Composite

Abstract

This composite comprises a foam layer and a base layer formed on at least one surface of the foam layer, wherein the base layer contains an inorganic substance. When the base layer is examined with a scanning electron microscope, slender regions each comprising a plurality of inorganic-substance particles linked in a row are observed.　The present invention can provide a composite which includes a foam layer and has a low content of bleeding components.

Description

Complex

[0001] The present invention relates to a composite comprising a foam layer and a substrate layer.

[0002] Due to their excellent flexibility and light weight, foams are used in a variety of fields, including automotive applications, electronic devices, consumer electronics, and residential building materials. While foams may be used as a single layer, it is also known to use them as laminates in which a non-foamed layer such as a resin film is laminated to a foam from the standpoint of processability and functionality. For example, Patent Document 1 discloses an invention relating to a foam laminate sheet for automotive interior materials, which comprises a foam layer having a base resin of a modified PPE resin, a non-foamed layer having a base resin of a thermoplastic resin laminated on both sides of the foam layer, a noise prevention layer laminated on one side of the foam laminate, and a skin material laminated on the other side via a multilayer hot-melt adhesive. It also describes that a substrate for automotive interior materials and automotive interior materials having excellent chemical resistance can be provided.

[0003] JP 2011-000810 A

[0004] However, in foamed materials and composites of foamed materials and non-foamed materials, blooming and bleeding due to low-molecular-weight components of the resin contained therein and various additives can occur, causing surface stickiness and contamination of the product to be used. For this reason, in recent years, there has been a strong demand for foamed materials with a low amount of bleeding components. Therefore, an object of the present invention is to provide a composite having a foam layer and with a low amount of bleeding components.

[0005] The present inventors conducted extensive research to solve the above-mentioned problems. As a result, they found that the above-mentioned problems can be solved by a composite including a foam layer and a substrate layer formed on at least one surface of the foam layer, the substrate layer containing an inorganic material, and when observed with a scanning electron microscope, the substrate layer has elongated regions in which a plurality of inorganic particles are connected in a string-like pattern, and thus completed the present invention. That is, the present invention provides the following [1] to [6].

[0006] [1] A composite comprising a foam layer and a substrate layer formed on at least one surface of the foam layer, wherein the substrate layer contains an inorganic material, and when the substrate layer is observed under a scanning electron microscope, elongated regions in which a plurality of inorganic particles are connected in a string-like pattern are observed. [2] The composite according to [1] above, wherein when the substrate layer is observed under a scanning electron microscope, a plurality of branched shapes formed by the inorganic particles are observed. [3] The composite according to [1] or [2] above, wherein at least one element belonging to the third period is observed in elemental analysis of the substrate layer. [4] The composite according to any one of [1] to [3] above, wherein Al and Si are observed in elemental analysis. [5] The composite according to any one of [1] to [4] above, wherein the substrate layer contains a resin. [6] The composite according to any one of [1] to [5] above, wherein the substrate layer exhibits at least one endothermic peak in a temperature range of 50 to 200°C when measured by differential scanning calorimetry (DSC).

[0007] According to the present invention, it is possible to provide a composite having a foam layer and having a small amount of bleeding components.

[0008] Fig. 1 is an SEM image of the surface of a substrate layer in one embodiment of the composite of the present invention. Fig. 2 is a diagram illustrating the aspect ratio of an elongated region. Fig. 3 is a cross-sectional view schematically showing one embodiment of the composite of the present invention. Fig. 4 is a cross-sectional view schematically showing another embodiment of the composite of the present invention. Fig. 5 is a cross-sectional view schematically showing another embodiment of the composite of the present invention.

[0009] The present invention will be described in detail below with reference to embodiments. [Composite] The composite of the present invention is a composite comprising a foam layer and a base layer formed on at least one surface of the foam layer, the base layer containing an inorganic material, and the base layer having an elongated region in which a plurality of inorganic particles are connected in a string-like pattern when observed with a scanning electron microscope.

[0010] <Substrate Layer> The substrate layer of the present invention contains an inorganic material, and when observed with a scanning electron microscope, the substrate layer has an elongated region (hereinafter sometimes abbreviated as an elongated region) in which a plurality of inorganic particles are connected in a string-like manner. By having an elongated region in the substrate layer, the amount of bleeding components from the substrate layer surface can be reduced. FIG. 1 shows a scanning electron microscope (SEM) image of one embodiment of the substrate layer surface in the present invention. FIG. 1 is a photograph of the surface of a substrate layer containing zeolite, an inorganic material, observed with a scanning electron microscope (SEM). More specifically, FIG. 1 is an image obtained by mapping Si elements within the field of view while observing the morphology with an energy dispersive X-ray analyzer (EDX) attached to the scanning electron microscope. In FIG. 1, a bright inorganic material is dispersed in a matrix made of a black resin. In the X portion of FIG. 1, a single inorganic particle is observed to exist. Meanwhile, in the Y and Z portions, elongated regions in which a plurality of inorganic particles are connected in a string-like manner are observed. The elongated region is a portion in which a plurality of inorganic particles are connected in a substantially unidirectional manner. The plurality of inorganic particles is preferably three or more inorganic particles, more preferably four or more inorganic particles, and even more preferably five or more inorganic particles. The upper limit of the number of connected inorganic particles is not particularly limited, but is, for example, 50.

[0011] The elongated region is a generally rod-shaped region and may have some bent portions, but when the longest line segment among those connecting any two points on the periphery of the elongated region is identified, all of the line segments pass through the elongated region. The elongated region does not include the inorganic particles that branch out from the portion where the inorganic particles are connected in a generally unidirectional manner (portion b shown in the figure).

