JP2017144597A - Multilayer foam sheet having a non-foamed layer comprising a long chain branched polypropylene resin composition - Google Patents

Abstract

The present invention provides a multi-layer foamed sheet that can suppress corrugation generated during the production of circular extrusion foaming using a polypropylene resin composition, has a high foaming ratio, and is excellent in surface appearance.
A polypropylene resin composition for a non-foamed layer comprising 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) having no long chain branched structure. Product (X) (however, the total amount of polypropylene resin (X1) and polypropylene resin (X2) is 100% by weight), polypropylene resin (W) and a polypropylene resin composition for a foam layer containing a foaming agent Are coextruded from a circular die to produce a multilayer foamed sheet.
[Selection figure] None

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-foamed layer containing a specific polypropylene resin composition, and the polypropylene resin composition. The present invention relates to a multilayer foam sheet having a non-foamed layer, and a molded body obtained by molding the multilayer foam sheet.

  Foamed sheets obtained by extrusion foaming of polypropylene resins are lightweight and excellent in heat resistance, impact resistance, chemical resistance, etc., so they can be used in a wide range of applications such as building materials, stationery, automobile interior materials and food containers. Expected. Such a foam sheet is foamed by adding various foaming agents to a polypropylene resin composition melted in an extruder, kneading under pressure, and extruding it under atmospheric pressure from a die attached to the tip of the extruder. It is obtained by taking out the molten resin that has been spread, cooled and solidified. At this time, from the viewpoint of reducing the environmental load, further improvement in lightness and heat insulation, that is, improvement in the expansion ratio is important.

  In extrusion foam molding of a polypropylene resin, a T die or a circular die is generally used. From the viewpoint that it is effective to improve a foaming ratio to draw a molten resin while foaming 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 was stretched and cooled by a cooling mandrel having an outer diameter larger than the annular slit diameter, and passed through the cooling mandrel. A foam sheet is manufactured by cutting a cylindrical foam using a cutter or the like.

  In the circular foam molding, as the expansion ratio increases, a so-called corrugated phenomenon that the molten resin undulates in the circumferential direction of the die becomes a problem. The corrugation is considered to occur when the volume expansion of the molten resin accompanying foaming in the circumferential direction exceeds the expansion by the mandrel. In addition, volume expansion becomes large, so that the amount of foaming agents to introduce | transduce (the target expansion ratio is high). In addition, the corrugation problem occurs even when the thickness of the foam sheet is increased by reducing the take-up speed.

  Here, in order to suppress the corrugation, a method of increasing the viscosity of the resin at the time of molding by suppressing the molding temperature or lowering the melt flow rate (MFR) of the resin and suppressing the rate of volume expansion can be considered. . However, when the amount of the foaming agent is large, the viscosity of the resin due to the foaming agent is remarkably lowered, and the amount of the foaming agent is increased, and the volume expansion rate is further increased. It is very difficult to control the volume expansion by this method.

  In order to suppress the corrugation, 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, even if the blow-up ratio is increased, the corrugation itself is not suppressed, and it is only difficult to notice by extending the corrugate. The thickness of the sheet becomes uneven, and as the blow-up ratio increases, the foam sheet strongly hits the mandrel, so that the expansion ratio is deteriorated and the appearance is liable to be deteriorated.

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

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

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

  In Patent Document 2, in order to suppress corrugation during circular foam molding, a foam sheet having a thickness smaller than the intended purpose is manufactured in advance, and then a non-foamed resin layer having a thickness of 10 to 200 μm is provided between the foam sheets. A method for producing a polypropylene resin composition multilayer foamed sheet having a thickness of 3 to 10 mm by an extrusion laminating method is proposed. This proposal also has a problem that the process is complicated because a method of increasing the thickness by laminating a plurality of thin foam sheets is used.

JP-A-7-227930 JP2009-274416

  In view of such circumstances, an object of the present invention is to suppress corrugation during production, obtain a foam sheet with a smooth surface and a high expansion ratio in circular foam molding.

The present inventors have conducted intensive research on the suppression of corrugation, and in order to suppress the volume expansion due to foaming from the die outlet from proceeding in the circumferential direction, a resin composition containing polypropylene having a long-chain branched structure is not used. By providing as a foam layer, it discovered that generation | occurrence | production of corrugation was remarkably improved and it came to this invention.
That is, the 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 (viscosity increase due to strain) during volume expansion due to foaming. And found that corrugation can be suppressed.
In addition, by providing a specific non-foamed layer to suppress corrugation, gas escape is also suppressed, so the expansion ratio is improved. When this is used as a surface layer, the surface smoothness is improved. Can also be obtained.

That is, the present invention includes the following.
[1] Polypropylene resin composition (X) comprising 5 to 100% by weight of polypropylene resin (X1) having a long chain branched structure and 0 to 95% by weight of polypropylene resin (X2) having no 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 foamed sheet comprising a polypropylene resin (W) and a foamed layer having a foaming 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) comprising 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) having no long chain branched structure ( Provided that the total amount of the polypropylene resin (X1) and the polypropylene resin (X2) is 100% by weight.)
A resin composition for a foam layer containing a polypropylene resin (W) and a foaming agent;
A method for producing a multilayer foamed sheet, characterized by co-extrusion 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 branched structure.

