TW202035163A - Packing sheet - Google Patents

Abstract

An objective of the present invention is to provide a packing sheet in which migration of components to an article to be packaged is little and which has excellent antistatic properties. As a solution, the packing sheet of the present invention is provided with a polyolefin resin foam sheet containing a donor-acceptor type antistatic agent.

Description

Packaging tablets

The present invention relates to a packaging sheet, and it relates to a packaging sheet provided with a polyolefin-based resin foamed sheet.

In the past, compared with polystyrene-based resin foamed sheets, polyester-based resin foamed sheets, etc., polyolefin-based resin foamed sheets are softer and have excellent cushioning properties, and thus are widely used as packaging sheets and the like.

As such a packaging sheet, a single sheet of a polyolefin-based resin foamed sheet, a laminated sheet obtained by laminating a surface decorative sheet on a polyolefin-based resin foamed sheet, and the like are known.

As the object to be packaged with such a packaging sheet, electrical equipment and electronic equipment, or components for electrical equipment and electronic equipment, etc. are known.

The purpose of the packaging sheet is to protect the packaged objects from shocks during storage or transportation. It is also used as an intermediary when storing components such as glass plates, semiconductor substrates, and metal plates that are the substrates of flat-panel display panels. Spacers between components, etc.

In order to avoid the occurrence of adhesions on the packaging object due to static electricity, antistatic properties are required for such packaging sheets.

As a method for making a polyolefin resin foam sheet exhibit antistatic properties, there is known a polymer type antistatic agent called a polymer type antistatic agent or a so-called low molecular weight antistatic agent in the forming material of the polyolefin resin foam sheet. The method of surfactant type antistatic agent.

Among them, the surfactant exhibits antistatic properties by exuding to the surface of the sheet, and therefore it is easy to adhere to the surface of the object to be protected (see Patent Document 1 below). On the other hand, polymer-type antistatic agents contain metal ions in many cases, and there is a concern that the metal ions migrate to such packaging materials to cause adverse effects.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2010-42556 A

As described above, the packaging sheet is required to exhibit antistatic properties and have less migration of components to the packaging, but such a demand has not been met.

Therefore, the subject of the present invention is to provide a packaging sheet that has less migration of components to the packaging material and excellent antistatic properties.

As a result of detailed studies to solve the above-mentioned problems, the inventors of the present case discovered that the polyolefin resin foamed sheet containing the donor/acceptor type antistatic agent exhibits excellent antistatic properties and is unlikely to cause migration or exudation of metal ions. Further completed the present invention.

That is, in order to solve the above-mentioned problems, the present invention provides a packaging sheet comprising a polyolefin resin foamed sheet containing a donor/acceptor type antistatic agent, and the polyolefin resin foamed sheet has at least one Exposed on the surface.

In the polyolefin-based resin foam sheet containing the donor/acceptor type antistatic agent, by coexisting donors such as borides and acceptors such as nitrides, the diffusion of holes and the diffusion of electrons proceed rapidly. Even if the action of metal ions such as sodium ion or lithium ion is not used, it can still exert good antistatic properties.

In addition, the polyolefin-based resin foam sheet containing the donor/acceptor type antistatic agent can exhibit good antistatic properties even if it does not contain a compound that causes bleeding, such as a surfactant.

Therefore, the packaging sheet provided in such a way that the polyolefin resin foamed sheet is exposed on at least one surface can suppress the migration of components to the packaged object while exhibiting excellent antistatic properties.

1: Polyolefin resin foam sheet

1a: side 1

1b: Side 2

2: glass plate

10: Laminated body

11, 12: Coating film

100: Packing bag

100a: front film

100b: reverse sheet

101: Sealing part

102: opening

X1: Printed circuit board

Figure 1 is a schematic diagram showing a usage pattern of the packaging sheet.

Figure 2 is a schematic cross-sectional view of a packaging sheet according to an embodiment of the present invention.

Fig. 3 is a schematic diagram showing another embodiment of the packaging sheet.

The packaging sheet of the present invention will be described.

Hereinafter, a case where the packaging sheet is a single-layer sheet composed only of a polyolefin-based resin foamed sheet and both the front and back sides are composed of a polyolefin-based resin foamed sheet is taken as an example to describe the embodiment of the present invention.

In addition, the case where the polyolefin resin foamed sheet is an extruded foam is exemplified below.

In more detail, the following exemplifies a packaging sheet comprising a "polyolefin resin foam sheet formed by extrusion foaming a polyolefin resin composition containing a polyolefin resin" as an electronic component The use of the spacer paper for the bag or the glass plate, on the one hand, illustrates the embodiment of the present invention.

Fig. 1 shows a state in which the packaging sheet of the present embodiment is used as a constituent material of the packaging bag 100 for storing the printed circuit board X1.

The aforementioned packaging bag 100 of this embodiment is composed of two packaging sheets, a rectangular front sheet 100a and a back sheet 100b having a larger area than the printed circuit board X1.

The packaging bag 100 of this embodiment is formed by three-side sealing a laminated product in which the front sheet 100a and the back sheet 100b are overlapped in such a way that the outlines are aligned.

