JP6701783B2 - Multilayer foamed sheet having a non-foamed layer containing a long-chain branched polypropylene resin composition - Google Patents

Description

  The present invention includes a method for producing a multilayer foam sheet in which corrugation during production in circular extrusion foam molding is suppressed by using a resin composition for a non-foaming layer containing a specific polypropylene resin composition, and the polypropylene resin composition. The present invention relates to a multilayer foamed sheet having a non-foamed layer, and a molded product obtained by molding the multilayer foamed sheet.

  The foamed sheet obtained by extrusion foam molding of polypropylene resin is lightweight and has excellent heat resistance, impact resistance, chemical resistance, etc., so it can be used in a wide range of applications such as building materials, stationery, automobile interior materials and food containers. Is expected. Such a foamed sheet is foamed by adding various foaming agents to a polypropylene resin composition melted in an extruder, kneading under pressure, and extruding under atmospheric pressure from a die attached to the tip of the extruder. It is obtained by taking out the molten resin while spreading, cooling and solidifying. At this time, it is important to further improve the lightness and the heat insulating property, that is, the expansion ratio from the viewpoint of reducing the environmental load.

  In extrusion foam molding of polypropylene-based resin, a T die or a circular die is generally used, but it is effective to improve the expansion ratio by taking out the molten resin while foaming it more isotropically. Dies are widely used.

  In extrusion foam molding using a circular die (hereinafter, also referred to as circular foam molding), the molten resin extruded from the circular die is stretched and cooled by a cooling mandrel having an outer diameter larger than the annular slit diameter, and passed through the cooling mandrel. A foamed sheet is manufactured by cutting open a tubular foam using a cutter or the like.

  In circular foam molding, a problem that a molten resin corrugates in the circumferential direction of a die, a so-called corrugate, becomes a problem as the expansion ratio increases. It is considered that the corrugation occurs when the volume expansion of the molten resin due to the foaming in the circumferential direction exceeds the expansion by the mandrel. The larger the amount of the foaming agent introduced (the higher the target expansion ratio), the larger the volume expansion. Further, the problem of corrugation occurs even when the thickness of the foamed sheet is increased by decreasing the take-up speed.

  Here, in order to suppress the corrugate, a method of increasing the viscosity of the resin at the time of molding by suppressing the molding temperature or the melt flow rate (MFR) of the resin to suppress the rate of volume expansion can be considered. . However, when the amount of the foaming agent is large, the viscosity of the resin is significantly decreased by the foaming agent, and the amount of vaporization of the foaming agent increases, which further increases the volume expansion rate. It is very difficult to control the volume expansion by this method.

  Further, in order to suppress the corrugate, it is generally considered effective to increase the blow-up ratio, which is determined by the die outlet diameter and the cooling mandrel outer diameter. However, since the volume expansion of the molten resin occurs immediately after leaving the die, increasing the blow-up ratio does not mean that the corrugate itself is suppressed. As the thickness of the sheet becomes more uneven and the blow-up ratio becomes larger, the foamed sheet hits the mandrel more strongly, which tends to cause a reduction in the expansion ratio and a deterioration in the appearance.

  In such a situation, not only foaming characteristics such as expansion ratio and unevenness of expansion ratio are bad, but it is also difficult to beautifully print or print on the surface of the sheet due to the deterioration of the appearance, or to laminate a film or the like, Furthermore, since the formability deteriorates during secondary processing such as vacuum forming, it is a major problem to suppress corrugations during forming.

  Several reports have been made regarding circular foam molding using a polypropylene resin in order to suppress corrugation (Patent Documents 1 and 2).

  In Patent Document 1, in order to obtain a thick foam sheet having a thickness of 3 to 10 mm without generating corrugations by circular foam molding, a plurality of thinner foam sheets are melt-bonded to obtain a foam sheet having a desired thickness. A method has been proposed. According to this proposal, it is possible to solve the problem of uneven thickness and variation in bubble diameter due to corrugations, but there is a problem that it is necessary to increase the number of manufacturing processes because melt bonding is performed in the post process of foam molding. is there.

  In Patent Document 2, in order to suppress corrugations during circular foam molding, a foam sheet having a smaller thickness than the purpose is manufactured in advance, and subsequently, a non-foam resin layer having a thickness of 10 to 200 μm is provided between the foam sheets. A method of producing a polypropylene resin composition multilayer foam sheet having a thickness of 3 to 10 mm by an extrusion laminating method is proposed. In this proposal as well, the method of increasing the thickness by stacking a plurality of thin foam sheets is used, so that there is a problem that the process is complicated.

JP-A-7-227930 JP, 2009-274416, A

  In view of such circumstances, it is an object of the present invention to obtain a foamed sheet that suppresses corrugations during manufacturing, has a smooth surface, and has a high expansion ratio in circular foam molding.

The present inventors have conducted diligent research on the suppression of corrugations, and in order to suppress the volume expansion due to foaming from the die outlet in the circumferential direction, a resin composition containing polypropylene having a long-chain branched structure is used. The present invention has been found out that the formation of a corrugate is remarkably improved by providing the foamed layer, and the present invention has been completed.
That is, a non-foamed layer containing a resin composition containing polypropylene having a long-chain branched structure regulates excessive expansion due to foaming due to strain hardening (increase in viscosity due to strain) during volume expansion due to foaming. However, it was found that the corrugation can be suppressed.
In addition, by providing a specific non-foaming layer to suppress corrugation, outgassing is also suppressed, so the expansion ratio is improved, and when this is used as the surface layer, the smoothness of the surface is improved. Can also be obtained.

That is, the present invention includes the following.
[1] Polypropylene resin composition (X) (5) to 100% by weight of a polypropylene resin (X1) having a long-chain branched structure and 0 to 95% by weight of a polypropylene resin (X2) not having a long-chain branched structure. Provided that the total amount of the polypropylene resin (X1) and the polypropylene resin (X2) is 100% by weight).
A multilayer foam sheet comprising a polypropylene resin (W) and a foam layer having an expansion ratio of 4.0 or more.
[2] The multilayer foamed sheet according to claim 1, wherein the polypropylene resin (W) is a polypropylene resin having no long-chain branched structure.
[3] A multilayer foamed molded article comprising the multilayer foamed sheet according to claim 1 or 2.
[4] Polypropylene resin composition (X) (5) to 100% by weight of a polypropylene resin (X1) having a long-chain branched structure and 0 to 95% by weight of a polypropylene resin (X2) not having a long-chain branched structure. However, the total amount of the polypropylene resin (X1) and the polypropylene resin (X2) is 100% by weight, and a resin composition for a non-foaming layer,
A resin composition for a foam layer containing a polypropylene resin (W) and a foaming agent,
A method for producing a multilayer foam sheet, which comprises co-extruding from a circular die.
[5] The method for producing a multilayer foamed sheet according to claim 4, wherein the polypropylene resin (W) is a polypropylene resin having no long chain branch structure.

In a multilayer foam provided with a non-foamed layer using the polypropylene resin composition of the present invention, corrugation during molding is largely suppressed, there is no unevenness in the thickness and foaming state in the circumferential direction, and the multilayer foam has excellent smoothness. A sheet is obtained and, in addition, outgassing is suppressed, so that the expansion ratio is easily improved.
Since the molded product is excellent in impact resistance, light weight, rigidity, heat resistance, heat insulation, oil resistance, etc., it is a tray that is compatible with heating with a microwave oven and filling with hot liquids such as hot beverages. It can be suitably used for food containers such as plates and cups, automobile door trims, vehicle interior materials such as automobile trunk mats, building materials and packaging, and stationery.

  The present invention will be described in detail below.

