JP2002097295A - Foamable olefin resin particle, foamed particle and foamed molding, and method of manufacturing these - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamable olefin resin particle capable of keeping foamability for a long time, to provide a foamed molding of olefin resin having excellent flexibility and appearance, and to provide methods of manufacturing these. SOLUTION: This foamable olefin resin particle is obtained by infiltrating a foaming agent into particles of an olefin resin composition particulated through melt-mixing an olefin resin and ethylene-styrene random copolymer, characterized in that the difference between the peak temperature on the high temperature side and the crystallization temperature is 60 deg.C or smaller, and the difference between the crystallization temperature and the inherent peak temperature shown as an endothermic peak is 40 deg.C or smaller in the measurement of DSC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expandable olefin-based resin particles, expanded olefin-based resin particles and foamed olefin-based resin molded articles obtained from the resin particles, and a method for producing these. For more information,
Expandable olefin-based resin particles capable of maintaining foamability for a long period of time, olefin-based resin expanded particles obtained by pre-expanding the expandable olefin-based resin particles, and light-weight formed by molding the olefin-based resin expanded particles in a mold. , Flexibility,
The present invention relates to an olefin resin foam molded article having excellent appearance and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Styrene-based resins, ethylene-based resins or propylene-based resins are widely used as base resins for foamed molded articles by in-mold molding. However, when a styrene-based resin is used as the base resin, there is a problem that the obtained foamed molded article is brittle and has poor chemical resistance. For this reason, there has been a problem in using the styrene-based resin foam as a cushioning material for packaging heavy objects or precision equipment requiring flexibility.

In order to solve these problems, a foam molded article using an ethylene resin as a base resin has been proposed. When such a resin is used as a base resin,
Although a flexible and tough foam molded article can be obtained, a cross-linking step is essential for lowering the density, and as a result, there is a drawback that the recyclability is poor. In addition, since this molded article has poor heat resistance, there is a problem in using it for a member that becomes hot.
Applications were limited. On the other hand, when a propylene-based resin is used as the base resin, the resin is substantially non-crosslinked and can be reduced in density (Japanese Patent Publication No. 56-1344), but the propylene-based resin has a high softening temperature. There are drawbacks in that the processing temperature during foaming / molding becomes high, the equipment costs of the foaming machine and the molding machine become expensive, and the durability of the mold is remarkably reduced. Further, the obtained molded article had improved heat resistance, but had high rigidity and poor flexibility.

[0004] In order to impart softness to the propylene resin, it has been studied to melt and mix an ethylene resin, an elastomer or the like. However, when such an ethylene-based resin or elastomer is added to the polypropylene-based resin, the crystallization temperature of the resin composition decreases, not only the molding cycle becomes longer, but also the rigidity inherent to the polypropylene-based resin decreases. Invite. On the other hand, it is also known that by adding an organic carboxylate such as sodium benzoate or basic ammonium dibenzoate, the crystallization temperature is increased, the molding cycle is shortened, and the rigidity of the molded product is increased. However, there are problems in control of gas retention and flexibility.

[0005] In addition, a method of increasing the crystallization temperature by adding an inorganic substance is also known, but the obtained foam is liable to break the cells and the like, and it is difficult to obtain a good molded product. Crosslinking of polypropylene with an easily crosslinkable polymer such as polyethylene or polybutadiene (JP-B-60-28856).
Publication), cross-linking of polypropylene (JP-B-60-168)
No. 632 and Japanese Patent Publication No. 3-48936) have a problem that, especially when the ethylene component is increased, a crosslinking step is indispensable for lowering the density of the foam, resulting in poor recyclability.

