JP2019177664A - Composite foam sheet and molded body - Google Patents

Abstract

To provide a composite foam sheet capable of suppressing occurrence of a gate mark caused by injection molding and comprising flexibility, and a molded body using the same.SOLUTION: A composite foam sheet 1 of the invention comprises: a thermoplastic resin foam sheet 10; a first unfoamed resin sheet 20 formed on one surface 12 of the thermoplastic resin foam sheet 10; and a second unfoamed resin sheet 30 formed on an opposite surface 24 of the surface 22 on the thermoplastic resin foam sheet 10 side on the first unfoamed resin sheet 20. A melting point of the first unfoamed resin sheet 20 is equal to or smaller than a melting point of the thermoplastic resin foam sheet 10, and a melting point of the second unfoamed resin sheet 30 is 160°C or greater. A molded article of the invention is obtained by molding the composite foam sheet of the invention.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite foam sheet used for automobile interior materials and the like, and a molded body using the same.

Resin foams are used in vehicles for the purpose of reducing vehicle weight. In recent years, further weight reduction of vehicles has been desired, and efforts have been made to further reduce the weight of resin foams used in vehicles. In particular, when a resin foam is used as a vehicle interior material, flexibility is required in addition to lightweight. In order to improve the flexibility of the resin foam, it is necessary to increase the expansion ratio of the resin foam.
On the other hand, in recent years, with the diversification and sophistication of preferences, automobile interior materials have been required to have complicated shapes, and in addition, productivity improvement has been demanded. Therefore, it has been attempted to manufacture automobile interior materials by a low pressure injection molding method. In the low pressure injection molding method, a resin is injected from an injection molding machine through a runner and a gate into a cavity of a mold as a product at a low pressure. For example, a molten resin such as a polypropylene resin that becomes an aggregate is injection-molded on one surface of the resin foam.

However, when a molten resin is injection-molded on one surface of a resin foam having a high expansion ratio, the resin foam may melt in the vicinity of the gate for injecting the molten resin. When the melted portion of the resin foam is solidified, volume shrinkage occurs. Therefore, for example, as shown in FIG. 3, a recess 160 called a gate mark is generated at a position corresponding to the gate 600 of the surface 140 opposite to the surface 120 on which the resin 500 is injection-molded in the resin foam 100. There is a case. This dent has a problem that the dent mark is made even on the skin material coated on the surface of the resin foam, and the appearance is deteriorated.
In order to suppress the generation of gate marks, know-how has been studied to adjust the shape of the gate, the temperature and speed of the injected resin, etc. However, as a more fundamental solution, improvement of the resin material is required. It has been.

For example, Patent Document 1 discloses that 25 to 50 weights of thermoplastic elastomer with respect to 100 parts by weight of a polyolefin resin composition composed of a polypropylene resin having at least one DSC endothermic peak of 160 ° C. or higher and a polyethylene resin. A crosslinked polyolefin resin foam containing a part is disclosed. This crosslinked polyolefin resin foam has an apparent density of 50 to 100 kg / m ³ and a gel fraction of 45% or more.

JP 2008-266589 A

However, even the crosslinked polyolefin resin foam of Patent Document 1 is insufficient in suppressing the generation of gate marks by injection molding, and the problem of poor appearance has not been completely solved.
Therefore, the present invention has been made in view of the above circumstances, and provides a composite foam sheet that has flexibility and can suppress the generation of gate marks due to injection molding, and a molded body using the same. The task is to do.

  As a result of intensive investigations, the inventors preliminarily laminate the first unfoamed resin sheet and the second unfoamed resin sheet, each having a melting point satisfying a predetermined condition, on one surface of the thermoplastic resin foam sheet. Thus, the present inventors have found that a composite foam sheet having flexibility and suppressing generation of gate marks due to injection molding, and a molded body using the same can be obtained.

That is, the present invention provides the following [1] to [8].
[1] A thermoplastic resin foam sheet, a first unfoamed resin sheet provided on one surface of the thermoplastic resin foam sheet, and the thermoplastic resin foam sheet side of the first unfoamed resin sheet A second unfoamed resin sheet provided on a surface opposite to the surface, the melting point of the first unfoamed resin sheet is a temperature equal to or lower than the melting point of the thermoplastic resin foam sheet, and the second A composite foamed sheet, wherein the unfoamed resin sheet has a melting point of 160 ° C or higher.
[2] The resin constituting the second unfoamed resin sheet is at least one resin selected from the group consisting of polyamide resin, polybutylene terephthalate resin, and polyethylene terephthalate resin. Composite foam sheet.
[3] A resin constituting the third non-foamed resin sheet is provided with a third non-foamed resin sheet on a surface opposite to the surface of the second foamed resin sheet on the thermoplastic resin foam sheet side. The composite foam sheet according to [1] or [2], which is a polyolefin resin.
[4] The composite foam sheet according to [3] above, wherein the resin constituting the third unfoamed resin sheet is a polypropylene resin.
[5] The composite foam sheet according to any one of the above [1] to [4], wherein the total thickness of the first unfoamed resin sheet and the second unfoamed resin sheet is 10 to 100 μm. .
[6] The composite foam sheet according to any one of [1] to [5], wherein the thermoplastic resin foam sheet is a polyolefin resin foam sheet.
[7] A molded product obtained by molding the composite foam sheet according to any one of [1] to [6].
[8] The molded article according to [7], which is an automobile interior material.