In multilayer foaming with a non-foamed layer using the polypropylene resin composition of the present invention, corrugation during molding is greatly suppressed, there is no uneven thickness or foamed state in the circumferential direction, and multilayer foam with excellent smoothness. In addition, a sheet can be obtained, and gas expansion is suppressed, so that the expansion ratio is easily improved.
The molded body is excellent in impact resistance, lightness, rigidity, heat resistance, heat insulation, oil resistance, etc., so that it can be used for heating with a microwave oven or filling hot liquids such as hot beverages, It can be suitably used for food containers such as dishes and cups, vehicle interior materials such as automobile door trims and automobile trunk mats, building materials, packaging, and stationery.

  The present invention will be described in detail below.

1. Multilayer foam sheet The multilayer foam sheet of this invention is demonstrated below.
The multilayer foamed sheet of the present invention comprises 5 to 100% by weight (including 100% by weight) of polypropylene resin (X1) having a long chain branched structure and 0 to 95% by weight of polypropylene resin (X2) having no long chain branched structure. % Of a non-foamed layer comprising a polypropylene resin composition (X) (where the total amount of the polypropylene resin (X1) and the polypropylene resin (X2) is 100% by weight), and the polypropylene resin (W) And a foaming layer having a foaming ratio of 4.0 or more. That is, in the multilayer foamed sheet of the present invention, the polypropylene resin composition (W) is a foam layer and the polypropylene resin composition (X) is a non-foam layer.

  Examples of the layer configuration include two types and two layers of non-foamed layer / foamed layer and two types and three layers such as non-foamed layer / foamed layer / non-foamed layer, but in addition, the effect of the present invention is not impaired. As long as there are three types and three layers such as non-foamed layer / foamed layer / other resin layer, and three types and five layers such as non-foamed layer / foamed layer / other resin layer / foamed layer / non-foamed layer A plurality of layers may be included with the resin layer interposed therebetween. For example, a layer having a necessary function according to the purpose such as a gas barrier layer and an impact resistance imparting layer can be provided.

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

  A printed layer, a decorative layer, and the like can be provided outside the non-foamed layer 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, polypropylene resin (X1) having a long chain branched structure (5 to 100% by weight (including 100% by weight)) and polypropylene resin (X2) having no long chain branched structure (0 to 95% by weight) A non-foamed layer resin composition comprising the polypropylene resin composition (X) (where 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 resin composition containing a foaming agent are coextruded from a circular die to produce a multilayer foam sheet. A multilayer foamed sheet comprising a non-foamed layer based on the polypropylene resin composition (X) and a foamed layer made of the polypropylene resin (W) having a foaming ratio of 4.0 or more is preferable.

  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, the strength and physical properties are excellent in practical use, and defects such as bending and folding of the multilayer foam sheet are difficult to occur during molding.

  About the lamination | stacking location of a non-foaming layer, it can laminate | stack on the inner side (side which contacts a cooling mandrel) and the outer side of a foaming layer, or both sides. Moreover, there is no restriction | limiting in the form of arrangement | positioning of a non-foaming layer, such as providing a barrier layer and an adhesive layer in addition to this non-foaming layer. However, in any case, at least one or more layers based on the polypropylene resin composition for non-foamed layer (X) shown in the present invention must be laminated. Although the corrugation suppressing effect can be obtained in both cases of the foam layer inside and outside, at this time, the layer based on the polypropylene resin composition (X) for non-foam layer 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 corrugation suppressing effect can be obtained, which is preferable.

  In addition, the multilayer foam sheet of the present invention may be subjected to surface treatment such as corona discharge treatment, flame treatment, or plasma treatment on the surface of the foam sheet for further improvement in printability and paintability. There is no problem.

  The thickness of the non-foamed layer is desirably 0.1 to 50%, preferably 0.1 to 20% of the total thickness of the resulting polypropylene-based multilayer foamed sheet. When the thickness of the non-foamed layer is within this range, a high corrugate suppression effect can be obtained even when the sheet is thick, or the amount of the introduced foaming agent is large, and the corrugate tends to become prominent during production, and Since the bubble growth of the foamed layer is not hindered, a high foaming ratio is achieved, and the lightweight property of the multilayer foamed sheet can be maintained.

2. Polypropylene resin composition (X)
The multilayer foamed sheet in the present invention needs to have 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 due to foaming of the molten resin discharged from the die. It is necessary to contain 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 a polypropylene resin (X2) that does not have 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. In the case of a propylene copolymer, the comonomer is at least one olefin selected from the group consisting of ethylene and an α-olefin 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 of its high heat resistance and rigidity.

  Polypropylene resin (X1) is a component necessary for suppressing corrugation due to high melt tension, and must have long-chain branching. The long chain branching in the present invention refers to a branched structure of molecular chains having several tens or more of main chain carbon atoms and several hundreds or more in molecular weight in order to express high melt tension and strain hardening, 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 an organic peroxide (Japanese Patent Publication No. 2001-524565), or a specific method A method of producing a macromonomer having a terminal unsaturated bond using a metallocene catalyst having the structure of (2) and forming a long chain branch by copolymerizing it with propylene (Japanese Patent Publication No. 2001-525460), Whichever method is used, the melt tension of the polypropylene resin can be greatly improved.

  The polypropylene resin (X1) having a long chain branch structure is not particularly limited as long as it has a long chain branch structure, but has a comb chain structure and a long chain branch structure is formed during polymerization. A method using a macromer copolymerization method is preferred. Examples of such a method include, for example, JP-T-2001-525460, JP-A-10-338717, JP-A-2002-523575, JP-A-2009-57542, JP-A-05027353, Examples include the method disclosed in Kaihei 10-338717. In particular, the macromer copolymerization method disclosed in Japanese Patent Application Laid-Open No. 2009-57542 is suitable for the present invention because it does not generate gel and can obtain a long-chain branched polypropylene resin.