That is, the aforementioned packaging bag 100 has a sealing portion 101 that adheres to each other along three of the four sides of the front sheet 100a and the back sheet 100b, and the portion along the remaining side is not adhered. Place the opening 102 of the aforementioned printed circuit board X1.

In the aforementioned packaging bag 100, the front sheet 100a and the back sheet 100b may be composed of the same sheet or different sheets.

In the aforementioned packaging bag 100 of this embodiment, both the front sheet 100a and the back sheet 100b are formed by the same polyolefin resin foam sheet 1.

Fig. 2 shows the cross-sectional shape of the polyolefin resin foamed sheet used as the front sheet 100a and the back sheet 100b in this embodiment.

As shown in the figure, the polyolefin-based resin foam sheet 1 of this embodiment has a first side 1a that forms the inner side of the packaging bag 100 and is in contact with the aforementioned printed circuit board X1, and a first side 1a that forms the outer side of the packaging bag 100 The second side 1b.

The polyolefin resin foamed sheet 1 of this embodiment is composed of a polyolefin resin as a matrix polymer and a polyolefin resin composition containing an antistatic agent.

Examples of the polyolefin resin contained in the polyolefin resin foamed sheet 1 of the present embodiment include polyethylene resin, polypropylene resin, and ethylene-α olefin resin.

The polyolefin-based resin composition constituting the polyolefin-based resin foamed sheet does not need to contain one type of polyolefin-based resin alone, and may contain two or more types.

The polyolefin resin contained in the polyolefin resin composition is preferably a polypropylene resin.

The aforementioned polypropylene resin may be a homopolypropylene (hPP) which is a single polymer of propylene, or a copolymer containing a small amount of ethylene or butene-1 in addition to propylene.

The three-dimensional structure regularity of the polypropylene resin is not particularly limited, and it may be any of in-line polypropylene (iPP), para-propylene (sPP), hetero-polypropylene (aPP), and the like.

The aforementioned copolymer may also be random polypropylene (rPP) obtained by random copolymerization of propylene and ethylene.

The aforementioned copolymer may also be the following block polypropylene (bPP): ethylene is introduced in the late stage of the polymerization reaction of propylene, whereby the propylene-ethylene copolymer is dispersed in the homopolypropylene in a domain phase. In the matrix phase.

The aforementioned block polypropylene may be an elastic substance containing a propylene-ethylene copolymer in a content of 40% by mass or more, or may be a so-called olefin-based thermoplastic elastomer (TPO) or the like.

The above-mentioned polypropylene resin may be a long-chain branch formed by chemical crosslinking or electron beam crosslinking, or so-called high melt tension polypropylene (HMS-PP) or the like.

The polypropylene resin contained in the polyolefin resin foamed sheet 1 is preferably block polypropylene (bPP) or high melt tension polypropylene (HMS-PP), and it is preferable to use a mixture of the two.

The mass ratio of block polypropylene (bPP) to high melt tension polypropylene (HMS-PP) (bPP/(bPP+HMS-PP)) is preferably 20% by mass or more, more preferably 30% by mass or more. Preferably, it is 40% by mass or more.

The aforementioned mass ratio (bPP/(bPP+HMS-PP)) is preferably 80% by mass or less, more preferably 70% by mass or less, and particularly preferably 60% by mass or less.

The high melt tension polypropylene preferably exhibits a melt tension of 3 cN or more at 230°C. The aforementioned melt tension is preferably 4 cN or more, particularly preferably 5 cN or more. The aforementioned melt tension is preferably 30 cN or less, more preferably 28 cN or less.

The aforementioned melt tension can be obtained, for example, by the following method.

(Melting tension measurement method)

The sample is used as it is when the measurement object is pellets, and when the measurement object is a polyolefin resin foamed sheet, etc., a pelletizer (for example, "HAND TRUDER" manufactured by Toyo Seiki Seisakusho Co., Ltd. Type PM-1") The polyolefin-based resin foamed sheet was pelletized under the conditions of a cylinder temperature of 220°C and a standby time of 2.5 minutes from filling the sample to the start of extrusion.

The melt tension was measured using a Twin-bore Capillary Rheometer Rheologic 5000T (manufactured by Chiast, Italy).

Specifically, a 15mm diameter cylinder heated to the test temperature is filled with the measurement sample resin, and after preheating for 5 minutes, from the capillary die of the measuring device (bore diameter 2.0mm, length 20mm, flat inflow angle), make the piston The descending speed (0.1546mm/s) is kept constant, while extruding into a ribbon shape, the ribbon is passed through a tension detection pulley 27cm below the capillary mold, and then a winding roller is used to set the initial speed at 8.7mm/s. The acceleration of 12mm/s ² gradually increases the winding speed while winding, and the average of the maximum value and the minimum value immediately before the ribbon is cut is used as the melt tension of the sample.

In addition, when there is only one maximum point in the tension trace, the maximum value is used as the melt tension.

As a preferable polyolefin resin contained in the polyolefin resin composition, in addition to the above-mentioned polypropylene resin, a low density polyethylene resin can be cited.

Examples of the aforementioned low-density polyethylene resin include linear low-density polyethylene resin (LLDPE) polymerized by a medium-low pressure method, or low-density polyethylene having long-chain branches formed in a molecular structure by a high-pressure method. Resin (LDPE).

