JP2016108423A - Method for producing foamed sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a foamed sheet capable of obtaining a foamed sheet which is hardly broken and has high flexibility in spite of having a thin thickness by being compressed.SOLUTION: A method for producing a foamed sheet includes: a foaming step of foaming a resin composition, and obtaining a foamed body in which a plurality of air bubbles are exposed to the surface of the outside of a first surface portion in one side in a thickness direction, and a second surface portion in the other side in the thickness direction is a skin layer; and a heating and compressing step of heating and compressing the foamed body, and obtaining a foamed sheet in which a plurality of air bubbles are exposed to the surface of the outside of the first surface portion in one side in the thickness direction and the second surface portion in the other side in the thickness direction is the skin layer. The heating and compressing step heats and compresses the foamed body from the side of the second surface portion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a foam sheet for foaming a resin composition.

  Conventionally, a thermoplastic resin foam obtained by foam-molding a thermoplastic resin has been used in various applications. The thermoplastic resin foam is often used, for example, as a cushioning material for packaging and a structural member for automobiles.

  Among thermoplastic resin foams, polyolefin resin foams are excellent in processability and flexibility, and are used as adhesive sheets used in electronic and electrical equipment, and as base materials for sealing materials. . In pressure-sensitive adhesive sheets used for electronic / electrical devices, demands for reduction in thickness and weight are increasing.

  Moreover, the pressure-sensitive adhesive sheet used for electronic / electric equipment is also required to have excellent strength. Conventionally, slicing has been performed to make a thermoplastic resin foam thin. However, there is a problem that the strength is lowered only by slicing the thermoplastic resin foam.

  Further, Patent Documents 1 to 3 below disclose a method for producing a polyolefin resin foam.

  Patent Document 1 discloses a method for producing a polyolefin resin thin-layer foamed sheet having a plurality of bubbles partitioned by walls containing a polyolefin resin. In this polyolefin resin thin-layer foam sheet, the thickness is 0.05 to 0.5 mm, the expansion ratio is 2 to 15 times, the open cell ratio is 30 to 95%, and the bubble breaking ratio is 1 to 30%.

  In Patent Document 2, a polyolefin resin foam is formed by extrusion foam molding with an annular die using a polyolefin resin composition containing a polyolefin resin as a thermoplastic resin and carbon dioxide (carbon dioxide) as a foaming agent. A method for manufacturing a body is disclosed. The polyolefin resin composition includes (a) a polyolefin resin, (b) (b1) an elastomer, and (b2) a plastomer. The blending ratio of the above (a) and (b) is in the range of 90/10 to 10/90 by weight ratio. The blending ratio of the above (b1) and (b2) is in the range of 90/10 to 10/90 by weight ratio.

Patent Document 3 discloses a method for producing a resin foam having a foam layer and a surface layer. The foam layer and the surface layer have the same composition. The surface coverage of the surface layer is 40% or more. The density of the foam layer is 0.20 g / cm ³ or less. In Patent Document 3, the resin constituting the resin foam is a thermoplastic resin, and a polyolefin resin is exemplified as this thermoplastic resin. The surface layer is formed by heat melting treatment. The resin foam has a thickness of 0.2 to 5 mm. The resin foam is used for electric / electronic devices.

JP 2014-062245 A JP, 2014-084341, A JP 2013-147667 A

  In the polyolefin resin foams described in Patent Documents 1 to 3, the tensile strength may be low. For this reason, when stress is added to the polyolefin resin foam, the foam may break. Moreover, in the polyolefin-type resin foam of patent documents 1-3, a softness | flexibility may be low.

  Moreover, in the polyolefin-type resin foam of patent documents 1-3, when thickness is made thin, there exists a problem that the tensile strength of a foam will become further lower or the softness | flexibility of a foam will become further lower.

  The objective of this invention is providing the manufacturing method of the foam sheet which can obtain the foam sheet which is hard to fracture | rupture and is highly flexible although thickness is thin by being compressed.

  According to the wide aspect of the present invention, the resin composition is foamed, and a plurality of bubbles are exposed on the outer surface of the first surface portion on one side in the thickness direction, and the second on the other side in the thickness direction. A foaming step of obtaining a foam whose surface part is a skin layer, and heating and compressing the foam to expose a plurality of bubbles on the outer surface of the first surface part on one side in the thickness direction. And a heat compression step for obtaining a foam sheet in which the second surface portion on the other side in the thickness direction is a skin layer, and in the heat compression step, the foam is heated from the second surface portion side. A method of manufacturing a foam sheet that compresses is provided.

  In a specific aspect of the method for producing a foam sheet according to the present invention, in the foaming step, without slicing the surface on the other side in the thickness direction, only the surface on one side in the thickness direction is sliced and foamed. Get the body.

  On the specific situation with the manufacturing method of the foam sheet which concerns on this invention, in the said heat compression process, 0.1 seconds or more and 5 seconds or less are heated, making the said foam contact a heat source.

  In a specific aspect of the method for producing a foam sheet according to the present invention, in the heating and compression step, the foam is heated and compressed while being in contact with a heat source, or the foam is heated while being in contact with a heat source. Thereafter, the foam is compressed during cooling.

  On the specific situation with the manufacturing method of the foam sheet which concerns on this invention, In the said heat compression process, ratio of the thickness of the foam sheet obtained with respect to the thickness of the said foam becomes 0.1 or more and 0.95 or less. The foam is heated and compressed.

  The resin composition preferably contains a polypropylene resin. The resin composition preferably includes a polypropylene resin and at least one of an olefinic thermoplastic elastomer and a polyethylene plastomer. In the resin composition, the total content of the polypropylene resin, the olefinic thermoplastic elastomer, and the polyethylene plastomer is 100% by weight, and the content of the polypropylene resin is 10% by weight or more and 90% by weight or less and the olefin. The total content of the thermoplastic elastomer and the polyethylene plastomer is preferably 10% by weight or more and 90% by weight or less.

  On the specific situation with the manufacturing method of the foam sheet which concerns on this invention, 25% compressive stress obtains the foam sheet which is 10 kPa or more and 150 kPa or less.

In a specific aspect of the method for producing a foam sheet according to the present invention, the number of exposed bubbles in a range of 1 mm ² of the first surface portion is 20 or more, and 1 mm ² of the second surface portion. A foam sheet in which the number of exposed bubbles in the range is 10 or less is obtained.

  In the method for producing a foamed sheet according to the present invention, the resin composition is foamed, and a plurality of bubbles are exposed on the outer surface of the first surface portion on one side in the thickness direction, and the other side in the thickness direction is exposed. A foaming step for obtaining a foam in which the second surface portion is a skin layer, and heating and compressing the foam, a plurality of bubbles are exposed on the outer surface of the first surface portion on one side in the thickness direction. And a heat compression step of obtaining a foam sheet in which the second surface portion on the other side in the thickness direction is a skin layer, and in the heat compression step, the foam is formed from the second surface portion side. Since it is heated and compressed, it is possible to obtain a foam sheet that is hard to break and has high flexibility despite being thin due to being compressed.

FIG. 1 is a cross-sectional SEM image showing a foam sheet obtained by the foam sheet manufacturing method according to one embodiment of the present invention. FIG. 2 is a cross-sectional SEM image showing a foam (before heat compression treatment) used to obtain a foam sheet.

  Hereinafter, the present invention will be described in detail.

  The method for producing a foam sheet according to the present invention includes a foaming step and a heat compression step. The said foaming process is a process of making a resin composition foam and obtaining a foam. In the foaming step, a foam is obtained in which a plurality of bubbles are exposed on the outer surface of the first surface portion on one side in the thickness direction, and the second surface portion on the other side in the thickness direction is a skin layer. . The heat compression step is a step of heating and compressing the foam to obtain a foam sheet. In the heat compression step, a foam sheet in which a plurality of bubbles are exposed on the outer surface of the first surface portion on one side in the thickness direction, and the second surface portion on the other side in the thickness direction is a skin layer. Get. The obtained foam sheet has a plurality of bubbles. In the obtained foamed sheet, the central portion in the thickness direction, the first surface portion on one side in the thickness direction, and the second surface portion on the other side in the thickness direction are all formed of the resin composition. Yes. Moreover, in the manufacturing method of the foam sheet which concerns on this invention, the said foam is heated and compressed from the said 2nd surface side in the said heat compression process.