On the other hand, since the above-mentioned ethylene resins and propylene resins have low gas barrier properties, even when impregnated with a foaming agent, the foaming agent is dissipated in a short time, so that the period for which the foaming property can be maintained is very short. Has the property of being short. As a method for dealing with this, a release foaming method of releasing resin particles containing a foaming agent under a low pressure atmosphere (Japanese Patent Publication No. 59-2)
No. 3731) is generally known. However, this method can produce low-density expanded particles, but at a temperature equal to or higher than the Vicat softening temperature of the resin particles,
In order to impregnate the resin particles with a foaming agent, impregnation equipment capable of withstanding high pressure is required, and there is a problem that the equipment cost is high. In addition, the resin particles tended to coalesce, the solid / liquid ratio could not be increased, and the amount of foamed particles obtained in one batch production was not satisfactory. Furthermore, in the case of foamed particles having a relatively high bulk density of 0.1 g / cm ³ or more obtained by this method, the variation in the density between the particles becomes large, and it is difficult to produce a foamed molded article having a good appearance. There was also.

Further, unlike the case of expandable styrene resin particles, the expandable olefin resin particles cannot be transported in the form of expandable resin particles due to the rapid dissipation of the blowing agent, and therefore have a low bulk. It is transported in the form of high expanded particles, and there is a problem that the transportation cost increases.

Japanese Patent Publication No. 46-27597 proposes a method of forming a foam by adding a decomposable foaming agent to an olefin resin, but it is difficult to reduce the density by high foaming. Also, the decomposition type foaming agent is expensive,
In addition, the decomposition product residue remains in the foam, and it is difficult to recover and reuse the foaming agent. Therefore, the problem has not been completely solved.

Further, various methods for suppressing the dissipation of the blowing agent by mixing another resin with the olefin resin have been studied. For example, Japanese Patent Application Laid-Open No. 9-132664 proposes a composition in which an olefin resin and an ionomer resin are melt-mixed, but a sufficient effect has not been obtained. As described above, foamable resin particles having excellent gas retaining properties and foamed molded articles having both flexibility and heat resistance have been long-sought, but none have been satisfactory.

[0010]

In view of the above situation,
The present inventors have made intensive studies and as a result, an olefin resin,
Among the expandable olefin resin particles containing a foaming agent in an olefin resin composition particle obtained by melt-mixing an ethylene-styrene random copolymer and a foamable olefin resin particle having a specific range, the foamability is extended over a long period of time. We found that we could hold. Furthermore, the foamed molded article obtained from the expandable resin particles was found to be low in density and excellent in flexibility, and was found to be non-crosslinked and excellent in moldability and recyclability, and completed the present invention.

Thus, according to the present invention, a foamable olefin resin obtained by impregnating a foaming agent into olefin resin composition particles obtained by melting and mixing an olefin resin and an ethylene-styrene random copolymer into granules. Particles,
When the expandable resin particles were heated from 20 ° C. to 220 ° C. at a heating rate of 10 ° C./min, the DSC curve obtained by measuring with a scanning differential calorimeter had two endothermic peaks, The peak temperature on the high temperature side of the two endothermic peaks and the temperature of the expandable resin particles were reduced by 10 ° C./min.
When the temperature is reduced from 0 ° C. to 40 ° C., the difference from the crystallization temperature shown as an exothermic peak in a DSC curve obtained by measuring with a scanning differential calorimeter is 60 ° C. or less,
And the crystallization temperature and the foamable resin particles are set at 10 ° C. /
DSC obtained by measuring with a scanning differential calorimeter when the temperature was raised again from 40 ° C. to 220 ° C. at a heating rate of
There is provided expandable olefin-based resin particles characterized in that the difference from the intrinsic peak temperature indicated as an endothermic peak in the curve is 40 ° C. or less.

According to the present invention, there is also provided an expanded olefin resin particle obtained by pre-expanding the expandable olefin resin particles, wherein the expanded resin olefin resin particles are heated at a rate of 10 ° C./min from 20 ° C. When the temperature was raised to 220 ° C., the DSC curve obtained by the scanning differential calorimeter had two endothermic peaks, and the temperature of the peak on the high temperature side of the two endothermic peaks and the resin expanded particles were measured. When the temperature was lowered from 220 ° C. to 40 ° C. at a temperature lowering rate of 10 ° C./min, the difference from the crystallization temperature shown as an exothermic peak in a DSC curve obtained by a scanning differential calorimeter was 60%.
° C or lower, and the crystallization temperature is obtained by measuring with a scanning differential calorimeter when the resin expanded particles are heated again from 40 ° C to 220 ° C at a heating rate of 10 ° C / min. The present invention provides expanded olefin-based resin particles characterized in that a difference from an intrinsic peak temperature indicated as an endothermic peak in a DSC curve is 40 ° C or less.

