistatic agent component measured by differential scanning calorimetry (DSC) can be Broadband.

That is, the antistatic agent component contains two or more types of polymer antistatic agents with different melting points, and the melting behavior is not the rapid rise and fall, but the Gentler. The antistatic agent component exhibiting a gentle melting behavior is further advantageous for the dispersion of the polyethylene component.

In addition, it is preferable that one of the first polymer-type antistatic agent and the second polymer-type antistatic agent (for example, the first polymer-type antistatic agent) and the melting point of the polyethylene component be close to each other, and the other In the case of (eg, the second polymer antistatic agent), the melting point is preferably higher than the former.

In the following, taking the case where the melting point of the second polymer type antistatic agent is higher than that of the first polymer type antistatic agent as an example, the polyethylene-based resin foamed sheet of this embodiment will be described.

In addition, the melting point and the heat of fusion of the polyethylene component, the antistatic agent component, the first polymer type antistatic agent, the second polymer type antistatic agent, and the like in the present embodiment mean those described in the examples The value measured by the method.

Examples of the polyethylene resin as the main component of the polyethylene resin foamed sheet of the present embodiment include ultra-low density polyethylene resin (VLDPE), low density polyethylene resin (LDPE), and linear low density polyethylene resin. (LLDPE), medium density polyethylene resin (MDPE), high density polyethylene resin (HDPE) and other polyethylene resins.

The melt flow rate (MFR) of the polyethylene component of the present embodiment composed of one or more of these polyethylene-based resins is preferably 1.0 g/10 min or more and 7.0 g/10 min or less.

In addition, the melt tension of the polyethylene component is preferably 6 cN or less.

In addition, the lower limit of the melt tension of the polyethylene component is usually 0.5 cN.

The values of the MFR and melt tension of the polyethylene resin foamed sheet in this embodiment mean that they are measured by the method described in the examples Value.

On the other hand, examples of the polymer antistatic agent include plasma polymerization of polyethylene oxide, polypropylene oxide, polyethylene glycol, polyester amide, polyether ester amide, and ethylene-methacrylic acid copolymer. Substances, quaternary ammonium salts such as polyethylene glycol methacrylate copolymers, and copolymers of olefin-based blocks and hydrophilic blocks described in Japanese Patent Application Laid-Open No. 2001-278985.

The polymer antistatic agent contained in the polyethylene-based resin foamed sheet is preferably a copolymer of an olefin-based block and a hydrophilic block.

The polyolefin resin composition forming the polyethylene resin foamed sheet preferably contains a polyether-polyolefin block copolymer (a block copolymer of a polyether block and a polyolefin block) as the aforementioned high Molecular antistatic agent.

In addition, for the purpose of further improving the antistatic performance, the polymer type antistatic agent may be one in which the polyamide is mixed with the aforementioned block copolymer.

In addition, the polymer type antistatic agent may be a copolymer including a polyether block, a polyolefin block, and a polyamide block.

The polymer antistatic agent is more preferably a copolymer of an olefin block and a polyether block, and the main component is a copolymer having a propylene ratio of 70 mol% or more in the olefin block. By.

In addition, the ratio of the polyether-polyolefin block copolymer in the polymer antistatic agent is preferably 70% by mass or more, and more preferably 80% by mass or more.

The aforementioned polyethylene resin foamed sheet is made of antistatic agent Those with more content are helpful to exert excellent antistatic performance.

On the other hand, the polyethylene resin foamed sheet with less antistatic agent component helps prevent the formation of agglomerates caused by the antistatic agent component.

From such a viewpoint, the content of the antistatic agent component of the polyethylene resin foamed sheet is preferably 3 parts by mass or more and 15 parts by mass or less when the content of the polyethylene component is 100 parts by mass.

In addition to the polyethylene component and the antistatic agent component, the polyethylene-based resin foamed sheet of the present embodiment may contain a bubble adjuster and various additives.

Examples of the bubble adjuster include inorganic particles and organic particles. The inorganic particles include talc, mica, silica, diatomaceous earth, alumina, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, and hydroacidification. Particles of any one of calcium, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, barium sulfate, and glass.

Examples of the organic particles include particles such as polytetrafluoroethylene.