  In this invention, since the structure mentioned above is provided, it is hard to fracture | rupture and it can obtain a highly flexible foam sheet. In addition, in the present invention, it is possible to obtain a foam sheet that is difficult to break and has high flexibility despite being thin. For example, when the thickness is larger than 0.5 mm, it is difficult to make it difficult to break when the thickness is 0.5 mm or less, even though it is difficult to break to some extent. In the present invention, even if the thickness is 0.5 mm or less, a foamed sheet that is difficult to break can be obtained. For example, when the thickness is larger than 0.5 mm, even if the flexibility can be increased to some extent, it is difficult to increase the flexibility when the thickness is 0.5 mm or less. In the present invention, a foam sheet having high flexibility can be obtained even if the thickness is 0.5 mm or less.

  From the viewpoint of further increasing the tensile strength and flexibility, it is preferable not to heat the foam from the first surface side in the heat compression step, and preferably not compress the foam from the first surface side. It is preferable not to heat and compress the foam from the first surface side.

  From the viewpoint of further increasing the tensile strength and flexibility, the thickness of the foam sheet is preferably 0.05 mm or more, more preferably 0.06 mm or more, still more preferably 0.07 mm or more, and further preferably 0.08 mm or more. Especially preferably, it is 0.09 mm or more, Most preferably, it is 0.10 mm or more. From the viewpoint of meeting the demand for thinning, the thickness of the foamed sheet is preferably 1 mm or less, more preferably 0.50 mm or less, still more preferably 0.45 mm or less, still more preferably 0.40 mm or less, particularly preferably. It is 0.35 mm or less, and most preferably 0.30 mm or less.

  From the viewpoint of further improving the breakage prevention property, the tensile strength of the foamed sheet is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, still more preferably 0.3 MPa or more, still more preferably 0.4 MPa or more, particularly Preferably it is 0.5 MPa or more, most preferably 0.6 MPa or more. The tensile strength of the foamed sheet is preferably 30 MPa or less.

  The foam sheet may be obtained through a melt extrusion foam molding process or the like. It is preferable that the tensile strength in the flow direction (MD direction) of the foam sheet and the tensile strength in the direction (TD direction) perpendicular to the flow direction of the foam sheet are not less than the above lower limit and not more than the above upper limit.

  From the viewpoint of further increasing the flexibility, the 25% compressive stress of the foamed sheet is preferably 200 kPa or less, more preferably 150 kPa or less. The 25% compressive stress of the foamed sheet is preferably 10 kPa or more.

  It is preferable that the arithmetic mean roughness Ra of the surface of both sides in a foam sheet differs. In this case, it is preferable that the side with the larger arithmetic average roughness Ra is the first surface portion side. The arithmetic average roughness Ra of the outer surface of the first surface portion is preferably larger than the arithmetic average roughness Ra of the outer surface of the second surface portion. The arithmetic average roughness Ra is measured according to JIS B0601: 1994.

From the viewpoint of effectively increasing the tensile strength and flexibility, the number of exposed bubbles in the 1 mm ² range (1 mm × 1 mm square range) of the first surface portion in the foam sheet is preferably 20 or more. , More preferably 30 or more, still more preferably 40 or more, particularly preferably 50 or more. The number of exposed bubbles in the 1 mm ² range (1 mm × 1 mm square range) of the second surface portion is preferably 10 or less, more preferably 5 or less, still more preferably 3 or less, particularly preferably. 0.

  From the viewpoint of increasing the tensile strength and flexibility, the second surface portion is a skin layer. The skin layer is a layer having a higher resin density than other regions. From the viewpoint of effectively increasing the tensile strength and flexibility, in the foamed sheet, the first surface portion is preferably a surface portion formed by slicing. From the viewpoint of effectively increasing the tensile strength and flexibility, in the foamed sheet, the second surface portion is preferably a surface portion that has not been sliced. From the viewpoint of effectively increasing the tensile strength and flexibility, in the foamed sheet, the resin density of the second surface portion is preferably higher than the center portion, and the resin density is higher than that of the first surface portion. High is preferred.

  In the foam sheet, a plurality of bubbles are exposed on the outer surface of the first surface portion. From the viewpoint of effectively increasing the tensile strength and flexibility, in the foam sheet, the average cell diameter of the exposed cell cross section on the outer surface of the first surface portion is preferably 20 μm or more, more preferably 25 μm or more. The thickness is preferably 200 μm or less, more preferably 150 μm or less. The bubble diameter of the bubble cross section is the long diameter of the bubble cross section. The average bubble diameter of the bubble cross section is obtained by averaging the long diameters of the bubble cross sections.

  In the foam sheet, the total surface area of the outer surface of the first surface portion is 100%, and the surface area without bubbles is preferably 5% or more, more preferably 10% or more, preferably 40% or less, more preferably 35% or less. It is. In the foamed sheet, out of the total surface area 100% of the outer surface of the second surface portion, the surface area without bubbles is preferably 90% or more, more preferably 95% or more, and particularly preferably 100% (exposed skin layer and bubbles). None). In the examples described later, the surface area without bubbles was 100% in the total surface area 100% of the outer surface of the second surface portion.

  The foam sheet is obtained through a heat compression process. A specific surface portion can be easily formed by heat compression treatment. The said foam sheet is obtained by heat-pressing the foam obtained by making a resin composition foam. The said foam is a sheet | seat before a heat compression process, for example. It is preferable to melt the surface of the foamed sheet during heating. By melting, it is possible to control the bubble state on the outer surface of the surface portion, the surface state, and the number of exposed bubbles. Further, the foamed sheet can be made thinner by heat compression treatment. In addition, the heat compression treatment makes the bubbles flat and reduces the repulsive force when a load is applied.

  When the foam sheet is divided into three in the thickness direction, the direction in which the length directions of the plurality of bubbles are averaged is parallel to the direction orthogonal to the thickness direction of the foam sheet in the central third region of the thickness direction. Or a direction inclined at 30 ° or less with respect to the direction perpendicular to the thickness direction of the foam sheet. When the direction in which the length direction of the bubbles is averaged is inclined with respect to the direction orthogonal to the thickness direction of the foam sheet, the inclination angle is more preferably 25 ° or less, still more preferably 20 ° or less, and particularly preferably Is 15 ° or less. In the examples described later, the air bubbles in the central region in the thickness direction were flat and extended in a direction perpendicular to the thickness direction of the foamed sheet, and the inclination angle was 30 ° or less.

  The average thickness of the foamed sheet is preferably 0.03 mm or more, more preferably 0.05 mm or more, further preferably 0.06 mm or more, preferably 0.55 mm or less, more preferably 0.50 mm or less, still more preferably 0. .45 mm or less. When the average thickness of the foamed sheet is not less than the above lower limit, the tensile strength is further increased. When the average thickness of the foamed sheet is not more than the above upper limit, it is possible to meet the demand for thinning. Moreover, in this invention, even if the thickness of a foam sheet is thin and the average thickness of a foam sheet is below the said upper limit, tensile strength becomes high enough.

  From the viewpoint of effectively increasing the tensile strength and flexibility, in the foaming process, the surface on the other side in the thickness direction is not sliced, and the surface on one side in the thickness direction is sliced to obtain a foam. It is preferable. From the viewpoint of effectively increasing the tensile strength and flexibility, it is preferable to heat and compress the foam from the surface side that has not been sliced in the heat compression step. It is preferable to obtain a foam sheet having a central portion, a sliced first surface portion, and a sliced second surface portion in the thickness direction.

  In the heat compression step, the foam is preferably heated while being in contact with a heat source.

  From the viewpoint of effectively increasing the tensile strength and flexibility, the temperature of the heat source (heating temperature) is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, still more preferably 50 ° C. or higher, still more preferably 55 ° C. or higher, Particularly preferably, it is 75 ° C or higher, most preferably 95 ° C or higher, preferably 170 ° C or lower, more preferably 160 ° C or lower, and further preferably 150 ° C or lower.

  From the viewpoint of effectively increasing the tensile strength and flexibility, the contact time (heating time) with the heat source is preferably 0.1 seconds or longer, more preferably 0.2 seconds or longer, preferably 5.0 seconds or shorter, more preferably. Is 4.5 seconds or less, more preferably 4.0 seconds or less.

