TWI541282B - Polyolefin based resin foamed sheet - Google Patents

Description

Polyolefin resin foam sheet

The present invention relates to a polyolefin resin foamed sheet, and more particularly to a polyolefin resin foam sheet containing a polymer type antistatic agent and a surfactant.

The polyolefin-based resin foamed sheet is excellent in cushioning properties due to its flexibility, and is used in packaging materials for electronic parts and home electric appliances, or interleaving papers for glass.

For example, a glass substrate for a flat panel display such as a liquid crystal display or a plasma display is laminated in a state in which a polyolefin resin foamed sheet is interposed, and is supplied from a glass manufacturer to a display manufacturer.

Further, in such a glass substrate, if foreign matter adheres to the surface, various defects may occur in the flat panel display. Therefore, the step of washing with water is temporarily used.

Because of such a situation, there is a demand for a polyolefin-based resin foamed sheet to be used as a backing paper: there is a low possibility of attaching foreign matter to the surface of the glass substrate, and it is easily removed by water washing even if foreign matter adheres. .

In response to such a request, for example, when a polyolefin resin foamed sheet is alternately laminated with a glass substrate to form a laminate, when the polyolefin resin foam sheet is peeled off from the glass substrate, peeling and charging are performed. There is a ripple of static electricity.

Therefore, dust or the like may adhere to the surface of the glass substrate due to the static electricity.

In such a case, an antistatic agent is contained in the polyolefin-based resin foamed sheet which should prevent the occurrence of the above-mentioned static electricity.

As such an antistatic agent, a low molecular type used as a surfactant and a polymer type such as an ion conductive polymer are known.

Among them, the surfactant has a high antistatic effect, and has an effect of exhibiting an antistatic effect at an early stage after the production of the polyolefin resin foamed sheet, but on the other hand, it overflows on the surface of the polyolefin resin foamed sheet ( Bleed out) and attached to the glass substrate.

In the following Patent Document 1 which describes the use of a laminated foam sheet for a glass substrate, the polyolefin resin layer on the surface of the laminated foam sheet is described. It contains a surfactant of a polyalkylene oxide which can be easily removed by washing with water even if it adheres to a glass substrate.

Furthermore, in the following Patent Document 1, the polyolefin-based resin layer further contains a polymer type antistatic agent which is expected to have a function as a mutual solvent of the surfactant and the polyolefin resin.

That is, in the following Patent Document 1, the following matters have been innovated: a polymer type antistatic agent functioning as a remelting agent is used to suppress the overflow of the above surfactant, and at the same time, even if the surfactant is adhered due to overflow It can still be easily removed by water cleaning on a glass substrate.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-42556

As described above, in order to avoid the malfunction of the glass substrate for a flat panel display, it is mainly required to suppress the deposit from the liner as much as possible, and at the same time, it can be easily removed by washing even when the deposit occurs.

However, the component transferred from the polyolefin resin foamed sheet does not necessarily have the image boundary. The hydrophilic component of the surfactant may have a hydrophobic component such as a low molecular weight component originally contained in the polyolefin resin.

In addition, the surfactant is easily transferred to the target material to be contacted, and the effect of suppressing adhesion of the other component contained in the foamed sheet of the polyolefin resin to the target material is exhibited after the transfer.

Therefore, when it is desired to reduce the amount of deposits like a glass substrate for a flat panel display and to abut a member to be washed with water, it is sometimes preferable to prevent the adhesion of the hydrophobic deposit which is difficult to be washed by water to adhere to the surface. It is preferable that the polyolefin resin foamed sheet contains a surfactant having high transferability.

However, since the surfactant which is easily washed by water and adhered to the glass substrate or the like is not easily overflowed, it is contained in the polyolefin resin foam sheet.

Therefore, the conventional polyolefin resin foamed sheet has a problem that it is not suitable for use as a backing paper for a glass substrate for a flat display.

In order to solve such a problem, the present invention has an object of providing a polyolefin-based resin foamed sheet which is suitable for use as a backing paper for a glass substrate for a flat panel display.

The polyolefin-based resin foamed sheet of the above-mentioned problem is a polyolefin-based resin, a polymer-based antistatic agent, and a surfactant, and is higher than 100 parts by mass of the polyolefin-based resin. The molecular antistatic agent has a content of 3 to 20 parts by mass, and is characterized in that it is an anionic surfactant which is solid at 20 ° C as the surfactant, and in order to promote the overflow of the anionic surfactant, It contains an overflow promoter which is miscible with the anionic surfactant and which is more likely to overflow than the anionic surfactant and is liquid at 20 °C.

