JP5339835B2 - Laminated foam sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated foam sheet which can appropriately be used as a sealing material for the purposes of dust prevention, heat insulation, sound insulation, shock absorption, watertightness, airtightness, etc., and is superior in fire retardancy. <P>SOLUTION: In the laminated foam sheet, a synthetic resin film is laminated/unified on/with at least one side of a foamed sheet having a 25% compressive strength of 30-200 kPa, and a polyimide resin layer is formed on the outer surface of the synthetic resin film. Since the foamed sheet has a proper compressive strength and excellent fire retardancy by the polyimide resin layer, it can appropriately be used as the sealing material under high-temperature conditions. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a laminated foam sheet that is excellent in flame retardancy and can be suitably used as a sealing material.

  Currently, foam is widely used as a sealing material in various fields such as architecture, civil engineering, electricity, electronics, and vehicles. Examples of the foam used for such a sealing material include a thermoplastic resin foam made of polyethylene resin, polypropylene resin, etc., a rubber foam made of synthetic rubber or natural rubber, and the like.

  Among seal materials, packing / gasket materials are used to fill gaps in various structures such as vehicles and light electricity, and serve as cushions against impacts while preventing dust from entering the structure. Used for.

  In particular, electrical products are required to have higher density, higher accuracy, smaller size, and lighter weight for the first time in mobile phones, and as a result, gaps for disposing sealing materials have been reduced, making it flexible and efficient. There is a demand for a sealing material that can be well disposed but exhibits high sealing performance after the disposition.

As such a sealing material, Patent Document 1 includes a foam having a hardness of 25% compression 0.08 to 0.3 kg / cm ² and a density of 0.3 to 0.5 g / cm ^3. A gasket comprising a base and a plastic film fixed to one side of the base has been proposed.

  However, the gasket has a problem that since the base made of foam has a low compressive strength, the base is deformed after punching into a desired shape, the dimensions do not match, and the sealing performance is poor. It was.

  In recent years, since the interior of a casing of an electrical product becomes hot during operation, the sealing material used in the casing is also required to have flame resistance.

JP 2001-100216 A

  The present invention provides a laminated foamed sheet that can be suitably used as a sealing material for the purpose of dustproofing, heat insulation, soundproofing, buffering, watertightness and airtightness, and is excellent in flame retardancy.

In the laminated foam sheet A of the present invention, a synthetic resin film is laminated and integrated on at least one surface of a foamed sheet having a 25% compression strength of 30 to 200 kPa, and a polyimide resin layer is laminated and integrated on the outer surface of the synthetic resin film. a laminated foam sheet formed by reduction, the thickness of the laminated foam sheet characterized in that it is a 0.1 to 1 mm.

  The foamed sheet 1 may have any cell structure of a closed cell foamed sheet, an open cell foamed sheet, or a foamed sheet formed by mixing closed cells and open cells as cells depending on the application. Good.

  The synthetic resin constituting the foam sheet 1 is not particularly limited as long as it is conventionally used for foams. For example, polyolefin resins such as polypropylene resins and polyethylene resins, polyurethanes, etc. Resin, polyvinyl chloride resin, polyamide elastomer, polystyrene elastomer and other thermoplastic elastomers, and polyvinyl acetate. A polyolefin-based resin is preferable, and a polypropylene-based resin and a polyethylene-based resin are more preferable because it is easy to produce a closed-cell foamed sheet having a compressive strength required when a laminated foamed sheet is used.

  The polypropylene-based resin is not particularly limited, and examples thereof include a propylene homopolymer and a copolymer of propylene and another olefin. Polypropylene resins may be used alone or in combination of two or more. Further, the copolymer of propylene and other olefins may be any of a block copolymer, a random copolymer, and a random block copolymer.

  Examples of the olefin copolymerized with propylene include α such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene and 1-decene. -Olefins.

  The polyethylene-based resin is not particularly limited. For example, a low-density polyethylene-based resin, a medium-density polyethylene-based resin, a high-density polyethylene-based resin, a linear low-density polyethylene-based resin, or a linear medium-density polyethylene-based resin. Examples thereof include a resin and a linear high-density polyethylene resin. Polyethylene resins may be used alone or in combination.

  Further, the polyethylene resin preferably contains a polyethylene resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. In the polyolefin resin, the content of the polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst is preferably 40% by weight or more, more preferably 50% by weight or more, and 60% by weight. The above is particularly preferable, and 100% by weight is most preferable. The content of the polyethylene resin obtained using the metallocene compound of 100% by weight means that only the polyethylene resin obtained using the metallocene compound is used as the polyolefin resin.

  The reason why the content of the polyethylene resin obtained using the metallocene compound in the polyolefin resin is preferably 40% by weight or more will be described. The first reason is as follows.

