KR102392965B1 - The manufacturing method of polyethylene-type resin extrusion foam seat|seet, polyethylene-type resin extrusion foam seat|seet, and the slip sheet for glass plates using the same - Google Patents

Abstract

A method for producing a polyethylene-based resin extruded foam sheet by extruding and foaming a foamable molten resin composition obtained by kneading low-density polyethylene, a physical foaming agent and an antistatic agent, wherein the foam sheet has a thickness in the range of 0.05 to 0.5 mm, and as an antistatic agent A method for producing a polyethylene-based resin extruded foam sheet, characterized in that a polymer-type antistatic agent having a melting point difference with a low-density polyethylene in the range of -10 to +10 ° C and a melt flow rate of 10 g/10 min or more is used. provided Thereby, in spite of the very thin thickness, the generation of small holes and through holes is prevented and suppressed even in mid- to long-term continuous production, high-quality, excellent strength and cushioning properties, and the antistatic performance is also sufficiently expressed. A novel polyethylene-based resin extruded foam sheet suitable as an interleaving sheet for glass plates is obtained.

Description

The manufacturing method of polyethylene-type resin extrusion foam seat|seet, polyethylene-type resin extrusion foam seat|seet, and the slip sheet for glass plates using the same

This invention relates to the manufacturing method of a novel polyethylene-type resin extrusion foam seat|seet, a novel polyethylene-type resin extrusion foam sheet|seat, and the slip sheet for glass plates using the same.

Polyethylene-based resin extruded foam sheet (hereinafter also referred to as foam sheet) is rich in antistatic function, flexibility and buffering properties, so it can prevent damage and breakage of the object to be packaged. has been widely used. Moreover, with the recent development and demand expansion of thin TVs, etc., damage to the surface of a glass substrate at the time of packing and conveyance of the glass substrate for image display apparatuses, such as a liquid crystal display, a plasma display, and an electroluminescent display, is prevented In order to do so, foam seat|seet provided with antistatic performance is used as an interleaving paper arrange|positioned between glass plates (patent document 1, patent document 2).

Up to now, glass plates of various thicknesses have been developed as glass plates for image display devices such as liquid crystal panels, but in recent years, very thin glass plates with a thickness of about 0.5 mm or less have been produced in view of weight reduction, energy saving, production cost, etc. . If a thick foam sheet having a thickness of about 1 mm to 2 mm as in the prior art is used as the separator for such a thin glass plate, the loading efficiency not only decreases, but also because the thickness of the separator on the glass plate becomes too thick, depending on the side on which a load is applied. There was a risk that the glass plate could be damaged.

For this reason, although development of thin foam seat|seet is advancing as an interleaving sheet corresponding to a thin glass plate, the problem that small holes and through-holes become easy to generate|occur|produce in foam seat|seet when it tries to manufacture thin foam seat|seet. happened.

In order to cope with such a problem, the present inventors first developed the polyethylene-type resin extrusion foam seat|seet whose average thickness is 0.5 mm or less by using a specific bubble regulator etc. (patent document 3, patent document 4).

These polyethylene-type resin extruded foam sheets are of high quality in which the generation of small holes and through-holes is prevented and suppressed, even if the average thickness is 0.5 mm or less, and has excellent antistatic performance and buffering properties.

Japanese Patent Laid-Open No. 2007-262409 Japanese Patent Laid-Open No. 2012-20766 Japanese Patent Laid-Open No. 2014-43553 International Publication No. 2014/030513

Although it can be said that the polyethylene-based resin extruded foam sheet is suitable as an interlayer for a thin glass plate, the generation of small holes and through holes is stably prevented and suppressed even in mid- to long-term continuous production over 2 to 7 days, etc. There is a strong demand for the development of a polyethylene-based resin extruded foam sheet exhibiting high quality and excellent antistatic performance.

The present invention has been made in view of the above circumstances, and despite its very thin thickness, the occurrence of small holes and through-holes is prevented and suppressed even in mid- to long-term continuous production, high-quality, excellent strength and buffering properties, and charging It aims at providing the manufacturing method of the novel polyethylene-type resin extruded foam seat|seet suitable as an interleaving sheet for glass plates which also fully expresses prevention performance, a novel polyethylene-type resin foam seat|seet, and the slip sheet for glass plates using the same.

This invention provides the manufacturing method of the novel polyethylene-type resin extruded foam seat|seet described below, the novel polyethylene-type resin extrusion foam seat|seet, and the slip sheet for glass plates using the same.

