JP2012218279A - Packaging foam sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging foam sheet, which has excellent flexibility and cushioning properties allowing stable wrapping while hardly damaging a packaging object and further can effectively prevent, even when storing a packaging object having a coating film, protective film or the like on the surface for a long period and further under high temperature, surface contamination of such a packaging object.SOLUTION: The packaging foam sheet has a thickness of 0.3-5 mm, and includes a resin layer using a polyolefin resin as substrate resin which is laminated on at least one surface of a polyolefin resin foam layer. The bending elastic modulus of the polyolefin resin that is the substrate resin of the resin layer is 600 MPa or less, 5-40 wt.% of a filler having an average particle size of 2-50 μm is dispersed and mixed to the resin layer, the basis weight of the resin layer is 0.5-10 g/m, and the ratio (D/B) of the average particle size of the filler (D) [μm] to the basis weight of the resin layer (B) [g/m] is 1-12.

Description

  The present invention relates to a foam sheet for packaging, and more particularly to a foam sheet for packaging useful as a packaging material / packaging material for precision machines, home appliances, electronic parts, various automobile articles, and the like.

  Polyolefin-based resin foam sheets have been used as materials for various cushioning materials and packaging materials so far because they are flexible and excellent in cushioning properties, and have waterproofness, moistureproofness, and heat insulation properties.

  As such a foam sheet, for example, polyolefin resin foam sheets described in Patent Document 1 and Patent Document 2 are known.

  These resin foam sheets contain conductive additives and antistatic agents in the resin, and are difficult to damage the packaged body because they are difficult to dust and have flexibility and buffering properties. It is suitably used as a packaging material / packaging material.

JP 2005-74771 A JP-A-7-242285

  However, recently, in the case of surface protection sheets for precision instruments and home appliances that have been subjected to paint processing, when this protective sheet is peeled off, the appearance of the surface of the packaged article may be deteriorated. It is particularly noticeable when the temperature increases, and it has been reported that the appearance of the packaged article is impaired.

  Such a phenomenon is not limited to the surface protective sheet, and even when the conventional polyolefin-based resin foam sheet is used as a packaging material, an undesirable pattern or spots appear on the surface of the packaged body, or some coating films It has been confirmed that undesirable surface defects, such as components floating on the surface, occur as well.

  Therefore, development of a packaging material / packaging material that does not cause such surface defects of the packaged body is strongly demanded, but the present situation is that a satisfactory one has not yet been obtained.

  The present invention has been made in view of the above circumstances, is excellent in flexibility and buffering properties, hardly damages the surface of the package body, can protect the package body from impact, and is coated on the surface. To provide a foamed sheet for packaging capable of effectively preventing surface defects of such a packaged body even when the packaged body having a film, a protective film or the like is stored for a long period of time or at a high temperature. Is an issue.

  As a result of intensive studies to solve the above problems, the inventors of the present invention, while packing the conventional packing material, the surface of the packing material and the coating film on the surface of the package body are closely adhered, Long-term surface contact continues. If the external environment changes during this time, such as a rise in temperature, so-called suffocation occurs, and a small portion of the solvent component of the coating film bleeds out to the surface, resulting in an increase in the solvent concentration on the surface of the coating film. It was found that the surface of the film was eroded, and undesirable patterns and spots appeared on the surface of the packaged body, and that some coating film components appeared on the surface. As a result of further study, this phenomenon is mainly caused by the surface contact state between the surface of the packaging material and the coating film on the surface of the package, and if this surface contact state can be prevented or suppressed, It reached the knowledge that the above-mentioned stuffiness phenomenon was suppressed and a desired package was obtained. The present invention has been made based on these findings.

  That is, according to this application, the following invention is provided.

<1> A foamed sheet for packaging having a thickness of 0.3 to 5 mm, wherein a resin layer having a polyolefin resin as a base resin is laminated on at least one surface of a polyolefin resin foam layer by coextrusion,
The flexural modulus of the polyolefin resin that is the base resin of the resin layer is 600 MPa or less, and 5 to 40% by weight of a filler having an average particle diameter of 2 to 50 μm is dispersed and blended in the resin layer. basis weight of 0.5 to 10 g / ^{m 2,} and the basis weight of the resin layer (B) the average particle size of the filler with respect to ^{[g / m 2] (D} ) the ratio of [μm] (D / B) Is a foamed sheet for packaging, characterized by being 1-12.