  From the viewpoint of effectively increasing the tensile strength and flexibility, the pressure during compression is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, still more preferably 0.15 MPa or more, preferably 1.1 MPa or less. Preferably it is 1.0 MPa or less, More preferably, it is 0.9 MPa or less.

  From the viewpoint of effectively increasing the tensile strength and flexibility, in the heating and compression step, the foam is heated and compressed while being in contact with a heat source, or the foam is heated while being in contact with a heat source, The foam is preferably compressed during cooling, and in the heating and compression step, it is more preferable to heat and compress the foam while contacting the foam with a heat source.

  From the viewpoint of effectively increasing the tensile strength and flexibility, the thickness of the foam is preferably 0.1 mm or more, more preferably 0.2 mm or more, still more preferably 0.3 mm or more, preferably 3.5 mm or less, More preferably, it is 3 mm or less, More preferably, it is 2.5 mm or less.

  From the viewpoint of effectively increasing the tensile strength and flexibility using a resin composition containing components (A) to (C) described later, the foaming ratio of the foam is preferably 5 times or more, more preferably 10 Times or more, more preferably 15 times or more, preferably 25 times or less, more preferably 24 times or less, still more preferably 23 times or less.

  From the viewpoint of effectively increasing the tensile strength and flexibility using a resin composition containing the components (A) to (C) described later, the average cell diameter in the foam is preferably 0.01 mm or more, more preferably It is 0.02 mm or more, more preferably 0.03 mm or more, preferably 0.3 mm or less, more preferably 0.2 mm or less, still more preferably 0.15 mm or less. In the examples described later, the average cell diameter in the foam was in the range of 0.05 mm or more and 0.15 mm or less. In addition, the bubble diameter in a foam is the thickness direction of a sheet | seat, the 1st direction (for example, MD direction) orthogonal to a thickness direction, and the 2nd direction (for example, TD direction) orthogonal to a thickness direction and a 1st direction. The diameter of each bubble can be obtained by averaging the diameters. The bubble diameter of the foam is obtained by averaging the diameters of a plurality of bubbles.

  The ratio of the thickness of the obtained foam sheet to the thickness of the foam during the heat compression treatment (foam sheet thickness / foam thickness) is preferably 0.05 or more, more preferably 0.06 or more, and further The foam is heated and compressed so that it is preferably 0.07 or more, preferably 0.98 or less, more preferably 0.95 or less, and even more preferably 0.93 or less. When the foam is heated and compressed so as to satisfy the above thickness relationship, the thickness is appropriately reduced, and the tensile strength and flexibility are sufficiently increased.

  In the step of obtaining the foam, it is preferable to use an annular die. The annular die preferably has a bubble generation unit that generates bubbles and a bubble growth unit that grows the generated bubbles. The bubble growth part is located downstream of the bubble generation part. In addition, the annular die generally has a forming part that performs sheet forming downstream of the bubble growth part. The bubble generation part is preferably a part where the width of the flow path through which the resin composition flows is narrowed. The bubble growth part is preferably a part where the width of the flow path is expanded downstream of the part where the width of the flow path through which the resin composition flows is narrowed.

  Next, details of the resin composition will be described.

(Details of resin composition)
From the viewpoint of effectively increasing the tensile strength and flexibility, the resin composition preferably includes a thermoplastic resin, more preferably includes a polyolefin-based resin or a polystyrene-based resin, and further includes a polyolefin-based resin. It is particularly preferable that (A) a polypropylene resin is included. From the viewpoint of effectively increasing the tensile strength and flexibility, it is preferable to include a thermoplastic resin and at least one of (B) an olefin-based thermoplastic elastomer and (C) a polyethylene-based plastomer. It is particularly preferable that the resin contains a polypropylene resin and at least one of (B) an olefin thermoplastic elastomer and (C) a polyethylene plastomer.

  From the viewpoint of effectively increasing the tensile strength and flexibility and further improving the surface condition, the resin composition contains both (B) an olefin-based thermoplastic elastomer and (C) a polyethylene-based plastomer. Is preferred.

  The resin composition does not contain (D) a black pigment or contains. In the foamed sheet having a good surface state, the resin composition may contain (D) a black pigment from the viewpoint of making folds (corrugated) and stains less noticeable.

  The resin composition does not contain or contain (E) a cell core material. From the viewpoint of obtaining a foam sheet having good flexibility, the resin composition may contain (E) a cell core material.

  Only one type of thermoplastic resin, polyolefin resin, (A) polypropylene resin, (B) olefin thermoplastic elastomer, (C) polyethylene plastomer, (D) black pigment, and (E) cell core material are used. Or two or more of them may be used in combination.

  The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resins, polystyrene resins, polyester resins, thermoplastic epoxy resins, polyamide resins, thermoplastic polyurethane resins, sulfide resins, and acrylic resins. From the viewpoint of effectively increasing the tensile strength and flexibility, a polyolefin-based resin or a polystyrene-based resin is preferable.

  The polyolefin resin is not particularly limited, and examples thereof include a polyethylene resin and a polypropylene resin. From the viewpoint of effectively increasing breakage prevention and flexibility, a polyethylene resin, a polypropylene resin, or a polystyrene resin is preferable.

  (A) A polypropylene resin is obtained by polymerizing a propylene monomer. (A) The polypropylene resin is a polymer. The polymer includes a copolymer. (A) As a polypropylene resin, the homopolymer of a propylene monomer and the copolymer of the polymerization component which has a propylene monomer as a main component are mentioned. In the copolymer of the polymerization component mainly composed of the propylene monomer, the content of the propylene monomer is 50% by weight or more, preferably 80% by weight or more, more preferably 90% by weight in 100% by weight of the polymerizable polymerization component. % By weight or more The form of copolymerization may be random or block.

  Specific examples of (A) polypropylene resins include propylene homopolymers, propylene random polymers, and propylene block polymers. (A) The polypropylene resin is preferably a homopolymer of a propylene monomer, and is preferably a propylene homopolymer.

  The melt flow rate (MFR) of the thermoplastic resin and the (A) polypropylene resin is preferably 0.1 g / 10 min or more, more preferably 0.15 g / 10, under the conditions of a test temperature of 230 ° C. and a load of 21.18 N. Min. Or more, more preferably 0.2 g / 10 min or more, preferably 5 g / 10 min or less. When the MFR of the thermoplastic resin and the (A) polypropylene resin is not less than the above lower limit and not more than the above upper limit, a foamed sheet having a higher tensile strength and a better surface state can be obtained.

  From the viewpoint of effectively increasing the tensile strength and flexibility and further improving the surface state, the melt tension at 230 ° C. of the thermoplastic resin and the (A) polypropylene resin is preferably 0.3 cN or more, More preferably, it is 0.5 cN or more, preferably 35 cN or less, more preferably 20 cN or less. Further, when the melt tension is not less than the above lower limit and not more than the above upper limit, the bubbles can be made finer, and the surface roughness of the foam sheet is effectively reduced.

  (B) The olefin-based thermoplastic elastomer preferably has a structure in which a hard segment and a soft segment are combined. (B) The olefin-based thermoplastic elastomer has rubber properties at room temperature (25 ° C.) and has a property that it can be molded and molded at a high temperature in the same manner as a thermoplastic resin.

  (B) The olefinic thermoplastic elastomer is generally a polyolefin resin such as a polypropylene or polyethylene hard segment, and a rubber such as an ethylene-propylene-diene copolymer or ethylene-propylene copolymer as a soft segment. Ingredient or amorphous polyethylene.

  (B) As the olefinic thermoplastic elastomer, polymerization of a hard segment monomer and a soft segment monomer is performed in multiple stages and directly produced in a polymerization reaction vessel; Banbury mixer or biaxial Blend-type elastomer produced by physically dispersing polyolefin resin as hard segment and rubber component as soft segment using kneader such as extruder; Banbury mixer or twin screw extruder Using a kneader, the rubber component is completely cross-linked in the polyolefin resin matrix by adding a cross-linking agent when physically dispersing the polyolefin resin that becomes the hard segment and the rubber component that becomes the soft segment. Or partially cross-linked and micro-dispersed Dynamic crosslinked elastomer used and the like.