Having long-chain branching in polypropylene is defined by a method based on the rheological properties of the resin, a method for calculating a branching index g ′ using the relationship between molecular weight and viscosity, a method using ¹³ C-NMR, and the like. In the present invention, a 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. There is a detailed description in “Developments in Polymer Characterization-4” (JV Dawkins ed. Applied Science Publishers, 1983). 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 a 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 ′ takes a value smaller than 1, it is determined that a long chain branching structure exists, and the value of the branching index g ′ decreases as the long chain branching structure increases. .

The branching index g ′ can be obtained as a function of the absolute molecular weight Mabs by using GPC with a light scatterometer and viscometer in the detector. The method for measuring the branching index g ′ in the present invention is described in detail in JP-A-2015-40213, and is as follows.
[Measuring method]
GPC: Alliance GPCV2000 (Waters)
Detector: Described in the order of connection Multi-angle laser light scattering detector (MALLS): DAWN-E (Wyatt Technology)
Differential refractometer (RI): attached to GPC Viscometer (Viscometer): attached to GPC 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 Corporation GMHHR-H (S) Two HT connections Sample injection part temperature: 140 ° C.
Column temperature: 140 ° C
Detector temperature: 140 ° C for all
Sample concentration: 1 mg / mL
Injection volume (sample loop volume): 0.2175 mL

[analysis method]
When calculating the absolute molecular weight (Mabs) obtained from the multi-angle laser light scattering detector (MALLS), the root mean square radius of inertia (Rg), and the intrinsic viscosity ([η]) obtained from the Viscometer, data processing attached to MALLS Calculation is performed using the software ASTRA (version 4.73.04) with reference to the following document.
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, it is preferable to use a material that does not contain a gel because the appearance deteriorates if the polypropylene resin contains a gel. The above-mentioned polypropylene resin (X1) having a long-chain branched structure is prepared by producing a macromonomer having a terminal unsaturated bond using a metallocene catalyst having a specific structure and copolymerizing it with propylene. What was manufactured using the method of forming is preferable. In particular, those having a branching index g ′ satisfying 0.3 or more and less than 1.0 when the absolute molecular weight Mabs is 1 million described below are preferable, more preferably 0.55 or more and 0.98 or less, and still more preferably 0.8. It is 75 or more and 0.96 or less, and most preferably 0.78 or more and 0.95 or less. When the branching index g ′ is within this range, a highly crosslinked component is not formed, and no gel is generated or very little. Therefore, a non-foamed layer containing a polypropylene resin (X1) is particularly 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. Detailed descriptions are given in 204 and 1738 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 carbon adjacent to the branched carbon, Cbr represents the methine carbon at the root 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 Cbr described in the structural formula (1) in itself.

Such a branched structure is identified by ¹³ C-NMR analysis. The assignment of each peak is described in Macromolecules, Vol. 35, no. 10. The description of 2002, pages 3839-3842 can be referred to. That is, a total of three methylene carbons (Ca, Cb, Cc) were observed, each at 43.9-44.1 ppm, 44.5-44.7 ppm, and 44.7-44.9 ppm. 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).
It is characterized in that three methylene carbons adjacent to the branched methine carbon Cbr are observed in three non-equivalent diastereotopics.

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 this and a branch having 4 or less carbon atoms are branched. Since the carbon peak positions can be distinguished from each other, in the present invention, the presence or absence of a long-chain branched structure can be determined by confirming the peak of the branched methine carbon.
In addition, about the measuring method of ¹³ C-NMR in this invention, although the detail is described in the patent 4553966, it 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 of 470 mg was completely dissolved in 2.6 ml of deuterated 1,1,2,2-tetrachloroethane in an NMR sample tube (10φ), and then heated at 120 ° C. and then measured. The chemical shift was set to 74.2 ppm in the middle of the three peaks of deuterated 1,1,2,2-tetrachloroethane. The chemical shift of other carbon peaks is based on this.
Device name: Varian Unity Inova
Flip angle: 90 degrees Pulse repetition time: 15.0 seconds Resonance frequency: 125.7 MHz
Integration count: 14,400 times

[Melting tension MT]
In order to sufficiently exhibit the corrugating suppression effect 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 a resin having a high melt tension is disposed in the non-foamed layer, the volume expansion rate of the foamed layer can be suppressed during the foaming process, so that the effect of suppressing corrugation generated 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 Seisakusho Co., Ltd.
Capillary: 2.0mm diameter, 40mm length
Cylinder diameter: 9.55mm
Cylinder extrusion speed: 20 mm / min Take-up speed: 4.0 m / min (however, if MT is too high and the resin breaks, the take-up speed is lowered and the maximum take-up speed is measured.)
Temperature: 230 ° C

About the minimum of MT of polypropylene resin (X1) concerning the present invention, it is preferred that MT is 3 g or more. About the upper limit of MT, it is preferable that MT is 20 g or less, More preferably, MT is 18 g or less.
Specific methods for controlling the MT within the above range include adjusting the MFR, adjusting the catalyst production method (particularly, the complex loading ratio), performing electron beam irradiation, or performing a granulation process. There is a method of changing the number of long chain branches by adding an oxide or the like. Increasing the number of long chain branches or lowering MFR increases MT. On the other hand, in order to lower MT, it is only necessary to adjust in the reverse direction.