  As will be described later, the foam sheet 1 is manufactured by stretching the foam sheet in a predetermined direction while foaming or under heating. When the foam sheet is stretched, the foam sheet is expanded in the stretching direction so that the cell walls are close to each other. Therefore, a resin having adhesiveness to the polyolefin resin (for example, ethylene-vinyl acetate copolymer) When coalescence is used, the cell walls may be closely integrated with each other, and a foam sheet having a desired range of 25% compression strength may not be obtained.

  On the other hand, the foamed sheet 1 of the present invention is required to have flexibility. Therefore, by using a polyolefin resin containing 40% by weight or more of a polyethylene resin obtained by using the above metallocene compound, the polyolefin resin is imparted with flexibility without increasing the adhesiveness, and sealed. A foam sheet having a 25% compressive strength suitable as a material can be obtained.

  The second reason is as follows. The polyethylene resin obtained by using the above metallocene compound has a narrow molecular weight distribution, and in the case of a copolymer, the copolymer component is introduced into each molecular weight component at a substantially equal ratio. Therefore, the foamed sheet can be uniformly crosslinked. And since the foam sheet is uniformly cross-linked, the foam sheet can be stretched uniformly, and the thickness of the resulting foam sheet is made uniform as a whole, and the sealing performance when used as a sealing material is ensured. Can be.

  As a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as the polymerization catalyst, using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, ethylene and a small amount of an α-olefin are obtained. A linear low density polyethylene obtained by copolymerization is preferred.

  Examples of the α-olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene.

  The metallocene compound generally refers to a compound having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds, and a bis (cyclopentadienyl) metal complex is typical.

  As the metallocene compound containing a tetravalent transition metal in the present invention, specifically, a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, platinum or the like is added to one or more cyclopentadidienes. Examples thereof include compounds in which an enyl ring or an analog thereof is present as a ligand (ligand).

  Examples of the ligand include a cyclopentadienyl ring; a cyclopentadienyl ring substituted with a hydrocarbon group, a substituted hydrocarbon group, or a hydrocarbon-substituted metalloid group; a cyclopentadienyl oligomer ring; an indenyl ring; And an indenyl ring substituted by a group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group. In addition to these π-electron unsaturated compounds, as ligands, monovalent anion ligands such as chlorine and bromine or divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, arylamides, A phosphide, an aryl phosphide or the like may be coordinated to the transition metal atom.

  Furthermore, examples of the hydrocarbon group substituted on the cyclopentadienyl ring include methyl group, ethyl group, propyl group, butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, 2-ethylhexyl group, heptyl group, Examples include an octyl group, a nonyl group, a decyl group, a cetyl group, and a phenyl group.

  Examples of such metallocene compounds containing tetravalent transition metals include cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, Dimethylsilyltetramethylcyclopentadienyl-t-butylamidozirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-t-butylamidohafnium dichloride, dimethylsilyltetramethylcyclopentadienyl-pn-butylphenylamidozirconium chloride , Methylphenylsilyltetramethylcyclopentadienyl-t-butylamido hafnium dichloride, indenyl titanium tris (dimethylamide), indenyl titanium tri (Diethylamide), indenyl titanium tris (di -n- propyl amide), indenyl titanium bis (di -n- butylamide) (di -n- propyl amide) and the like.

  The metallocene compound exhibits an action as a catalyst in the polymerization of various olefins by changing the kind of metal and the structure of the ligand and combining with a specific cocatalyst (co-catalyst). Specifically, the polymerization is usually performed in a catalyst system in which methylaluminoxane (MAO), a boron-based compound or the like is added to these metallocene compounds as a cocatalyst. In addition, the use ratio of the cocatalyst with respect to the metallocene compound is preferably 10 to 1,000,000 mole times, and more preferably 50 to 5,000 mole times.

The polymerization method of the polyethylene resin is not particularly limited, and examples thereof include a solution polymerization method using an inert medium, a bulk polymerization method substantially free of an inert medium, and a gas phase polymerization method. The polymerization temperature is usually from −100 ° C. to 300 ° C., and the polymerization pressure is usually from normal pressure to 100 kg / cm ² .

  Since the metallocene compound has uniform properties of active sites and each active site has the same activity, the uniformity of the molecular weight, molecular weight distribution, composition, composition distribution, etc. of the polymer to be synthesized is increased. Therefore, the polyolefin resin polymerized using these metallocene compounds as a polymerization catalyst has a narrow molecular weight distribution, and in the case of a copolymer, the copolymer component is introduced in almost equal proportion to any molecular weight component. Have

  The foamed sheet 1 contains a large number of bubbles (hereinafter referred to as “stretched cells”) that are stretched in a direction orthogonal to the thickness direction thereof, that is, in the in-plane direction of the foamed sheet 1. The directions are oriented in the same direction. The stretch direction of the stretched bubbles refers to a linear direction connecting two points where the bubbles have the longest diameter, and the same stretch direction assumes a straight line parallel to the stretch direction of each stretched bubble, The angle formed by these straight lines is 0 to 45 °.