  According to the present invention, it is possible to provide a composite foam sheet that has flexibility and can suppress generation of gate marks due to injection molding, and a molded body using the same.

FIG. 1 is a view showing an example of the composite foam sheet of the present invention. FIG. 2 is a view showing another example of the composite foam sheet of the present invention. FIG. 3 is a diagram for explaining a gate mark of a resin foam.

The composite foam sheet of the present invention includes a thermoplastic resin foam sheet, a first unfoamed resin sheet provided on one surface of the thermoplastic resin foam sheet, and a plastic resin foam sheet side of the first unfoamed resin sheet. And a second unfoamed resin sheet provided on the surface opposite to the surface. For example, a composite foam sheet 1 as an example of the composite foam sheet according to the present invention includes a thermoplastic resin foam sheet 10 and a first uncoated sheet provided on one surface 12 of the thermoplastic resin foam sheet 10 as shown in FIG. A foamed resin sheet 20 and a second unfoamed resin sheet 30 provided on the surface 24 opposite to the surface 22 on the thermoplastic resin foamed sheet 10 side of the first unfoamed resin sheet 20 are provided.
The melting point of the first unfoamed resin sheet is equal to or lower than the melting point of the thermoplastic resin foam sheet, and the melting point of the second unfoamed resin sheet is 160 ° C. or higher. Hereinafter, the thermoplastic resin foam sheet may be simply referred to as “foam sheet”, and the non-foam resin sheet may be simply referred to as “resin sheet”.
Hereinafter, each component used for the composite foam sheet of this invention is demonstrated.

[Thermoplastic resin foam sheet]
Examples of the thermoplastic resin foam sheet include a sheet formed by crosslinking and foaming a resin composition containing a thermoplastic resin.
Examples of the thermoplastic resin used for the thermoplastic resin foam sheet include polypropylene resins, polyethylene resins, polyolefin resins such as olefin thermoplastic elastomers, polystyrene resins, acrylonitrile / ethylene propylene / styrene copolymers (AES). Resin) and the like. These thermoplastic resins can be used alone or in combination of two or more. A preferred thermoplastic resin from the viewpoint of lightness and flexibility is a polyolefin resin, a more preferred thermoplastic resin is at least one of a polypropylene resin and a polyethylene resin, and a more preferred thermoplastic resin is a polypropylene resin. And a mixture of polyethylene resin.

<Polypropylene resin>
The polypropylene resin is not particularly limited, and examples thereof include a propylene homopolymer (homopolypropylene) and a copolymer of propylene and another olefin. The copolymer of propylene and another olefin may be any of a block copolymer, a random copolymer, and a random block copolymer, but is preferably a random copolymer (random polypropylene).
Examples of other olefins copolymerized with propylene include α such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene and the like. -Olefins, among which ethylene is preferred. That is, the polypropylene resin is preferably an ethylene-propylene random copolymer.
The copolymer of propylene and other olefins is usually 90 to 99.5% by weight of propylene and 0.5 to 10% by weight of α-olefin other than propylene, but 95 to 99% by weight of propylene. %, And α-olefin other than propylene is preferably 1 to 5% by mass.

The polypropylene resin preferably has a melt flow rate (hereinafter also referred to as “MFR”) of 0.4 to 14.0 g / 10 min, more preferably 0.5 to 12.5 g / 10 min. preferable. By using the polypropylene resin having the above MFR, it becomes easy to improve the moldability when the resin composition is processed into a foam and the moldability when the foam is secondarily molded.
The melting point of the polypropylene resin is, for example, 155 to 165 ° C. in the case of a homopolymer and a block copolymer, and 130 to 150 ° C. in the case of a random copolymer.
Said polypropylene resin can be used individually or in combination of 2 or more types.

<Polyethylene resin>
Examples of the polyethylene resin include a low density polyethylene resin, a medium density polyethylene resin, a high density polyethylene resin, and a linear low density polyethylene resin. The polyethylene resin preferably has an MFR of 1.0 to 5.0 g / 10 min, and more preferably 1.5 to 4.0 g / 10 min. By using the polyethylene resin having the above MFR, it becomes easy to improve the moldability when the resin composition is processed into a foam and the moldability when the foam is secondarily molded.

Of the polyethylene resins, linear low density polyethylene resins (LLDPE) are more preferable. LLDPE is polyethylene having a density of 0.910 g / cm ³ or more and less than 0.950 g / cm ³ , and preferably has a density of 0.910 to 0.930 g / cm ³ . When the resin composition contains LLDPE having a low density, the processability when processing into a foamed sheet, the moldability when forming the foamed sheet into a molded body, and the like are likely to be good. In addition, the said density was measured based on JISK7112.
LLDPE is usually a copolymer of ethylene and a small amount of an α-olefin containing ethylene as a main component (50% by mass or more, preferably 70% by mass or more of all monomers). Here, examples of the α-olefin include those having 3 to 12 carbon atoms, preferably 4 to 10 carbon atoms, and specifically, 1-butene, 1-pentene, 1-hexene, 4-methyl-1 -Pentene, 1-heptene, 1-octene and the like. In the copolymer, these α-olefins can be used alone or in combination of two or more.
Moreover, a polyethylene-type resin can also be used individually or in combination of 2 or more types.
The melting point of the polyethylene resin is, for example, 105 to 110 ° C. in the case of a low density polyethylene resin, 120 to 123 ° C. in the case of a medium density polyethylene resin, and 123 in the case of a high density polyethylene resin. It is -135 degreeC, and is 110-130 degreeC in the case of a linear low density polyethylene-type resin.