In addition, in this embodiment, it can be applied as a chemical foaming agent such as azodimethanamide, sodium bicarbonate, a mixture of sodium bicarbonate and citric acid, etc., and it can also be used as the aforementioned bubble regulator.

The polyethylene resin foamed sheet of the present embodiment may contain a small amount of polyolefin resin other than polyethylene resin such as polypropylene resin as other components.

The polyethylene-based resin foamed sheet of the present embodiment may contain a small amount of resin other than polyolefin-based resin as other components.

In addition, the polyethylene resin foamed sheet of this embodiment may contain Anti-aging agents, antioxidants, ultraviolet absorbers, surfactants, flame retardants, antibacterial agents, colorants, etc. are other ingredients.

However, the content of the "other components" in the polyethylene resin foamed sheet as described above is preferably controlled to 5% by mass or less, and more preferably 3% by mass or less.

The ultra good system is in a state in which it does not substantially contain other components (for example, the content in the polyethylene resin foamed sheet is less than 1% by mass).

The polyethylene resin foamed sheet of this embodiment can be extruded by passing the resin composition containing the above-mentioned polyethylene resin, polymer type antistatic agent, bubble regulator, and foaming agent through a round die, etc. Produced by a foaming method.

The aforementioned foaming agent may include the aforementioned chemical foaming agent or physical foaming agent.

Examples of the physical blowing agent include hydrocarbons such as isobutane, n-butane, propane, pentane, hexane, cyclobutane, and cyclopentane, and inorganic gases such as carbon dioxide and nitrogen.

If you want to obtain a thin polyethylene resin foamed sheet in such extrusion foaming, if the polymer antistatic agent is not sufficiently diffused in the extruder and forms agglomerates, I am afraid that the extruded sheet will cause The rupture caused by the clot.

In contrast, the polyethylene resin foamed sheet of the present embodiment is mainly composed of a polyethylene component close to the melting point and an antistatic agent component. Since the antistatic agent component exhibits excellent dispersibility in the extruder, it is difficult Cracked.

In addition, by this, the polyethylene resin foamed sheet of this embodiment can increase the line speed at the time of manufacturing at a high speed.

For example, when manufacturing the polyethylene resin foamed sheet of the present embodiment, the sheet after extrusion may be wound at a high speed of 30 m/min to 100 m/min.

That is, from the viewpoint of production efficiency, the polyethylene resin foamed sheet of this embodiment also has advantages.

Moreover, even when the expanded diameter of the cylindrical foamed sheet extruded from the circular die is expanded, the polyethylene-based resin foamed sheet of the present embodiment is hard to crack, and the diameter of the circular die (connected to the slit width) The diameter of the center circle is 2.5 times or more and 5.0 times or less.

That is, the polyethylene-based resin foamed sheet of the present embodiment has an advantage that it is easy to obtain a thin product while the extruder is operating at high discharge.

In addition, since the polyethylene resin foamed sheet of the present embodiment has excellent dispersibility of the antistatic agent component, it can exhibit excellent antistatic performance without excessively formulating the antistatic agent component.

In this way, the polyethylene-based resin foamed sheet of the present embodiment not only has excellent antistatic properties but is easy to manufacture in a thin state, and has the advantage of easily producing excellent quality products with good yield.

In addition, as shown in FIG. 1, the polyethylene-based resin foamed sheet of the present embodiment can also be used in a form other than sandwiched between two glass substrates.

Then, the above list is only a limited illustration of the present invention, and the present invention is not to be interpreted in any way by the above list.

(Example)

The following examples are given to illustrate the present invention in more detail, but The present invention is not limited by these.

(Example 1)

Preparations prepared by mixing the following materials in the following ratios are prepared.