  In addition, when the bubbles of the foam sheet 1 are stretched in all directions orthogonal to the thickness direction to form a meteorite, that is, when the bubbles are cut at any position in the direction orthogonal to the thickness direction of the foam sheet, any cutting is performed. When the surface also has a perfect circle shape and any of the cut surfaces has an elliptical shape when the foamed sheet is cut in the thickness direction, an arbitrary direction orthogonal to the thickness direction of the foamed sheet may be set as the stretching direction.

  By taking such a cell structure, the foam sheet 1 has an appropriate restoring elastic force despite having excellent flexibility, and when the laminated foam sheet A is used as a sealing material, It excels in workability when disposed in a predetermined gap and exhibits excellent sealing performance.

  When the ratio of the stretched cells in the bubbles of the foamed sheet 1 is small, the flexibility of the foamed sheet becomes insufficient, and the workability when disposed at a predetermined position when the laminated foamed sheet is used as a sealing material is lowered. Therefore, 50% or more is preferable, and 70 to 100% is more preferable.

  The ratio of stretched bubbles in the bubbles of the foam sheet 1 is measured in the following manner. The foam sheet 1 is cut over the entire thickness in the thickness direction on a plane parallel to the stretching direction of the stretched cells. Note that the plane parallel to the extending direction of the expanded bubbles refers to a vector in the in-plane direction obtained when the vector indicating the extending direction of each expanded cell is divided into the in-plane direction of the foamed sheet and the thickness direction of the foamed sheet. A direction parallel to the most occupied direction among the directions.

  Then, a photograph of the cut surface of the foam sheet 1 was taken using a scanning electron microscope (SEM). In this photograph, the number of expanded bubbles and the total number of bubbles were counted, and the percentage of the number of expanded bubbles relative to the total number of bubbles was calculated. This value is calculated as the ratio of stretched bubbles in the bubbles of the foam sheet.

  The extending direction of the expanded cells of the foam sheet 1 is not particularly limited as long as it is a direction orthogonal to the thickness direction of the foam sheet, that is, the in-plane direction of the foam sheet, but the foam sheet is manufactured using an extruder. For this, the direction (CD) perpendicular to the extrusion direction (MD) of the foam sheet is preferred.

In the bubbles of the foam sheet 1, that is, all the bubbles including the stretched bubbles in the foam sheet, the average cell diameter D ₁ in the stretching direction and the average cell diameter in the direction perpendicular to the stretching direction and perpendicular to the thickness direction of the foam sheet. When the ratio to D ₂ (D ₁ / D ₂ ) (hereinafter sometimes referred to as “average cell diameter ratio”) is small, the flexibility of the foam sheet becomes insufficient, and the laminated foam sheet is used as a sealing material The workability at the time of disposing at a predetermined position decreases, and if it is large, the rigidity of the laminated foam sheet decreases, so 0.9 to 3.0 is preferable. In addition, the thickness direction of a foam sheet means a direction perpendicular | vertical with respect to the surface of a foam sheet.

Next, the average cell diameter D ₁ in the extending direction in all the bubbles of the foam sheet 1 is measured in the following manner. First, a foam sheet is cut | disconnected over the thickness direction in the thickness direction in the surface parallel to the extending direction of the extending | stretching bubble.

  Thereafter, the cut surface of the foam sheet 1 is magnified 60 times using a scanning electron microscope (SEM), and a photograph is taken so that the total length in the thickness direction of the foam sheet is accommodated.

  In the obtained photograph, a straight line having a length of 15 cm (actual length of 2500 μm before enlargement) on the photograph is parallel to the surface of the foam sheet at a portion corresponding to the central portion in the thickness direction of the foam sheet 1. Draw like so.

Next, the number of bubbles positioned on the straight line is visually counted, and the average bubble diameter in the extending direction of the bubbles is calculated based on the following formula.
Average bubble diameter D ₁ (μm) = 2500 (μm) / number of bubbles (pieces)

Further, in all cells of the foamed sheet 1, refers to average cell diameter D ₂ direction perpendicular to the orthogonal and the thickness direction of the foamed sheet 1 to the stretching direction of the stretched bubble is measured in the following manner. First, the foamed sheet 1 is cut at a surface perpendicular to the thickness direction at the center in the thickness direction. Thereafter, the cut surface of the foam sheet 1 is magnified 60 times using a scanning electron microscope (SEM) and photographed.

  In the obtained photograph, a straight line having a length of 15 cm on the photograph (actual length of 2500 μm before enlargement) on the surface corresponding to the central portion of the foam sheet 1 is placed on a plane parallel to the extending direction of the expanded bubbles. Draw in an orthogonal direction.

Next, the number of bubbles positioned on the straight line is visually counted, and the average bubble diameter in the extending direction of the bubbles is calculated based on the following formula.
Average bubble diameter D ₂ (μm) = 2500 (μm) / number of bubbles (number)

  In the above-described procedure for measuring the average bubble diameter, when counting the number of bubbles located on a straight line, the bubble diameter is determined based only on the bubble cross section appearing on the photograph.