<Olefin-based thermoplastic elastomer>
The olefin-based thermoplastic elastomer (TPO) generally has a polyolefin such as polyethylene or polypropylene as a hard segment and a rubber component such as EPM or EPDM as a soft segment. As the olefinic thermoplastic elastomer, any of a blend type, a dynamic crosslinking type, and a polymerization type can be used.

When the resin composition contains a polyolefin resin, it may be composed of a polyolefin resin alone as a resin component, but contains a resin component other than the polyolefin resin as long as the object of the present invention is not impaired. Also good.
The polyolefin resin is usually contained in an amount of 70% by mass or more with respect to the total amount of the resin contained in the resin composition, but is preferably contained in an amount of 80 to 100% by mass, more preferably 90 to 100% by mass.

Further, the resin composition preferably contains 40% by mass or more, more preferably 50% by mass or more, and 90% by mass of the polypropylene resin based on the total amount of the resin contained in the resin composition. It is preferable to contain below, and it is more preferable to contain 80 mass% or less.
As described above, the polypropylene resin is preferably random polypropylene, but may be a mixture of homopolypropylene and random polypropylene.
Thus, a foamed sheet can make the mechanical strength, heat resistance, etc. of a foamed sheet favorable by having a polypropylene resin as a main component.

The resin composition preferably contains a polyethylene resin in addition to the polypropylene resin as a polyolefin resin. In this case, the polyethylene resin is preferably contained in an amount of 10% by mass or more, more preferably 20% by mass or more, and 60% by mass or less, based on the total amount of the resin contained in the resin composition. The content is preferably 50% by mass or less.
By including a polyethylene resin in addition to the polypropylene resin, the resin composition can easily improve processability and moldability while improving mechanical strength, heat resistance, and the like.
The resin composition may further contain an olefin-based thermoplastic elastomer in addition to the polypropylene resin. In this case, from the viewpoint of mechanical strength, heat resistance, processability and moldability of the foam sheet, the olefinic thermoplastic elastomer may be contained in an amount of 30% by mass or less based on the total amount of the resin contained in the resin composition. The content is preferably 20% by mass or less, more preferably 10% by mass or more.

<Additives>
The resin composition used for this invention contains a foaming agent normally as an additive other than said resin component. Moreover, it is preferable to contain one or both of a crosslinking assistant and an antioxidant.

(Foaming agent)
Methods for foaming the 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 resin composition, and the physical foaming method is impregnated with a low boiling point liquid (foaming agent) in the resin composition. Thereafter, the cell is formed by volatilizing the foaming agent. The foaming method is not particularly limited, but the chemical foaming method is preferable from the viewpoint of obtaining a uniform closed cell foam.
As the foaming agent, a thermal decomposition type foaming agent is used. For example, an organic or inorganic chemical foaming agent having a decomposition temperature of about 160 to 270 ° C. can be used.
Organic foaming agents include azodicarbonamide, azodicarboxylic acid metal salts (such as barium azodicarboxylate), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N, N′-dinitrosopentamethylenetetramine, Examples thereof include hydrazine derivatives such as hydrazodicarbonamide, 4,4′-oxybis (benzenesulfonylhydrazide) and toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonyl semicarbazide.

Examples of the inorganic foaming agent include ammonium carbonate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, anhydrous monosodium citrate, and the like.
Among these, azo compounds and nitroso compounds are preferable from the viewpoint of obtaining fine bubbles, and from the viewpoints of economy and safety, and azodicarbonamide, azobisisobutyronitrile, N, N′-dinitrosopentamethylene. Tetramine is more preferred, and azodicarbonamide is particularly preferred.
A foaming agent can be used individually or in combination of 2 or more types.
The addition amount of the pyrolytic foaming agent is preferably 1 to 30 parts by mass, more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the resin component, from the viewpoint of appropriately foaming the foam without bursting. .

(Crosslinking aid)
A polyfunctional monomer can be used as a crosslinking aid. For example, trifunctional (meth) acrylate compounds such as trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, trimellitic acid triallyl ester, 1,2,4-benzenetricarboxylic acid triallyl ester, triallyl isocyanurate, etc. Bifunctional compounds such as compounds having three functional groups in one molecule, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, neopentylglycol dimethacrylate, etc. (Meth) acrylate compounds, compounds with two functional groups in one molecule such as divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, ethyl vinyl benzene, lauryl methacrylate, stearyl methacrylate Over doors and the like. In these, a trifunctional (meth) acrylate type compound is more preferable.
The crosslinking aids can be used alone or in combination of two or more.
By adding a crosslinking aid to the resin composition, the resin composition can be crosslinked with a small ionizing radiation dose. Therefore, cutting and deterioration of each resin molecule accompanying irradiation with ionizing radiation can be prevented.
The content of the crosslinking aid is preferably 0.2 to 20 parts by mass with respect to 100 parts by mass of the resin composition from the viewpoint of adjusting the degree of crosslinking and ease of control when foaming the resin composition. More preferred is 5 to 15 parts by mass.