<1> A method for producing a polyethylene-based resin extruded foam sheet by extruding and foaming a foamable molten resin composition containing low-density polyethylene, a physical foaming agent and an antistatic agent, wherein the foam sheet has a thickness in the range of 0.05 to 0.5 mm, Production of polyethylene-based resin extruded foam sheet, characterized in that a polymer type antistatic agent having a melting point difference of -10 to +10 ° C. and a melt flow rate of 10 g/10 min or more is used as the inhibitor as an inhibitor Way.

<2> The method according to <1>,

The melting point of the polymer-type antistatic agent is a method for producing a polyethylene-based resin extruded foam sheet, characterized in that 120 ℃ or less.

<3> The method according to <1> or <2>,

The ratio of the melt flow rate of the low-density polyethylene to the melt flow rate of the polymer-type antistatic agent (melt flow rate of low-density polyethylene/melt flow rate of the polymer-type antistatic agent) is 2 or less Production of a polyethylene-based resin extruded foam sheet, characterized in that Way.

<4> The method according to <1> or <2>,

3 to 25 parts by mass of a high molecular weight antistatic agent are blended with respect to 100 parts by mass of the low-density polyethylene.

<5> A low-density polyethylene-based resin extruded foam sheet containing an antistatic agent, the base resin of which is low-density polyethylene, wherein the thickness is in the range of 0.05 mm to 0.5 mm, and the apparent density is in the range of 20 to 450 kg/m 3 , and the antistatic agent A polyethylene-based resin extruded foam sheet, characterized in that it is a polymer type antistatic agent having a melting point difference with a low-density polyethylene within a range of -10°C to +10°C, and a melt flow rate of 10 g/10 min or more.

<6> The interleaving sheet for glass plates which consists of the polyethylene-type resin extrusion foam seat|seet as described in <5>.

(Effects of the Invention)

According to the manufacturing method of the present invention, not only for a short period of time such as several hours, but also for medium and long-term continuous production over several days, the occurrence of small holes and through holes is prevented and suppressed, high-quality, very thin, and excellent antistatic performance. An expressed polyethylene-type resin foam seat|seet can be obtained.

In addition, the novel polyethylene-based resin foam sheet according to the present invention is of high quality in which the occurrence of small holes and through holes is prevented and suppressed, and also exhibits sufficient antistatic performance despite its very thin thickness.

Therefore, the novel polyethylene-based resin foam sheet of the present invention can be used in fields where an antistatic function or the like is strongly required, particularly when transporting or packing thin glass plates for image display devices such as liquid crystal displays, plasma displays, and electroluminescence displays. Widely demanded as an interleaving paper for a glass plate for preventing damage is anticipated.

Moreover, the novel polyethylene-type resin foam seat|seet of this invention can be manufactured continuously over a mid- to long-term, and is a foam seat|seet with very high production efficiency industrially.

The method for producing a polyethylene-based resin extruded foam sheet (hereinafter, simply referred to as foam sheet) of the present invention is to produce a polyethylene-based resin extruded foam sheet by extruding and foaming a foamable molten resin composition containing low-density polyethylene, a physical foaming agent and an antistatic agent As a method of making the foam sheet, the thickness of the foam sheet is in the range of 0.05 to 0.5 mm, the difference in melting point with the low-density polyethylene as an antistatic agent is in the range of -10 to +10°C, and the melt flow rate is 10 g/10 min or more. It is characterized by using a polymer type antistatic agent.

(Manufacturing method of foam sheet)

In the manufacturing method of the foam seat|seet of this invention, additives, such as low-density polyethylene, antistatic agent, and other additives added as needed, are supplied to an extruder and heat-kneaded at about 200 degreeC, which is a material for molding a foam seat|seet, To obtain a molten resin composition . Then, a physical foaming agent is press-injected into this molten resin composition, and it kneads|mixed and it is set as a foamable molten resin composition in an extruder. Then, this foamable molten resin composition is cooled to foaming appropriate temperature.

Here, the appropriate foaming temperature of the foamable molten resin composition is a temperature at which a foamed layer can be easily obtained, preferably in the range of [melting point + 0 ° C] to [melting point + 15 ° C.] of low-density polyethylene, more preferably [ melting point +2°C] to [melting point +10°C].

Then, the above-mentioned foamable molten resin composition is introduced into an annular die, extruded from the die tip lip portion into the atmosphere to foam the expandable molten resin composition to produce a tubular extruded foam, and this tubular extruded foam is expanded with a mandrel (blow up) ) while taking over, it is possible to obtain a foam sheet by cutting along the extrusion direction.

(Material for forming foam sheet)

In the manufacturing method of this invention, as mentioned above, it forms by extruding and foaming the foamable molten resin composition which mix|blended the low-density polyethylene, the antistatic agent, the physical foaming agent, and the foam|bubble control agent and other additives as needed. Below, the material used in order to shape|mold foam seat|seet is demonstrated in detail.