[0012] The aspect ratio of the elongated region is 3 or more, preferably 4 or more, and more preferably 5 or more. The upper limit of the aspect ratio is not particularly limited, but is, for example, 50. FIG. 2 schematically shows the elongated region indicated by Y in FIG. 1 , and the aspect ratio of the elongated region is the ratio of the long diameter to the short diameter of the elongated region (long diameter / short diameter). The long diameter of the elongated region refers to the longest line segment connecting any two points on the periphery of the elongated region. The short diameter is the line segment connecting two points on the periphery of the elongated region, passing through the midpoint of the long diameter and perpendicular to the long diameter.

[0013] As explained above, the presence or absence of elongated regions can be confirmed by SEM-EDX measurement, and in this case, it is preferable to map elements according to the type of inorganic substance contained. Note that the observation of the base layer with a scanning electron microscope (element mapping by SEM-EDX measurement) can be performed on the portion of the base layer where the inorganic substance is present, and specifically, it is preferable to measure the surface or cross section of the portion of the base layer where the inorganic substance is present. For example, when the base layer is formed only with an inorganic particle-containing layer described below, it is preferable to observe its surface.

[0014] When SEM-EDX measurement is performed on the base material layer, the number of elongated regions per 50 μm × 50 μm observation field is preferably 2 or more, more preferably 3 or more, and even more preferably 10 or more. Furthermore, when SEM-EDX measurement is performed on the base material layer, the area of ​​inorganic-derived elements per 50 μm × 50 μm observation field is preferably 5% or more, preferably 10% or more, and more preferably 20% or more.

[0015] In addition, in the SEM observation of the base layer, it is preferable that the above-mentioned elongated regions are observed, and also that a plurality of branch shapes formed by inorganic particles are observed, as shown in Fig. 1b. The branch shapes are shapes in which inorganic particles other than the elongated regions are connected to the inorganic particles forming the elongated regions. In such cases, the amount of bleeding components from the surface of the base layer can be further reduced.

[0016] The method for obtaining a base layer having such elongated regions is not particularly limited, but examples thereof include a method using an inorganic particle-containing aqueous emulsion, which will be described later. This method allows a thin coating film containing a high concentration of inorganic matter to be formed on a foam, making it easier to obtain a base layer having the elongated regions.

[0017] <Inorganic Substance> The substrate layer contains an inorganic substance. In elemental analysis of the substrate layer, it is preferable that at least one element belonging to the third period is observed. Here, elements belonging to the third period include Na, Mg, Al, Si, P, S, Cl, and Ar. Among these, it is preferable that Al and Si are observed in the substrate layer. The inclusion of Al and Si in the substrate layer makes it easier to reduce the amount of bleeding components on the surface of the substrate layer through interactions between the resin and the inorganic substance, etc. The elemental analysis can be performed using SEM-EDX.

[0018] The inorganic material contained in the substrate layer is not particularly limited, but is preferably porous particles. Examples of porous particles include silica such as mesoporous silica, silica gel, and fumed silica; zeolites such as artificially synthesized zeolites and naturally occurring zeolites; activated carbon, Montlorillonite, hydrotalcite, diatomite, clinker ash, fly ash, aluminum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, titanium oxide, zirconium oxide, aluminum hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, zirconium hydroxide, zirconium phosphate, titanium phosphate, aluminum phosphate, calcium carbonate, metal-organic framework MOF, porous crystalline aluminum phosphate ALPO, and porous crystalline silicoaluminophosphate SAPO. These may be used alone or in combination of two or more. Also usable are layered particles of the above-listed compounds, core-shell particles synthesized using them as a template, hollow particles, aggregated particles, and fused alloys. These may be used alone or in combination of two or more. Among these, silica, zeolite, aluminum oxide, magnesium oxide, and calcium carbonate are preferred, silica, zeolite, and aluminum oxide are more preferred, and zeolite is even more preferred.

[0019] The inorganic substance is preferably in the form of particles, and the average particle size thereof is not particularly limited, but is preferably 0.01 to 100 μm, more preferably 0.1 to 80 μm, and even more preferably 0.5 to 20 μm. The average particle size of the inorganic substance means the cumulative median diameter measured using a particle size distribution diameter measuring instrument, SEM measurement, or the like.

[0020] <Resin> The substrate layer contains a resin in addition to the inorganic substance described above. More specifically, the substrate layer preferably includes at least an inorganic particle-containing layer containing a resin and an inorganic substance. The substrate layer preferably exhibits at least one endothermic peak in a temperature range of 50 to 200°C when measured using a differential scanning calorimeter (DSC). Combining a resin exhibiting such thermal properties with the inorganic substance described above facilitates reducing bleeding on the surface of the substrate layer. The resin is not particularly limited, but is preferably a thermoplastic resin. Examples of thermoplastic resins include thermoplastic elastomers such as olefin-based thermoplastic elastomers (TPO), styrene-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers; polyolefin-based resins such as polypropylene-based resins (PP), polyethylene-based resins (PE), and poly(1-)butene resins; acrylonitrile-butadiene-styrene (ABS) resins; polycarbonate resins; polyphenylene ether resins; (meth)acrylic resins; polyamide resins; and polyvinyl chloride resins (PVC).

[0021] Among these, the thermoplastic resin is preferably at least one selected from polyolefin resins and olefin thermoplastic elastomers (TPOs), more preferably polyolefin resins, and even more preferably polyethylene resins. By using these resins and the inorganic substances described above, bleeding on the surface of the substrate layer is easily reduced. Furthermore, when the foam layer described below is a polyolefin resin foam, the resin in the substrate layer is preferably a polyethylene resin. This improves the adhesion between the foam layer and the substrate layer.