‧100 parts by mass of low-density polyethylene resin (trade name: "LF580", density: 931 kg/m ³ , melting point 115°C, MFR = 3.8 g/10 min, melt tension = 1.7 cN) manufactured by Japan Polyethylene Corporation

‧The first polymer antistatic agent (polyether-polyolefin block copolymer, trade name "Pelectron LMP", manufactured by Sanyo Chemical Industry Co., Ltd., crystallization temperature: 56°C, melting point: 115°C, heat of fusion: 26mJ/ mg, MFR=30g/10min) 3 parts by mass

‧Second polymer antistatic agent (polyether-polyolefin block copolymer, trade name: "Pelestat 300", crystallization temperature: 99°C, melting point: 135°C, MFR=30g/ 10min) 3 parts by mass

‧Mixture of bubble adjuster masterbatch (masterbatch containing azodimethamide: trade name "Serumaiku MB1023") made by Sankyo Chemical Co., Ltd. 0.15 parts by mass

The above formulation was supplied to the first extruder (cylinder diameter: φ 90 mm) of the tandem extruder, and melt-kneading was carried out so that the maximum temperature reached in the extruder became 210°C.

In addition, the first polymer type antistatic agent (trade name "Pelectron LMP", melting point: 106°C) and the second polymer type antistatic agent (trade name "Pelestat 300") are contained in a ratio of 1:1 in the manner described above , Melting point: 135°C) The melting point of the antistatic agent component is 130°C, and the difference between the melting point of the polyethylene component (115°C) is 15°C.

Melt and mix the above formulation with the first extruder During the course of the first extruder, mixed butane (isobutane/n-butane=50/) was pressed at a ratio of 18 parts by mass relative to 100 parts by mass of the low-density polyethylene resin. 50 (molby)) as a foaming agent, and then melt-kneading.

After being melt-kneaded by the first extruder, the melt-kneaded material is cooled to a temperature range suitable for foaming in a second extruder (cylinder diameter: φ 150 mm) connected to the first extruder (111 ℃), from the circular die with an outlet diameter of 222mm (slit width 0.04mm) to the atmosphere to extrusion foam.

The resin temperature at this time was 116°C.

After blowing and cooling the extruded foamed cylindrical foamed sheet, the cylindrical foamed sheet was cooled along a cooling mandrel with a diameter of 770 mm and a length of 650 mm while expanding the diameter.

Next, the expanded cylindrical foam sheet was wound at a winding speed of 50 m/min, and the sheet was cut along the extrusion direction from one point in the circumferential direction.

The cut cylindrical foam sheet was peeled off to obtain a long strip-shaped polyethylene resin foam sheet, which was used as the polyethylene resin foam sheet of Example 1.

In addition, the physical properties etc. of the polyethylene resin foamed sheet of Example 1 were measured based on the following method.

<Thickness 1 (original thickness)>

The thickness of the polyethylene resin foamed sheet can be measured using a constant pressure thickness measuring machine (manufactured by Teclock, model "SCM-627").

Specifically, the thickness of the polyethylene resin foamed sheet can be determined as follows: a cylindrical weight is used to measure the thickness at a constant pressure on a circular surface (area: 60.8 cm ² ) with a radius of 4.4 cm The thickness of the polyethylene-based resin foamed sheet when a load of 95 g (including its own weight) is applied is measured by a machine.

In addition, the thickness of the polyethylene resin foamed sheet is usually measured at 50 points every 5 cm in the width direction as the arithmetic average of the measured values.

In addition, when the width of the polyethylene resin foam sheet is too narrow to ensure a measurement position of 50 points, the arithmetic average value of all the measured values is regarded as the thickness after ensuring as many measurement points as possible.

<Thickness 2 (compressed thickness)>

A measurement sample of 10 cm×10 cm×thickness (total thickness of the polyethylene-based resin foamed sheet) was cut out from the polyethylene-based resin foamed sheet, and a constant pressure thickness gauge (product name “PG-14J”) manufactured by Teclock was used. Terminal diameter: 16 mm), and the thickness of the measurement sample when a weight of 0.41 kg is placed is Tp.

In addition, the aforementioned measurement samples cut at 5 points in the sheet width direction of the polyethylene-based resin foamed sheet were measured, and the average value of the measured values measured for each measurement sample system was defined as the thickness at compression (Tp).

In addition, let the aforementioned original thickness be T0, and calculate the crushing rate (Pr) according to the following formula.

Pr=(T0-Tp)/T0×100

<Mass per unit area (basis weight)>

Two lines of the first line extending in the direction from the vertical extrusion direction and the second line parallel to the first line and spaced a distance of 20 cm from the first line in the extrusion direction are used to foam the polyethylene resin The sheet was cut to obtain a sample for measurement.