  That is, the bubbles may seem to be completely separated from each other by the bubble wall on the cut surface of the foam sheet 1, but may be communicated with each other at a portion other than the cut surface of the foam sheet. In the present invention, without considering whether or not the portions other than the cut surface of the foam sheet communicate with each other, the bubble form was judged based on only the bubble film cross section appearing on the photograph, and appeared on the photograph One void portion completely surrounded by the bubble membrane cross section is determined as one bubble.

  Positioning on a straight line means that the straight line completely penetrates the bubble at any part of the bubble, and the straight line does not completely penetrate the bubble at both ends of the straight line. In the case where the end portion of the bubble is located in the bubble, the bubble was counted as 0.5.

  When taking a photograph of the cut surface of the foam sheet 1, coloring of the cut surface of the foam sheet facilitates the discrimination of bubbles, and when the photograph is magnified together with a 2500 μm scale, It becomes easy to specify the straight line length.

  When the closed cell ratio of the foamed sheet 1 is low, when the laminated foamed sheet is used as a sealing material, the sealing performance of the sealing material may be lowered, so 70% or more is preferable, and 80 to 100% is more preferable.

In addition, the closed cell rate of the foam sheet 1 means what was measured in the following way. First, a test piece having a flat square shape with a side of 5 cm and a constant thickness is cut out from the foam sheet. Then, the thickness of the test piece is measured to calculate the apparent volume V ₁ of the test piece, and the weight W _{1 of the} test piece is measured.

Next, the volume V ₂ occupied by the bubbles is calculated based on the following formula. The density of the resin constituting the test piece is ρg / cm ³ .
Volume occupied by bubbles V ₂ = V ₁ −W ₁ / ρ

Subsequently, the test piece is submerged in distilled water at 23 ° C. to a depth of 100 mm from the water surface, and a pressure of 15 kPa is applied to the test piece over 3 minutes. After that, the test piece is taken out of the water, the water adhering to the surface of the test piece is removed, the weight W _{2 of the} test piece is measured, and the open cell rate F ₁ and the closed cell rate F ₂ are calculated based on the following formulas. To do.
Open cell ratio F ₁ (%) = 100 × (W ₂ −W ₁ ) / V ₂
Closed cell ratio F ₂ (%) = 100−F ₁

  When the 25% compressive strength of the foamed sheet 1 is small, the sealing performance of the sealing material is lowered when the laminated foamed sheet is used as a sealing material. When the 25% compressive strength is large, when the laminated foamed sheet is used as the sealing material, Since the workability | operativity at the time of arrangement | positioning falls, it is limited to 30-200 kPa, and 30-150 kPa is preferable.

  In addition, the 25% compressive strength of the foam sheet 1 refers to that measured in accordance with JIS K6767. Specifically, a plurality of planar square test pieces each having a side of 5 cm are cut out from the foam sheet, and a plurality of these test pieces are stacked in the thickness direction to produce a laminate having a thickness of 25 cm. After being allowed to stand for a period of time, it can be determined by measuring the 25% compressive strength of the laminate in accordance with JIS K6767 at room temperature.

When the apparent density according to JIS K7222 of the foamed sheet 1 is small, the flexibility of the laminated foamed sheet is lowered, and when the laminated foamed sheet is used as a sealing material, the sealing performance may be lowered. When the laminated foamed sheet is used as a sealing material, the elastic restoring property may be lowered when compressed in the thickness direction, so 0.05 to 0.7 g / cm ³ is preferable.

  In addition, the foamed sheet 1 has additives such as talc, clay, flame retardant, zinc oxide, carbon black, silicon dioxide, titanium oxide, glass fiber, antioxidant, ultraviolet absorber and the like within the range not impairing the physical properties thereof. May be added as necessary.

  The flame retardant is not particularly limited, and examples thereof include metal hydroxides such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide, hydrotalcite, calcium carbonate, hexabromobiphenyl ether, decabromobiphenyl ether, and polyphosphoric acid. Ammonium, trimethyl phosphate, triethyl phosphate, melamine resin can be mentioned, even if the thickness of the foamed sheet is thin, a foamed sheet having flexibility can be obtained, and the laminated foamed sheet can be suitably used as a sealing material. Metal hydroxide is preferable, and magnesium hydroxide, aluminum hydroxide, calcium hydroxide, and hydrotalcite are more preferable.

  As shown in FIG. 1, a synthetic resin film 2 is laminated and integrated on at least one surface of the foamed sheet 1, preferably on both surfaces of the foamed sheet 1. The synthetic resin constituting the synthetic resin film 2 is not particularly limited, and examples thereof include polyester resins such as polyethylene terephthalate, polyolefin resins such as polyethylene resins and polypropylene resins, and polyester resins are preferable. Polyethylene terephthalate is more preferable.