(Low Density Polyethylene)

As the low-density polyethylene, polyethylene having a long-chain branched structure and having a density of 900 kg/m 3 or more and less than 930 kg/m 3 can be used. The said resin shows favorable foamability, and the foam seat|seet obtained becomes a thing excellent in a buffering characteristic. From the above point of view, the density of the low-density polyethylene is preferably 910 kg/m 3 or more and 925 kg/m 3 or less. The melting point of the low-density polyethylene is preferably 100 to 120 °C, more preferably 105 to 115 °C. Melting|fusing point of the said low density polyethylene can be measured by the method based on JISK7121-1987. Specifically, using a differential scanning calorimeter, heating is performed by heating and melting by raising the temperature from 40°C to 200°C at 10°C/min, holding at that temperature for 10 minutes, cooling to 40°C at 10°C/min, after heat treatment, and then heating again A melting peak is obtained by raising the temperature from 40°C to 200°C at a rate of 10°C/min. And let the temperature of the apex of the largest melting peak among the obtained melting peaks be melting|fusing point.

Moreover, it is preferable that it is 5 g/10min or more, and, as for the melt flow rate of a low density polyethylene, it is more preferable that it is 10 g/10min or more, It is more preferable that it is 15 g/10min or more. The melt flow rate is a value measured at a temperature of 190° C. and a load of 2.16 kg according to JIS K7210-1:2014.

In addition, when the low-density polyethylene is a mixture of two or more types, the melting point and melt flow rate of the mixture are specified by the melting point and melt flow rate measured with respect to what was previously melt-kneaded in an extruder.

As a commercial item of the low-density polyethylene preferably used by this invention, "Product name NUC8321" by NUC Corporation (melt flow rate 1.9 g/10min, melting|fusing point 112 degreeC) etc. are illustrated, for example.

In the low-density polyethylene, other polyethylene-based resins, polypropylene-based resins, and thermoplastic resins such as polystyrene-based resins, ethylene propylene rubber, styrene-butadiene-styrene block copolymers, etc. An elastomer etc. may be included.

The other polyethylene-based resin is a resin having an ethylene component unit of 50 mol% or more, and specifically, high-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene- An ethyl acrylate copolymer etc., and a mixture of 2 or more types thereof are illustrated further.

20 mass parts or less are preferable with respect to 100 mass parts of low density polyethylene, as for the compounding quantity of resins other than low density polyethylene, and an elastomer, 10 mass parts or less are more preferable, and 5 mass parts or less are especially preferable. It can be set as the base resin which comprises a foamable molten resin composition by kneading resin and elastomer other than the said low density polyethylene together with a low density polyethylene.

(Antistatic agent)

In the manufacturing method of this invention, it is necessary to use a polymer type antistatic agent as an antistatic agent. This polymeric antistatic agent has a melting point difference of -10°C to +10°C with the low-density polyethylene, and a melt flow rate of 10 g/10 min or more.

If such a polymeric antistatic agent is used, it is possible to obtain a high-quality polyethylene-based resin extruded foam sheet exhibiting an excellent antistatic function in which the occurrence of small holes and through holes is prevented and suppressed even in continuous production over a medium to long term.

The exact reason for this is not certain at this time, but as will be described later, the polymer-type antistatic agent used in the present invention has a low melting point and a high melt flow rate. It is thought that this is because the precipitation of crystals, which is the cause of the occurrence of small holes or through holes, is prevented or suppressed.

The difference between the melting point of the polymer antistatic agent used in the present invention and the melting point of the low-density polyethylene ([melting point of low-density polyethylene]-[melting point of polymer-type antistatic agent]) is within the range of -10 ° C. to +10 ° C., Also in continuous operation, from the viewpoint of obtaining a high-quality product, the melting point difference is preferably -8°C to +8°C, more preferably -7°C to +7°C. Moreover, it is preferable that it is 125 degrees C or less, and, as for melting|fusing point of a polymer type antistatic agent, it is more preferable that it is 120 degrees C or less. On the other hand, the lower limit of melting|fusing point is about 100 degreeC.

In addition, melting|fusing point of a polymer type antistatic agent is calculated|required by the method similar to the said low density polyethylene.

For the same reason, the melt flow rate of the polymer type antistatic agent used in the present invention is 10 g/10 min or more, preferably 20 g/10 min or more, and more preferably 30 g/10 min or more. On the other hand, if the upper limit is about 100 g/10 minutes in the said range, since an antistatic agent is excellent in fluidity|liquidity and exhibits antistatic performance more effectively, it is preferable. The melt flow rate of the polymer-type antistatic agent is a value measured at a temperature of 190°C and a load of 2.16 kg according to JIS K7210-1:2014.