(Antioxidant)
Examples of the antioxidant include phenol-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and amine-based antioxidants. In these, a phenolic antioxidant and a sulfur type antioxidant are preferable, and it is more preferable to use a phenolic antioxidant and a sulfur type antioxidant together.
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, tetrakis [methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate ] Methane etc. are mentioned.
Examples of the sulfur-based antioxidant include dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, pentaerythrityl tetrakis (3-lauryl thiopropionate), and the like.
These antioxidants can be used alone or in combination of two or more.
0.1-10 mass parts is preferable with respect to 100 mass parts of resin compositions, and, as for content of antioxidant, 0.2-5 mass parts is more preferable.
In addition, the resin composition can be used in addition to the above, such as decomposition temperature adjusting agents such as zinc oxide, zinc stearate, urea, etc., flame retardants, metal damage inhibitors, antistatic agents, stabilizers, fillers, pigments, etc. The additive may be contained.

[Foamed sheet]
The foam sheet used in the present invention is obtained by crosslinking and foaming the above resin composition.
(density)
The density (apparent density) of the foamed sheet is preferably 0.125 g / cm ³ or less, more preferably 0.083 g / cm ³ or less, and still more preferably 0, from the viewpoint of improving the balance between flexibility and mechanical strength. .067g / cm ³ or less, and, preferably 0.029 g / cm ³ or more, more preferably 0.040 g / cm ³ or more, further preferably 0.043 g / cm ³ or more.

(Crosslinking degree)
The degree of crosslinking (% by mass) of the foamed sheet is preferably 25% or more, more preferably 30% or more, still more preferably 35% or more, from the viewpoint of improving flexibility, mechanical strength, and moldability in a balanced manner. And preferably it is 65% or less, More preferably, it is 60% or less, More preferably, it is 55% or less.
In addition, the measuring method of a crosslinking degree can be measured by the method as described in the Example mentioned later.

(Thickness)
The thickness of the foam sheet is preferably 0.5 mm or more, more preferably 0.8 mm or more, further preferably 1.2 mm or more, and preferably 8 mm or less, more preferably 6 mm or less, and even more preferably 5 mm or less. is there. When the thickness of the foam is within these ranges, it is easy to improve both flexibility and moldability, and it becomes easy to mold the automobile interior material.

<Method for producing foam sheet>
The foamed sheet can be produced, for example, by melting and kneading the resin composition to form a sheet, cross-linking the resin composition by irradiating ionizing radiation, and further heating and foaming.
Specifically, a production method having the following steps 1 to 3 is more preferable.
Step 1: Step of obtaining a resin composition having a predetermined shape such as a sheet after melt-kneading each component constituting the resin composition Step 2: Irradiating the resin composition obtained in Step 1 with ionizing radiation Step of cross-linking Step 3: Step of obtaining a foamed sheet by heating and foaming the resin composition cross-linked in step 2 to a temperature higher than the decomposition temperature of the pyrolytic foaming agent.

In step 1, first, each component constituting the resin composition is supplied to a kneading apparatus, and melt-kneaded at a temperature lower than the decomposition temperature of the pyrolytic foaming agent, and then the melt-kneaded resin composition is preferably Is formed into a desired shape such as a sheet by a kneading apparatus used in melt kneading.
Examples of the kneading apparatus used here include general-purpose kneading apparatuses such as injection molding machines, extruders (single screw extruders, twin screw extruders, etc.), Banbury mixers, rolls, and the like. An extruder is preferred, and if an injection molding machine is used, it can be manufactured with high productivity.
The resin temperature inside the injection molding machine or the extruder is preferably 120 to 220 ° C, more preferably 140 to 200 ° C, still more preferably 150 to 195 ° C.

In step 2, the resin composition molded into a desired shape is irradiated with ionizing radiation.
Examples of ionizing radiation include electron beams, α rays, β rays, γ rays, X rays, and the like. In these, an electron beam is preferable from a viewpoint of performing productivity and irradiation uniformly.
For example, when the resin composition is formed into a sheet shape, the ionizing radiation may be irradiated on only one side of the sheet or on both sides, but preferably on both sides.
The irradiation amount of ionizing radiation may be an amount capable of obtaining a desired degree of crosslinking in consideration of the thickness of the foamable resin composition to be irradiated, etc., but is usually 0.1 to 10 Mrad, preferably 2 to 5 Mrad is more preferable.

In Step 3, after the resin composition is cross-linked by irradiation with ionizing radiation as described above, the resin composition is heated to a temperature equal to or higher than the decomposition temperature of the foaming agent, and foaming and molding are performed simultaneously. Obtainable.
Here, the temperature at which the resin composition is heated and foamed depends on the decomposition temperature of the thermally decomposable foaming agent used as the foaming agent, but is usually 140 to 300 ° C, preferably 150 to 280 ° C, more preferably 160 to 260 ° C. It is. In addition, the foamed sheet may be stretched in the MD direction or the CD direction or both after foaming or while foaming.
The foam sheet of the present invention preferably has a closed cell structure, but may have a closed cell structure including open cells.

