JP2019044059A - Extrusion foam sheet, resin foam molding, and method for producing extrusion foam sheet - Google Patents

Abstract

To provide an extrusion foam sheet having fine foam and having excellent strength, and a resin foam molding having excellent lightness in weight and strength.SOLUTION: The present invention provides an extrusion foam sheet in which, the content of volatile organic compounds (VOCs) in a foam layer is 200 mg/kg or more and 4000 mg/kg or less. The aromatic vinyl monomer is styrene. The volatile organic compounds include styrene, and the content of styrene in the foam layer is 35 mg/kg or more and 800 mg/kg or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an extruded foam sheet, a foamed resin molded article, and a method for producing the extruded foam sheet.

BACKGROUND ART Conventionally, polypropylene resins are used as raw materials for various molded articles because of their excellent mechanical properties and chemical resistance.
As the molded article, for example, a two-dimensional thing such as a non-foamed film or an extruded foam sheet, and a thing obtained by subjecting a film or an extruded foam sheet to a thermoforming to give a three-dimensional shape are known. It is done.
A thermoformed article obtained by subjecting the extruded foam sheet to thermoforming is used alone or in combination with other members as a component of various foamed resin articles.

The extruded foam sheet is usually prepared by melt-kneading a polypropylene-based resin composition containing a polypropylene-based resin, a foaming agent, and the like with an extruder, and extrusion-foaming into a sheet form from a die attached to the tip of the extruder. It is manufactured by the method.
As the extruded foam sheet, one having a foam layer alone or one having a laminated structure formed by coextrusion of a foam layer and a non-foam layer is known.
Foamed resin molded articles obtained by thermoforming extruded foam sheets are used in various applications because they have both light weight and high strength.

When forming an extruded foam sheet by such a manufacturing method, it is advantageous for the polypropylene resin composition to exhibit a melt tension of a certain level or more in order to make the foam state of the foam layer dense.
In addition, when thermoforming is performed using a compact foamed extruded foam sheet, the lightness and strength of the foamed resin molded product can be made more excellent.
From such a thing, in order to exhibit high melt tension with respect to a polypropylene resin, modification | reformation which gives a branched structure to a polypropylene resin is performed.
As a method of producing such a modified polypropylene resin, there is known a method of reacting a polypropylene resin, an organic peroxide and an aromatic vinyl monomer (see Patent Document 1 below).

  Conventionally, not only an extruded foam sheet obtained by extrusion-foaming a modified polypropylene resin composition containing the above modified polypropylene resin as described above, but also when producing an extruded foam sheet generally, a modified polypropylene The low molecular weight compounds generated during the production of the epoxy resin and the thermal decomposition products in the extruder may remain as volatile organic compounds (VOC) in the sheet, which may cause odors to be generated in the extruded foam sheet. A method is adopted where it is difficult for residual organic compounds to survive.

JP, 2016-089143, A

Conventionally, even when an extruded foam sheet is produced using a modified polypropylene-based resin instead of a general polypropylene-based resin, the foamed state may not be sufficiently dense in some cases, and an improvement is required.
That is, in the conventional extruded foam sheet, there is a demand for further improvement of the compactness in the foamed state, but a method for satisfying such a demand has not yet been found.
Then, this invention makes it a subject to provide the extrusion-foamed sheet of a precise foaming state and to provide the foamed resin molded article excellent in lightness and intensity | strength in order to satisfy the above requests.

The inventors of the present invention diligently studied to solve the above-mentioned problems. When making an extruded foam sheet using a modified polypropylene resin, by leaving the VOC intentionally left, the cells of the extruded foam sheet become finer. It has been found that the toughness of the extruded foam sheet is improved and the strength is increased, and the present invention has been completed.
In addition, the inventor of the present invention modified polypropylene-based resin to produce modified polypropylene-based resin, and then modified polypropylene-based resin in the process of producing an extruded foam sheet using the modified polypropylene-based resin. It has been found that adjusting the amount of VOC contained is effective for obtaining the extruded foam sheet as described above, and the present invention has been completed.

  In order to solve the above problems, the present invention is an extruded foam sheet having a foam layer formed of a modified polypropylene resin composition containing a modified polypropylene resin, wherein the modified polypropylene resin is a polypropylene resin An extruded foam sheet is provided, wherein the volatile organic compound (VOC) content in the foam layer is 200 mg / kg or more and 4000 mg / kg or less of a reaction product of an organic peroxide and an aromatic vinyl monomer.

  The present invention is a foamed resin molded article wherein a part or the whole is constituted by a thermoformed article, and the thermoformed article is constituted by an extruded foam sheet, wherein the thermoformed article is the above-mentioned extruded foam sheet Provided is a foamed resin molded article configured.

  In the present invention, a reaction step of reacting a polypropylene resin, an organic peroxide and an aromatic vinyl monomer by melt-kneading to produce a modified polypropylene resin, and the modified polypropylene obtained in the reaction step The system resin is subjected to heat treatment to remove a part of the volatile organic compound (VOC) contained in the modified polypropylene resin, and the content of the volatile organic compound (VOC) is 1000 mg / kg or more and 10000 mg. Carrying out a VOC removal step of not more than 1 kg / kg, and further carrying out an extrusion step of extruding and foaming the modified polypropylene resin composition containing the modified polypropylene resin subjected to the VOC removal step, Of producing extruded foam sheet having extruded layer formed of high-grade polypropylene resin composition To.

  ADVANTAGE OF THE INVENTION According to this invention, the extrusion-foaming sheet of a precise | minute foaming state is provided, and the foamed resin molded article excellent in lightness and intensity | strength can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic sectional drawing of the extrusion-foaming sheet of one Embodiment. The schematic sectional drawing of the extrusion-foaming sheet of other embodiment. Explanatory drawing explaining the measuring method of the average bubble diameter of an extrusion foaming sheet | seat (foaming layer).

An embodiment of the present invention will be described.
First, an extruded foam sheet will be described with reference to FIGS.
Even if the extruded foam sheet 1 in the present embodiment has only a single foam layer 10 as shown in FIG. 1, a non-foamed layer 20 on one side or both sides of the foam layer 10 as shown in FIG. 20 'may be laminated.
In addition, although the extruded foam sheet in the present embodiment is not shown in the figure, it may have a plurality of foam layers or may have a plurality of non-foam layers laminated on one side of the foam layer. .

The foamed resin molded article in the present embodiment is at least a part of a thermoformed article obtained by thermoforming the extruded foam sheet 1, and includes a foamed portion constituted by the foamed layer 10.
The foamed resin molded article in the present embodiment may include a thermoformed article formed by the extruded foam sheet 1 having the non-foamed layer 20, 20 ', and the non-foamed layer together with the foamed portion formed by the foamed layer 10. It may have a non-foamed part formed by 20, 20 '.
That is, in the foamed resin molded product in the present embodiment, the lightness and strength of the foamed layer 10 are reflected in the characteristics.

The foam layer 10 in the extruded foam sheet 1 is formed of a modified polypropylene resin composition containing a modified polypropylene resin which is a reaction product of a polypropylene resin, an organic peroxide and an aromatic vinyl monomer. .
And, the content of volatile organic compound (VOC) in the foam layer 10 of the extruded foam sheet 1 is 200 mg / kg or more and 4000 mg / kg or less.