1. Multilayer Foamed Sheet The multilayer foamed sheet of the present invention will be described below.
The multilayer foamed sheet of the present invention comprises 5 to 100% by weight (including 100% by weight) of a polypropylene resin (X1) having a long chain branch structure and 0 to 95% by weight of a polypropylene resin (X2) having no long chain branch structure. % Of the polypropylene resin composition (X) (provided that the total amount of the polypropylene resin (X1) and the polypropylene resin (X2) is 100% by weight) and the polypropylene resin (W). And a foam layer having an expansion ratio of 4.0 or more. That is, the multilayer foamed sheet of the present invention has the polypropylene resin composition (W) as the foaming layer and the polypropylene resin composition (X) as the non-foaming layer.

  The layer constitution may be a non-foamed layer/foamed layer two-kind two layer or a non-foamed layer/foamed layer/non-foamed layer two-layer three-layered layer structure, but in addition, the effect of the present invention is not impaired As long as there are three kinds of three layers such as non-foaming layer/foaming layer/other resin layer and three kinds of five layers such as non-foaming layer/foaming layer/other resin layer/foaming layer/non-foaming layer It is also possible to include a plurality of layers sandwiching the resin layer, and for example, a layer having a necessary function such as a gas barrier layer and an impact resistance imparting layer can be provided according to the purpose.

  It is desirable that the total thickness of the non-foamed layer laminated on one side or both sides of the foamed layer is 0.1 to 50%, preferably 0.1 to 20% of the entire multilayer foamed sheet. When the thickness of the non-foamed layer is within the above range, a sufficient corrugate suppressing effect can be obtained.

  On the outside of the non-foamed layer, a printed layer, a decorative layer, etc. can be provided as long as the effects of the present invention are not impaired. An adhesive layer or the like can be provided between the foam layer and the other resin layer.

  In the present invention, from 5 to 100% by weight (including 100% by weight) of a polypropylene resin (X1) having a long chain branched structure and from 0 to 95% by weight of a polypropylene resin (X2) having no long chain branched structure. The polypropylene resin composition (X) (wherein the total amount of the polypropylene resin (X1) and the polypropylene resin (X2) is 100% by weight), and the polypropylene resin (W) And a resin composition for a foam layer containing a foaming agent are coextruded from a circular die to produce a multilayer foam sheet. It is preferable to provide a multi-layer foamed sheet including a non-foamed layer having the polypropylene resin composition (X) as a base material and a foamed layer made of the polypropylene resin (W) having an expansion ratio of 4.0 or more.

  The thickness of the multilayer foam sheet according to the present invention is not particularly limited, but is preferably about 0.3 mm to 30 mm. More preferably, it is 0.5 mm to 10 mm. When the sheet thickness is within this range, practical strength and physical properties are excellent, and defects such as bending and folding of the multilayer foam sheet during molding are less likely to occur.

  The non-foamed layer may be laminated on either the inside (the side in contact with the cooling mandrel) or the outside or both sides of the foamed layer. In addition to the non-foaming layer, there is no limitation on the form of disposing the non-foaming layer such as providing a barrier layer or an adhesive layer. However, in any case, at least one layer having the polypropylene resin composition for a non-foamed layer (X) as a base material shown in the present invention must be laminated. The effect of suppressing corrugation can be obtained in any of the inside and outside of the foam layer, and at this time, the layer based on the polypropylene resin composition for non-foam layer (X) is at least inside the foam layer. By providing one layer, the effect of suppressing volume expansion due to foaming is high, and a larger corrugate suppressing effect can be obtained, which is preferable.

  Further, in the multilayer foamed sheet of the present invention, in order to further improve printability and paintability, even if the surface of the foamed sheet is subjected to surface treatment such as corona discharge treatment, flame treatment, plasma treatment, etc. It doesn't matter.

  The thickness of the non-foamed layer is desirably 0.1 to 50%, preferably 0.1 to 20% of the total thickness of the obtained polypropylene-based multilayer foamed sheet. When the thickness of the non-foamed layer is in this range, a high corrugation-suppressing effect can be obtained even when the sheet becomes thicker, the amount of the introduced foaming agent is large, and corrugates are likely to be remarkable during production, and Since the growth of bubbles in the foam layer is not hindered, a high expansion ratio can be achieved and the lightweightness of the multilayer foam sheet can be maintained.

2. Polypropylene resin composition (X)
The multilayer foamed sheet in the present invention needs to include a non-foamed layer made of the polypropylene resin composition (X).
The non-foamed layer made of the polypropylene resin composition (X) is a layer necessary for suppressing the volume expansion rate of the molten resin in the foaming process, and for suppressing the volume expansion of the molten resin discharged from the die due to the foaming. In addition, it is necessary to include a polypropylene resin (X1) having a long-chain branched structure. At this time, the polypropylene resin composition (X) needs to contain a sufficient amount of the polypropylene resin (X1) to suppress corrugation, but contains the polypropylene resin (X2) having no long chain branching. It is possible.

2.1. Polypropylene resin having a long-chain branched structure (X1)
The polypropylene resin (X1) having a long-chain branched structure used in the present invention may be a propylene homopolymer or a propylene copolymer. When it is a propylene copolymer, the comonomer is at least one olefin selected from the group consisting of ethylene and α-olefins having 4 to 10 carbon atoms, and the content of the comonomer in the polypropylene resin (X1) is 3% by weight. % Or less is preferable. The polypropylene resin (X1) is preferably a propylene homopolymer because it has high heat resistance and rigidity.

  The polypropylene resin (X1) is a component necessary for suppressing corrugation due to high melt tension, and must have long chain branching. The long-chain branch in the present invention refers to a branched structure with a molecular chain consisting of several tens of main chain carbon atoms in order to express high melt tension and strain hardening property, and a molecular weight of several hundreds or more, such as 1-butene. A distinction is made from short chain branches formed by copolymerization with α-olefins.

  As a method for introducing a long-chain branched structure into a polypropylene resin, a method using high-energy ionizing radiation (Japanese Patent Laid-Open No. 62-121704), a method using organic peroxide (Japanese Patent Publication No. 2001-524565), or a specific method A method for producing a macromonomer having a terminal unsaturated bond by using a metallocene catalyst having the structure of and forming a long chain branch by copolymerizing it with propylene (Japanese Translation of PCT International Publication No. 2001-525460). Regardless of which method is used, the melt tension of the polypropylene resin can be greatly improved.

  The polypropylene resin (X1) having a long chain branched structure is not particularly limited as long as it has a long chain branched structure, but has a comb chain structure and a long chain branched structure is formed during polymerization. A method using a macromer copolymerization method is preferable. As an example of such a method, for example, Japanese Patent Laid-Open No. 2001-525460, Japanese Patent Laid-Open No. 10-338717, Japanese Patent Laid-Open No. 2002-523575, Japanese Patent Laid-Open No. 2009-57542, Japanese Patent No. 050237353, Japanese Patent Laid-Open No. The method disclosed in Kaihei 10-338717 is mentioned. In particular, the macromer copolymerization method disclosed in JP-A-2009-57542 is suitable for the present invention because it can give a polypropylene resin containing a long chain branch without generation of gel.

Having a long chain branch in polypropylene is defined by a method based on the rheological properties of the resin, a method of calculating a branching index g′ using the relationship between the molecular weight and viscosity, a method of using ¹³ C-NMR, and the like. In the present invention, the long-chain branched structure is defined by the branching index g′ and ¹³ C-NMR as shown below.

[Branching index g']
The branching index g'is known as a direct index for long chain branching. A detailed description is given in "Developments in Polymer Characterization-4" (JV Dawkins ed. Applied Science Publishers, 1983), and the definition of the branching index g'is as follows.

Branch index g′=[η]br/[η]lin
[Η]br: Intrinsic viscosity of polymer (br) having long-chain branched structure [η]lin: Intrinsic viscosity of linear polymer having the same molecular weight as polymer (br)

  As is clear from the above definition, when the branching index g'has a value smaller than 1, it is judged that a long chain branching structure exists, and the value of the branching index g'will decrease as the number of long chain branching structures increases. ..