[First unfoamed resin sheet]
The first unfoamed resin sheet (hereinafter, sometimes simply referred to as “first resin sheet”) is provided on one surface of the foamed sheet. For example, the first resin sheet is bonded and laminated to one surface of the foam sheet.
The melting point of the first resin sheet is a temperature below the melting point of the foam sheet, and is preferably a temperature below the melting point. Thereby, at the time of injection molding, when the high temperature resin collides with the composite foam sheet, the first resin sheet can be melted before the foam sheet melts. And heat is absorbed by fusion | melting of a 1st resin sheet, the temperature rise of a foam sheet is suppressed, and melting | fusing of a foam sheet can be suppressed. Furthermore, when laminating the foam sheet, the first resin sheet, and the second unfoamed resin sheet described below, the foamed sheet and the second unfoamed sheet are melted by melting the first resin sheet without melting the foam sheet. The connection between the foamed resin sheets can be strengthened.
On the other hand, when the melting point of the first resin sheet is higher than the melting point of the foamed sheet, the above-described effect does not occur.

From the viewpoint of the above effect, the temperature difference between the melting point of the first resin sheet and the melting point of the foamed sheet is preferably 5 to 50 ° C, more preferably 10 to 35 ° C.
In addition, melting | fusing point of a foam sheet and a 1st resin sheet can be measured using DSC (differential scanning calorimeter) based on JISK7121 (plastic transition temperature measuring method). When there are a plurality of melting peaks, the peak temperature of the melting peak on the highest temperature side is defined as the melting point of the resin sheet or foamed sheet. Furthermore, the melting point of the second unfoamed resin sheet described later and the melting point of the third unfoamed resin sheet can also be measured by the same method as that for the first resin sheet.

From the viewpoint of adhesiveness between the first resin sheet and the foam sheet, the first resin sheet contains at least one thermoplastic resin included in the resin composition used for the foam sheet. Is preferred. For example, when the resin composition used for the foam sheet contains a polyethylene resin, the resin constituting the first resin sheet is preferably a polyethylene resin, and when the resin composition used for the foam sheet contains a polypropylene resin The resin constituting the first resin sheet is preferably a polypropylene resin.
Therefore, since the thermoplastic resin contained in the resin composition is preferably a polyolefin resin, and more preferably a polypropylene resin, the resin constituting the first resin sheet is preferably a polyolefin resin and more preferably a polypropylene resin. .
The polyolefin resin and polypropylene resin used for the first resin sheet can be the same as the polyolefin resin and polypropylene resin used for the foamed sheet, respectively. However, the polyolefin resin and the polypropylene resin used for the first resin sheet are appropriately selected so that the melting point of the first resin sheet is equal to or lower than the melting point of the foam sheet.
The form of the first resin sheet may be either a single layer or a multilayer.

  From the viewpoint of suppressing the generation of gate marks in the composite foam sheet, and from the viewpoint of ensuring the flexibility of the composite foam sheet, the thickness of the first resin sheet is preferably 5 to 80 μm, and preferably 10 to 50 μm. More preferably.

[Second unfoamed resin sheet]
The second unfoamed resin sheet (hereinafter sometimes simply referred to as “second resin sheet”) is provided on the surface of the first resin sheet opposite to the surface of the foam sheet. For example, the second resin sheet is laminated by being bonded to the surface of the first resin sheet opposite to the surface on the foam sheet side.
A 2nd resin sheet is a sheet | seat for suppressing that the heat | fever of the injection molded high temperature resin transmits to a foamed sheet, and suppressing that a foamed sheet melt | dissolves. Therefore, the second resin sheet is preferably a sheet having excellent heat resistance that does not melt even when the high temperature resin collides with the composite foam sheet during injection molding. Specifically, the melting point of the second resin sheet is 160 ° C. or higher, preferably 170 ° C. or higher, and more preferably 190 ° C. or higher. If the melting point of the second resin sheet is less than 160 ° C., the second resin sheet may melt when the high temperature resin collides with the composite foam sheet during injection molding. In addition, although the upper limit of the range of melting | fusing point of a 2nd resin sheet is not specifically limited, For example, it is 270 degreeC, Preferably it is 240 degreeC.

Furthermore, by providing the composite foam sheet with the second resin sheet, it is possible to suppress the high temperature resin from wrapping around the side surface of the composite foam sheet during injection molding. Thereby, it can suppress that an avatar-like unevenness | corrugation generate | occur | produces in the edge of a composite foam sheet.
The form of the second resin sheet may be either a single layer or a multilayer.

  From the viewpoint that the melting point is 160 ° C. or more and from the viewpoint of adhesiveness with the first resin sheet, the resin constituting the second resin sheet is a polyamide resin, a polybutylene terephthalate resin, a polyethylene terephthalate resin, or the like. Of these, a polyamide resin is more preferable. These can be used alone or in combination of two or more.

<Polyamide resin>
The polyamide resin is a resin containing an amide group (—NHCO) in the molecular structure.
Examples of the polyamide resin used for the second resin sheet include nylon 6 (melting point: 225 ° C.), nylon 66 (melting point: 265 ° C.), nylon 610 (melting point: 215 ° C.), nylon 612 (melting point: 215 ° C.). Nylon 11 (melting point: 187 ° C.), nylon 12 (melting point: 176 ° C.), nylon 46 (melting point: 290 ° C.), semi-aromatic polyamide (melting point: 320 ° C.), and the like.

<Polybutylene terephthalate resin>
The polybutylene terephthalate resin is a kind of aromatic polyester having an ester group (—RCOO) in the molecule, and is a crystalline thermoplastic resin. The melting point of the polybutylene terephthalate resin is, for example, 225 ° C.