  <2> The foamed sheet for packaging according to the first aspect, wherein the coefficient of static friction of the resin layer surface is 0.5 or more.

  <3> The packaging foam sheet according to the first or second invention, wherein the polyolefin resin which is the base resin of the resin layer is low-density polyethylene.

  <4> The packaging foam sheet according to any one of the first to third inventions, wherein the polyolefin resin forming the foam layer is low-density polyethylene.

<5> The packaging foam sheet according to any one of the first to fourth inventions, wherein the apparent density of the packaging foam sheet is 15 to 90 kg / m ³ .

  <6> The foamed sheet for packaging according to any one of the first to fifth inventions, wherein the filler is talc.

  <7> The foamed sheet for packaging according to any one of the first to fifth inventions, wherein the filler is calcium carbonate.

  The packaging foam sheet of the present invention is excellent in flexibility and shock-absorbing properties, so that the surface of the packaged body is hard to be damaged, the packaged body can be protected from impact, and the coating film or protective film is formed on the surface. Even when the packaged bodies having the above are stored for a long period of time or at a high temperature, surface defects of these packaged bodies can be effectively prevented.

It is sectional drawing which shows the example of 1 structure of the foaming sheet for packaging of this invention. It is explanatory drawing of a coextrusion method.

The present invention relates to a foam sheet for packaging in which a resin layer having a polyolefin resin as a base resin is laminated on at least one surface of a polyolefin resin foam layer by coextrusion, and the thickness thereof is 0.3 to 5 mm, the flexural modulus of the polyolefin resin that is the base resin of the resin layer is 600 MPa or less, and 5 to 40% by weight of a filler having an average particle diameter of 2 to 50 μm is dispersed and blended in the resin layer. the ratio of the basis weight of the resin layer is 0.5 to 10 g / ^{m 2,} and the basis weight of the resin layer (B) the average particle size of the filler with respect to ^{[g / m 2] (D} ) [μm] ( D / B) is 1 to 12.

  Hereinafter, the foamed sheet for packaging according to the present invention will be sequentially described.

  One structural example of the packaging foam sheet of the present invention is shown in a sectional view in FIG. This foaming sheet 1 for packaging is obtained by laminating a polyolefin resin layer 3 containing a filler on at least one surface of a polyolefin resin foam layer 2. Here, the description will focus on the one in which the polyolefin-based resin layer 3 is laminated on one side, but it is of course possible to have a configuration in which the two sides are laminated in accordance with the case.

In the foamed sheet for packaging of the present invention, 5 to 40% by weight of a filler having an average particle diameter of 2 to 50 μm is dispersed and blended on at least one surface of the foamed layer, and the basis weight of the resin layer is 0.5 to 10 g / m ^2. And a specific resin layer in which the ratio (D / B) of the average particle diameter (D) [μm] of the filler to the basis weight (B) [g / m ² ] of the resin layer is 1 to 12. By forming by the co-extrusion method, a large number of fine irregularities are formed on the surface of the resin layer due to the presence of the filler while most or all of the filler is covered with the polyolefin-based resin.

  The conventional foamed sheet for packaging made of polyolefin resin foamed sheet, etc. itself is flexible, and its surface is also flexible, so it follows the shape of the packaged object when packaged, and further the foamed sheet for packaging It is considered that the surface of the surface is deformed and both are in surface contact.

  The foamed sheet for packaging according to the present invention has a large number of fine irregularities derived from the filler formed on the surface thereof, so that when the article to be packaged is packaged with the foamed sheet for packaging, the foamed sheet for packaging and the packaged Since the product is in a point contact state substantially, the above-described stuffiness phenomenon is suppressed, and it is considered that the occurrence of defective surface of the packaged product can be suppressed.

  In addition, since the filler is covered with the polyolefin resin, the surface of the package is not damaged by the filler.

