JP7020979B2 - Manufacturing method of polyethylene resin foam sheet and polyethylene resin foam sheet and its roll - Google Patents

Description

The present invention relates to a method for producing a polyethylene-based resin foamed sheet, a polyethylene-based resin foamed sheet, and a roll thereof.

The polyethylene-based resin foam sheet is used in various fields as a sheet paper for plate-shaped materials, a packing material, a cushioning material, and the like in which the cushioning property is utilized.

As shown in Patent Document 1, a polyethylene-based resin foam sheet is generally produced by extruding a resin melt containing an aliphatic hydrocarbon such as butane as a physical foaming agent from an extruder and foaming it. .. For example, a polyethylene-based resin foam sheet can be obtained by taking out a tubular foam formed by extruding a resin melt from an extruder equipped with an annular die.

The polyethylene-based resin foam sheet is generally stored and shipped as a roll-shaped material wound into a roll shape. In recent years, polyethylene-based resin foam sheets are increasingly shipped in the form of rolls as export products.

In addition, in Patent Document 2, nonflammable hydrochlorofluoroolefin (HCFO) is used as a physical foaming agent for extruded polystyrene resin, and the solubility and diffusion coefficient of gas in polystyrene are obtained. We are evaluating the characteristics.

Japanese Patent Application Laid-Open No. 2015-074671 Special Table 2010-522818

For example, when a polyethylene-based resin foam sheet is used as a paper sheet for plate-like materials, it is required to have a cushioning property and a stiffness that is resistant to sagging. In order to satisfy such physical properties, a polyethylene-based resin foam sheet having a closed cell structure is required.

Normally, such a polyethylene-based resin foamed sheet is manufactured using butane, which is a flammable gas, as an aliphatic hydrocarbon. Therefore, the polyethylene-based resin foamed sheet immediately after production was used as a physical foaming agent. Butane remains.

The physical foaming agent remaining on the polyethylene-based resin foam sheet immediately after production gradually dissipates to the outside over time. On the other hand, the surrounding gas (generally air) gradually flows into the foam sheet. At this time, since the foamed sheet shrinks due to the dissipation of the physical foaming agent, a curing step of the foamed sheet is required in order to recover the thickness of the shrunk foamed sheet. Therefore, from the viewpoint of enabling the foamed sheet to be shipped at an early stage, there is a demand for a foamed sheet having a quick recovery in thickness and a short time required for the curing process.

On the other hand, when the polyethylene-based resin foamed sheet is housed in a closed space such as a container for storage or transportation, if butane remains on the polyethylene-based resin foamed sheet, the butane dissipates from the polyethylene-based resin foamed sheet. Accumulates in the closed space, and the butane concentration in the closed space increases. In particular, when the polyethylene-based resin foam sheet shipped as an export product is transported by ship for a long time, the butane concentration in the closed space may reach the explosive limit concentration during transportation depending on the amount of the product in the closed container. There was a risk of reaching.

As a method of reducing the butane remaining in the polyethylene-based resin foam sheet, a curing step of dissipating the butane remaining in the polyethylene-based resin foam sheet is performed for a long period of time before the polyethylene-based resin foam sheet is housed in the closed space. It is conceivable to sufficiently carry out the method or to separately carry out a heat treatment for promoting the dissipation of butane on the polyethylene-based resin foam sheet.

However, when the curing process is carried out for a long period of time, the period until the polyethylene-based resin foam sheet is shipped becomes long, and it is necessary to secure a space for curing, so that there is a problem that productivity deteriorates. In addition, even after long-term curing, there is a risk that the residual amount of butane cannot be sufficiently reduced. Further, when the heat treatment is performed, there is a problem that the productivity is deteriorated because the manufacturing process is increased.

Further, as an alternative to butane, it is conceivable to use general carbon dioxide or the like as a nonflammable physical foaming agent. However, when a polyethylene-based resin foamed sheet is manufactured using a conventionally used nonflammable foaming agent such as carbon dioxide, the extruded foamability from the annular die is lowered, and the surface texture of the foam is deteriorated or foam is broken. Is likely to occur. In particular, this tendency becomes remarkable when trying to obtain a thin foam sheet.

Patent Document 2 evaluates the characteristics of a polystyrene resin foam when HCFO is used as a physical foaming agent, but it is applied to a sheet-shaped foam extruded from an annular die and blown up, particularly a polyethylene-based resin foam sheet. The physical properties of the case have not been clarified.

The present invention has been made in view of the above circumstances, and is a polyethylene-based resin foam produced by using a flammable physical foaming agent under the same manufacturing conditions as when a flammable physical foaming agent is used. A method for producing a polyethylene-based resin foamed sheet and polyethylene, which have the same physical properties as the sheet and can shorten or omit the step of reducing the residual amount of the flammable physical foaming agent and the step of recovering the thickness of the foamed sheet. An object of the present invention is to provide a foamed resin sheet and a roll thereof.

In order to solve the above problems, the method for producing a polyethylene-based resin foam sheet of the present invention has a tubular shape formed by extruding a polyethylene-based resin melt obtained by kneading a polyethylene-based resin and a physical foaming agent from an annular die. By taking the foam of, the average thickness is 2 mm or less, the basis weight is 10 g / m ² or more and 100 g / m ² or less, the closed cell ratio is 5% or more and 85% or less, and the average cell diameter in the thickness direction with respect to the average cell diameter in the extrusion direction. A method for producing a polyethylene-based resin foamed sheet having a ratio of 0.1 or more and 0.6 or less, and a ratio of an average cell diameter in the thickness direction of 0.2 or more and 0.8 or less to an average cell diameter in the width direction, which is physically foamed. As an agent, a physical foaming agent containing 1-chloro-3,3,3-trifluoropropene is used, and the blending amount of 1-chloro-3,3,3-trifluoropropene is 0.5 mol per 1 kg of polyethylene resin. It is characterized in that it is 3.0 mol or less.

The polyethylene-based resin foam sheet of the present invention is obtained by extruding and foaming a polyethylene-based resin melt obtained by kneading a polyethylene-based resin and a physical foaming agent containing 1-chloro-3,3,3-trifluoropropene. , Average thickness 2 mm or less, Basis weight 10 g / m ² or more and 100 g / m ² or less, closed cell ratio 5% or more and 85% or less, ratio of average cell diameter in the thickness direction to average cell diameter in the extrusion direction 0.1 or more 0. A polyethylene-based resin foamed sheet having a ratio of 6 or less, the ratio of the average cell diameter in the thickness direction to the average cell diameter in the width direction, 0.2 or more and 0.8 or less.

