WO2022149538A1

WO2022149538A1 - Polypropylene resin foam particles and polypropylene resin foam molded article

Info

Publication number: WO2022149538A1
Application number: PCT/JP2021/048735
Authority: WO
Inventors: 豊松宮
Original assignee: 株式会社カネカ
Priority date: 2021-01-08
Filing date: 2021-12-28
Publication date: 2022-07-14
Also published as: CN116783240A; JPWO2022149538A1

Abstract

The present invention addresses the problem of providing polypropylene resin foam particles that (a) can provide a polypropylene resin foam molded article that exhibits almost no post-molding shrinkage or deformation, and (b) exhibit excellent foaming characteristics. The polypropylene resin foam particles contain prescribed amounts of: a polypropylene resin; a copolymer containing an acrylonitrile unit and a styrenic unit; and a hydrogenated styrenic copolymer.

Description

Polypropylene resin foam particles and polypropylene resin foam molded products

The present invention relates to polypropylene-based resin foamed particles and polypropylene-based resin foamed molded article.

Polypropylene resin foam molded products are used for various purposes such as automobile interior members, core materials for automobile bumpers, heat insulating materials, cushioning packaging materials, and returnable boxes.

By the way, since the polypropylene-based resin is a crystalline thermoplastic resin, the polypropylene-based resin foamed molded product obtained by molding the polypropylene-based resin foamed particles is compared with the non-crystalline thermoplastic resin such as polystyrene after molding. Shrinkage is large. Therefore, in particular, when integrally molding another material such as metal (in the case of insert molding), the metal member may be deformed due to the shrinkage of the polypropylene-based resin foam molded body after molding. That is, in the prior art, it has been difficult to control the dimensions and / or shape of the polypropylene-based resin foam molded product when integrally molding other materials such as metal.

As a method of controlling shrinkage of a polypropylene-based resin foam molded product after molding, a method of mixing an amorphous thermoplastic resin with a polypropylene-based resin and using it is known.

For example, Patent Document 1 discloses a technique in which a polypropylene-based resin, an amorphous thermoplastic resin, and a compatibilizer are mixed and used.

Patent Document 2 discloses a technique in which a polypropylene-based resin is mixed with a polystyrene-based resin and a polymer mainly composed of a vinyl aromatic compound.

Japanese Patent Publication No. 2001-302837 Japanese Patent Publication No. 6-100740

In view of the above circumstances, an object of the embodiment of the present invention is to provide a polypropylene-based resin foam molded product having (a) almost no shrinkage and deformation after molding, and (b) polypropylene having excellent foamability. The purpose is to provide foamed resin particles.

The present inventors have completed the present invention as a result of diligent studies to solve the above-mentioned problems.

That is, the polypropylene-based resin foamed particles according to the embodiment of the present invention include 100 parts by weight of the polypropylene-based resin, 5 parts by weight to 60 parts by weight of the polymer containing the acrylonitrile unit and the styrene-based unit, and the hydrogenated styrene-based particles. Includes 3.0 parts by weight to 30.0 parts by weight of the polymer.

Further, the method for producing polypropylene-based resin foamed particles according to one embodiment of the present invention includes a foaming step of foaming polypropylene-based resin particles, and the polypropylene-based resin particles are 100 parts by weight of polypropylene-based resin and acrylonitrile. It contains 5 parts by weight to 60 parts by weight of the copolymer including the unit and the styrene-based unit, and 3.0 parts by weight to 30.0 parts by weight of the hydrogenated styrene-based copolymer.

According to one embodiment of the present invention, it is possible to provide (a) a polypropylene-based resin foam molded product having almost no shrinkage and deformation after molding, and (b) to provide polypropylene-based resin foamed particles having excellent foamability. It works.

FIG. 1 is a schematic view of a foam molded product 100 used for evaluating the amount of deformation.

An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications can be made within the scope of the claims. The technical scope of the present invention also includes embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples. Further, by combining the technical means disclosed in each embodiment, new technical features can be formed. In addition, all the academic documents and patent documents described in the present specification are incorporated as references in the present specification. Further, unless otherwise specified in the present specification, "A to B" representing a numerical range is intended to be "A or more (including A and larger than A) and B or less (including B and smaller than B)".

Further, unless otherwise specified in the present specification, as structural units, a structural unit derived from an X ¹ monomer, a structural unit derived from an X ² monomer, ... And an X ⁿ monomer (n is A copolymer containing (an integer of 2 or more) is also referred to as "X ¹ / X ² / ... / X ⁿ copolymer". Unless otherwise specified, the X ¹ / X ² / ... / X ⁿ copolymer is not particularly limited in the polymerization mode, and may be a random copolymer or a block copolymer. It may be a graft copolymer or a graft copolymer.

Further, in the present specification, the structural unit derived from the X monomer contained in the polymer or the copolymer may be referred to as "X unit".

[1. Polypropylene resin foam particles]
The polypropylene-based resin foamed particles according to the embodiment of the present invention include 100 parts by weight of a polypropylene-based resin, 5 to 60 parts by weight of a copolymer containing an acrylonitrile unit and a styrene-based unit, and a hydrogenated styrene-based copolymer. Includes 3.0 parts by weight to 30.0 parts by weight.

The polypropylene-based resin foamed particles according to the embodiment of the present invention can be molded by a known method to provide a polypropylene-based resin foamed molded product.

In the present specification, "polypropylene resin foamed particles" may be referred to as "foamed particles", and "polypropylene resin foamed particles according to one embodiment of the present invention" may be referred to as "present foamed particles". The "polypropylene resin foam molded body" may be referred to as a "foam molded body".

Since the polypropylene-based resin foamed particles according to the embodiment of the present invention have the above-mentioned constitution, it is possible to provide (a) a polypropylene-based resin foamed molded product having almost no shrinkage and deformation after molding, and (b) to be foamable. It has the advantage of being excellent. It can be said that the polypropylene-based resin foamed particles according to the embodiment of the present invention can provide a polypropylene-based resin foamed molded product in which shrinkage and deformation after molding are reduced as compared with the conventional product. In the present specification, reducing the shrinkage of the foamed molded product after molding is also referred to as being excellent in shrinkage.

In the present specification, the polypropylene-based resin is intended to be a resin containing 75 mol% or more of structural units derived from a propylene monomer in 100 mol% of all structural units contained in the resin. In the present specification, "structural unit derived from propylene monomer" may be referred to as "propylene unit".

(Polypropylene resin)
The polypropylene-based resin may be (a) a homopolymer of propylene, or (b) a block copolymer of propylene and a monomer other than propylene, a random copolymer, or a graft copolymer. It may be well, or (c) a mixture of two or more of these.

The polypropylene-based resin may have one or more structural units derived from a monomer other than the propylene monomer in addition to the propylene unit, or may have one or more. The "monomer other than the propylene monomer" used in the production of polypropylene-based resin may be referred to as "comonomer". The "structural unit derived from a monomer other than the propylene monomer" contained in the polypropylene resin may be referred to as a "comonomer unit".

Examples of comonomers include ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene, 1-heptene, Examples thereof include α-olefins having 2 or 4 to 12 carbon atoms such as 3-methyl-1-hexene, 1-octene and 1-decene.

Specific examples of the polypropylene-based resin include polypropylene homopolymers, ethylene / propylene random copolymers, 1-butene / propylene random copolymers, 1-butene / ethylene / propylene random copolymers, and ethylene / propylene block copolymer weights. Examples thereof include coalescence, 1-butene / propylene block copolymer, propylene / chlorinated vinyl copolymer, propylene / maleic anhydride copolymer, styrene-modified polypropylene-based resin and the like. As the polypropylene-based resin, one of these may be used alone, or two or more thereof may be used in combination. Among these, the ethylene / propylene random copolymer and the 1-butene / ethylene / propylene random copolymer have good foamability in the obtained foamed particles, and the present molded product has good formability. It is suitable because of its possession. The 1-butene is synonymous with butene-1.

Consider the case where an ethylene / propylene random copolymer or a 1-butene / ethylene / propylene random copolymer is used as the polypropylene-based resin (case A). In Case A, the ethylene content in the ethylene / propylene random copolymer or the 1-butene / ethylene / propylene random copolymer is 0.2% by weight to 10.0% by weight in 100% by weight of each copolymer. Is preferable. The ethylene content can also be said to be the content of structural units (ethylene units) derived from ethylene. When the content of ethylene units in the ethylene / propylene random copolymer or 1-butene / ethylene / propylene random copolymer is (i) 0.2% by weight or more, the foamed particles in the production of the present foamed particles The foamability and / or the formability of the obtained foamed particles tends to be good, and when (ii) 10.0% by weight or less, the mechanical properties of the foamed molded product obtained from the present foamed particles are deteriorated. There is no fear.

Further, in Case A, the 1-butene content in the 1-butene / ethylene / propylene random copolymer is preferably 0.2% by weight to 10.0% by weight based on 100% by weight of the copolymer. The 1-butene content can also be said to be the content of the constituent units (1-butene units) derived from 1-butene. When the content of 1-butene units in the 1-butene / ethylene / propylene random copolymer is (i) 0.2% by weight or more, the foamability of the foamed particles in the production of the present foamed particles and / or The moldability of the obtained foamed particles tends to be good, and when (ii) 10.0% by weight or less, there is no possibility that the mechanical properties of the foamed molded product obtained from the present foamed particles are deteriorated.

Further, in Case A, the total content of the ethylene unit and the 1-butene unit in the 1-butene / ethylene / propylene random copolymer is 0 in 100% by weight of the 1-butene / ethylene / propylene random copolymer. It is preferably 5.5% by weight to 10.0% by weight. When the total content of ethylene units and 1-butene units in the 1-butene / ethylene / propylene random copolymer is (i) 0.5% by weight or more, the foamability of the foamed particles in the production of the foamed particles is (i). And / or the formability of the obtained foamed particles tends to be good, and (ii) when it is 10.0% by weight or less, there is a possibility that the mechanical properties of the foamed molded product obtained from the present foamed particles are deteriorated. do not have.

The melting point of the polypropylene resin is preferably 135.0 ° C to 160.0 ° C, more preferably 138.0 ° C to 158.0 ° C, more preferably 140.0 ° C to 156.0 ° C, and more preferably 143.0 ° C. ~ 154.0 ° C. is more preferable, 145.0 ° C. to 152.0 ° C. is further preferable, and 148.0 ° C. to 150.0 ° C. is particularly preferable. When the melting point of the polypropylene-based resin is (i) 135.0 ° C. or higher, the foamed molded product obtained from the foamed particles has excellent heat resistance, and when (ii) 160.0 ° C. or lower, the book In the production of foamed particles, it becomes easy to increase the foaming ratio of the foamed particles.

In the present specification, the melting point of the polypropylene resin is a value obtained by measuring by the differential scanning calorimetry method (hereinafter referred to as "DSC method"). The specific operation procedure is as follows: (1) By raising the temperature of the polypropylene resin 5 mg to 6 mg from 40.0 ° C to 220.0 ° C at a heating rate of 10.0 ° C / min. The polypropylene-based resin is melted; (2) Then, the temperature of the melted polypropylene-based resin is lowered from 220.0 ° C. to 40.0 ° C. at a temperature lowering rate of 10.0 ° C./min to cause the polypropylene-based resin. (3) Then, the temperature of the crystallized polypropylene-based resin is further raised from 40.0 ° C. to 220.0 ° C. at a heating rate of 10 ° C./min. The temperature of the peak (melting peak) of the DSC curve of the polypropylene-based resin obtained at the time of the second temperature rise (that is, at the time of (3)) can be obtained as the melting point of the polypropylene-based resin. When there are a plurality of peaks (melting peaks) in the DSC curve of the polypropylene resin obtained at the time of the second temperature rise by the above method, the temperature of the peak (melting peak) having the maximum heat of fusion is set to polypropylene. Let it be the melting point of the system resin. As the differential scanning calorimeter, for example, a DSC6200 type manufactured by Seiko Instruments Co., Ltd. can be used.