  (B) It is possible to use both a non-crosslinked elastomer and a crosslinked elastomer as the olefinic thermoplastic elastomer. From the viewpoint of improving the recyclability of the foamed sheet, a non-crosslinked elastomer produced by physically dispersing a polyolefin-based resin serving as a hard segment and a rubber component serving as a soft segment is preferable. Moreover, such a non-crosslinked elastomer can be suitably used for extrusion foam molding with the annular die. Furthermore, even when such a non-crosslinked elastomer is used, even when the foamed sheet is recycled and supplied again to the extruder for extrusion foam molding, foaming failure due to the crosslinked rubber can be suppressed.

  (B) Specific examples of the olefin-based thermoplastic elastomer include olefin-based elastomers such as ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, and chlorinated polyethylene; styrene-based elastomers; polyester-based elastomers Polyamide-based elastomers; polyurethane-based elastomers and the like.

  (B) When the olefinic thermoplastic elastomer is an ethylene-propylene-diene copolymer elastomer, examples of the diene component include ethylidene norbornene, 1,4-hexadiene, and dicyclopentadiene. Such an ethylene-propylene-diene copolymer elastomer can be suitably used for extrusion foam molding with the above annular die. Only one type of ethylene-propylene-diene copolymer elastomer may be used, or two or more types may be used in combination.

  From the viewpoint of effectively increasing the tensile strength and flexibility and further improving the surface condition, (B) the olefin-based thermoplastic elastomer has an MFR at a test temperature of 230 ° C. and a load of 21.18 N. Preferably, the MFR of (B) the olefinic thermoplastic elastomer is preferably 1 g / 10 min or more, and preferably 15 g / 10 min or less. (B) When the MFR of the olefinic thermoplastic elastomer is not less than the above lower limit and not more than the above upper limit, a foamed sheet having a higher tensile strength and a better surface state can be obtained.

  Examples of the (C) polyethylene plastomer include a polyethylene polymer containing a polyolefin resin and a copolymer component such as an α-olefin.

  As the α-olefin, an α-olefin having 4 to 8 carbon atoms is preferable, and 1-butene, 1-hexene or 1-octene is more preferable.

  Examples of the ethylene / α-olefin copolymer include “Esprene NO416” (ethylene-1-butene copolymer) manufactured by Sumitomo Chemical Co., Ltd. and “Kernel KS240T” (ethylene-1-hexene copolymer) manufactured by Nippon Polyethylene Co., Ltd. And “Affinity EG8100” (ethylene-1-octene copolymer) manufactured by Dow Chemical.

(C) density of the polyethylene-based plastomer, preferably 0.85 g / cm ³ or more, preferably 0.91 g / cm ³ or less. When the density is equal to or higher than the lower limit, the tensile strength of the foam sheet is effectively increased. When the density is not more than the above upper limit, the flexibility of the foam sheet is further increased.

  From the viewpoint of effectively increasing the tensile strength and flexibility and further improving the surface condition, the (C) polyethylene-based plastomer may have an MFR at a test temperature of 190 ° C. and a load of 21.18 N. Preferably, the MFR of the (C) polyethylene plastomer is preferably 1 g / 10 min or more, and preferably 15 g / 10 min or less.

  From the viewpoint of effectively increasing the tensile strength and flexibility and further improving the surface condition, the resin composition comprises a thermoplastic resin, (B) an olefin-based thermoplastic elastomer, and (C) a polyethylene-based plastomer. In the total 100% by weight, the thermoplastic resin content is preferably 10% by weight or more, more preferably 15% by weight or more, still more preferably 20% by weight or more, preferably 90% by weight or less, more preferably 85% by weight or less. The total content of (B) the olefinic thermoplastic elastomer and (C) the polyethylene plastomer is preferably 10% by weight or more, more preferably 15% by weight or more, still more preferably 80% by weight or less. Is 20% by weight or more, preferably 90% by weight or less, more preferably 85% by weight or less, and still more preferably 80% by weight or less. A.

  From the viewpoint of effectively increasing the tensile strength and flexibility and further improving the surface state, in the resin composition, (A) a polypropylene resin, (B) an olefin thermoplastic elastomer, and (C) a polyethylene resin. In the total 100% by weight with the plastomer, the content of the (A) polypropylene resin is preferably 10% by weight or more, more preferably 15% by weight or more, still more preferably 20% by weight or more, and preferably 90% by weight or less. The total content of (B) the olefinic thermoplastic elastomer and (C) the polyethylene plastomer is preferably 10% by weight or more, more preferably 15% by weight or less, more preferably 85% by weight or less. % By weight or more, more preferably 20% by weight or more, preferably 90% by weight or less, more preferably 85% by weight or less, To preferably 80 wt% or less.

  In the resin composition, the weight ratio of the content of (C) polyethylene plastomer to the content of (B) olefin thermoplastic elastomer (content of (C) / content of (B)) is preferably 5 / 95 or more, more preferably 10/90 or more, further preferably 15/85 or more, particularly preferably 20/80 or more, preferably 95/5 or less, more preferably 90/10 or less, still more preferably 85/10 or less, Especially preferably, it is 80/20 or less. When the weight ratio (content of (C) / content of (B)) is not less than the above lower limit and not more than the above upper limit, the breakage prevention property and flexibility are effectively enhanced, and the surface state is further improved. Become. In addition, as a result of effectively increasing the expansion ratio, the flexibility of the foam sheet can be further increased.

  In the resin composition, the total content of the thermoplastic resin, (B) the olefinic thermoplastic elastomer and (C) the polyethylene plastomer is preferably 80% by weight or more, more preferably 90% by weight or more, preferably 100% by weight. % (Total amount) or less.

  In the resin composition, the total content of (A) polypropylene resin, (B) olefin thermoplastic elastomer and (C) polyethylene plastomer is preferably 80% by weight or more, more preferably 90% by weight or more, preferably Is less than 100% by weight (total amount).

  In the resin composition, the content of (D) the black pigment is preferably 2% by weight or more, more preferably 4% by weight or more, preferably 20% by weight or less, more preferably 15% by weight or less.

  The melt flow rate (MFR) of the resin composition is preferably 0.1 g / 10 min or more, more preferably 0.15 g / 10 min or more, still more preferably 0.2 g / 10 min or more, particularly preferably 0.25 g. / 10 min or more, preferably 5 g / 10 min or less, more preferably 4.5 g / 10 min or less, still more preferably 4 g / 10 min or less. When the MFR of the resin composition is not less than the above lower limit and not more than the above upper limit, the tensile strength and flexibility are effectively increased, and the surface state is further improved. When the MFR of the resin composition is equal to or higher than the lower limit, the load on the extruder is reduced, the foam sheet productivity is increased, and the resin composition efficiently flows through the resin flow path of the annular die.

  The MFR of the thermoplastic resin, (A) polypropylene resin, (B) olefin thermoplastic elastomer, (C) polyethylene plastomer and resin composition is a test temperature of 230 ° C. in accordance with B method of JIS K7210: 1999. Alternatively, it is measured under the conditions of 190 ° C. and a load of 21.18N.

  From the viewpoint of effectively increasing the tensile strength and flexibility and further improving the surface state, the melt tension at 230 ° C. of the resin composition is preferably 0.1 cN or more, more preferably 0.2 cN or more. , Preferably 30 cN or less, more preferably 25 cN or less. Moreover, a bubble can be made still finer as melt tension is more than the said minimum and below the said upper limit.

  The melt tension of the thermoplastic resin, (A) polypropylene resin and resin composition is measured under conditions of a test temperature of 230 ° C. and a load of 21.18N.

  Along with the resin composition, various additives may be used as necessary within the range not impairing the effects of the present invention. The above additives include surfactants, dispersants, weathering stabilizers, light stabilizers, pigments, dyes, flame retardants, plasticizers, lubricants, UV absorbers, antioxidants, fillers, reinforcing agents, and antistatic agents. Agents and the like. By using the surfactant, the slipperiness and the anti-blocking property are further enhanced. By using the dispersant, the dispersibility of each compounding component is increased. Examples of the dispersant include higher fatty acids, higher fatty acid esters and higher fatty acid amides.

(Other details of foam sheet and foam sheet production method)
For foam molding, carbon dioxide (carbon dioxide) or the like is suitably used as a foaming agent.