As shown in FIG. 1, a polyimide resin layer 3 is laminated and integrated over the entire surface of at least the outer surface of the synthetic resin film 2, that is, the surface of the synthetic resin film 2 opposite to the foamed sheet 1. The polyimide resin layer imparts excellent flame retardancy to the laminated foam sheet. As shown in FIG. 2, polyimide resin layers may be laminated and integrated on both surfaces of the synthetic resin film 2.

When the synthetic resin films 2 and 2 are laminated and integrated on both surfaces of the foam sheet 1, polyimide resin layers 3 and 3 are entirely laminated on at least the outer surface or both surfaces of the both synthetic resin films 2 and 2. It is integrated . In FIG. 3, polyimide resin layers 3 and 3 are laminated and integrated on both surfaces of the synthetic resin film 2.

Thus, the synthetic resin film 2 is laminated and integrated on at least one surface of the foamed sheet 1, and the polyimide resin layer 3 having excellent flame retardancy on the surface (outer surface) of the synthetic resin film is laminated and integrated. Therefore, the laminated foam sheet has excellent flame retardancy.

  Moreover, the laminated foam sheet of the present invention is not given flame retardancy by containing a flame retardant in the foam sheet, but is given flame retardancy by the polyimide resin layer 3. Flexibility is not impaired, and when used as a sealing material, excellent sealing properties are exhibited.

  In addition, the foam sheet and the synthetic resin film may be integrated by thermal fusion between the thermoplastic resin constituting the foam sheet and the synthetic resin constituting the synthetic resin film. It is preferable that the resin film is integrated with an adhesive. Examples of such adhesives include acrylic adhesives and urethane adhesives.

Next, the manufacturing method of a laminated foam sheet is demonstrated. First, the manufacturing method of a foam sheet is demonstrated. The method for producing the foam sheet is not particularly limited.For example, (1) a thermoplastic resin and a thermally decomposable foaming agent are supplied to an extruder, melt-kneaded, and extruded into a sheet form from the extruder. The step of producing a resin sheet, the step of irradiating the foamable resin sheet with ionizing radiation and crosslinking, the heated foamed resin sheet is heated and foamed, and the resulting foamed sheet is melted at the time of foaming The foam sheet is stretched by stretching in the direction (width direction) perpendicular to the extrusion direction while maintaining the foam, and the foam sheet is stretched. (2) Thermoplastic resin, pyrolytic foaming A step of producing a foamable resin sheet by supplying an agent and an organic peroxide to an extruder, melt-kneading, and extruding into a sheet form from the extruder, and heating the foamable resin sheet to form an organic peroxide Disassemble The step of foaming while foaming resin sheet is cross-linked, and the foamed sheet is stretched in the direction (width direction) orthogonal to the extrusion direction while maintaining the molten state at the time of foaming. And (3) supplying a thermoplastic resin and a pyrolytic foaming agent to an extruder, melt-kneading, and extruding the foamable resin sheet into a sheet from the extruder. A step of producing, a step of irradiating this foamable resin sheet with ionizing radiation to crosslink the foamable resin sheet, and a foamed sheet produced by heating, foaming and cooling the crosslinked foamable resin sheet A step of heating the foamed sheet again to a molten or softened state, and stretching the foamed sheet in a direction perpendicular to the extrusion direction (width direction) to stretch the foam sheet bubbles, (4) Supplying thermoplastic resin, pyrolytic foaming agent and organic peroxide to an extruder, melt-kneading, and extruding into a sheet from the extruder A step of producing a resin sheet, a step of heating the foamable resin sheet to decompose the organic peroxide, and foaming the foamable resin sheet while crosslinking the foamed resin sheet; A step of heating the sheet again to a molten or softened state, and a foamed sheet for stretching the foamed sheet by stretching the foamed sheet in a direction (width direction) orthogonal to the extrusion direction to stretch the foam. And the like.

  The pyrolytic foaming agent is not particularly limited as long as it is one that decomposes by heating and generates gas, and has been conventionally used in the production of foams. For example, azodicarbonamide, N , N′-dinitrosopentamethylenetetramine, p-toluenesulfonyl semicarbazide, and azodicarbonamide is preferable. In addition, a thermal decomposition type foaming agent may be used independently, or 2 or more types may be used together.

  And the addition amount of a thermal decomposition type foaming agent has preferable 1-30 weight part with respect to 100 weight part of thermoplastic resins. If the amount of the pyrolytic foaming agent is small, the foamed sheet may not be sufficiently foamed. When the amount of the pyrolytic foaming agent added is large, the bubbles formed by foaming may not be stable, and the foam structure of the foam may become uneven.

  And as a method of cross-linking the foamable resin sheet, for example, a method of irradiating the foamable resin sheet with ionizing radiation such as electron beam, α ray, β ray, γ ray, A method in which an organic peroxide is blended and the obtained foamable resin sheet is heated to decompose the organic peroxide can be used, and these methods may be used in combination.