  When describing the polyolefin resin layer 3 constituting the foam sheet 1 for packaging of the present invention, the material constituting the polyolefin resin layer 3 has a flexural modulus of 600 MPa or less so as not to damage the surface of the packaged body. It is necessary to use a highly flexible resin that is preferably 450 MPa or less, more preferably 300 MPa or less. The lower limit is about 10 MPa. If the flexural modulus is too high, the surface of the foam sheet for packaging becomes hard, and it becomes slippery with the object to be packaged, so that the surface of the object to be packaged is easily damaged. Examples of such resins include polyethylene resins, polypropylene resins, and mixtures of two or more thereof. As the polyethylene-based resin, a copolymer of ethylene and a comonomer such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate copolymer having an ethylene component exceeding 50 mol%. Furthermore, the mixture of 2 or more types of these is mentioned. Examples of the polypropylene resin include propylene homopolymers, propylene-ethylene copolymers, propylene-butene copolymers, propylene copolymers such as propylene-ethylene-butene copolymers, and mixtures of two or more of these. Is mentioned. Among the polyolefin resins, polyethylene resins, particularly low density polyethylene, are preferably used from the viewpoint of flexibility such as low surface hardness and excellent surface protection performance of the package.

  The flexural modulus of the base resin is JIS K7171 (1994), using a test piece having a thickness of 2 mm, a width of 25 mm and a length of 40 mm, a span distance of 30 mm, and an indenter radius R1 of 5.0 mm. This is a value measured under the condition that the radius R2 of the support base is 2.0 mm and the test speed is 2 mm / min.

The basis weight of the polyolefin resin layer 3 B [g / ^{m 2]} is preferably 0.5 to 10 g / ^{m 2,} more preferably 0.7~5g / ^{m 2.} Such an extremely thin resin layer can be produced by a coextrusion method described later. When the basis weight B of the polyolefin resin layer 3 is too small, it is difficult to form the resin layer at the time of production even in the coextrusion method, while the basis weight B of the polyolefin resin layer 3 is too large. And depending on the use of the packaging foam sheet 1, the lightness and flexibility may be insufficient, and the raw material costs during the production of the packaging foam sheet 1 will also increase.

  The basis weight B is adjusted by adjusting the discharge amount of the resin melt for forming the resin layer and the take-up speed of the foam sheet. The basis weight of the polyolefin resin layer 3 can be obtained by the following method.

When the foam sheet 1 for packaging is manufactured, the extrusion amount X [kg / hour] of the polyolefin-based resin layer 3 and the width W [m] of the resulting foam sheet 1 for packaging, and the obtained packaging are included in the extrusion foaming conditions. When the length L per unit time of the foam sheet 1 for packaging (= the take-up speed of the foam sheet for packaging) [m / hour] is known, the basis weight of the polyolefin resin layer 3 according to the following formula (1) [ g / m ² ] can be obtained.

ポリオレフィン系樹脂層３には、充填剤が配合されるが、この充填剤としては、平均粒子径が好ましくは２〜５０μｍ、より好ましくは３〜２０μｍのものが用いられる。平均粒子径が小さすぎると、樹脂層の表面に微細な凹凸が形成されにくく所期の目的を達成することが困難となり、平均粒子径が大きすぎると充填剤が樹脂層の表面から数多く突出して被包装物の表面を傷つけるおそれがある。また、樹脂層中に存在する充填剤の絶対数が少なくなるため表面の凹凸が粗くなり、包装用発泡シートと被包装物とが実質的に面接触となってしまうので、被包装材の表面不良を防ぐという所期の目的を達成することができなくなる。

The polyolefin resin layer 3 is mixed with a filler. As the filler, one having an average particle diameter of preferably 2 to 50 μm, more preferably 3 to 20 μm is used. If the average particle size is too small, it will be difficult to form fine irregularities on the surface of the resin layer, and it will be difficult to achieve the intended purpose. If the average particle size is too large, many fillers will protrude from the surface of the resin layer. There is a risk of damaging the surface of the package. In addition, since the absolute number of fillers present in the resin layer is reduced, the surface irregularities become rough, and the packaging foam sheet and the packaged object are substantially in surface contact with each other. The intended purpose of preventing defects cannot be achieved.