According to the present invention, there is also provided an olefin resin foam molded article obtained by molding the above-mentioned olefin resin foam particles in a mold, wherein the resin foam molded article is heated at a rate of 10 ° C./min to 20 ° C. When the temperature was raised to about 220 ° C., the DSC curve obtained by the scanning differential calorimeter had two endothermic peaks, the peak temperature on the high temperature side of the two endothermic peaks, and the resin foam molded article When the temperature was lowered from 220 ° C. to 40 ° C. at a rate of 10 ° C./min, the difference from the crystallization temperature shown as an exothermic peak in a DSC curve obtained by a scanning differential calorimeter was 60 ° C. or less. And a DSC curve obtained by measuring with a scanning differential calorimeter when the crystallization temperature and the temperature of the resin foam molded article are raised again from 40 ° C. to 220 ° C. at a rate of 10 ° C./min. To Olefin resin foamed molded difference between intrinsic peak temperature shown as the endothermic peak There are characterized in that at 40 ° C. or less is provided.

According to the present invention, the olefin-based resin composition particles are melt-mixed with an olefin-based resin and an ethylene-styrene random copolymer to give granules of the olefin-based resin composition. A method for producing expandable olefin-based resin particles, characterized by impregnating a foaming agent in a temperature range up to 10 ° C. higher.

Further, according to the present invention, there is provided a method for producing expanded olefin resin particles, wherein the expandable olefin resin particles obtained by the above method are pre-expanded.

Further, according to the present invention, pre-expansion is performed once or plural times while applying pressure in a gas atmosphere containing a blowing agent using the expanded olefin resin particles obtained by the above method. A method for producing expanded olefin resin particles is provided. Further, according to the present invention, there is provided a method for producing an olefin-based resin foam molded article, which comprises in-mold molding the olefin-based resin foamed particles obtained by the above method.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The olefin resin used in the present invention is not particularly limited as long as it is a commonly used olefin resin, and examples thereof include homopolypropylene, ethylene random polypropylene, ethylene block polypropylene, and α-olefin resin. Propylene resins such as a propylene copolymer and an α-olefin-propylene-ethylene copolymer are exemplified.

As the α-olefin, for example, butene
1, isobutene, pentene-1,3-methylbutene-
1, 4 to 12 carbon atoms such as octene-1 and decene-1
One. The copolymer of propylene and ethylene and / or α-olefin as the olefin-based resin may be any of a binary copolymer, a terpolymer, and a multi-component copolymer.

The ethylene and / or α-olefin component contained in the olefin resin is 0.1 to 20% by weight.
Is preferable, and 0.5 to 10% by weight is more preferable. Preferred olefin-based resins are ethylene random polypropylene having an ethylene component of 0.5 to 5% by weight, an MI value of 0.5 to 5, and a melting point of 130 to 140 ° C, and a homopolypropylene having an MI value of 0.5 to 5, and a melting point of 160 to 165 ° C. And the like. As the ethylene-styrene random copolymer used in the present invention, the general formula (I)

[0020]

Embedded image (Wherein a, b and c each represent an integer of 1 or more)

Preferred are the random or substantially random copolymers represented by As used herein, the term "substantially random copolymer" means that each monomer is arranged with some regularity so that a large block consisting of only one of ethylene and styrene does not occur in its main chain. Means the obtained copolymer. More specifically, for example, as shown in the general formula (I), two or more methylene groups are used so that none of the phenyl groups derived from the styrene monomer are substituted with carbon atoms adjacent to each other on the main chain. Separated copolymers can be defined as "substantially random copolymers."

The term "substantially random" used herein means that the distribution of the monomers in the copolymer is defined as Bern
oulli statistical model, or a first- or second-order Markovian statistical model (POLYME by JC Randall).
R SEQUENCE DETERMINATION,
carbon-13 NMR Method, Acade
mic PressNew York, 1977, p
p. 71-78. reference).