Further, in the present invention, the overflow promoter is preferably propylene glycol.

Further, in the present invention, the anionic surfactant is preferably a sulfonate surfactant.

Such a polyolefin resin foamed sheet can be suitably used as a backing paper for a glass substrate for a flat display.

An anionic surfactant, in particular, an anionic surfactant which is solid at normal temperature (for example, 20 ° C) is generally easily removed by washing with a nonionic surfactant.

On the other hand, an anionic surfactant which is solid at normal temperature tends to be solidified in a foamed sheet as compared with a liquid at a normal temperature, and tends to easily deteriorate the uniformity of overflow.

In the present invention, the polyolefin-based resin foamed sheet contains a miscibility with an anionic surfactant which is solid at 20 ° C, and is more likely to overflow than the anionic surfactant and is a liquid overflow at 20 ° C. Promoter.

Therefore, in the polyolefin resin foamed sheet of the present invention, the anionic surfactant which is easily removed by water washing is allowed to overflow on the surface by the overflow promoter.

In other words, when the polyolefin-based resin foamed sheet of the present invention is used as a backing paper for a glass substrate for a flat panel display or the like, the anionic surfactant is rapidly transferred to the surface of the target material to be inhibited by water. Cleaning the substances that are not easily removed.

[Formation of the Invention]

The polyolefin resin foamed sheet of the present invention contains a polymer type antistatic agent, an anionic surfactant, and an overflow promoter for promoting the overflow of the anionic surfactant, and a polyolefin resin. The olefin-based resin composition is extruded and foamed to form a sheet-like polyolefin resin foamed sheet (hereinafter, only "Foamed sheet" is used as an example to illustrate its implementation.

In the following, an embodiment of the polyolefin-based resin foamed sheet of the present invention will be described by taking a case of using a liner for a glass substrate for a flat panel display as an example.

As the polyolefin-based resin constituting the foamed sheet of the present embodiment, a polyolefin-based resin such as a polyethylene resin or a polypropylene resin can be used, in particular, a melt mass-flow rate. (hereinafter also referred to as "MFR") is 2 to 6 g/10 min, and a low-density polyethylene resin having a resin density of 925 kg/m ³ or more and 935 kg/m ³ or less is preferably used.

The low-density polyethylene resin of the above-mentioned MFR is preferable because if the MFR is too small, the problem of the kneading property with the polymer type antistatic agent in the extruder may occur, and the antistatic property may be lowered, and the foaming may be performed. When foaming occurs, it is difficult to obtain a good foamed sheet.

Further, it is preferable that the MFR low-density polyethylene resin is such that if the MFR is too large, the melt tension is too low, and a low-density foamed sheet is easily obtained, and a deposit of an eye secretion is easily generated at the tip end of the mold.

That is, it is preferable to use a low-density polyethylene resin having an MFR of 2 g/10 min or more and 6 g/10 min or less because it is not only easy to obtain a foamed sheet which is easily foamed, but also can be removed during production. The trouble of the foregoing deposits can improve the manufacturing efficiency of the foamed sheet.

Moreover, the melt mass flow rate in the present specification, unless otherwise specified, the MFR of the polymer type antistatic agent described later also refers to the melt flow rate of the plastic-thermoplastic plastic according to JIS K 7210:1999 ( MFR)" and the test method of melt volume-flow rate (MVR)" The method described in the method of B (however, the test temperature is 190 ° C, the load is 21.18 N).

The polyolefin-based resin constituting the foamed sheet of the present embodiment preferably has a density as described above because the foaming agent is quickly dispersed from the extruded foam sheet because the resin density is too small, and the resin is present. The rigidity of itself is becoming smaller, so there is no way to The contraction of the system.

Further, the polyolefin-based resin preferably has a density as described above, because if the value of the resin density is too large, the rigidity of the resin itself is too large, and the foamed sheet may be lost as a cushioning property of the packaging material. .

In other words, the polyolefin-based resin constituting the foamed sheet of the present embodiment preferably has a density as described above because of the formation of a foamed sheet which is excellent in cushioning properties.

The polymer type antistatic agent which is a foamed sheet together with the polyolefin resin is preferably a polymer type antistatic agent having a crystallization temperature of less than 90 ° C and an MFR of 10 to 40 g/10 min.