In addition, the ratio of the melt flow rate of the low-density polyethylene B to the melt flow rate of the polymer-type antistatic agent (melt flow rate of low-density polyethylene/melt flow rate of the polymer-type antistatic agent) is preferably 2 or less, and more preferably 1 or less. and 0.8 or less is more preferable. When the ratio is within the above range, the polymer-type antistatic agent is dispersed in a mesh or layer shape, and excellent antistatic performance can be more effectively exhibited. On the other hand, the lower limit of the ratio is preferably about 0.01 or more.

As a polymeric antistatic agent preferably used in the present invention, it consists of a block copolymer of polyether and polyolefin, and as a commercially available product, for example, Pelectron LMP manufactured by Sanyo Kasei Kogyo Co., Ltd. (melting point 114° C., melt flow rate 30 g) /10 min) and the like can be exemplified.

As a number average molecular weight of the polymer type antistatic agent used in this invention, 2,000 or more are preferable, More preferably, it is 2,000-100,000, More preferably, it is 5,000-80,000. In addition, the upper limit of the number average molecular weight of the said polymer type antistatic agent is about 500,000. By making the number average molecular weight of a high molecular weight antistatic agent into the said range, antistatic performance is expressed more stably, without being influenced by environments, such as humidity.

The said number average molecular weight is calculated|required using high temperature gel permeation chromatography. For example, if the polymer type antistatic agent has polyetheresteramide or polyether as its main component, use orthodichlorobenzene as a solvent to have a sample concentration of 3 mg/ml, and use polystyrene as a reference material at a column temperature of 135°C. It is a value measured under conditions. In addition, the type of the solvent and the column temperature are appropriately changed according to the type of the polymer type antistatic agent.

(Antistatic agent compounding amount)

The blending amount of the high molecular weight antistatic agent to the foam is preferably 2 to 30 parts by mass, more preferably 2 to 30 parts by mass, based on 100 parts by mass of the low-density polyethylene constituting the foam, from the viewpoint of having sufficient antistatic properties and obtaining a high-quality foam sheet. is 3 to 25 parts by mass, more preferably 5 to 20 parts by mass.

(Surface resistivity of foam sheet)

In the method of this invention, the surface resistivity of the surface of foam seat|seet can be made into 1x10< ⁷ >-1x10< ¹³ >(ohm) by adding the said polymer type antistatic agent. If the said surface resistivity is in the said range, foam seat|seet will show sufficient antistatic property. From the above viewpoint, the surface resistivity is preferably 5×10 ¹² Ω or less, and more preferably 1×10 ¹² Ω or less.

The surface resistivity in this invention is measured based on JISK6271:2008, after performing the state adjustment of the following test piece. Specifically, a test piece cut out from the foam sheet as the measurement object (length 100 mm × width 100 mm × thickness: measurement object thickness) is left to stand in an atmosphere of a temperature of 20° C. and a relative humidity of 30% for 36 hours to control the state of the test piece. Next, a voltage is applied to the test piece under conditions of an applied voltage of 500 V in an atmosphere of a temperature of 20°C and a relative humidity of 30%. Voltage application is started, and the surface resistivity is measured after 1 minute has elapsed.

(physical blowing agent)

In the method of the present invention, low-density polyethylene is supplied to an extruder, heated and kneaded to form a molten resin, and then a physical foaming agent is press-injected and further kneaded to form a foamable molten resin composition. The physical foaming agent may be an organic or inorganic physical foaming agent. Examples of the organic physical foaming agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane and isohexane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, and methyl chloride and ethyl chloride. fluorinated hydrocarbons such as chlorinated hydrocarbons, 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane, ethers such as dimethyl ether and methyl ethyl ether, and alcohols such as methanol and ethanol .

Examples of the inorganic physical foaming agent include oxygen, nitrogen, carbon dioxide, air, and water. It is possible to mix and use 2 or more types of these physical foaming agents. Of these, organic physical foaming agents are preferable from the viewpoint of foamability, and among them, those containing normal butane, isobutane, or mixtures thereof as a main component are particularly suitable.

The addition amount of the said physical foaming agent is adjusted according to the type and the apparent density of the target foam seat|seet. For example, when a foam sheet having an apparent density of 20 to 450 kg/m 3 is obtained by using a physical foaming agent such as a butane mixture of 30% by weight of isobutane and 70% by weight of normal butane as the physical foaming agent, the base material constituting the foamable molten resin composition It is 4-35 mass parts with respect to 100 mass parts of resin, Preferably it is 5-30 mass parts, More preferably, it is 6-25 mass parts.