The roll-shaped material of the polyethylene-based resin foamed sheet of the present invention is the polyethylene-based resin foamed sheet wound in a roll shape.

In the present invention, nonflammable 1-chloro-3,3,3-trifluoropropene is used as a physical foaming agent. Therefore, according to the present invention, it is possible to shorten or omit the curing and heat treatment steps for reducing the residual amount of the flammable physical foaming agent in the foamed sheet. In addition, since the thickness of the foamed sheet immediately after production is quickly recovered, the curing process can be shortened.

In addition, according to the present invention, a polyethylene-based resin having the same good physical properties as a foamed sheet manufactured using a flammable physical foaming agent under the same manufacturing conditions as when a flammable physical foaming agent is used. A foam sheet can be obtained.

It is a schematic diagram which shows an example of the extruder used in this invention.

Hereinafter, the present invention will be described in detail.

In the present specification, the term "polyethylene resin foam sheet" refers to a tubular foam formed by extruding a polyethylene resin melt obtained by kneading a polyethylene resin and a physical foaming agent from an annular die. It mainly shows a foamed sheet that has recovered to a constant thickness after being picked up. For the average thickness, basis weight, closed cell ratio, average cell diameter, apparent density, foaming ratio, etc., the value of the foamed sheet whose thickness has been restored is referred to. However, the present invention is not necessarily limited to this, and a tubular foam immediately after extrusion and a sheet-like material whose thickness is restored after being picked up may be referred to as "polyethylene resin foam sheet".
(Manufacturing method of polyethylene resin foam sheet)
In the method for producing a polyethylene-based resin foam sheet of the present invention, 1-chloro-3,3,3-trifluoropropene is used as at least a part of the physical foaming agent in producing the polyethylene-based resin foam sheet as described above. Used.

Therefore, it is possible to shorten or omit the curing step for reducing the residual amount of flammable butane or other aliphatic hydrocarbons, which is necessary before storing in a closed container, especially when exporting. Moreover, since the thickness of the foamed sheet is restored at an early stage, the curing process can be shortened. Further, the obtained polyethylene-based resin foamed sheet exhibits the same physical characteristics as the polyethylene-based resin foamed sheet formed by using an aliphatic hydrocarbon such as butane as a physical foaming agent in the same extrusion production method. Therefore, according to the present invention, it is possible to promptly ship and export a polyethylene-based resin foam sheet having good physical properties.

The polyethylene-based resin foam sheet, which is the target of the production method of the present invention, takes up the foam at a take-up speed faster than the discharge rate of the resin melt at the time of extrusion, and stretches the foam to obtain a thin foam. It is a sheet. By picking up the foam at a pick-up speed faster than the discharge speed at the time of extrusion, the bubbles in the foam sheet become a flat bubble shape long in the extrusion direction. In addition, at the time of extrusion, by expanding the diameter by blow-up, that is, a tubular cooling tube (hereinafter, also referred to as mandrel) having a diameter larger than that of the annular die lip portion, the bubbles are flattened and the bubble shape becomes long in the width direction of the foamed sheet. Become.

The polyethylene-based resin used in the present invention has an ethylene component of 50 mol% or more, preferably 60 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more.

As the polyethylene-based resin, for example, any polyethylene-based resin usually used for a polyethylene-based resin foam can be used without particular limitation. Specifically, low density polyethylene, ultra low density polyethylene, linear low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer And so on. These may be used alone or in combination of two or more.

Among these, it is preferable to use low-density polyethylene from the viewpoint that a foamed sheet having good extrusion foamability at the time of manufacturing a foamed sheet and having good cushioning property and elasticity can be stably obtained. Generally, low-density polyethylene refers to a polyethylene-based resin having a density of 0.91 g / cm ³ or more and less than 0.93 g / cm ³ .

When low density polyethylene is used, its MFR (melt flow rate) is preferably 2 g / 10 min or more and 20 g / 10 min or less, and more preferably 4 g / 10 min or more and 15 g / 10 min or less.

Here, the MFR is measured based on JIS K 7210-1: 2014 (test temperature: 190 ° C., load 2.16 kg). When two or more types of low-density polyethylene are used in combination, the MFR of the mixture thereof is preferably within the above range.

When the MFR is within this range, the flowability of the polyethylene-based resin is high, and the foam is easily stretched at the time of picking up. Therefore, it is possible to stably obtain a foamed sheet having a thin thickness and a good appearance.

When low-density polyethylene is used, the melt tension at 190 ° C. is preferably 15 mN or more and 300 mN or less. When the melt tension is within this range, a foamed sheet having a low basis weight, a high closed cell ratio, and a good appearance can be stably obtained. Considering this point, the melting tension is more preferably 30 mN or more, and further preferably 40 mN or more. Further, the melting tension is more preferably 250 mN or less.

The melt tension of the polyethylene resin at 190 ° C. (hereinafter, also referred to as melt tension or MT) can be measured by, for example, a melt tension tester type II manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, using a melt tension tester having a nozzle with a nozzle diameter of 2.095 mm and a length of 8 mm, the resin is extruded from the nozzle in a string shape under the conditions of a resin temperature of 190 ° C. and an extrusion piston speed of 10 mm / min. This string-shaped object is hung on a tension detection pulley having a diameter of 45 mm, and then wound with a winding roll having a diameter of 50 mm at a winding speed of 15.7 m / min.

The specific method for obtaining the melt tension is as follows. The melt tension of the string-like material detected by the detector connected to the tension detection pulley by winding at a winding speed of 15.7 m / min is measured over time, and the vertical axis is MT (mN). ) Is shown in a chart with time (seconds) on the horizontal axis, and a graph with amplitude is obtained. Next, the median (X) of the amplitude of the stable portion of the amplitude is taken. In the present invention, this value (X) is taken as the melt tension. In the measurement, the rarely generated specific amplitude shall be ignored.

However, when the string-shaped object hung on the tension detection pulley is cut to a winding speed of 15.7 m / min, the winding speed R when the string-shaped object is cut is obtained. Next, at a constant winding speed of R × 0.7, the median amplitude (X) is defined as the melt tension from the graph obtained in the same manner as described above.