The volatile organic compound (VOC) in the foam layer 10 is more in consideration of more reliably exerting the effect of densifying the cells of the foam layer 10 and the effect of causing the foam layer 10 to exhibit excellent toughness. Preferably, it is included.
From such a viewpoint, the content of the volatile organic compound (VOC) in the foam layer 10 is preferably 250 mg / kg or more, more preferably 350 mg / kg or more, and 400 mg / kg or more. Is particularly preferred.
On the other hand, when the volatile organic compound (VOC) is excessively contained, the bubbles of the foam layer 10 tend to be coarsened, and the plasticizing effect by the VOC acts strongly to not sufficiently improve the strength of the foam layer 10 There is.
Therefore, the content of the volatile organic compound (VOC) in the foam layer 10 is preferably 2500 mg / kg or less, more preferably 2000 mg / kg or less, and particularly preferably 1500 mg / kg or less .

Among VOCs, in particular, styrene plasticizes a polypropylene-based resin, and since it is hard to dissipate from the foam layer at normal temperature, the foam layer can exhibit excellent toughness over a long period of time.
Therefore, in the extruded foam sheet 1 of the present embodiment, it is preferable that the modified polypropylene-based resin in which styrene is used as the aromatic vinyl monomer is contained in the foam layer 10.
And it is preferable that one part or all part of the volatile organic compound (VOC) contained in the foaming layer 10 is styrene.
The content of styrene in the foam layer 10 is preferably 35 mg / kg or more and 800 mg / kg or less.
The content of styrene in the foam layer 10 is more preferably 50 mg / kg or more, and particularly preferably 100 mg / kg or more.
The content of styrene in the foam layer 10 is more preferably 500 mg / kg or less, still more preferably 300 mg / kg or less, and particularly preferably 250 mg / kg or less.

The foam layer 10 usually has a thickness of 0.5 mm or more and 5 mm or less.
In the case where the non-foamed layers 20 and 20 'are provided, the thickness thereof is usually 0.01 mm or more and 0.5 mm or less.
The density (apparent density) of the foam layer 10 is preferably 0.3 g / cm ³ or less and 0.25 g / cm ³ or less in that the effects of the present invention can be more remarkably exhibited. More preferably, it is particularly preferably 0.2 g / cm ³ or less.
The density (apparent density) of the foam layer 10 is usually 0.07 g / cm ³ or more.
The open cell ratio of the foam layer 10 is preferably 40% or less in order to exhibit excellent strength of the foamed resin molded product.
The open cell ratio of the foam layer 10 is preferably 35% or less, more preferably 30% or less, still more preferably 25% or less, and particularly preferably 20% or less.
The open cell ratio of the foam layer 10 is usually 1% or more.

In the present embodiment, the modified polypropylene-based resin which is the main component of the modified polypropylene-based resin composition constituting the foam layer 10 is (A) polypropylene-based resin, (B) organic peroxide, and (C) 2.) It is obtained by reacting a resin composition containing an aromatic vinyl monomer (hereinafter also referred to as "raw material composition").
As the modified polypropylene-based resin of the present embodiment, it is preferable to adopt one in which the phase angle determined by frequency dispersion dynamic viscoelasticity measurement at 200 ° C. is 30 ° or more and 70 ° or less at a frequency of 0.01 Hz.
In frequency dispersive dynamic viscoelasticity measurement, the influence of the viscosity term tends to appear in the low frequency region.
That is, in the modified polypropylene-based resin of the present embodiment, the phase angle in the low frequency region is small, and it is difficult for the molecules to “slip”.
Therefore, the modified polypropylene-based resin of the present embodiment exhibits a moderate elongation when foaming to form a foam layer, and the rapid reduction of the cell membrane due to the growth of the cell is suppressed. It is advantageous to obtain a foamed layer 10 having a low open cell rate.

The phase angle is determined as follows.
(How to determine the phase angle)
The dynamic viscoelasticity measurement is performed by a viscoelasticity measurement apparatus PHYSICA MCR 301 (manufactured by Anton Paar), a temperature control system CTD450.
First, a modified polypropylene resin to be a sample is pressed with a heat press under a condition of heating at 200 ° C. for 5 minutes to prepare a disc sample having a diameter of 25 mm and a thickness of 3 mm.
Next, the sample is set on the plate of the viscoelasticity measuring device heated to the measurement temperature (200 ° C.), and is heated and melted for 5 minutes under a nitrogen atmosphere.
Thereafter, the space is crushed to 2.0 mm with a parallel plate of 25 mm in diameter, and the resin which has run out of the plate is removed.
After heating for 5 minutes after reaching the measurement temperature ± 1 ° C, strain 5%, frequency 0.01 to 100 (Hz), the number of measurement points 21 (5 points / digit), measurement temperature 200 ° C Dynamic viscoelasticity measurement is performed to measure the phase angle δ (°).
The measurement start is from the high frequency side (100 Hz).
Then, a phase angle δ at a frequency of 0.01 Hz is obtained.

The modified polypropylene resin is one that has been modified so as to exhibit higher melt tension than the starting material (A) polypropylene resin.
Whether or not the modified polypropylene-based resin exhibits a melt tension higher than that of the polypropylene-based resin used as a raw material can be determined, for example, by comparing the melt tensions of the two at a temperature of 230 ° C.
Since a common polypropylene resin has a melt tension at 230 ° C. of less than 5 cN, the melt tension measured at 230 ° C. has a value of 6 cN or more, as compared to the starting material (A) polypropylene resin. What is shown can be regarded as a modified polypropylene resin.

The modified polypropylene resin preferably has a melt tension of 6 cN or more at 230 ° C., more preferably 10 cN or more at 230 ° C., and a melt tension of 15 cN or more at 230 ° C. Is particularly preferred.
However, if the melt tension of the modified polypropylene resin is too high, the load on the extruder may be increased when extruding, so the value at 230 ° C. is preferably 30 cN or less, preferably 28 cN or less It is more preferable that

In addition, when melt | dissolution tension is calculated | required regarding modified | reformed polypropylene resin etc., it can obtain | require by the following methods.
(Melt tension measurement method)
If the sample to be measured is a pellet, use it as it is, and if it is a sheet such as an extruded foam sheet, use a pelletizer (for example, “Handtruder Model PM-1” manufactured by Toyo Seiki Seisakusho Co., Ltd.) And pelletized under conditions of a cylinder temperature of 220.degree. C. and a waiting time of 2.5 minutes from sample loading to extrusion start.
Melt tension is measured using a twin bore capillary rheometer Rheologic 5000T (manufactured by Italy Chiast).
That is, after filling the measurement sample resin in a barrel with a diameter of 15 mm heated to the test temperature and preheating for 5 minutes, the piston lowering speed from the capillary die (bore diameter 2.0 mm, length 20 mm, inflow angle flat) of the above measuring device Using a take-up roll after passing the string through a tension detection pulley located 27 cm below the capillary die while holding (0.1546 mm / s) constant and extruding in a string-like manner The winding speed is gradually increased at an initial speed of 8.7 mm / s and an acceleration of 12 mm / s ² , and the average of the maximum value and the minimum value immediately before the string is cut is taken as the melt tension of the sample. .
When there is only one maximum point in the tension chart, the maximum value is taken as the melt tension.

The modified polypropylene resin preferably has a melt mass flow rate (MFR) having a predetermined value in order to reduce the load on the extruder during extrusion and to cause the foam layer 10 to exhibit good foamability.
More specifically, the modified polypropylene resin preferably has an MFR of 0.5 g / 10 min or more, more preferably 0.7 g / 10 min or more, and particularly preferably 1.0 g / 10 min or more preferable.
The MFR of the modified polypropylene resin is preferably 0.7 g / 10 min or more in order to form a foam layer excellent in closed cell properties (low open cell rate).
However, if the MFR is excessively high, it may be difficult to cause the foam layer 10 to exhibit good foamability, so the MFR of the modified polypropylene resin is preferably 5.0 g / 10 min or less, and 3. More preferably, it is 0 g / 10 min or less.