(Bubble control agent)

In the method of this invention, a bubble control agent can be supplied to an extruder together with the said low density polyethylene. An inorganic powder or a chemical foaming agent can be used as a foam|bubble control agent. Examples of the inorganic powder include talc, zeolite, silica, calcium carbonate and the like.

As the chemical foaming agent, azodicarbonamide, hydrazodicarbonamide, azobisisobutyronitrile, sodium bicarbonate (sodium bicarbonate), sodium bicarbonate and sodium bicarbonate-citric acid, which is a mixture of citric acid or a monoalkali metal salt of citric acid such as sodium citrate A system chemical foaming agent etc. are illustrated. Among the above-mentioned chemical foaming agents, in order to obtain a foam sheet having a small cell diameter and excellent cushioning properties, a sodium bicarbonate-citric acid-based chemical foaming agent is preferable.

In particular, the use of a sodium bicarbonate-citric acid-based chemical foaming agent having an average particle diameter of 3 to 8 µm is preferable because the generation of through holes penetrating the foam sheet can be more effectively prevented. From this viewpoint, it is more preferable that the said average particle diameter is 4-7 micrometers. Moreover, it is preferable that it is 100 micrometers or less, and, as for the maximum particle diameter of a chemical foaming agent, it is more preferable that it is 80 micrometers or less. The average particle diameter means a median diameter (d50) measured by laser diffraction scattering type particle size distribution measurement. In addition, the maximum particle diameter of the chemical foaming agent is enlarged and observed with an optical microscope, etc. of a particle group of about 1-3 mg randomly sampled from the chemical foaming agent, and the major axis diameter of the particle with the longest major axis diameter among the particle group is determined by the chemical foaming agent. to the maximum particle diameter.

It is preferable that the addition amount of the said bubble regulator is 0.1-3 mass parts with respect to 100 mass parts of base resin which comprises a foamable molten resin composition, More preferably, it is 0.2-2 mass parts. It is preferable that the said addition amount is the said range, since it is easy to adjust a cell diameter to a desired range.

(Other additives)

In the method of the present invention, in addition to the above components, various additives may be added within a range that does not impair the effects of the present invention. As an additive, antioxidant, a heat stabilizer, a weathering agent, a ultraviolet absorber, a flame retardant, an inorganic filler, an antibacterial agent, a coloring agent etc. are illustrated, for example.

In the manufacturing method of the present invention, the reason why a foam sheet is obtained that prevents and suppresses the occurrence of small holes and through-holes, and also sufficiently exhibits antistatic performance, even in mid- to long-term continuous production, is not certain at the present time, but it is speculated as follows. are doing

Conventionally, in the polyethylene-based resin extruded foam sheet containing this type of antistatic agent, the antistatic agent is a polymer type having a melting point of about 135°C or higher, with a melting point difference of +20°C or higher with a low-density polyethylene as a base resin, as shown in later comparative examples. Antistatic agents are used. When such a conventional polymeric antistatic agent is used, since the temperature in the extruder is maintained at a high temperature of about 200° C. or higher as described above, the polymeric antistatic agent is completely melted in the foamable molten resin composition and is an unmelted polymeric antistatic agent. crystals do not precipitate.

However, this foamable molten resin composition is cooled to an appropriate foaming temperature when introduced into the annular die as described above, and specifically cooled to about 120°C (melting point of low-density polyethylene-based resin +10°C or less). Since the conventional polymeric antistatic agent is about 135°C, it is considered that a part of the polymeric antistatic agent melted in the extruder crystallizes and precipitates under such a cooling temperature.

And when the expandable molten resin composition containing this precipitated crystal|crystallization is extruded in an annular die, the precipitated crystal|crystallization will start to stay and adhere to the wall surface in an annular die. In the initial stage (several hours), the amount of residual crystals retained and adhered is small, so the effect on the surface of the foam is small, for example, in the case of continuous production for 2 days or continuous production over a long period of time of 7 days, the above The amount of retained crystals and the amount of adhesion of the remaining crystals increase dramatically, and eventually they come into contact with and fall on the surface of the foam, causing small holes or through holes in the foam sheet, making it impossible to obtain a high-quality foam seat.

On the other hand, in the present invention, as an antistatic agent, a polymeric antistatic agent having a melting point difference of -10 ° C. to +10 ° C. within the range of -10 ° C. to +10 ° C. and a melt flow rate of 10 g/10 min or more was used as an antistatic agent. , in the extruder, like the conventional polymeric antistatic agent, it is completely melted in the foamable molten resin composition, and the unmelted polymeric antistatic agent does not precipitate.