The crystallization temperature of the polymer type antistatic agent is preferably less than 90 ° C. Because the crystallization temperature is too high, the crystallization proceeds in the extruder and the dispersion is deteriorated, and the bubble film is extruded during the extrusion. When the polymer type antistatic agent is not deformed into a block, the distance between the dispersed particles of the antistatic agent is enlarged, and it is difficult to exhibit an antistatic function proportional to the added amount.

That is, it is preferable that the crystallization temperature of the polymer type antistatic agent is less than 90 ° C because it is advantageous for the foamed sheet to exhibit an antistatic function commensurate with the added amount.

Further, the MFR of the polymer type antistatic agent is preferably in the range as described above because the MFR of the polymer type antistatic agent is too small, and the dispersion of the polyethylene resin in the extruder or in the mold is uneven. Although the surface specific resistance is excellent, the static decay rate tends to deteriorate.

In addition, it is preferable that the MFR is in the range as described above because the use of the polymer type antistatic agent having an excessive MFR reduces the dispersibility in the polyolefin resin and simultaneously melts the polyolefin resin composition. The tension is lowered, and a low-density foamed sheet cannot be obtained, or there may be a large bubble which causes a connected sample.

In other words, the MFR of the polymer type antistatic agent is preferably within the above range because it is advantageous in that the foamed sheet having a good foaming state exhibits an excellent electrostatic decay rate.

In addition, in the present specification, the crystallization temperature is a value measured by the method described in JIS K7122 "Method for Measuring Transfer Temperature of Plastics".

Specifically, a differential scanning calorimeter (for example, "DSC6220" manufactured by SII Nano Technology Co., Ltd.) can be used, and about 6.5 mg of the sample is filled in the measuring container, and the flow rate of nitrogen gas is set at 30 ml/min, and the temperature is raised at 10 ° C / min. After heating from 30 ° C to 200 ° C, the film was cooled at a cooling rate of 10 ° C / min, and the peak temperature at the time of cooling was measured as the crystallization temperature.

In addition, when there are two or more of the peaks of the heat generation, the temperature of the peak of the peak of the highest temperature side among the peaks of the area of 5% or more of the total peak area is used as the crystallization temperature.

Examples of the polymer type antistatic agent include ions such as polyethylene oxide, polypropylene oxide, polyethylene glycol, polyester decylamine, polyether ester guanamine, and ethylene-methacrylic acid copolymer. A quaternary ammonium salt such as a polymer or a polyethylene glycol methacrylate copolymer, and a copolymer of an olefin block and a hydrophilic block described in JP-A-2001-278985.

Among these, a copolymer of an olefin block and a hydrophilic block is preferable, and a polyether-polyolefin block copolymer (polyether block and polyolefin block) is contained in the polyolefin resin composition. The block copolymer) is preferably the above-mentioned polymer type antistatic agent.

Further, as the polymer type antistatic agent, a mixture of two or more kinds of substances may be used, and in order to further improve the antistatic property, a polyamine may be mixed in the block copolymer. Or the copolymerization of the polyamine block is further carried out.

As the polymer type antistatic agent, a copolymer containing an olefin block of 70 mol% or more of propylene and a polyether block is preferable as a main component.

Here, the copolymer is a "main component", and the ratio of the polyether-polyolefin block copolymer in the polymer type antistatic agent is 50% by mass or more.

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

In the polyolefin-based resin composition constituting the polyolefin-based resin foamed sheet of the present embodiment, the blend ratio of the polyolefin-based resin and the polymer-type antistatic agent is relative to the polyolefin-based resin. The ratio of the polymer type antistatic agent to 3 to 20 parts by mass is important for 100 parts by mass.

The blending ratio of the polymer-type antistatic agent to the polyolefin-based resin composition is important within the above range, and when it is at least the lower limit of the above range, the antistatic property of the foamed sheet can be prevented from being insufficient. The dust adheres to the glass substrate, and for example, it is possible to suppress peeling off static electricity when peeling off from the glass substrate.

In addition, it is important that the blending ratio of the polymer-type antistatic agent of the polyolefin-based resin composition is within the above range, and when it is at most the upper limit of the above range, the cost increase of the foamed sheet is not inhibited. It is possible to prevent the foaming property of the polyolefin resin composition from being lowered, and it is impossible to obtain a foamed sheet having a low density.