In the present invention, 1-chloro-3,3,3-trifluoropropene (HCFO1233zd) is used as the physical foaming agent.

Substantially only 1-chloro-3,3,3-trifluoropropene may be used as the physical foaming agent, or 1-chloro-3,3,3-tri tri. Other physical foaming agents may be used in addition to fluoropropene. Other effervescent agents include inorganic physical effervescent agents such as carbon dioxide, nitrogen, air and water, and aliphatic hydrocarbons having 3 to 6 carbon atoms such as propane, normal butane, isobutane, normal pentane, isopentan, isohexane and cyclohexane. Hydrocarbons having 1 or more and 4 or less carbon atoms such as hydrogen, methyl chloride, ethyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, and carbon atoms of methanol, ethanol, propanol, butanol, etc. Examples thereof include organic physical effervescent agents such as aliphatic alcohols having 1 or more and 4 or less, dimethyl ethers, diethyl ethers, dipropyl ethers and the like, and aliphatic ethers having 2 to 8 carbon atoms. These may be used alone or in combination of two or more.

By using 1-chloro-3,3,3-trifluoropropene for at least a part of the physical foaming agent used, it is possible to omit or shorten the curing process for the purpose of dissipating the flammable foaming agent. At the same time, a sheet-like foam having good physical properties can be obtained. Further, the thickness of the foamed sheet is quickly recovered immediately after production, and the curing period for recovering the thickness of the foamed sheet can be shortened.

From the viewpoint that a foamed sheet having a good appearance can be obtained, and when the obtained polyethylene-based resin foamed sheet is housed in a closed container, it is possible to completely avoid the accumulation of flammable gas derived from the foamed sheet in the closed container. Therefore, it is preferable to use substantially only 1-chloro-3,3,3-trifluoropropene as the physical effervescent agent.

As other physical foaming agents, aliphatic hydrocarbons having 3 or more and 6 or less carbon atoms, aliphatic alcohols having 1 or more and 4 or less carbon atoms, and 2 or more and 8 or less carbon atoms are used as long as the effects of the present invention are not impaired. When a flammable gas (flammable physical foaming agent) such as an aliphatic ether is used, it remains in the polyethylene-based resin foam sheet immediately after production from the viewpoint of omitting or shortening the curing step for dissipating the flammable gas. It is preferable to add the flammable gas so that the content of the flammable gas is 0.05% by mass or less. In particular, when a saturated hydrocarbon having 3 or more and 6 or less carbon atoms is used, the blending amount thereof is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and further preferably 1 part by mass or less with respect to 100 parts by mass of the polyethylene resin. preferable.

From the above viewpoint, it is most preferable not to use a flammable gas as the physical foaming agent.

In the production method of the present invention, the blending amount of 1-chloro-3,3,3-trifluoropropene with respect to the polyethylene resin is 0.5 mol or more and 3.0 mol or less per 1 kg of the polyethylene resin. Within this range, extrusion foaming can be stably performed. From this viewpoint, the blending amount of 1-chloro-3,3,3-trifluoropropene with respect to the polyethylene resin is preferably 1.0 mol or more and 2.5 mol or less.

From the viewpoint of easily obtaining a good foamed sheet, the blending amount of the physical foaming agent with respect to the polyethylene resin is preferably 0.5 mol or more and 3.0 mol or less per 1 kg of the polyethylene resin, and 1.0 mol or more. It is more preferably 5 mol or less.

A thin foam sheet using carbon dioxide or the like, which has been conventionally used as a nonflammable physical foaming agent, to increase the take-up speed (for example, when adjusted to the range of 5 m / min or more and 75 m / min or less). When trying to obtain the above, the resin extruded from the annular die cannot withstand the take-up, and the foamed sheet tends to break. Further, even when the foam could be formed into a sheet shape, the surface of the foam tended to have poor surface texture due to uneven elongation or unevenness due to bubble rupture. This is considered to be one of the reasons that carbon dioxide has a low plasticizing effect on the thermoplastic resin, and therefore, when carbon dioxide is used as a physical foaming agent, the ductility of the resin extruded from the annular die is not sufficient. Be done. On the other hand, by containing 1-chloro-3,3,3-trifluoropropene in the above-mentioned blending amount in the physical foaming agent, even when a thin foam sheet is to be obtained, the elongation is uneven. The generation of bubbles and the deterioration of surface properties are suppressed.

From the viewpoint of obtaining a foamed sheet having good surface texture, apparent density and closed cell ratio, the blending ratio of 1-chloro-3,3,3-trifluoropropene in the physical foaming agent is preferably 50 mol% or more. , 1-Chloro-3,3,3-trifluoropropene is more preferably 60 mol% or more, and 1-chloro-3,3,3-trifluoropropene is 70 mol% or more. It is more preferable that the blending ratio of 1-chloro-3,3,3-trifluoropropene is 90 mol% or more, and the blending ratio of 1-chloro-3,3,3-trifluoropropene is 100 mol. % Is particularly preferable (however, in each case, the total mixing ratio of 1-chloro-3,3,3-trifluoropropene and other physical foaming agents is 100 mol%).

In the method for producing a polyethylene-based resin foam sheet of the present invention, in addition to the polyethylene-based resin and the physical foaming agent described above, one kind of other material necessary for extrusion molding is used within the range not impairing the effect of the present invention. Alternatively, two or more types can be used.

Examples of other materials include bubble regulators, antioxidants, heat stabilizers, weather resistant agents, ultraviolet absorbers, flame retardants, inorganic fillers, antibacterial agents, colorants, antistatic agents and the like.

As the bubble adjusting agent, either an inorganic type or an organic type can be used. Examples of the inorganic bubble adjusting agent include boric acid metal salts such as zinc borate, magnesium borate, and borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate, and the like. ..

Examples of the organic bubble adjusting agent include sodium 2,2-methylenebis (4,6-tert-butylphenyl) phosphate, sodium benzoate, calcium benzoate, aluminum benzoate, sodium stearate and the like. .. Further, a combination of citric acid and sodium bicarbonate, an alkali salt of citric acid and sodium bicarbonate and the like can also be used. Two or more of these bubble adjusting agents can be mixed and used.

The amount of the bubble adjusting agent added can be appropriately set according to the bubbles to be formed on the polyethylene-based resin foam sheet, but is usually 0.05 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the polyethylene-based resin. It is preferably in the range of 0.2 parts by mass or more and 5 parts by mass or less.