[0022] As the olefin-based thermoplastic elastomer (TPO), any of blend type, dynamically crosslinked type, and polymerization type can be used. Specific examples of olefin-based thermoplastic elastomers include those containing polypropylene as a hard segment and a copolymer containing ethylene, propylene, and optionally a small amount of a diene component as a soft segment. Examples of such copolymers include ethylene-propylene copolymer (EPR) and ethylene-propylene-diene copolymer (EPDM). Other specific examples of olefin-based thermoplastic elastomers (TPO) include a blend of polyethylene and EPR, a blend of polyethylene and EPR partially crosslinked using an organic peroxide, a blend of polyethylene and EPR graft-modified with an unsaturated hydroxy monomer, an unsaturated carboxylic acid derivative, or the like, and butyl-grafted polyethylene.

[0023] The polyethylene resin is not particularly limited, but examples thereof include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ethylene-α-olefin copolymers containing ethylene as a main component, and these may be used alone or in combination of two or more.

[0024] <Layer Structure of Composite> The composite of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the contents of the drawings. As shown in FIG. 3, a composite 10 of the present invention includes a foam layer 11 and a substrate layer 12 laminated on one side of the foam layer 11. The substrate layer 12 is an inorganic particle-containing layer containing a resin and an inorganic substance. While FIG. 3 shows a diagram in which the substrate layer 12 is laminated on one side of the foam layer 11, the substrate layer 12 may be laminated on both sides of the foam layer 11. From the viewpoint of improving moldability and taking into consideration applications such as automotive interior materials, a composite in which the substrate layer 12 is laminated on one side of the foam layer 11, as shown in FIG. 3, is preferred.

[0025] Although the composite 10 in Fig. 3 shows an embodiment in which the foam layer is composed of only one layer, the foam layer may be composed of two or more layers. For example, the foam layer 11 may have a two-layer structure of a foam layer 11a and a foam layer 11b as shown in Fig. 4. The composite 10A in Fig. 4 is a composite in which the foam layer 11b, the foam layer 11a, and the base layer 12 are laminated in this order.

[0026] Although the composite 10 in FIG. 3 shows an embodiment in which the substrate layer 12 consists of only one layer, the substrate layer 12 may be multi-layered, i.e., two or more layers. For example, the substrate layer 12 may be a two-layer structure consisting of a first substrate layer 12b and a second substrate layer 12a, as shown in FIG. 5. The composite 10B in FIG. 5 is a composite in which a foam layer 11, a first substrate layer 12b, and a second substrate layer 12a are laminated in this order. When the substrate layer 12 is multi-layered, at least one layer of the multi-layer structure is an inorganic particle-containing layer containing a resin and an inorganic substance, and the other layers may or may not contain an inorganic substance. For example, in FIG. 5, the second substrate layer 12a may be a resin layer containing no inorganic substance, and the first substrate layer 12b may be an inorganic particle-containing layer containing a resin and an inorganic substance.

[0027] The content of the inorganic substance in the inorganic particle-containing layer is preferably 70 to 300 parts by mass, and more preferably 100 to 150 parts by mass, per 100 parts by mass of the resin.

[0028] The thickness of the inorganic particle-containing layer is not particularly limited, but is preferably 1 to 200 μm, more preferably 3 to 100 μm, even more preferably 5 to 50 μm, and still more preferably 5 to 20 μm.

[0029] The inorganic particle-containing layer is preferably a coating film, more specifically, a coating film formed from an inorganic particle-containing aqueous emulsion described below. When the inorganic particle-containing layer is a coating film, it is easy to form the elongated regions made of the inorganic substance.

[0030] As described above, the substrate layer may include a resin layer (second substrate layer) that does not contain inorganic particles. When the composite includes a resin layer that does not contain inorganic matter, the surface smoothness is more easily improved. The resin layer is a layer composed of a resin. The resin included in the resin layer can be any of the resins described above as the resin included in the substrate layer, without any particular restrictions. Among these, a polyethylene-based resin or an olefin-based thermoplastic elastomer (TPO) is preferred, and an olefin-based thermoplastic elastomer (TPO) is more preferred.

[0031] The thickness of the resin layer (second substrate layer) that does not contain inorganic particles is not particularly limited, but is preferably 100 to 1000 μm, and more preferably 300 to 700 μm.

[0032] The thickness of the substrate layer (total thickness of the substrate layer) is not particularly limited, but is, for example, 1 to 1000 μm, preferably 3 to 100 μm, more preferably 5 to 50 μm, and even more preferably 5 to 20 μm.

[0033] [Foam Layer] The composite of the present invention includes a foam layer. The foam layer can impart flexibility, lightness, and the like to the composite. The foam layer is not particularly limited, and examples thereof include polyolefin resin foam, polystyrene foam, polyurethane foam, phenolic resin foam, urea resin foam, epoxy resin foam, acrylic resin foam, rubber foam, polyvinyl chloride foam, polyamide resin foam, polyimide resin foam, polyvinyl alcohol resin foam, ionomer foam, pyranyl resin foam, and silicone resin foam. These foams can be used alone or in combination of two or more. Among these foams, polyolefin resin foam is preferred, and crosslinked polyolefin resin foam is more preferred.

[0034] The foam layer is formed by foaming a foamable resin composition containing a resin. When the foam layer is a crosslinked polyolefin resin foam, the foam layer is formed by crosslinking and foaming a foamable resin composition containing a polyolefin resin.