  In addition, the average particle diameter in this invention means the particle diameter (volume average particle diameter: d50) when the cumulative volume with respect to the volume of all the particles becomes 50% based on the particle size distribution measured by the laser diffraction scattering method. .

  The blending amount of the filler is preferably 5 to 40% by weight, more preferably 10 to 30% by weight, and particularly preferably 15 to 25% by weight with respect to 100 parts by weight of the base resin of the polyolefin-based resin layer 3. It is good. If the blending amount of the filler is too small, it will be difficult to achieve the intended purpose of the present invention. If the blending amount of the filler is too large, the resin layer will be difficult to stretch at the time of production, so that the resin layer is formed. That itself becomes difficult.

  As the filler, either an inorganic filler or an organic filler can be used. As inorganic fillers, general inorganic powders can be used as fillers such as talc, calcium carbonate, silica, mica, titanium oxide, and as organic fillers, styrene resin crosslinked fine particles and acrylic resin crosslinked fine particles can be used. Polymer fine particles such as can be used. Among these, talc and calcium carbonate are particularly preferably used because the hardness is low and the surface of the package is not particularly damaged, and the aspect ratio is relatively small among low-hardness fillers.

Moreover, in this invention, ratio (D / B) of the average particle diameter (D) [micrometer] of the filler with respect to the basic weight (B) [g / m < ² >] of the polyolefin-type resin layer 3, Preferably it is 1-12. More preferably, it is 2 to 10, more preferably 3 to 8. If the ratio D / B is too small, fine irregularities are not formed on the surface of the resin layer, making it difficult to achieve the intended purpose of the present invention. If the ratio D / B is too large, it is present in the resin layer. Since the absolute number of fillers to be used is reduced, the intended purpose of preventing the surface of the packaged material from being damaged, or preventing the surface of the packaged material from becoming defective, or the filler from protruding easily from the resin layer surface, is achieved. Difficult to do.

  Next, the polyolefin resin foam layer 2 of the foam sheet 1 for packaging according to the present invention will be described.

  In the present invention, the polyolefin resin used for the polyolefin resin foam layer 2 includes a polyethylene resin, a polypropylene resin, and a mixture of two or more thereof. As the polyethylene-based resin, a copolymer of ethylene and a comonomer such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate copolymer having an ethylene component exceeding 50 mol%. Furthermore, the mixture of 2 or more types of these is mentioned. Further, as the polypropylene resin, propylene homopolymer, propylene-ethylene copolymer, propylene-butene copolymer, propylene-based copolymer such as propylene-ethylene-butene copolymer, and a mixture of two or more of them. Is mentioned. Among the polyolefin resins, polyethylene resins, particularly low density polyethylene, are preferably used from the viewpoint of flexibility such as low surface hardness and excellent surface protection performance of the polyolefin resin layer.

  The total thickness of the foamed sheet for packaging is preferably 0 because it has a good balance between the buffering property that protects the package from the impact by preventing the surface of the package from being damaged due to external factors, and ease of packaging. 3 to 5 mm, more preferably 0.5 to 3 mm, and particularly preferably 0.5 to 2 mm.

  The thickness of the packaging foam sheet 1 is determined by measuring the thickness with a micro gauge or the like every 10 cm in the width direction of the packaging foam sheet 1 and arithmetically averaging the thickness at each measurement point.

The apparent density of the foam sheet 1 for packaging is preferably 15 to 90 kg / m ³ , more preferably 17 to 60 kg / m ³ . If the density is too small, it may be difficult to produce a foam sheet having a good appearance and the like in a stable manner. On the other hand, if the density is too large, the buffering property may be insufficient depending on the application.

The apparent density of the packaging foam sheet 1 is obtained by dividing the volume of the packaging foam sheet 1 obtained by a submerging method or the like by the weight of the packaging foam sheet 1 measured in advance, and the unit is [kg / m ³ ].