The melt flow rate (MFR) of the polypropylene resin is not particularly limited, but is preferably 3.0 g / 10 minutes to 30.0 g / 10 minutes, more preferably 4.0 g / 10 minutes to 20.0 g / 10 minutes. , 5.0 g / 10 minutes to 15.0 g / 10 minutes are more preferable, and 6.0 g / 10 minutes to 13.0 g / 10 minutes are particularly preferable. The MFR may be referred to as "melt index (MI)".

When the MFR of the polypropylene resin is 3 g / 10 minutes or more, it tends to be easy to increase the foaming ratio of the foamed particles in the production of the foamed particles. When the MFR of the polypropylene resin is 30 g / 10 minutes or less, there is no possibility that the bubbles of the obtained foamed particles are communicated with each other, and as a result, (i) the compressive strength of the foamed molded product obtained from the present foamed particles is good. Or (ii) the surface property of the foamed molded product tends to be good.

In the present specification, the MFR value of the polypropylene-based resin is a value obtained by measuring under the following conditions using the MFR measuring instrument described in JIS K7210: 1999: Orifice diameter 2.0959 ±. 0.005 mmφ, orifice length 8,000 ± 0.025 mm, load 2.16 kgf, temperature 230 ° C (230 ± 0.2 ° C).

Polypropylene resin can be obtained by a known method. The polymerization catalyst for synthesizing the polypropylene-based resin is not particularly limited, and for example, a Ziegler-based catalyst, a metallocene catalyst, or the like can be used.

(Copolymer containing acrylonitrile unit and styrene-based unit)
The foamed particles contain 5 to 60 parts by weight of a copolymer containing an acrylonitrile unit and a styrene-based unit with respect to 100 parts by weight of the polypropylene-based resin. By having the above-mentioned structure, the present foamed particles have an advantage that foamed particles having excellent foamability can be obtained, and a foamed molded product having further reduced shrinkage and deformation after molding as compared with the conventional product can be obtained. In the present specification, "a copolymer containing an acrylonitrile unit and a styrene-based unit" may be referred to as an "AS copolymer". The AS copolymer is an amorphous resin.

In the present specification, the AS copolymer is a copolymer containing at least 50 mol% or more of structural units derived from acrylonitrile units or styrene-based units in 100 mol% of all structural units contained in the AS copolymer. Intended for polymers. The AS copolymer is not particularly limited as long as it is a copolymer containing 50 mol% or more of a constituent unit containing at least an acrylonitrile unit and a styrene-based unit, and is, for example, (a) a block copolymer, a random copolymer or a copolymer. It may be a graft copolymer, or (b) a mixture of two or more of these.

The styrene-based unit contained in the AS copolymer is a structural unit derived from the styrene-based monomer. Examples of the styrene-based monomer include (a) styrene, and (b) α-methylstyrene, p-methylstyrene, m-methylstyrene, о-methylstyrene, 2,4-dimethylstyrene, p-. Examples thereof include styrene-based derivatives such as ethyl styrene, m-ethyl styrene, о-ethyl styrene, t-butyl styrene, and chlorstyrene. These styrene-based monomers may be used alone or in combination of two or more. That is, the styrene-based unit contained in the AS copolymer may be one kind or a combination of two or more kinds.

The styrene-based unit contained in the AS copolymer preferably contains an α-methylstyrene unit. The amount of α-methylstyrene unit in the styrene-based unit contained in the AS polymer is preferably 70% by weight or more, preferably 80% by weight or more, based on 100% by weight of the styrene-based unit contained in the AS polymer. Is more preferable, 90% by weight or more is further preferable, 95% by weight or more is particularly preferable, and 100% by weight is most preferable. That is, the styrene-based unit contained in the AS copolymer is most preferably α-methylstyrene unit. The larger the amount of α-methylstyrene unit in the styrene-based unit contained in the AS copolymer, the more the obtained foamed particles can provide (a) a polypropylene-based resin foamed molded product having almost no shrinkage and deformation after molding. (B) It has the advantage of being excellent in foamability.

The amount of the styrene-based unit contained in the AS copolymer (hereinafter, may be referred to as “styrene-based content”) is preferably 20% by weight to 95% by weight in 100% by weight of the AS copolymer. , 50% by weight to 90% by weight, more preferably 55% by weight to 85% by weight, further preferably 60% by weight to 80% by weight, and 65% by weight to 75% by weight. % Is particularly preferable. According to this configuration, there is an advantage that an AS copolymer having good productivity and excellent heat resistance can be obtained.

The amount of α-methylstyrene unit as a styrene-based unit contained in the AS copolymer (hereinafter, may be referred to as “α-methylstyrene content”) is 20% by weight in 100% by weight of the AS copolymer. It is preferably ~ 95% by weight, more preferably 50% by weight to 90% by weight, further preferably 55% by weight to 85% by weight, still more preferably 60% by weight to 80% by weight. It is more preferably 65% by weight to 75% by weight, and particularly preferably 65% by weight. According to this configuration, there is an advantage that an AS copolymer having good productivity and excellent heat resistance can be obtained.

The AS copolymer may have a structural unit other than the acrylonitrile unit and the styrene-based unit (hereinafter, may be referred to as "constituent unit other than AS"). The constituent units other than AS include vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid esters such as methyl acrylate and ethyl acrylate; methacrylic esters such as methyl methacrylate and ethyl methacrylate; and ethylene and propylene. Examples thereof include monomers other than the above-mentioned monomers copolymerizable with olefins; maleic anhydride; vinyl chloride; vinylidene chloride; and acrylonitrile units and / or styrene-based units. Since the heat resistance of the AS copolymer is good, the amount of the constituent units other than AS contained in the AS copolymer is preferably 10% by weight or less, preferably 5% by weight or less, based on 100% by weight of the AS copolymer. More preferably, 1% by weight or less is further preferable, and 0% by weight is particularly preferable. That is, it is particularly preferable that the AS copolymer is a copolymer composed of an acrylonitrile unit and a styrene-based unit.

Specific examples of the AS copolymer include acrylonitrile / styrene copolymer, acrylonitrile / α-methylstyrene copolymer, acrylonitrile / p-methylstyrene copolymer, acrylonitrile / m-methylstyrene copolymer, and acrylonitrile / о. -Methylstyrene copolymer, acrylonitrile / 2,4-dimethylstyrene copolymer, acrylonitrile / p-ethylstyrene copolymer, acrylonitrile / m-ethylstyrene copolymer, acrylonitrile / о-ethylstyrene copolymer, acrylonitrile Examples thereof include / t-butylstyrene copolymer and acrylonitrile / chlorstyrene copolymer. Among the above-mentioned copolymers, acrylonitrile / α-methylstyrene copolymer is preferable because it has an advantage that foamed particles having excellent foamability can be obtained. Only one kind of these AS copolymers may be used, or two or more kinds thereof may be used in combination.

The glass transition temperature (sometimes referred to as “Tg”) of the AS copolymer is not particularly limited, but is preferably 95 ° C to 140 ° C, more preferably 100 ° C to 135 ° C, and preferably 103 ° C to 130 ° C. More preferably, 105 ° C to 125 ° C is particularly preferable. When the Tg of the AS copolymer is (i) 95 ° C. or higher, it has an advantage that foamed particles having excellent heat resistance and a foamed molded product can be obtained, and when it is (ii) 140 ° C. or lower, it has an advantage. Effervescent particles with a low open cell ratio can be obtained.

In the present specification, the Tg of the AS copolymer is a value obtained by measuring according to JIS-K-7121 using a differential scanning calorimeter [DSC6200 type manufactured by Seiko Instruments Co., Ltd.]. The specific operation procedure is as follows (1) to (5): (1) Weigh 5 mg of the AS polymer; (2) In a nitrogen atmosphere, the temperature of the AS polymer is set to 10 The temperature is raised from room temperature to 250 ° C. at ° C./min; (3) the temperature of the heated AS copolymer is lowered from 250 ° C. to room temperature at 10 ° C./min; (4) again of the AS copolymer. The temperature is raised from room temperature to 250 ° C. at 10 ° C./min; (5) the peak (melting peak) of the DSC curve of the AS polymer obtained at the time of the second temperature rise (that is, at the time of (4)). Let the temperature of be taken as Tg of the AS copolymer.

The MFR of the AS copolymer is not particularly limited, but is preferably 2.0 g / 10 minutes to 15.0 g / 10 minutes, more preferably 3.0 g / 10 minutes to 12.0 g / 10 minutes, and 4.0 g. It is more preferably / 10 minutes to 10.0 g / 10 minutes. When the MFR of the AS copolymer is 2.0 g / 10 min to 15.0 g / min, the AS copolymer has excellent compatibility with the polypropylene-based resin, and the obtained resin particles are continuously foamed. Foaming can be reduced. As a result, it has an advantage that foamed particles having a low open cell ratio can be obtained.

In the present specification, the MFR value of the AS copolymer is a value obtained by measuring under the following conditions using the MFR measuring instrument described in JIS K7210: 1999: Orifice diameter 2.0959. ± 0.005 mmφ, orifice length 8,000 ± 0.025 mm, load 2.16 kgf, temperature 230 ° C (230 ± 0.2 ° C).

The content of the AS copolymer in the foamed particles is 5 parts by weight to 60 parts by weight, more preferably 5 parts by weight to 50 parts by weight, and 8 parts by weight to 50 parts by weight with respect to 100 parts by weight of the polypropylene-based resin. Parts by weight are more preferable, parts by weight 10 to 40 parts by weight are more preferable, parts by weight 13 to 40 parts by weight are more preferable, parts by weight 15 to 35 parts by weight are further preferable, and parts by weight 20 to 30 parts by weight are particularly preferable. When the content of the AS copolymer is (a) 5 parts by weight or more with respect to 100 parts by weight of the polypropylene resin, foamed particles having excellent foamability can be obtained, and after molding as compared with the conventional product. It has an advantage that a foamed molded product having further reduced shrinkage and deformation can be obtained, and (b) when it is 60 parts by weight or less, foamed particles having a low open cell ratio and excellent foamability can be obtained. It has the advantage of.

(Hydrogenated styrene copolymer)
The polypropylene-based resin foamed particles according to the embodiment of the present invention contain 3.0 parts by weight to 30.0 parts by weight of the hydrogenated styrene-based copolymer. In one embodiment of the present invention, the hydrogenated styrene-based copolymer has a compatibilizing effect between the polypropylene-based resin and the AS copolymer. In other words, the hydrogenated styrene-based copolymer can function as a compatibilizer. By containing the hydrogenated styrene-based copolymer within the above-mentioned range, the foamed particles can be foamed with excellent foamability, and the shrinkage and deformation after molding are further reduced as compared with the conventional product. It has the advantage that a molded product can be obtained.