[0035] (Polyolefin Resin) Examples of the polyolefin resin contained in the foamable resin composition include polyethylene-based resins, polypropylene-based resins, ethylene vinyl acetate resins, etc. From the viewpoint of improving the heat resistance and moldability of the resulting crosslinked polyolefin resin foam, the polyolefin resin preferably contains a polypropylene-based resin, and more preferably contains both a polypropylene-based resin and a polyethylene-based resin.

[0036] Examples of polypropylene-based resins include homopolypropylene, ethylene-propylene random copolymers containing propylene as the main component, and ethylene-propylene block copolymers containing propylene as the main component. These may be used alone or in combination of two or more. Among these, it is preferable to use an ethylene-propylene random copolymer containing propylene as the main component. Incidentally, "containing propylene as the main component" means that the content of propylene-derived structural units in the polypropylene-based resin is 75% by mass or more, preferably 90% by mass or more, of the total monomer-derived structural units. The same applies below. The melt flow rate (hereinafter referred to as "MFR") of the polypropylene-based resin is preferably 70 g / 10 min or less, more preferably 50 g / 10 min or less, and even more preferably 25 g / 10 min or less. The lower limit of the MFR is typically 0.1 g / 10 min. The MFR of the polypropylene resin is a value measured in accordance with JIS K 7210 under conditions of a temperature of 230° C. and a load of 21.2 N.

[0037] The polyethylene resin is not particularly limited, but examples thereof include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ethylene-α-olefin copolymers containing ethylene as the main component, which may be used alone or in combination of two or more. Among the above-mentioned polyethylene resins, linear low-density polyethylene is preferred. The density of linear low-density polyethylene is 0.900 to 0.925 g / cm. ３ is preferably 0.902 to 0.922 g / cm ３The MFR of the polyethylene resin is preferably 0.5 to 70 g / 10 min, and more preferably 1.5 to 50 g / 10 min. The MFR of the polyethylene resin is a value measured in accordance with JIS K 7210 under conditions of a temperature of 190°C and a load of 21.2 N.

[0038] When the polyolefin resin contains a polypropylene-based resin, the foamable resin composition may further contain a resin other than a polypropylene-based resin. Specific examples include polyolefin-based resins other than polypropylene-based resins, such as polyethylene-based resins, and olefin-based elastomers. The total content of the polyolefin-based resin other than a polypropylene-based resin and the olefin-based elastomer relative to the total amount of resin contained in the foamable resin composition is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. Examples of olefin-based elastomers include ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), and olefin-based thermoplastic elastomers. Details of the olefin-based thermoplastic elastomer are as described above in the non-foam layer section. The foamable resin composition may also contain a resin other than a polyolefin resin and an olefin-based elastomer.

[0039] <Antioxidant> The foamable resin composition preferably contains an antioxidant. By containing an antioxidant, oxidative degradation of the polyolefin resin can be suppressed. The foamable resin composition preferably contains 0.1 to 5.0 parts by mass, and more preferably 0.5 to 4.0 parts by mass, of the antioxidant per 100 parts by mass of the resin. By using 0.5 parts by mass or more of the antioxidant per 100 parts by mass of the resin, oxidative degradation of the polyolefin resin can be further suppressed, and bleeding out of oxidative degradation products from the crosslinked polyolefin resin foam can be reduced. Furthermore, by using 5.0 parts by mass or less of the antioxidant per 100 parts by mass of the resin, bleeding out of excess antioxidant can be suppressed.

[0040] The type of antioxidant is not particularly limited, and examples thereof include phenolic antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and amine-based antioxidants. Among these, at least one selected from phenolic antioxidants and phosphorus-based antioxidants is preferred, and among these, phenolic antioxidants are more preferred from the viewpoints of antioxidant activity and compatibility with resins. Examples of phenolic antioxidants include 2,6-di-tert-butyl-p-cresol, n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, and tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane. Among these, 2,6-di-tert-butyl-p-cresol is preferred. The antioxidants may be used alone or in combination of two or more.

[0041] <Crosslinking Auxiliary Agent> The foamable resin composition preferably contains a crosslinking auxiliary agent. The content of the crosslinking auxiliary agent in the foamable resin composition is preferably 2.0 to 5.0 parts by mass, and more preferably 2.5 to 4.7 parts by mass, per 100 parts by mass of the resin contained in the foamable resin composition. By using 2.0 parts by mass or more of the crosslinking auxiliary agent per 100 parts by mass of the resin, heat resistance can be improved and oxidative degradation of the foam can be suppressed. By using 5.0 parts by mass or less of the crosslinking auxiliary agent per 100 parts by mass of the resin, moldability can be improved and poor foaming can be easily prevented.

[0042] Examples of cross-linking aids include polyfunctional (meth)acrylate compounds such as trifunctional (meth)acrylate compounds and bifunctional (meth)acrylate compounds, and compounds having three functional groups per molecule. Other cross-linking aids include compounds having two functional groups per molecule, such as divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, ethylvinylbenzene, lauryl methacrylate, and stearyl methacrylate. Examples of trifunctional (meth)acrylate compounds include trimethylolpropane trimethacrylate and trimethylolpropane triacrylate. Examples of bifunctional (meth)acrylate compounds include 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, and neopentyl glycol dimethacrylate. Examples of compounds having three functional groups in one molecule include trimellitic acid triallyl ester, 1,2,4-benzenetricarboxylic acid triallyl ester, and triallyl isocyanurate. The crosslinking aids can be used alone or in combination of two or more. Among these, polyfunctional (meth)acrylate compounds are preferred, bifunctional (meth)acrylate compounds are more preferred, and 1,9-nonanediol dimethacrylate is even more preferred.