  At the time of foam molding, it is preferable that a sea-island structure is formed in the resin composition, and the thermoplastic resin or (A) polypropylene-based resin is the sea part, (B) olefin-based thermoplastic elastomer and (C) polyethylene-based plastomer It is preferable that at least one of the islands is an island. In this case, when shear is applied to the resin composition, the island portion expands and contracts, so that the viscosity of the resin composition is appropriately increased. In order to make (B) an olefinic thermoplastic elastomer and (C) a polyethylene plastomer a good island, the hardness (duro hardness) of the thermoplastic resin or (A) polypropylene resin is (B) olefinic thermoplasticity. It is preferably higher than the hardness (duro hardness) of the elastomer and (C) polyethylene plastomer. The hardness of the thermoplastic resin or (A) polypropylene resin is preferably D50 or more, and the hardness of (B) the olefin thermoplastic elastomer and (C) polyethylene plastomer is preferably less than D50. From the viewpoint of appropriately increasing the viscosity of the resin composition when shear is imparted to the resin composition, the hardness of (B) the olefin thermoplastic elastomer and (C) the polyethylene plastomer is preferably D10 or more.

  The annular die is attached to the tip of the extruder. The resin composition is melt-kneaded in the extruder. Examples of the extruder include a single-screw extruder, a twin-screw extruder, and a tandem extruder. A tandem type extruder is preferred because the extrusion conditions can be easily controlled.

  The extrusion rate of the resin composition in the bubble generation part of the resin flow path is preferably 15 kg / hour or more, preferably 50 kg / hour or less. When the extrusion amount is not less than the above lower limit and not more than the above upper limit, a foamed sheet having a higher tensile strength and a better surface state can be obtained, the foaming ratio can be further increased, and the bubbles can be made finer. And a foamed sheet having an appropriate open cell rate and appropriate bubble breaking rate can be obtained.

  The extrusion amount is the total weight of the extrudate (resin composition, foaming agent, etc.) extruded from the annular die.

  From the viewpoint of appropriately increasing the foamability, the melting temperature of the resin composition is preferably T + 10 ° C. or higher, preferably T + 30 ° C. or lower, when the melting point of the thermoplastic resin or (A) polypropylene resin is T ° C. is there. When the melting temperature is equal to or higher than the lower limit, crystallization of the thermoplastic resin or (A) polypropylene resin is difficult to start, and an excessive increase in viscosity of the melt is suppressed. When the melting temperature is not more than the above upper limit, the solidification speed and foaming speed after foaming become appropriate, and the foaming ratio can be increased moderately.

  In the foam and the foam sheet, the number of cells in the thickness direction is preferably 2 or more, and more preferably 3 or more. That is, it is preferable that two or more or three or more bubbles are arranged on a straight line connecting the surfaces of both sides of the foam and the foam sheet in the thickness direction. When the number of bubbles in the thickness direction is 3 or more, the flexibility of the foam sheet is further increased. The upper limit of the number of cells in the thickness direction can be appropriately adjusted depending on the thickness of the foam and the foamed sheet and the average cell diameter, and is not particularly limited. The number of bubbles in the thickness direction may be 50 or less.

  The use of the foam sheet is not particularly limited. Foamed sheets are used for packaging cushioning materials, automotive structural members, and the like. In addition, since the foam sheet is excellent in workability and flexibility, it is used as a pressure-sensitive adhesive sheet for electronic / electric equipment, a base material for a sealing material, and the like.

  An adhesive sheet can be obtained by disposing an adhesive layer on one surface of the foam sheet. This pressure-sensitive adhesive sheet includes a foamed sheet and a pressure-sensitive adhesive layer disposed on one surface of the foamed sheet. In this pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer may be disposed on the other surface of the foamed sheet, or the pressure-sensitive adhesive layer may be disposed on the surfaces on both sides of the foamed sheet.

  The foamed sheet is preferably used for an adhesive sheet for electronic / electrical equipment, and more preferably used for an adhesive sheet for wearable computers. The pressure-sensitive adhesive sheet is preferably a pressure-sensitive adhesive sheet for electronic / electric equipment, and is preferably a pressure-sensitive adhesive sheet for wearable computers. In such a use, it is calculated | required that especially the thickness of a foam sheet and an adhesive sheet is thin. In the present invention, although it is thin, it is difficult to break and has high flexibility. Therefore, in electronic and electrical equipment such as wearable computers, the foam sheet and the pressure-sensitive adhesive sheet are prevented from being broken, and the foam sheet and the pressure-sensitive adhesive sheet absorb the impact. Can increase the sex.

  The present invention will be described in more detail with reference to the following examples. The present invention is not limited only to the following examples.

Example 1
100 parts by weight of polypropylene resin (MFR: 0.3 g / 10 min, “E110G” manufactured by Prime Polymer Co., Ltd.), 7 parts by weight of talc (average particle diameter: 13 μm) as a cell core material, and pigment (“PPM OYA164 BLK manufactured by Toyochem Co., Ltd.) -FD ") was mixed with 10 parts by weight to prepare a resin composition.

  A tandem type extruder in which a second extruder with a diameter of 75 mm was connected to the tip of a first extruder with a diameter of 65 mm was prepared. The obtained resin composition was supplied to the first extruder of the tandem type extruder and melt kneaded. In the middle of the first extruder, 4.5 parts by weight of supercritical carbon dioxide is injected as a foaming agent, and the molten resin composition and carbon dioxide are uniformly mixed and kneaded, and then a molten resin containing the foaming agent. The composition was continuously supplied to the second extruder and cooled to a resin temperature suitable for foaming while melt-kneading.

  Thereafter, from a die ring attached to the tip of the second extruder (bubble generation part diameter φ 36 mm, foam molding part outlet diameter φ 70 mm), discharge rate 30 kg / hr, melt temperature 176 ° C., ring die A cylindrical foam was obtained by extrusion foaming under the condition of a melt pressure of 12.0 MPa in front. The cylindrical foam molded in the foam molding part of the annular die was put on a cooled mandrel, and the outer surface was cooled by blowing air from the air ring. The cooled cylindrical foam was cut with a cutter at one point on the mandrel to obtain a resin foam sheet having an average thickness of 2.0 mm.

  One side of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 0.5 mm was obtained by slicing one side.

  Next, a dielectric heating roll is prepared as a heat source, the heating temperature (pressing temperature) is 110 ° C., the nip roll pressure (pressing pressure) is 0.3 MPa, and the contact time between the dielectric heating roll and the foam is 3.0 seconds. The resulting foam was passed between a dielectric heating roll and a nip roll. At this time, the surface of the obtained foam which was not sliced was brought into contact with a dielectric heating roll. As a result, a foamed sheet (after heat pressing) having an average thickness of 0.10 mm was obtained from the surface side that was not sliced.

  The obtained foamed sheet is compressed at a compression rate of 80% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 2)
60 parts by weight of a polypropylene resin (MFR: 0.3 g / 10 minutes, “E110G” manufactured by Prime Polymer) and 40 parts by weight of a thermoplastic elastomer (MFR: 1.5 g / 10 minutes, “R110E” manufactured by Prime Polymer) In addition, 100 parts by weight of the blended resin composition was prepared.

  To 100 parts by weight of the obtained blended resin composition, 7 parts by weight of talc (average particle size 13 μm) as a cell core material and 10 parts by weight of a pigment (“PPM OYA164 BLK-FD” manufactured by Toyochem Co., Ltd.) A resin composition was prepared.

  Except having used the obtained resin composition, it carried out similarly to Example 1, and obtained the resin foam sheet of average thickness 2.0mm.

  One side of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 0.5 mm was obtained by slicing one side.

  Heating was performed from the surface side not sliced in the same manner as in Example 1 except that the obtained foam was used and that the contact time between the dielectric heating roll and the foam was changed to 1.0 second. A foamed sheet that was pressed and had an average thickness of 0.15 mm was obtained.

  The obtained foam sheet is compressed at a compression rate of 70% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 3)
60 parts by weight of a polypropylene resin (MFR: 0.3 g / 10 min, “E110G” manufactured by Prime Polymer) and 20 parts by weight of a thermoplastic elastomer (MFR: 1.5 g / 10 min, “R110E” manufactured by Prime Polymer) Then, 20 parts by weight of polyethylene (MFR: 2.2 g / 10 min, “KS240T” manufactured by Nippon Polyethylene Co., Ltd.), which is a metallocene plastomer, was added to prepare 100 parts by weight of the compounded resin composition.