The branching index g′ can be obtained as a function of the absolute molecular weight Mabs by using a GPC equipped with a light scatterometer and a viscometer in the detector. The method for measuring the branching index g'in the present invention is described in detail in JP-A-2005-40213, and is as follows.
[Measuring method]
GPC: Alliance GPCV2000 (Waters)
Detector: Described in order of connection Multi-angle laser light scattering detector (MALLS): DAWN-E (Wyatt Technology)
Differential Refractometer (RI): GPC included Viscosity detector (Viscometer): GPC included Mobile phase solvent: 1,2,4-trichlorobenzene (Irganox 1076 added at a concentration of 0.5 mg/mL)
Mobile phase flow rate: 1 mL/min Column: Tosoh GMHHR-H(S) Two HTs connected Sample injection part temperature: 140°C
Column temperature: 140℃
Detector temperature: All 140 ℃
Sample concentration: 1 mg/mL
Injection volume (sample loop volume): 0.2175 mL

[analysis method]
In obtaining the absolute molecular weight (Mabs), the root mean square radius of gyration (Rg), and the intrinsic viscosity ([η]) obtained from the Viscometer obtained from the multi-angle laser light scattering detector (MALLS), data processing attached to MALLS was performed. Calculation is performed using software ASTRA (version 4.73.04) with reference to the following documents.
References:
1. "Developments in Polymer Characterization-4" (JV Dawkins ed. Applied Science Publishers, 1983. Chapter 1).
2. Polymer, 45, 6495-6505 (2004).
3. Macromolecules, 33, 2424-2436 (2000).
4. Macromolecules, 33, 6945-6952 (2000).

Further, when the non-foamed layer containing the polypropylene resin constitutes the surface of the product, if the polypropylene resin contains a gel, the appearance is deteriorated. Therefore, it is preferable to use a gel-free product. The polypropylene resin (X1) having a long-chain branched structure described above is prepared by preparing a macromonomer having a terminal unsaturated bond using a metallocene catalyst having a specific structure, and copolymerizing the macromonomer with propylene to form a long-chain branched structure. Those manufactured using the method for forming are preferred. In particular, it is preferable that the branching index g′ at an absolute molecular weight Mabs of 1,000,000 described below satisfies 0.3 or more and less than 1.0, more preferably 0.55 or more and 0.98 or less, still more preferably 0. It is 75 or more and 0.96 or less, and most preferably 0.78 or more and 0.95 or less. If the branching index g'is in this range, highly crosslinked components are not formed and gel is not formed or is very small. Therefore, the non-foamed layer containing the polypropylene resin (X1) is especially on the surface of the product. Does not deteriorate the appearance when configuring.
[ ¹³ C-NMR]
As described above, ¹³ C-NMR can distinguish between a short-chain branched structure and a long-chain branched structure. Macromol. Chem. Phys. 2003, vol. A detailed description is given in 204 and 1738, but it is as follows.
The propylene-based polymer having a long chain branched structure has a specific branched structure as shown in the following structural formula (1). In Structural Formula (1), Ca, Cb, and Cc represent methylene carbons adjacent to the branched carbon, Cbr represents the methine carbon at the base of the branched chain, and P1, P2, and P3 represent propylene-based polymer residues. Indicates.
P1, P2, and P3 may contain a branched carbon (Cbr) different from the Cbr described in the structural formula (1) in itself.

Such a branched structure is identified by ¹³ C-NMR analysis. The attribution of each peak is described in Macromolecules, Vol. 35, No. 10. 2002, pages 3839-3842 can be referred to. That is, a total of 3 methylene carbons (Ca, Cb, Cc) were observed at 43.9 to 44.1 ppm, 44.5 to 44.7 ppm, and 44.7 to 44.9 ppm, and 31.5 were observed. Methine carbon (Cbr) is observed at ~31.7 ppm. Hereinafter, the methine carbon observed at 31.5 to 31.7 ppm may be abbreviated as branched methine carbon (Cbr).
The feature is that three methylene carbons close to the branched methine carbon Cbr are observed in three non-equivalently divided diastereotopic topics.

Such a branched chain assigned by ¹³ C-NMR indicates a propylene-based polymer residue having 5 or more carbon atoms branched from the main chain of the propylene-based polymer, and the branched chain having 4 or less carbon atoms is branched. Since it can be distinguished by the difference in the carbon peak position, in the present invention, the presence or absence of the long-chain branched structure can be determined by confirming the branched methine carbon peak.
The ¹³ C-NMR measuring method in the present invention is described in detail in Japanese Patent No. 4555966, but is as follows.
[ ¹³ C-NMR measurement method]
Regarding the branched structure of the propylene polymer of the present invention, the branched structure was measured and analyzed under the following conditions using the following NMR spectrometer.
A sample (470 mg) was completely dissolved in deuterated 1,1,2,2-tetrachloroethane (2.6 ml) in an NMR sample tube (10φ), heated at 120° C., and then measured. The chemical shift was set so that the central peak of the three deuterated 1,1,2,2-tetrachloroethane peaks was 74.2 ppm. Chemical shifts of other carbon peaks are based on this.
Device name: Varian Unity Inova
Flip angle: 90 degrees Pulse repetition time: 15.0 seconds Resonance frequency: 125.7 MHz
Total number of times: 14,400 times

[Melting tension MT]
In order to sufficiently exert the effect of suppressing corrugation in the present invention, melt tension can be used as a useful index for controlling excessive volume expansion of the resin discharged from the die during molding. When the resin having a high melt tension is placed in the non-foamed layer, the volume expansion rate of the foamed layer can be suppressed in the foaming process, and thus the effect of suppressing the corrugation caused by excessive expansion is enhanced. The melt tension (MT) of the polypropylene resin (X1) according to the present invention is preferably 2 to 25 g. The melt tension (MT) in the present invention is a value measured under the following conditions.

[MT measurement conditions]
Measuring device: Capillograph 1B manufactured by Toyo Seiki Co., Ltd.
Capillary: diameter 2.0 mm, length 40 mm
Cylinder diameter: 9.55 mm
Cylinder extrusion speed: 20 mm/min Take-up speed: 4.0 m/min (However, if MT is too high and the resin breaks, lower the take-up speed and measure at the highest speed that can be taken.)
Temperature: 230 ℃

Regarding the lower limit of MT of the polypropylene resin (X1) according to the present invention, MT is preferably 3 g or more. Regarding the upper limit of MT, MT is preferably 20 g or less, and more preferably MT is 18 g or less.
Specific methods for controlling MT within the above range include adjusting the MFR, adjusting the catalyst production method (particularly, the loading ratio of the complex), performing electron beam irradiation, or using a granulation step. There is a method of changing the number of long chain branches by adding an oxide or the like. MT increases with increasing number of long chain branches and decreasing MFR. On the other hand, MT can be lowered by adjusting in the opposite direction.

The MFR of the polypropylene resin (X1) according to the present invention is preferably more than 0.5 g/10 minutes and 20 g/10 minutes or less.
The MFR in the present invention is the method A, condition M (230° C., 2.16 kg load) of JIS K7210:1999 “Plastics-Test methods for melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics”. It is the value measured according to.

The lower limit of the MFR of the polypropylene resin (X1) according to the present invention is preferably 1 g/10 minutes or more, more preferably 2 g/10 minutes or more. The upper limit of MFR is preferably 17 g/10 minutes or less, more preferably 15 g/10 minutes or less, further preferably 13 g/10 minutes or less, and most preferably 10 g/10 minutes or less.
As a specific method for adjusting the MFR within the above range, a method of changing the amount of hydrogen added during the polymerization can be mentioned. Since hydrogen acts as a chain transfer agent in the polymerization of propylene, increasing the addition amount of hydrogen increases the MFR, and conversely, decreasing the addition amount can decrease the MFR. The value of MFR with respect to the hydrogen concentration in the polymerization tank varies depending on the catalyst used and other polymerization conditions, but the relationship between the hydrogen concentration and MFR is grasped in advance according to the catalyst species and other polymerization conditions, and the desired MFR It is extremely easy for a person skilled in the art to adjust the hydrogen concentration so as to obtain the value.