[0043] <Foaming Agent> Methods for foaming a foamable resin composition include chemical foaming and physical foaming. The chemical foaming method is a method in which bubbles are formed by gas generated by thermal decomposition of a compound added to the foamable resin composition, while the physical foaming method is a method in which a low-boiling-point liquid (foaming agent) is impregnated into the foamable resin composition and then the foaming agent is volatilized to form cells. The foaming method is not particularly limited, but chemical foaming is preferred. As the foaming agent, a thermal decomposition type foaming agent is preferably used, and for example, an organic or inorganic chemical foaming agent with a decomposition temperature of about 140 to 270°C can be used. Examples of organic blowing agents include azo compounds such as ammonium carbonate, ammonium hydrogencarbonate, ammonium nitrite, azodicarbonamide, and azobisisobutyronitrile; nitroso compounds such as N,N'-dinitrosopentamethylenetetramine; hydrazine derivatives such as hydrazodicarbonamide, 4,4'-oxybis(benzenesulfonylhydrazide), and toluenesulfonylhydrazide; and semicarbazide compounds such as toluenesulfonylsemicarbazide.

[0044] Examples of inorganic foaming agents include sodium carbonate, sodium bicarbonate, metal azodicarboxylates (e.g., barium azodicarboxylate), sodium borohydride, and anhydrous monosodium citrate. Among these, from the viewpoints of obtaining fine bubbles and from the viewpoints of economy and safety, azo compounds and nitroso compounds are preferred, with azodicarbonamide, azobisisobutyronitrile, and N,N'-dinitrosopentamethylenetetramine being more preferred, and azodicarbonamide being particularly preferred. The foaming agents can be used alone or in combination of two or more. The amount of foaming agent added to the foamable resin composition is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 3 to 12 parts by mass per 100 parts by mass of the polyolefin resin, from the viewpoint of easily adjusting the expansion ratio of the foam to the range described below.

[0045] <Other Additives> The foamable resin composition may contain additives that are generally used in foams, such as a heat stabilizer, a colorant, a flame retardant, an antistatic agent, a filler, a rust inhibitor, and a decomposition temperature adjuster, as needed.

[0046] <Expansion Ratio> The expansion ratio of the foam layer is not particularly limited, but is preferably 8 to 30 times, more preferably 9 to 28 times, and even more preferably 9.5 to 27 times. When the expansion ratio is a certain level or higher, flexibility of the foam can be easily ensured. When the expansion ratio is a certain level or lower, the mechanical strength of the foam can be improved. The expansion ratio is calculated as the ratio of the specific volume (unit: cm) of the foamable resin composition before expansion to the foam layer after expansion. ３ / g) was measured and calculated by (specific volume of foam layer) / (specific volume of foamable resin composition before foaming).

[0047] <Degree of Crosslinking> The degree of crosslinking of the foam layer of the present invention is preferably 30 to 60% by mass. A degree of crosslinking of 30 to 60% by mass allows for a well-balanced improvement in the mechanical strength, flexibility, and moldability of the foam. From the viewpoint of a well-balanced improvement in the mechanical strength, flexibility, and moldability of the foam, the degree of crosslinking of the crosslinked polyolefin resin foam of the present invention is more preferably 33 to 57% by mass, and even more preferably 35 to 55% by mass. The degree of crosslinking can be measured by the following method. A test piece of about 100 mg is taken from the foam layer, and the mass A (mg) of the test piece is precisely weighed. Next, this test piece is immersed in 30 cm of xylene at 120°C. ３ After immersion for 24 hours, the insoluble matter on the mesh is filtered through a 200-mesh wire netting, vacuum-dried, and the mass B (mg) of the insoluble matter is precisely weighed. The degree of crosslinking (mass%) is calculated from the obtained value using the following formula: Degree of crosslinking (mass%) = 100 × (B / A).

[0048] <Thickness> The thickness of the foam layer is not particularly limited, but is preferably 1 to 5 mm, more preferably 1.2 to 4 mm, and even more preferably 1.5 to 3.5 mm.

[0049] [Method for producing composite] The method for producing the composite of the present invention is not particularly limited, but examples include a method comprising a step (A) of producing a foam layer and a step (B) of forming a base layer on at least one surface of the foam layer produced in the step (A).

[0050] <Step (A)> Step (A) is a step of producing a foam layer. Step (A) is preferably produced by a method including, for example, the following steps 1 to 3: (Step 1) a step of processing a foamable resin composition into a sheet to produce a foamable sheet; (Step 2) a step of irradiating the foamable sheet with ionizing radiation to produce a cross-linked foamable sheet; and (Step 3) a step of foaming the cross-linked foamable sheet to produce a foam layer.

[0051] (Step 1) Step 1 is a step of processing the foamable resin composition into a sheet to produce a foamable sheet. The foamable resin composition is kneaded using a kneader such as a Banbury mixer or a pressure kneader, and then continuously extruded using an extruder, a calender, conveyor belt casting, or the like to produce a foamable sheet. The temperature at which the foamable resin composition is kneaded is preferably 170 to 210°C, and more preferably 175 to 205°C.

[0052] (Step 2) Step 2 is a step of irradiating the foamable sheet with ionizing radiation to produce a crosslinked foamable sheet. When the foam layer is a crosslinked polyolefin resin foam, the irradiation dose when irradiating with ionizing radiation is preferably 1 to 10 Mrad, more preferably 1.5 to 5 Mrad. Irradiation with ionizing radiation may be performed on one side or both sides of the foamable sheet. Examples of ionizing radiation include electron beams, α-rays, β-rays, γ-rays, and X-rays. Of these, electron beams are preferred from the viewpoints of productivity and uniform irradiation.