The low-density polyethylene resin (LDPE) preferably has a resin density of 910 kg/m ³ or more and 930 kg/m ³ or less.

The linear low-density polyethylene resin (LLDPE) preferably has a resin density of 910 kg/m ³ or more and 925 kg/m ³ or less.

The low density polyethylene resin (LDPE) or the linear low density polyethylene resin (LLDPE) preferably has a melt flow rate (hereinafter referred to as "MFR") of 1 g/10 min or more and 10 g/10 min or less.

The above-mentioned melt flow rate, unless otherwise specified in this specification, refers to the MFR of the polymer antistatic agent mentioned later, which is based on JIS K 7210: 1999 "Plastic-thermoplastic melt flow rate (MFR)" and melt volume flow Test method of rate (MVR)" The value measured by the method described in Method B (however, the test temperature is 190°C and the load is 21.18N).

The donor/acceptor type antistatic agent contained in the polyolefin resin composition together with the polyolefin resin may be, for example, a combination of an organic boride and a basic nitride.

As the aforementioned donor/acceptor type antistatic agent, one having excellent compatibility with polyolefin resin is preferred, and an alkyl chain having a certain length is preferred.

The aforementioned donor/acceptor type antistatic agent is preferably one represented by the following general formula (1).

In addition, "R ¹ "and "R ² " in the above formula (1) are independently "R ⁷ CO-OCH ₂ -" or "HOCH ₂ -", and at least one of them is "R ⁷ CO-OCH ₂ -""."R ³ "and "R ⁴ " in the above formula (1) are independently "CH ₃ -", "C ₂ H ₅ -", "HOCH ₂ -", "HOC ₂ H ₄ -" or "HOCH ₂ CH(CH ₃ ) ^- ". "R ⁵ "in the above formula (1) is "-C ₂ H ₄ -" or "-C ₃ H ₆ -". "R ⁶ "and "R ⁷ " in the above formula (1) are each independently an alkyl group having 11 to 21 carbon atoms.

In addition, as the aforementioned donor/acceptor type antistatic agent, one represented by the following general formula (2) may also be used.

In addition, "R ¹ "and "R ² " in the above formula (2) are independently "R ⁷ CO-OCH ₂ -" or "HOCH ₂ -", and at least one of them is "R ⁷ CO-OCH ₂ -""."R ³ "and "R ⁴ " in the above formula (2) are independently "CH ₃ -", "C ₂ H ₅ -", "HOCH ₂ -", "HOC ₂ H ₄ -" or "HOCH ₂ CH(CH ₃ )-". "R ⁵ "in the above formula (2) is "-C ₂ H ₄ -" or "-C ₃ H ₆ -". "R ⁶ "and "R ⁷ " in the above formula (2) are each independently an alkyl group having 11 to 21 carbon atoms.

In the aforementioned general formulas (1) and (2), the organoboride portion in the upper stage becomes the donor, and the basic nitrogen in the lower stage becomes the acceptor.

In addition, "(-)" in the aforementioned donor means that the electron withdrawing property of the boron atom becomes stronger, and "(+)" means that the electron donating property of the oxygen atom becomes stronger.

In addition, "→" in the aforementioned donor body indicates a path through which electrons are adsorbed, and "---" indicates a state where the bonding force between atoms is weakened.

Furthermore, "δ+" indicates that the covalent bond has polarity.

In addition, as the above-mentioned general formulas (1) and (2), as the donor/acceptor type antistatic agent in this embodiment, it is preferable to use the molecular formula "C ₄₂ H ₈₁ O ₈ B The combination of the organic boride represented by "" and the basic nitride represented by the molecular formula "C ₂₃ H ₄₈ ON ₂ ", or the organic boride represented by the molecular formula "C ₄₂ H ₈₁ O ₈ B" and the molecular formula "C ₂₃ H ₄₇ A combination of basic nitrides represented by "O ₂ N".

Regarding the content of the donor/acceptor type antistatic agent in the polyolefin resin composition, when the total amount of all polyolefin resins contained in the polyolefin resin composition is 100 parts by mass , Preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and still more preferably 0.3 parts by mass or more.

Regarding the content of the donor/acceptor type antistatic agent in the polyolefin resin composition, when the total amount of all polyolefin resins contained in the polyolefin resin composition is 100 parts by mass , Preferably 3.0 parts by mass or less, more preferably 2.8 parts by mass or less, and still more preferably 2.6 parts by mass or less.

The polyolefin resin foam sheet 1 of this embodiment is manufactured by an extrusion foaming method. Therefore, among the aforementioned polyolefin resin compositions used in the extrusion foaming method, in addition to the previous In addition to the above-mentioned ingredients, it may further contain ingredients required for foaming.

Examples of components used for this foaming include foaming agents and bubble regulators.

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

Among them, as the aforementioned blowing agent, a mixed butane of isobutane and n-butane is preferred.

In this way, if a mixed butane of isobutane/n-butane is used, isobutane is used to suppress the rapid escape of the blowing agent during the extrusion step.