  The polypropylene resin (X1) according to the present invention preferably has a 25° C. xylene-soluble component amount (CXS) of less than 5% by weight (provided that the total amount of the polypropylene resin (X1) is 100% by weight). CXS is a general index representing a low crystalline polymer component, and when the amount of this component is large, the content of the low crystalline polymer component in the polypropylene resin (X1) is high, and eye bleeding is likely to occur during molding. .. Further, when the layer made of the polypropylene resin (X1) constitutes the surface, there arises a problem that the sheet surface is easily sticky. The CXS in the present invention is a value measured by the following procedure.

[CXS measurement procedure]
A 2 g sample is dissolved in 300 ml of p-xylene (containing 0.5 mg/ml of BHT) at 130°C to form a solution, and then the solution is left at 25°C for 12 hours. Then, the precipitated polymer is separated by filtration, p-xylene is evaporated from the filtrate, and dried under reduced pressure at 100° C. for 12 hours to recover a 25° C. xylene-soluble component. The ratio [% by weight] of the weight of this recovered component to the weight of the charged sample is defined as CXS.

The CXS of the polypropylene resin (X1) according to the present invention is preferably less than 5% by weight. The CXS is more preferably less than 3% by weight, even more preferably less than 1% by weight and most preferably less than 0.5% by weight. The lower limit of CXS is not particularly limited, but is preferably 0.01% by weight or more, more preferably 0.05% by weight or more.
As a specific method for adjusting CXS within the above range, selection of a catalyst can be mentioned. The most important factor for determining the CXS of a polypropylene having a long chain branch is a catalyst, and a known catalyst satisfying CXS may be selected.

The isotactic triad fraction (mm fraction) determined by ¹³ C-NMR of the polypropylene resin (X1) according to the present invention is preferably 95% or more.

Here, the mm fraction refers to the abundance of two consecutive propylene units having three consecutive meso steric relationships between adjacent methyl groups, and the definition in the present invention is described in JP-A-2009-275207. The description in paragraphs [0053] to [0065] shall be followed. The higher the mm fraction, the more regularly the propylene units in the polymer chain are arranged, and the higher the crystallinity is. Higher crystallinity is preferable because it increases heat resistance and rigidity.
¹³ C-NMR measurement conditions are also in accordance with JP 2009-275207 A.
In the present invention, the mm fraction is preferably 95% or more, more preferably 96% or more, and further preferably 97% or more.
As a specific method for adjusting the mm fraction within the above range, selection of the catalyst can be mentioned. The most important factor for determining the mm fraction of polypropylene having a long chain branch is a catalyst, and a known catalyst satisfying the mm fraction may be selected.

2.2. Polypropylene resin without long-chain branch structure (X2)
The polypropylene resin (X2) is not particularly limited in kind as long as it does not have a long chain branching structure, and a linear homopolypropylene not containing a long chain branching structure, propylene-α-. Any of olefin random copolymer, block polypropylene and the like can be used. Examples of the α-olefin include ethylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1. Examples of the polypropylene resin (X2) include linear homopolypropylene, propylene-ethylene random copolymer, and block polypropylene.

  Homopolypropylene, propylene-ethylene random copolymer, and block polypropylene will be described below in order.

2.2.1. Homopolypropylene (X2H), propylene-ethylene random copolymer (X2C)
Homopolypropylene (X2H) and propylene-ethylene random copolymer (X2C) are homopolymers of propylene or random copolymers of propylene and less than about 10% by weight of ethylene, and homopolypropylene (X2H) and propylene- The ethylene random copolymer (X2C) may contain, for example, 3% by weight or less as a comonomer of at least one olefin selected from the group consisting of α-olefins having 4 to 10 carbon atoms.
Specific examples of the α-olefin having 4 to 10 carbon atoms include 1-butene, 1-hexene and 1-octene. Most preferred among the comonomers are ethylene and 1-butene.
It is customary to control the comonomer content by appropriately adjusting the amount ratio of the monomer supplied to the polymerization tank (eg, the ratio of ethylene to propylene). The copolymerization characteristics of the catalyst to be used may be investigated in advance, and the monomer supply amount ratio may be adjusted so that the gas composition in the polymerization tank has a value corresponding to the desired comonomer content.

The homopolypropylene (X2H) and the propylene-ethylene random copolymer (X2C) preferably have an MFR of 1 to 100 g/10 minutes. Regarding the upper limit value, the MFR of homopolypropylene (X2H) and propylene-ethylene random copolymer (X2C) is more preferably 70 g/10 minutes or less, further preferably 50 g/10 minutes or less, and most preferably 30 g/10 minutes. It is below. Regarding the lower limit value, the MFR of homopolypropylene (X2H) and propylene-ethylene random copolymer (X2C) is more preferably 0.5 g/10 minutes or more, further preferably 1 g/10 minutes or more, and most preferably 2 g/ 10 minutes or more.
As a specific method of adjusting the MFR, a method of changing the amount of hydrogen added during the polymerization can be mentioned.
The method for measuring MFR is as described above.

2.2.2. Block polypropylene (X2Y)
Block polypropylene (X2Y) is usually a reactor blend of a polypropylene component and a propylene-ethylene copolymer component. The polypropylene component is preferably homopolypropylene (X2H), propylene-ethylene random copolymer (X2C), or a mixture thereof described above.

  The propylene-ethylene random copolymer component is a copolymer of propylene and ethylene, but may be a copolymer of other monomers as long as the effects of the present invention are not impaired.

The propylene-ethylene random copolymer component preferably has an intrinsic viscosity of 5.3 dl/g or more measured in decalin at 135°C.
The intrinsic viscosity of the propylene-ethylene random copolymer component is more preferably 6 dl/g or more, further preferably 7 dl/g or more, most preferably 8 dl/g or more, more preferably 16 dl/g or less, further preferably Is 13 dl/g or less, most preferably 11 dl/g or less.
As a specific method of adjusting the intrinsic viscosity of the propylene-ethylene random copolymer component, a method of changing the hydrogen concentration during polymerization can be mentioned.

In the block polypropylene (X2Y), the content of the propylene-ethylene random copolymer component in the block polypropylene (X2Y) is usually 1% by weight or more and less than 50% by weight (however, the total amount of the block polypropylene (X2Y) is 100% by weight. And).
The content of the propylene-ethylene random copolymer component in the block polypropylene (X2Y) is preferably 3% by weight or more, more preferably 5% by weight or more, further preferably 8% by weight or more, and most preferably 10% by weight or more. It is preferably 45% by weight or less, more preferably 40% by weight or less, further preferably 35% by weight or less, and most preferably 30% by weight or less.
Since the total amount of block polypropylene (X2Y) is 100% by weight, the content of the polypropylene component is a value obtained by subtracting the content of the propylene-ethylene random copolymer component from 100% by weight.

As the polypropylene resin (X2), among the above, block polypropylene (X2Y) is particularly preferable, and among the block polypropylene (X2Y), the intrinsic viscosity of the propylene-ethylene random copolymer component at 135° C. in decalin is 5 A block polypropylene (X2Y) having a ratio of 0.3 or more is more preferable.
When the intrinsic viscosity of the block polypropylene satisfies the above, the appearance of the multilayer foamed sheet tends to be good when the non-foamed layer is used as the surface layer.