The MFR of the polypropylene resin (X1) according to the present invention is preferably more than 0.5 g / 10 minutes and not more than 20 g / 10 minutes.
MFR in the present invention is A method, 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 a 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 min or more, more preferably 2 g / 10 min or more. The upper limit of MFR is preferably 17 g / 10 min or less, more preferably 15 g / 10 min or less, still more preferably 13 g / 10 min or less, and most preferably 10 g / 10 min or less.
As a specific method for adjusting the MFR to the above range, a method of changing the amount of hydrogen added during polymerization can be mentioned. Since hydrogen acts as a chain transfer agent in the polymerization of propylene, if the amount of hydrogen added is increased, the MFR increases. Conversely, if the amount added is decreased, the MFR can be decreased. The value of MFR relative to the hydrogen concentration inside the polymerization tank varies depending on the catalyst used and other polymerization conditions, but the relationship between the hydrogen concentration and MFR is determined in advance according to the catalyst type and other polymerization conditions, and the desired MFR value is determined. It is very easy for those skilled in the art to adjust the hydrogen concentration so as to obtain a value.

  The 25 ° C. xylene-soluble component amount (CXS) of the polypropylene resin (X1) according to the present invention is preferably 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 crystallinity polymer component. When this component is large, the content of the low crystallinity polymer component in the polypropylene resin (X1) is high, and it is easy to generate an eye during molding. . Moreover, when the layer which consists of polypropylene resin (X1) comprises the surface, the problem that the sheet | seat surface is easy to stick arises. 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 BHT) at 130 ° C. to make a solution, and then left at 25 ° C. for 12 hours. Thereafter, the precipitated polymer is separated by filtration, p-xylene is evaporated from the filtrate, and further dried under reduced pressure at 100 ° C. for 12 hours to recover a 25 ° C. xylene-soluble component. The ratio [wt%] of the weight of the recovered component to the charged sample weight is defined as CXS.

The CXS of the polypropylene resin (X1) according to the present invention is preferably less than 5% by weight. 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. Although there is no restriction | limiting in particular about the lower limit of CXS, Preferably it is 0.01 weight% or more, More preferably, it is 0.05 weight% or more.
As a specific method for adjusting CXS to the above range, a catalyst can be selected. The most important factor for determining CXS of polypropylene having a long chain branch is a catalyst, and a catalyst satisfying CXS may be selected from known catalysts.

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

2.2. Polypropylene resin without long chain branching structure (X2)
The type of polypropylene resin (X2) is not particularly limited as long as it does not have a long-chain branched structure, and linear homopolypropylene that does not contain a long-chain branched structure, propylene-α- Any of an olefin random copolymer, a 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), propylene-ethylene random copolymer (X2C) is a homopolymer of propylene or a random copolymer of propylene and less than about 10% by weight of ethylene, and homopolypropylene (X2H), propylene- The ethylene random copolymer (X2C) may contain, for example, 3% by weight or less of at least one olefin selected from the group consisting of α-olefins having 4 to 10 carbon atoms as a comonomer.
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.
The comonomer content is usually controlled by appropriately adjusting the amount ratio of the monomer supplied to the polymerization tank (eg, the amount ratio of ethylene to propylene). The copolymerization characteristics of the catalyst to be used may be examined in advance, and the monomer feed ratio may be adjusted so that the gas composition in the polymerization tank has a value corresponding to the desired comonomer content.

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

  The propylene-ethylene random copolymer component is a copolymer of propylene and ethylene, but may be copolymerized with 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 135 ° C. decalin.
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, still more preferably. Is 13 dl / g or less, most preferably 11 dl / g or less.
As a specific method for adjusting the intrinsic viscosity of the propylene-ethylene random copolymer component, there can be mentioned a method of changing the hydrogen concentration during polymerization.

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, still more preferably 8% by weight or more, and most preferably 10% by weight or more. Preferably 45% by weight or less, more preferably 40% by weight or less, still more 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. Among the block polypropylene (X2Y), the propylene-ethylene random copolymer component has an intrinsic viscosity of 5 in decalin at 135 ° C. More preferably, the block polypropylene (X2Y) is 3 or more.
When the intrinsic viscosity of the block polypropylene satisfies the above, when the non-foamed layer is used as the surface layer, the appearance of the multilayer foamed sheet tends to be good.

2.3. Preparation method of polypropylene resin (X) The ratio of the polypropylene resin (X1) in the polypropylene resin composition (X) is 5 to 100 wt% (including 100 wt%) with respect to the polypropylene resin composition (X). Preferably 10 to 100% by weight, more preferably 15 to 100% by weight. This makes it possible to obtain a higher melt tension than ordinary linear polypropylene resins, and to suppress corrugation during production by providing the resin composition as a non-foamed layer of a foamed sheet. is there.
The range of the amount of the polypropylene resin (X2) relative to the total amount of the polypropylene resin composition (X) is 0 to 95% by weight, preferably 0 to 90% by weight, and more preferably 0 to 85% by weight. With the polypropylene resin (X2), the fluidity of the non-foamed layer can be adjusted.