  Examples of the organic peroxide include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis. (T-butylperoxy) octane, n-butyl-4,4-bis (t-butylperoxy) valerate, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α '-Bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t- Butylperoxy) hexyne-3, benzoyl peroxide, cumylperoxyneodecanate, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di ( Benzoylperoxy) hexane, t-butylperoxyisopropyl carbonate, and t-butylperoxyallyl carbonate. These may be used alone or in combination of two or more.

  If the amount of the organic peroxide added is small, crosslinking of the foamable resin sheet may be insufficient. If it is large, the foamable resin sheet becomes too hard and foaming may be difficult. The amount is preferably 0.01 to 5 parts by weight and more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the thermoplastic resin.

  Further, the method for foaming the foamable resin sheet is not particularly limited, and examples thereof include a method of heating with hot air, a method of heating with infrared rays, a method of salt bath, and a method of oil bath. These may be used in combination.

  The stretching of the foamed sheet may be performed after foaming the foamable resin sheet to obtain the foamed sheet, or may be performed while foaming the foamable resin sheet. In addition, after foaming the foamable resin sheet to obtain the foamed sheet, when the foamed sheet is stretched, the foamed sheet is continuously stretched while maintaining the molten state at the time of foaming without cooling the foamed sheet. Alternatively, after the foam sheet is cooled, the foam sheet may be heated again to be in a molten or softened state and then stretched. Furthermore, the stretched foam sheet may be stretched again in the manner described above.

  The foamed sheet is produced by stretching the foamed sheet in a predetermined direction to stretch and deform the foamed sheet in a predetermined direction, and innumerable stretched bubbles are oriented in the same direction. can do.

  Further, as a method of stretching the foam sheet in the width direction, foaming is performed by gripping both ends of the foam sheet in the width direction with a pair of gripping members and gradually moving the pair of gripping members in a direction away from each other. A method of stretching the sheet in the width direction is preferable. In addition, since the foamable resin sheet expands in the width direction due to its own foaming, when the foamed sheet is stretched in the width direction, the expansion in the width direction due to foaming of the foamable resin sheet is taken into consideration. It is necessary to adjust so that the foamed sheet is stretched in the width direction more than the expansion amount.

  Further, the draw ratio in the width direction of the foamed sheet is preferably 1.5 to 3 times. When the draw ratio is small, the flexibility of the foamed sheet becomes insufficient, and when the laminated foamed sheet is used as a sealing material, workability when disposed at a predetermined position may be lowered. When the draw ratio is large, the foamed sheet may be broken.

Incidentally, the draw ratio of the width of the foam sheet, heating the foamable resin sheet without stretching in its extrusion direction and the width direction, the length in the width of the foamed sheet obtained by foaming and W _1, stretched in the width the length of the width of the foam sheet was set to W _2, can be calculated based on the following equation.
Stretch ratio (times) in the width of the foam sheet = W ₂ / W ₁

The method for laminating and integrating the synthetic resin film on one surface of the foamed sheet is not particularly limited, and examples thereof include a method for laminating and integrating the synthetic resin film on one surface of the foamed sheet via an adhesive. At this time, it is necessary to preliminarily laminate and integrate a polyimide resin layer on one side or both sides of the synthetic resin film in advance, and to laminate and integrate the synthetic resin film on one surface of the foam sheet so that the polyimide resin layer is on the outside. is there.

Moreover, the thickness of a laminated foam sheet is limited to 0.1-1 mm. If the laminated foam sheet is thin, the sealing performance may be lowered when the laminated foam sheet is used as a sealing material. If the laminated foam sheet is thick, the laminated foam sheet may be disposed at a desired location when the laminated foam sheet is used as a sealing material. The workability during installation may be reduced.

  The laminated foam sheet of the present invention can be suitably used as a sealing material under high temperature conditions because the foam sheet has an appropriate compressive strength and has excellent flame retardancy due to the polyimide resin layer. .

And the laminated foam sheet has added flame retardancy by the polyimide resin layer laminated and integrated on the surface of the synthetic resin film laminated and integrated on one surface of the foam sheet instead of containing the flame retardant in the foam sheet. Therefore, the foamed sheet is excellent in flexibility, and exhibits good sealing properties when used as a sealing material.

It is the model longitudinal cross-sectional view which showed the laminated foam sheet of this invention. It is the model longitudinal cross-sectional view which showed another example of the laminated foam sheet of this invention. It is the model longitudinal cross-sectional view which showed another example of the laminated foam sheet of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Foam sheet 2 Synthetic resin film 3 Polyimide resin layer A Laminated foam sheet

Example 1
100 parts by weight of polyethylene obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst (trade name “KF370” manufactured by Nippon Polyethylene Co., Ltd., density: 0.905 g / cm ³ ), 2.5 parts by weight of azodicarbonamide And 0.36 parts by weight of 2,6-di-t-butyl-p-cresol and 0.2 parts by weight of zinc oxide as a foaming aid are supplied to an extruder and melt-kneaded at 120 ° C. to obtain a thickness of 0 A foamable polyethylene sheet having a thickness of 3 mm and a width of 200 mm was obtained.