On the other hand, n-butane, which is excellent in compatibility with polyolefin-based resins, suppresses an increase in the open cell ratio, and therefore can obtain a polyolefin-based resin foamed sheet 1 with less shrinkage, low open cell ratio, and excellent cushioning properties.

In addition, although the amount of foaming agent used in extrusion foaming is also related to the required degree of foaming, it is usually 5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the polyolefin resin.

Generally, the addition ratio of the blowing agent is set in such a range, because if the blowing agent is less than 5 parts by mass, it may be difficult to obtain sufficient foaming, and if it exceeds 25 parts by mass, the bubble film may burst and a good polymerization may not be obtained. Olefin resin foam sheet.

In addition, as the aforementioned bubble regulator for regulating the bubbles formed by the foaming agent, inorganic powders such as talc and silica can be cited. A mixture of polyvalent carboxylic acid and sodium carbonate or sodium bicarbonate (sodium bicarbonate), azodicarboxylate, etc., used as a decomposable blowing agent can also be used as the aforementioned bubble regulator.

These can be used singly or in combination. The addition amount of this air bubble regulator is preferably 0.5 parts by mass or less per 100 parts by mass of the polyolefin resin.

In addition to the above-mentioned components, the polyolefin-based resin foamed sheet 1 of the present embodiment may contain additives such as heat stabilizers, ultraviolet absorbers, antioxidants, and colorants as required.

In addition to the polyolefin resin and the donor/acceptor type antistatic agent, the ratio of other components contained in the polyolefin resin foam sheet 1 is preferably 10% by mass or less, more preferably 5% by mass or less .

That is, the total ratio of the polyolefin resin and the donor/acceptor type antistatic agent in the polyolefin resin composition constituting the polyolefin resin foam sheet 1 is preferably 90% by mass or more, more preferably 95% by mass. Above mass%.

The density (apparent density) of the polyolefin-based resin foamed sheet 1 composed of the above-mentioned polyolefin-based resin composition is not particularly limited, as long as it can exhibit the generally required cushioning properties, usually less than 150kg/m ³ , Preferably 100 kg/m ³ or less, particularly preferably 70 kg/m ³ or less.

Such a density is preferably selected because by making the density below the upper limit, the polyolefin resin foamed sheet 1 can be reliably imparted with excellent flexibility and cushioning properties, and by setting the density above the lower limit, the polyolefin resin The foam sheet 1 exhibits excellent strength.

From this point of view, the density of the polyolefin-based resin foamed sheet 1 is preferably 10 kg/m ³ or more, more preferably 15 kg/m ³ or more.

The density of the polyolefin resin foam sheet 1 was measured in accordance with the method described in JIS K7222: 1999 "Foamed Plastics and Rubber-Apparent Density Measurement", and specifically measured by the following method.

(Density measurement method)

From the polyolefin-based resin foam sheet, a sample of 100 cm ³ or more is prepared, and the size and mass of the sample are measured after the state is adjusted for 16 hours under the 23/50 of JIS K7100: 1999 and Class 2 environment. The following formula calculates the apparent density.

Apparent density (g/cm ³ ) = sample mass (g) / sample volume (cm ³ )

In addition, regarding the size measurement of the sample, for example, the "DIGIMATIC" CD-15 type manufactured by Mitutoyo Corporation can be used.

The thickness of the aforementioned polyolefin resin foamed sheet is preferably 0.1 mm or more, more preferably 0.15 mm or more, and still more preferably 0.3 mm or more.

The thickness of the aforementioned polyolefin resin foamed sheet is preferably 6 mm or less, more preferably 5 mm or less, and still more preferably 4 mm or less.

The thickness of the polyolefin-based resin foamed sheet 1 can be, for example, the average value of the thickness measured at 10 or more measurement points selected at random.

The basis weight of the aforementioned polyolefin resin foamed sheet is preferably 10 g/m ² or more, more preferably 15 g/m ² or more, and still more preferably 25 g/m ² or more.

The basis weight of the aforementioned polyolefin resin foamed sheet is preferably 600 g/m ² or less, more preferably 500 g/m ² or less, and still more preferably 400 g/m ² or less.

The basis weight of the aforementioned polyolefin resin foamed sheet can be measured according to the method described in JIS P8124:2011 "Paper and Cardboard-Basis Weight Measurement Method".

Specifically, 10 pieces of 100 cm ² or more samples can be cut out, and each mass and area can be measured, and the following formula can be used to obtain.

Basis weight (g/m ² )=10000×test piece mass (g)/test single area (cm ² )

Regarding the aforementioned polyolefin resin foamed sheet, the amount of exudation in at least the first surface 1a (the surface in contact with the packaged object) is preferably 0.3% by mass or less, and the amount of exudation is more preferably 0.2% by mass or less. The best amount is below 0.1% by mass.

The amount of exudation of the aforementioned polyolefin resin foamed sheet can be obtained by the following method.

Cut the sample into a size of 100mm×100mm, and put the sample into a thicker sealed bag with a chain of 120mm×170mm.

Add 20ml of methanol into this sealed bag, try to exhaust air and close the zipper, shake the sealed bag about 100 times by hand.