A well-known thing can be used for the preparation methods of polypropylene resin composition (X). For example, the polypropylene resin composition (X) can be prepared by mixing the polypropylene resins (X1) and (X2) and optional components described later with a dry blend, a Henschel mixer or the like. 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 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 an optional additive is melt-kneaded and pelletized, and the polypropylene resin (X2) and an optional additive are further mixed with the pellet, and then melt-kneaded and pelletized.
b '. A mixture of the polypropylene resin (X2) and an optional additive is melt-kneaded and pelletized, and the polypropylene resin (X1) and an optional additive are further mixed into the pellet, and then melt-kneaded and pelletized.
c. A mixture of the polypropylene resin (X1) and an arbitrary additive and a mixture of the polypropylene resin (X2) and an arbitrary additive are melt-kneaded to obtain each pellet, and the obtained pellets are Mix.
d. A mixture of the polypropylene resin (X1) and an arbitrary additive and a mixture of the polypropylene resin (X2) and an arbitrary additive are melt-kneaded to obtain each pellet, and the obtained pellets are These are mixed and further melt-kneaded and pelletized.
Such a method can be used.

  The range of the preferable 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 value is more preferably 1.5 / 10 minutes or more. Preferably it is 2.0 / 10 minutes or more, and the upper limit is more preferably 20 g / 10 minutes or less, and still more preferably 15 g / 10 minutes or less. If MFR is 1.0 g / 10 min or more, it is possible to ensure 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 corrugation 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). Moreover, when MFR of the polypropylene component in a block polypropylene (X2Y) and a propylene-ethylene random copolymer component differ, MFR of polypropylene resin composition (X) can also be adjusted by changing the compounding quantity of both. For example, when the MFR of the polypropylene component is higher than the MFR of the propylene-ethylene random copolymer component, when the blending amount of the polypropylene component is increased, the MFR of the polypropylene resin composition (X) is increased 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 by a melt tension tester.
Here, MT is Capillograph 1B manufactured by Toyo Seiki Seisakusho Co., Ltd. Capillary: Diameter 2.0 mm, Length 40 mm, Cylinder diameter: 9.55 mm, Cylinder extrusion speed: 20 mm / min, Take-off speed: 4.0 m / Min., Temperature: 230 ° C. The melt tension as measured is expressed in grams. The upper limit of MT is not particularly required, but if MT is 40 g or less, fluidity is improved and surface roughness is easily suppressed, and therefore, 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 it is often possible to effectively suppress the roughening of the interface between the layers when forming the multilayer sheet, and the corrugated suppression effect is also easily obtained. .
There are several ways to adjust MT within the above range. For example, the MT of the polypropylene resins (X1) and (X2) may be changed, or the blending ratio of the polypropylene resins (X1) and (X2) may be changed. Generally, if the content of the polypropylene component (X1) having a long chain branched structure having a high melt tension is increased, the MT of the resin composition can be increased.

3. Polypropylene resin (W)
The polypropylene-based resin (W) for the foam layer is not particularly limited, but is preferably suitable for extrusion foaming. For example, a polypropylene-based composition composed of specific two components described in JP2013-1000049 And linear polypropylene resins having high melt tension as described in JP-A-2009-67948.
Examples of the polypropylene-based resin (W) for the foam layer include homopolypropylene, propylene-α-olefin random copolymer, and block polypropylene.

  As MFR of the polypropylene-type resin used for a foamed layer, 1-20 g / 10min is preferable, More preferably, it is 2-15 g / 10min.

4). Manufacturing method of multilayer foamed sheet As a manufacturing method of the multilayer foamed 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 extruded molten resin is circularly die. Circular foaming is applied in which a multi-layer foam sheet is formed by stretching and cooling with a cooling mandrel having an outer diameter larger than the slit diameter, and then cutting the cylindrical foam using a cutter or the like. For multilayering, melt and knead each resin for foam layer and non-foam layer with separate extruders, and layer each layer with multilayer mandrel die, multi stack die, multilayer spider mandrel die, multilayer spiral mandrel die, etc. Can be stacked.

  There is no restriction | limiting in particular in the kind of foaming agent to be used, The well-known foaming agent currently used for plastics, rubber | gum, etc. can be used. Moreover, you may use any kind, such as a microcapsule containing a physical foaming agent, a decomposable foaming agent (chemical foaming agent), a thermal expansion agent, etc., or combining several types.

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

  Of these, aliphatic hydrocarbons such as propane, butane, and pentane and carbon dioxide are preferable because they are inexpensive and have high solubility in polypropylene resins. In the case of using carbon dioxide gas, supercritical conditions of 7.4 MPa or more and 31 ° C. or more are more preferable because they are excellent in diffusion and solubility in the resin.

  Specific examples of degradable foaming agents (chemical foaming agents) include a mixture of sodium bicarbonate and an organic acid such as citric acid, an azo foaming agent such as azodicarbonamide and barium azodicarboxylate, and N, N′-dinitrosopentamethylene. Nitroso blowing agents such as tetramine, N, N′-dimethyl-N, N′-dinitrosotephthalamide, sulfohydrazide blowing agents such as p, p′-oxybisbenzenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, tri And hydrazinotriazine. The blending amount of the foaming agent is preferably in the range of 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 a physical foaming agent is used, a bubble regulator can be used as necessary. Examples of the air conditioner 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 dinitrosopentanemethylenetetramine and N, N'-dimethyl-N, N'-dinitrosotephthalamide, benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, p, p'-oxybisbenzenesulfonyl semicarbazide, p- Degradable foaming agents such as toluenesulfonyl semicarbazide, trihydrazinotriazine, barium azodicarboxylate, inorganic powders such as talc and silica, acid salts such as polyvalent carboxylic acids, reaction of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate Examples of mixtures It is possible. These bubble regulators may be used alone or in combination.