The average thickness of the polyethylene-based resin foam sheet obtained by the production method of the present invention is 2 mm or less. The average thickness can be, for example, 1 mm or less, or 0.5 mm or less, depending on the object to be packaged and the purpose of use thereof, such as for a large thin glass plate. The lower limit of the average thickness is not particularly limited, but 0.1 mm or more is preferable from the viewpoint of cushioning property against the packaged object and surface protection.

The average thickness of the polyethylene-based resin foam sheet in the present invention is a thickness measured at equal intervals along the width direction over the entire width at three or more locations randomly selected along the extrusion direction with respect to the foam sheet ( It can be obtained by calculating the average thickness of the three or more locations by the arithmetic mean of (mm) and arithmetically averaging the calculated values of the average thickness of the three or more locations.

The average thickness of the polyethylene-based resin foam sheet can be adjusted mainly by the take-up speed at the time of extrusion, the discharge amount, the blow-up ratio (diameter expansion ratio), and the like. When producing a polyethylene-based resin foam sheet having an average thickness in the above range, the take-up speed of the tubular foam extruded from the extruder is preferably 5 m / min or more and 75 m / min or less, and the average thickness is particularly 1. When adjusting to 0 mm or less, the take-up speed is preferably 10 m / min or more and 75 m / min or less, and more preferably 15 m / min or more and 60 m / min or less.

The basis weight of the polyethylene-based resin foam sheet obtained by the production method of the present invention is 10 g / m ² or more and 100 g / m ² or less. When the basis weight is within this range, it is suitable for obtaining a lightweight polyethylene-based resin foam sheet while maintaining cushioning property and elasticity.

The closed cell ratio of the polyethylene-based resin foam sheet obtained by the production method of the present invention is 5% or more and 85% or less. When the closed cell ratio is within this range, a polyethylene-based resin foam sheet having good physical properties such as cushioning property and elasticity can be obtained even if the bubbles have a flat shape.

Further, from the viewpoint of excellent balance between thickness recovery and cushioning property, the upper limit of the closed cell ratio is preferably 80%, more preferably 70%.

The closed cell ratio of the foamed sheet can be specified, for example, as follows. A test piece is cut out from the foam sheet, the true volume Vx of the test piece is measured according to procedure C of ASTM-D2856-70, and the closed cell ratio S (%) is calculated by the following formula (1). As the measuring device, for example, an air comparison type hydrometer 930 type manufactured by Toshiba Beckman Co., Ltd. can be used.

However, in the above formula (1), Vx is the true volume (cm ³ ) of the cut sample obtained by the above measurement (the volume of the resin composition constituting the test piece and the total cell volume of the closed cell portion of the test piece). ), Va is the apparent volume of the test piece calculated from the external dimensions of the test piece (cm ³ ), W is the total weight of the test piece (g), and ρ is extrusion foaming. The density (g / cm ³ ) of the resin composition constituting the sheet is shown.

As a test piece for measuring the closed cell ratio, a test piece adjusted so that the apparent volume is approximately 20 cm ³ by stacking a plurality of foam sheets can be used.

In the polyethylene-based resin foam sheet obtained by the production method of the present invention, the ratio (VD / MD) of the average cell diameter in the thickness direction (VD) to the average cell diameter in the extrusion direction (MD) is 0.1 or more and 0.6. It is as follows. The ratio (VD / TD) of the average bubble diameter in the thickness direction (VD) to the average bubble diameter in the width direction (TD) is 0.2 or more and 0.8 or less. When these ratios are within the above range, when used as a sheet paper for plate-shaped materials, the elasticity is secured and the handling is good, the cushioning property is secured, and it is suitable for the protection of the packaged object.

From the viewpoint of stably obtaining a foamed sheet having good cushioning property and elasticity, the average cell diameter in the extrusion direction (MD) of the polyethylene-based resin foamed sheet is preferably about 300 μm or more and 1000 μm or less. Further, the average bubble diameter in the width direction (TD) is preferably about 100 μm or more and 600 μm or less. Further, the average bubble diameter in the thickness direction (VD) is preferably about 80 μm or more and 500 μm or less.

As will be described later, the average cell diameter is obtained by drawing a line segment parallel to each direction in a cross-sectional photograph of a vertical cross section in each direction and obtaining the number of bubbles intersecting the line segment with respect to the length of the line segment. calculate.

The fact that these ratios are less than 1.0 indicates that the bubbles have a flat shape. Generally, when a polyethylene-based resin foam sheet is picked up at a relatively high pick-up speed to obtain a thin-thickness polyethylene-based resin foam sheet, bubbles tend to be flattened. The ratio of these average bubble diameters (VD / MD and VD / TD) can be adjusted within the range according to the take-up speed, the discharge amount, the blow-up ratio (diameter expansion ratio), and the like.

For example, by increasing the take-up speed, the ratio of the average cell diameter in the thickness direction (VD / MD) to the average cell diameter in the extrusion direction can be adjusted to 0.6 or less. Further, by increasing the blow-up ratio, the ratio of the average cell diameter in the thickness direction (VD / TD) to the average cell diameter in the width direction can be adjusted to 0.8 or less.

The blow-up ratio is preferably 2.0 or more and 4.0 or less, and 2.1 or more and 3.8 or less, from the viewpoint that the generation of corrugated can be suppressed and a foamed sheet having a good appearance can be easily obtained. Is more preferable, and 2.2 or more and 3.5 or less is further preferable.

The blow-up ratio (diameter expansion ratio) is the ratio of the diameter of the mandrel to the diameter of the annular die lip portion (diameter of the mandrel / diameter of the annular die lip portion). By setting the blow-up ratio small, it is possible to adjust the extruded foam sheet so that the bubble diameter in the thickness direction is larger than the bubble diameter in the width direction. On the other hand, by setting a large blow-up ratio, it is possible to adjust the extruded foam sheet so that the bubble diameter in the thickness direction becomes smaller than the bubble diameter in the width direction.

The apparent density of the polyethylene-based resin foam sheet obtained by the production method of the present invention is preferably 20 kg / m ³ or more and 300 kg / m ³ or less, and more preferably 35 kg / m ³ or more and 250 kg / m ³ or less. When the apparent density is within this range, a lightweight polyethylene-based resin foam sheet can be obtained while maintaining cushioning property and elasticity. The foamed sheet of the present invention is suitable as a paper sheet for plate-shaped materials because it is lightweight, thin, and has good cushioning properties and firmness.