  To 100 parts by weight of the obtained blended resin composition, 7 parts by weight of talc (average particle size 13 μm) as a cell core material and 10 parts by weight of a pigment (“PPM OYA164 BLK-FD” manufactured by Toyochem Co., Ltd.) A resin composition was prepared.

  Except having used the obtained resin composition, it carried out similarly to Example 1, and obtained the resin foam sheet of average thickness 2.0mm.

  One side of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 0.5 mm was obtained by slicing one side.

  Heating was performed from the surface side not sliced in the same manner as in Example 1 except that the obtained foam was used and the contact time between the dielectric heating roll and the foam was changed to 0.5 seconds. A foamed sheet that was pressed and had an average thickness of 0.10 mm was obtained.

  The obtained foamed sheet is compressed at a compression rate of 80% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

Example 4
The foam obtained in Example 3 was prepared.

  Example 1 was used except that the obtained foam was used, the heating temperature was changed to 130 ° C., and the contact time between the dielectric heating roll and the foam was changed to 0.5 seconds. The foamed sheet was heated and pressed from the surface side that was not sliced, and the average thickness was 0.05 mm.

  The obtained foam sheet is compressed at a compression rate of 90% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 5)
The foam obtained in Example 3 was prepared.

  The same as in Example 1 except that the obtained foam was used, the heating temperature was changed to 90 ° C., and the contact time between the dielectric heating roll and the foam was changed to 0.5 seconds. The foamed sheet was heated and pressed from the surface side not sliced, and the average thickness was 0.15 mm.

  The obtained foam sheet is compressed at a compression rate of 70% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 6)
The foam obtained in Example 3 was prepared.

  The same as in Example 1 except that the obtained foam was used, the heating temperature was changed to 70 ° C., and the contact time between the dielectric heating roll and the foam was changed to 0.5 seconds. The foamed sheet was heated and pressed from the surface side that was not sliced, and the average thickness was 0.20 mm.

  The obtained foam sheet is compressed at a compression rate of 60% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 7)
The foam obtained in Example 3 was prepared.

  Except that the obtained foam was used, the heating temperature was changed to 60 ° C., and the contact time between the dielectric heating roll and the foam was changed to 0.5 seconds, as in Example 1. The foamed sheet was heated and pressed from the surface side that was not sliced and had an average thickness of 0.25 mm.

  The obtained foamed sheet is compressed with respect to the foam at a compression rate of 50%. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 8)
The foam obtained in Example 3 was prepared.

  Except that the obtained foam was used, that the heating temperature was changed to 50 ° C., and that the contact time between the dielectric heating roll and the foam was changed to 0.5 seconds, the same as in Example 1. The foamed sheet was heated and pressed from the surface side that was not sliced, and the average thickness was 0.30 mm.

  The obtained foam sheet is compressed at a compression rate of 40% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

Example 9
100 parts by weight of a polyethylene resin (MFR: 0.2 g / 10 min, “DFD67676” manufactured by NUC), 7 parts by weight of talc (average particle diameter: 13 μm) as a cell core material, and pigment (“PPM OYA164 BLK manufactured by Toyochem Co., Ltd.) -FD ") was mixed with 10 parts by weight to prepare a resin composition.

  An average thickness of 2.5 mm was obtained in the same manner as in Example 1 except that the obtained resin composition was used, the melt temperature was changed to 115 ° C., and the melt pressure was changed to 10.0 MPa. A resin foam sheet was obtained.

  One surface of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 1.0 mm obtained by slicing one surface was obtained.

  Except that the obtained foam was used and the heating temperature was changed to 80 ° C., it was heated and pressed from the surface side that was not sliced in the same manner as in Example 1, and the average thickness was 0.00. A foam sheet of 10 mm was obtained.

  The obtained foam sheet is compressed at a compression rate of 90% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 10)
40 parts by weight of a thermoplastic elastomer (MFR: 11 g / 10 minutes, “Z101N” manufactured by Mitsubishi Chemical Co., Ltd.) is added to 60 parts by weight of a polyethylene resin (MFR: 0.2 g / 10 minutes, manufactured by NUC “DFDJ6776”). 100 parts by weight of the blended resin composition was prepared.

  To 100 parts by weight of the obtained blended resin composition, 7 parts by weight of talc (average particle size 13 μm) as a cell core material and 10 parts by weight of a pigment (“PPM OYA164 BLK-FD” manufactured by Toyochem Co., Ltd.) A resin composition was prepared.

  An average thickness of 2.5 mm was obtained in the same manner as in Example 1 except that the obtained resin composition was used, the melt temperature was changed to 115 ° C., and the melt pressure was changed to 10.0 MPa. A resin foam sheet was obtained.

  One surface of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 1.0 mm obtained by slicing one surface was obtained.

  Except that the obtained foam was used, that the heating temperature was changed to 80 ° C., and that the contact time between the dielectric heating roll and the foam was changed to 1.0 second, the same as in Example 1. The foamed sheet was heated and pressed from the surface side not sliced, and the average thickness was 0.12 mm.

  The obtained foam sheet is compressed at a compression rate of 88% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 11)
60 parts by weight of a polyethylene resin (MFR: 0.2 g / 10 min, “DFD67676” manufactured by NUC), 20 parts by weight of a thermoplastic elastomer (MFR: 11 g / 10 min, “Z101N” manufactured by Mitsubishi Chemical Corporation), and metallocene 20 parts by weight of polyethylene as a plastomer (MFR: 2.2 g / 10 min, “KS240T” manufactured by Nippon Polyethylene Co., Ltd.) was added to prepare 100 parts by weight of the compounded resin composition.

  To 100 parts by weight of the obtained blended resin composition, 7 parts by weight of talc (average particle size 13 μm) as a cell core material and 10 parts by weight of a pigment (“PPM OYA164 BLK-FD” manufactured by Toyochem Co., Ltd.) A resin composition was prepared.

  An average thickness of 2.5 mm was obtained in the same manner as in Example 1 except that the obtained resin composition was used, the melt temperature was changed to 115 ° C., and the melt pressure was changed to 10.0 MPa. A resin foam sheet was obtained.

  One surface of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 1.0 mm obtained by slicing one surface was obtained.

  Example 1 was used except that the obtained foam was used, the heating temperature was changed to 80 ° C., and the contact time between the dielectric heating roll and the foam was changed to 0.5 seconds. The foamed sheet was heated and pressed from the surface side that was not sliced, and the average thickness was 0.07 mm.

  The obtained foam sheet is compressed with a compression ratio of 93% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 12)
100 parts by weight of a polystyrene resin (MFR: 1.6 g / 10 min, “HRM26” manufactured by Toyo Styrene Co., Ltd.), 7 parts by weight of talc (average particle diameter: 13 μm) as a cell core material, and pigment (“PPM OYA164 manufactured by Toyochem Co., Ltd.) BLK-FD ") and 10 parts by weight were mixed to prepare a resin composition.

  In the same manner as in Example 1 except that the obtained resin composition was used, the melt temperature was changed to 15.3 ° C., and the melt pressure was changed to 9.0 MPa, an average thickness of 2. A 0 mm resin foam sheet was obtained.

  One side of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 0.5 mm was obtained by slicing one side.

  Except that the obtained foam was used and the heating temperature was changed to 130 ° C., it was heated and pressed from the surface side that was not sliced in the same manner as in Example 1, and the average thickness was 0.00. A foam sheet of 20 mm was obtained.

  The obtained foam sheet is compressed at a compression rate of 60% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 13)
40 parts by weight of thermoplastic elastomer (MFR: 0.4 g / 10 min, JSR “3400B”) is added to 60 parts by weight of polystyrene resin (MFR: 1.6 g / 10 min, “HRM26” manufactured by Toyo Styrene Co., Ltd.) In addition, 100 parts by weight of the blended resin composition was prepared.

  To 100 parts by weight of the obtained blended resin composition, 7 parts by weight of talc (average particle size 13 μm) as a cell core material and 10 parts by weight of a pigment (“PPM OYA164 BLK-FD” manufactured by Toyochem Co., Ltd.) A resin composition was prepared.