2.3. Method for preparing polypropylene resin (X) The proportion of the polypropylene resin (X1) in the polypropylene resin composition (X) is 5 to 100% by weight (including 100% by weight) based on the polypropylene resin composition (X). It is necessary to do so, preferably 10 to 100% by weight, more preferably 15 to 100% by weight. As a result, a higher melt tension can be obtained as compared with a normal linear polypropylene resin, and by providing the resin composition as a non-foamed layer of a foamed sheet, it is possible to suppress corrugation during production. is there.
The range of the amount of the polypropylene resin (X2) based on the total amount of the polypropylene resin composition (X) is 0 to 95% by weight, preferably 0 to 90% by weight, more preferably 0 to 85% by weight. The polypropylene resin (X2) can control the fluidity of the non-foamed layer.

As a method for preparing the polypropylene resin composition (X), known methods can be used. For example, the polypropylene resin composition (X) can be prepared by mixing the polypropylene resins (X1) and (X2) and the optional components described below with a dry blend, a Henschel mixer, or the like. Further, these may be melt-kneaded by a single-screw extruder, a twin-screw kneader, a kneader or the like.
At this time, in order to use for extrusion molding, it is preferable that the resin composition is melt-kneaded and the resin composition is pelletized. As a method of pelletizing the resin composition,
a. A mixture of polypropylene resins (X1) and (X2) and any additive is melt-kneaded and pelletized.
b. A mixture of the polypropylene resin (X1) and any additive is melt-kneaded into pellets, and the polypropylene resin (X2) and any additive are further mixed with the pellets, and then melt-kneaded into pellets.
b'. A mixture of the polypropylene resin (X2) and any additive is melt-kneaded into pellets, and the polypropylene resin (X1) and any additive are further mixed with the pellets, and then melt-kneaded into pellets.
c. A mixture of polypropylene resin (X1) and any additive and a mixture of polypropylene resin (X2) and any additive were melt-kneaded to obtain respective pellets. Mix.
d. A mixture of polypropylene resin (X1) and any additive and a mixture of polypropylene resin (X2) and any additive were melt-kneaded to obtain respective pellets. Mix and further melt-knead and pelletize.
Such a method can be used.

  The preferred range of the melt flow rate (MFR) of the polypropylene resin composition (X) used in the present invention is 1.0 to 30 g/10 minutes, and the lower limit is more preferably 1.5/10 minutes or more, It is preferably 2.0/10 minutes or more, and the upper limit value is more preferably 20 g/10 minutes or less, further preferably 15 g/10 minutes or less. When the MFR is 1.0 g/10 minutes or more, it is possible to secure the fluidity of the molten resin. On the other hand, if it is 30 g/10 minutes or less, the melt tension of the molten resin is maintained, and the corrugate suppressing effect is easily obtained.

  Here, MFR is a value measured according to JIS K7210 at a heating temperature of 230° C. and a load of 21.2 N (2.16 kg).

  There are several ways to adjust the MFR. For example, the MFR of the polypropylene resin composition (X) can be adjusted by adjusting the MFR of the polypropylene resin (X1) or the polypropylene resin (X2). Further, when the polypropylene component in the block polypropylene (X2Y) and the propylene-ethylene random copolymer component have different MFRs, the MFR of the polypropylene resin composition (X) can be adjusted by changing the blending amount of both. For example, when the MFR of the polypropylene component is higher than the MFR of the propylene-ethylene random copolymer component, the higher the compounding amount of the polypropylene component, the higher the MFR of the polypropylene resin composition (X) via the polypropylene resin (X2). Become.

The polypropylene resin composition (X) preferably has a melt tension (MT) at 230° C. of 1.0 g or more as measured by a melt tension tester.
Here, MT is a Capillograph 1B manufactured by Toyo Seiki Seisaku-sho, Ltd., capillary: diameter 2.0 mm, length 40 mm, cylinder diameter: 9.55 mm, cylinder extrusion speed: 20 mm/min, take-up speed: 4.0 m. /Minute, temperature: The melt tension when measured under the conditions of 230°C, and the unit is gram. Regarding the upper limit of MT, it is not particularly necessary to provide it, but when MT is 40 g or less, fluidity is improved and surface roughness is easily suppressed. Therefore, it is preferably 40 g or less, more preferably 35 g or less, Most preferably, it is 30 g or less. When the melt tension is in the above range, the compatibility between the foamed layer and the non-foamed layer is improved, and when the multilayer sheet is formed, it is often possible to effectively suppress the interface roughness between the layers, and the corrugate suppressing effect is also easily obtained. ..
There are several ways to adjust MT within the above range. For example, MT of the polypropylene resins (X1) and (X2) may be changed, or the compounding ratio of the polypropylene resins (X1) and (X2) may be changed. Generally, the MT of the resin composition can be increased by increasing the content of the polypropylene component (X1) having a long chain branched structure with high melt tension.

3. Polypropylene resin (W)
The polypropylene resin (W) for the foam layer is not particularly limited, but one suitable for extrusion foaming is preferable, and for example, a polypropylene composition composed of two specific components described in JP-A-2013-100491. And linear polypropylene resins having a high melt tension as described in JP-A-2009-67948.
Examples of the polypropylene resin (W) for the foam layer include homopolypropylene, propylene-α-olefin random copolymer, block polypropylene and the like.

  The MFR of the polypropylene resin used for the foamed layer is preferably 1 to 20 g/10 minutes, more preferably 2 to 15 g/10 minutes.

4. Method for producing multi-layered foam sheet As a method for producing a multi-layered foam sheet, a resin and a foaming agent are kneaded using an extruder to which a circular die having a circular die exit shape is connected, and the melted resin extruded is subjected to a circular die. Circular foaming is applied in which a multilayer foamed sheet is obtained by drawing and cooling with a cooling mandrel having an outer diameter larger than the slit diameter, and then cutting open the tubular foam with a cutter or the like. For multi-layering, each resin for foaming layer and non-foaming layer is melted and kneaded with different extruders, and each layer is laminated with a multi-layer mandrel die, multi-stack die, multi-layer spider mandrel die, multi-layer spiral mandrel die, etc. It can be laminated.

  The type of foaming agent used is not particularly limited, and known foaming agents used for plastics, rubber and the like can be used. Further, any kind of a physical foaming agent, a decomposable foaming agent (chemical foaming agent), a microcapsule containing a thermal expansion agent, or the like, or a combination of a plurality of kinds may be used.

  Specific examples of the physical blowing agent, propane, butane, pentane, aliphatic hydrocarbons such as hexane, cyclopentane, alicyclic hydrocarbons such as cyclohexane, chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichloro. Difluoromethane, chloromethane, dichloromethane, chloroethane, dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, trichlorotrifluoroethane, dichlorotetrafluoroethane , Halogenated hydrocarbons such as chloropentafluoroethane and perfluorocyclobutane, inorganic gases such as water, carbon dioxide gas and nitrogen, and the like. These compounds may be used alone or in combination of a plurality of compounds.

  Of these, aliphatic hydrocarbons such as propane, butane, and pentane, and carbon dioxide gas are preferable because they are inexpensive and have high solubility in polypropylene resin. When carbon dioxide gas is used, it is more preferable to use supercritical conditions of 7.4 MPa or higher and 31° C. or higher because the state of excellent diffusion and solubility in the resin is achieved.

  Specific examples of the decomposable foaming agent (chemical foaming agent) include a mixture of sodium bicarbonate and an organic acid such as citric acid, an azo foaming agent such as azodicarbonamide, barium azodicarboxylate, N,N′-dinitrosopentamethylene. Nitroso-based foaming agents such as tetramine, N,N'-dimethyl-N,N'-dinitrosoterephthalamide, sulfohydrazide-based foaming agents such as p,p'-oxybisbenzenesulfonyl hydrazide and p-toluenesulfonyl semicarbazide, tri- Examples thereof include hydrazinotriazine. The blending amount of the foaming agent is preferably 0.05 to 10 parts by weight with respect to 100 parts by weight of the polypropylene resin (W) in the polypropylene resin composition for the foam layer.