In addition, this foamable molten resin composition is cooled so that it may become foaming appropriate temperature as mentioned above, and specifically, it is cooled to about melting|fusing point +10 degreeC of low density polyethylene-type resin, for example, 120 degreeC. Here, since the polymer-type antistatic agent used in the present invention has a melting point that is within the range of -10°C to +10°C with a melting point difference from low-density polyethylene, it is completely melted in the annular die as well as in the extruder under this cooling temperature. It is thought that crystallization of unmelted polymeric antistatic agent is prevented and suppressed.

Therefore, in the present invention, despite the thin thickness, unlike the case of using the conventional polymer-type antistatic agent, even in a short period of several hours, as well as in continuous production over a medium-long period of several days, due to the polymer-type antistatic agent It is possible to obtain a high-quality foam sheet that has excellent strength and cushioning properties, while preventing and suppressing the occurrence of small holes and through-holes, which are thought to occur, and sufficiently exhibiting antistatic performance.

As described above, the production method of the foam sheet of the present invention is excellent in continuous productivity because the generation of small holes and through holes is prevented and suppressed not only for a short period of several hours, but also for a medium to long period of several days. Therefore, in manufacture of foam seat|seet of this invention, although it changes also with thickness and width direction length, it is 100 m or more at the time of manufacture, Preferably foam seat|seet can be wound up as roll shape of length 300 m or more.

On the other hand, in the conventional manufacturing method, there is a possibility that defects of small holes or through holes may occur in the foam sheet when continuous production over a medium to long period of several days is performed. After removing a part, since the operation|work which winds up foam seat|seet again in roll shape is needed, production efficiency will fall remarkably.

From the said viewpoint, in this invention, it is so preferable that there are few number of through-holes 1 mm or more in diameter which exist in the polyethylene-type resin extrusion foam seat|seet. Specifically, it is preferable that the number of 1 mm or more through-holes generated in one hour after the lapse of 2 or 7 days from the start of production is less than three.

(thickness of foam sheet)

The thickness (average thickness) of foam seat|seet obtained by the manufacturing method of this invention is 0.05 mm or more and 0.5 mm or less. From the viewpoint of cushioning properties and usability as interleaving paper, the lower limit of the average thickness is preferably 0.07 mm, more preferably 0.1 mm, still more preferably 0.15 mm. On the other hand, the upper limit of the average thickness is preferably 0.4 mm, more preferably 0.35 mm, still more preferably 0.3 mm.

The average thickness of foam seat|seet can be measured using the Yamabun Electric Co., Ltd. product offline thickness measuring machine TOF-4R etc. First, about the full width of foam seat|seet, thickness is measured at 1 cm intervals. The arithmetic mean thickness of the entire width is calculated based on the thickness of the foam sheet measured at intervals of 1 cm. In addition, the foam seat|seet used for the said measurement uses the thing adjusted for 24 hours or more under the conditions of temperature 23±5 degreeC, and 50% of relative humidity.

(apparent density of foam sheet)

The apparent density of the foam seat|seet obtained by the manufacturing method of this invention becomes like this. Preferably it exists in the range of 20-450 kg/m<3>. If the apparent density is within the above range, it is preferable because it is excellent in cushioning properties as a packaging material such as an interleaf paper. From this point of view, the apparent density is more preferably 30 to 300 kg/m 3 , and still more preferably 50 to 200 kg/m 3 .

In addition, the apparent density of foam seat|seet can be calculated|required by dividing the weight (g/m<2>) per unit area of foam seat|seet by the average thickness of foam seat|seet, and also unit conversion into [kg/m<3>].

In addition, it is preferable that the ratio of the diameter of the discharge port of the annular die to the diameter of the mandrel (blow-up ratio: the diameter of the mandrel/diameter of the lip of the annular die) is 2.2 to 3.8. If it is the said range, since there is no wave phenomenon in the circumferential direction accompanying foaming, and it is excellent in thickness precision, and since a favorable foam seat|seet is obtained without excessive flattening in the width direction of cells, it is preferable.

(foam sheet)

The novel polyethylene-based resin extruded foam sheet according to the present invention is of high quality in which the occurrence of small holes and through-holes is prevented and suppressed, and exhibits sufficient antistatic performance, despite the extremely thin thickness as described above.

Therefore, the novel polyethylene-based resin extruded foam sheet of the present invention is a field in which an antistatic function or the like is strongly required, particularly when conveying or packing a thin glass plate for an image display device such as a liquid crystal display, a plasma display, or an electroluminescence display. It is widely and very useful as a slip sheet for glass plates to prevent damage to. Moreover, it is possible to manufacture continuously over a mid- to long-term, and it is a foam seat|seet with very high production efficiency industrially.

Example

Hereinafter, the present invention will be described in more detail in Examples and Comparative Examples. However, the present invention is not limited to the Examples.