The MFR of a polypropylene based resin which is a raw material of a modified polypropylene based resin or a modified polypropylene based resin is measured as follows.
When the measurement target is a pellet, it is used as it is as a measurement sample.
When the object to be measured is a foamed sheet, the foamed sheet is pelletized using a pelletizer "Hand Truuda model PM-1" manufactured by Toyo Seiki Seisakusho Co., Ltd., and used as a measurement sample.
In addition, the cylinder temperature at the time of producing a pellet from a foaming sheet using a pelletizer shall be 220 degreeC, and the waiting time from sample filling to extrusion start shall be 2.5 minutes.
Melt mass flow rate (MFR) is a test of JIS K 7210: 1999 "plastic-thermoplastic plastic melt mass flow rate (MFR) and melt volume flow rate (MVR) using semi-automatic melt indexer 2A manufactured by Toyo Seiki Seisaku-sho, Ltd. Method: Measured by "b) Method for measuring the time for which the piston travels a predetermined distance" described in Method B.
Measurement conditions are a sample amount of 3 to 8 g, a preheating time of 270 seconds, a load holding time of 30 seconds, a test temperature of 230 ° C., a test load of 21.18 N, and a piston movement distance (interval) 4 mm.
The number of tests is 3 times, and the average value is the value of melt mass flow rate (g / 10 min).

  In order to obtain the above modified polypropylene-based resin, it is preferable that the starting material (A) polypropylene-based resin has predetermined melting characteristics.

[(A) polypropylene resin]
A polypropylene resin is a polymer obtained by polymerizing a propylene monomer.
Examples of the polypropylene-based resin to be contained in the raw material composition for obtaining the modified polypropylene-based resin include a homopolymer of a propylene monomer (homopolypropylene resin) and a copolymer of a propylene monomer and another monomer.
The content of the propylene monomer is preferably 50% by mass or more, and the content of the propylene monomer is more preferably 80% by mass or more in 100% by mass of the polymerization component, for example. The content of is particularly preferably 90% by mass or more.
The copolymerization may be random copolymerization (random polypropylene resin) or block copolymerization (block polypropylene resin).
When the polypropylene resin is a copolymer, the component other than the propylene monomer is preferably at least one selected from the group consisting of an ethylene monomer and an α-olefin monomer having 4 to 8 carbon atoms, and the ethylene monomer and 1 More preferably, it is one or more of butene monomers.

The raw material composition for producing the modified polypropylene resin of this embodiment preferably contains at least two types of polypropylene resins, and at least two types of homopolypropylene resin and block polypropylene resin. Is preferred.
When the total amount of polypropylene resins to be contained in the raw material composition is 100% by mass, the homopolypropylene resin is preferably contained in a proportion of 85% by mass or more and less than 100% by mass, and 90% by mass or more and 99% by mass It is more preferable to contain in the following ratio.
The block polypropylene resin is preferably contained in a proportion of more than 0% by mass and 15% by mass or less, when the total amount of the polypropylene-based resin to be contained in the raw material composition is 100% by mass, and 1% by mass or more and 10%. It is more preferable to contain in the ratio of mass% or less.

The polypropylene resin to be contained in the raw material composition preferably has a relatively high MFR.
The polypropylene resin used as a general extrusion foam sheet forming material has an MFR of about 1 g / 10 min to 3 g / 10 min, but in the present embodiment, the MFR of the polypropylene resin used as a starting material of the modified polypropylene resin Is preferably 4.0 g / 10 min or more, more preferably 5.0 g / 10 min or more, and particularly preferably 6.0 g / 10 min or more.
The MFR of the polypropylene resin is preferably 20.0 g / 10 min or less, more preferably 15.0 g / 10 min or less, and particularly preferably 10.0 g / 10 min or less.

When the raw material composition contains two types of polypropylene-based resins of homopolypropylene resin and block polypropylene resin, it is preferable that all of them have the above-mentioned MFR.
The MFR of the homopolypropylene resin and the MFR of the block polypropylene resin are preferably close to each other.
For example, assuming that the value of MFR of homopolypropylene resin is "MFR-H" and the value of MFR of block polypropylene resin is "MFR-B", these ratios ("MFR-H" / "MFR-B") Is preferably 0.8 or more and 1.25 or less.

[(B) organic peroxide]
The (B) organic peroxide of the present embodiment has a hydrogen abstraction ability to a polypropylene resin, and is not particularly limited. For example, hydroperoxide, dialkyl peroxide, peroxy ester, diacyl peroxide, peroxy Oxydicarbonate, peroxyketal, ketone peroxide and the like can be mentioned.

Examples of the hydroperoxide include permethane hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide.
Examples of the dialkyl peroxide include dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di (t-butylperoxy) -hexyne-3 and the like. .
Examples of the peroxy ester include t-butyl peroxy 2-ethylhexyl carbonate, t-hexyl peroxy isopropyl monocarbonate, t-hexyl peroxy benzoate, t-butyl peroxy benzoate, t-butyl peroxy laurate, t-Butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxyacetate, 2,5-dimethyl 2,5-di (benzoylperoxy) hexane, and t-butylperoxyisopropyl monocarbonate Etc.
Examples of the diacyl peroxide include dibenzoyl peroxide, di (4-methylbenzoyl) peroxide, and di (3-methylbenzoyl) peroxide.
Examples of the peroxydicarbonate include di (2-ethylhexyl) peroxydicarbonate and diisopropyl peroxydicarbonate.
Examples of the peroxyketal include, for example, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-t-butylperoxycyclohexane, 2,2-di (t -Butylperoxy) -butane, n-butyl 4,4-di- (t-butylperoxy) valerate, and 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane and the like Be
Examples of the ketone peroxide include methyl ethyl ketone peroxide, acetylacetone peroxide and the like.

The organic peroxide of the present embodiment is preferably peroxy ester, diacyl peroxide, or peroxy dicarbonate.
The organic peroxide preferably has a structure represented by the following general formula (X).

（但し、Ｒ^１は、置換若しくは非置換のフェニル基又は置換若しくは非置換のアルコキシ基を表し、Ｒ^２は１価の有機基を表している。）

(However, R ¹ represents a substituted or unsubstituted phenyl group or a substituted or unsubstituted alkoxy group, and R ² represents a monovalent organic group.)

In the general formula (X), when “R ¹ ” is an alkoxy group, “R ¹ ” is an alkyl group having a branched structure having 3 to 8 carbon atoms (eg, isopropyl, t-butyl, It is preferable that it is an alkoxy group which oxygen atom couple | bonded with t-hexyl, 2-ethylhexyl etc.).
When "R ¹ " is other than an alkoxy group in which an oxygen atom is bonded to 2-ethylhexyl, the oxygen atom is preferably bonded to either a secondary carbon or a tertiary carbon, and is preferably represented by the following general formula (Y) It is preferred to have the structure shown.

（但し、式中の「Ｒ^１１」、「Ｒ^１２」は、何れか一方がメチル基で他方が水素原子で、「Ｒ^１４」が炭素数１〜６の直鎖アルキル基を表し、「Ｒ^１３」が２級炭素であることを表している。）

(Wherein, “R ¹¹ ” and “R ¹² ” in the formula each represent a methyl group and the other is a hydrogen atom, and “R ¹⁴ ” represents a linear alkyl group having 1 to 6 carbon atoms, “R ¹³ represents that it is a secondary carbon.)