After shaking, the zipper was opened, the methanol in the sealed bag was taken out to a beaker, and heated in a constant temperature bath at 105°C for 24 hours to evaporate the methanol to obtain a dry solid.

After that, put the beaker into a desiccator, let it cool in the desiccator, and measure the mass of the evaporated and dried solid after returning to normal temperature.

In addition, the measurement is carried out three times in principle using three samples cut out from different places.

Then, the average value of 3 measurements was taken as the amount of exudation of the aforementioned polyolefin resin foamed sheet.

In the polyolefin resin foamed sheet, the amount (total amount) of alkali metal ions and alkaline earth metal ions in at least the first surface 1a (the surface in contact with the packaged object) is preferably 2 mg/m ² or less.

The amount of alkali metal ions and alkaline earth metal ions in the first surface 1a is more preferably 1 mg/m ² or less, and still more preferably 0.5 mg/m ² or less.

The amount of alkali metal ions and alkaline earth metal ions in the aforementioned polyolefin resin foamed sheet can be obtained by the following method.

Cut the sample into a size of 100mm×100mm, and put the sample into a thicker sealed bag with a chain of 120mm×170mm.

Add 20ml of ion-exchange water to this sealed bag, try to remove air and close the zipper, keep it in a constant temperature bath at 60°C, after 30 minutes, shake the sealed bag 10 times by hand.

After another 30 minutes, the sealed bag was shaken by hand 10 times in the same manner, and the sealed bag was opened to take out the ion-exchanged water. Then, using a multifunctional ICP emission spectrometer (trade name "ICPE-9000", manufactured by Shimadzu Corporation), the amount of alkali metal ions and alkaline earth metal ions contained in the ion exchange water was measured under the following measurement conditions.

(Measurement conditions)

Observation direction: axial

Exposure time: 30 seconds

High frequency output: 1.20kW

Carrier flow rate: 0.7mL/min

Plasma flow rate: 10.0mL/min

Auxiliary flow rate: 0.6mL/min

In the polyolefin-based resin foam sheet, at least the surface resistivity of the first surface 1a (the surface in contact with the packaged object) is preferably a predetermined value after being wiped with ethanol.

Specifically, after wiping with ethanol, the surface resistivity of the polyolefin-based resin foamed sheet measured under the conditions of a temperature of 20°C and a relative humidity of 60%RH is preferably 1×10 ⁸ Ω or more, more preferably It is 1×10 ⁹ Ω or more, particularly preferably 1×10 ¹⁰ Ω or more.

The aforementioned surface resistivity is preferably 1×10 ¹² Ω or less, more preferably 1×10 ¹¹ Ω or less.

The surface resistivity can be measured according to the method described in JIS K6911: 1995 "General Test Methods for Thermosetting Plastics".

The test device (Advantest (stock) digital ultra-high resistance/micro current meter, model "R3840" and RESISTIVITY CHAMBER, model "R12702A") can be used to measure surface resistivity. The surface resistivity is calculated by pressing the electrode on a sample taken from a polyolefin resin foam sheet with a load of about 30N, charging it at 500V for 1 minute, measuring its resistance value, and calculating it by the following formula.

In addition, the sample has a width of 100 mm × a length of 100 mm × thickness (thickness of the polyolefin resin foam sheet itself).

The measurement is carried out after adjusting the state for more than 24 hours in an environment with a temperature of 20±2°C and a relative humidity of 65±5%RH. The test environment is a temperature of 20±2°C and a relative humidity of 65±5%RH.

The number of samples (n number) is 5, and in principle the front and back sides are measured separately.

In addition, the surface of the sample was wiped with ethanol after conditioning.

The wiping with ethanol was implemented in the following manner.

Wipe the entire measuring surface of the 100mm square sample after adjustment with a paper towel (for example, the product name "KimWipes") with a small amount of ethanol.

After the wiping, the surface resistivity was kept in a test environment for 1 hour and then implemented.

In addition, the surface resistivity of each sample was calculated by the following formula, and the measured values were calculated and averaged for all samples, and the average value was used as the surface resistivity of the polyolefin-based resin foamed sheet.

ρs=(π(D+d)/(D-d))×Rs

ρs: Surface resistivity (MΩ)

D: The inner diameter of the ring electrode on the surface (cm)

d: The outer diameter of the inner circle of the surface electrode (cm)

Rs: Surface resistance (MΩ)

The polyolefin-based resin foamed sheet 1 in this embodiment mode may contain a small amount of a polymer antistatic agent and a small amount of a surfactant within the range that exhibits the above-mentioned surface properties.

Examples of the aforementioned polymer type antistatic agent include: ionic polymerization of polyethylene oxide, polypropylene oxide, polyethylene glycol, polyester amide, polyether ester amide, ethylene-methacrylic acid copolymer, etc. Quaternary ammonium salts such as polyethylene glycol methacrylate copolymers, copolymers of olefin-based blocks and hydrophilic blocks described in JP 2001-278985 A, etc.

The content of the polymer antistatic agent in the polyolefin-based resin foam sheet is preferably 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less.

The polyolefin resin foamed sheet of this embodiment does not contain a polymer antistatic agent and is particularly preferred.