<Polyethylene terephthalate resin>
Polyethylene terephthalate resin is a crystalline resin obtained by polycondensation of terephthalic acid and ethylene glycol. The melting point of the polyethylene terephthalate resin is, for example, 245 ° C.

  From the viewpoint of suppressing the melting of the foam sheet during injection molding and the viewpoint of the flexibility of the composite foam sheet, the thickness of the second resin sheet is preferably 2 to 50 μm, and preferably 4 to 45 μm. More preferably, it is 7-40 micrometers, and it is still more preferable that it is 10-35 micrometers.

[Total thickness of first unfoamed resin sheet and second unfoamed resin sheet]
From the viewpoint of the flexibility and mechanical strength of the composite foam sheet, the total thickness of the first resin sheet and the second resin sheet is preferably 7 to 130 μm, more preferably 10 to 100 μm, More preferably, it is 13-90 micrometers, and it is especially preferable that it is 25-70 micrometers.

[Third unfoamed resin sheet]
The composite foam sheet of the present invention may be a third unfoamed resin sheet (hereinafter simply referred to as “third resin sheet”) provided on the surface of the second resin sheet opposite to the foam sheet side surface. May be included). For example, the composite foam sheet 1A as an example of the composite foam sheet of the present invention is provided with a third surface 34 provided on the surface 34 opposite to the surface 32 on the foam sheet 10 side of the second resin sheet 30 as shown in FIG. The unfoamed resin sheet 40 is included.
Thereby, the adhesiveness between the below-mentioned injection-molded base material and the composite foam sheet can be further enhanced.
From the viewpoint of bondability with the base material, the resin constituting the third resin sheet is preferably a polyolefin resin, and more preferably a polypropylene resin.
As the polyolefin resin and the polypropylene resin used for the third resin sheet, the same resins as the polyolefin resin and the polypropylene resin used for the first resin sheet can be used, respectively.
The resin used for the third resin sheet may be the same as or different from the resin used for the first resin sheet. However, in order to prevent the first resin sheet or the second resin sheet from being peeled off from the foamed sheet, the resin used for the third resin sheet is the same as the resin used for the first resin sheet. It is preferable.

From the viewpoint of bondability with a substrate described later, the thickness of the third resin sheet is preferably 5 to 80 μm, and more preferably 10 to 50 μm.
Note that the thickness of the third resin sheet may be the same as or different from the thickness of the first resin sheet. However, in order to prevent the first resin sheet or the second resin sheet from peeling off from the foamed sheet, the thickness of the third resin sheet is preferably the same as the thickness of the first resin sheet.

[Total thickness of first unfoamed resin sheet, second unfoamed resin sheet, and third unfoamed resin sheet]
From the viewpoint of the flexibility and mechanical strength of the composite foam sheet, the total thickness of the first resin sheet, the second resin sheet, and the third unfoamed resin sheet is preferably 12 to 210 μm, More preferably, it is 140 micrometers, and it is still more preferable that it is 50-120 micrometers.

[Composite foam sheet]
The composite foam sheet of the present invention is preferably formed by adhering and laminating a foam sheet, a first resin sheet, a second resin sheet, and, if desired, a third resin sheet.
Examples of a method for producing a composite foam sheet by laminating a foam sheet, a first resin sheet, a second resin sheet, and a third resin sheet, if desired, include an extrusion laminating method and a heat fusion laminating method. It is done. Note that a composite foam sheet may be manufactured by sequentially laminating a first resin sheet, a second resin sheet, and, if desired, a third resin sheet on the foam sheet. Alternatively, a composite foam sheet may be manufactured by laminating a multilayer sheet prepared by sequentially laminating a first resin sheet, a second resin sheet, and, if desired, a third resin sheet on the foam sheet.

  The first resin sheet and the second resin sheet may be provided on only one surface of the foamed sheet, or may be provided on both surfaces.

  The compressive strength at 25% compression of the composite foam sheet is preferably 100 kPa or less, more preferably 10 to 100 kPa, and still more preferably 20 to 95 kPa. When the compression strength at 50% compression of the thermally conductive foam is 100 kPa or less, the flexibility of the composite foam sheet is good. In addition, the compression strength at the time of 25% compression of the composite foam sheet was measured according to JISK6767-7.2.3 (JIS2009) on the surface of the composite foam sheet on the foamed resin sheet side.

[Molded body]
The molded body of the present invention is obtained by molding the composite foam sheet of the present invention by a known method. When manufacturing a molded object, other raw materials, such as a skin material and a base material, can be laminated | stacked and manufactured, Preferably it laminates | stacks with a base material.

(Skin material)
As the skin material, polyvinyl chloride sheet, sheet made of mixed resin of polyvinyl chloride and ABS resin, thermoplastic elastomer sheet, woven fabric, knitted fabric, non-woven fabric, artificial leather, synthetic leather, etc. using natural fiber or artificial fiber, etc. Examples include leather and metal. Moreover, it is good also as a composite molded object by which the design, such as a grain and a grain pattern, was given to the surface using the leather stamp etc. which attached the unevenness transferred from genuine leather, stone, wood, etc. When laminating the skin material on the composite foam sheet, the skin material is disposed on the foam sheet side.
Examples of methods for laminating skin materials include extrusion laminating, adhesive laminating after laminating an adhesive, thermal laminating (thermal fusing), hot melt, high frequency welder, and electroless metals Examples include plating, electrolytic plating, and vapor deposition.
What is necessary is just to adhere | attach both by any method.