The surfactant which is contained in the polyolefin resin foam sheet together with the polymer type antistatic agent is an antistatic function of a so-called low molecular type antistatic agent. In the present embodiment, it is used in the embodiment. An anionic surfactant which is a solid at 20 ° C is important, and an anionic surfactant which has an HLB value of 20 or more (normally an upper limit of 50) obtained by the Davies method is particularly preferable.

Further, the Davies method is used to divide the surfactant molecules according to atomic groups (or functional groups) by giving the base number unique to each atomic group and calculating the HLB value, for example, according to Sanyo Chemical Industry Co., Ltd. The method described in the book title "Introduction to Surfactant" is calculated in detail.

Furthermore, as long as there is no specific indication in the future, the "HLB value" represents the "HLB value obtained by the Davies method".

As the anionic surfactant, for example, dialkyl sulfosuccinate, alkyl sulfonate, alpha olefin sulfonate, linear alkyl benzene sulfonate, naphthalene may be used. a sulfonate surfactant such as a sulfonate-formaldehyde condensate, an alkylnaphthalenesulfonate or an N-methyl-N-mercapto taurate; an aliphatic monocarboxylate or a polyoxyethylene alkyl group; a carboxylate surfactant such as an ether carboxylate, N-mercaptocresine or N-mercapto branamine; alkyl sulfate, polyoxyethylene alkyl ether sulfate, fat sulfate A sulfate salt-based surfactant such as an ester salt; a phosphate salt-based surfactant such as an alkyl phosphate, a polyoxyethylene alkyl ether phosphate or a polyoxyethylene alkylphenyl ether phosphate.

Further, when the content of the anionic surfactant is too small in the foamed sheet, it is difficult to anticipate the effect of preventing substances other than the anionic surfactant from adhering to the surface of the glass substrate, and it is difficult to impart a foamed sheet at the same time. Sufficient antistatic effect.

On the other hand, there is a limit to the effect of suppressing the adhesion of the adhering substances other than the antistatic effect or the anionic surfactant. Therefore, even if the foamed sheet contains more than necessary of the anionic surfactant, the manufacturing is only made. Foamed sheets have become difficult.

In such a case, the content of the anionic surfactant in the foamed sheet is preferably 0.1 to 5 parts by mass based on 100 parts by mass of the polyolefin resin.

Among the above-mentioned examples, in the present embodiment, it is important that the foamed sheet contains the anionic surfactant, and it is easy to wash off from the surface of the glass substrate, and it is important to use a solid at 20 ° C. Among them, a sulfonate-based surfactant which is solid at 20 ° C is particularly preferable.

As the sulfonate-based surfactant, any of a dialkyl sulfosuccinate, a linear alkylbenzenesulfonate, and an alkylsulfonate is preferably used.

In particular, an anionic surfactant is preferred to contain sodium which is a relative ion when dispersed in water or the like, sodium dialkyl sulfosuccinate, sodium linear alkylbenzene sulfonate, and sodium alkyl sulfonate. A sodium sulfonate-based surfactant is particularly preferred.

Further, the anionic surfactant may be used alone or in combination of two or more.

As the overflow promoter for promoting the overflow of the anionic surfactant, it is possible to use a solvent which is miscible with the anionic surfactant and which is more likely to overflow than the anionic surfactant and which is liquid at normal temperature (20 ° C).

For the overflow promoter, for example, it is preferred that the anionic surfactant is dissolved at a concentration of 10% by mass or more at 20° C., and an anionic surfactant is exhibited at a concentration of 40% by mass or more. Soluble miscible ones are particularly desirable.

Further, the overflow promoter generally has an SP value deviated from the SP value of the polyolefin resin in order to promote the overflow of the anionic surfactant, and even an anion having a similar SP value to the polyolefin resin is used because of such an overflow promoter. The surfactant can also easily overflow.

Whether or not the overflow promoter is more likely to overflow than the anionic surfactant, for example, can be judged from the SP value calculated by Fedors' estimation algorithm, and can be judged by a large deviation from the SP value of the polyolefin resin.

Further, for example, when a polyethylene resin having an SP value of 7 to 9 is used, the SP value of the overflow promoter is about 10 to 15, and the SP value of the anionic surfactant is preferably about 7 to 10.