[Low Density Polyethylene]

Table 1 shows the low-density polyethylene used in Examples and Comparative Examples.

Table 2 shows the antistatic agents used in Examples and Comparative Examples.

[Bubble Adjuster]

The foam control agent used in Examples and Comparative Examples was a mixture of sodium hydrogencarbonate and citrate-sodium in a weight ratio of 1:1, and a chemical foaming agent having an average particle diameter (d50) of 6 µm and a maximum particle diameter of 30 µm was used.

[Device]

As a foam seat|seet manufacturing apparatus, the 1st extruder (tandem extruder) in which the extruder with a barrel inner diameter of 115 mm for foaming layer formation, and the extruder with a barrel inner diameter of 150 mm were connected was used downstream. In addition, the temperature control of the lip part mold of a die|dye was performed for each divided part by dividing the lip part mold into 8 parts.

Examples 1 to 3, Comparative Examples 1 to 5

The low-density polyethylene-type resin shown in Table 3, the antistatic agent, and the bubble control agent were supplied to the raw material inlet of the extruder by the formulation shown in Table 3, and it was heat-kneaded and it was set as the resin melt adjusted to 200 degreeC. As a physical foaming agent, mixed butane of 70 mass % of normal butane and 30 mass % of isobutane as a physical foaming agent in the resin melt is press-fitted so as to have a compounding amount shown in Table 3 with respect to 100 parts by mass of a polyethylene-based resin, heat-kneaded, and then cooled and shown in Table 3 It was set as the foamable molten resin composition of the indicated resin temperature, and the said foamable molten resin composition was introduce|transduced into the annular die for extrusion.

Then, it extruded in the air through the lip|rip of the die|dye, and the cylindrical foam of a single-layer structure containing an antistatic agent was formed. The cylindrical foam was taken with a mandrel at the speed shown in Table 3 while expanding the diameter at the blow-up ratio shown in Table 3, and cut along the extrusion direction and wound on a roll of a predetermined length to obtain a single-layer foam sheet containing an antistatic agent. .

In addition, the compounding quantity of the antistatic agent, a bubble control agent, and a physical foaming agent in Table 3 shows mass parts of an antistatic agent, a bubble control agent, and a physical foaming agent with respect to 100 mass parts of resin which comprises a foaming layer.

The physical properties of the foam seat|seet obtained by the Example and the comparative example are shown in Table 4.

(Result of review in Table 4)

From Table 4, it can be seen that the foam sheet obtained in Examples 1 to 3 used a unique high-molecular-type antistatic agent having a melting point difference of +7°C with low-density polyethylene (Daebang 1: Melting point 114°C), so 48 hours (2 days) In the medium-term continuous production of , as well as in the long-term continuous production of 168 hours (7 days), the generation of through-holes on the surface is prevented and suppressed, and the antistatic performance is sufficiently exhibited. Therefore, it turns out that the foam seat|seet of this invention has antistatic performance, and it is stable and it is an industrially very valuable foam seat|seet which can be mass-produced.

On the other hand, in the foam sheets obtained in Comparative Examples 1 to 2, polymeric antistatic agents (Daebang 2, Daebang 3) having a high melting point (135° C.) with a melting point difference of 28° C. with low-density polyethylene were used, but 48 hours ( In the medium-term continuous production of 2 days), the occurrence of through-holes was already seen, and in the long-term continuous production of 168 hours (7 days), the occurrence of through-holes was more remarkable, indicating that the production efficiency was low. there is.

The foam sheet obtained in Comparative Example 3 uses a high-molecular antistatic agent (Daebang 4: melting point 92° C.) having a melting point difference of -15°C from that of low-density polyethylene. is obtained, but sufficient antistatic performance is not expressed. Then, as in Comparative Example 4, when the compounding amount was increased in order to sufficiently express the antistatic ability, it was difficult to stably manufacture the foam sheet because there was a large amount of Daebang 4 having a low melt flow rate this time.

The foam seat|seet obtained in Comparative Example 5 contrasts with Example 2, and it turns out that the antistatic agent with a large melting|fusing point difference with a low-density polyethylene-type resin is not suitable for long-term continuous production.

In addition, in Table 4, various physical properties were measured as follows.

(thickness of foam sheet)

The average thickness of foam seat|seet was measured using the Yamabun Electric Co., Ltd. product offline thickness meter TOF-4R. First, about the foam seat|seet full width, thickness was measured at 1 cm intervals. The arithmetic mean thickness of the total width was calculated|required based on the foam seat|seet thickness measured at this 1-cm space|interval. In addition, the foam seat|seet used for the said measurement used what adjusted the state for 48 hours under the conditions of temperature 23±5 degreeC, and 50% of relative humidity.