  The average thickness of 2.0 mm was obtained in the same manner as in Example 1 except that the obtained resin composition was used, the melt temperature was changed to 150 ° C., and the melt pressure was changed to 9.5 MPa. A resin foam sheet was obtained.

  One side of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 0.5 mm was obtained by slicing one side.

  Except that the obtained foam was used, the heating temperature was changed to 130 ° C., and the contact time between the dielectric heating roll and the foam was changed to 1.0 second, as in Example 1. The foamed sheet was heated and pressed from the surface side that was not sliced and had an average thickness of 0.25 mm.

  The obtained foamed sheet is compressed with respect to the foam at a compression rate of 50%. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Example 14)
To 60 parts by weight of a polystyrene-based resin (MFR: 1.6 g / 10 min, “HRM26” manufactured by Toyo Styrene Co., Ltd.), 20 parts by weight of a thermoplastic elastomer (MFR: 11 g / 10 min, “Z101N” manufactured by Mitsubishi Chemical Corporation), 20 parts by weight of polyethylene (MFR: 2.2 g / 10 min, “KS240T” manufactured by Nippon Polyethylene Co., Ltd.), which is a metallocene plastomer, was added to prepare 100 parts by weight of the compounded resin composition.

  To 100 parts by weight of the obtained blended resin composition, 7 parts by weight of talc (average particle size 13 μm) as a cell core material and 10 parts by weight of a pigment (“PPM OYA164 BLK-FD” manufactured by Toyochem Co., Ltd.) A resin composition was prepared.

  The average thickness of 2.0 mm was obtained in the same manner as in Example 1 except that the obtained resin composition was used, the melt temperature was changed to 150 ° C., and the melt pressure was changed to 9.5 MPa. A resin foam sheet was obtained.

  One side of the obtained resin foam sheet was sliced by a splitting machine to remove the skin, and a foam (average sheet thickness before heating and pressing) having an average thickness of 0.5 mm was obtained by slicing one side.

  Example 1 was used except that the obtained foam was used, the heating temperature was changed to 130 ° C., and the contact time between the dielectric heating roll and the foam was changed to 0.5 seconds. The foamed sheet was heated and pressed from the surface side not sliced, and the average thickness was 0.15 mm.

  The obtained foam sheet is compressed at a compression rate of 70% with respect to the foam. It was possible to crush easily. When the thickness after 24 hours was observed, there was no restoration over time and the shape was maintained.

(Comparative Example 1)
The resin composition obtained in Example 2 was prepared.

  In the same manner as in Example 1, except that the obtained resin composition was used and 2.0 parts by weight of carbon dioxide in a supercritical state was injected as a foaming agent from the middle of the first extruder, an average thickness of 0. A 5 mm resin foam sheet was obtained. This resin foam sheet was used as a foam without slicing.

  The obtained foam was used, the contact time between the dielectric heating roll and the foam was changed to 1.0 second, and the surface on one side of both sides that was not sliced was brought into contact with the dielectric heating roll. In the same manner as in Example 1, a foamed sheet that was hot-pressed from the non-sliced surface side and had an average thickness of 0.35 mm was obtained.

  The obtained foam sheet is compressed at a compression rate of 30% with respect to the foam.

(Comparative Example 2)
The resin foam sheet obtained in Example 2 was prepared.

  Both surfaces of the obtained resin foam sheet were sliced with a splitting machine to remove the outer skin, and a foam having an average thickness of 0.5 mm (sheet before heating and pressing) was obtained by slicing both surfaces.

  The obtained foam was used, the contact time between the dielectric heating roll and the foam was changed to 1.0 second, and the surface on one side of the sliced sides was brought into contact with the dielectric heating roll. Except for this, a foamed sheet having an average thickness of 0.15 mm was obtained by heat pressing from one side of the sliced process in the same manner as in Example 1.

  The obtained foam sheet is compressed at a compression rate of 70% with respect to the foam.

(Comparative Example 3)
The resin composition obtained in Example 10 was prepared.

  An average thickness of 1. was obtained in the same manner as in Example 1 except that the obtained resin composition was used and 6.0 parts by weight of carbon dioxide in a supercritical state was injected from the middle of the first extruder as a blowing agent. A 0 mm resin foam sheet was obtained. This resin foam sheet was used as a foam without slicing.

  Using the obtained foam, changing the heating temperature to 80 ° C., changing the contact time between the dielectric heating roll and the foam to 1.0 second, Except that the surface on one side was brought into contact with the dielectric heating roll, a foamed sheet that was hot-pressed from the surface side that was not sliced and had an average thickness of 0.75 mm was obtained in the same manner as in Example 1. .

  The obtained foamed sheet is compressed at a compression rate of 25% with respect to the foam.

(Comparative Example 4)
The resin foam sheet obtained in Example 10 was prepared.

  Both surfaces of the obtained resin foam sheet were sliced with a splitting machine to remove the outer skin, and a foam having an average thickness of 1.0 mm (before heating press, sheet original fabric) obtained by slicing both surfaces was obtained.

  Using the obtained foam, changing the heating temperature to 80 ° C., changing the contact time between the dielectric heating roll and the foam to 1.0 second, and one side of the sliced sides A foamed sheet having an average thickness of 0.25 mm was obtained by being heat-pressed from one side of the sliced process in the same manner as in Example 1 except that the surface was contacted with a dielectric heating roll.

  The obtained foam sheet is compressed at a compression rate of 75% with respect to the foam.

(Comparative Example 5)
The resin composition obtained in Example 13 was prepared.

  In the same manner as in Example 1, except that the obtained resin composition was used and 3.0 parts by weight of carbon dioxide in a supercritical state was injected as a foaming agent from the middle of the first extruder, an average thickness of 0. A 5 mm resin foam sheet was obtained. This resin foam sheet was used as a foam without slicing.

  Using the obtained foam, changing the heating temperature to 130 ° C., changing the contact time between the dielectric heating roll and the foam to 1.0 seconds, and on both sides of the non-sliced side Except that the surface on one side was brought into contact with the dielectric heating roll, a foamed sheet having been heated and pressed from the non-sliced surface side in the same manner as in Example 1 and having an average thickness of 0.30 mm was obtained. .

  The obtained foam sheet is compressed at a compression rate of 40% with respect to the foam.

(Comparative Example 6)
The resin foam sheet obtained in Example 13 was prepared.

  Both surfaces of the obtained resin foam sheet were sliced with a splitting machine to remove the outer skin, and a foam having an average thickness of 0.5 mm (sheet before heating and pressing) was obtained by slicing both surfaces.

  Using the obtained foam, changing the heating temperature to 130 ° C., changing the contact time between the dielectric heating roll and the foam to 1.0 second, and one side of the sliced sides A foamed sheet having an average thickness of 0.10 mm was obtained in the same manner as in Example 1 except that the surface was contacted with a dielectric heating roll.

  The obtained foamed sheet is compressed at a compression rate of 80% with respect to the foam.

(Comparative Example 7)
The resin sheet obtained in Example 3 was prepared.

  Both surfaces of the obtained resin foam sheet were sliced by a splitting machine to remove the skin, and a foam having an average thickness of 1.0 mm was obtained by slicing both surfaces.

  The obtained foam was used as a foam sheet of Comparative Example 7 without being hot-pressed.

(Comparative Example 8)
The foam obtained in Example 3 was prepared.

  Except that the obtained foam was used, the contact time between the dielectric heating roll and the foam was changed to 1.0 second, and the sliced surface of the foam was brought into contact with the dielectric heating roll. In the same manner as in Example 1, a foamed sheet that was hot-pressed from the sliced surface side and had an average thickness of 0.20 mm was obtained.

  The obtained foam sheet is compressed at a compression rate of 60% with respect to the foam.

(Evaluation)
(1) Average thickness Using a thickness gauge ("No.547-301" manufactured by Mitutoyo Corporation) and a thickness measuring device of size φ10 mm, the thickness of the obtained foam sheet in the width direction (TD direction) was measured under no load condition. 12 points were measured at intervals of 30 mm. The average value (arithmetic mean) of the measured values was taken as the average thickness (mm) of the foamed sheet.