In addition, when "R ¹ " is either a substituted or unsubstituted phenyl group, "R ¹ " is an unsubstituted phenyl group or a substituted phenyl in which one hydrogen atom is substituted by a methyl group. Is preferred.

Further, it is preferable that “R ² ” also have a bulky structure such as branched alkyl and phenyl.
Specifically, it is preferable to have a structure represented by the following general formula (Z).

（但し、式中の「Ｒ^２１」は、炭素数１〜６の直鎖アルキル基か、又は、フェニル基を有する１価の有機基かの何れかであることを表している。）

(However, “R ²¹ ” in the formula represents either a linear alkyl group having 1 to 6 carbon atoms or a monovalent organic group having a phenyl group.)

  Examples of the organic peroxide having a structure represented by the general formula (X) include t-butylperoxy 2-ethylhexyl carbonate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t -Hexylperoxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, dibenzoyl peroxide, di (4-methylbenzoyl) peroxide, diisopropyl peroxydicarbonate, etc. .

In the raw material composition for producing the modified polypropylene resin, the content of the (B) organic peroxide is 0.1 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of the (A) polypropylene resin Is preferred.
In the modified polypropylene-based resin of the present embodiment, when the content of the organic peroxide is too low, the reactivity of the raw material composition becomes low, and thus there is a possibility that a favorable reforming effect is not exhibited.
In the modified polypropylene-based resin of the present embodiment, when the content of the organic peroxide is excessive, the decomposition reaction of the polypropylene-based resin is likely to occur at the time of melt-kneading, so that the elastic component becomes small and a favorable modifying effect is exhibited. May not be
That is, when the content of the organic peroxide is 0.1 parts by mass or more and 1.5 parts by mass or less, the raw material composition is excellent without controlling the reaction conditions at the time of melt-kneading with high accuracy A modified polypropylene-based resin having a melt tension can be produced.

In order to more reliably produce a modified polypropylene resin having excellent melt tension, the content of the organic peroxide relative to 100 parts by mass of the polypropylene resin is more preferably 0.3 parts by mass or more.
Similarly, the content of the organic peroxide relative to 100 parts by mass of the polypropylene resin is more preferably 1.0 parts by mass or less.

[(C) aromatic vinyl monomer]
The aromatic vinyl monomer (C) is a component which chemically bonds to the (A) polypropylene resin to form a branched structure and acts as a crosslinking agent for crosslinking the polypropylene resins.
The aromatic vinyl monomer to be contained in the raw material composition may be only one kind or two or more kinds.
Examples of the aromatic vinyl monomer include styrene; methylstyrene such as o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, β-methylstyrene, dimethylstyrene, trimethylstyrene and the like; α-chloro Chlorostyrenes such as styrene, β-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, dichlorostyrene, trichlorostyrene and the like; o-bromostyrene, m-bromostyrene, p-bromostyrene, dibromostyrene, Bromostyrenes such as tribromostyrene; o-fluorostyrenes, m-fluorostyrenes, p-fluorostyrenes, difluorostyrenes, fluorostyrenes such as trifluorostyrenes; o-nitrostyrenes, m-nitrostyrenes, p-nitros Nitrostyrenes such as thylene, dinitrostyrene, trinitrostyrene; o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, dihydroxystyrene, vinylphenols such as trihydroxystyrene; o-divinylbenzene, m-divinylbenzene, p -Divinylbenzene such as divinylbenzene; and isopropenylbenzene such as o-diisopropenylbenzene, m-diisopropenylbenzene, p-diisopropenylbenzene and the like.
Among them, the aromatic vinyl monomer is preferably styrene.

It is preferable that content of (C) aromatic vinyl monomer in a raw material composition is 0.1 mass part or more and 10 mass parts or less with respect to 100 mass parts of (A) polypropylene resin.
When the content of the aromatic vinyl monomer is too low, there is a possibility that a branched or crosslinked structure may not be sufficiently formed in melt-kneading.
In addition, when the content of the aromatic vinyl monomer is too small, the suppression of the decomposition of the resin by the peroxide is also insufficient, and there is a possibility that a favorable reforming effect can not be exhibited.
Furthermore, when the content of the aromatic vinyl monomer is too low, the amount of volatile organic compound (VOC) contained in the modified polypropylene-based resin is reduced, and the volatile organic compound (VOC) in the foam layer of the extruded foam sheet There is a risk that the content of
Therefore, the content of the aromatic vinyl monomer in the raw material composition is more preferably 0.5 parts by mass or more, and particularly preferably 1 part by mass or more with respect to 100 parts by mass of the polypropylene resin.

If the content of the aromatic vinyl monomer in the raw material composition is too large, a part of the aromatic vinyl monomer tends to be unreacted in melt-kneading, and the content of volatile organic compound (VOC) becomes excessive. There is a fear.
In addition, when the content of the aromatic vinyl monomer is too large, there is a possibility that the modified polypropylene resin may cause a problem of white turbidity caused by micro phase separation and the like.
In such a case, the modified polypropylene-based resin may be poor in nobi and may not exhibit a favorable modifying effect.
Furthermore, when the content of the aromatic vinyl monomer is too large, when making the modified polypropylene-based resin, there may be a case where a significantly high molecular weight product (referred to as "gel") is generated. .
Such a gel has a large difference in heat melting behavior from that of a non-polymerized product, and if it is excessively contained in the foam sheet, the appearance of the foam sheet may be impaired or the open cell ratio of the foam sheet may be excessively increased. Can be a factor to reduce the strength.
Therefore, the content of the aromatic vinyl monomer in the raw material composition is more preferably 8 parts by mass or less and particularly preferably 7 parts by mass or less with respect to 100 parts by mass of the polypropylene resin.

In addition, if necessary, the raw material composition may contain a monomer other than the aromatic vinyl monomer.
Examples of the monomer include ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene, 1 Α-olefin monomers such as heptene, 3-methyl-1-hexene, 1-octene and 1-decene; cycloolefin monomers such as cyclopentene and norbornene; 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, Diene monomers such as 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6-octadiene; chlorinated monomers such as vinyl chloride and vinylidene chloride; acrylonitrile, acrylic acid, methacrylic acid, maleic acid, Ethyl acrylate, butyl acrylate, glycidyl acrylate, methacrylic It includes acetate based monomers such as vinyl acetate, epoxy monomers; methyl, glycidyl methacrylate, acrylic monomers such as maleic anhydride.

[(D) radical scavenger]
In order to obtain the modified polypropylene resin, the raw material composition preferably includes (D) a radical scavenger to control its reactivity.
The use of a radical scavenger is effective to increase the melt tension of the modified polypropylene resin.
That is, the radical scavenger is effective in obtaining a resin foam having a good appearance using a modified polypropylene resin.

Radical scavengers are capable of reacting with alkyl radical species.
The radical scavenger is preferably capable of binding to the aromatic vinyl monomer after binding to the alkyl radical.
Only one type of radical scavenger may be used, or two or more types may be used in combination.

  Examples of the radical scavenger include quinone compounds (quinones), naphthoquinone compounds (naphthoquinones), and phenothiazine compounds (phenothiazines).