[0053] (Step 3) Step 3 is a step of foaming the cross-linked foamable sheet to produce a sheet-like foam layer. Examples of methods for foaming the cross-linked foamable sheet include a batch method using an oven, and a continuous foaming method in which the cross-linked foamable sheet is continuously passed through a heating furnace. The temperature at which the cross-linked foamable sheet is foamed is approximately 150 to 320°C when the foam layer is a cross-linked polyolefin resin foam. The method for adjusting the temperature to the above range is not particularly limited, and may include the use of hot air or infrared rays. Furthermore, after foaming or during foaming, the cross-linked foamable sheet may be stretched in either or both of the MD and TD directions.

[0054] <Step (B)> Step (B) is a step of forming a substrate layer on at least one surface of the foam layer produced in step (A). A method of forming a substrate layer on at least one surface of the foam layer includes a method using an aqueous emulsion for forming an inorganic particle-containing layer in the substrate layer. For example, the substrate layer can be formed on at least one surface of the foam layer through the following steps 4 to 6. (Step 4) A step of preparing an aqueous emulsion. (Step 5) A step of dispersing inorganic particles in the aqueous emulsion to prepare an inorganic particle-containing aqueous emulsion. (Step 6) A step of applying the inorganic particle-containing aqueous emulsion to at least one surface of the foam layer and drying it to form an inorganic particle-containing layer.

[0055] (Step 4) Step 4 is a step of preparing an aqueous emulsion. The aqueous emulsion contains at least water and resin particles. The resin particles are of the same type as the resin contained in the inorganic particle-containing layer to be formed. That is, when the resin contained in the inorganic particle-containing layer is a polyethylene-based resin, the resin particles contained in the aqueous emulsion are polyethylene-based resin particles.

[0056] The aqueous emulsion is preferably obtained by emulsion polymerization of a monomer for producing resin particles. In the case where the resin particles are, for example, a polyethylene-based resin, the monomer for producing the resin particles is, for example, an ethylene monomer, and, optionally, an α-olefin monomer having approximately 3 to 10 carbon atoms. Specifically, the aqueous emulsion can be produced by adding a surfactant as an emulsifier, as well as the monomer and a pH adjuster, to a dispersion medium containing water as the main component (for example, a dispersion medium containing 90% by mass or more of water, preferably a dispersion medium consisting of water), and emulsion-polymerizing the monomer while stirring. In emulsion polymerization, additives such as a polymerization initiator, a chain transfer agent, and a stabilizer may be blended as necessary.

[0057] (Step 5) In step 5, inorganic particles are dispersed in the aqueous emulsion prepared as described above to form an inorganic particle-containing aqueous emulsion. The inorganic particles dispersed in the aqueous emulsion are of the same type as the inorganic material contained in the inorganic particle-containing layer to be formed. The amount of inorganic particles per 100 parts by mass of resin particles in the inorganic particle-containing aqueous emulsion is the same as the amount of inorganic material per 100 parts by mass of resin in the inorganic particle-containing layer described above.

[0058] (Step 6) In step 6, the inorganic particle-containing aqueous emulsion obtained as described above is applied to at least one surface of the foam layer and dried to form an inorganic particle-containing layer. The method for applying the inorganic particle-containing aqueous emulsion is not particularly limited, and various coaters may be used. For example, application can be performed using a bar coater, comma coater, gravure coater, dip coater, roll coater, spin coater, flow coater, knife coater, spray coater, or the like. The temperature during drying is, for example, 30 to 150°C, and preferably 60 to 120°C.

[0059] By carrying out the above steps 4 to 6, a composite body consisting of a foam layer and a substrate layer laminated on at least one surface of the foam layer is obtained. In this case, the substrate layer is composed of a single layer of inorganic particle-containing layer, which is a coating film of an inorganic particle-containing aqueous emulsion. By using an inorganic particle-containing aqueous emulsion, it becomes easier to obtain a substrate layer in which the above-mentioned elongated regions in which a plurality of inorganic particles are connected in a string-like pattern are observed. The method using an inorganic particle-containing aqueous emulsion is also preferable in that the VOC (volatile organic compounds) of the obtained composite is reduced.

[0060] In the above steps 4 to 6, the method for forming the inorganic particle-containing layer is described by describing a "step of preparing an aqueous emulsion" and a "step of preparing an inorganic particle-containing aqueous emulsion." However, commercially available products can be used as the "aqueous emulsion" and the "inorganic particle-containing aqueous emulsion" as needed.

[0061] When the base layer is made multilayered, for example, a resin layer (such as a resin film) that does not contain inorganic particles may be laminated on the surface of the inorganic particle-containing layer formed on at least one surface of the foam layer as described above.

[0062] The lamination method and process are not particularly limited, but may be a method of applying heat and pressure using a press or the like to thermocompress the laminate, or a method using an adhesive or pressure sensitive adhesive.

[0063] <Uses> The composite of the present invention can be molded by various molding methods such as vacuum molding and used as a heat insulating material, cushioning material, etc. In particular, in the automotive field, the composite of the present invention can be suitably used as an automotive interior material such as a ceiling material, a door, or an instrument panel.

[0064] The present invention will be explained in more detail by way of examples, but the present invention is not limited to these examples in any way.

[0065] [Measurement Methods] The methods for measuring and evaluating each physical property are as follows.