  When using a physical foaming agent, a cell regulator may be used, if necessary. Examples of the bubble control agent include inorganic decomposable foaming agents such as ammonium carbonate, sodium bicarbonate, ammonium bicarbonate and ammonium nitrite, azo compounds such as azodicarbonamide, azobisisobutyronitrile and diazoaminobenzene, N,N'-. Nitroso compounds such as dinitrosopentane methylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide, benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, p,p'-oxybisbenzenesulfonyl semicarbazide, p- Degradable foaming agents such as toluenesulfonyl semicarbazide, trihydrazinotriazine, barium azodicarboxylate, etc., inorganic powders such as talc, silica, acidic salts such as polyvalent carboxylic acid, reaction of polyvalent carboxylic acid with sodium carbonate or sodium bicarbonate. A mixture etc. can be illustrated. These bubble regulators may be used alone or in combination of two or more.

When using the cell regulator, the content of the cell regulator may be in the range of 0.005 to 5 parts by weight based on 100 parts by weight of the polypropylene resin composition for the foam layer. preferable.
5. Optional Components Each layer of the foamed layer and the non-foamed layer may contain a polyethylene resin, an elastomer or the like as another thermoplastic resin as long as the effect of the present invention is not impaired.

  Further, the foamed layer of the multilayer foamed sheet of the present invention, each layer of the non-foamed layer, an antioxidant, a neutralizing agent, a light stabilizer, an ultraviolet absorber, an inorganic filler, an antiblocking agent, a lubricant, an antistatic agent, Various additives such as a metal deactivator, a coloring agent, a crystal nucleating agent, and a polymer that can be used for polypropylene can be added within a range that does not impair the object of the present invention. The compounding amount of these additives is generally 0.0001 to 3% by weight, preferably 0.001 to 1% by weight in 100% by weight of the polypropylene resin composition (X) or the polypropylene resin (W).

  Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants and sulfur antioxidants, and examples of neutralizing agents include higher fatty acid salts such as calcium stearate and zinc stearate. Examples of stabilizers and ultraviolet absorbers include hindered amines, nickel complex compounds, benzotriazoles, and benzophenones.

Hereinafter, typical compounds will be exemplified as the phenolic antioxidant.
The monophenol type compounds include 2,6-di-t-butyl-4-methylphenol (common name: BHT), tocopherol (vitamin E), n-octadecyl-3-(4'-hydroxy-3',5'. -Di-t-butylphenyl) propionate (trade name: Irganox 1076, Sumilizer BP-76) can be exemplified.

  Examples of the bisphenol type compound include 2,2′-methylenebis(4-methyl-6-t-butylphenol) (trade name: Sumilizer MDP-S), 1,1-bis(2′-methyl-4′-hydroxy-5). '-T-Butylphenyl)butane (trade name: Sumilizer BBM-S, ADEKA STAB AO-40), 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl) Examples include propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane (trade name: Sumilizer GA-80, Adeka Stab AO-80).

Examples of triphenol type compounds include 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane (trade name: Adeka Stab AO-30), 1,3,5-trimethyl-2. , 4,6-Tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (trade name: Irganox 1330, ADEKA STAB AO-330), Tris-(3,5-di-t-butyl-4-). Hydroxybenzyl)-isocyanurate (trade name: Irganox 3114, ADEKA STAB AO-20), 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate (trade name: Sumilizer) BP-179, Cyanox1790), and tris-(3,5-di-t-butyl-4-hydroxyphenyl)-isocyanurate (trade name: Cheminox 314) can be exemplified.
Examples of the tetraphenol type compound include tetrakis{methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate}methane (trade name: Irganox 1010).

Hereinafter, typical compounds will be exemplified as the phosphorus-based antioxidant.
Examples of the phosphite-type compound include tris(2,4-di-t-butylphenyl)phosphite (trade name: Irgafos168, Sumilizer P-16, Adekastab 2112), trisnonylphenyl phosphite (trade names: Sumilizer TNP, Adekastab). 1178), tris (mixed, mono-dinonylphenyl phosphite) (trade name: ADEKA STAB 329K), tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylenediphosphonite (common name: P-EPQ) and cyclic neopentanetetraylbis(2,6-di-t-butyl-4-methylphenylphosphite) (trade name: ADEKA STAB PEP-36) can be exemplified.

Hereinafter, typical compounds will be exemplified as the sulfur-based antioxidant.
Examples of the sulfide type compound include dilauryl-3,3′-thio-dipropionate (common name: DLTDP), di-myristyl-3,3′-thio-dipropionate (common name: DMTDP), distearyl-3,3′-thio- Examples include dipropionate (common name: DSTDP) and pentaerythritol-tetrakis-(3-laurylthio-propionate) (trade names: Sumilizer TP-D, Adeka Stab AO-412S).

Next, the ultraviolet absorber and the light stabilizer will be described.
The ultraviolet absorber is a compound having an absorption band in the ultraviolet region, and triazole-based, benzophenone-based, salicylate-based, cyanoacrylate-based, nickel chelate-based, inorganic fine particle-based, and the like are known. The most commonly used of these is the triazole type.
Hereinafter, typical compounds will be exemplified as the ultraviolet absorber.
Examples of the triazole-based compound include 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (trade name: Smithsorb 200, TinuvinP), 2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole. (Brand name: Sumisorb 340, Tinuvin 399), 2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole (Brand name: Sumisorb 320, Tinuvin 320), 2-(2′-hydroxy) -3',5'-di-t-amylphenyl)benzotriazole (trade name: Sumisorb 350, Tinuvin 328), 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5- An example is chlorobenzotriazole (trade name: Sumisorb 300, Tinuvin 326).
Examples of the benzophenone-based compound include 2-hydroxy-4-methoxybenzophenone (trade name: Smithsorb 110) and 2-hydroxy-4-n-octoxybenzophenone (trade name: Smithsorb 130).
Examples of salicylate compounds include 4-t-butylphenyl salicylate (trade name: Seesorb 202). Examples of the cyanoacrylate-based compound include ethyl (3,3-diphenyl)cyanoacrylate (trade name: Seesorb 501). Examples of the nickel chelate compound include nickel dibutyldithiocarbamate (trade name: Antigen NBC). Examples of the inorganic fine particle-based compound include TiO ₂ , ZnO ₂ , and CeO ₂ .

As the light stabilizer, a hindered amine-based compound is generally used, which is called HALS. HALS has a 2,2,6,6-tetramethylpiperidine skeleton and cannot absorb ultraviolet rays, but suppresses photodegradation due to various functions. It is said that its main functions are three: trapping radicals, decomposing hydroxyperoxide compounds, and trapping heavy metals that accelerate the decomposition of hydroxyperoxide.
Hereinafter, typical compounds will be exemplified as HALS.
Examples of sebacate-type compounds include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (trade name: ADEKA STAB LA-77, Tinuvin770), bis(1,2,2,6,6-pentamethyl- 4-piperidyl) sebacate (trade name: Tinuvin 765) can be exemplified.
In the butane tetracarboxylate type compound, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane tetracarboxylate (trade name: ADEKA STAB LA-57), tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate (trade name: ADEKA STAB LA-52), 1,2,3,4-butanetetra Condensation product of carboxylic acid with 2,2,6,6-tetramethyl-4-piperidinol and tridecyl alcohol (trade name: ADEKA STAB LA-67), 1,2,3,4-butanetetracarboxylic acid and 1, A condensate with 2,2,6,6-pentamethyl-4-piperidinol and tridecyl alcohol (trade name: ADEKA STAB LA-62) can be exemplified.
Examples of the succinic acid polyester type compound include a condensation polymer of succinic acid and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine.
Examples of triazine-type compounds include N,N′-bis(3-aminopropyl)ethylenediamine·2,4-bis{N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino. }-6-Chloro-1,3,5-triazine condensate (trade name: Chimassorb 199), poly{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2 ,4-Diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl)imino} (trade name: Chimassorb 944 ), poly(6-morpholino-s-triazine-2,4-diyl){(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetra Methyl-4-piperidyl)imino} (trade name: Chimasorb 3346) can be exemplified.