For the apparent density (kg / m ³ ), the mass (kg) of a plurality of test pieces cut out from a foam sheet and the volume (m ³ ) obtained from the appearance dimensions are measured, and the mass (kg) is the volume. It can be obtained by dividing by (m ³ ) to obtain the apparent density (kg / m ³ ) of each test piece, and arithmetically averaging the obtained values.

In the present invention, when producing a polyethylene-based resin foam sheet, a tubular foam formed by extruding a polyethylene-based resin melt obtained by kneading a polyethylene-based resin and a physical foaming agent from an annular die is taken.

For example, a polyethylene-based resin, a bubble regulator, and an additive, if necessary, are supplied to an extruder and heated and melted to form a resin melt, and then a physical foaming agent is press-fitted into the resin melt and further kneaded. To obtain a foamable resin melt. The foamable resin melt is adjusted to a temperature at which it can be foamed (resin temperature) in the extruder, introduced into an annular die, extruded from the lip portion at the tip of the die into the atmosphere in the low pressure region, and the foamable resin melt is foamed. Use a tubular foam. A foamed sheet can be obtained by cutting open the tubular foam along the extrusion direction while taking it up while expanding the diameter (blow-up) with a mandrel.

FIG. 1 is a schematic view showing an example of an extruder used in the present invention. First, the polyethylene-based resin is supplied to the extruder 1 from the supply port 2. At this time, other components such as a bubble adjusting agent may be added as appropriate. Further, the physical foaming agent is injected into the extruder 1 from the foaming agent injection port 3. The polyethylene-based resin is melted by the extruder 1 and the polyethylene-based resin is kneaded with a physical foaming agent and other components to obtain a polyethylene-based resin melt.

Subsequently, the mandrel 5 arranged on the downstream side of the annular die 4 while taking out the tubular foam 7 formed by extruding the polyethylene-based resin melt from the annular die 4 attached to the tip of the extruder 1. A polyethylene-based resin foam sheet 8 which is a sheet-like foam can be obtained by passing over the mandrel 5 and cutting the sheet by an incision means such as a cutter blade 6 installed on the mandrel 5.

In the above description, the embodiment of manufacturing the polyethylene-based resin foam sheet 8 by cutting open the tubular foam 7 has been described, but the manufacturing method of the present invention is not limited to this, and for example, the tubular foam 7 is drawn. It is also possible to form a polyethylene-based resin foam sheet 8 by passing it through a pinch roll (not shown) while taking it, and fusing the inner surfaces of the tubular foam 7 with each other.

Further, by winding the sheet-shaped foam 8 with a winder (not shown), a roll-shaped polyethylene resin foam sheet 8 can be obtained.

The roll-shaped material is shipped after undergoing processes such as cutting and packaging, for example.

In the above description, the method for producing the polyethylene-based resin foamed sheet which is a single layer has been described, but it is also possible to produce a multi-layered sheet-shaped foam. Specifically, a polyethylene resin melt for forming a resin layer formed by kneading a polyethylene resin is laminated on a polyethylene resin melt for forming a foam layer formed by kneading a polyethylene resin and a physical foaming agent. A polyethylene-based resin foam sheet having a polyethylene-based resin foam layer and a polyethylene-based resin layer laminated and adhered to the foam layer by taking up a tubular foam formed by co-extruding from an annular die (hereinafter, (Also also referred to as a multilayer foam sheet) can be manufactured.

In this case, for example, foaming is performed by attaching a coextrusion annular die to the outlet of the foam layer forming extruder and coextruding using a device in which the resin layer forming extruder is connected to the coextrusion annular die. A tubular multi-layer foam sheet having a layer and a resin layer can be obtained, and the tubular multi-layer foam sheet can be manufactured by listening or passing through a pinch roll as described above. The resin layer may be in a non-foamed state or a foamed state.

As the foam layer and the resin constituting the resin layer, the polyethylene-based resin described above can be used as the material of the polyethylene-based resin foam sheet which is a single layer. Further, in the case of the form of the multilayer foamed sheet, the average thickness, the basis weight, the independent cell ratio, the apparent density, the ratio of the average cell diameter in the thickness direction to the average cell diameter in the extrusion direction, and the thickness direction with respect to the average cell diameter in the width direction. The ratio of the average cell diameter can be obtained by performing various measurements on the multilayer foamed sheet.

From the viewpoint of being able to increase the stiffness while maintaining the cushioning property, the basis weight of the resin layer in the multilayer foamed sheet is preferably 1 g / m ^{2 or more and 40 g / m 2 or} less per side, and 1.5 g / m /. It is more preferably m ² or more and 20 g / m ² or less.

The basis weight of the resin layer is calculated by multiplying the thickness of the resin layer by the density of the resin constituting the resin layer and converting it into a unit, the ratio of the discharge amount between the foam layer and the resin layer at the time of extrusion, and the multilayer foam sheet. It can be calculated from the relationship with the basis weight of.

(Polyethylene resin foam sheet and roll)
The polyethylene-based resin foam sheet of the present invention extrudes a polyethylene-based resin melt obtained by kneading a polyethylene-based resin and a physical foaming agent containing 1-chloro-3,3,3-trifluoropropene, and has an average thickness of 2 mm or less. , Basis weight 10 g / m ² or more and 100 g / m ² or less, closed cell ratio 5% or more and 85% or less, ratio of average cell diameter in thickness direction to average cell diameter in extrusion direction 0.1 or more and 0.6 or less, width direction It is a polyethylene-based resin foamed sheet having a ratio of 0.2 or more and 0.8 or less of the average cell diameter in the thickness direction to the average cell diameter of the above.

According to the polyethylene-based resin foamed sheet of the present invention, 1-chloro-3,3,3-trifluoropropene is used as at least a part of the physical foaming agent. Therefore, it is possible to shorten or omit the curing step for reducing the residual amount of flammable butane or other aliphatic hydrocarbons, which is necessary before storing in a closed container, especially when exporting. Moreover, since the thickness of the foamed sheet is restored at an early stage, the curing process can be shortened. Further, the obtained polyethylene-based resin foamed sheet exhibits the same physical characteristics as the polyethylene-based resin foamed sheet formed by using an aliphatic hydrocarbon such as butane as a physical foaming agent in the same extrusion production method. Therefore, according to the present invention, it is possible to promptly ship and export a polyethylene-based resin foam sheet having good physical properties.