As such an overflow promoter, for example, propylene glycol, ethylene glycol, polyethylene glycol, propylene glycol phenyl ether, 1-3-butylene glycol, ethylene glycol monobutyl ether, diethylene glycol monoethyl Ethyl alcohol, ethylene glycol monoethyl ether or the like is particularly excellent in the effect of promoting the overflow of the anionic surfactant, and it is preferable to have propylene glycol which is easily washed away by water.

In addition, the content of the overflow promoter contained in the foamed sheet is usually 0.1 to 3 times by mass based on the content of the anionic surfactant. More preferably, it is 0.2 times to 1.5 times.

In the case where the sodium-containing resin foamed sheet of the present embodiment is immersed in water to elute sodium ions, the anionic interface activity is adjusted, for example, when the sodium-containing resin foamed sheet of the present embodiment is used as an anionic surfactant. The content of the agent and the overflow promoter in the polyolefin resin foamed sheet is preferably such that the amount of sodium ion eluted per unit area is 20 ng/cm ² to 100 ng/cm ² .

For the elution amount of the sodium ion, for example, a polyolefin resin foamed sheet can be cut into pieces having a size of 10 cm × 10 cm for measurement.

As an example of the method for measuring the elution amount of the sodium ion, the following method can be employed.

First, a zipper bag having a size of 12 cm × 17 cm was prepared, 50 ml of distilled water was poured thereinto, and after heating at 70 ° C for 1 hour, the internal water was poured off and dried.

After the dried zipper bag was poured into 50 ml of distilled water again, the above-mentioned section was placed and the air was removed as much as possible, and this was stored in a 60 ° C dryer in a flat state and heated for 20 minutes.

After 20 minutes passed, the zipper bag was temporarily taken out, shaken several times and given vibration, and returned to the dryer at 60 ° C again, and stored in a state of being placed in a flat state opposite to the upper side and the lower side of the front zipper bag.

Then, after 20 minutes, the zipper bag was taken out, and the internal distilled water was collected several times in the same manner as before, and the amount of sodium ions contained in the distilled water was quantified by inductively coupled plasma (ICP) luminescence analysis. Got it.

The sodium ion can be quantified by the ICP emission spectrometry. For example, a multi-type ICP emission spectroscopic analyzer manufactured by Shimadzu Corporation can be used, and the model number is "ICPE-9000". The exposure time is 30 seconds, and the high frequency output is 1.20 kW. The conditions of the sub-plasma-assisted flow rate (0.7-10.0-0.6 (l/min)) were carried out.

Further, the anionic surfactant is not in a powder form in a natural state, and in order to improve the dispersibility to water or resin, etc., it is possible to use a water-soluble inorganic salt such as sodium sulfate (sodium sulfate), sodium chloride or sodium carbonate. When it is used in advance and powdered, the sodium ions eluted from the polyolefin resin foamed sheet by the water-soluble inorganic salt are combined with the sodium ions eluted by the anionic surfactant to adjust the dissolution. The amount (20 ng/cm ² to 100 ng/cm ² ) is ideal.

In other words, the polyolefin-based resin foamed sheet of the present embodiment is preferably adjusted so that the sodium ion elution amount is 20 ng/cm ² to 100 ng/cm ² regardless of the source thereof.

The amount of sodium ions eluted from the polyolefin resin foamed sheet by an anionic surfactant or the like is preferably 20 ng/cm ² to 100 ng/cm ² because the sodium ion elution amount is set to 20 ng/cm ² or more. It is possible to more reliably remove the material which has overflowed from the polyolefin resin foamed sheet.

Further, the upper limit is set to 100 ng/cm ² because if the polyolefin-based resin foamed sheet contains an excessive amount of sodium which may be eluted, the sustained antistatic effect of the polymer-type antistatic agent may be I can't fully play it.

In other words, it is preferable that the amount of sodium is adjusted to a level of 100 ng/cm ² or less in order to sufficiently adjust the function of the polymer antistatic agent.

In addition, when the amount of elution of sodium ions other than the anionic surfactant accounts for more than half of the amount, it is difficult to sufficiently expect the above-described effects. Therefore, 50% of the sodium contained in the polyolefin resin foam sheet is 50%. The above is preferably from an anionic surfactant.

Further, since the polyolefin-based resin foamed sheet of the present embodiment is produced by extrusion foaming, it contains a component necessary for foaming in addition to the above-described components.

The foaming agent or the air bubble adjusting agent may be mentioned as a component for foaming, and a foaming sheet may contain a heat stabilizer, an ultraviolet absorber, an antioxidant, a coloring agent, etc., as needed. Additives.