  Further, examples of the inorganic filler include calcium carbonate, silica, hydrotalcite, zeolite, aluminum silicate, magnesium silicate and the like. The blending amount of the inorganic filler can be about 50 parts by weight or less. Examples of the lubricant include higher fatty acid amides such as stearic acid amide.

  Further, examples of the antistatic agent include fatty acid partial esters such as glycerin fatty acid monoester, and examples of the metal deactivator include triazines, phosphones, epoxies, triazoles, hydrazides, oxamides and the like. it can.

Lubricants are additives used to improve moldability and fluidity, and have the function of reducing the frictional force between polymer molecules and the frictional force between the polymer and the inner wall of the molding machine in a molding machine or extruder. .. Compounds used as lubricants include hydrocarbon compounds such as paraffin and wax, alcohols such as stearyl alcohol and propylene glycol, higher fatty acid esters such as n-butyl stearate, higher fatty acid amides such as oleic acid amide and stearic acid amide, and stearates. Examples include higher fatty acid salts such as calcium phosphate, partial esters of polyhydric alcohols such as stearic acid monoglyceride, and silicone oil.
Of these, specific examples of higher fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, and behenic acid amide. The fatty acid amide compound may have a substituent on the alkyl chain or N. Examples of the fatty acid amide compound having a substituent include hydroxystearic acid amide, N-oleylpalmitic acid amide, N-stearyl oleic acid amide, N-stearyl erucic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, Can be mentioned.

Hereinafter, typical compounds will be exemplified as the neutralizing agent.
Examples of the carboxylate type compound include calcium stearate and zinc stearate. Examples of the inorganic compound include hydrotalcite, and inclusions of aluminum hydroxide and lithium carbonate (trade name: Mizucarac).

6. Manufacture of Molded Article The multilayer foamed sheet of the present invention can be used for thermoforming. Thermoforming as used herein generally means that a plastic sheet is heated and softened and pressed into a desired mold for molding, and the air in the gap between the mold and the material is eliminated and the mold is brought into close contact with the mold by atmospheric pressure. There are vacuum forming, compressed air forming using compressed air at atmospheric pressure or higher, vacuum pressure forming using both vacuum and compressed air.
The thermoforming method is not particularly limited, and examples thereof include plug molding, matched mold molding, and plug assist molding.
Further, a cup-shaped molded body can be obtained by using a molding method that is generally used for manufacturing paper cups and the like. The molding method that is generally used in the production of paper cups and the like here is to prepare a body member punched in a fan shape and a bottom member punched in a circular shape, respectively, and roll a round body in the peripheral portion of the bottom member. In this method, the lower end of the part is wound and heat-fused to form a cup.

7. The molded product obtained above is a foam food container such as trays, cups, plates and cups that can be heated by a microwave oven or filled with high-temperature liquid, automobile door trims, vehicle interior materials such as automobile trunk mats, building materials, Suitable for heat insulating materials, packaging, stationery, etc.

  Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[Evaluation methods]
In the examples and comparative examples, various properties of the polypropylene resin composition, the multilayer foamed sheet, and the components thereof were measured and evaluated according to the following evaluation methods.

(1) Multilayer Foamed Sheet Density A test piece was cut out from the polypropylene (multilayer) foamed sheets obtained in Examples and Comparative Examples, and the weight (g) of the test piece was calculated from the external dimensions of the test piece (cm ^{3 ).} ) Divided by. The density was determined by measurement according to JIS K7222.

(2) Corrugation Evaluation of Multilayer Foamed Sheet Corrugation evaluation during production was visually evaluated according to the following criteria during production of the polypropylene-based resin composition foamed sheet obtained in each of Examples and Comparative Examples.
⊚: No corrugate is observed at the exit of the die.
○: A corrugate is confirmed at the die exit, but the corrugate has no effect after the cooling mandrel.
Δ: A corrugate was confirmed at the exit of the die, and the influence of the corrugate was locally recognized even after the cooling mandrel.
X: Corrugations at the die exit are remarkable, and corrugates are widely affected even after the cooling mandrel.

(3) Appearance Evaluation of Multilayer Foamed Sheet For the surface appearance evaluation of the foamed sheet, the polypropylene-based resin composition foamed sheets obtained in each Example and each Comparative Example were visually evaluated according to the following criteria.
A: The surface of the foamed sheet is smooth with no visible irregularities.
◯: The surface of the foamed sheet is smooth, although irregularities are visually recognized.
X: Concavities and convexities due to air bubbles are confirmed on the surface of the foamed sheet, and roughness is noticeable.

[Materials used]
The following polypropylene resins PP-1 to PP-7 were used.

PP-1 and PP-2
WAYMAX MFX3 and WAYMAX MFX6 manufactured by Japan Polypro Co., Ltd. were used as polypropylene PP-1 and PP-2 having a long-chain branched structure. Table 1 shows the results of analysis of PP-1 and PP-2. ^{From the} results of ¹³ C-NMR measurement and branching index g′ measurement, it was confirmed that this polypropylene had long chain branches.

PP-3
As PP-3, block polypropylene (MFR=1.5 g/cm 3, MT=3.5 g) manufactured by Nippon Polypro Co., Ltd. was used.
The results of analysis of PP-3 are shown in Table-2.
PP-4
As PP-4, a block polypropylene (MFR=2.6 g/cm3, MT=2.9 g) manufactured by Nippon Polypro Ltd. was used.
The results of analysis of PP-4 are shown in Table-2.

PP-5
As the block polypropylene PP-5, BC3BRF manufactured by Japan Polypro Co., Ltd. was used.
The results of analysis of the block polypropylene PP-5 are shown in Table 2.
PP-6
As the block polypropylene PP-6, FTS 3000 manufactured by Japan Polypro Co., Ltd. was used.
Table 2 shows the results of analysis of the block polypropylene PP-6.
PP-7
MA1B manufactured by Nippon Polypro Co., Ltd. was used as the homopolypropylene PP-7.
The results of analysis of homopolypropylene PP-7 are shown in Table 2.
From the results of ¹³ C-NMR and branching index g′, it was confirmed that PP-3 to PP-7 do not have a long-chain branched structure.

Polypropylene resin composition (X-1, X-2, X-3)
70 parts by weight of polypropylene (PP-1) and 30 parts by weight of block polypropylene (PP-3) were dry blended and melt-kneaded with a twin-screw extruder to obtain a polypropylene resin composition (X-1). Further, 70 parts by weight of polypropylene (PP-2) and 30 parts by weight of block polypropylene (PP-4) were dry blended to obtain a polypropylene resin composition (X-2). Further, 70 parts by weight of polypropylene (PP-7) and 30 parts by weight of block polypropylene (PP-4) were dry blended to obtain a polypropylene resin composition (X-3). Table 3 shows the evaluation results of MFR and MT of the polypropylene resin compositions (X-1, X-2 and X-3).