In the present specification, the "hydrogenated styrene-based copolymer" is a block copolymer containing a styrene block composed of only styrene units and a conjugated diene-based block composed of only conjugated diene-based units (hereinafter, copolymer weight). It is a copolymer obtained by hydrogenating (also referred to as coalescence X). In the present specification, "hydrogenation" may be referred to as "hydrogenation". More specifically, the "hydrogenated styrene-based copolymer" refers to the copolymer X so that at least a part of the carbon-carbon double bond in the conjugated diene-based unit of the copolymer X is saturated. Intended is a copolymer obtained by hydrogenation.

The conjugated diene-based unit contained in the copolymer X includes a butadiene unit, an isoprene unit, a 1,3-pentadiene unit, a 2,3-dimethyl-1,3-butadiene unit, and a 3-methyl-1,3-octadien unit. , Or 4-ethyl-1,3-hexadiene unit, and the like, but are not particularly limited.

In the production of the hydrogenated styrene-based copolymer, at least a part of the carbon-carbon double bond in the conjugated diene-based unit of the copolymer X needs to be saturated, and all of them need to be saturated. There is no. In other words, the hydrogenated styrene-based copolymer may contain a conjugated diene-based unit contained in the copolymer X used for producing the hydrogenated styrene-based copolymer. More specifically, when the copolymer X contains a butadiene unit as a conjugated diene-based unit, (a) hydrogen is not added to the hydrogenated styrene-based copolymer obtained by hydrogenating the copolymer X. Butadiene units may be contained, and (b-1) hydrogen may contain butylene units obtained by addition-polymerizing 1,2 to carbon-carbon double bonds of butadiene units, and (b-2) hydrogen. May contain ethylene units obtained by 1,4 addition polymerization of butadiene units of carbon-carbon double bonds.

In the hydrogenated styrene-based copolymer, the ratio of the conjugated diene-based unit to which hydrogen is added to the carbon-carbon double bond (hereinafter, "hydrogen") out of the total amount of the conjugated diene-based unit of the copolymer X used for production. The addition rate) is preferably 50% or more, more preferably 70% to 100%, and even more preferably 80% to 100%. When the hydrogenation rate of the hydrogenated styrene-based copolymer is within the above range, the hydrogenated styrene-based copolymer is likely to be present at the interface between the polypropylene-based resin and the AS copolymer, and the hydrogenated styrene-based copolymer is likely to be present. The compatibilization effect of the copolymer tends to be improved. The hydrogenation rate of the hydrogenated styrene-based copolymer may be 100%.

Specific examples of the hydrogenated styrene-based copolymer include styrene / ethylene / butylene / styrene block copolymer (SEBS), styrene / ethylene / propylene / styrene block copolymer (SEPS), and the like. The SEBS is composed of (a) a styrene block composed of only styrene units, (b) a butadiene block composed of only butadiene units, and (c) a styrene block composed of only styrene units, in this order. It is a copolymer obtained by hydrogenating a copolymer (copolymer X). More specifically, SEBS includes (a) a styrene block composed of only styrene units, (b) (b-1) 1, and a butylene unit formed by addition-polymerized butadiene units and (b). -2) A block in which 1,4 addition-polymerized butadiene units are hydrogenated and an ethylene unit is randomly bonded, and (c) a copolymer in which the styrene block is bonded in this order. Is. In SEBS, the block in which the butylene unit and the ethylene unit are randomly bonded may contain a butadiene unit. SEPS consists of (a) a styrene block composed of only styrene units, (b) an isoprene block composed of only isoprene units, and (c) a styrene block composed of only styrene units, which are bonded in this order. It is a copolymer obtained by hydrogenating a copolymer (copolymer X). More specifically, SEPS includes (a) a styrene block composed of only styrene units, (b) a block in which ethylene units and propylene units are randomly bonded, which are hydrogenated with isoprene units, and (c). ) The styrene block is a copolymer formed by bonding in this order. Among these, the hydrogenated styrene-based copolymer preferably contains SEBS, and is particularly preferably SEBS, because it has the advantage of having relatively high strength.

The styrene unit content of the hydrogenated styrene-based copolymer (hereinafter, may be referred to as “styrene content”) is 5% by weight to 90% by weight in 100% by weight of the hydrogenated styrene-based copolymer. It is preferably 10% by weight to 85% by weight, more preferably 15% by weight to 80% by weight, and even more preferably 25% by weight to 55% by weight. According to this structure, there is an advantage that the compatibility between the polypropylene-based resin and the AS copolymer can be enhanced. In particular, when the styrene unit content of the hydrogenated styrene-based copolymer is 15% by weight or more in 100% by weight of the hydrogenated styrene-based copolymer, shrinkage and deformation after molding are more severe than those of the conventional product. There is a tendency to obtain reduced foam moldings.

The content of the hydrogenated styrene-based copolymer in the foamed particles is 3.0 parts by weight to 30.0 parts by weight with respect to 100 parts by weight of the polypropylene-based resin, and 4.0 parts by weight to 25.0 parts by weight. By weight is preferable, 5.0 parts by weight to 20.0 parts by weight is more preferable, 5.0 parts by weight to 15.0 parts by weight is further preferable, and 5.0 parts by weight to 10.0 parts by weight is particularly preferable. When the content of the hydrogenated styrene-based copolymer is 3.0 parts by weight or more with respect to 100 parts by weight of the polypropylene-based resin, the phase of the polypropylene-based resin and the AS copolymer by the hydrogenated styrene-based copolymer. It has the advantage that the solubilization effect is fully exhibited. When the content of the hydrogenated styrene-based copolymer is 30.0 parts by weight or less with respect to 100 parts by weight of the polypropylene-based resin, (a) foamed particles having excellent foamability can be obtained, and (b) foamed particles can be obtained. It has the advantages that the rigidity of the foamed molded product to be molded is sufficient, and (c) a foamed molded product having further reduced shrinkage and deformation after molding as compared with the conventional product can be obtained.

(Other resins, etc.)
The foamed particles include, as a resin component, a resin other than a polypropylene-based resin, an AS copolymer, and a hydrogenated styrene-based copolymer (other resins, etc.) as long as the effect according to the embodiment of the present invention is not impaired. It may be referred to.) Further may be included. Examples of the other resins include (a) high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid. Copolymers and ethylene resins such as ethylene / methacrylic acid copolymers, (b) polystyrene, styrene / maleic anhydride copolymers, and styrene resins such as styrene / ethylene copolymers, (c) polyphenylene. Polyphenylene ether-based resins such as ether and modified polyphenylene ether, polyolefin waxes such as (d) propylene / α-olefin wax, and (e) ethylene / propylene rubber, ethylene / butene rubber, ethylene / hexene rubber, ethylene / octene rubber, etc. Examples include olefin rubber. The styrene resin and the polyphenylene ether resin are amorphous resins.

The content of other resins and the like in the foamed particles is preferably more than 0 parts by weight and 50 parts by weight or less, and more preferably more than 0 parts by weight and 30 parts by weight or less with respect to 100 parts by weight of the polypropylene-based resin. Further, the foamed particles do not have to contain other resins or the like. That is, the content of other resins and the like in the foamed particles may be 0 parts by weight.

(Additive)
The foamed particles may further contain an additive in addition to the resin component including the polypropylene-based resin, the AS copolymer and the hydrogenated styrene-based copolymer. Examples of the additive include a colorant, a water-absorbent substance, a foaming nucleating agent, an antistatic agent, a flame retardant, an antioxidant, a light stabilizer, a crystal nucleating agent, a conductive agent, a lubricant and the like. In the production of the present foamed particles, such an additive may be used in the production of the resin particles and contained in the resin particles, or may be directly added to the dispersion liquid in the foaming step described later.

The water-absorbent substance is a substance used for the purpose of increasing the amount of impregnated water in the resin particles in the production of the foamed particles. By using a water-absorbent substance when producing the present foamed particles, foamability can be imparted to the resin particles. The effect of the water-absorbent substance on imparting foamability to the resin particles becomes particularly remarkable when water is used as the foaming agent.

Examples of the water-absorbent substance that can be used in one embodiment of the present invention include glycerin, diglycerin, polyethylene glycol, C12 to C18 fatty alcohols (eg, pentaerythritol, cetyl alcohol, stearyl alcohol), melamine, and isocyanul. Examples thereof include acid, melamine-isocyanuric acid condensate, zinc borate and the like. One kind of these water-absorbent substances may be used alone, or two or more kinds may be mixed and used. Further, when two or more kinds of water-absorbent substances are mixed and used, the mixing ratio may be appropriately adjusted according to the purpose.

Glycerin and polyethylene glycol (a) do not promote the miniaturization of the average bubble diameter of the foamed particles, and (b) have good compatibility with polypropylene-based resins. Therefore, among the above-mentioned water-absorbent substances, glycerin and / or polyethylene glycol are preferable.

The amount of the water-absorbent substance used in the production of the foamed particles, in other words, the content of the water-absorbent substance in the foamed particles will be described. The content of the water-absorbent substance in the foamed particles is 0.01 parts by weight to 1.00 parts by weight with respect to 100 parts by weight of the total amount of the polypropylene-based resin, the AS copolymer and the hydrogenated styrene-based copolymer. Is more preferable, and it is more preferably 0.05 part by weight to 0.70 part by weight, and further preferably 0.10 part by weight to 0.60 part by weight. When the content of the water-absorbent substance is (i) 0.01 parts by weight or more, the foaming effect of the water-absorbent substance can be sufficiently obtained, and (ii) 1.00 parts by weight or less. , There is no risk of the obtained foamed particles shrinking.

The foam nucleating agent is a substance that can be used in the production of the present foam particles and can become foam nuclei when the resin particles foam. In the production of the foamed particles, it is preferable to use a foaming nucleating agent, in other words, it is preferable that the foaming particles contain a foaming nucleating agent.

Examples of the effervescent nucleating agent that can be used in one embodiment of the present invention include silica (silicon dioxide), silicate, alumina, diatomaceous earth, calcium carbonate, magnesium carbonate, calcium phosphate, Nagaishi apatite, barium sulfate and the like. Examples of the silicate include talc, magnesium silicate, kaolin, halloysite, decite, aluminum silicate, zeolite and the like. In addition, one kind of these foam nucleating agents may be used alone, or two or more kinds may be mixed and used. Further, when two or more kinds of foam nucleating agents are mixed and used, the mixing ratio may be appropriately adjusted according to the purpose.

The amount of the foam nucleating agent used in the production of the foamed particles, in other words, the content of the foamed nucleating agent in the foamed particles will be described. From the viewpoint of uniformity of average cell diameter, the content of the foam nucleating agent in the foam particles was 0. 005 parts by weight to 2.000 parts by weight are preferable, 0.010 parts by weight to 1.000 parts by weight are more preferable, and 0.030 parts by weight to 0.500 parts by weight are further preferable.

The total amount of additives used in the production of the foamed particles, in other words, the total content of each additive in the foamed particles is more than 0 parts by weight and 10 parts by weight or less with respect to 100 parts by weight of the polypropylene resin. It is preferably more than 0 parts by weight and more preferably 5 parts by weight or less. Further, the foamed particles do not have to contain each additive. That is, the content of each additive in the foamed particles may be 0 parts by weight.

<Physical characteristics>
Hereinafter, the physical characteristics of the foamed particles will be described.

(Expansion magnification of foam particles)
The foamed particles preferably have a foaming ratio of 15.0 to 50.0 times, more preferably 15.0 to 40.0 times, and 15.0 to 25.0 times. It is more preferable, and it is particularly preferable that it is 15.0 times to 20.0 times. When the foaming ratio of the foamed particles is (i) 15.0 times or more, a lightweight foamed molded product can be obtained with high production efficiency, and when (ii) 50.0 times or less, the obtained foamed molded product can be obtained. There is no risk of insufficient strength. In the present specification, the “excellent foaming” foamed particles are intended to be foamed particles having a foaming ratio of 15.0 times or more of the foamed particles (one-stage foamed particles described later) formed by directly foaming the resin particles. ..