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

  In addition, each layer of the foamed layer and the non-foamed layer of the multilayer foamed sheet of the present invention includes 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 colorant, a crystal nucleating agent, and other polymers that can be used for polypropylene can be blended within a range that does not impair the object of the present invention. The 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 polypropylene resin (W).

  Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, and sulfur-based antioxidants. Examples of neutralizing agents include higher fatty acid salts such as calcium stearate and zinc stearate. Examples of the stabilizer and the ultraviolet absorber include hindered amines, nickel complex compounds, benzotriazoles, and benzophenones.

Hereinafter, typical compounds are exemplified as the phenolic antioxidant.
In the monophenol type compound, 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.

  Among the bisphenol type compounds, 2,2′-methylenebis (4-methyl-6-tert-butylphenol) (trade name: Sumilizer MDP-S), 1,1-bis (2′-methyl-4′-hydroxy-5) '-T-Butylphenyl) butane (trade name: Sumilizer BBM-S, Adekastab AO-40), 3,9-bis [2- {3- (3-t-butyl-4-hydroxy-5-methylphenyl) Propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane (trade names: Smither GA-80, Adeka Stab AO-80) can be exemplified.

Among the triphenol type compounds, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane (trade name: ADK 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-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate (trade name: Sumilyzer) BP-179, Cyanox 1790), tris- (3,5-di-tert-butyl-4-hydroxyphenyl) -isocyanu Over door (trade name: Keminokkusu 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 are exemplified as the phosphorus-based antioxidant.
Among the phosphite type compounds, tris (2,4-di-t-butylphenyl) phosphite (trade name: Irgafos 168, Sumilizer P-16, Adeka Stab 2112), trisnonylphenyl phosphite (trade name: Sumilyzer TNP, Adeka Stab) 1178), tris (mixed, mono-dinonylphenyl phosphite) (trade name: ADK STAB 329K), tetrakis (2,4-di-t-butylphenyl) -4,4′-biphenylene diphosphonite (common name: P-EPQ) and cyclic neopentanetetraylbis (2,6-di-t-butyl-4-methylphenyl phosphite) (trade name: ADK STAB PEP-36).

Hereinafter, typical compounds are exemplified as the sulfur-based antioxidant.
In the sulfide type compound, dilauryl-3,3′-thio-dipropionate (common name: DLTDP), di-myristyl-3,3′-thio-dipropionate (common name: DMTDP), distearyl-3,3′-thio- Examples thereof include dipropionate (common name: DSTDP), pentaerythritol-tetrakis- (3-laurylthio-propionate) (trade name: Sumilizer TP-D, ADK 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, benzophenone, salicylate, cyanoacrylate, nickel chelate, inorganic fine particle, and the like are known. Of these, the triazole type is most widely used.
Hereinafter, typical compounds are exemplified as the ultraviolet absorber.
Among triazole-based compounds, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole (trade name: Sumisorb 200, TinuvinP), 2- (2′-hydroxy-5′-t-octylphenyl) benzotriazole (Trade names: Sumisorb 340, Tinuvin 399), 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole (trade names: Sumisorb 320, Tinuvin 320), 2- (2′-hydroxy) -3 ′, 5′-di-t-amylphenyl) benzotriazole (trade names: Sumisorb 350, Tinuvin 328), 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5 Chlorobenzotriazole (trade name: Sumisorb 300, Tinuvin 326) Yes.
Examples of benzophenone-based compounds include 2-hydroxy-4-methoxybenzophenone (trade name: Sumisorb 110) and 2-hydroxy-4-n-octoxybenzophenone (trade name: Sumisorb 130).
Examples of salicylate compounds include 4-t-butylphenyl salicylate (trade name: Seesorb 202). Examples of cyanoacrylate compounds 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 inorganic fine particle compounds include TiO ₂ , ZnO ₂ , and CeO ₂ .

The light stabilizer is generally a hindered amine compound and is called HALS. HALS has a 2,2,6,6-tetramethylpiperidine skeleton and cannot absorb ultraviolet rays, but suppresses photodegradation by various functions. The main functions are said to be three of: scavenging radicals, decomposing hydroxy peroxide compounds, and capturing heavy metals that accelerate the decomposition of hydroxy peroxides.
Hereinafter, typical compounds are exemplified as HALS.
In the sebacate type compound, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (trade name: ADK STAB LA-77, Tinuvin 770), bis (1,2,2,6,6-pentamethyl- 4-piperidyl) sebacate (trade name: Tinuvin 765) can be exemplified.
Among the butanetetracarboxylate type compounds, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (trade name: ADK STAB LA-57), tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (trade name: ADK 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 of 2,2,6,6-pentamethyl-4-piperidinol and tridecyl alcohol (trade name: Adeka Stab LA-62) can be exemplified. .
Examples of the succinic polyester type compound include a condensation polymer of succinic acid and 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine.
In the triazine type compound, 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-teto Lamethyl-4-piperidyl) imino} (trade name: Chimasorb 3346).

  Examples of the inorganic filler include calcium carbonate, silica, hydrotalcite, zeolite, aluminum silicate, magnesium silicate and the like. The compounding quantity of an inorganic filler can be about 50 weight part or less. Examples of the lubricant include higher fatty acid amides such as stearic acid amide.