Examples of the quinone compound include p-benzoquinone, p-naphthoquinone, 2-t-butyl-p-benzoquinone, and 2,5-diphenyl-p-benzoquinone. As said naphthoquinone compound, a 1, 4- naphthoquinone, 2-hydroxy 1, 4- naphthoquinone, a vitamin K etc. are mentioned.
Examples of the phenothiazine compound include phenothiazine, bis- (α-methylbenzyl) phenothiazine, 3,7-dioctylphenothiazine, and bis- (α-dimethylbenzyl) phenothiazine.

The content of the radical scavenger (D) in the raw material composition is preferably 0.005 parts by mass or more and 0.05 parts by mass or more with respect to 100 parts by mass of the (A) polypropylene resin. Is more preferred.
Moreover, it is preferable that content of the radical scavenger with respect to 100 mass parts of polypropylene resins is 1 mass part or less.
When the content of the radical scavenger is in the range as described above, the melt tension of the modified polypropylene resin is effectively increased, and the appearance of the extruded foam sheet is further improved.

  In addition to these, as the other component (E) to be contained in the raw material composition, various additives may be mentioned.

[(E) Additive]
The additive is suitably used according to various purposes, and is not particularly limited.
Specific examples of the additive include a weather resistant stabilizer, an antistatic agent, an antioxidant, a deodorant, a light stabilizer, a crystal nucleating agent, a pigment, a lubricant, and a purpose of imparting slip or antiblocking properties. Surfactants, inorganic fillers, and dispersibility improvers for improving the dispersibility of the inorganic fillers.
Examples of the dispersibility improver include higher fatty acids, higher fatty acid esters, and higher fatty acid amides.

The additive may be contained in the raw material composition before or during melt-kneading.
Further, the additive may be added after the melt-kneading to be contained in the modified polypropylene resin.
Only one type of additive may be used, or two or more types may be used in combination.

  The modified polypropylene-based resin according to the present embodiment can be easily obtained using a raw material composition containing the components as described above, and can be produced, for example, as follows.

(Method for producing modified polypropylene resin)
In the production of the modified polypropylene-based resin, for example, (A) 100 parts by mass of a polypropylene-based resin, (B) 0.1 parts by mass or more and 1.5 parts by mass or less of an organic peroxide, (C) aromatic vinyl The method of melt-kneading the raw material composition containing 0.1 mass part or more and 10 mass parts or less of monomers, and obtaining a modified polypropylene resin can be employ | adopted.
At the time of melt-kneading the raw material composition, it is preferable to control the heating temperature in order to bring the raw material composition into a good molten state.
The raw material composition reacts by heating at the time of melt kneading.
That is, the organic peroxide generates a radical by the heating, and the radical attacks the hydrogen bonded to the tertiary carbon of the polypropylene resin to form an alkyl radical.
In the state as it is, β-cleavage occurs to cause molecular cleavage of the polypropylene resin, but in the present embodiment, an aromatic vinyl monomer is bonded to the location to form a branched structure (crosslinked structure).

The aromatic vinyl monomer is preferably added to the obtained mixture after the polypropylene resin and the organic peroxide are mixed to obtain a mixture from the viewpoint of making the addition effect remarkable.
However, the polypropylene resin, the organic peroxide, and the aromatic vinyl monomer may be mixed together.
The radical scavenger may be added prior to the addition of the aromatic vinyl monomer, may be added after the addition of the aromatic vinyl monomer, or may be mixed with other components in a batch.
The additive may be added prior to the addition of the aromatic vinyl monomer, may be added after the addition of the aromatic vinyl monomer, and may be mixed together with other components.

Melt-kneading of a raw material composition can be implemented using general apparatuses, such as a kneader, a Banbury mixer, and an extruder.
When the raw material composition is melt-kneaded, it is preferable to use an extruder.
It is preferable that the raw material composition is supplied to the extruder and a crosslinking reaction is caused in the extruder to form the modified polypropylene resin, and at the same time, the modified polypropylene resin is extruded from the extruder.
By continuously feeding the raw material composition to the extruder and continuously extruding the modified polypropylene resin from the extruder, the modified polypropylene resin can be efficiently obtained.

Examples of the extruder include single-screw extruders and twin-screw extruders.
The said extruder can be used for manufacture of a modification | denaturation polypropylene-type resin as an extruder of the tandem type connected individually or in multiple numbers.
In particular, a twin-screw extruder is preferable from the viewpoint of further enhancing the dispersibility and reactivity of the other components with respect to the polypropylene resin as the base resin.

  When melt-kneading is performed using an extruder, an extruder provided with a vent mechanism is used to discharge VOCs such as residual monomers and thermal decomposition products before discharge of the melt-kneaded product using the vent mechanism. You may

In the method for producing a modified polypropylene-based resin of the present embodiment, after carbon dioxide and water are supplied to the extruder for melt-kneading, the kneaded product to which carbon dioxide and water are added is further melt-kneaded for a certain time By discharging the gas containing carbon and water from the kneaded material, the amount of VOC to be contained in the modified polypropylene resin can also be adjusted.
That is, in the method for producing a modified polypropylene resin, a polypropylene resin, an organic peroxide and an aromatic vinyl monomer are melt-kneaded to react the polypropylene resin and the aromatic vinyl monomer, thereby modifying the polypropylene resin. It is preferable to carry out a reaction step of producing a resin and a VOC removal step of removing VOC from the modified polypropylene resin obtained by melt-kneading in the reaction step.

The said VOC removal process does not need to be implemented in the form which follows a reaction process, and may be implemented, after discharging the modified polypropylene resin obtained by the reaction process from an extruder, and cooling once.
The VOC removal step carried out after the modified polypropylene resin is discharged from the extruder and cooled once may be carried out, for example, in the form of strands or sheets of modified polypropylene resin, and the strands or sheets are pelletized. It may be carried out on the pellet after the
For example, the VOC removal step can be carried out by reducing the pressure of the modified polypropylene resin pellet at room temperature or heating the modified polypropylene resin pellet.
The VOC removal step can also be carried out by heating the modified polypropylene-based resin pellet under a reduced pressure environment.

It is preferable that the said VOC removal process is implemented several times including the 1st process implemented continuously to a reaction process, and the 2nd process implemented after discharging | emitting from an extruder.
In the VOC removal step, preferably, the modified polypropylene-based resin obtained in the reaction step is subjected to a heat treatment to remove the VOC.
Here, in the second step, it is difficult to adopt temperature conditions equal to or higher than the melting point of the polypropylene-based resin in the sense of avoiding the prevention of fusion between the pellets and the strands.
Therefore, it is preferable that, for example, the temperature of the modified polypropylene-based resin be 90 ° C. or more and 150 ° C. or less.
The second step is more preferably performed such that the temperature of the modified polypropylene resin is 100 ° C. or more and 140 ° C. or less.
In the second step, the heat treatment at the above temperature is preferably performed for 0.5 hours or more.
The heat treatment time is preferably 12 hours or less.

As described above, in the second step, it is difficult to adopt temperature conditions higher than the melting point of the polypropylene-based resin, and the temperature of the modified polypropylene-based resin is reduced to below the melting point.
On the other hand, the first step is carried out under the condition that the temperature of the modified polypropylene resin is equal to or higher than the melting point, and is usually carried out in the state where the temperature of the modified polypropylene resin exceeds 150 ° C.
The first step is preferably carried out in a state where the temperature of the modified polypropylene resin is 250 ° C. or less.
As described above, since the temperature conditions are different between the first step and the second step, the VOCs to be mainly removed can be made different.
Specifically, in the second step, relatively low boiling point VOCs are removed, and in the first step, not only relatively low boiling point VOCs but also high boiling point VOCs are removed.
As described above, since the first step and the second step having different temperature conditions are performed, in the present embodiment, adjustment of the amount of VOC contained in the modified polypropylene-based resin used for producing the extruded foam sheet In addition, adjustment of components can be easily implemented.