  Next, the manufacturing method of the foam sheet 1 for packaging of this invention is described. The packaging foam sheet 1 of the present invention is produced, for example, by the coextrusion foam molding method shown in FIG. Specifically, the polyolefin resin 11 for forming the foam layer is supplied to the first extruder A, melted and kneaded under heating, the foaming agent is press-fitted into the resin melt from the foaming agent injection hole 13, and further kneaded. The resin melt for forming a foam layer containing a foaming agent is used. On the other hand, the polyolefin resin 12 for resin layer formation and the filler are supplied to the second extruder B, melt kneaded under heating, and if necessary, a volatile plasticizer is injected and further kneaded to form a resin layer. Adjust the resin melt. The resin layer forming resin melt and the foaming layer forming resin melt containing the foaming agent of the first extruder A are laminated in a die and co-extruded from a die attached to the extruder outlet, and polyolefin resin foaming is performed. A packaging foam sheet in which a polyolefin-based resin layer is laminated on at least one side of the layer is obtained. By adopting the above coextrusion foam molding method, the adhesion between the polyolefin resin foam layer and the thin film polyolefin resin layer is excellent, and even if the filler is highly filled and the film is very thin, A resin layer having fine irregularities derived from the filler on the surface can be reliably obtained in a state where the filler is covered with the base resin without occurrence of tearing or the like.

  Examples of the foaming agent used in the production of the polyolefin resin foam layer of the present invention include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, isohexane, and cyclohexane, methyl chloride, and ethyl chloride. Examples thereof include organic physical foaming agents such as chlorinated hydrocarbons such as inorganic physical foaming agents such as nitrogen and carbon dioxide. Two or more of the above physical foaming agents can be mixed and used.

  The amount of the foaming agent added is appropriately adjusted according to the type of foaming agent and the apparent density of the desired polyolefin resin foamed layer, but when an organic physical foaming agent such as butane is used as the foaming agent. The amount of the organic physical foaming agent added is preferably 3 to 30 parts by weight, more preferably 4 to 20 parts by weight per 100 parts by weight of the base resin.

  In addition, in the production of the foam sheet for packaging of the present invention, a cell regulator is usually added to the polyolefin resin foam layer forming resin. As the air bubble adjusting agent, any of inorganic and organic materials that are conventionally used can be used. Examples of the inorganic foam regulator include metal salts of boric acid such as zinc borate, magnesium borate, borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate and the like. Organic foam regulators include 2,2-methylenebis (4,6-tert-butylphenyl) phosphate, sodium benzoate, calcium benzoate, aluminum benzoate, sodium stearate, citric acid and bicarbonate. A combination of sodium or an alkali salt of citric acid and sodium bicarbonate is used. These bubble regulators can be used in combination of two or more.

  The amount of the air bubble regulator added is, for example, preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight with respect to 100 parts by weight of the base resin. Moreover, it is preferable to use a bubble regulator as a masterbatch.

  Further, when the foamed sheet for packaging of the present invention is produced, a hydrocarbon compound such as propane, normal butane, and isobutane may be added to the polyolefin resin layer forming resin as a volatile plasticizer, if necessary. These hydrocarbon compounds have an extremely thin resin layer, so that the resin for forming the resin layer can be plasticized without being involved in foaming. The temperature can be lowered to a temperature that does not hinder the resin layer, and even at such a low resin temperature, extensibility following the foamed layer can be imparted to the resin layer. As a result, the resin layer is usually difficult to stretch when the filler is highly filled, but an extremely thin resin layer can be formed without destroying the cell structure of the foam layer. The hydrocarbon compound in the polyolefin resin layer is almost volatilized by the heat at the time of extrusion at the time of extrusion, so compared with general plasticizers such as liquid paraffin and fatty acid esters that are likely to remain in the resin layer. Thus, physical properties such as rigidity of the resin layer are not deteriorated.

  The addition amount of the volatile plasticizer is appropriately adjusted according to the type of polyolefin resin that is the base resin of the resin layer, the addition amount of the filler, the thickness of the resin layer, and the like. And about 5 to 50 parts by weight per 100 parts by weight in total.

  The packaging foam sheet 1 of the present invention preferably imparts antistatic properties. In this case, sufficient antistatic properties can be imparted by adding an antistatic agent only to the resin layer. The antistatic agent is preferably a polymer type antistatic agent.