As the substantially random copolymer, 3
In the block of the aromatic monomer having at least one unit, the content of the vinyl or vinylidene aromatic monomer is 15% of the total amount.
% Or less. The ethylene-styrene random copolymer in the present invention does not have a high degree of isotacticity or syndiotacticity. This corresponds to the C ¹³ NMR of the substantially random copolymer of the present invention.
In the spectrum, the peak area corresponding to the main chain methylene and methine carbon indicating either the meso dyad sequence or the racemic dyad sequence does not exceed 75% of the total peak area of the main chain methylene and methine carbon. I do.

The substantially random copolymer may comprise one or more α-olefin monomers, one or more vinyl or vinylidene aromatic monomers, and / or one or more sterically hindered aliphatic or cycloaliphatic aliphatic monomers. It contains polymerized units derived from vinyl or vinylidene monomers, and other optionally polymerizable ethylenically unsaturated monomers.

As the α-olefin, for example, 2 to 20
, Preferably 2 to 12, more preferably 2 to 8 carbon atoms. Specifically, ethylene, propylene, butene-1,4-methyl-1-pentene, hexene-1 or octene-1, or ethylene and one or more other propylene, butene-1,4
-Methyl-1-pentene, hexene-1 or octene-1. Note that these α-olefins do not contain an aromatic moiety. Examples of the vinyl or vinylidene aromatic monomer include those represented by the following chemical formula.

[0026]

Embedded image

Here, R ₁ is selected from the group consisting of hydrogen and an alkyl group containing 1 to 4 carbon atoms, and is preferably hydrogen or methyl. R ₂ is selected from the group consisting of alkyl groups containing each independently hydrogen or 1 to 4 carbon atoms, preferably hydrogen and methyl. Ar is a phenyl group, or 1 to 1 selected from the group consisting of halogen, alkyl having 1 to 4 carbon atoms and alkyl halide having 1 to 4 carbon atoms.
It is a phenyl group substituted by five substituents. n
Is 0-4, preferably 0-2, most preferably 0.

Examples of such vinyl or vinylidene aromatic monomers include styrene, vinyl toluene,
Examples include α-methylstyrene, t-butylstyrene, chlorostyrene, and isomers of these compounds. Of these, styrene and its alkyl- or halogen-substituted derivatives are preferred, for example, lower alkyls of styrene such as styrene, α-methylstyrene [eg ortho-, meta- or para-methylstyrene] (1 to 4 carbon atoms).
Substitutes, halogenated styrene, paravinyltoluene or mixtures thereof are more preferred, and styrene is particularly preferred. “Sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer” refers to an addition-polymerizable vinyl or vinylidene monomer represented by the following general formula.

[0029]

Embedded image

Here, A ₁ is a sterically bulky aliphatic or cycloaliphatic hydrocarbon residue having up to 20 carbon atoms. R ₃ is selected from the group consisting of alkyl groups comprising hydrogen and 1-4 carbon atoms, preferably hydrogen or methyl. R ₄ is each independently hydrogen and 1 to
It is selected from the group consisting of alkyl groups containing 4 carbon atoms and is preferably hydrogen or methyl. R ₃ and A ₁ may be bonded to each other to form a ring. By "sterically bulky" is meant monomers having substituents that cannot be normally addition polymerized at rates comparable to the polymerization of ethylene with standard Ziegler-Natta polymerization catalysts.

The sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer is preferably a monomer in which any one carbon atom in the ethylenically unsaturated bond is tertiary or quaternary substituted. Such substituents include, for example, cyclohexyl, cyclohexenyl,
Examples include cyclic aliphatic hydrocarbon residues such as cyclooctenyl, or cyclic alkyl or aryl substituents thereof, tertiary butyl, norbornyl, and the like. As the sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compound, various isomeric vinyl-ring-substituted derivatives of cyclohexene and substituted cyclohexene, 5-ethylenediene-2-norbornene, and the like are particularly preferable.
-And 4-vinylcyclohexane are particularly preferred.