  The foamable polyethylene sheet was crosslinked by irradiating it with 5 Mrad of an electron beam at an acceleration voltage of 800 kV. The foamable polyethylene sheet was supplied to a foaming furnace maintained at 250 ° C. and foamed to obtain a polyethylene foam sheet. In addition, the discharge rate of the polyethylene foam sheet from the foaming furnace was adjusted to 2.5 times the supply speed of the foamable polyethylene sheet to the foaming furnace so that tension was not substantially applied to the polyethylene foam sheet in the extrusion direction.

While maintaining the molten state of the obtained foamed sheet, the end in the width direction is continuously sucked with a suction-type guider and stretched three times in the width direction, and the bubbles are in a direction perpendicular to the extrusion direction ( The foamed sheet having stretched cells was obtained by stretching in the width direction). The foam sheet had an expansion ratio of 3.3 cm ³ / g, a thickness of 0.1 mm, and a width of 600 mm.

In all the bubbles of the foam sheet, and average cell diameter D _1, (average cell diameter of the average cell diameter / extrusion width direction) the ratio of the average cell diameter D ₂ of the extrusion direction in the stretching direction (width direction) is 1. 90. The ratio of stretched bubbles in the bubbles of the foamed sheet was 90%.

A polyimide terephthalate film (trade name “Lumirror ZV” manufactured by Toray Industries, Inc.) with a polyimide resin layer entirely laminated and integrated on both sides and a thickness of 25 μm is prepared, and an acrylic adhesive (Sekisui Fuller) is provided on one side of the polyethylene terephthalate film. After applying 15 g / m ² of the product name “7850” manufactured by the company, the polyethylene terephthalate film is laminated and integrated on the foam sheet so that the acrylic adhesive is on the foam sheet side. A sheet was obtained.

(Example 2)
Laminated foam sheet in the same manner as in Example 1 except that 3.1 parts by weight of azodicarbonamide was used instead of 2.5 parts by weight, and that the foamed sheet was stretched twice instead of three times in the width direction. Got.

The obtained foamed sheet had an expansion ratio of 5 cm ³ / g, a thickness of 0.20 mm, and a width of 400 mm. In all the bubbles of the foam sheet, and average cell diameter D _1, (average cell diameter of the average cell diameter / extrusion width direction) the ratio of the average cell diameter D ₂ of the extrusion direction in the stretching direction (width direction) is 1. 50. The ratio of stretched bubbles in the bubbles of the foamed sheet was 90%.

(Example 3)
A laminated foam sheet was obtained in the same manner as in Example 1 except that the foam sheet was stretched 1.5 times in the width direction instead of 3 times.

The obtained foamed sheet had an expansion ratio of 3 cm ³ / g, a thickness of 0.30 mm, and a width of 300 mm. In all the bubbles of the foam sheet, and average cell diameter D _1, (average cell diameter of the average cell diameter / extrusion width direction) the ratio of the average cell diameter D ₂ of the extrusion direction in the stretching direction (width direction) is 1. 80. The ratio of stretched bubbles in the bubbles of the foamed sheet was 90%.

Example 4
Azodicarbonamide was changed to 5.5 parts by weight instead of 2.5 parts by weight, the thickness of the foamable polyethylene sheet was changed to 0.5 mm instead of 0.3 mm, and the foamed sheet was tripled in the width direction. Instead, a laminated foam sheet was obtained in the same manner as in Example 1 except that the film was stretched twice.

The obtained foamed sheet had an expansion ratio of 10 cm ³ / g, a thickness of 0.50 mm, and a width of 400 mm. In all the bubbles of the foam sheet, and average cell diameter D _1, (average cell diameter of the average cell diameter / extrusion width direction) the ratio of the average cell diameter D ₂ of the extrusion direction in the stretching direction (width direction) is 1. 50. The ratio of stretched bubbles in the bubbles of the foamed sheet was 90%.

(Example 5)
Except for using a polyethylene terephthalate film (trade name “Lumirror ZV (single-sided product)” manufactured by Toray Industries, Inc.) having a polyimide resin layer entirely laminated and integrated on one side and a thickness of 25 μm as a polyethylene terephthalate film. In the same manner as in Example 1, a laminated foam sheet was obtained.

(Example 6)
A laminated foam sheet was obtained in the same manner as in Example 1 except that 30 parts by weight of magnesium hydroxide (trade name “Kisuma 5A” manufactured by Kyowa Chemical Co., Ltd.) was further supplied to the extruder.