Examples of the aforementioned surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.

The content of the surfactant in the polyolefin-based resin foam sheet is preferably 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less.

The polyolefin-based resin foamed sheet of the present embodiment preferably does not contain a surfactant.

In the polyolefin-based resin foamed sheet 1 in this embodiment, it is preferable that not only the first surface 1a but also the second surface 1b has the surface properties as described above, in that it can be used without distinguishing the front and back.

However, since the aforementioned second surface 1b is not in contact with the printed circuit board X1 as the object to be packaged, the packaging sheet (front sheet 100a, back sheet 100b) of this embodiment may be made of polyolefin resin. Fiber sheet (paper, cloth, etc.), film (resin film, metal Films, composite films, etc.) and resin foam sheets that do not contain donor/acceptor type antistatic agents.

That is, the packaging sheet in this embodiment mode may be provided so as to expose the polyolefin resin foam sheet kneaded with the donor/acceptor type antistatic agent on at least one surface.

In the above description, although the use type of the packaging bag 100 as a packaging sheet is exemplified, the packaging sheet in this embodiment can also be used for other purposes.

Taking Fig. 3 as an example, another embodiment of the packaging sheet in this embodiment is described.

The packaging sheet shown in Figure 3 is a single-layer sheet composed of only the polyolefin-based resin foam sheet 1. When a plurality of glass plates 2 are laminated in the vertical direction to form a laminated body 10, it is regarded as intervening adjacent The spacer paper between the glass plates 2 is used.

The aforementioned glass plate 2 in this embodiment is a glass plate for flat display panels such as plasma display panels or liquid crystal display panels.

The packaging sheet constituting the packaging bag 100 is used in such a way that only one side of the two surfaces (first surface 1a) is in contact with the printed circuit board X1 as the object to be packaged, but the packaging shown in Figure 3 For the sheet, both the first surface 1a and the second surface 1b of the polyolefin-based resin foamed sheet 1 are the abutting surfaces of the glass plate 2 as the object to be packaged.

Therefore, the packaging sheet used in this embodiment preferably has a polyolefin-based resin foam sheet so that the polyolefin-based resin foam sheet kneaded with the donor/acceptor type antistatic agent is exposed on both surfaces. Resin foam sheet.

When the polyolefin-based resin foamed sheet is required to be exposed on both surfaces, the packaging sheet does not need to be composed of a single polyolefin-based resin foamed sheet 1. It can also be a combination of two polyolefin-based resin foamed sheets 1 directly or through A laminated sheet that is laminated in the state of other sheets.

That is, the packaging sheet may have a first surface layer provided on one side and a second surface layer provided on the other side, each made of a polyolefin resin foam sheet containing a donor/acceptor type antistatic agent. constitute The two-layer structure may also have a three-layer or more-layer structure with one or more intermediate layers between the first surface layer and the second surface layer, and the first surface layer and the The second surface layer is each composed of a polyolefin-based resin foam sheet containing a donor/acceptor type antistatic agent.

As mentioned above, when the packaging sheet has a plurality of polyolefin resin foam sheets, the thickness of a polyolefin resin foam sheet and other polyolefin resin foam sheets and the difference between the donor/acceptor type antistatic agent The content etc. may be the same or different.

As mentioned above, the polyolefin resin foamed sheet 1 is manufactured by the extrusion foaming method in this embodiment.

Specifically, the following extrusion steps can be carried out to produce the polyolefin resin foam sheet 1: from a circular die (Circular die) installed at the front end of the extruder, the aforementioned polyolefin resin composition is continuously extruded Make foam into a sheet to make extruded foam sheet.

In the extrusion step, since the donor/acceptor type antistatic agent shows affinity for the polyolefin resin, the donor/acceptor type antistatic agent becomes contained in the polyolefin resin foam sheet in a good dispersion state In the state.

Known antistatic agents include a coating type used for coating on the surface of a resin product, and a kneading type used for kneading the resin product.

As described above, in this embodiment, the donor/acceptor type antistatic agent is used as a kneading type antistatic agent.

The polyolefin-based resin foam sheet 1 kneaded with a donor/acceptor type antistatic agent not only exhibits excellent antistatic properties, but also has less migration of its components with respect to the contacting target material.

Then, in this extrusion step, the donor/acceptor type antistatic agent is prevented from oozing out to the surface of the polyolefin resin foamed sheet 1.

In the aforementioned extrusion step in this embodiment, the cylindrical foam continuously extruded from the circular mold is subjected to the first cooling and the second cooling. The first cooling is to blow from the inside and outside immediately after the extrusion. Cooling air is added for air cooling, and the second cooling system uses a cooling mandrel to further cool the air-cooled foam.

In the aforementioned extrusion step, the cylindrical foam is cut in the extrusion direction with a cutter provided on the downstream side of the cooling mandrel and taken out.

In the aforementioned extrusion step in this embodiment, a cooling mandrel with an outer diameter larger than the diameter of the circular mold is used for the second cooling.

Therefore, this second cooling is performed by sliding the outer peripheral surface of the cooling mandrel to the inner peripheral surface of the cylindrical foam that has undergone the first cooling.