In the present specification, the expansion ratio of the expanded particles is calculated by the following methods (1) to (6): (1) The weight Gi of a certain amount of expanded particles is accurately measured to the unit of 0.001 g ((1). Round off the 4th digit after the decimal point); (2) Next, the entire amount of the foamed particles used for measuring the weight Gi is immersed in 100 mL of ethanol at 23 ° C. contained in a measuring cylinder; (3) Female. The volume y (cm ³ ) of the foamed particles is measured based on the increase in the liquid level position of the cylinder; (4) the weight Gi (g) of the foamed particles is divided by the volume yi (cm ³ ) of the foamed particles. The apparent density di (g / L) of the foamed particles is calculated by converting this into g / L units; (5) The resin particles used for producing the foamed particles are used instead of the foamed particles (1) to ( By performing the same operation as in 4), the density ds (g / L) of the resin particles is calculated; (6) The expansion ratio of the foamed particles is calculated by the following formula:
Foaming magnification Ki = ds / di.

(DSC ratio of foamed particles)
The foamed particles preferably have at least two melting peaks in the DSC curve obtained by the differential scanning calorimetry described below. Of the melting peaks, the amount of heat of melting obtained from the peak of melting on the high temperature side is referred to as "the amount of heat of melting on the high temperature side", and the amount of heat of melting obtained from the peak of melting on the low temperature side is referred to as "the amount of heat of melting on the low temperature side". When there are three or more melting peaks, the amount of heat of melting obtained from the hottest melting peak is the "heat of melting on the high temperature side", and the amount of heat of melting obtained from the other peaks of melting is "the amount of heat of melting on the low temperature side". And.

The DSC ratio of the foamed particles is not particularly limited, but is preferably 10.0% to 50.0%, more preferably 20.0% to 40.0%, and 22.0% to 30%. It is more preferably 9.0%. When the DSC ratio of the foamed particles is 10.0% or more, there is an advantage that the foamed molded product obtained by molding the foamed particles has sufficient strength. On the other hand, when the DSC ratio of the foamed particles is 40% or less, there is an advantage that the foamed particles can be molded at a relatively low molding temperature.

As used herein, the DSC ratio is intended to be the ratio of the heat of melting on the high temperature side to the total heat of melting calculated from the DSC curve of the foamed particles. In the present specification, the DSC curve is obtained by using a differential scanning calorimeter (for example, DSC6200 type manufactured by Seiko Instruments). More specifically, in the present specification, the methods for measuring (calculating) the DSC ratio of foamed particles using a differential scanning calorimeter (for example, DSC6200 type manufactured by Seiko Instruments) are as follows (1) to (5). : (1) Weigh 5 mg to 6 mg of foamed particles; (2) Raise the temperature of the foamed particles from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min to melt the foamed particles; (3) ) In the DSC curve of the foamed particles obtained in the process of (2) above, (a) the maximum point between the hottest melting peak and the melting peak next to the melting peak (on the low temperature side), and before the start of melting. The point representing the temperature is connected by a straight line, and (b) the maximum point and the point representing the temperature after the completion of melting are connected by a straight line; (4) (a) (a-1) the maximum point and the point after the completion of melting are connected. The heat quantity calculated from the region on the high temperature side surrounded by the line segment connecting the points representing the temperature of (a-2) and the DSC curve is defined as the heat quantity for melting on the high temperature side, and (b) (b-1) the maximum. The amount of heat calculated from the region on the low temperature side surrounded by the line segment connecting the point and the point representing the temperature before the start of melting, (b-2) DSC curve, is defined as the amount of heat for melting on the low temperature side, and (c) the high temperature side. The sum of the heat of melting and the heat of melting on the low temperature side is defined as the total heat of melting (= heat of melting on the high temperature side + heat of melting on the low temperature side); (5) The DSC ratio is calculated from the following equation:
DSC ratio (%) = (heat of melting on the high temperature side / total heat of melting) × 100.

The DSC ratio of the foamed particles is also a value that serves as a guide for the amount of crystals having a high melting point contained in the foamed particles. That is, the DSC ratio of the foamed particles is 10.0% to 50.0%, which indicates that the foamed particles contain a relatively large amount of crystals having a high melting point. Further, the DSC ratio of the foamed particles greatly contributes to the viscoelasticity of the resin particles and the foamed particles when the resin particles are foamed and when the foamed particles are expanded. That is, when the DSC ratio of the foamed particles is 10.0% to 50.0%, the resin particles and the foamed particles have excellent foamability when the resin particles are foamed and when the foamed particles are molded. And can exhibit swellability. As a result, the foamed particles have an advantage that it is possible to obtain a foamed molded product having excellent internal fusion property and mechanical strength such as compressive strength at a low molding pressure.

As a method of controlling the DSC ratio in the present foamed particles within a predetermined range, the conditions at the time of producing the present foamed particles (particularly, the foaming temperature, the foaming pressure, the holding time, and the temperature of the region (space) where the dispersion liquid is discharged) are used. Etc.) can be adjusted. From the viewpoint of easy adjustment, a method of adjusting the foaming temperature, foaming pressure and / or holding time is preferable as a method of controlling the DSC ratio within a predetermined range.

For example, when the foaming temperature is raised, the DSC ratio of the obtained foamed particles tends to be small, and conversely, when the foaming temperature is lowered, the DSC ratio of the obtained foamed particles tends to be large. This is because the amount of unmelted crystals contained in the foamed particles changes depending on the foaming temperature. Further, when the foaming pressure is increased, the DSC ratio of the obtained foamed particles tends to be small, and conversely, when the foaming pressure is lowered, the DSC ratio of the obtained foamed particles tends to be large. This is because the foaming pressure changes the degree of plasticization, which in turn changes the amount of unmelted crystals contained in the foamed particles. Further, the longer the holding time, the larger the DSC ratio of the obtained foamed particles tends to be. This is because the amount of unmelted crystals contained in the foamed particles changes depending on the holding time.

(Continuous bubble rate)
The lower the open cell ratio of the foamed particles, the more preferable. The open cell ratio of the foamed particles is preferably 15.0% or less, more preferably 10.0% or less, more preferably 9.0% or less, and 8.0% or less. It is more preferably 7.0% or less, more preferably 6.0% or less, more preferably 5.0% or less, and 4.0% or less. Is more preferable, and 3.0% or less is particularly preferable. The lower limit of the open cell ratio of the foamed particles is not particularly limited, and is, for example, 0.0% or more. According to this configuration, (a) the cells are hardly foamed and shrunk during molding of the foamed particles, so that the foamed particles have an advantage of being excellent in moldability, and (b) obtained by using the foamed particles. In the foamed molded product, it has an advantage that features such as shape arbitraryness, cushioning property, light weight, compressive strength and heat insulating property are more exhibited. The open cell ratio of the foamed particles can be controlled by, for example, the amount of the AS copolymer used.

In the present specification, the open cell ratio of the foamed particles is determined by using an air comparative hydrometer [manufactured by Tokyo Science Co., Ltd., Model 1000] according to the method described in Procedure C (PROSEDURE C) of ASTM D2856-87. It is a value obtained by measurement. Specifically, the open cell ratio of the foamed particles is calculated by sequentially carrying out the following (1) to (4): (1) Volume Vc (cm ³ ) of the foamed particles using an air comparative gravimeter. (2) Then, the total amount of the foamed particles after measuring Vc is submerged in the ethanol contained in the graduated cylinder; (3) Then, from the amount of increase in the position of ethanol in the graduated cylinder, the foamed particles The apparent volume Va (cm ³ ) is obtained; (4) The open bubble ratio of the foamed particles is calculated by the following formula: open bubble ratio (%) = ((Va-Vc) × 100) / Va. The method for measuring the volume Va as described above is also referred to as a submersion method.

<Manufacturing method of polypropylene-based resin foam particles>
The method for producing the foamed particles is not particularly limited, and a known production method can be appropriately used. The method for producing the foamed particles includes a foaming step of foaming polypropylene-based resin particles, and the polypropylene-based resin particles include 100 parts by weight of the polypropylene-based resin and 5 weights of a copolymer containing an acrylonitrile unit and a styrene-based unit. It is preferable that the method comprises 60 parts by weight and 3 parts by weight to 30 parts by weight of the hydrogenated styrene-based copolymer. Hereinafter, one aspect of the method for producing the foamed particles will be described in detail, but the above description (for example, the description in the <component> section) is appropriately incorporated except for the matters described in detail below. The method for producing the foamed particles is not limited to the following production method.

(Granulation process)
In producing the foamed particles, first, a step of producing polypropylene-based resin particles (granulation step) can be performed. In the present specification, "polypropylene resin particles" may be referred to as "resin particles". In the granulation step, 100 parts by weight of a polypropylene-based resin, 5 parts by weight to 60 parts by weight of a copolymer containing an acrylonitrile unit and a styrene-based unit, and 3 parts by weight to 30 parts by weight of a hydrogenated styrene-based copolymer are used. It can be said that this is a process of manufacturing resin particles containing the resin particles.

Examples of the method for producing resin particles include a method using an extruder. Specifically, for example, resin particles can be produced by the following methods (1) to (5): (1) polypropylene-based resin, AS copolymer and hydrogenated styrene-based copolymer, and If necessary, one or more selected from the group consisting of other resins and additives is blended to prepare a blend; (2) the blend is put into an extruder and the blend is melt-kneaded. The polypropylene-based resin composition is prepared; (3) the polypropylene-based resin composition is extruded from a die provided in the extruder; (4) the extruded polypropylene-based resin composition is cooled by passing it through water or the like. (5) Then, the solidified polypropylene-based resin composition is shredded into a desired shape such as a columnar shape, an elliptical shape, a spherical shape, a cubic shape, a rectangular shape, or the like with a cutter. Alternatively, in (3), the polypropylene-based resin composition melt-kneaded is extruded directly into water from a die provided in the extruder, and immediately after extrusion, the polypropylene-based resin composition is cut into particle shapes, cooled, and solidified. Is also good. By melt-kneading the blended product in this way, more uniform resin particles can be obtained.

The weight per grain of the resin particles obtained as described above is preferably 0.5 mg / grain to 3.0 mg / grain, and more preferably 0.7 mg / grain to 2.5 mg / grain. When the weight per grain of the resin particles is 0.5 mg / grain or more, the handleability of the resin particles tends to be improved, and when the weight is 3.0 mg / grain or less, the mold is filled in the in-mold foam molding step. There is a tendency for sex to improve.

The amount of polypropylene-based resin, AS copolymer and hydrogenated styrene-based copolymer, and other resins and additives to be subjected to the granulation step (blended and melt-kneaded) in the produced resin particles. , The content of each of the above components. Therefore, in the granulation step, at least 100 parts by weight of the polypropylene-based resin, 5 parts by weight to 60 parts by weight of the copolymer containing the acrylonitrile unit and the styrene-based unit, and 3 parts by weight to 30 parts by weight of the hydrogenated styrene-based copolymer are performed. It is preferable to include a step of blending the parts and the mixture and melt-kneading the blended product.