  Specific examples of the polymer-type antistatic agent include polyethylene oxide, polypropylene oxide, polyethylene glycol, polyether, polyester amide, polyether ester amide, an ionomer such as an ethylene-methacrylic acid copolymer, and a polyethylene glycol methacrylate polymer. A molecule selected from quaternary ammonium salts such as quaternary ammonium salts, a mixture of two or more, or a copolymer of two or more, and a copolymer of these with another resin such as polypropylene. Examples include resins having a polar group in the chain and capable of complexing or solvating an inorganic salt or a low molecular weight organic protonic acid salt. May be.

  The compounding amount of the polymer type antistatic agent is preferably 5 to 70 parts by weight, more preferably 10 to 40 parts by weight with respect to 100 parts by weight of the ethylene-based polymer having flexibility.

  Furthermore, in the production of the foam sheet for packaging 1 of the present invention, various known additives used for the production of polyolefin resin foams can be used as appropriate. Examples of the additive include an antioxidant, a heat stabilizer, a weathering agent, an ultraviolet ray inhibitor, a flame retardant, an inorganic filler, a shrinkage inhibitor, and a colorant.

  As described above, the foamed sheet for packaging according to the present invention is excellent in flexibility and buffering properties, so that it is difficult to damage the packaged body and can be stably packaged. In addition, even when a packaged body having a coating film or a protective film on the surface is stored at a high temperature for a long period of time, in order to maintain an appropriate contact state without being in close contact with the surface of the packaged object, these It becomes possible to effectively prevent surface contamination of the packaged body.

  Next, the foamed sheet for packaging according to the present invention will be described in more detail with reference to examples and comparative examples.

[Example 1]
A polyolefin resin layer is formed by using a tandem extruder in which a 90 mm diameter extruder having a blowing agent inlet and a 120 mm diameter extruder are connected as a first extruder for forming a polyolefin resin foam layer. As the second extruder, an extruder having a diameter of 50 mm and L / D = 46 (L is length, D is diameter) was used. An annular die having a diameter of 94 mm was used for coextrusion of the foamed sheet at the exit of the first and second extruders.

  For forming a polyolefin resin foam layer, 100 parts by weight of low density polyethylene (flexural modulus: 205 MPa, MFR (melt flow rate) = 0.4 g / 10 min, trade name “F-102” manufactured by Sumitomo Chemical) Then, 3 parts by weight of the bubble regulator master batch was blended and supplied to the raw material inlet of an extruder having a diameter of 90 mm, followed by heating and kneading to obtain a molten resin mixture prepared at about 200 ° C. Using a physical foaming agent (70% by weight of normal butane and 30% by weight of isobutane), the molten resin mixture was press-fitted to 30 parts by weight with respect to 100 parts by weight of low-density polyethylene, and then The resultant was supplied to an extruder having a diameter of 120 mm connected to the downstream side of an extruder having a diameter of 90 mm to obtain a resin melt for forming a polyolefin-based resin foam layer at 108 ° C.

  On the other hand, in order to form a polyolefin resin layer, talc (Matsumura Sangyo Co., Ltd.) is used as a filler for 100 parts by weight of low density polyethylene (MFR = 0.4 g / 10 min, trade name “F-102” manufactured by Sumitomo Chemical). Company-made Hiefeller # 12: Average particle size 6.7 μm) 20 parts by weight, supplied to the raw material inlet of the second extruder with a diameter of 50 mm, melted by heating and prepared at about 200 ° C. A mixed butane (70% by weight of normal butane and 30% by weight of isobutane) as a volatile plasticizer is pressed into the molten resin mixture so as to be 30 parts by weight with respect to 100 parts by weight of the molten resin mixture. Was adjusted to 110 ° C. to obtain a resin melt for forming a resin layer.

  Supply the resin melt for forming the foam layer and the resin melt for forming the resin layer obtained above into the joining die, and in order resin melt for forming the resin layer / resin melt for forming the foam layer / resin melt for forming the resin layer For packaging according to the present invention, a cylindrical extruded foam is taken out along a cooling cylinder, cut out and cut and opened, and a resin layer is laminated and bonded to both sides of the foamed layer. A foam sheet was obtained.