In this second cooling, while cooling the cylindrical foam after the first cooling, the diameter is also expanded with the cooling mandrel at the same time.

As described above, the foam cut by a cutter in the extrusion direction is unrolled into a strip shape, and then wound to form the raw material roll.

In this embodiment, in order for the polyolefin resin foamed sheet 1 to exhibit excellent cushioning properties, the polyolefin resin contained in the polyolefin resin composition is the aforementioned high melt tension polypropylene (HMS-PP) With at least one of block polypropylene (bPP), it is preferable to use both, and it is preferable to make the polyolefin resin composition into a state in which the crystallinity is lower than that of homopolypropylene (hPP).

The ideal crystallization of polypropylene has a heat of fusion of 209J/g, and the degree of crystallinity of homopolypropylene (hPP) is usually 50% to 70%.

In view of the above, the degree of crystallinity of the aforementioned polyolefin resin composition is preferably 40% or less, more preferably 30% or less.

That is, the heat of crystallization of the polyolefin-based resin composition is preferably 83 J/g or less, more preferably 62 J/g or less.

The heat of crystallization of the polyolefin resin composition can be measured by the method described in JIS K7122: 2012 "Measuring Method of Heat of Transfer of Plastics".

Specifically, it can be obtained by the following method.

(Method for obtaining heat of crystallization)

Using a differential scanning calorimeter device (for example, manufactured by SII nanotechnology, model "DSC6220"), about 6 mg of sample is filled into the bottom of the aluminum measuring container in a gapless manner, and the nitrogen flow rate is 20 mL/min. After cooling from 30°C to -40°C, keep it for 10 minutes, increase from -40°C to 220°C (first heating), keep it for 10 minutes and then lower the temperature from 220°C to -40°C (cooling), keep it for 10 minutes, The temperature was increased from -40°C to 220°C (the second heating) to obtain the DSC curve.

In addition, all heating and cooling were performed at a rate of 10°C/min, and alumina was used as the reference material.

The aforementioned heat of crystallization is obtained from the area of the crystallization peak observed during the cooling process.

The heat of crystallization can be obtained by using the analysis software attached to the device. The part enclosed by the straight line connecting the point where the DSC curve departs from the reference line on the high temperature side and the point where the DSC curve returns to the reference line on the low temperature side and the DSC curve The area is calculated.

In this embodiment, in order to make the polyolefin resin foam sheet 1 exhibit excellent cushioning properties, the polyolefin resin foam sheet can also be rapidly cooled by the above-mentioned cooling air or cooling with a cooling mandrel. To below the crystallization temperature, the internal formation of polypropylene crystals is suppressed.

In addition, the crystallization of the polyolefin-based resin foamed sheet 1 is suppressed. This can be determined by the fact that the heat of fusion in the "first heating" in the operation for obtaining the heat of crystallization is lower than that in the "second heating" Confirm the obtained heat of fusion.

The ratio (Qm1/Qm2) of the heat of fusion (Qm1) in the "first heating" to the heat of fusion (Qm2) in the "second heating" of the polyolefin-based resin foam sheet 1 is preferably 0.9 or less.

The aforementioned ratio (Qm1/Qm2) is more preferably 0.8 or less.

The heat of fusion of the polyolefin-based resin foam sheet is the same as the heat of crystallization. It can be obtained using the analysis software attached to the device. It can be calculated from the point where the DSC curve is far from the reference line on the low temperature side and the DSC curve back to the high temperature side Calculate the area of the part enclosed by the straight line connecting the points of the reference line and the DSC curve.

In this embodiment, as described above, it is illustrated that the polyolefin-based resin foamed sheet can be easily adjusted to an ideal state as a packaging sheet, and the polyolefin-based resin foamed sheet is produced by extrusion foaming. However, the polyolefin-based resin foam sheet included in the packaging sheet of the present invention may be produced by other manufacturing methods.

In this embodiment, although the printed circuit board and glass plate are cited as the packaged objects packaged by the packaging sheet, as the aforementioned packaged objects, for example, silicon chips, hard disks, microprocessors, light-emitting diodes For electrical equipment such as body, sapphire chip, disc substrate, IC chip, magneto-optical disc (MO), DVD, BD, various memories, liquid crystal filter, magnetic resistance head for hard disc, CCD, reticle, etc. Components and components for electronic equipment are ideal.

In addition, the aforementioned packaged objects may also be so-called electrical equipment and electronic equipment such as computers, screens, video recorders, smartphones, and tablet computers in which these components are assembled.

That is, the use of the packaging sheet of the present invention is not particularly limited.

In addition, the packaging sheet of the present invention is not limited in any way with regard to matters other than the use due to the above-mentioned examples.

[Example]

Next, examples are given to explain the present invention in more detail, but the present invention is not limited to these.

(Example 1)

The first stage (upstream side) extruder is a single-shaft extruder with a diameter of 90mm, and the second stage (downstream side) is a single-axis extruder with a diameter of 115mm. The machine was used as an extruder to produce a polypropylene resin foam sheet.