It is preferable that the said VOC removal process is implemented so that the volatile organic compound (VOC) contained in modified polypropylene-type resin may be 1000 mg / kg or more and 10000 mg / kg or less.
That is, the VOC content of the modified polypropylene-based resin used for producing the extruded foam sheet is preferably 1000 mg / kg or more and 10000 mg / kg or less.
The VOC content is more preferably 1100 mg / kg or more, still more preferably 1200 mg / kg or more, and particularly preferably 1500 mg / kg or more.
The VOC content is more preferably 7000 mg / kg or less, still more preferably 5000 mg / kg or less.

In this embodiment, styrene is left in the modified polypropylene resin in the reaction step, and 100 mg / kg or more and 8000 mg / kg or less in the modified polypropylene resin after the VOC removal step is performed. It is preferable to leave styrene as a VOC in proportion.
That is, it is preferable that the modified polypropylene resin used for the production of the extruded foam sheet contains styrene at a rate of 100 mg / kg or more and 8000 mg / kg or less in a state in which volatilization removal is possible.
The styrene content is more preferably 500 mg / kg or more, still more preferably 700 mg / kg or more, and particularly preferably 800 mg / kg or more.
The styrene content is more preferably 6000 mg / kg or less, still more preferably 5000 mg / kg or less, and particularly preferably 4000 mg / kg or less.

  In the modified polypropylene-based resin used for producing the extruded foam sheet, the proportion of the styrene in the VOC is preferably 50% by mass or more and 90% by mass or less.

After the VOC removal step, an extrusion step of extruding and foaming the modified polypropylene resin composition containing the modified polypropylene resin having the adjusted VOC content is further carried out, and the modified polypropylene resin composition It is possible to produce an extruded foam sheet having a foam layer formed by
By producing the extruded foam sheet by such a production method, it is possible to produce an extruded foam sheet having a content of volatile organic compound (VOC) in the foam layer of 200 mg / kg or more and 4000 mg / kg or less.
Moreover, in the manufacturing method of the extrusion-foaming sheet in this embodiment, it can implement easily that VOC is adjusted so that it may become more suitable content.

The modified polypropylene resin composition used as a raw material of the extruded foam sheet in the extrusion step can contain a foaming agent and a cell regulator in addition to the modified polypropylene resin which is a base polymer.
Examples of the blowing agent include hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane and cyclopentane, and halides thereof, carbon dioxide gas and nitrogen.
Examples of the cell regulator include talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, Inorganic compound particles such as potassium sulfate, barium sulfate and glass beads, organic compound particles such as polytetrafluoroethylene, and the like can be mentioned.
Furthermore, azodicarbonamide which functions also as a thermal decomposition type foaming agent, sodium hydrogencarbonate, a mixture of sodium hydrogencarbonate and citric acid, and the like can be used as the above-mentioned cell regulator.
The cell regulator and the foaming agent need not be used alone, but may be used in combination of two or more.
One or more of the (E) additives as described above may be further added to the modified polypropylene resin composition.

The modified polypropylene resin composition does not have to be composed of one type of modified polypropylene resin and may contain two or more types of modified polypropylene resin as a base polymer.
The modified polypropylene resin composition may contain a resin other than the modified polypropylene resin.
As resins other than the modified polypropylene resin, resins excellent in compatibility with the modified polypropylene resin such as unmodified polypropylene resin and polyethylene resin are preferable.
The modified polypropylene resin composition may contain 60% by mass or more of the modified polypropylene resin when the total content of the modified polypropylene resin and the resin other than the modified polypropylene resin is 100% by mass. preferable.
The content of the modified polypropylene resin is more preferably 80% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more.
The resin to be contained in the modified polypropylene resin composition may be substantially only modified polypropylene resin.

  The modified polypropylene resin composition can be extruded and foamed using an extruder equipped with a circular die or a flat die.

In the extruded foam sheet produced in the extrusion step, a modified polypropylene-based resin that exhibits high melt tension as compared to a general polypropylene-based resin is adopted as a foam layer forming material, and the modified polypropylene is Since VOC is appropriately contained in the resin, it is possible to foam at a high magnification during extrusion foaming, and moreover, since the expansion of the cellular membrane becomes good, the closed cell property is excellent.
And the foam of the foam layer of the extrusion foam sheet obtained by this embodiment becomes a precise | minute structure, and exhibits the outstanding intensity | strength.

From such a thing, the extrusion-foaming sheet of this embodiment is excellent also in the moldability in thermoforming etc.
The extruded foam sheet is a thermoformed article (foamed resin molded article) which has excellent appearance following a molding die even when deep-drawn as in a cup container because the cells of the foam layer are dense. it can.

Examples of the thermoforming include vacuum forming, pressure forming, vacuum pressure forming, match molding and press forming.
A container is preferable as a specific foamed resin molded article produced by this thermoforming.
The foamed resin container produced in this manner is preferably used as various packaging containers because it is not only lightweight and high in strength but also easy to mass-produce.
Further, the foamed resin container is preferably used for food packaging because it is excellent in heat insulation and the like.
A nonwoven fabric, metal foil, decorative paper, a printing film, etc. may be laminated on the surface of the foamed resin molded article of the present embodiment according to the application.

The foamed resin molded article of the present invention can have various modes other than the above.
Further, in the present embodiment, the above-described examples are given for the extruded foam sheet and the modified polypropylene-based resin, but the present invention is not limited to the above examples.

  The present invention will be described in more detail by way of the following examples, but the present invention is not limited to these examples.

(Preparation of modified polypropylene resin)
(Production Example 1)
95% by mass of a first polypropylene-based resin (homopolypropylene resin, “PM600A” manufactured by Sun Aroma, MFR = 7.5 g / 10 min, density = 0.9 g / cm ³ ) and a second polypropylene-based resin (block polypropylene resin, 5% by mass of “PC684S” manufactured by Sun Aroma Co., Ltd., MFR = 7.5 g / 10 min, density = 0.9 g / cm ³ ) and 100 parts by mass of these polypropylene resins t-butylperoxyisopropyl carbonate (chemical 0.70 parts by mass of “Kayacaron BIC-75” manufactured by Akzo Co., Ltd., half-life temperature: 156 ° C., 1 minute is mixed by a screw feeder, and the obtained mixture is subjected to a twin screw extruder having a bore diameter of 41 mm 42), and using a liquid injection pump from the middle of the twin-screw extruder, the styrene monomer The resin was supplied so that the ratio to 100 parts by mass of the epoxy resin was 2.5 parts by mass.
The temperature from the feed part of the twin-screw extruder to the styrene injection position is set at 170 ° C, the temperature thereafter is set at 230 ° C, and the pressure inside the extruder is -0.094 kPa reduced from the vent part in the middle of the twin-screw extruder The raw material composition was melt-kneaded in a twin-screw extruder under the conditions of a rotational speed of 135 rpm, and the polypropylene-based resin and styrene were reacted by the melt-kneading to produce a modified polypropylene-based resin.
The modified polypropylene resin was extruded in the form of a strand with a discharge amount of 45 kg / h from a die with a bore of 2 mm, a land of 11 mm and a hole number of 9 attached to the tip of an extruder.
Next, the extruded strand-like modified polypropylene resin was passed through a cooling water tank containing water at 30 ° C. to solidify by cooling.
The cooled strand-like modified polypropylene resin was cut with a pelletizer to obtain pellets of the modified polypropylene resin.
Thereafter, the pellets were placed in a hot air drier (Matsui Seisakusho, HD 2-200D-J), and heat treatment (VOC removal step) was performed at 120 ° C. for 9 hours.
The VOC content of the modified polypropylene-based resin after partial removal of VOC by heat treatment was 41 mg / kg (the content of which is styrene: 3 mg / kg).