[Example 1]
1) Raw materials used The following materials were used as the polypropylene resin composition for the foamed layer, the cell regulator, and the polypropylene resin composition for the non-foamed layer.
Block polypropylene PP-5 as the polypropylene resin (W) contained in the polypropylene resin composition for the foam layer
・Polypropylene resin composition (X-1) as polypropylene resin composition for non-foaming layer
-Bubble regulator: 0.5 part by weight of a chemical foaming agent to 100 parts by weight of PP-5 (trade name: Hydrocerol CF40E-J, manufactured by Nippon Boehringer Ingelheim Co., Ltd.)
2) Production of Multilayer Foam Sheet by Circular Extrusion Foam A multilayer foam sheet was produced as follows.
2-1) In order to produce a multilayer foamed sheet, the polypropylene resin composition for a foamed layer is charged into a raw material supply hopper of a tandem extruder having screw diameters of 40 mmΦ and 50 mmΦ for the first and second extruders, respectively. did. With the cylinder set temperature of the first-stage extruder set at 230° C., the resin was heated and melted to be plasticized and the bubble control agent was decomposed, butane gas was injected at 0.35 kg/h and mixed using a gas injection pump. Then, the second stage extruder was quickly cooled to a preset temperature of 165° C., and the propylene resin composition for foam layer was cooled to a preset temperature of 165° C. with a circular die attached to the tip of the extruder (caliber= 55 mmΦ, gap=0.75 mm) was extruded into the atmosphere to foam. Regarding the polypropylene resin composition (X-1) for the non-foamed layer, after the polypropylene resin (X-1) was heated and melted by introducing it into the raw material supply hopper of an extruder having a diameter of 30 mmΦ and setting the cylinder temperature to 190°C. Was laminated on the inside of the foam layer with a multilayer spiral mandrel, and co-extruded together with the foam layer from the tip of the circular die to produce a laminated foam. The total extrusion rate of the composition for the foamed layer and the composition for the non-foamed layer was 15 kg/h.
2-2) The foam was cooled by passing through a cooling mandrel having an outer diameter of 120 mmΦ, and subsequently cut open by a rotor cutter into a sheet, and the sheet was wound by a take-up roll, a pinch roll and a take-up roll. The sheet thickness was adjusted by the speed of the take-up roll.
The obtained foamed sheet had a foamed layer density of 0.196 g/cm ³ and had a good appearance. Table 4 shows the evaluation results of the foamed sheet.

[Examples 2 to 3]
A multilayer foam sheet was produced in the same manner as in Example 1 except that the non-foam layer was placed outside the foam layer (Example 2) or on both sides (Example 3).
When arranging the non-foamed layer on the outside of the foamed layer, an extruder having the same diameter as the extruder used for laminating the non-foamed layer on the inside is used, and the polypropylene resin composition for the non-foamed layer is put into the raw material supply hopper, The polypropylene resin composition for a non-foaming layer was heated and melted at a cylinder setting temperature of 190° C., then laminated on the outside of the foam layer with a multilayer spiral mandrel, and co-extruded together with the foam layer from the tip of a circular die to produce a laminated foam.
When laminating the non-foamed layer on both sides of the foamed layer, a laminated foam was produced by activating both the extruders used for laminating inside and outside.
The obtained foamed sheet had a foamed layer having a density of 0.136 to 0.180 g/cm ³ and had a good appearance. Table 4 shows the evaluation results of the foamed sheet.

[Example 4]
Circular extrusion foaming was carried out in the same manner as in Example 3 except that block polypropylene (PP-6) was used instead of block polypropylene (PP-5) for the foam layer, and various multilayer foam sheets were obtained. The obtained foamed sheet had a foamed layer density of 0.164 g/cm ³ , did not generate corrugations during the production, and had a very beautiful appearance. Table 4 shows the evaluation results of the foamed sheet.
[Example 5]
Circular extrusion foaming was performed in the same manner as in Example 3 except that the non-foamed layer was the polypropylene resin composition X-2, and various multilayer foamed sheets were obtained. The obtained foamed sheet had a foamed layer density of 0.185 g/cm ³ , did not generate corrugations at all during the production, and had a very beautiful appearance. Table 4 shows the evaluation results of the foamed sheet.

[Comparative Example 1]
The single-layer foam sheet was produced in Example 1 without starting the extruder for the non-foam layer. Other conditions are the same as in Example 1. In the obtained foamed sheet, the density of the foamed layer was 0.205 g/cm ³ , corrugations were remarkably generated during the production, many irregularities were formed, and the appearance was impaired. Table 5 shows the evaluation results of the foamed sheet.

[Comparative Examples 2-3]
Various multilayer foamed sheets were obtained in the same manner as in Examples 2 to 3 except that block polypropylene (PP-5) having no long chain branch structure was laminated as a non-foamed layer by coextrusion. The obtained multilayer foamed sheet had a foamed layer density of 0.203 g/cm ³ , corrugates were remarkably generated during the production, many irregularities were formed, and the appearance was impaired. Table 5 shows the evaluation results of the foamed sheet.

[Comparative Example 4]
As the resin for the non-foamed layer, homopolypropylene PP-7 having no long chain branch was used instead of PP-2 having long chain branch used in Example 5, except that it was used as a mixture with PP-4. A multilayer foamed sheet was obtained in the same manner as in Example 5. The obtained foamed sheet had a density of the foamed layer of 0.209 g/cm ³ , corrugates were confirmed during production, and the appearance was inferior to that of the example. Table 5 shows the evaluation results of the foamed sheet.

  By comparison between Examples and Comparative Examples, when the polypropylene resin composition (X1-1 and X1-2) containing the polypropylene resin (PP-1 and PP-2) having a long-chain branched structure is provided as a non-foaming layer. It is clear that the occurrence of corrugations is remarkably suppressed, and a multi-layer foamed sheet having a good sheet surface appearance and a high sheet thickness uniformity even when the foaming ratio is high or the thickness is increased.

  The polypropylene multilayer foamed sheet obtained by co-extruding the polypropylene resin composition for a non-foamed layer of the present invention, and a thermoformed body using the multilayer foamed sheet have excellent surface appearance because corrugates during production are suppressed. The expansion ratio is high. In addition, the obtained sheet is excellent in thermoformability, impact resistance, lightness, rigidity, heat resistance, heat insulation, oil resistance, etc., so it can be heated by a microwave oven and filled with high temperature liquid. It can be suitably used in a wide range of fields such as foamed food containers such as trays, plates and cups, automobile door trims, vehicle interior materials such as automobile trunk mats, building materials, heat insulating materials, packaging and stationery, and has an extremely high industrial value.

Claims (5)

Polypropylene resin comprising 5 to 100% by weight of a polypropylene resin (X1) having a long chain branch structure obtained by using a macromer copolymerization method and 0 to 95% by weight of a polypropylene resin (X2) having no long chain branch structure. A non-foamed layer containing the composition (X) (however, the total amount of the polypropylene resin (X1) and the polypropylene resin (X2) is 100% by weight);
Made of polypropylene-based resin (W), see contains an expansion ratio of 4.0 or more foam layers, the polypropylene resin (X1), branching index absolute molecular weight Mabs are in 1,000,000 g 'of 0.75 or more 0.96 The following is a multilayer foam sheet.   The multilayer foamed sheet according to claim 1, wherein the polypropylene resin (W) is a polypropylene resin having no long-chain branched structure.   A multi-layer foam molded article comprising the multi-layer foam sheet according to claim 1. Have a long chain branched structure obtained by using a macromer copolymerization method, and the absolute molecular weight Mabs 1,000,000 in branching index g 'of 0.75 or more 0.96 or less der Ru polypropylene resin (X1) 5 to 100 And a polypropylene resin (X2) having no long chain branched structure in an amount of 0 to 95% by weight (provided that the total amount of the polypropylene resin (X1) and the polypropylene resin (X2) is 100% by weight) and a resin composition for a non-foamed layer,
A resin composition for a foam layer containing a polypropylene resin (W) and a foaming agent,
A method for producing a multilayer foam sheet, which comprises co-extruding from a circular die.   The method for producing a multilayer foam sheet according to claim 4, wherein the polypropylene resin (W) is a polypropylene resin having no long-chain branched structure.