From the above viewpoint, the content of the flammable physical foaming agent in the polyethylene-based resin foamed sheet is preferably 0.05% by mass or less, and more preferably 0% by mass. The flammable physical foaming agent may be selected from 1 or one selected from an aliphatic hydrocarbon having 3 or more and 6 or less carbon atoms, an aliphatic alcohol having 1 or more and 4 or less carbon atoms, and an aliphatic ether having 2 or more and 8 or less carbon atoms. Two or more physical foaming agents can be mentioned. When the foamed sheet contains a plurality of flammable physical foaming agents, the total of these contents is taken as the above-mentioned content.

Further, a multi-layer foamed sheet using the above polyethylene-based resin foamed sheet can also be used. In the multilayer foamed sheet of the present invention, a polyethylene-based resin layer is laminated and adhered to at least one sheet surface of the polyethylene-based resin foamed sheet. In particular, it is preferable that the polyethylene resin layers are laminated and adhered to both sides of the polyethylene resin foam sheet by coextrusion.

In the polyethylene-based resin foam sheet of the present invention, the polyethylene-based resin, the average thickness, the basis weight, the closed cell ratio, the ratio of the average cell diameter in the thickness direction to the average cell diameter in the extrusion direction, and the thickness direction with respect to the average cell diameter in the width direction. For the embodiment of the specific invention such as the ratio of the average bubble diameter, the description in the column of "Method for producing a polyethylene-based resin foam sheet" is referred to, and the detailed description thereof will be omitted. Regarding the multilayer foamed sheet, the description in the column of "Method for manufacturing polyethylene-based resin foamed sheet" is referred to, and detailed description thereof will be omitted.

The roll-shaped product of the present invention is a polyethylene-based resin foam sheet wound in a roll shape. When a foamed sheet is produced using an aliphatic hydrocarbon such as butane as in the conventional case, there is a problem that it takes time to dissipate the foaming agent remaining on the foamed sheet, and the foamed sheet is particularly rolled. In the case of a product, the foaming agent of the foam located in the center of the roll-shaped material in the thickness direction (that is, between the core side and the outermost surface side of the roll-shaped material) is less likely to disperse, and the residual amount of butane. Was difficult to reduce. In the present invention, since the polyethylene-based resin foam sheet is manufactured by using nonflammable 1-chloro-3,3,3-trifluoropropene as a physical foaming agent, it can be cured after production even in the form of a roll. The process can be omitted or shortened for export.

The foamed sheet, which is a roll, usually has a roll width of 700 mm or more and 4000 mm or less, a total length of the foamed sheet of 100 m or more and 2000 m or less, and a roll diameter of 200 mm or more and 2000 mm or less. However, the roll diameter indicates the diameter when a 3-inch winding core tube (outer diameter 80 mm) is used for the winding core.

(Use)
In the method for producing a polyethylene-based resin foamed sheet of the present invention and the polyethylene-based resin foamed sheet and its roll-like material described above, the use of the polyethylene-based resin foamed sheet is not particularly limited, but it is in the form of a glass plate for a liquid crystal panel or the like. It is suitably used as a paper for materials, a packing material, a cushioning material, and the like. For example, an effervescent sheet used as an interleaving paper for plate-like materials has a cushioning property for protecting an object to be packaged such as a glass plate, and has a small amount of sagging when cantilevered (strong stiffness). It is also required to have excellent handleability when dressing. Further, in recent years, large-scale thinning of glass plates for liquid crystal panels and the like has progressed, and foam sheets used as paper in the meantime are also required to have thinner thickness. The polyethylene-based resin foam sheet is suitable for satisfying such a requirement.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

As a manufacturing apparatus, a tandem type extruder equipped with an extruder having a barrel inner diameter of 65 mm and an extruder having a barrel inner diameter of 90 mm connected to the downstream side thereof was used.

An annular die (lip diameter 60 mm) was attached to the outlet of the extruder, and a mandrel having a diameter of 150 mm was installed on the downstream side of the annular die. The mandrel used was provided with a cutter blade for cutting sheet-shaped foam.

The resin materials used in each Example and each Comparative Example are as follows.
Polyethylene resin (LDPE1): low density polyethylene, manufactured by NUC Co., Ltd., NUC-8321, MFR (190 ° C, load 2.16 kg) 2.4 g / 10 min, melt tension 52.2 mN at 190 ° C.
Polyethylene resin (LDPE2): low density polyethylene, manufactured by NUC Co., Ltd., NUC / 8008, MFR (190 ° C, load 2.16 kg) 4.7 g / 10 min, melt tension 46.6 mN at 190 ° C.
Polyethylene resin (LDPE3): low density polyethylene, manufactured by NUC Co., Ltd., NUC / 8009, MFR (190 ° C, load 2.16 kg) 9.0 g / 10 min, melt tension 20 mN at 190 ° C.
Polyethylene resin (LLDPE1): Linear low-density polyethylene, manufactured by Tosoh Corporation, M55, MFR (190 ° C, load 2.16 kg) 8.0 g / 10 min, melt tension 3 mN at 190 ° C.
For the measurement of MFR and melt tension, the above-mentioned method is referred to.

The foaming agents used to carry out each Example and each Comparative Example are as follows.
1-Chloro-3,3,3-trifluoropropene (HCFO1233zd)
・ Carbon dioxide (CO ₂ )
-Silver butane (s-Bu) A mixture in which the mass ratio of isobutane to normal butane (isobutane: normal butane) was adjusted to 30:70.-1,3,3,3-Tetrafluoropropene (HFO1234ze)
The types and amounts of the foaming agents used are shown in Table 1.

A polyethylene-based resin is supplied to the extruder at the above ratio, and a chemical foaming agent containing citric acid and sodium hydrogencarbonate at a ratio of 1: 2 as a bubble adjusting agent is 1.1% by mass with respect to 100 parts by mass of the polyethylene-based resin. Partially added, heated, melted, kneaded, and then a foaming agent was injected to obtain a polyethylene-based resin melt adjusted to an appropriate resin temperature, which was introduced into an annular die.

The types and classifications (combustible or non-combustible) of the foaming agents and their blending amounts, as well as the resin temperature (° C.) and the discharge amount (kg / hr) in each Example and each Comparative Example are shown in Table 1.