Other optionally polymerizable ethylenically unsaturated monomers include, for example, norbornene and 1-1
Examples include norbornene substituted with alkyl having 0 carbon atoms or aryl having 6 to 10 carbon atoms. The substantially random ethylene-styrene copolymer in the present invention includes, for example, ethylene / styrene, ethylene / styrene / propylene, ethylene / styrene.
Styrene / octene, ethylene / styrene / butene, ethylene / styrene / norbornene copolymer and the like can be mentioned.

Also, the substantially random ethylene-styrene copolymer may be modified by typical grafting, hydrogenation, functionalization or other conventional methods. The copolymer can be easily converted into a sulfonated or chlorinated derivative by an existing method. This copolymer can be extended or peroxide, silane,
It can be modified by cross-linking, including but not limited to various curing systems using sulphurides, radiation or azides. Details of crosslinking are described in U.S. Patent Application Nos. 921,641 and 921,641, filed August 27, 1997.
No. 642, the contents of both of these applications being incorporated herein by reference. Further, the ethylene-styrene random copolymer in the present invention effectively employs a secondary curing system using a combination of heat, humidity curing and radiation steps. The secondary curing system is 1
On September 29, 995, K. L. Walton and S.M.
V. US Patent Application 53 filed by Karande
Nos. 6,022,022 and 822, which are incorporated herein by reference. For example, it is desirable to employ both a peroxide crosslinking agent and a silane crosslinking agent, a peroxide crosslinking agent and radiation, and a sulfur-containing crosslinking agent and a silane crosslinking agent.

The substantially random copolymer in the present invention is prepared by mixing the diene component as a termonomer at the time of production, followed by the above method or the method of sulfurizing a vinyl group using sulfur as a crosslinking agent, for example. Alternatively, it may be modified by various other crosslinking processes. The substantially random copolymer in the present invention can be obtained from James
C. EP-A-0,416,8 by Stevens et al.
15 and Francis J. et al. Both pseudo-random copolymers, such as described in US Pat. No. 5,703,187 to Timmers, both of which are incorporated herein by reference in their entirety.

Further, the substantially random copolymer in the present invention includes a substantially random terpolymer as described in US Pat. No. 5,872,201.
The substantially random copolymer in the present invention can be produced, for example, by a method of polymerizing a mixture of polymerizable monomers in the presence of one or more metallocene or a geometrically constrained catalyst and various cocatalysts. it can. This polymerization reaction is carried out at a pressure of from atmospheric pressure to 3000 atm.
It is preferably carried out at a temperature up to 200 ° C. Polymerization at higher than the autopolymerization temperature of each monomer and removal of unpolymerized monomer may result in the production of small amounts of homopolymeric polymer due to free radical polymerization.

A catalyst suitable for producing a substantially random copolymer according to the present invention and a method for producing the same are described in, for example, US Patent Application No. 54 filed July 3, 1990.
No. 5,403 (EP-A-416,815), 1991
U.S. Patent Application 702,475 filed on May 20, 1975
(EP-A-514,828), U.S. Patent Application 876,268, filed May 1, 1992 (EP-A
No. 520,732), U.S. patent application Ser. No. 241,523 filed May 12, 1994 and U.S. Pat.
No. 55,438, 5,057,475, 5,096,
867, 5,064,802, 5,132,380
No. 5,189,192, 5,321,106,
5,347,024, 5,350,723, 5,3
Nos. 74,696 and 5,399,635, all of which are incorporated herein by reference.

The substantially random copolymer in the present invention is a compound represented by the following general formula, and can be produced, for example, by the method described in JP-A-7-278230.

[0038]

Embedded image

Here, Cp ₁ and Cp ₂ are each independently a cyclopentadienyl group, an indenyl group, a fluorenyl group or a substituted product thereof. R ₁ and R ₂ each independently represent a hydrogen atom, a halogen atom,
12 hydrocarbon groups, alkoxy groups, or aryloxy groups. M is a Group IV metal, preferably Zr or Hf, most preferably Zr. R ₃ is Cp ₁ and Cp
_An alkylene group or a silanediyl group used to crosslink ₂ .