The mass per unit area of the polyethylene-based resin foamed sheet can be calculated using the following formula based on the mass of the sample for measurement: W (g) and the area: S (cm ² ).

In addition, when the size of the polyethylene resin foam sheet does not reach the available width of 20 cm to cut the measurement sample, it can be cut into a rectangular shape within the largest possible size to obtain a slice, according to the quality of the slice W(g) and For the area S (cm ² ), the mass per unit area of the polyethylene-based resin foamed sheet was obtained using the following formula.

Mass per unit area (g/m ² )=W/S×10000

<surface resistivity>

The surface resistivity of the polyethylene resin foamed sheet can be measured according to the method described in JIS K6911-2006 "General Test Methods for Thermosetting Plastics".

That is, the surface resistivity of the polyethylene resin foamed sheet can be tested using a test device (Advantest Digital Ultra-High Resistance/Micro-Current Meter R8340 and Resistivity Chamber (R12702A)) with a load of about 30N The electrode was pressed against the test piece, the resistance value after charging at 500 V for 1 minute was measured, and it was calculated according to the following formula.

In addition, a test piece can usually be produced by cutting out a polyethylene-based resin foamed sheet by "width 100 mm x length 100 mm x thickness (total thickness of the polyethylene-based resin foamed sheet)".

In addition, the measurement is usually performed by leaving the test piece for 24 hours or more in an environment with a temperature of 20±2°C and a humidity of 65±5%.

The test environment for measuring the surface resistivity is an environment with a temperature of 20±2°C and a humidity of 65±5%.

Secondly, the measurement usually sets the number of test pieces to 5, and performs the test on the front and back sides of the test pieces to obtain a total of 10 measured values.

In principle, the surface resistivity of the polyethylene resin foamed sheet uses the arithmetic average of all 10 measured values.

ρ s=π(D+d)/(D-d)×Rs

ρ s: surface inherent resistivity (Ω/□)

D: Inner diameter (cm) of the ring electrode on the surface (7cm in the resistivity test box R12702A)

d: Outer diameter (cm) of the inner circle of the surface electrode (5cm in the resistivity test box R12702A)

Rs: surface resistance (Ω)

<Continuous bubble rate (continuous bubble rate)>

A plurality of 25 mm square square slices were cut out from the polyethylene resin foamed sheet, and the slices were superimposed so as to have a thickness of about 5 cm to prepare a sample. Use Micromeritics dry automatic density meter (Shimadzu Corporation Co., Ltd., model: AccuPyc II 1340 (V1.0)) and the real volume (V) of the sample was measured.

In addition, the sample was stacked so that the slices did not produce gaps as much as possible to form a thickness of about 5 cm.

Then, the apparent volume (V0) is calculated from the outer shape of the sample.

From the obtained values (V, V0), the continuous bubble rate (%) was calculated according to the following formula.

Continuous bubble rate (%) = (V0-V)/V0×100

<melting point and heat of fusion>

The melting point of polyethylene-based resins and polymer-based antistatic agents is usually the peak of the DSC curve obtained after performing differential scanning calorimetry (DSC) analysis according to the method described in JIS K7121-2012 "Transition Temperature Measurement Method for Plastics"顶温度。 Top temperature.

In addition, the heat of fusion of the polyethylene-based resin and the polymer-based antistatic agent can be obtained from the peak area of the DSC curve according to the method described in JIS K 7122-2012 "Method for Measuring the Transition Temperature of Plastics".

Specifically, using a differential scanning calorimeter (for example, "DSC6220" manufactured by SII NanoTechnology Co., Ltd.), a measurement container is filled with a sample of about 6.5 mg, and the heating and cooling rate is 10° C./min under a nitrogen flow rate of 30 ml/min. The temperature is raised/cooled between 30°C and 200°C, and the endothermic peak temperature at the second temperature increase is measured as the melting point.

When the endothermic peaks generated by melting do not overlap, but are located at two positions, the endothermic peak on the high temperature side is set to the melting point of the resin, and the endothermic wave The area of the peak is defined as the heat of fusion of the resin.