(Foaming process)
The mode of the foaming step in the method for producing the foamed particles is not particularly limited as long as the resin particles can be foamed. In one embodiment of the invention, the foaming step is
(A) A dispersion step of dispersing resin particles, an aqueous dispersion medium, a foaming agent, and if necessary, a dispersant and / or a dispersion aid in a container.
(B) A temperature rise-boosting step in which the temperature inside the container is raised to a constant temperature and the pressure inside the container is raised to a constant pressure.
(C) A holding step of holding the temperature and pressure inside the container at a constant temperature and pressure, and
(D) It is preferable to include a discharge step of releasing one end of the container and discharging the dispersion liquid in the container to a region (space) having a pressure lower than the foaming pressure (that is, the pressure inside the container).

The process of producing the foamed particles from the resin particles in this way is referred to as a "one-stage foaming step", and the obtained foamed particles are referred to as "one-stage foamed particles".

The amount of the polypropylene-based resin, AS copolymer, and hydrogenated styrene-based copolymer contained in the resin particles to be subjected to the foaming step is the polypropylene-based resin, AS copolymer, and hydrogenated styrene-based polymer in the obtained foamed particles. It is the amount of copolymer. Therefore, in the foaming step in the method for producing the foamed particles, 100 parts by weight of the polypropylene resin, 5 to 60 parts by weight of the copolymer containing the acrylonitrile unit and the styrene unit, and 3 weight of the hydrogenated styrene copolymer are used. It is preferable that the step is to foam the resin particles containing parts to 30 parts by weight.

(Dispersion process)
The dispersion step can be said to be, for example, a step of preparing a dispersion liquid in which resin particles, a foaming agent, and, if necessary, a dispersant and / or a dispersion aid are dispersed in an aqueous dispersion medium.

The container used in the dispersion step is not particularly limited, but a container that can withstand the foaming temperature and foaming pressure described later is preferable. As the container, for example, a pressure-resistant container is preferable, and an autoclave type pressure-resistant container is more preferable.

The aqueous dispersion medium is not particularly limited as long as it can uniformly disperse resin particles, a foaming agent, and the like. Examples of the aqueous dispersion medium include (a) a dispersion medium obtained by adding methanol, ethanol, ethylene glycol, glycerin and the like to water, and (b) water such as tap water and industrial water. From the viewpoint of stable production of foamed particles, the aqueous dispersion medium includes RO water (water purified by the reverse osmosis membrane method), distilled water, deionized water (water purified by an ion exchange resin), etc. It is preferable to use pure water, ultrapure water, or the like.

The amount of the aqueous dispersion medium used is not particularly limited, but is preferably 100 parts by weight to 400 parts by weight with respect to 100 parts by weight of the resin particles. When the amount of the aqueous dispersion medium used is (a) 100 parts by weight or more, there is no possibility that the stability of the dispersion liquid is deteriorated (in other words, the dispersion of the resin particles is good), and (b) 400 parts by weight or less. If this is the case, there is no risk that the productivity of the foamed particles will decrease.

Examples of the effervescent agent include (a) (a-1) an inorganic gas such as nitrogen, carbon dioxide and air (a mixture of oxygen, nitrogen and carbon dioxide), and (a-2) an inorganic effervescent agent such as water; (B) (b-1) Saturated hydrocarbons having 3 to 5 carbon atoms such as propane, normal butane, isobutane, normal pentane, isopentan, neopentane, and (b-2) ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether. , (B-3) Organic foaming agents such as monochloromethane, dichloromethane, halogenated hydrocarbons such as dichlorodifluoroethane; and the like. As the foaming agent, at least one selected from the group consisting of the above-mentioned inorganic foaming agent and organic foaming agent can be used. When two or more kinds of foaming agents are mixed and used, the mixing ratio may be appropriately adjusted according to the purpose. From the viewpoint of environmental load and foaming power, the inorganic foaming agent is preferable as the foaming agent among the above-mentioned foaming agents. In addition, carbon dioxide is preferable among the inorganic foaming agents because it has a moderately high plasticizing effect and easily improves the foamability of the foamed particles in the production of the foamed particles.

The amount of the foaming agent used is not particularly limited, and may be appropriately used according to (a) the type of foaming agent and / or (b) the desired expansion ratio of the foamed particles. The amount of the foaming agent used is, for example, preferably 1 part by weight to 10000 parts by weight, more preferably 1 part by weight to 5000 parts by weight, still more preferably 1 part by weight to 1000 parts by weight, based on 100 parts by weight of the resin particles. When the amount of the foaming agent used is 1 part by weight or more with respect to 100 parts by weight of the resin particles, foamed particles having a suitable density can be obtained. On the other hand, when the amount of the foaming agent used is 10,000 parts by weight or less with respect to 100 parts by weight of the resin particles, the effect according to the amount of the foaming agent used can be obtained, so that no economic waste occurs. The amount of the foaming agent used may be, for example, 1 part by weight to 100 parts by weight or 1 part by weight to 10 parts by weight with respect to 100 parts by weight of the resin particles.

When water is used as the foaming agent, the water in the dispersion liquid in the container can be used as the foaming agent. Specifically, when water in the dispersion liquid is used as the foaming agent, it is preferable that the resin particles contain a water-absorbent substance in advance. As a result, the resin particles can easily absorb the water of the dispersion liquid in the container, and as a result, the water can be easily used as a foaming agent.

It is preferable to use a dispersant in the method for producing the foamed particles. By using the dispersant, there is an advantage that the coalescence of the resin particles (sometimes referred to as blocking) can be reduced and the foamed particles can be stably produced. Examples of the dispersant include inorganic substances such as calcium tertiary phosphate, magnesium tertiary phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, clay, aluminum oxide, titanium oxide, and aluminum hydroxide. One type of these dispersants may be used alone, or two or more types may be mixed and used. Further, when two or more kinds of dispersants are mixed and used, the mixing ratio may be appropriately adjusted according to the purpose.

The amount of the dispersant used in the dispersion liquid used in one embodiment of the present invention is preferably 0.01 parts by weight to 3.00 parts by weight, preferably 0.05 parts by weight to 2 parts by weight with respect to 100 parts by weight of the resin particles. .00 parts by weight is more preferable, and 0.10 parts by weight to 1.00 parts by weight is further preferable. When the amount of the dispersant used is (a) 0.01 parts by weight or more, there is no risk of causing poor dispersion of the resin particles, and (b) when it is 3.00 parts by weight or less, the obtained foamed particles are used. During in-mold foam molding, there is no risk of causing poor fusion between the foamed particles.

In the method for producing the foamed particles, a dispersion aid is used in order to (a) improve the effect of reducing the coalescence of the resin particles and / or (b) improve the stability of the dispersion liquid in the container. It is preferable to do so. Examples of the dispersion aid include anionic surfactants. Examples of the anionic surfactant include sodium alkylbenzene sulfonate such as sodium dodecylbenzene sulfonate, sodium alkane sulfonate, sodium alkyl sulfonate, sodium alkyl diphenyl ether disulfonate, sodium α-olefin sulfonate and the like. One type of these dispersion aids may be used alone, or two or more types may be mixed and used. Further, when two or more kinds of dispersion aids are mixed and used, the mixing ratio may be appropriately adjusted according to the purpose.

The amount of the dispersion aid used in the dispersion liquid used in one embodiment of the present invention is preferably 0.001 part by weight to 0.500 part by weight, preferably 0.001 part by weight, based on 100 parts by weight of the resin particles. It is more preferably from parts by weight to 0.200 parts by weight, and even more preferably from 0.010 parts by weight to 0.200 parts by weight. When the amount of the dispersion aid used is within the above range, there is no risk of causing poor dispersion of the resin particles.

If the stability of the dispersion is reduced, multiple resin particles may coalesce or form a lump in the container. As a result, (i) coalesced foam particles can be obtained, (ii) a lump of resin particles remains in the container and the foam particles cannot be produced, or (iii) the productivity of the foam particles is lowered. It may happen.

(Temperature temperature-boosting process and holding process)
The temperature rise-pressurization step is preferably performed after the dispersion step, and the holding step is preferably performed after the temperature rise-pressurization step. In the present specification, (a) a constant temperature in the temperature raising-pressurizing step and the holding step may be referred to as a foaming temperature, and (b) a constant pressure may be referred to as a foaming pressure.

The foaming temperature varies depending on the types of polypropylene-based resin, AS copolymer and hydrogenated styrene-based copolymer, the type of foaming agent, the apparent density of desired foamed particles, etc., and cannot be unconditionally specified. The foaming temperature is (i) (a) a mixture of polypropylene-based resin, AS copolymer and hydrogenated styrene-based copolymer, (b) polypropylene-based resin composition, or (c) melting point of resin particles-20.0. The temperature is preferably from ° C to + 10.0 ° C, and is preferably (ii) (a) a mixture of a polypropylene-based resin, an AS copolymer and a hydrogenated styrene-based copolymer, (b) a polypropylene-based resin composition, or (c). ) The melting point of the resin particles is more preferably -15.0 ° C to + 8.0 ° C, and (iii) (a) a mixture of a polypropylene-based resin, an AS copolymer and a hydrogenated styrene-based copolymer, (b). ) The polypropylene-based resin composition or (c) the resin particles has a melting point of -10.0 ° C to a melting point of + 6.0 ° C, which is more preferable.

The foaming pressure is preferably 1.0 MPa (gauge pressure) to 10.0 MPa (gauge pressure), more preferably 2.0 MPa (gauge pressure) to 5.0 MPa (gauge pressure), and 2.5 MPa (gauge pressure) to 3. 5.5 MPa (gauge pressure) is more preferable. When the foaming pressure is 1.0 MPa (gauge pressure) or more, foamed particles having a suitable density can be obtained.

In the holding step, the time (holding time) for holding the dispersion liquid in the container near the foaming temperature and the foaming pressure is not particularly limited. The holding time is preferably 10 to 60 minutes, more preferably 12 to 55 minutes, and even more preferably 15 to 50 minutes. When the holding time is 10 minutes or more, a sufficient amount of unmelted crystals (polypropylene resin crystals) are present, and as a result, the shrinkage of the obtained foamed particles and / or the increase in the open cell ratio can be reduced. Has advantages. On the other hand, when the holding time is 60 minutes or less, there is no excessive amount of unmelted crystals, so that there is an advantage that the foamed particles can be molded at a low molding temperature.

(Release process)
It is preferable that the release step is carried out after (a) a temperature rise-pressurization step when the holding step is not carried out, and (b) after the holding step when the holding step is carried out. The release step allows the resin particles to be foamed, resulting in foamed particles.

In the release step, the "region below the foaming pressure" is intended as "the region under the pressure below the foaming pressure" or "the space under the pressure below the foaming pressure", and the "atmosphere at a pressure lower than the foaming pressure". It can also be said to be "below." The region having a lower pressure than the foaming pressure is not particularly limited as long as the pressure is lower than the foaming pressure, and may be, for example, a region under atmospheric pressure.

In the discharge step, when the dispersion liquid is discharged to a region lower than the foaming pressure, the dispersion liquid is passed through an open orifice having a diameter of 1 mm to 5 mm for the purpose of adjusting the flow rate of the dispersion liquid and reducing the variation in the expansion ratio of the obtained foamed particles. Can also be released. Further, for the purpose of improving foamability, the low pressure region (space) may be filled with saturated steam.