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

In particular, as the aforementioned blowing agent, a mixed butane of isobutane and n-butane is preferable.

If the mixed butane of isobutane/n-butane thus obtained is used, the rapid escape of the blowing agent in the extrusion foaming step is suppressed by isobutane, and on the other hand, the polyolefin resin N-butane with excellent mutual solubility inhibits the increase of the continuous bubble rate, so A foamed sheet having excellent shrinkage and a reduced open cell ratio is obtained.

In addition, the amount of the foaming agent to be used in the extrusion foaming is also required to be a degree of foaming, and is usually set to 5 with respect to 100 parts by mass of the total of the polyolefin-based resin and the polymer-based antistatic agent. More than or equal to 25 parts by mass.

In general, the addition ratio of the foaming agent is such a range that it is easy to obtain sufficient foaming when the foaming agent is 5 parts by mass or more, and it is possible to suppress breakage of the bubble film during foaming at 25 parts by mass or less.

In addition, as the bubble adjusting agent for adjusting the bubbles formed by the foaming agent, an inorganic powder such as talc or cerium oxide or a polycarboxylic acid and carbonic acid which is also used as a decomposition type foaming agent may be mentioned. Sodium or a mixture of baking soda (sodium bicarbonate), guanamine azodicarboxylate, and the like.

These can be used alone or in combination with the majority. The amount of the bubble modifier to be added is preferably 0.5 parts by mass or less per 100 parts by mass of the polyolefin resin.

The density (visual density) of the foamed sheet is not particularly limited as long as it has a cushioning property which is generally required as a backing paper of a glass substrate, and is usually less than 70 kg/m ^{3 .} It is preferably 10 kg/m ³ or more and 60 kg/m ³ or less.

Since such a density is selected as an ideal range, since the density is 70 kg/m ³ or less, it is possible to suppress the insufficient flexibility of the foamed sheet and to achieve a low cushioning property.

On the other hand, if the density is too small, the strength of the foamed sheet is not sufficient, and the cushioning property is low.

Further, when the thickness of the bubble film is too thin, the shrinkage becomes large, and when a long foamed sheet is produced, it becomes difficult to roll it into a roll.

Therefore, the density of the foamed sheet is preferably 10 kg/m ³ or more, and more preferably 15 kg/m ³ or more.

The foamed sheet according to the present embodiment can be produced in the same manner as a general extruded foam sheet. As an example, the polyolefin-based resin composition can be extruded. The foaming step is performed to produce an extrusion foaming step of extruding the foamed sheet, and the extruded sheet is rolled up by a winder to prepare a winding step of the original roll, so that the wound original roll is matured. The ripening step during the period is produced by rewinding the original roll by a rewinder or the like into a decorative winding step for the product roll.

As described above, the foamed sheet produced by extrusion foaming is used as the backing paper of the glass substrate in the present embodiment, but the use of the foamed sheet of the present invention is not limited to the glass substrate. In the backing paper, even if the material other than the glass substrate is a predetermined water washer, it is expected that the same effect can be obtained by using it as a backing paper used as a glass substrate for packaging or the like.

[Examples]

Hereinafter, the present invention will be described in further detail by way of examples, but the invention is not limited thereto.

(Example 1)

100 parts by mass of a low-density polyethylene resin (trade name: "LF580", density: 929 kg/m ³ , MFR = 4.0 g/10 min) manufactured by Nippon Polyethylene Co., Ltd., manufactured by Sanyo Chemical Co., Ltd. Polymer type antistatic agent (polyether-polypropylene block copolymer, trade name: "PELESTAT 300", crystallization temperature: 85.4 ° C, MFR = 30 g/10 min) 7 parts by mass, and bubbles made by Sankyo Chemical Co., Ltd. Master batch (master batch containing azomethicamine: trade name "Cellmic MB1023") 0.05 parts by mass blended blend supplied to the first extrusion of a tandem extruder The machine (cylinder diameter: φ 90 mm) was melt-kneaded so that the maximum reaching temperature in the extruder became 210 °C.

Further, from the middle of the first extruder, mixed butane (isobutane/n-butane = 50/50 (mole ratio)) as a foaming agent is used to be 100 mass with respect to the aforementioned low-density polyethylene resin. The proportion was 6.2 parts by mass.