The following formulation was prepared: 100 parts by mass of a mixed polypropylene resin containing high melt tension polypropylene (HMS-PP) and block polypropylene (bPP) in a mass ratio of 50:50 to 0.5 parts by mass A donor/acceptor type antistatic agent (a mixture of an organic boride and a basic nitride) is added, and a bubble regulator (talc-based bubble regulator) is added at a ratio of 0.2 parts by mass.

This formulation was fed to the hopper of the extruder with a caliber of 90 mm in the first stage, heated and melted at 200°C, and then 4 parts by mass relative to 100 parts by mass of the molten resin. In the middle of the extruder, butane (isobutane/n-butane=35/65) as a blowing agent was pressed in, and the extruder was used for melt kneading.

The kneaded mixture obtained by the melt kneading was supplied to the extruder in the second stage through the connecting pipe, and the temperature of the kneaded mixture was lowered to 170 while continuing the kneading inside the extruder. ℃.

In this way, the reduced temperature kneaded mixture was extruded from the circular slit of a circular die with a diameter of 140 mm and a slit gap of 0.95 mm connected to the tip of the extruder so that the extrusion volume was 98.5 kg/hour. It is made into a cylindrical shape in the atmosphere to foam the aforementioned kneaded product to form a cylindrical foam.

With the cooled mandrel (mandrel diameter: φ414mm, length: 500mm), the foam is drawn while expanding the diameter, and an air cooling ring is used to blow air on the outer surface of the foam to make the foam The foam was cooled, and the cooled foam was cut with a knife to produce a polyolefin resin foam sheet.

(Example 2)

Use low density polyethylene (LDPE) instead of mixed polypropylene resin, change the amount of donor/acceptor type antistatic agent from 0.5 parts by mass to 0.3 parts by mass, and change the extrusion conditions. 1 In the same manner, a polyolefin resin foamed sheet was produced.

(Example 3)

Except having changed the amount of the donor/acceptor type antistatic agent from 0.3 parts by mass to 2.0 parts by mass, the same procedure as in Example 2 was carried out to produce a polyolefin-based resin foam sheet.

(Comparative example 1)

Use a polymer type antistatic agent instead of the donor/acceptor type antistatic agent, and make the addition amount of the polymer type antistatic agent 8 parts by mass relative to 100 parts by mass of the mixed polypropylene resin. In addition, In the same manner as in Example 1, a polyolefin resin foamed sheet was produced.

(Comparative example 2)

Use surfactant (glyceryl monostearate) instead of donor/acceptor type antistatic agent, and make the amount of surfactant 1.5 parts by mass relative to 100 parts by mass of low-density polyethylene (LDPE). Except that, in the same manner as in Example 2, a polyolefin-based resin foam sheet was produced.

(Comparative example 3)

The surfactant was changed from glyceryl monostearate to alkyl diethanolamide, and the amount of surfactant was changed from 1.5 parts by mass to 3.4 parts by mass relative to 100 parts by mass of low-density polyethylene (LDPE). Otherwise, a polyolefin-based resin foam sheet was produced in the same manner as in Comparative Example 2.

The physical properties of the obtained polyolefin resin foamed sheet are as shown in the table.

(Property Evaluation Project)

Thickness: the thickness of the polyolefin resin foam sheet

Basis weight: Basis weight of polyolefin resin foamed sheet

Surface resistivity: The surface resistivity measured under the conditions of a temperature of 20°C and a relative humidity of 60%RH after wiping the surface of the polyolefin resin foam sheet with ethanol

Exudation amount: the amount of exudation on the surface of the polyolefin resin foamed sheet

Metal ion amount: the total amount of alkali metal ions and alkaline earth metal ions on the surface of the polyolefin resin foamed sheet

[Table 1]

From the above results, it can be seen that providing the packaging sheet with a polyolefin-based resin foam sheet containing a donor/acceptor type antistatic agent can effectively reduce the migration of components to the packaged object.

That is, as described above, it can be seen that the packaging sheet of the present invention has little migration of components to the packaged object and has excellent antistatic properties.

1: Polyolefin resin foam sheet

1a: side 1

1b: Side 2

100: Packing bag

100a: front film

100b: reverse sheet

101: Sealing part

102: opening

X1: Printed circuit board

Claims (3)

A packaging sheet is provided with a polyolefin resin foam sheet containing a donor/acceptor type antistatic agent, and the polyolefin resin foam sheet is exposed on at least one surface. The packaging sheet described in claim 1, wherein the content of the antistatic agent contained in the polyolefin resin foam sheet is relative to the polyolefin resin contained in the polyolefin resin foam sheet 100 parts by mass is 0.1 parts by mass or more and 3 parts by mass or less. The packaging sheet described in item 1 or 2 of the scope of patent application, wherein the thickness of the aforementioned polyolefin resin foamed sheet is 0.15 mm or more and 5 mm or less, and the basis weight is 15 g/m ² or more and 500 g/m ² or less, In the aforementioned surface of the polyolefin resin foamed sheet, The amount of exudation is 0.2% by mass or less, The amount of alkali metal ions and alkaline earth metal ions is 1 mg/m ² or less, and After wiping with ethanol, the surface resistivity measured under the conditions of a temperature of 20°C and a relative humidity of 60%RH is 1×10 ⁹ Ω or more and 1×10 ¹² Ω or less.

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