In addition, at the second temperature increase, the endothermic peak displayed at the highest temperature and the one or more endothermic peaks appearing on the low temperature side have similar temperatures. As a result, when these superimposed to form an endothermic peak, and In the case where the endothermic peak has a plurality of peak temperatures, the highest peak temperature is used as the melting point, and the heat of fusion is obtained based on the area of all the peaks superimposed.

In addition, the melting point and the heat of fusion of the polyethylene component containing plural polyethylene-based resins and the antistatic agent component containing plural polymer-based antistatic agents are adjusted to contain plural polyethylene-based resins at a predetermined ratio After a sample and a sample containing a plurality of polymer antistatic agents at a predetermined ratio, the sample can be obtained by obtaining a DSC curve in the same manner as described above.

<difference of peak temperature>

According to the aforementioned "melting point" measurement method, differential scanning calorimetry analysis of the antistatic agent component was performed.

Then, the peak temperature (P _H ) on the highest temperature side shown by the DSC curve and the peak temperature (P _L ) appearing on the lowest temperature side are obtained, and the difference (P _H -P _L ) is obtained.

<melt tension>

The melt tension of the polyethylene resin can be measured according to the following procedure.

That is, after storing a sample made of polyethylene-based resin in a cylinder arranged in a vertically upright state and having an inner diameter of 15 mm, it is fed at 190°C. Heat and melt for up to 5 minutes.

Then, insert the piston from the upper half into the cylinder, and use the piston to melt the sample in the cylinder from the capillary (mold diameter: 2.095mm, mold length: 8mm, inflow angle: 90) at the lower end of the cylinder using the piston ° (conical)) Extruded at a certain extrusion speed of 0.0676 mm/s to obtain a rope.

After that, the extruded rope-like body is passed through a tension detection pulley arranged under the capillary, and then wound up using a winding roller.

The winding system of the string-shaped body was set at an initial speed of 3.447 mm/s, and then the acceleration was set at 13.1 mm/s ² while slowly increasing the winding speed.

In this winding, the winding speed at which the tension observed by the tension detection pulley drops sharply is referred to as "breaking point speed".

In the tension observed during the period until the speed at the break point is observed, the maximum value and the minimum value of the tension before the speed at the break point are measured. The average value of the maximum value and the minimum value is the "melt tension".

In addition, melt tension can be measured using, for example, a testing machine commercially available under the trade name "Twin Bore Capillary Rheometer Rheologic 5000T" by CEAST Corporation.

<MFR>

The MFR of the polyethylene resin can be measured according to the flow test method of JIS K7210-1999 thermoplastic plastics.

Specifically, MFR (g/10min) can be used in a measuring device under the test conditions of Semi-auto melt indexer (manufactured by Toyo Seiki Co., Ltd.) at a temperature of 190°C, a load of 21.18N, and a preheating time of 5 minutes. Perform the measurement.

<sag amount>

The sagging amount can be made by cutting out three test pieces with a width of 100 mm and a length of 200 mm from the polyethylene resin foamed sheet so that the extrusion direction becomes the longitudinal direction, and then proceed according to the following procedure (refer to FIG. 2) Determination.

First, the ruler R is laminated on the test piece SP.

In addition, the test piece SP and the ruler R are superposed in such a state that one end in the longitudinal direction is aligned with each other.

This bag is sandwiched between two acrylic plates A1 and A2 with a width of 120 mm.

At this time, it is assumed that one end of the test piece SP aligned with the ruler R is also aligned with one end of the width direction of the acrylic plates A1 and A2, which is the other side of the test piece from the acrylic plates A1 and A2. One end protrudes 80mm.

Then, this is placed on the base F, the ruler R is kept horizontal on the test piece SP, and the vertical distance H between the front end of the test piece SP and the ruler R is measured.

The same measurement was performed for the remaining two test pieces, and the arithmetic average of the distance H was defined as the droop amount.

In addition, the sag amount means that the lower the value, the more excellent the strength of the polyethylene resin foam sheet.

<Measurement of exudation>

Quantitative analysis of the components exuded from the polyethylene resin foam sheet can be measured according to the following procedure.

That is, 10 samples of 10 cm×10 cm square were cut from any position of the polyethylene resin foam sheet.