In addition, "CHEMISTAT 3033" (trade name) manufactured by Sanyo Chemical Co., Ltd., which contains 90% or more of the alkyl sulfonate (softening point 70 ° C, HLB value 40) of 90 to 16 carbon atoms, is prepared as an overflow. Promoter propylene glycol (Asahi Glass) Co., Ltd., melting point: -59 ° C, liquid at room temperature (20 ° C), and these solutions are mixed at a mass ratio of 60:40 ("CHEMISTAT 3033": propylene glycol) relative to the aforementioned low density polyethylene resin The ratio of 100 parts by mass was 1.5 parts by mass, and further, melt kneading was carried out.

After the melt-kneading of the first extruder, the second extruder (cylinder diameter: φ 150 mm) connected to the first extruder is cooled to a temperature range (111 ° C) suitable for foaming, and utilized. A circular die having an exit diameter of 220 mm (gap 0.31 mm) was extruded and foamed in the atmosphere.

After being squeezed and foamed, the cylindrical foam is cooled by a blown air, cooled along a cooling mandrel having a diameter of 770 mm and a length of 650 mm, and extruded along a cutter disposed on the rear side of the cooling mandrel. The cylindrical foam was cut in the direction to obtain a long strip-shaped foamed sheet.

<thickness. Density>

The thickness of the obtained foamed sheet was measured by a constant pressure thickness measuring machine (Model PG-(Special) S-37387 ("SCM-627") manufactured by Teclock Co., Ltd., and the result was 0.5 mm, and the density was (visual density). JIS K 7222:2005 "Foamed plastic and rubber - method for determining apparent density", the result was 51 kg/m ³ .

<contact angle>

Moreover, the suitability of the backing paper as a glass substrate was determined by the contact angle in the following manner.

First, the foamed sheet was cut into a size of 5 cm × 10 cm, and it was washed. The dried glass plate (the alkali-free glass OA-10G made by Nippon Electric Glass Co., Ltd.) was loaded with a weight of 1 kg to load the entire foamed sheet at a temperature of 60 ° C and a relative humidity of 80. After standing for 24 hours in a constant temperature and humidity chamber (manufactured by ISUZU Co., Ltd., trade name "HPAV-120-40"), it was dried at a temperature of 30 ° C and a relative humidity of 0% for 24 hours.

The contact angle of the purified water on the surface of the glass plate which is in contact with the foamed sheet was measured by a solid-liquid interface analyzer (trade name "DROP MASTER300") manufactured by Kyowa Interface Chemical Co., Ltd., and used as a contact angle before washing.

A glass plate which was subjected to a load and contacted with a foamed sheet and which had been subjected to treatment at 60 ° C, 80% RH × 24 hours - 30 ° C 0% RH × 24 hours, to contain 0.4% household alkaline detergent ( Washed with washing water manufactured by Kao Co., Ltd., trade name "Attack", and rinsed with distilled water, and dried at a temperature of 30 ° C and a relative humidity of 0% for 24 hours.

The contact angle of the glass plate after the washing was measured as the contact angle after washing.

Further, the contact angle before washing and the contact angle after washing were measured 20 times each, and the average value was calculated.

As a result, it was confirmed that the contact angle before washing was 7.5 degrees, and the contact angle after washing was 6.5 degrees, and it was confirmed that the portion contacting the foamed sheet was cleaned by washing.

<Sodium ion elution amount>

The obtained foamed sheet was cut into a size of 10 cm × 10 cm to prepare a slice, and the eluted amount of sodium ions was measured as described below.

First, a 12 cm × 17 cm zipper bag was prepared, 50 mm of distilled water was poured thereinto, and after heating at 70 ° C for 1 hour, the internal water was poured off and dried.

While placing the above-mentioned slice in the zipper bag, 50 ml of distilled water was poured again, and the air was removed as much as possible. This was stored in a dryer at 60 ° C for 20 minutes, and then shaken by hand several times, after that. Turn it over and place it in the dryer for 20 minutes.

Then, the zipper bag was taken out from the dryer and shaken several times by hand, and the inside distilled water was collected, and the sodium contained in the distilled water was quantified by a composite ICP emission spectroscopic analyzer (model "ICPE-9000") manufactured by Shimadzu Corporation. The amount of ions.

Further, the measurement conditions of the ICP emission analysis were an exposure time of 30 seconds, a high frequency output of 1.20 kW, and a carrier-plasma-assisted flow rate (0.7-10.0-0.6 (l/min)).