  Furthermore, 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, and oxamides. it can.

A lubricant is an additive used to improve moldability and fluidity, and has the effect 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, stear Examples include higher fatty acid salts such as calcium phosphate, partial esters of polyhydric alcohols such as stearic acid monoglyceride, and silicone oil.
Among these, specific examples of the higher fatty acid amide 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 hydroxy stearic acid amide, N-oleyl palmitic acid amide, N-stearyl oleic acid amide, N-stearyl erucic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, Can be mentioned.

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

6). Manufacture of a molded object The multilayer foam sheet of this invention can be used for thermoforming. In general, thermoforming is to heat and soften a plastic sheet and press it against a desired mold to eliminate the air in the gap between the mold and the material, and then close the mold to the mold by atmospheric pressure. There are vacuum forming to perform, pressure forming to form using compressed air at atmospheric pressure or higher, and 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.
In addition, a cup-shaped molded body can be obtained by using a molding method generally used in the manufacture of paper cups and the like. The molding method generally used in the manufacture of paper cups and the like here is to prepare a barrel member punched into a fan shape and a bottom member punched into a circle, respectively, and round the barrel on the peripheral edge of the bottom member. This is a method of forming into a cup shape by entraining the lower end of the part and heat-sealing.

7). Applications The molded products obtained above are used for foamed food containers such as trays, cups, dishes, cups, automobile door trims, automobile trunk mats, automobile interior materials, building materials, etc. Suitable for heat insulating materials, packaging, stationery, etc.

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

[Evaluation method]
In Examples and Comparative Examples, various physical properties of a polypropylene resin composition, a multilayer foamed sheet, and its constituent components were measured and evaluated according to the following evaluation methods.

(1) Multilayer foamed sheet density A test piece was cut out from the polypropylene-based (multilayer) foamed sheet obtained in the examples and comparative examples, and the test piece weight (g) was determined from the outer dimensions of the test piece (cm ^3). ) Divided by. The density was determined by measuring according to JIS K7222.

(2) Corrugated evaluation of multilayer foamed sheet Corrugated evaluation during production was visually evaluated according to the following criteria during the production of the polypropylene resin composition foamed sheet obtained in each Example and each Comparative Example.
A: No corrugation is observed at the die exit.
○: Corrugation is confirmed at the die outlet, but no influence of corrugation is observed after the cooling mandrel.
Δ: Corrugation is confirmed at the die outlet, and the influence of the corrugation is locally observed even after the cooling mandrel.
X: The corrugation at the die outlet is remarkable, and the influence of the corrugation is widely recognized even after the cooling mandrel.

(3) Appearance Evaluation of Multilayer Foamed Sheet For the surface appearance evaluation of the foamed sheet, the polypropylene resin composition foamed sheets obtained in the respective Examples and Comparative Examples were visually evaluated based on the following criteria.
(Double-circle): The unevenness | corrugation by visual observation is not confirmed on the foam sheet surface, but it is smooth.
◯: Concavities and convexities are visually observed on the foam sheet surface, but are smooth.
X: Concavities and convexities due to bubbles are confirmed on the surface of the foam sheet, and the roughness is conspicuous.

[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 Nippon Polypro Co., Ltd. were used as polypropylene PP-1 and PP-2 having a long-chain branched structure. The results of analyzing PP-1 and PP-2 are shown in Table 1. ^{From the 13} C-NMR measurement and the branching index g ′ measurement results, it was confirmed that long chain branching was present in this polypropylene.

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

PP-5
BC3BRF manufactured by Nippon Polypro Co., Ltd. was used as the block polypropylene PP-5.
Table 2 shows the results of analysis of block polypropylene PP-5.
PP-6
FTS3000 manufactured by Nippon Polypro Co., Ltd. was used as the block polypropylene PP-6.
Table 2 shows the results of analysis of block polypropylene PP-6.
PP-7
MA1B manufactured by Nippon Polypro Co., Ltd. was used as homopolypropylene PP-7.
The results of analysis of homopolypropylene PP-7 are shown in Table 2.
PP-3 to PP-7 were confirmed to have no long-chain branch structure from the measurement results of ¹³ C-NMR and branching index g ′.

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). The evaluation results of MFR and MT of the polypropylene resin composition (X-1, X-2 and X-3) are shown in Table 3.