(Two-stage foaming process)
By the way, in order to obtain foamed particles having a high foaming ratio, there is a method of increasing the amount of the inorganic foaming agent used in the one-stage foaming step (hereinafter referred to as method 1). Further, as a method other than Method 1, foamed particles (one-stage foamed particles) having a relatively low magnification (foaming ratio of about 2.0 to 35.0 times) were obtained in the one-stage foaming step, and then 1 was obtained. A method of increasing the foaming ratio by re-foaming the step-foamed particles (hereinafter referred to as method 2) can also be adopted.

Examples of the method 2 include a method including the following (a1) to (a3) in order: (a1) One-stage foamed particles having a foaming ratio of 2.0 to 35.0 times in the one-stage foaming step. Manufacture; (a2) The one-stage foamed particles are placed in a pressure-resistant container and pressure-treated with nitrogen, air, carbon dioxide, etc. at 0.2 MPa (gauge pressure) to 0.6 MPa (gauge pressure) to perform one-stage. The pressure inside the foamed particles (hereinafter, may be referred to as "internal pressure") is made higher than the normal pressure; (a3) Then, a method of heating the one-stage foamed particles having an increased internal pressure with steam or the like to further foam them. The step of increasing the foaming ratio of the one-stage foamed particles as in Method 2 is called a "two-stage foaming step", and the polypropylene-based resin foamed particles obtained by the method of Method 2 are called "two-stage foamed particles".

In the above (a3) of the two-stage foaming step, the pressure of water vapor for heating the one-stage foamed particles is 0.03 MPa (gauge pressure) to 0.20 MPa (gauge pressure) in consideration of the expansion ratio of the two-stage foamed particles. It is preferable to adjust the gauge pressure). When the pressure of water vapor in the two-stage foaming step is 0.03 MPa (gauge pressure) or more, the foaming ratio tends to improve, and when it is 0.20 MPa (gauge pressure) or less, the obtained two-stage foamed particles are used. Is less likely to coalesce. When the two-stage foamed particles are coalesced together, the obtained two-stage foamed particles may not be available for subsequent in-mold foam molding.

The internal pressure of the one-stage foamed particles obtained by impregnating the one-stage foamed particles with nitrogen, air, carbon dioxide, etc. may be appropriately changed in consideration of the expansion ratio of the two-stage foamed particles and the water vapor pressure in the two-stage foaming step. desirable. The internal pressure of the one-stage foamed particles is preferably 0.15 MPa (absolute pressure) to 0.60 MPa (absolute pressure), more preferably 0.20 MPa (absolute pressure) to 0.60 MPa (absolute pressure), and 0.30 MPa (absolute pressure). Pressure) to 0.60 MPa (absolute pressure) is more preferable. When the internal pressure of the one-stage foamed particles is 0.15 MPa (absolute pressure) or more, high pressure water vapor is not required to improve the foaming ratio, so that the possibility of coalescence of the two-stage foamed particles is reduced. When the internal pressure of the one-stage foamed particles is 0.60 MPa (absolute pressure) or less, the possibility that the two-stage foamed particles are continuously foamed is reduced. As a result, the possibility that the rigidity such as the compressive strength of the finally obtained in-mold foam molded product is reduced is reduced. In addition, "tonghua" can also be said to be "tonghua of bubbles".

[2. Polypropylene resin foam molded product]
The polypropylene-based resin foam molded article according to the embodiment of the present invention is described in [1. Polypropylene-based resin foamed particles] is a foamed molded product obtained by molding the polypropylene-based resin foamed particles described in the section. The polypropylene-based resin foam molded article according to the embodiment of the present invention is described in [1. It can be said that the polypropylene-based resin foamed particles described in the section [Polypropylene-based resin foamed particles] are included. Further, the present foamed molded product is formed by molding polypropylene-based resin foam particles obtained by the method for producing the present foam particles (for example, the production method described in the above-mentioned <Production method for producing polypropylene-based resin foam particles>). Although it can be said to be a foam molded product, it can also be said to be a foam molded product containing polypropylene-based resin foam particles obtained by the method for producing the present foam particles. Further, the present foam molded product is described in the above [1. It can be said that it is a foamed molded product obtained by molding the present foamed particles described in the section of [Polypropylene resin foamed particles], and it can also be said that it is a foamed molded product containing the present foamed particles.

In the present specification, the "polypropylene resin foam molded product according to the embodiment of the present invention" may be referred to as the "present foam molded product".

Since the foam molded product has the above-mentioned structure, it has an advantage that there is almost no shrinkage or deformation after molding.

(Shrinkage factor)
In the present specification, "there is almost no shrinkage after molding" with respect to the foam molded product means that the shrinkage rate obtained by measuring by the following methods (1) to (3) is small: (1). Foamed particles are foam-molded in a mold using a mold having known dimensions (for example, 369 mm in the longitudinal direction × 319 mm in the lateral direction × 50 mm in the thickness direction). Here, the length in the longitudinal direction of the mold is L0; (2) the length L1 in the longitudinal direction of the obtained foamed molded product is measured. (3) Calculate the shrinkage rate (%) according to the following formula:
Shrinkage rate (%) = ((L1-L0) × 100) / L0.

The shrinkage of the foam molded product is preferably 1.2% or less, more preferably 1.0% or less, further preferably 0.8% or less, and 0.6% or less. It is particularly preferable to have. It can be said that the foam molded product having a shrinkage ratio of 1.2% or less has good dimensional stability because it is intended that the foamed molded product obtained by production is unlikely to have dimensional variation. The foamed particles that can provide a foamed molded product having good dimensional stability, and the foamed molded product have an advantage that they can be suitably used in the field of insert molding that is integrally molded with other materials such as metal.

(Deformation amount)
Hereinafter, the amount of deformation of the foam molded product will be described with reference to FIG. 1. FIG. 1 is a schematic view of a foam molded product 100 used for evaluating the amount of deformation. The foam molded body 100 is manufactured using a mold having a partition plate in the center of the mold (length direction 350 mm × lateral direction 320 mm × thickness direction (moving mold drive direction) 180 mm). In FIG. 1, the X direction can be said to be the thickness direction of the foam molded product 100, and can also be said to be the movable drive direction. The Y direction can be said to be the longitudinal direction of the foam molded product 100, and is a direction that intersects the X direction perpendicularly. The Z direction can be said to be the lateral direction of the foam molded product 100, and is a direction that intersects each of the X direction and the Y direction perpendicularly. As shown in FIG. 1, in the foam molded product 100, the dimensions (lengths) of the two ends in the longitudinal direction in the Z direction are K1 and K2, respectively, and the dimension in the Z direction of the central portion in the longitudinal direction is K3. And.

In the present specification, "almost no deformation" with respect to the foam molded body means that the amount of deformation obtained by measuring by the following methods (1) to (3) is small: (1) longitudinal direction (1) Foamed particles using a mold having dimensions (length) of 350 mm in the Y direction, 320 mm in the lateral direction (Z direction) and 180 mm in the thickness direction (X direction), and having a partition plate in the center of the mold. (2) Z-direction dimensions (mm) (K1, K2) of the two longitudinal ends of the obtained foam-formed body (foam-formed body 100) and the central portion in the longitudinal direction. Measure the dimensions (mm) (K3) in the Z direction; (3) Calculate the amount of deformation according to the following formula:
Deformation amount (mm) = {(K1 + K2) / 2} -K3.

The amount of deformation of the foam molded product is preferably 14.0 mm or less, more preferably 13.0 mm or less, more preferably 12.0 mm or less, and more preferably 11.0 mm or less. It is preferably 10.0 mm or less, more preferably 9.0 mm or less, more preferably 8.0 mm or less, more preferably 7.0 mm or less, and 6.0 mm or less. Is more preferable, and 5.0 mm or less is particularly preferable. It can be said that the foamed molded product having a deformation amount of 14.0 mm or less has good dimensional stability because it is intended that the foamed molded product obtained by manufacturing is less likely to have dimensional variation.

<Manufacturing method of foam molded product>
The method for producing the foam molded product is not particularly limited, and a known method can be applied. As a method for producing the present foam molded product, the above-mentioned [1. Includes a step of in-mold foam molding of the main foamed particles described in the item [Polypropylene resin foamed particles] or the foamed particles obtained by the production method described in the above item <Method for producing polypropylene-based resin foamed particles>. Is preferable. Specific embodiments of the method for producing the present foam molded product include, for example, a production method (in-mold foam molding method) including the following (b1) to (b6) in order, but the present invention is not limited to such a production method. :
(B1) A mold composed of a fixed mold that cannot be driven and a movable mold that can be driven is mounted on the in-mold foam molding machine. Here, the fixed type and the mobile type can be formed inside the fixed type and the mobile type by driving the mobile type toward the fixed type (the operation may be referred to as "mold closing");
(B2) Drive the mobile mold toward the fixed mold so that a slight gap (also referred to as cracking) is formed so that the fixed mold and the mobile mold are not completely closed.
(B3) Foamed particles are filled into the molding space formed inside the fixed mold and the mobile mold, for example, through a filling machine;
(B4) Drive the mobile type so that the fixed type and the mobile type are completely closed (that is, completely closed);
(B5) After preheating the mold with steam, the mold is heated on one side and the other side with steam, and then the mold is heated on both sides with steam to perform in-mold foam molding;
(B6) The foamed molded product in the mold is taken out from the mold and dried (for example, dried at 75 ° C.) to obtain a foamed molded product.

In the above (b3), as a method of filling the foamed particles in the molding space, the following methods (b3-1) to (b3-4) can be mentioned:
(B3-1) The foamed particles (including the above-mentioned two-stage foamed particles, the same applies hereinafter) are pressure-treated with an inorganic gas in a container, the foamed particles are impregnated with the inorganic gas, and a predetermined internal pressure of the foamed particles is applied. A method of filling the molding space with the foamed particles after the application;
(B3-2) A method of filling a molding space with foamed particles and then compressing the volume in the mold so as to reduce the volume by 10% to 75%;
(B3-3) A method of compressing foamed particles with gas pressure and filling the molding space;
(B3-4) A method of filling a molding space with foamed particles without any particular pretreatment.

Among the methods for producing the foamed molded product, at least one selected from the group consisting of air, nitrogen, oxygen, carbon dioxide, helium, neon, argon and the like can be used as the inorganic gas in the method (b3-1). .. Among these inorganic gases, air and / or carbon dioxide are preferable.

Among the methods for producing the present foamed molded product, the internal pressure of the foamed particles in the method (b3-1) is preferably 0.10 MPa (absolute pressure) to 0.30 MPa (absolute pressure), and 0.11 MPa (absolute pressure) to 0. 25 MPa (absolute pressure) is preferable.

Of the methods for producing the present foamed molded product, the temperature inside the container when the foamed particles are impregnated with the inorganic gas by the method (b3-1) is preferably 10 ° C. to 90 ° C., more preferably 40 ° C. to 90 ° C. ..

In the methods (b3-2) and (b3-3) described above, the resilience of the foamed particles compressed by gas pressure is used in order to fuse the foamed particles in the subsequent step (b5).

One embodiment of the present invention may have the following configuration.

[1] 100 parts by weight of a polypropylene-based resin, 5 to 60 parts by weight of a copolymer containing an acrylonitrile unit and a styrene-based unit, and 3.0 to 30.0 parts by weight of a hydrogenated styrene-based copolymer. , Including polypropylene-based resin foam particles.

[2] The polypropylene-based resin foamed particles according to [1], wherein the styrene-based unit is an α-methylstyrene unit.

[3] The polypropylene-based resin foamed particles according to [1] or [2], wherein the hydrogenated styrene-based copolymer is a styrene / ethylene / butylene / styrene copolymer (SEBS).