Samples are obtained by sandwiching commercially available 10cm×10cm square glass plates with 2 cut samples, and the samples are made into 5 groups, which are kept at a high temperature set by ISUZU, which is set to a temperature of 65°C and a humidity of 90%RH. 100 hours in a wet tank.

Next, it was left for 1 hour under the conditions of a temperature of 23° C. and a humidity of 30% RH, and the quality of the glass plate after removing the sample was measured using a precision balance (Electronic Balance GR-202 manufactured by AND Corporation).

Then, relative to the initial mass of the glass plate, an increased mass is obtained, and this increased mass is divided by the sample area (200 cm ² ) to obtain the amount of exudation. In addition, the amount of exudation is based on the arithmetic average of 5 sets of samples.

(Examples 2, 3, Comparative Examples 1 to 4)

The polyethylene resin foamed sheets of Examples 2, 3 and Comparative Examples 1 to 4 were prepared in the following manner, and evaluated in the same manner as the polyethylene resin foamed sheet of Example 1.

The results are shown in Table 1.

(Example 2)

Except that the type and amount of the polymer type antistatic agent contained in the antistatic agent component were changed, the polyethylene resin foam sheet was prepared in the same manner as in Example 1 and used as the polyethylene in Example 2 Resin foam sheet.

Specifically, the first polymer type antistatic agent was changed to the trade name "Pelectron LMP-FS" (polyether-polyolefin block copolymer, crystallization temperature: 56°C, melting point: 114) manufactured by Sanyo Chemical Industry Co., Ltd. ℃, heat of fusion: 24J/g), to replace the trade name "Pelectron LMP" manufactured by the same company, and to 100 parts by mass of the polyethylene component, the blending ratio is set to 3.5 parts by mass instead of 3 parts by mass, and relative In the case of 100 parts by mass of the polyethylene component, the formulation ratio of the second polymer-type antistatic agent (trade name "Pelestat 300") was set to 1 part by mass instead of 3 parts by mass, in the same manner as in Example 1. Production of polyethylene resin foam sheet.

(Example 3)

Except that the amount of the polymer type antistatic agent contained in the antistatic agent component was changed, a polyethylene resin foam sheet was prepared in the same manner as in Example 1, which was used as the polyethylene resin resin in Example 3. Bubble slices.

Specifically, it is the same as Example 1 except that the blending ratio of the first polymer type antistatic agent (trade name "Pelectron LMP") is 2 parts by mass instead of 3 parts by mass with respect to 100 parts by mass of the polyethylene component. In the same way, a polyethylene-based resin foam sheet is produced. (The mixing ratio of the second polymer type antistatic agent (trade name "Pelestat 300") is set to 3 parts by mass as in Example 1 with respect to 100 parts by mass of the polyethylene component.)

(Comparative example 1)

Polyethylene was produced in the same manner as in Example 1 except that the type and amount of the polymer antistatic agent contained in the antistatic agent component were changed. The resin foam sheet is regarded as the polyethylene resin foam sheet of Comparative Example 1.

Specifically, one kind of polymer antistatic agent (trade name "IPE-U3", melting point: 220°C) manufactured by IonPhasE is used alone instead of two kinds of polymer type antistatic agents, and the A polyethylene resin foamed sheet was produced in the same manner as in Example 1, except that 100 parts by mass of the ethylene component was used and the blending ratio was 10 parts by mass.

(Comparative example 2)

Low density polyethylene resin-based polyethylene resin manufactured by DOW Chemical, tradename "DFDJ6775" ^{(density: 921kg / m 3, MFR =} 0.3g / 10min, the melt tension = 19.6cN) manufactured by Japan Polyethylene Corporation instead of Low-density polyethylene resin (trade name: "LF580"), and a polymer-type antistatic agent (single trade name "Pelectron HS" (melting point: 135°C) manufactured by Sanyo Chemical Industry Co., Ltd.) alone, except, In the same manner as in Example 1, a polyethylene-based resin foamed sheet was prepared as the polyethylene-based resin foamed sheet of Comparative Example 2. (The ratio of the antistatic agent component to 6 parts by mass relative to 100 parts by mass of the polyethylene component is the same as in Example 1.)