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet for packaging. The basis weight B is the basis weight of the resin layer per one side. The average thickness was obtained by dividing the basis weight B by the density of the resin layer (the load average value of the density of the polyolefin resin and the density of the filler) and converting the unit to [μm].

  The basis weight of the packaging foam sheet was adjusted by adjusting the discharge amount of the resin melt for forming the resin layer and the take-up speed of the packaging foam sheet.

  In addition, 10.8 parts by weight of talc (trade name “High Filler # 12” manufactured by Matsumura Sangyo Co., Ltd.) and 5.9 parts by weight of sodium citrate are added to 100 parts by weight of low density polyethylene. An air conditioner master batch was used.

  The average particle diameter of the filler is the average of the particle diameter when the cumulative volume reaches 50% (volume average particle diameter: d50) using a laser diffraction particle size distribution analyzer: SALD-2100 manufactured by Shimadzu Corporation. The particle diameter was taken.

[Example 2]
In Example 1, the thickness of the packaging foam sheet and 1.02 mm, except that the basis weight of the resin layer was 0.9 g / m ² was obtained by packaging foam sheet according to the present invention in the same manner as in Example 1 .

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet for packaging.

[Example 3]
In Example 1, the thickness of the packaging foam sheet was 1.08 mm, and calcium carbonate (trade name “White SB Blue” manufactured by Shiroishi Calcium Co., Ltd .: average particle size 4.7 μm) was used instead of talc as a filler. A packaging foam sheet according to the present invention was obtained in the same manner as in Example 1 except that the basis weight of the resin layer was 0.9 g / m ² .

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet for packaging.

[Example 4]
In Example 1, the thickness of the foam sheet for packaging is 1.08 mm, the resin layer forming resin is a linear low density polyethylene resin (flexural modulus 420 MPa, MFR: 3 g / 10 min) manufactured by Sumitomo Chemical Co., Ltd. and a filler. Example except that calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd .: trade name “White SB Blue”; average particle size 4.7 μm) was used instead of talc, and the basis weight of the resin layer was 0.9 g / m ^2. In the same manner as in No. 1, a foam sheet for packaging according to the present invention was obtained.

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet for packaging.

[Example 5]
In Example 1, the thickness of the packaging foam sheet is 2.05 mm, and calcium carbonate (manufactured by Shiroishi Calcium Co., Ltd .: trade name “BF300”; average particle size 21.7 μm) is used instead of talc as a filler. A packaging foam sheet according to the present invention was obtained in the same manner as in Example 1 except that the basis weight of the layer was 4.5 g / m ² .

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet for packaging.

[Comparative Example 1]
In Example 1, the thickness of the packaging foam sheet was 1.06 mm, and a packaging foam sheet for comparison was obtained in the same manner as in Example 1 except that no filler was added to the resin layer.

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet for packaging.

[Comparative Example 2]
In Example 1, the thickness of the foam sheet for packaging was 1.03 mm, and calcium carbonate (manufactured by Shiroishi Calcium Co., Ltd .: trade name “BF300”; average particle size 2.1 μm) was used instead of talc as a filler. Obtained a foamed sheet for packaging of Comparative Example in the same manner as in Example 1.

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet.

[Comparative Example 3]
In Example 1, the thickness of the packaging foam sheet was 2.08 mm, and calcium carbonate (manufactured by Shiroishi Calcium Co., Ltd .: trade name “Softon”; average particle diameter 2.1 μm) was used instead of talc as a filler. A foamed sheet for packaging of a comparative example was obtained in the same manner as in Example 1 except that the amount was 4.5 g / m ² .

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet for packaging.

[Comparative Example 4]
In Example 1, except that the polyethylene resin as the resin layer forming resin was replaced with a polyethylene resin having a flexural modulus of 820 MPa (manufactured by Nippon Polyethylene Co., Ltd .: trade name “NOVATEC HJ362N; MFR: 5.0 g / 10 min). In the same manner as in Example 1, a packaging foam sheet for comparison was obtained.

  Tables 1 and 2 show the apparent density, thickness, base resin elastic modulus of the resin layer, average particle diameter D, basis weight B, average thickness, and D / B of the foamed sheet for packaging.