[4] The styrene unit content of the hydrogenated styrene-based copolymer is 15% by weight to 80% by weight in 100% by weight of the hydrogenated styrene-based copolymer, any of [1] to [3]. The polypropylene-based resin foamed particles according to one.

[5] The polypropylene-based resin foamed particles according to any one of [1] to [4], wherein the copolymer containing the acrylonitrile unit and the styrene-based unit has a glass transition temperature of 95 ° C. to 140 ° C.

[6] A polypropylene-based resin foam molded product obtained by molding the polypropylene-based resin foamed particles according to any one of [1] to [5].

[7] The polypropylene-based resin particles have a foaming step of foaming the polypropylene-based resin particles, and the polypropylene-based resin particles are composed of 100 parts by weight of the polypropylene-based resin and 5 to 60 parts by weight of a copolymer containing an acrylonitrile unit and a styrene-based unit. , A method for producing polypropylene-based resin foamed particles, which comprises 3.0 parts by weight to 30.0 parts by weight of a hydrogenated styrene-based copolymer.

[8] The method for producing polypropylene-based resin foamed particles according to [7], wherein the styrene-based unit is an α-methylstyrene unit.

[9] The method for producing polypropylene-based resin foam particles according to [7] or [8], wherein the hydrogenated styrene-based copolymer is a styrene / ethylene / butylene / styrene copolymer (SEBS).

[10] The styrene unit content of the hydrogenated styrene-based copolymer is any one of [7] to [9], which is 15% by weight to 80% by weight in 100% by weight of the hydrogenated styrene-based copolymer. The method for producing polypropylene-based resin foam particles according to one.

[11] The production of polypropylene-based resin foamed particles according to any one of [7] to [10], wherein the glass transition temperature of the copolymer containing the acrylonitrile unit and the styrene-based unit is 95 ° C. to 140 ° C. Method.

[12] Polypropylene resin foamed particles according to any one of [1] to [5], or polypropylene resin foam obtained by the method according to any one of [7] to [11]. A method for producing a polypropylene-based resin foam molded product, which comprises a step of molding particles.

Hereinafter, one embodiment of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to such Examples.

〔material〕
The materials used in Examples and Comparative Examples will be described below.

<Resin component>
(Polypropylene resin)
Polypropylene resin: 1-butene / ethylene / propylene random copolymer [melting point 149 ° C., 1-butene content 3.8% by weight, ethylene content 0.5% by weight, MFR = 10 g / 10 minutes]
(AS copolymer)
AS copolymer 1: acrylonitrile / α-methylstyrene copolymer [Tg121 ° C., α-methylstyrene content 70% by weight (styrene-based content 70% by weight), MFR = 4.9 g / 10 minutes]
AS copolymer 2: Acrylonitrile / styrene copolymer [Tg 108 ° C., styrene content 75% by weight (styrene content 75% by weight), MFR = 6.1 g / 10 minutes]
AS copolymer 3: Acrylonitrile / styrene copolymer [Tg 115 ° C., styrene content 50% by weight (styrene content 50% by weight), MFR = 8.1 g / 10 minutes]
(Hydrogenated styrene copolymer)
Hydrogenated Styrene Copolymer 1: SEBS (Styrene / Ethylene / Butylene / Styrene Copolymer, Dynaron9901P manufactured by JSR) [Styrene content 53%]
Hydrogenated Styrene Copolymer 2: SEBS (Styrene / Ethylene / Butylene / Styrene Copolymer, Dynaron8300P manufactured by JSR) [Styrene content 9%]
(Other resins)
(Amorphous resin)
Amorphous resin 1: Polystyrene [Tg101 ° C, MFR = 7.0]
Amorphous resin 2: Mixture of polyphenylene ether and polystyrene [Tg 120 ° C., MFR = 1.8 g / 10 minutes]
(Compatible agent)
Compatibility agent: Polypropylene / (Acrylonitrile / Styrene) Graft copolymer [Main chain: Polypropylene, Side chain: Acrylonitrile / Styrene copolymer, Polypropylene: Acrylonitrile / Styrene copolymer = 70 (mol%): 30 (mol%) )] (Polyper A3400 manufactured by Nichiyu Co., Ltd.)
<Additives>
(Water-absorbent substance)
Glycerin (manufactured by Lion Corporation, purified glycerin D)
(Foam nucleating agent)
Talc (manufactured by Hayashi Kasei Co., Ltd., Tarkhan powder (registered trademark) PK-S)
〔Measuring method〕
Measurements and evaluations of various items were carried out as follows.

(Melting point of polypropylene resin)
The melting point of the polypropylene-based resin was a value obtained by measuring by the DSC method using a differential scanning calorimeter (manufactured by Seiko Instruments Co., Ltd., DSC6200 type). The specific operation procedure was as follows (1) to (4): (1) The temperature of the polypropylene-based resin 5 mg to 6 mg was raised from 40.0 ° C to 220 at a heating rate of 10.0 ° C / min. The polypropylene-based resin was melted by raising the temperature to 0 ° C.; (2) Then, the temperature of the melted polypropylene-based resin was lowered from 220.0 ° C. to 40.0 at a temperature lowering rate of 10.0 ° C./min. The polypropylene-based resin was crystallized by lowering the temperature to ° C; (3), and then the temperature of the crystallized polypropylene-based resin was further increased from 40.0 ° C to 220 at a heating rate of 10.0 ° C / min. The temperature was raised to 0.0 ° C.; (4) The temperature of the peak (melting peak) of the DSC curve of the polypropylene-based resin obtained at the time of the second temperature rise (that is, at the time of (3)) was the melting point of the polypropylene-based resin. And said. When there are a plurality of peaks (melting peaks) in the DSC curve of the polypropylene resin obtained at the time of the second temperature rise by the above method, the temperature of the peak (melting peak) having the maximum heat of fusion is used. The melting point of the polypropylene resin was used.

(Glass transition temperature (Tg) of AS copolymer)
The glass transition temperature (Tg) of the AS polymer is the following (1) to (5) in accordance with JIS-K-7121 using a differential scanning calorimeter [DSC6200 type manufactured by Seiko Instruments Co., Ltd.]. ): (1) 5 mg of AS polymer was weighed; (2) the temperature of the AS polymer was raised from room temperature to 250 ° C. at 10 ° C./min under a nitrogen atmosphere. (3) The temperature of the heated AS polymer was lowered from 250 ° C. to room temperature at 10 ° C./min; (4) The temperature of the AS polymer was again lowered from room temperature to 250 ° C. at 10 ° C./min. (5) The temperature of the peak (melting peak) of the DSC curve of the AS polymer obtained at the time of the second temperature rise (that is, at the time of (4)) was defined as Tg of the AS polymer. ..

(MFR of polypropylene resin and AS copolymer)
The MFR of the polypropylene resin or AS copolymer was measured under the following conditions using the MFR measuring instrument described in JIS K7210: 1999: the diameter of the orifice was 2.0959 ± 0. 005 mmφ, orifice length 8,000 ± 0.025 mm, load 2.16 kgf, and temperature 230 ° C (230 ± 0.2 ° C).

(Expansion magnification of expanded particles (1-stage expanded particles, 2-stage expanded particles))
The method for measuring the expansion ratio of the expanded particles was as follows (1) to (6): (1) The weight Gi of a certain amount of expanded particles (one-stage expanded particles or two-stage expanded particles) was 0.001 g. (Rounded to the 4th digit after the decimal point); (2) Next, the entire amount of the foamed particles used for measuring the weight Gi was immersed in 100 mL of water at 23 ° C contained in a measuring cylinder. (3) The volume y (cm ³ ) of the foamed particles was measured based on the increase in the liquid level position of the measuring cylinder; (4) the weight Gi (g) of the foamed particles was measured as the volume y (g) of the foamed particles. The apparent density di (g / L) of the foamed particles was calculated by dividing by cm ³ ) and converting this into g / L units; (5) Instead of the foamed particles, the resin particles used for producing the foamed particles were used. The density ds (g / L) of the resin particles was calculated by performing the same operations as in (1) to (4); (6) The expansion ratio of the foamed particles was calculated by the following formula:
Foaming magnification Ki = ds / di.

(Effervescent)
The foamability of the foamed particles was evaluated by the foaming ratio of the one-stage foamed particles obtained by performing the one-stage foaming step under the same conditions. The evaluation criteria are as follows.
〇 (Good): The expansion ratio of the one-stage expanded particles is 15.0 times or more.
X (defective): The expansion ratio of the one-stage expanded particles is less than 15.0 times.

Here, the expansion ratio of the expanded particles is affected by the DSC ratio of the expanded particles. For example, when the foamed particles are produced by adjusting the foaming temperature or the like so that the DSC ratio of the foamed particles is low, the foamed particles having a high foaming ratio tend to be obtained. Therefore, when comparing the foaming ratios of different foamed particles, it is necessary to compare the foaming ratios in consideration of the influence of the DSC ratio of the foamed particles. That is, when comparing the expansion ratios between different foamed particles, the expansion ratios of the expanded particles can be compared relatively accurately by producing the expanded particles so that the DSC ratios are close to each other.

(DSC ratio of foamed particles)
In the measurement (calculation) of the DSC ratio of the foamed particles, a differential scanning calorimeter (DSC6200 type manufactured by Seiko Instruments) was used. The method for measuring (calculating) the DSC ratio of foamed particles using a differential scanning calorimeter was as follows (1) to (5): (1) 5 mg to 6 mg of foamed particles were weighed; (2). The temperature of the foamed particles was raised from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min to melt the foamed particles; (3) DSC curve of the foamed particles obtained in the step (2) above. In (a), the maximum point between the hottest melting peak and the melting peak next to the melting peak (on the low temperature side) and the point representing the temperature before the start of melting are connected by a straight line, and (b) the above. A straight line connects the maximum point and the point representing the temperature after melting; (4) (a) (a-1) The line segment connecting the maximum point and the point representing the temperature after melting and (a). -2) The heat quantity calculated from the region on the high temperature side surrounded by the DSC curve is defined as the heat quantity for melting on the high temperature side, and (b) (b-1) a line connecting the maximum point and the point representing the temperature before the start of melting. The amount of heat calculated from the region on the low temperature side surrounded by the minute and (b-2) DSC curve is taken as the amount of heat for melting on the low temperature side, and the sum of (c) the amount of heat for melting on the high temperature side and the amount of heat for melting on the low temperature side is total melting. The calorific value (= heat of melting on the high temperature side + heat of melting on the low temperature side) was used; (5) The DSC ratio was calculated from the following formula:
DSC ratio (%) = (heat of melting on the high temperature side / total heat of melting) × 100.

(Continuous cell ratio of foamed particles)
The open cell ratio of the polypropylene-based resin foamed particles was measured using an air comparative hydrometer [manufactured by Tokyo Science Co., Ltd., Model 1000] according to the method described in Procedure C (PROSEDURE C) of ASTM D2856-87. I asked for it. More specifically, the open cell ratio of the foamed particles was calculated by sequentially carrying out the following (1) to (4): (1) Volume Vc (cm ³ ) of the foamed particles using an air comparative gravimeter. (2) Then, the total amount of the foamed particles after measuring Vc was submerged in the ethanol contained in the graduated cylinder; (3) Then, from the amount of increase in the position of ethanol in the graduated cylinder, the foamed particles The apparent volume Va (cm ³ ) was determined; (4) The open cell ratio of the foamed particles was calculated by the following formula:
Open cell ratio (%) = ((Va-Vc) × 100) / Va.