[Example 1]
1) Raw materials used The following materials were used as the polypropylene resin composition for the foam layer, the air conditioner, and the polypropylene resin composition for the non-foam 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 a polypropylene resin composition for non-foamed layers
-Bubble regulator: 0.5 parts by weight of chemical foaming agent (trade name: Hydrocerol CF40E-J, manufactured by Nippon Boehringer Ingelheim Co., Ltd.) with respect to 100 parts by weight of PP-5
2) Production of multilayer foam sheet by circular extrusion foaming A multilayer foam sheet was produced as follows.
2-1) In order to produce a multi-layer foam sheet, the polypropylene resin composition for the foam layer is introduced into the raw material supply hopper of a tandem type extruder having screw diameters of 40 mmΦ and 50 mmΦ respectively for the first and second stage extruders. did. The cylinder set temperature of the first-stage extruder was set to 230 ° C., and the resin was heated and melted to be plasticized and the bubble regulator was decomposed, and butane gas was injected and mixed using a gas injection pump at 0.35 kg / h. Thereafter, the setting temperature of the second-stage extruder was quickly cooled to 165 ° C., and the propylene-based resin composition for the foam layer was subjected to a circular die (caliber = aperture = 55 mmΦ, gap = 0.75 mm) and foamed by extrusion into the atmosphere. Moreover, about the polypropylene resin composition (X-1) for non-foaming layers, after putting into the raw material supply hopper of an extruder with a diameter of 30 mmΦ, the polypropylene resin (X-1) is heated and melted at a cylinder set temperature of 190 ° C. The laminated foam was manufactured by laminating inside the foamed layer with a multilayer spiral mandrel and coextruding from the tip of the circular die together with the foamed layer. The total extrusion rate of the foam layer composition and the non-foam layer composition was 15 kg / h.
2-2) The foam was cooled by passing it through a cooling mandrel having an outer diameter of 120 mmΦ, and then cut into a sheet by a rotor cutter, 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 foam layer density of 0.196 g / cm ³ and a good appearance. Table 4 shows the evaluation results of the foam sheet.

[Examples 2-3]
A multilayer foamed sheet was produced in the same manner as in Example 1 except that the non-foamed layer was placed outside the foamed layer (Example 2) or on both sides (Example 3).
When disposing the non-foamed layer on the outside of the foamed layer, using a 30 mmΦ extruder having the same type as the extruder used for laminating on the inside, the polypropylene resin composition for the non-foamed layer is put into the raw material supply hopper, The polypropylene resin composition for the non-foamed layer was heated and melted at a cylinder set temperature of 190 ° C., and then laminated on the outside of the foamed layer with a multilayer spiral mandrel, and co-extruded from the tip of the circular die together with the foamed layer to produce a laminated foam.
When laminating the non-foamed layer on both sides of the foamed layer, a laminated foam was produced by starting both the extruders used when laminating the inside and outside.
The obtained foamed sheet had a foam layer density of 0.136 to 0.180 g / cm ³ and a good appearance. Table 4 shows the evaluation results of the foam sheet.

[Example 4]
Circular extrusion foaming was performed in the same manner as in Example 3 except that block polypropylene (PP-6) was used as the foam layer instead of block polypropylene (PP-5) to obtain various multilayer foam sheets. The resulting foamed sheet had a foamed layer density of 0.164 g / cm ³ , no corrugation was produced during production, and the appearance was very beautiful. Table 4 shows the evaluation results of the foam sheet.
[Example 5]
Except that the non-foamed layer was changed to polypropylene resin composition X-2, circular extrusion foaming was performed in the same manner as in Example 3 to obtain various multilayer foamed sheets. The obtained foamed sheet had a foamed layer density of 0.185 g / cm ³ , no corrugation was produced during production, and the appearance was very beautiful. Table 4 shows the evaluation results of the foam sheet.

[Comparative Example 1]
The single-layer foam sheet was produced in Example 1 without starting the non-foamed layer extruder. Other conditions are the same as in Example 1. The obtained foamed sheet had a density of the foamed layer of 0.205 g / cm ³ , and corrugation was remarkably generated during production, there were many irregularities, and the appearance was impaired. Table 5 shows the evaluation results of the foam 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 branched structure was laminated as a non-foamed layer by coextrusion. The obtained multilayer foamed sheet had a density of the foamed layer of 0.203 g / cm ³ , and corrugation was remarkably generated during production, and there were many irregularities and the appearance was impaired. Table 5 shows the evaluation results of the foam sheet.

[Comparative Example 4]
As a resin for the non-foamed layer, a homopolypropylene PP-7 having no long chain branching was used in place of PP-2 having a long chain branching used in Example 5, except that it was used as a mixture with PP-4. Obtained a multilayer foamed sheet in the same manner as in Example 5. In the obtained foamed sheet, the density of the foamed layer was 0.209 g / cm ³ , a corrugate was confirmed during production, and the appearance was inferior to the examples. Table 5 shows the evaluation results of the foam sheet.

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

  The polypropylene multilayer foam sheet obtained by co-extrusion of the polypropylene resin composition for non-foamed layer of the present invention, and the thermoformed article using the multilayer foam sheet have excellent surface appearance because corrugation during production is suppressed. , Foaming 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 supports heating with a microwave oven and filling of high-temperature liquids. It can be suitably used in a wide range of fields such as foamed food containers such as trays, dishes and cups, automobile interior trims such as automobile door trims and automobile trunk mats, building materials, heat insulating materials, packaging and stationery, and has an extremely high industrial value.

Claims (5)

Polypropylene resin composition (X) comprising 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) having no long chain branched structure (however, polypropylene A non-foamed layer comprising a resin (X1) and a polypropylene resin (X2) in a total amount of 100 wt%),
A multilayer foamed sheet comprising a polypropylene resin (W) and a foamed layer having a foaming ratio of 4.0 or more.   The multilayer foamed sheet according to claim 1, wherein the polypropylene resin (W) is a polypropylene resin having no long-chain branched structure.   A multilayer foamed molded article comprising the multilayer foamed sheet according to claim 1. Polypropylene resin composition (X) comprising 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) having no long chain branched structure (however, polypropylene The total amount of the resin (X1) and the polypropylene resin (X2) is 100% by weight.)
A resin composition for a foam layer containing a polypropylene resin (W) and a foaming agent;
A method for producing a multilayer foamed sheet, characterized by co-extrusion from a circular die.   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 branched structure.