[0066] <Analysis of inorganic distribution and elemental species in the substrate layer> The surface of the substrate layer of the composite was measured using a SEM-EDX device (JEOL Ltd., "JSM-IT100") to measure the distribution of inorganic substances and the type of elements in the substrate layer. The measurement conditions for SEM-EDX were as follows: Observation magnification: 2000x; Field of view: 190 μm × 86 μm; Observation field of view: 50 μm × 50 μm; Acceleration voltage: 10 kV; WD: 10 mm. The above field of view corresponds to the size of the SEM photograph obtained, and the observation field corresponds to the field of view in which the distribution of inorganic substances is observed. Note that devices other than the above-mentioned SEM-EDX device may be used as long as measurements can be made under the above-mentioned observation magnification to WD conditions. The morphology of the inorganic substances was confirmed by mapping elements according to the type of inorganic substance using SEM-EDX. The RGB values ​​of the images obtained by SEM-EDX were reset and processed as follows: R: 0 / 190 G: 0 / 255 B: 0 / 255 By processing based on the above setting values, areas other than those where elements were strongly detected were hidden. Then, it was confirmed whether elongated areas (elongated areas) in which multiple inorganic particles were connected in a string-like pattern were observed in the base material layer.

[0067] <Form of inorganic substance> The inorganic substance contained in the base material layer was used as a measurement sample, and the presence or absence of pores and the pore diameter were measured by measuring the nitrogen adsorption / desorption isotherm using a "BELSORP-mini" manufactured by Bell Japan.

[0068] <Presence or Absence of Endothermic Peak> Using a differential scanning calorimeter (DSC, Yamato Scientific Co., Ltd., "DSC7020") as a sample, the substrate layer was heated from 25 to 250°C at a rate of 10°C / min under a nitrogen flow condition of 40 mL / min, and the presence or absence of an endothermic peak in the temperature range of 50 to 200°C was examined.

[0069] <Expansion Ratio and Crosslinking Degree of Foam Layer> The expansion ratio and crosslinking degree of the foam layer were measured by the methods described in the specification.

[0070] <Presence or absence of bleeding matter on the surface of the base layer> The composites produced in each of the examples and comparative examples were visually evaluated for the presence or absence of bleeding matter (presence or absence of bleed-out) on the surface of the base layer after heating at 80°C, 100°C, and 120°C for 24 hours. A judgment of "yes" or "no" was made based on the following evaluation items. Yes...visual: gloss, discoloration, and stickiness were observed. No...visual: gloss, discoloration, and stickiness were not observed.

[0071] [Components Used] The components used in each Example and Comparative Example are as follows. (Raw Materials for Foam Layer) Polypropylene Resin (1): Homo PP, manufactured by Prime Polymer Co., Ltd., trade name "J106G", MFR 15 g / 10 min Polypropylene Resin (2): Random PP, manufactured by Sumitomo Chemical Co., Ltd., trade name "AD571", density 0.90 g / cm ３ , MFR 0.5 g / 10 min (230 ° C.) LLDPE: Linear low-density polyethylene, manufactured by Prime Polymer Co., Ltd., trade name "UltraZex 1020L", density 0.91 g / cm ３ , MFR 2.0 g / 10 min (190°C) TPO: olefin-based thermoplastic elastomer, manufactured by Basell, trade name "Softell CA 02 A", MFR 0.6 g / 10 min (230°C) EPDM: olefin-based elastomer, manufactured by Mitsui Chemicals, Inc., trade name "3045" Foaming agent: azodicarbonamide, manufactured by Otsuka Chemical Co., Ltd., trade name "SO-L", decomposition temperature: 197°C, average particle size: 3.2 μm Phenol-based antioxidant: manufactured by BASF Japan Ltd., trade name "Irganox 1010" Crosslinking aid: 1,9-nonanediol dimethacrylate, manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Ester 1,9ND", viscosity 8 mPa·s / 25°C

[0072] (Raw materials for the base layer) Inorganic particle-containing aqueous emulsion (1)...a water-based emulsion in which polyethylene resin particles are dispersed, and silica (SiO ２ ) was dispersed to prepare an inorganic particle-containing aqueous emulsion (1). The ratio of silica (SiO ２ The amount of silica (SiO ２ ) has an average particle size of 9 μm.

[0073] Inorganic particle-containing aqueous emulsion (2): Magnesium oxide (MgO) was dispersed in an aqueous emulsion in which polyethylene resin particles were dispersed to prepare an inorganic particle-containing aqueous emulsion (2). The amount of magnesium oxide (MgO) per 100 parts by mass of polyethylene resin particles in the inorganic particle-containing aqueous emulsion (2) was 80 parts by mass. The average particle size of the magnesium oxide (MgO) used was 5 μm.

[0074] Inorganic particle-containing aqueous emulsion (3) ... A water-based emulsion in which polyethylene resin particles are dispersed, and aluminum oxide (Al ２ O ３ ) was dispersed to prepare an inorganic particle-containing aqueous emulsion (3). ２ O ３ The amount of aluminum oxide (Al) used was 110 parts by mass. ２ O ３ ) has an average particle size of 7.2 μm.

[0075] Inorganic particle-containing aqueous emulsion (4) ... A water-based emulsion in which polyethylene resin particles are dispersed, and calcium carbonate (CaCO ３ ) was dispersed to prepare an inorganic particle-containing aqueous emulsion (4). ３ The amount of calcium carbonate (CaCO ) used was 100 parts by mass. ３ ) has an average particle size of 9 μm.