(2) Average bubble diameter (exposed bubble cross section)
The average bubble diameter of the exposed bubble surface was determined. Specifically, the first surface portion and the second surface portion are made 100 times using a scanning electron microscope (“S-3000N” manufactured by Hitachi, Ltd. or “S-3400N” manufactured by Hitachi High-Technologies Corporation). The photo was taken with a magnification.

  The photographed image was printed on A4 paper, the number of bubbles present on a 60 mm straight line drawn on the printed photograph was measured, and the average bubble diameter was calculated by the following formula.

  Average bubble diameter (mm) = 60 / (number of bubbles × 100)

  The scale bar on the photograph was measured to 1/100 mm using “Digimatic Caliper” manufactured by Mitutoyo Co., Ltd., and the magnification of the photograph was obtained by the following formula.

  Photo magnification = Scale bar measured value (mm) / Scale bar display value (mm)

  Moreover, when drawing a straight line, a straight line of 60 mm was drawn in a direction passing through the major axis as much as possible in the bubble cross section.

(3) Number of exposed bubbles in the range of 1 mm ² The number was calculated using the photograph used in the measurement of the average bubble diameter. Specifically, the number of bubbles present in a 10 mm × 10 mm square drawn on the printed photograph used in the measurement of the average bubble diameter was visually counted, so that the number of exposed bubbles in the range of 1 mm ² was determined. It was the number.

(4) Tensile strength Tensilon universal testing machine UCT-10T (Orientec Co., Ltd.) and universal testing machine data processing software UTPS-458X (Soft Brain Co., Ltd.) were used to determine the values measured by the following method in the MD direction. And the tensile strength (MPa) of the foam sheet in the TD direction.

  Using a dumbbell-shaped No. 3 punching blade defined in JIS K6251: 2010, the foamed sheet was punched in the flow direction of the foamed sheet (MD direction: extrusion direction) to obtain five test pieces. The foamed sheet was punched in the width direction (TD direction: direction orthogonal to the extrusion direction) to obtain five test pieces.

  The test piece was conditioned in JIS K 7100: 1999 symbol “23/50” (temperature 23 ° C., relative humidity 50%) under a second grade standard atmosphere over 16 hours, and then under the same standard atmosphere. It was measured. The distance between the grips was measured at 50 mm and the test speed was 500 mm / min, and calculated according to the method defined in JIS K6251: 2010. However, the elongation was calculated from the distance between the grippers. The tensile strength TS (MPa) is calculated by the following formula.

TS = Fm / Wt
TS: Tensile strength (MPa)
Fm: Maximum force (N)
W: Width of the parallel part of the punching blade shape (mm)
t: thickness of parallel part (mm)

(5) 25% compressive stress Using the Tensilon universal testing machine (Orientec, model: UCT-10T) and universal testing machine data processing software (Soft Brain, product number: UTPS-458X), the following method The value measured at is taken as 25% compressive stress (kPa) of the foamed sheet.

  When the test piece size is 50 × 50 × 2 mm and the thickness of the test piece is 2 mm or more, the test piece is used as it is, and when the thickness of the test piece is less than 2 mm, the test pieces are stacked to have a thickness of about 2 mm. And

The width and length of the test piece were measured to 1/100 mm using a digital caliper (manufactured by Mitutoyo Corporation, product name: Digimatic caliper, model: CD-15), and the thickness of the test piece was measured using a Tensilon universal testing machine ( Compressed test piece using Orientec, model: UCT-10T, load cell: 10 kN, model: UR-1T-A-SR, above and below the point where the load is 2 N / 25 cm ² (0.8 kPa) Measure the distance between the compression plates to 1/100 mm and use it as the test start point.

The starting point of displacement is the test start point, the compression speed is 1 mm / min, and the stress at the time of 25% compression of the initial thickness (the compression load is 2 N / 25 cm ² ) is the compression stress. Three test pieces are measured, and the average of the compressive stress calculated by the following formula is defined as 25% compressive stress (kPa) of the foamed sheet.

σ ₂₅ = (F ₂₅ / A ₀ ) × 10 ³
σ ₂₅ : compressive stress (kPa)
F ₂₅ : Load at 25% deformation (N)
A ₀ : initial cross-sectional area of the specimen (mm ² )

  In addition, after adjusting the state of the test piece over a period of 16 hours or more in a second grade standard atmosphere, the symbol “23/50” (temperature 23 ° C., relative humidity 50%) of JIS K 7100: 1999, Measure with.

(6) IP code The IP code was measured as follows in accordance with the IP code measuring method based on the protection grade (IP code) by the outer shell of JIS C0920 electric machine.

  Using a test piece obtained by extracting a foam sheet of each thickness into a width of 2 mm and a length of 150 mm × width of 150 mm (inner diameter length of 148 mm × width of 148 mm), and sandwiching the test piece with an acrylic plate having a thickness of 3 mm, length of 200 mm × width of 200 mm, and a test sample It was. The test piece was uniformly sandwiched at the four corners of the acrylic plate so that the compression was 50% of the thickness.

  Non-protected IP00, protected against invasion of foreign solids with a diameter of 2.5mm or more, and IP31, exogenous with a diameter of 1.0mm or more that is not adversely affected by water drops falling vertically IP43, which is protected against intrusion of solids and is not adversely affected by water from spray water within 60 degrees from the vertical, is protected against intrusion of foreign solids with a diameter of 1.0 mm or more, In addition, IP44 was not adversely affected by splashes from any direction. IP57 was designated as an IP57 that does not hinder normal operation even if there is a slight intrusion of dust, and is not adversely affected even when immersed in water at a specified pressure and time.

  Details and results are shown in Tables 1 and 2 below.

  Moreover, the cross-sectional SEM (scanning electron microscope) image in the thickness direction of the foam sheet obtained by the manufacturing method of the foam sheet which concerns on FIG. 1 at one Embodiment of this invention was shown. In FIG. 2, the cross-sectional SEM image in the thickness direction of the foam (before heat compression process) used in order to obtain a foam sheet was shown.

Claims (10)

Foaming the resin composition so that a plurality of bubbles are exposed on the outer surface of the first surface portion on one side in the thickness direction, and the second surface portion on the other side in the thickness direction is a skin layer. A foaming process to obtain a body;
When the foam is heated and compressed, a plurality of bubbles are exposed on the outer surface of the first surface portion on one side in the thickness direction, and the second surface portion on the other side in the thickness direction is the skin layer. And a heat compression step for obtaining a foam sheet,
In the heating and compression step, the foam sheet is heated and compressed from the second surface portion side.   2. The method for producing a foam sheet according to claim 1, wherein, in the foaming step, a foam is obtained by slicing only the surface on one side in the thickness direction without slicing the surface on the other side in the thickness direction.   3. The method for producing a foam sheet according to claim 1, wherein, in the heat compression step, the foam is heated for 0.1 seconds or more and 5 seconds or less while being brought into contact with a heat source.   In the heating and compression step, the foam is heated and compressed while being in contact with a heat source, or the foam is heated while being in contact with a heat source, and then the foam is compressed during cooling. The manufacturing method of the foam sheet of any one of these.   In the heating and compression step, the foam is heated and compressed so that a ratio of a thickness of the obtained foam sheet to a thickness of the foam is 0.1 or more and 0.95 or less. The manufacturing method of the foam sheet of any one of Claims 1.   The manufacturing method of the foam sheet of any one of Claims 1-5 in which the said resin composition contains polypropylene resin.   The method for producing a foam sheet according to claim 6, wherein the resin composition contains a polypropylene resin and at least one of an olefin thermoplastic elastomer and a polyethylene plastomer.   In the resin composition, the total content of the polypropylene resin, the olefinic thermoplastic elastomer, and the polyethylene plastomer is 100% by weight, and the content of the polypropylene resin is 10% by weight or more and 90% by weight or less and the olefin. The method for producing a foam sheet according to claim 7, wherein the total content of the thermoplastic elastomer and the polyethylene plastomer is 10% by weight or more and 90% by weight or less.   The manufacturing method of the foam sheet of any one of Claims 1-8 which obtains the foam sheet whose 25% compressive stress is 10 kPa or more and 150 kPa or less. A foam sheet in which the number of exposed bubbles in the 1 mm ² range of the first surface portion is 20 or more and the number of exposed bubbles in the 1 mm ² range of the second surface portion is 10 or less. The manufacturing method of the foam sheet of any one of Claims 1-9 obtained.