(Base material)
The base material serves as a skeleton of the molded body, and a thermoplastic resin is usually used. As the thermoplastic resin for the substrate, the above-described polyolefin resin, a copolymer of ethylene and α-olefin, vinyl acetate, acrylic ester, ABS resin, polystyrene resin, or the like can be applied.
When laminating the base material on the composite foam sheet of the present invention, it is preferable to inject the base material resin to the unfoamed resin sheet side and laminate and integrate them.
At this time, if a resin having a considerably high melting point such as a polyamide-based resin or a polybutylene terephthalate-based resin is used as a base material, the melting temperature of the base material layer becomes high, and the bubbles destroy the foam sheet at the time of molding. Sometimes. Therefore, the first and second unfoamed resin sheets are configured so that the melting point of the base resin is lower than the melting points of the resins constituting the first and second unfoamed resin sheets. It is preferable to select the base resin so that the melting point of each resin to be made is higher than the melting point of the base resin.

Examples of the molding method of the molded body of the present invention include a stamping molding method, a vacuum molding method, a compression molding method, and an injection molding method. Among these, the injection molding method and the vacuum molding method are preferable, the injection molding method is more preferable, and the low pressure injection molding method (LPM method) is more preferable. By the LPM method, the composite foam sheet of the present invention can be formed into a molded body such as an automobile interior material having a complicated shape. In the injection molding, for example, a molded body may be obtained by injecting a resin constituting the base material into a composite foam sheet disposed in a metal cavity. In particular, since the composite foam sheet of the present invention is less likely to cause gate marks due to injection molding, the molded article of the present invention is less likely to have poor appearance. Alternatively, the composite foam sheet may be formed by vacuum forming or the like, and the formed composite foam sheet may be used for the injection molding.
The molded body formed by molding the composite foam sheet of the present invention can be used as a heat insulating material, a cushioning material, etc., particularly in the automotive field, such as ceiling materials, door trims, instrument panels, center cluster peripheral parts, etc. It can be suitably used as an automobile interior material.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited at all by these examples.
In addition, the measuring method of each physical property and the evaluation method of a foamed sheet are as follows.

(1) Density The density (apparent density) of the foam sheet was measured according to JIS K 7222.
(2) Sheet thickness Measured with a dial gauge.
(3) Crosslinking degree About 100 mg of a test piece is collected from the foamed sheet, and the mass A (mg) of the test piece is precisely weighed. Next, this test piece was immersed in 30 cm ³ of xylene at 120 ° C. and allowed to stand for 24 hours, and then filtered through a 200-mesh wire mesh to collect the insoluble matter on the wire mesh, vacuum dried, and the mass of the insoluble matter. Weigh B (mg) precisely. From the obtained value, the degree of crosslinking (% by mass) was calculated by the following formula.
Crosslinking degree (% by mass) = 100 × (B / A)
(4) Melting | fusing point Melting | fusing point of the foamed resin sheet and the non-foamed resin sheet was measured using DSC based on JISK7121.

(Manufacture of foam sheet)
Each resin component and additive shown in Table 1 are put into a single-screw extruder in the number of parts shown in Table 1, and melt-kneaded at a resin temperature of 190 ° C. to extrude a sheet-shaped resin composition having a predetermined thickness. Obtained. The resin composition was cross-linked by irradiating an electron beam with 1 Mrad at an acceleration voltage of 800 kV on both surfaces of the sheet-like resin composition. Thereafter, the crosslinked resin composition was heated at 250 ° C. for 5 minutes in a hot air oven and foamed by the heating to obtain a foamed sheet having a predetermined thickness. The results are shown in Table 1 below.

Details of the resin components and additives shown in Table 1 are as follows.
LLDPE: linear low density polyethylene resin, product name: 2036P, manufactured by Dow Chemical Co., MFR = 2.5 g / 10 min, melting point: 110-130 ° C.
Random PP: ethylene-propylene random copolymer, product name: Novatec EG7F, manufactured by Nippon Polypro Co., Ltd., MFR = 1.3 g / 10 min, ethylene content: 3% by mass, melting point: 130-150 ° C.
PP homopolymer: polypropylene homopolymer, product name: Novatec PP MA3, manufactured by Nippon Polypro Co., Ltd., MFR = 10 g / 10 min, melting point: 155 to 165 ° C.
Foaming agent: Azodicarbonamide Crosslinking aid: Trimethylolpropane trimethacrylate Antioxidant 1: 2,6-di-tert-butyl-p-cresol Antioxidant 2: Dilaurylthiodipropionate

(Manufacture of composite foam sheet)
After laminating the first non-foamed resin sheet, the second non-foamed sheet, and the third non-foamed sheet in this order, heat press molding was performed at 245 ° C. to produce a multilayer sheet. And after laminating the obtained multilayer sheet on a foam sheet, it heat-press-molds at 180 degreeC, a foamed resin sheet / first unfoamed resin sheet / second unfoamed resin sheet / third unfoamed resin sheet A composite foam sheet laminated in this order was manufactured.
The following resin sheets were used as the first unfoamed resin sheet, the second unfoamed resin sheet, and the third unfoamed resin sheet.
First unfoamed resin sheet: unstretched polypropylene film, product name: pyrene film-CTP1128, manufactured by Toyobo Co., Ltd., melting point: 135 to 150 ° C
Second unfoamed resin sheet: nylon 6 film, product name: Emblem ON-5 (thickness: 5 μm), ON-15 (thickness: 15 μm), ON-25 (thickness: 25 μm), manufactured by Unitika Ltd., melting point: 225 ° C
Third unfoamed resin sheet: unstretched polypropylene film, product name: pyrene film-CTP1128, manufactured by Toyobo Co., Ltd., melting point: 135-150 ° C

[Vacuum formability evaluation]
The composite foam sheets of Examples and Comparative Examples were molded into a cup shape by scalpeling at a molding temperature of 170 ° C. by vacuum molding, and the moldability was evaluated.