[0076] Inorganic particle-containing aqueous emulsion (5): Zeolite was dispersed in an aqueous emulsion in which polyethylene resin particles were dispersed, to prepare an inorganic particle-containing aqueous emulsion (5). The amount of zeolite per 100 parts by mass of polyethylene resin particles in the inorganic particle-containing aqueous emulsion (5) was 120 parts by mass. The average particle size of the zeolite used was 7 μm.

[0077] Inorganic particle-containing aqueous emulsion (6) ... A water-based emulsion in which polyethylene resin particles are dispersed, and aluminum oxide (Al ２ O ３ ) was dispersed to prepare an inorganic particle-containing aqueous emulsion (6). ２ O ３ The amount of aluminum oxide (Al) used was 10 parts by mass. ２ O ３ ) has an average particle size of 7.2 μm.

[0078] Inorganic particle-containing aqueous emulsion (7): Zeolite was dispersed in an aqueous emulsion in which polyethylene resin particles were dispersed, to prepare an inorganic particle-containing aqueous emulsion (7). The amount of zeolite per 100 parts by mass of polyethylene resin particles in the inorganic particle-containing aqueous emulsion (7) was 10 parts by mass. The average particle size of the zeolite used was 7 μm.

[0079] Example 1 (Production of Foam Layer) A foamable resin composition obtained by mixing polypropylene-based resin (2), LLDPE, phenol-based antioxidant, crosslinking aid, and foaming agent in the proportions shown in Table 1 was melt-kneaded at 180°C using a single-screw extruder to form a foamable sheet. Both sides of the foamable sheet were irradiated with ionizing radiation (electron beam) at an acceleration voltage of 1000 kV and 2.0 Mrad to obtain a crosslinked foamable sheet. The crosslinked foamable sheet was then fed into a vertical hot-air foaming oven at an oven temperature of 250°C and heated and foamed while stretching to obtain a crosslinked polyolefin resin foam having a thickness of 2.5 mm. (Production of Composite) One side of the crosslinked polyolefin resin foam prepared as described above was coated with inorganic particle-containing aqueous emulsion (1) using a roll coater, followed by drying at 100°C to form a substrate layer comprising an inorganic particle-containing layer. The thickness of the substrate layer comprising an inorganic particle-containing layer was 10 μm. In this manner, a composite of crosslinked polyolefin resin foam / inorganic particle-containing layer (substrate layer) was obtained.

[0080] [Examples 2 to 7] Crosslinked polyolefin resin foams were obtained in the same manner as in Example 1, except that the formulation of the foamable resin composition was changed as shown in Table 1. Then, composites were obtained in the same manner as in Example 1, using the following types of inorganic particle-containing aqueous emulsions. In Example 2, inorganic particle-containing aqueous emulsion (2), in Example 3, inorganic particle-containing aqueous emulsion (3), in Example 4, inorganic particle-containing aqueous emulsion (4), and in Examples 5 to 7, inorganic particle-containing aqueous emulsion (5) were used.

[0081] Comparative Example 1 A crosslinked polyolefin resin foam was obtained in the same manner as in Example 1. Then, the types of inorganic particle-containing aqueous emulsions were changed as follows, and a composite was obtained in the same manner as in Example 1. In Comparative Example 1, inorganic particle-containing aqueous emulsion (6) was used.

[0082] Comparative Example 2 A crosslinked polyolefin resin foam was obtained in the same manner as in Example 1. Next, an aqueous emulsion (containing no inorganic substances) was applied to the crosslinked polyolefin foam using a roll coater, and other treatments were carried out in the same manner as in Example 1 to obtain a composite.

[0083] Comparative Example 3 A crosslinked polyolefin resin foam was obtained in the same manner as in Example 5. Then, a composite was obtained in the same manner as in Example 5, except that the types of inorganic particle-containing aqueous emulsions were changed as follows: In Comparative Example 3, inorganic particle-containing aqueous emulsion (7) was used.

[0084]

[0085] The composites of Examples 1 to 7 were composites including a foam layer and a substrate layer containing an inorganic material. When the substrate layer was observed with a scanning electron microscope, elongated regions in which a plurality of inorganic particles were connected in a string-like pattern were observed, and no bleeding from the surface of the substrate layer was confirmed. In contrast, the composites of Comparative Examples 1 and 3 contained an inorganic material in the substrate layer, but when the substrate layer was observed with a scanning electron microscope, no elongated regions were confirmed. Furthermore, the composite of Comparative Example 2 did not contain an inorganic material in the substrate layer. The composites of Comparative Examples 1 to 3 did not satisfy the specified requirements of the present invention, and as a result, bleeding from the surface of the substrate layer was confirmed.

[0086] 10, 10A, 10B Composite 11, 11a, 11b Foam layer 12 Base material layer 12a Second base material layer 12b First base material layer

Claims

1. A composite comprising a foam layer and a base layer formed on at least one surface of the foam layer, the base layer containing an inorganic material, and when the base layer is observed with a scanning electron microscope, elongated regions in which a plurality of inorganic particles are linked together in a string-like pattern are observed.

2. The composite according to claim 1, wherein a plurality of branch shapes formed by inorganic particles are observed when the base layer is observed under a scanning electron microscope.

3. The composite according to claim 1 or 2, wherein at least one element belonging to the third period is observed in an elemental analysis of the substrate layer.

4. The composite according to claim 1 or 2, in which Al and Si are observed by elemental analysis.

5. The composite according to claim 1 or 2, wherein the substrate layer contains a resin.

6. The composite according to claim 1 or 2, wherein the base layer exhibits at least one endothermic peak in a temperature range of 50 to 200° C. when measured by a differential scanning calorimeter (DSC).