Subsequently, the polyethylene-based resin melt introduced into the annular die was extruded into a cylindrical shape along the outer surface of the mandrel to form a tubular foam. In Examples 1 to 5, Comparative Examples 1 to 5, and Comparative Example 7, the blow-up ratio was set to 2.5. Further, in Example 6, Comparative Example 6, and Comparative Example 8, a mandrel having a diameter of 212 mm was used, and the blow-up ratio was set to 3.5. A tubular foam was cut open with a cutter blade provided on the mandrel, and was taken up at an appropriate take-up speed and wound into a roll to obtain a polyethylene-based resin foam sheet.

The die pressure (G: gauge pressure) (MPa) and take-up speed (m / min) of the annular die in each Example and each Comparative Example are shown in Table 1.

The foamed sheets produced in each of the above-mentioned Examples and Comparative Examples were measured and evaluated as follows.

Apparent density Five points were randomly selected in the extrusion direction of the polyethylene-based resin foamed sheet, and five test pieces having the total width of the foamed sheet × the length of 100 mm in the extrusion direction were cut out at each place. The volume (m ³ ) obtained from the mass (kg) and appearance dimensions of each test piece is measured, and the mass (kg) is divided by the volume (m ³ ) to obtain the apparent density (kg / m ³ ) of each test piece. The calculated average value of the obtained values was used as the apparent density (kg / m ³ ).

Foaming Ratio The value obtained by dividing the density (kg / m ^{3) of the polyethylene resin used by the apparent density (kg / m 3 )} calculated by the above method was calculated as the foaming ratio.

Average Thickness Over the entire width of the polyethylene-based resin foam sheet, the thickness (mm) of the foam sheet at 15 points at equal intervals along the width direction was measured, and the average thickness by the arithmetic average was calculated. The measurement was performed on three randomly selected locations of the foam sheet, and the arithmetic mean value of the calculated average thickness values of the three locations was taken as the average thickness (mm) of the polyethylene-based resin foam sheet. The average thickness of the polyethylene-based resin foamed sheet is a value obtained by measuring the thickness of the polyethylene-based resin foamed sheet after recovery when the thickness becomes steady.

For Examples 3 to 5 and Comparative Examples 3 to 5, the average thickness of the polyethylene-based resin foam sheet one day (24 hours) after being picked up from the extruder was measured, and then the polyethylene-based resin foam sheet was picked up from the extruder. The thickness recovery rate after 1 day was calculated from the following formula.
Thickness recovery rate after 1 day (%) = [Average thickness after 1 day / Average thickness after recovery] x 100

Basis weight A polyethylene-based resin foam sheet is cut out to a size of 100 mm × 100 mm to prepare a test piece, the area of the test piece (m ² ) and the mass (kg) of the test piece are measured, and the mass (kg) is the area (m). The basis weight (g / m ² ) was obtained by dividing by ² ).

Closed cell ratio The closed cell ratio (%) of the polyethylene-based resin foam sheet was determined as follows in accordance with Procedure C described in ASTM D 2856-70. The actual volume of the test piece (volume of closed cells and resin) measured using a test piece cut out from a polyethylene-based resin foam sheet to an appropriate size and using an air comparison hydrometer 930 type manufactured by Toshiba Beckman Co., Ltd. The closed cell ratio (%) was calculated from Vx (cm ³ ) by the following formula (1).
Closed cell ratio (%) = (Vx-W / ρ) x 100 / (Va-W / ρ) ... (1)
However, Va, W, and ρ in the above formula are as follows.
Va: Apparent volume of the test piece used for the measurement (cm ³ )
W: Mass of test piece (g)
ρ: Density of the resin composition constituting the test piece (g / cm ³ )
The density ρ (g / cm ³ ) of the resin composition is obtained by performing an operation of defoaming bubbles by a heating press and then cooling the test piece used for the mass w (g) of the test piece and the test piece. It was obtained from the volume of the sample (cm ³ ).

In addition, the closed cell ratio was measured using a test piece adjusted so that the apparent volume was approximately 20 cm ³ by stacking a plurality of foam sheets.

Surface properties of the foamed sheet The surface of one side of the foamed sheet was visually observed from a distance of 1 m under an indoor light and evaluated as follows.
◯: Smoothness and good appearance △: There was a part where uneven elongation was confirmed ×: There was uneven elongation, and unevenness and poor appearance due to bubble rupture were observed.

Content of flammable gas in foam sheet (wt%)
In the sheet-shaped foam immediately after being wound into a roll, 1 g of a test piece was cut out from the center portion in the width direction of the sheet, which was between the core and the outer surface of the roll. This test piece is immersed in a 50 cc solvent containing a known amount of cyclopentane in a closed container at room temperature for 24 hours, and the flammable physical foaming agent (with 3 to 6 carbon atoms) remaining in the test piece is used. Aliphatic hydrocarbons) were extracted in the solvent.

Then, the amount of the aliphatic hydrocarbon having 3 to 6 carbon atoms extracted in the solvent is quantified by the internal standard method using a gas chromatograph, and remains in the test piece from the mass of the test piece measured in advance. The amount of the foaming agent was determined, and this was used as the content of flammable gas in the foamed sheet.

Average bubble diameter The average bubble diameter in the extrusion direction (MD) was determined by the following method. First, the polyethylene-based resin foam sheet was cut so as to be parallel to the extrusion direction and divided into 10 equal parts in the width direction to form 10 test pieces A. A cross-sectional photograph of a vertical cross section (10 faces in total) on one side of each test piece A was taken. Next, at the central portion in the thickness direction in the cross-sectional photograph, a line segment having a length of 30 mm is drawn in the extrusion direction, the number of all bubbles intersecting with the line segment is measured, and the length of the line segment (that is, 30 mm) is measured. Was divided by the number of measured bubbles to obtain the bubble diameter in the extrusion direction. The arithmetic mean value of the bubble diameter obtained on each of the 10 surfaces was obtained, and this value was taken as the average bubble diameter (μm) in the extrusion direction.

The starting point of the line segment was the outermost end of the bubble. Also, when a part of the bubble intersected with the line segment, it was measured as a bubble.