<Vacuum formability>
About the obtained cup-shaped molded object, the vacuum moldability was evaluated according to the following criteria.
5: A wrinkle or a torn part was not confirmed in the cup-shaped molded body.
4: Although the torn part was not confirmed, slight wrinkles were confirmed by the cup-shaped molded object. However, there was no problem in practical use.
3: Although the torn part was not confirmed, wrinkles were confirmed on a part of surface of a cup-shaped molded object. However, there was no problem in practical use.
2: Although the torn part was not confirmed, the big wrinkle was confirmed by the cup-shaped molded object. And it was a problematic level for practical use.
1: The location where the cup-shaped molded body was torn was confirmed.
[LPM moldability evaluation]

(Substrate formation by injection molding)
After the cup-shaped molded body prepared by the vacuum moldability evaluation was placed in an injection mold, a base material (random polypropylene, manufactured by Nippon Polypro Co., Ltd., Novatec BC4BSW, MFR = 5.0 g / 10 min, melting point: 135- 150 ° C.) was injected (injection temperature: 190 ° C.) to obtain a concave molded body. In addition, the obtained recessed molded object was laminated | stacked in order of skin material / foamed sheet / first unfoamed resin sheet / second unfoamed resin sheet / third unfoamed resin sheet / base material. .
Using the obtained concave molded body, low-pressure injection moldability (LPM moldability) was evaluated. The results are shown in Table 1 below.

<LPM moldability>
The surface appearance of the obtained concave shaped body was visually observed to check for the presence or absence of the gate mark dent, and the appearance was judged according to the following criteria. Moreover, the depth of the dent of the gate mark was also measured using a caliper.
(Criteria)
A: There is no dent of the gate mark.
B: Although the position where the gate is located can be recognized by a slight depression of the gate mark, it is at a level that causes no problem in practice.
C: Although the dent of the gate mark can be seen slightly, there is no practical problem.
D: A dent of the gate mark is slightly visible, and there is a practical problem.
E: The depression of the gate mark can be clearly seen, and there is a problem in practical use.
F: The dent of the gate mark is deep and has a problem in practical use.

[Flexibility evaluation]
Flexibility was evaluated using the obtained concave shaped body. The results are shown in Table 1 below.
<Flexibility sensory evaluation (soft sensory evaluation)>
The surface on the foamed resin sheet side of the obtained concave molded body was pressed with a finger, and the tactile sensation was evaluated in five stages of 1 to 5. “1” indicates the hardest, and a larger number indicates softer. If the evaluation is 3 or more, there is no practical problem.

<25% compressive strength>
The compression strength at 25% compression (25% compression strength) was measured in accordance with JIS K6767-7.2.3 (JIS 2009) on the surface of the concave molded body on the foamed resin sheet side.

  From Table 1, it was found that the composite foam sheet of the present invention has flexibility and can suppress generation of gate marks due to injection molding.

1, 1A Composite foam sheet 10 Thermoplastic resin foam sheet 20 First unfoamed resin sheet 30 Second unfoamed resin sheet 40 Second unfoamed resin sheet 100 Resin foam 160 Gate mark 500 Injection molded resin 600 Gate

Claims (8)

A thermoplastic resin foam sheet, a first non-foamed resin sheet provided on one surface of the thermoplastic resin foam sheet, and a surface of the first non-foamed resin sheet opposite to the surface of the thermoplastic resin foam sheet A second unfoamed resin sheet provided on the side surface,
The melting point of the first unfoamed resin sheet is equal to or lower than the melting point of the thermoplastic resin foam sheet;
A composite foamed sheet, wherein the second unfoamed resin sheet has a melting point of 160 ° C or higher.   The composite foamed sheet according to claim 1, wherein the resin constituting the second unfoamed resin sheet is at least one resin selected from the group consisting of a polyamide resin, a polybutylene terephthalate resin, and a polyethylene terephthalate resin. . A third unfoamed resin sheet is provided on the surface opposite to the surface of the thermoplastic resin foam sheet in the second unfoamed resin sheet,
The composite foam sheet according to claim 1 or 2, wherein a resin constituting the third unfoamed resin sheet is a polyolefin resin.   The composite foam sheet according to claim 3, wherein the resin constituting the third unfoamed resin sheet is a polypropylene resin.   The composite foam sheet of any one of Claims 1-4 whose sum total of the thickness of a said 1st unfoamed resin sheet and a said 2nd unfoamed resin sheet is 10-100 micrometers.   The composite foam sheet according to any one of claims 1 to 5, wherein the thermoplastic resin foam sheet is a polyolefin resin foam sheet.   The molded object obtained by shape | molding the composite foam sheet of any one of Claims 1-6. The molded article according to claim 7, which is an automobile interior material.