(Basic weight of foam sheet)

The basis weight of the foam sheet is obtained by cutting a rectangular test piece having a width of 250 mm over the entire width of the foam sheet, dividing the weight (g) of the test piece by the area of the test piece (sheet width (mm) × 250 mm), 1 It was converted into the weight (g) of foam seat|seet per m<2>, and this was made into the basis weight of foam seat|seet (g/m<2>).

(apparent density of foam sheet)

The apparent density of foam seat|seet was calculated|required by dividing by the average thickness of foam seat|seet calculated|required by the above by the basis weight (g/m<2>) of foam seat|seet calculated|required by the said method.

(Occurrence of through holes, etc.)

(short-term)

At the time of foam seat|seet manufacture, using the fault detector, the surface of foam seat|seet was observed for 1 hour after 48 hours from a manufacture start, and the following reference|standard evaluated.

good: After 48 hours, the number of through holes of 1 mm or more generated in 1 hour is less than 3

poor: After 48 hours, the number of through holes of 1 mm or more generated in 1 hour is 3 or more but less than 5

bad: After 48 hours, the number of 1 mm or more through-holes generated in 1 hour is 5 or more

(long time)

At the time of foam seat|seet manufacture, using the fault detector, the surface of foam seat|seet was observed 1 hour after 168 hours from a manufacture start, and the following reference|standard evaluated.

good: After 168 hours, the number of through holes of 1 mm or more generated in 1 hour is less than 3

poor: After 168 hours, the number of through holes of 1 mm or more generated in 1 hour is 3 or more but less than 5

bad: After 168 hours, the number of 1 mm or more through-holes generated in 1 hour is 5 or more

-: Unable to evaluate (cannot form foam sheet)

(Surface resistivity)

The surface resistivity was measured based on JIS K6271:2008, after performing state adjustment of the following test piece. Specifically, five test pieces (length 100 mm × width 100 mm × thickness: thickness of the measurement object) randomly cut from the foam sheet as the measurement object were left for 36 hours in an atmosphere of a temperature of 23° C. and a relative humidity of 50%. The state of the test piece adjustment was made. Next, a voltage was applied to the test piece under the condition of an applied voltage of 500 V in an atmosphere of a temperature of 23°C and a relative humidity of 50% on both surfaces of each test piece. The surface resistivity of 1 minute after the voltage application was started was measured, and those arithmetic mean values (5 specimens x both surfaces [n=10]) were made into the surface resistivity of laminated foam seat|seet.

Claims (7)

A method for producing a polyethylene-based resin extruded foam sheet by extruding and foaming a foamable molten resin composition containing low-density polyethylene, a physical foaming agent and an antistatic agent, the method comprising:
The thickness of the foam sheet is in the range of 0.05 to 0.5 mm, the melt flow rate of the low-density polyethylene is 15 g/10 min or more, and the melting point difference with the low-density polyethylene as an antistatic agent has a melting point in the range of -10 to +10 ° C., Further, a method for producing a polyethylene-based resin extruded foam sheet using a polymer-type antistatic agent having a melt flow rate of 10 g/10 min or more. The method of claim 1,
The melting point of the polymer-type antistatic agent is a method for producing a polyethylene-based resin extruded foam sheet, characterized in that 120 ℃ or less. 3. The method of claim 1 or 2,
The ratio of the melt flow rate of the low-density polyethylene to the melt flow rate of the polymer-type antistatic agent (melt flow rate of low-density polyethylene/melt flow rate of the polymer-type antistatic agent) is 2 or less Production of a polyethylene-based resin extruded foam sheet, characterized in that Way. 3. The method of claim 1 or 2,
With respect to 100 parts by mass of the low-density polyethylene, a method for producing a polyethylene-based resin extruded foam sheet, wherein the polymer-type antistatic agent is blended within the range of 3 to 25 parts by mass. A polyethylene-based resin extruded foam sheet containing an antistatic agent, wherein the base resin is low-density polyethylene,
The thickness is in the range of 0.05 mm to 0.5 mm, the apparent density is in the range of 20 to 450 kg/m3, the melt flow rate of the low density polyethylene is 15 g/10 min or more, and the melting point difference of the antistatic agent with the low density polyethylene is -10 ° C. Polyethylene-based resin extruded foam sheet, characterized in that it is a polymer-type antistatic agent having a melting point in the range of ~+10°C and a melt flow rate of 10 g/10 min or more. The slip sheet for glass plates which consists of the polyethylene-type resin extrusion foam seat|seet of Claim 5. 3. The method of claim 1 or 2,
The said foam seat|seet is a roll body formed by winding up, The manufacturing method of the polyethylene-type resin extrusion foam seat|seet characterized by the above-mentioned.