Then, from the amount of sodium ions obtained, the mass (M _Na : ng) of all the sodium ions contained in 50 ml of distilled water was determined, and this was divided by the area of the slice (the total "200 cm ² " in the surface) to determine the area per unit area. The amount of sodium ion eluted.

(Examples 2 to 6)

A foamed sheet was produced in the same manner as in Example 1 except that the type and amount of the anionic surfactant and the overflow promoter contained in the foamed sheet were changed. Example 1 was evaluated in the same manner.

Further, in Example 2, a linear alkylbenzenesulfonate such as dodecylbenzenesulfonate manufactured by Kao Co., Ltd. (softening point: 270 ° C, HLB value: 36.2) was used as a main component (linear alkyl group). The product name "NEOPELEX No. 6" having a sodium benzenesulfonate content of about 60% by mass and the residue: sodium sulfate is used as an anionic surfactant, and in Examples 4 and 5, "ethylene glycol" is used as an overflow promotion. Agent.

Then, in Example 6, a foamed sheet was obtained using polyethylene glycol 300 (manufactured by Sanyo Chemical Co., Ltd., melting point - 13 ° C) as an overflow promoter.

(Comparative Examples 1, 2)

A foamed sheet piece was produced in the same manner as in Example 1 except that a nonionic surfactant was used instead of the anionic surfactant, and evaluation was performed in the same manner as in Example 1.

Further, in Comparative Example 1, as a nonionic surfactant, diglycerin monooleate (trade name "ESR720", softening point 40 ° C, HLB value 9.0) manufactured by Riken VITAMIN Co., Ltd. was used, and in Comparative Example 2, As a nonionic surfactant, a stearin monoglyceride (trade name "PV-100") manufactured by Riken VITAMIN Co., Ltd. was used.

(Comparative Examples 3 and 4)

A foamed sheet piece was produced in the same manner as in Example 1 except that the anionic surfactant was not contained, and evaluation was carried out in the same manner as in Example 1.

Further, in Comparative Example 3, only polypropylene glycol which is a function of an overflow promoter was contained, and in Comparative Example 4, any of an anionic surfactant and an overflow promoter were not contained.

(Comparative Example 5)

A foamed sheet was obtained by merely adding an anionic surfactant. Specifically, a portion of CHEMISTAT 3033 4.0 was added to obtain a foamed sheet having a thickness of 0.5 mm.

The evaluation results of the examples and comparative examples are shown in Table 1 below.

Moreover, the foamed sheet of Comparative Example 5 has a serious surface spot, and although an anti-additive is added Electrostatic agent, but the generation of static electricity is not good.

For this reason, the measurement of the contact angle was not performed on the foamed sheet of Comparative Example 5.

The foamed sheet of the present invention can also be understood from the results shown in the above table, and is useful for a backing paper of a glass substrate or the like.

Claims (7)

A polyolefin resin foamed sheet comprising a polyolefin resin, a polymer type antistatic agent, and a surfactant, and the content of the polymer type antistatic agent is 100 parts by mass based on the polyolefin resin. 3 to 20 parts by mass; characterized by: as the surfactant, an anionic surfactant containing a solid at 20 ° C, and in order to promote the overflow of the anionic surfactant, further containing an interface with the anionic surfactant The agent is mutually soluble and is more likely to overflow than the anionic surfactant and is a liquid overflow promoter at 20 °C. The polyolefin resin foamed sheet of the first aspect of the invention, wherein the overflow promoter is propylene glycol. The polyolefin resin foamed sheet of the first aspect of the invention, wherein the anionic surfactant is a sulfonate surfactant. The polyolefin resin foamed sheet of the second aspect of the invention, wherein the anionic surfactant is a sulfonate surfactant. The polyolefin-based resin foamed sheet of the third aspect of the invention, wherein the anionic surfactant contains sodium which is a relative ion, and when it is immersed in water to elute sodium ions, the amount of sodium ion eluted per unit area It becomes 20 ng/cm ² to 100 ng/cm ² . The polyolefin-based resin foamed sheet of the fourth aspect of the invention, wherein the anionic surfactant contains sodium which is a relative ion, and when it is immersed in water to elute sodium ions, the amount of sodium ion eluted per unit area It becomes 20 ng/cm ² to 100 ng/cm ² . The polyolefin-based resin foamed sheet according to any one of the first to sixth aspects of the invention is used as a backing paper for a glass substrate for a flat panel display.