The obtained foamed sheet had an expansion ratio of 2 cm ³ / g, a thickness of 0.50 mm, and a width of 600 mm. In all the bubbles of the foam sheet, and average cell diameter D _1, (average cell diameter of the average cell diameter / extrusion width direction) the ratio of the average cell diameter D ₂ of the extrusion direction in the stretching direction (width direction) is 1. 50. The ratio of stretched bubbles in the bubbles of the foamed sheet was 90%.

(Comparative Example 1)
As the polyethylene terephthalate film, a laminated foamed sheet was obtained in the same manner as in Example 1 except that a polyethylene terephthalate film having a thickness of 25 μm with no polyimide resin layers laminated and integrated on both sides was used.

(Comparative Example 2)
A laminated foam sheet was obtained in the same manner as in Comparative Example 1 except that 100 parts by weight of magnesium hydroxide (trade name “Kisuma 5A” manufactured by Kyowa Chemical Co., Ltd.) was further supplied to the extruder.

The foamed sheet thus obtained had an expansion ratio of 0.6 cm ³ / g, a thickness of 0.10 mm, and a width of 600 mm. In all the bubbles of the foamed sheet, the average cell diameter D ₁ of the stretching direction (width direction), the ratio of the average cell diameter D ₂ of the extrusion direction (average cell diameter in the width direction of the average cell diameter / extrusion direction) 0. 50. The ratio of stretched bubbles in the bubbles of the foamed sheet was 90%.

(Comparative Example 3)
A laminated foamed sheet was obtained in the same manner as in Example 5 except that a polyethylene terephthalate film having a thickness of 25 μm with no polyimide resin layer laminated and integrated on both sides was used as the polyethylene terephthalate film.

(Comparative Example 4)
As the foam sheet, a flame-retardant polyurethane resin foam sheet (foaming ratio: 2.5 cm ³ / g, thickness: 0.50 mm) commercially available from Roger Inoac under the trade name “SRU-40P” was used. A laminated foam sheet was obtained in the same manner as Example 1 except for the above. The flame-retardant polyurethane resin foam sheet contained 30 parts by weight of aluminum hydroxide with respect to 100 parts by weight of the polyurethane resin.

  The apparent density and closed cell ratio of the obtained foamed sheet were measured, and the results are shown in Table 1. Further, the 25% compressive strength of the laminated foamed sheet was measured as described above, and the flame retardancy and water tightness of the laminated foamed sheet were measured as follows, and the results are shown in Table 1.

(Flame retardance)
The flame retardancy of the obtained laminated foam sheet was measured according to UL94HBF.

(Watertightness)
After sticking a double-sided pressure-sensitive adhesive tape on both sides of the laminated foamed sheet, a test piece was obtained by punching from the laminated foamed sheet into a ring shape having an outer diameter of 60 mm and an inner diameter of 40 mm over the entire thickness of the sealing material.

  The test piece is sandwiched between two parallel acrylic resin plates so that the compression rate of the test piece is 20%, that is, the thickness of the test piece after compression is 20% of the thickness before compression. The test piece was compressed with two acrylic resin plates in the thickness direction.

  One acrylic resin plate of the two acrylic resin plates has a through hole for water filling and pressure application in a portion corresponding to the center portion of the test piece. From this through hole, Fill the space surrounded by the opposing surfaces of the two acrylic resin plates and the test piece with tap water, and then apply a pressure of 10 kPa at 23 ° C. for 5 minutes to conduct a water leak test, The presence or absence was visually observed. The case where there was no water leakage was indicated as “O”, and the case where water leakage occurred was indicated as “X”.

Claims (7)

25% compressive strength is at a synthetic resin film on at least one surface of the foam sheet is integrally laminated 30～200KPa, the outer surface of the synthetic resin film had a laminated foam sheet polyimide resin layer are integrally laminated And the thickness of the said laminated foam sheet is 0.1-1 mm, The laminated foam sheet characterized by the above-mentioned .   The laminated foam sheet according to claim 1, wherein the foam sheet contains 1 to 50 parts by weight of a metal hydroxide with respect to 100 parts by weight of the synthetic resin constituting the foam sheet. The foam sheet has bubbles stretched in a direction orthogonal to the thickness direction of the foam sheet, and in the foam of the foam sheet, the average cell diameter D ₁ in the stretch direction is orthogonal to the stretch direction and _3. The ratio (D ₁ / D ₂ ) to the average cell diameter D _{2 in} a direction orthogonal to the thickness direction of the foamed sheet is 0.9 to 3.0. 3. Laminated foam sheet. The laminated foam sheet according to any one of claims 1 to 3 , wherein the apparent density of the foam sheet is 0.05 to 0.7 g / cm ³ .   The laminated foam sheet according to claim 1, wherein the synthetic resin film is a polyethylene terephthalate film.   The laminated foam sheet according to any one of claims 1 to 3, wherein the synthetic resin constituting the foam sheet is a polyolefin resin.   The laminated foam sheet according to claim 1, wherein an adhesive layer is interposed between the foam sheet and the synthetic resin film.

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