Similarly, the average bubble diameter in the width direction (TD) was determined by the following method. First, in the width direction of the foam, the foam was cut at 10 points at random in parallel with the width direction and in the extrusion direction to form 10 test pieces B. A cross-sectional photograph of a vertical cross section (10 faces in total) on one side of each test piece B was taken. Next, in the cross-sectional photograph, a line segment having a length of 30 mm is drawn in the width direction at the center in the thickness direction, the number of all bubbles intersecting with this line segment is measured, and the length of the line segment (that is, 30 mm) is measured. The value divided by the number of measured bubbles was taken as the bubble diameter in the width direction. The arithmetic mean value of the bubble diameter obtained on each of the 10 surfaces was obtained, and this value was taken as the average bubble diameter (μm) in the width direction.

The starting point of the line segment was the outermost end of the bubble. Also, when a part of the bubble intersected with the line segment, it was measured as a bubble.

The average bubble diameter in the thickness direction (VD) was determined by the following method. Similar to the measurement of the average bubble diameter in the extrusion direction described above, a cross-sectional photograph of a vertical cross section was taken with respect to the test piece A. Next, in the cross-sectional photograph, a line segment is drawn in the total thickness direction of the foam, the number of bubbles on the line segment is measured, and the value obtained by dividing the length of the line segment by the number of bubbles is the bubble diameter in the thickness direction. And said. The arithmetic mean value of the bubble diameter obtained on each of the 10 surfaces was obtained and used as the average bubble diameter (μm) in the thickness direction.

The ratio of the average cell diameter in the thickness direction (VD / MD) to the average cell diameter in the extrusion direction and the ratio of the average cell diameter in the thickness direction (VD / TD) to the average cell diameter in the width direction in Table 2 are determined by the above methods. Calculated from the measured value.

The results of the above measurements and evaluations are shown in Table 2.

(* 1) Mol amount of foaming agent blended in 1 kg of polyethylene resin (* 2) Weight of foaming agent injected into the extruder per unit time (* 3) Used for 100 parts by mass of LDPE supplied to the extruder Amount of foaming agent (* 4) Ratio of HCFO1233zd or HFO1234ze to 100 mol% of foaming agent injected into the extruder

As shown in Table 1, each Example was carried out using 1-chloro-3,3,3-trifluoropropene as the physical foaming agent under the condition that the flammable physical foaming agent did not remain on the produced foaming sheet. rice field. Therefore, the foamed sheets obtained in each example can be quickly stored in a closed container such as a container by omitting the curing step for dissipating the foaming agent remaining on the foamed sheet. There is no risk of flammable physical foaming agent accumulating inside.

From Table 1, Examples 1 to 6 in which HCFO1233zd was used as the physical foaming agent had extrusion conditions and foaming conditions as compared with Comparative Examples 1 to 6 in which the same production conditions were used except that silver butane was used as the physical foaming agent. No significant difference was observed in the pick-up state, and from Table 2, it was possible to obtain an equivalent sheet in terms of physical properties.

The thickness recovery rates of Example 3, Example 4, and Example 5 after 1 day were 96%, 93%, and 100%, respectively. On the other hand, the thickness recovery rates of Comparative Example 3, Comparative Example 4, and Comparative Example 5 after 1 day were 95%, 84%, and 95%, respectively. From these results, it was confirmed that Examples 3 to 5 tended to recover the thickness after production faster than Comparative Examples 3 to 5 under the same production conditions except that silver butane was used as the physical foaming agent. .. It was suggested that the curing process could be shortened because the thickness could be restored at an early stage.

In Comparative Example 7, HFO1234ze, which is a hydrofluoroolefin (HFO) similar to HCFO1233zd used in Examples, was used as the physical foaming agent, but it was difficult to foam the resin, and a sheet-shaped foam was obtained. I couldn't.

In Comparative Example 8, CO ₂ was used as the physical foaming agent, but the ductility of the polyethylene-based resin melt was poor, and a sheet-shaped foam could not be obtained.

1 Extruder 2 Supply port 3 Foaming agent injection port 4 Circular die 5 Mandrel 6 Cutter blade 7 Cylindrical foam 8 Polyethylene resin foam sheet

Claims (7)

By taking out a tubular foam formed by extruding a polyethylene-based resin melt made by kneading a polyethylene-based resin and a physical foaming agent from an annular die, an average thickness of 2 mm or less and a basis weight of 10 g / m ² or more. 100 g / m ² or less, closed cell ratio 5% or more and 85% or less, ratio of average cell diameter in the thickness direction to average cell diameter in the extrusion direction 0.1 or more and 0.6 or less, in the thickness direction with respect to the average cell diameter in the width direction A method for producing a polyethylene-based resin foamed sheet having an average cell diameter ratio of 0.2 or more and 0.8 or less.
The polyethylene-based resin contains low-density polyethylene and / or linear low-density polyethylene.
As the physical foaming agent, a physical foaming agent containing 1-chloro-3,3,3-trifluoropropene was used.
A method for producing a polyethylene-based resin foam sheet, wherein the blending amount of 1-chloro-3,3,3-trifluoropropene is 0.5 mol or more and 3.0 mol or less per 1 kg of the polyethylene-based resin. The method for producing a polyethylene-based resin foam sheet according to claim 1, wherein the polyethylene-based resin is low-density polyethylene. The method for producing a polyethylene-based resin foam sheet according to claim 1 or 2, wherein the melt flow rate (190 ° C., load 2.16 kg) of the polyethylene-based resin is 2 g / 10 min or more and 20 g / 10 min or less. .. The method for producing a polyethylene-based resin foam sheet according to any one of claims 1 to 3, wherein the polyethylene-based resin has a melt tension of 15 mN or more and 300 mN or less at 190 ° C. The method for producing a polyethylene-based resin foam sheet according to any one of claims 1 to 4, wherein the polyethylene-based resin foam sheet has an apparent density of 20 kg / m ³ or more and 300 kg / m ³ or less. A polyethylene-based resin melt obtained by kneading a polyethylene-based resin containing low-density polyethylene and / or a linear low-density polyethylene with a physical foaming agent containing 1-chloro-3,3,3-trifluoropropene is extruded. Foamed, average thickness 2 mm or less, basis weight 10 g / m ² or more and 100 g / m ² or less, closed cell ratio 5% or more and 85% or less, ratio of average cell diameter in the thickness direction to average cell diameter in the extrusion direction 0. A polyethylene-based resin foam sheet having a ratio of 1 or more and 0.6 or less, an average cell diameter in the thickness direction to 0.2 or more and 0.8 or less , and an apparent density of 20 kg / m ³ or more and 300 kg / m ³ or less . A roll-shaped material obtained by winding the polyethylene-based resin foam sheet according to claim 6 into a roll shape.

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