(Production Example 2-9)
A modified polypropylene-based resin was prepared in the same manner as in Production Example 1 except that the blend ratio of the polypropylene resin, the organic peroxide, and the aromatic vinyl monomer, the extrusion conditions, and the heat treatment conditions were changed as described in Table 1 below. Manufactured.

Example 1
100 parts by mass of the modified polypropylene-based resin described in Production Example 8 (code of modified polypropylene-based resin: H) and 0.2 parts by mass of a cell regulator ("Finecell master HCPO410K" manufactured by Dainichi Seika Kogyo Co., Ltd.) Dry blending gave a mixture.
The mixture is supplied to the first extruder through a hopper using a tandem extruder in which a second extruder having a bore diameter of 65 mm is connected to the downstream side of the first extruder having a bore diameter of 50 mm, the mixture in the first extruder The mixture was heated and melted and kneaded.
Thereafter, butane (isobutane / normal butane = 70/30) was injected into the first extruder as a foaming agent, and the mixture was melt-kneaded with the mixture.
Next, the melt-kneaded product is transferred to a second extruder and uniformly cooled to a temperature suitable for extrusion foaming, and then extrusion foaming is carried out from a cylindrical die with a diameter of 60 mm at a discharge rate of 30 kg / hour to obtain cylindrical foam I got
The resulting cylindrical foam is placed on a 170 mm diameter mandrel cooled by water at approximately 20 ° C. inside, and the outer surface is cooled and molded by blowing air with an air ring larger than the diameter, and a circle is formed. At one point on the circumference, it was cut with a cutter to obtain a band-like extruded foam sheet.
As described above, the extruded foam sheet obtained here has a single layer structure constituted by only a single foam layer.
The properties of the extruded foam sheet (foam layer), the results of evaluation of the tensile test and the bending test are shown in Table 2.

(Examples 2 to 6, Comparative Examples 1 to 2)
An extruded foam sheet was produced and evaluated in the same manner as in Example 1 using the modified polypropylene resin described in Table 2.
The results are shown in Table 2.

(Reference Example 1)
A commercially available high melt tension polypropylene resin ("WB140 HMS" manufactured by Borealis, MFR = 2.1 g / 10 min, density = 0.9 g / cm ³ , VOC content = 694 mg / kg, styrene content = 18 mg / kg) is used. Then, in the same manner as in Example 1, an extruded foam sheet was produced and evaluated.
The results are shown in Table 2.

(Evaluation method)
The specific evaluation method regarding the extruded foam sheet is as follows.

(Open cell rate)
A plurality of 25 mm long × 25 mm wide sheet-like samples were cut out from the extruded foam sheet, and the cut out samples were stacked so as not to leave a space, and test pieces were obtained with a thickness of 25 mm.
The outer dimensions of the obtained test piece were measured to 1/100 mm using “Digimatic Caliper” calipers manufactured by Mitutoyo Corp., and the apparent volume (V1: cm ³ ) was determined.
Next, the volume (V2: cm < ³ >) of the test piece was calculated | required by the 1-1 / 2-1 atmospheric pressure method using Tokyo Science Co., Ltd. "1000 type" air comparison type hydrometer.
The open cell rate (%) was calculated by the following equation, and the average value of the open cell rates of the five test pieces was determined.
The test pieces are adjusted in advance under the condition of JIS K 7100: 1999 symbol “23/50” (temperature 23 ± 2 ° C., relative humidity 50 ± 5%) under a second grade standard atmosphere for 24 hours or more, and then the same. It measured in standard atmosphere.
The air comparison type hydrometer was corrected with a standard ball (large 28.96 cm ³ , small 8.58 cm ³ ).

Open cell rate (%) = (V1-V2) / V1 × 100

(V1: apparent volume measured with vernier calipers, V2: volume measured with air comparison type hydrometer)

(VOC measurement of modified polypropylene resin and extruded foam sheet (foam layer))
In the measurement of VOC, pellets of the modified polypropylene resin and extruded foam sheet are sealed in a polypropylene container (made by As One Corporation, trade name: I-Boy) within one month after preparation for the purpose of prevention of contamination, and analysis It was stored at room temperature 20 ° C. until it was performed and used as a sample.

About 3 mg of the sample was precisely weighed in a GLT tube, set in a “TD-4 J type” autosampler manufactured by LCI Science Co., Ltd., and heated for 3 minutes at 250 ° C. The generated volatile component was kept at −40 ° C. Concentrated cold trap into parts.

After that, thermal desorption was performed to perform GC / MS measurement.
The GC / MS measurement conditions are as shown below, and all peaks detected between the peak retention times of n-hexane and n-hexadecane were quantified in terms of toluene from the obtained chromatogram.
However, the peak of about 0.1 mg / kg or more was targeted for quantification, and the sum of the quantified values was defined as the VOC content.
The VOC content was calculated from the following equation using one inspection line obtained by similarly injecting 1 μL of a 1000 ppm toluene standard solution into a GLT tube and measuring the same.

VOC content (mg / kg) = (area value of each component / area value of 1 μg of toluene) / sample weight (g)

Moreover, styrene content was computed by the following formula.

Styrene content (mg / kg) =
(Area value of 1 μg × styrene / area value of 1 μg of toluene) / sample mass (g)

[GC / MS measurement conditions]
measuring device:
"JMS-Q1000 GCM kII" mass spectrometer manufactured by Nippon Denshi Co., Ltd. "7890A" gas chromatograph column manufactured by Agilent Technologies Ltd .:
Phenomenex “ZB-1” capillary column (1.0 μm × 0.25 mmφ × 60 m)

[GC oven temperature rise conditions]
Initial temperature: 40 ° C (hold for 3 min)
First stage temperature rising rate: 15 ° C / min (up to 200 ° C)
Second stage heating rate: 25 ° C / min (up to 250 ° C)
Final temperature: 250 ° C (6.33 min)
Carrier gas: He
He flow rate: 1 mL / min
Inlet temperature: 250 ° C
Interface temperature: 250 ° C
Detector voltage: -1021V
Split ratio: 1/50
Ion source temperature: 250 ° C
Ionization current: 300 uA
Ionization energy: 70 eV
Detection method: Scanning method (m / z = 40-400)

[Thermal desorption conditions]
apparatus:
LCI Science Co., Ltd. “TD-4J” Thermal Desorber Thermal Desorption P & T Conditions:
PurgeTime: 10s
InjectTime: 20s
DesorbTime: 300s
DelayStartTime: 10s
DesorbHeater: 250 ° C
CryoTempHeating: 200 ° C
CryoTempCooling: -40 ° C

(Apparent density of extruded foam sheet (foam layer))
The apparent density of the extruded foam sheet was measured by the method described in JIS K 7222: 1999 "foamed plastic and rubber-measurement of apparent density".
Specifically, it was measured by the following method.
A sample of 100 cm ³ or more is prepared from the extruded foam sheet, and this sample is conditioned for 16 hours in a class 2 environment under the symbol 23/50 of JIS K 7100: 1999, then its size and mass are measured to determine apparent density Calculated by the following equation.