(Shrinkage rate of foam molded product)
The method for measuring the shrinkage rate of the foam molded product was as follows (1) to (3): (1) A mold having known dimensions (for example, 369 mm in the longitudinal direction × 319 mm in the lateral direction × 50 mm in the thickness direction). ) Was used to foam-mold the foamed particles in the mold. Here, the length in the longitudinal direction of the mold was set to L0; (2) the length L1 in the longitudinal direction of the obtained foamed molded product was measured; (3) the shrinkage rate (%) was calculated according to the following formula:
Shrinkage rate (%) = ((L1-L0) × 100) / L0
The mold used for measuring the shrinkage rate may be referred to as a shrinkage rate evaluation mold.

(Deformation amount of foam molded product)
The method for measuring the amount of deformation of the foam molded body was as follows (1) to (3): (1) Longitudinal direction (Y direction) 350 mm, lateral direction (Z direction) 320 mm and thickness direction (X). Foam particles were foam-molded in the mold using a mold having a dimension (length) of 180 mm (direction) and having a partition plate in the center of the mold; (2) The obtained foam-molded body (foam molding). The Z-direction dimensions (mm) (K1, K2) of the two longitudinal ends of the body 100) and the Z-direction dimensions (mm) (K3) of the longitudinal central portion were measured; (3) the following equation. The amount of deformation was calculated according to:
Deformation amount (mm) = {(K1 + K2) / 2} -K3.
The mold used for measuring the deformation amount may be referred to as a deformation amount evaluation mold.

[Example 1]
(Preparation of polypropylene resin particles)
100 parts by weight (10 kg) of polypropylene resin, 12 parts by weight (1.2 kg) of AS copolymer 1, 7.0 parts by weight (700 g) of hydrogenated styrene polymer 1, as a foam nucleating agent. 0.050 parts by weight (5 g) of talc and 0.2 parts by weight (20 g) of glycerin as a water-absorbent substance were dry-blended.

The obtained blend was put into a twin-screw extruder [TEM26-SX manufactured by Toshiba Machine Co., Ltd.] and melt-kneaded at a resin temperature of 250 ° C. The melt-kneaded polypropylene-based resin composition was extruded into a strand shape through a die having a circular hole attached to the tip of the extruder. The extruded polypropylene-based resin composition was cooled with water and then cut with a cutter to obtain columnar resin particles (1.2 mg / grain).

(Preparation of polypropylene-based resin foamed particles (one-stage foamed particles))
100 parts by weight of the obtained resin particles, 200 parts by weight of pure water, 0.2 parts by weight of kaolin (ASP-170 manufactured by Engelhard) as a poorly water-soluble inorganic compound, and 0 sodium dodecylbenzenesulfonate as a surfactant. .03 parts by weight was put into a pressure-resistant airtight container. Then, 6.7 parts by weight of carbon dioxide was introduced into the pressure-resistant airtight container as a foaming agent while stirring the raw materials in the pressure-resistant airtight container to prepare a dispersion liquid. Next, the temperature inside the pressure-resistant airtight container was heated to a foaming temperature of 151.0 ° C. After that, carbon dioxide was additionally press-fitted into the pressure-resistant airtight container, and the pressure inside the pressure-resistant airtight container was increased to a foaming pressure of 3.2 MPa (gauge pressure) (heating-pressurizing step). Next, after holding the inside of the pressure-resistant airtight container at the foaming temperature and foaming pressure for 30 minutes (holding step), the valve at the bottom of the airtight container is opened, and the dispersion liquid is foamed under atmospheric pressure through an orifice having a diameter of 3.6 mm. Foamed particles (one-stage foamed particles) were obtained by discharging into a cylinder. At this time, carbon dioxide is additionally press-fitted into the pressure-resistant airtight container so that the pressure in the pressure-resistant airtight container does not drop from the foaming pressure during the discharge of the dispersion liquid, and the pressure in the pressure-resistant airtight container is 3.2 MPa (gauge pressure). ). Table 1 shows the results of measuring the foaming ratio, foamability, DSC ratio and open cell ratio of the obtained foamed particles.

(Preparation of polypropylene-based resin foamed particles (two-stage foamed particles))
The obtained one-stage foamed particles were dried at 60 ° C. for 6 hours and then placed in a pressure-resistant airtight container. Air is introduced into the pressure-resistant airtight container, and the one-stage foamed particles in the pressure-resistant airtight container are impregnated with pressurized air to apply an internal pressure (absolute pressure) of 0.24 MP (absolute pressure) to the one-stage foamed particles. did. Approximately 20 L of one-stage foamed particles impregnated with air (applied internal pressure to the foamed particles) were charged into the foaming machine. Then, the one-stage foamed particles in the foaming machine are heated with steam of 0.06 MPa (gauge pressure) for 30 seconds to further foam the one-stage foamed particles (two-stage foaming), and the foamed particles (two-stage foamed particles). ) Was obtained.

(Manufacturing of polypropylene-based resin foam molded product)
The obtained foamed particles (two-stage foamed particles) were put into a pressure-resistant airtight container. Air is introduced into the pressure-resistant airtight container, and the two-stage foamed particles in the pressure-resistant airtight container are impregnated with pressurized air to apply 0.20 MP (absolute pressure) internal pressure of the foamed particles (absolute pressure) to the two-stage foamed particles. did. The two-stage foamed particles impregnated with air were subjected to 0.30 MPa (0.30 MPa) using a molding machine (polypropylene mold in-mold foam molding machine manufactured by Daisen Co., Ltd.) and a shrinkage rate evaluation mold and a deformation amount evaluation mold. A foam-molded article was obtained by heat-molding with steam of (gauge pressure). After each of the obtained foam molded products was left at room temperature for 1 hour, it was cured and dried in a constant temperature room at 75 ° C. for 12 hours, and then left again at room temperature for 4 hours. Then, the shrinkage rate and the amount of deformation of the obtained foam molded product were evaluated by the above-mentioned method. The results are shown in Table 1.

(Examples 2 to 7, Comparative Examples 1 to 9)
Foamed particles and foamed compacts were obtained by the same method as in Example 1 except that the type of each material, the amount of each material, and / or each production condition were changed as shown in Table 1. The physical characteristics of the obtained foamed particles and foamed molded product were measured and evaluated. The results are shown in Table 1.

There is no significant difference in the DSC ratio of the foamed particles throughout the examples and comparative examples. Therefore, it is possible to compare the expansion ratios of the expanded particles relatively accurately through Examples and Comparative Examples.

〔summary〕
The following can be clearly seen from Table 1:
(1) From the comparison between Examples 1 to 7 and Comparative Example 1, when the polypropylene-based resin alone is used, the amount of deformation of the foamed molded product is large, and the reduction of shrinkage of the foamed molded product is insufficient. I understand.

(2) From the comparison between Examples 1 to 7 and Comparative Example 2, it can be seen that when polystyrene, which is an amorphous resin, is used instead of the AS copolymer, the foamability of the foamed particles is low.

(3) From the comparison between Examples 1 to 7 and Comparative Example 3, when a mixture of polyphenylene ether and polystyrene is used as the amorphous resin instead of the AS copolymer, the foaming particles have low foamability and can be obtained. It can be seen that the reduction of shrinkage of the foam molded product is also insufficient.

(4) From the comparison between Examples 1 to 7 and Comparative Example 4, when the amount of the AS copolymer used is larger than the range of the present application, the foamability of the foamed particles and the open cell ratio become poor (lower). I understand.

(5) From the comparison between Examples 1 to 7 and Comparative Example 5, it can be seen that when the hydrogenated styrene-based copolymer is not used, the reduction in shrinkage of the obtained foamed molded product is insufficient.

(6) From the comparison between Examples 1 to 7 and Comparative Example 6, when the amount of the hydrogenated styrene-based copolymer used is larger than the range of the present application, the foamability of the foamed particles is low, and the shrinkage of the obtained foamed molded product is reduced. It can be seen that the reduction of is also insufficient.

(7) From the comparison between Examples 1 to 7 and Comparative Example 7, when a non-hydrogenated styrene-based copolymer is used instead of the hydrogenated styrene-based copolymer, the shrinkage of the obtained foamed molded product is reduced. Turns out to be inadequate.

(8) From the comparison between Examples 1 to 7 and Comparative Example 8, it can be seen that when the amount of the AS copolymer used is less than the range of the present application, the reduction in shrinkage of the obtained foamed molded product is insufficient.

(9) From the comparison between Examples 1 to 7 and Comparative Example 9, when the amount of the hydrogenated styrene-based copolymer used is less than the range of the present application, the reduction in shrinkage of the obtained foamed molded product is insufficient. I understand.

The polypropylene-based resin foamed particles according to the embodiment of the present invention can provide a polypropylene-based resin foamed molded product having excellent foamability and hardly shrinking or deforming after molding. The polypropylene-based resin foam molded product can be suitably used for various applications such as cushioning packaging materials, physical distribution materials, heat insulating materials, civil engineering and building materials, and automobile materials.

Claims

With 100 parts by weight of polypropylene resin,
5 to 60 parts by weight of the copolymer containing acrylonitrile unit and styrene-based unit,
Polypropylene-based resin foamed particles containing 3.0 parts by weight to 30.0 parts by weight of a hydrogenated styrene-based copolymer.
The polypropylene-based resin foamed particles according to claim 1, wherein the styrene-based unit is an α-methylstyrene unit.
The polypropylene-based resin foamed particles according to claim 1 or 2, wherein the hydrogenated styrene-based copolymer is a styrene / ethylene / butylene / styrene copolymer (SEBS).
The styrene unit content of the hydrogenated styrene-based copolymer is 15% by weight to 80% by weight in 100% by weight of the hydrogenated styrene-based copolymer according to any one of claims 1 to 3. Polypropylene resin foam particles.
The polypropylene-based resin foamed particles according to any one of claims 1 to 4, wherein the copolymer containing the acrylonitrile unit and the styrene-based unit has a glass transition temperature of 95 ° C to 140 ° C.
A polypropylene-based resin foam molded product obtained by molding the polypropylene-based resin foamed particles according to any one of claims 1 to 5.
Has a foaming process to foam polypropylene resin particles,
The polypropylene-based resin particles are
With 100 parts by weight of polypropylene resin,
5 to 60 parts by weight of the copolymer containing acrylonitrile unit and styrene-based unit,
A method for producing polypropylene-based resin foamed particles, which comprises 3 parts by weight to 30 parts by weight of a hydrogenated styrene-based copolymer.
The method for producing polypropylene-based resin foamed particles according to claim 7, wherein the styrene-based unit is an α-methylstyrene unit.
The method for producing polypropylene-based resin foam particles according to claim 7 or 8, wherein the hydrogenated styrene-based copolymer is a styrene / ethylene / butylene / styrene copolymer (SEBS).
The styrene unit content of the hydrogenated styrene-based copolymer is 15% by weight to 80% by weight in 100% by weight of the hydrogenated styrene-based copolymer according to any one of claims 7 to 9. A method for producing polypropylene-based resin foam particles.
The method for producing polypropylene-based resin foamed particles according to any one of claims 7 to 10, wherein the glass transition temperature of the copolymer containing the acrylonitrile unit and the styrene-based unit is 95 ° C to 140 ° C.
Polypropylene resin foam obtained by the method for producing polypropylene resin foam particles according to any one of claims 1 to 5 or polypropylene resin foam particles according to any one of claims 7 to 11. A method for producing a polypropylene-based resin foam-molded body, which comprises a step of foam-molding particles in a mold.