The copolymer in the present invention comprises a substantially random α-olefin / vinyl or vinylidene aromatic copolymer. This aromatic copolymer is, for example, John
G. FIG. Bradfute et al. (WR Grae & C
o. International Publication WO95 / 32095, R.A.
B. Pannell (Exxon Chemical
Patents, Inc. International Publication WO94 /)
00500 or Plastics Technology
ogy, page 25 (September 1992).

The copolymer in the present invention was prepared in September 1996.
March 4, Francis J. U.S. Patent Application No. 708,809 filed by Timmers et al. Includes a substantially random copolymer containing at least one α-olefin / vinyl aromatic / vinyl aromatic / α-olefin tetrad. . These substantially random copolymers have a special signal in the C ¹³ NMR spectrum with an intensity that is more than three times the noise between peaks. Such a signal is a signal of chemical shift 4
3.70-44.25 ppm and 38.0-38.5
ppm, especially 44.1, 43.9 and 38.
Appears at 2 ppm. In the proton test NMR experiment,
The signal in the chemical shift region of 43.70-44.25 ppm was methine carbon, and 38.0-
The signal at 38.5 ppm indicates a methylene carbon.

The substantially random copolymer in the present invention is described in Longo and Grassi (Makromol.
Chem. 191: 2387-2396 (19
90)) and D'Anniello et al. (Journa)
l of Appliedpolymer Science
ce, 58, 1701-1706 (1995)) [Methylaluminoxane (MAO) and cyclopentadienyltitanium trichloride (CpTiCl
₃ ) has reported the use of a catalyst system], Xu and L
in (polymer Preprints, Am. C
hem. Soc. , Div. Polym. Chem) 3
5, 686, 687 (1994)) [MgCl ₂ / TiCl ₄ / NdCl ₃ / Al (iB
u) Copolymerization of ethylene and styrene using _three catalysts], Lu et al. (Journal of Appl.
ied Polymer Science, 53, 1
453-1460 (1994)) [reporting the copolymerization of ethylene and styrene using TiCl ₄ / NdCl ₃ / MgCl ₂ / Al (Et) ₃ ],
Sernetz and Mulhaupt, (Macrom
l. Chem. Phys. 197, 1071-10
83, 1997) [Me ₂ Si (M
e ₄ Cp) (N-tert-butyl) TiCl ₂ / m
reports the effect of polymerization conditions on copolymers of styrene and ethylene using ethylaluminoxane Ziegler-Natta catalysts].

Ethylene-styrene copolymers produced using bridged metallocene catalysts are available from Ariaki Shiaki and Suzuki (Polymer prints, A.
m. Chem. Soc. , Div. Polym. Che
m. 38, 349 and 350 (1997)) and U.S. Pat. No. 5,652,315 [Sankyo Toatsu Co., Ltd.]. Copolymers of α-olefin / vinyl aromatic monomers such as propylene / styrene and butene / styrene are disclosed in Mitsui Petrochemical Industries, Ltd., US Pat.
No. 96, 5,652, 315, and the methods disclosed in DE 197 11 339 A1 of Denki Kagaku Kogyo KK and U.S. Pat. No. 5,883,213. All of the methods for making these copolymers are incorporated herein. Also, Polymer Preprint 39, 1
No., March 1998, can be used as a blend component in the foam of the present invention.

The ethylene / styrene random copolymer used in the present invention has an ethylene / styrene weight ratio of 30 /
70-75 / 25, more preferably 40 / 60-70 /
30. 75/25 weight ratio of ethylene / styrene
If the styrene content is less, it is difficult to obtain a sufficient foaming retention effect, and if the styrene content is more than 30/70, the compatibility with the polyolefin resin is reduced, and it is difficult to obtain a foam. Not preferred.

The content of the ethylene-styrene random copolymer in the olefin resin composition particles is 5 to 4
It is 5% by weight, more preferably 10 to 35% by weight. When the content of the ethylene-styrene random copolymer is 5
%, It is difficult to obtain sufficient gas retention and flexibility. On the other hand, if the content exceeds 45%, the foamability tends to decrease, which is not preferable in obtaining a low-density foam.