Apparent density (g / cm ³ ) = mass of sample (g) / volume of sample (cm ³ )

(Average bubble diameter)
A cross section (hereinafter, MD cross section) in which the extruded foam sheet is cut along a plane (arrow 1 in FIG. 3) which is parallel to the MD direction (extrusion direction) from the center in the width direction of the extruded foam sheet and perpendicular to the surface of the extruded foam sheet. And the extruded foam sheet cut along a plane (arrow 2 in FIG. 3) parallel to the TD direction (direction orthogonal to the extrusion direction on the surface of the extruded foam sheet) and perpendicular to the surface of the extruded foam sheet Each cross section (hereinafter, referred to as a TD cross section) was photographed at a magnification of 18 times with “SU1510” scanning electron microscope (SEM) manufactured by Hitachi High-Technologies Corporation.
For each of the MD cross section and the TD cross section, microscopic images of a total of 4 fields of view were taken, 2 fields of view.
For each of the two images of the MD cross section, 30 bubbles were arbitrarily selected, and using a length measurement function of the SEM control software, the location where the bubble diameter was the longest in the MD direction was measured.
The lengths of the bubbles measured for each of the two images were arithmetically averaged to obtain a bubble diameter D _MD in the MD direction.
For each of the two images of the TD cross section, 30 air bubbles were arbitrarily selected, and the length of the air bubble in the TD direction was measured in the TD direction using the length measurement function of the SEM control software.
The bubble length measured for each of the two images was arithmetically averaged to obtain a bubble diameter D _TD in the TD direction.
For each of one image of the MD cross section and one image of the TD cross section, select 30 bubbles arbitrarily, and use the length measurement function of the SEM control software to make a direction orthogonal to each of the MD and TD directions (VD ) Was measured where the bubble diameter was the longest.
The lengths of the bubbles measured for each of the two images were arithmetically averaged to obtain the bubble diameter D _VD in the VD direction.
The average bubble diameter was calculated by the following equation.

Average bubble diameter (μm) = (D _MD × D _TD × D _V D) ^1/3

D _MD : bubble diameter in the MD direction (μm)
D _TD : Bubble diameter in the TD direction (μm)
D _VD : Bubble diameter in the VD direction (μm)

The maximum point elongation rate and the elongation at break of the tensile test were measured in accordance with the method described in JIS K6767: 1999 “Foam plastic-polyethylene-test method”.
Measurement is load cell rating 1000 N, range 20%, breakage detection sensitivity using “TENSILON UCT-10T” universal testing machine manufactured by ORIENTEC Co., Ltd. and “UTPS-458X” universal testing machine data processing manufactured by Softbrain Co., Ltd. It implemented on the conditions of 0.5 fs% and 500 mm / min of tensile velocity, and the clamp distance was 100 mm.
In the measurement, a dumbbell-shaped type 1 (ISO 1798 standard) and a foam sheet punched out with the flow direction (MD direction: extrusion direction) of the foam sheet as the longitudinal direction were used as test pieces.
Maximum point elongation was calculated from the distance between the jaws before testing and when the maximum point load was reached.
The elongation at break was calculated from the distance between the jaws before testing and at the time of cutting.
The minimum number of test pieces was five.
The test pieces are conditioned under the conditions of JIS K 7100: 1999 symbol “23/50” (temperature 23 ° C., relative humidity 50%), under a standard atmosphere of class 2 for 24 hours or more, and then measured under the same standard atmosphere Did.
The maximum point elongation rate and the elongation at break point were calculated by the following equations.

E ₁ = 100 × (L ₁ −L ₀ ) / L ₀

E ₁ : Maximum point elongation rate (%)
L ₀ : Distance between jaws before test (mm)
L ₁ : Distance between jaws when maximum point load is reached (mm)

E ₂ = 100 × (L ₂ −L ₀ ) / L ₀

E ₂ : Elongation at break (%)
L ₀ : Distance between jaws before test (mm)
L ₂ : Distance between clamps at cutting (mm)

(Bending test)
The maximum point deflection of the bending test was measured by the method described in JIS K7171-1: 2008 "Plastic-Test method of bending characteristics".
The measurement is carried out using “TENSILON UCT-10T” universal testing machine manufactured by ORIENTEC Co., Ltd. and “UTPS-458X” universal testing machine data processing manufactured by Softbrain Co., Ltd. Load cell rating 50 N, range 20%, breakage detection sensitivity 1 fs It implemented on% conditions.
The test piece used the thing of width 25 mm x length 40 mm by making the flow direction (MD direction: extrusion direction) of a foam sheet into a longitudinal direction.
Using the test piece, a bending test was performed at a compression speed of 1 mm / min, a pressure wedge 5R, and a support base 2R with a distance between supporting points of 32 mm.
The minimum number of test pieces was five.
The measurement is performed after conditioning the test piece under the standard atmosphere of a standard of class 2 with a symbol “23/50” (temperature 23 ± 2 ° C., relative humidity 50 ± 5%) of JIS K 7100: 1999, and then the same. Conducted under a standard atmosphere.
The origin of displacement was taken as the return point, and the displacement from the origin when the maximum load was reached was taken as the maximum point deflection (mm).

  From the above, it can be seen that according to the present invention, an extruded foam sheet having fine cells and excellent strength can be obtained, and a foamed resin molded article excellent in lightness and strength can be obtained.

  1: Extruded foam sheet 10: Foam layer 20, 20 ': non-foam layer

Claims (7)

An extruded foam sheet having a foam layer formed of a modified polypropylene resin composition containing a modified polypropylene resin,
The modified polypropylene-based resin is a reaction product of a polypropylene-based resin, an organic peroxide, and an aromatic vinyl monomer,
The extrusion foam sheet whose content of the volatile organic compound (VOC) in the said foam layer is 200 mg / kg or more and 4000 mg / kg or less.   The extruded foam sheet according to claim 1, wherein the aromatic vinyl monomer is styrene. The volatile organic compound (VOC) contains styrene,
The extruded foam sheet according to claim 1 or 2, wherein a content of styrene in the foam layer is 35 mg / kg or more and 800 mg / kg or less.   The extruded foam sheet according to any one of claims 1 to 3, wherein the open cell ratio of the foam layer is 40% or less. A foamed resin molded article which is partially or entirely constituted by a thermoformed article, and the thermoformed article is constituted by an extruded foam sheet,
A foamed resin molded article, wherein the thermoformed article is formed of the extruded foam sheet according to any one of claims 1 to 4. A reaction step of producing a modified polypropylene resin by reacting a polypropylene resin, an organic peroxide, and an aromatic vinyl monomer by melt-kneading;
The modified polypropylene-based resin obtained in the reaction step is subjected to heat treatment to remove part of volatile organic compounds (VOC) contained in the modified polypropylene-based resin, and the volatile organic compounds ( Implement a VOC removal process to reduce the content of VOCs to 1000 mg / kg or more and 10000 mg / kg or less,
The foam layer formed of the modified polypropylene resin composition is further implemented by extruding an extrusion step of extrusion foaming the modified polypropylene resin composition containing the modified polypropylene resin in which the VOC removal step is performed. The manufacturing method of the extrusion foaming sheet which manufactures the extrusion foaming sheet which it has. Styrene is used as the aromatic vinyl monomer,
In the reaction step, styrene is left in the modified polypropylene-based resin,
The method for producing an extruded foam sheet according to claim 6, wherein styrene is left at a ratio of 100 mg / kg or more and 8000 mg / kg or less in the modified polypropylene resin after the VOC removal step is performed.

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