(Comparative example 3)

Except for changing the type and amount of the polymer-type antistatic agent contained in the antistatic agent component, a polyethylene resin foam sheet was produced in the same manner as in Example 1 and used as the polyethylene resin of Comparative Example 3. Foam Flakes.

Specifically, one type of polymer antistatic agent (trade name "IPE-fSAT", melting point: 89°C) manufactured by IonPhasE is used alone instead of using the two types together as a polymer type antistatic agent. A polyethylene resin foamed sheet was produced in the same manner as in Example 1 except that 100 parts by mass of the polyethylene component was used and the blending ratio was 12 parts by mass.

(Comparative example 4)

Except that the type of the polymer type antistatic agent contained in the antistatic agent component was changed, a polyethylene-based resin foam sheet was produced in the same manner as in Example 1, and used as the polyethylene-based resin foam of Comparative Example 4. Flakes.

Specifically, instead of using the first polymer type antistatic agent as the polymer type antistatic agent (trade name "IPE-U3", melting point: 220°C) manufactured by IonPhasE, instead of the trade name manufactured by Sanyo Chemical Industry Co., Ltd. Except "Pelectron LMP", a polyethylene-based resin foam sheet was produced in the same manner as in Example 1.

In addition, the second polymer type antistatic agent is set as the brand name "Pelestat 300" manufactured by Sanyo Chemical Industry Co., Ltd., and the first and second polymer type antistatic agents are based on 100 parts by mass of the polyethylene component. The ratios are all 3 parts by mass and are the same as in Example 1.

In addition, the 1:1 mass ratio contains the antistatic agent component with the trade name "IPE-U3" and the trade name "Pelestat 300". The melting point is 178°C.

As can be seen from the results shown in the above table, according to the present invention, it is possible to provide a polyethylene resin foamed sheet excellent in antistatic properties and thin in thickness.

1‧‧‧polyethylene resin foam sheet

2‧‧‧Glass substrate

10‧‧‧Layered body

Claims (6)

A polyethylene resin foamed sheet comprising: one or more than two polyethylene components selected from low-density polyethylene resin and medium-density polyethylene resin, and one or more An antistatic agent component composed of two or more types of polymer antistatic agents; where the content of the polyethylene component is 100 parts by mass, the content of the antistatic agent component is 3 parts by mass or more and 15 parts by mass or less The DSC curve of the polyethylene component and the DSC curve of the antistatic agent component show one or more than two endothermic peaks, and the peak temperature of the endothermic peak that appears on the highest temperature side in the DSC curve of the polyethylene component When Tm1 is set and the peak temperature of the endothermic peak appearing on the highest temperature side in the DSC curve of the antistatic agent component is Tm2, the following relational expression (1) is satisfied, (Tm1-10)≦Tm2≦(Tm1+ 17)‧‧‧(1). The polyethylene resin foamed sheet as described in item 1 of the patent application range, wherein the DSC curve of the antistatic agent component shows two or more endothermic peaks, and the endothermic peaks appearing on the highest temperature side in the DSC curve The heat of fusion is 30J/g or less. The polyethylene resin foamed sheet as described in item 1 of the patent application range, wherein the DSC curve of the antistatic agent component shows two or more endothermic peaks, and the endothermic peak appearing on the highest temperature side in the DSC curve The difference between the peak temperature of the peak and the peak temperature of the endothermic peak appearing on the lowest temperature side is 95°C or less. The polyethylene resin foamed sheet as described in item 1 of the patent application range has a thickness of 0.15 mm or more and 0.4 mm or less, and the mass per unit area is 15 g/m ² or more and 30 g/m ² or less. The polyethylene resin foamed sheet as described in item 1 of the patent application, wherein the surface resistivity is 1×10 ⁸ Ω or more and 1×10 ¹² Ω or less. The polyethylene resin foamed sheet as described in any one of the items 1 to 5 of the patent application scope, which is used to protect the glass substrate for flat panel display, and is used to interpose between the two aforementioned glass substrates ; When the compression is applied with a pressure of 2N/cm ² in the thickness direction, the polyethylene resin foamed sheet has a thickness of 45% or more and 70% or less before compression, and a pressure of 2N/cm ² is applied in the thickness direction When compressed, the polyethylene resin foamed sheet has a thickness of 0.1 mm or more.

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