[Evaluation test as packaging material]
Next, the electrostatic friction coefficient was measured about the foaming sheet for packaging of the said Examples 1-5 and Comparative Examples 1-4. Moreover, the characteristic as a packaging material was evaluated from the viewpoint of buffering property, scratch prevention performance and scratch prevention performance. The results are shown in Table 2.

The evaluation method and evaluation criteria were as follows.
< Static friction coefficient >
In accordance with the tilt method defined in JIS P 8147, a static friction coefficient measuring machine “TYPE: HEIDON-10” manufactured by Shinto Kagaku Co., Ltd. is used, and an evaluation sample is fixed to a flat indenter (200 g, 35 mm × 70 mm). The coefficient of static friction was measured by switching the changeover switch to 8 mm / sec. In addition, this static friction coefficient is a static friction coefficient with respect to the flat stainless steel plate (SUS304) surface where the surface is smooth.
< Buffer properties >
A weight of 200 g was hung on a polypropylene plate (size: 100 mm × 150 mm) packaged with an evaluation sample, dropped from a height of 500 mm, and the cushioning performance of the foamed sheet for packaging was evaluated based on the presence or absence of dent scratches.

○: No dent scratch ×: There is a dent scratch < Scratch prevention performance >
Made by Nippon Rigaku Kogyo Co., Ltd .: With a cabinet-type wear tester, the evaluation sample was placed on a polypropylene plate (size: 50 mm × 55 mm), and a load of 10 gf / cm ² was applied, the reciprocating width distance was 10 mm, and the reciprocating number was 100 times. The abrasion test was performed under the conditions, and the scratch-proof performance of the packaging foam sheet was evaluated based on the surface abrasion state of the polypropylene plate after the test.

○: No scratches ×: There are scratches < surface properties of the package >
The surface of a polypropylene plate (size: 65 mm × 115 mm) was coated in the order of acrylic primer / acrylic paint / urethane clear, and dried at 23 ° C. for 48 hours. Immediately after drying, an evaluation sample was placed on the painted surface of the polypropylene plate, and a load of 24 gf / cm ² was evenly applied thereon, left in an oven at 60 ° C. for 120 hours, the evaluation sample was removed, and the evaluation sample was removed. The painted surface of the polypropylene plate was wiped and washed with ethanol, and the surface state was visually observed.

○: No surface pattern ×: With surface pattern

DESCRIPTION OF SYMBOLS 1 Foam sheet for packaging 2 Polyolefin resin foam layer 3 Polyolefin resin layer A 1st extruder B 2nd extruder 11 Resin for foam layer formation 12 Resin for resin layer formation 13 Foaming agent injection hole

Claims (7)

A foamed sheet for packaging having a thickness of 0.3 to 5 mm, wherein a resin layer having a polyolefin resin as a base resin is laminated on at least one surface of the polyolefin resin foam layer by coextrusion,
The flexural modulus of the polyolefin resin that is the base resin of the resin layer is 600 MPa or less, and 5 to 40% by weight of a filler having an average particle diameter of 2 to 50 μm is dispersed and blended in the resin layer. basis weight of 0.5 to 10 g / ^{m 2,} and the basis weight of the resin layer (B) the average particle size of the filler with respect to ^{[g / m 2] (D} ) the ratio of [μm] (D / B) Is a foamed sheet for packaging, characterized by being 1-12.   The foaming sheet for packaging according to claim 1, wherein the static friction coefficient of the resin layer surface is 0.5 or more.   The foamed sheet for packaging according to claim 1 or 2, wherein the polyolefin resin which is a base resin of the resin layer is low density polyethylene.   The foamed sheet for packaging according to any one of claims 1 to 3, wherein the polyolefin resin forming the foamed layer is low-density polyethylene. The apparent density of the packaging foam sheet is 15 to 90 kg / m ³ , The packaging foam sheet according to any one of claims 1 to 4,   The foaming sheet for packaging according to any one of claims 1 to 5, wherein the filler is talc.   The packaging foam sheet according to any one of claims 1 to 5, wherein the filler is calcium carbonate.

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