The ethylene-styrene random copolymer is
An α-olefin having from 3 to 20 carbon atoms and containing no aromatic moiety, within a range not to impair the effects of the present invention;
For example, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene or 1-octene can replace part of ethylene.

Similarly, as long as the effects of the present invention are not impaired, derivatives of styrene substituted with alkyl or halogen, such as vinyltoluene, α-methylstyrene, o-, m- or p-methylstyrene, t- Part of styrene can be replaced with butylstyrene, chlorostyrene, etc. or isomers thereof.

Further, the ethylene-styrene random copolymer may be an addition-polymerizable aliphatic vinyl or cycloaliphatic vinyl monomer or a vinylidene monomer, for example, a 1- to 4-alkylene monomer, within a range not to impair the effects of the present invention. , 3
-Or 4-vinylcyclohexane or 5-ethylenediene-2-norbornene may be copolymerized.

The ethylene-styrene random copolymer forms an isotactic styrene homopolymer by homopolymerizing a styrene monomer at a high temperature during the production. If desired, the homopolymer can be separated by extraction with a suitable extractant, for example, acetone or chloroform, etc., provided that its content is within a range not to impair the effects of the present invention. Can be used as it is.

To obtain an olefin resin composition by melt-mixing an olefin resin and an ethylene-styrene random copolymer, preferably used are a commonly used co-kneader, Banbury mixer, Brabender, single screw extruder. A method in which a kneader such as a twin-screw extruder uniformly melts and kneads at a temperature of 180 to 250 ° C. is used. Among these kneaders, it is more preferable to use single-screw and twin-screw extruders from the viewpoint of good productivity.

At the time of melting and mixing, various additives such as an antioxidant, a flame retardant, a flame retardant auxiliary, an antistatic agent and a bubble regulator may be added as required. Melt mixing may be performed multiple times in order to mix the components sufficiently uniformly.
The melt-mixed resin composition is extruded, for example, from a die in a strand shape, cut, and formed into resin composition particles such as pellets.

The method for impregnating the resin composition particles with the foaming agent is not particularly limited, and the resin composition particles are impregnated with the foaming agent in a water suspension system or a gas phase system at a predetermined temperature in a pressure vessel. There is a method to make it. Further, following the melt-mixing by the extruder, during the process up to being extruded from the die, the molten resin composition adjusted to a predetermined temperature and the foaming agent are mixed, for example, extruded from the die into water and cooled. There is also a method of obtaining expandable resin particles without foaming by the above method, but in the present invention, the former method of impregnation is preferred.

The impregnation in the aqueous suspension system is carried out, for example, by dispersing the resin composition particles in an aqueous suspension containing a dispersion stabilizer in a pressure vessel, and then introducing a foaming agent into the system with stirring. ,
It is performed by a method of impregnating at a predetermined temperature. As the dispersion stabilizer, poorly water-soluble inorganic salts such as tribasic calcium phosphate and magnesium pyrophosphate are preferably used.
The proportion of the dispersion stabilizer to be used is preferably about 0.5 to 5% by weight based on the weight of the resin composition particles.

Further, an anionic surfactant such as sodium dodecylbenzenesulfonate may be added to the aqueous suspension for improving the dispersion stability. The amount of the resin composition particles dispersed in the aqueous suspension is preferably 20 to 100 parts by weight, more preferably 20 to 80 parts by weight, based on 100 parts by weight of the aqueous suspension.

In producing the expandable polyolefin resin particles of the present invention, the temperature at which the blowing agent is impregnated into the polyolefin resin composition particles is from the melting point of the resin composition particles to a temperature 10 ° C. higher than the melting point. It is preferably within the range. More preferably, the range is from the melting point of the resin composition particles to a temperature higher by 8 ° C. than the melting point. When the temperature at which the blowing agent is impregnated is lower than the melting point of the resin composition, the bubbles in the expandable resin particles become coarse and uneven,
It is not preferable because the foaming property tends to be low, the moldability of the foamed particles also decreases, and it becomes difficult to obtain a flexible foam. Also,
When impregnated at a temperature higher than the melting point of the resin composition particles by more than 10 ° C., the expandability of the expandable resin is likely to be low, and the obtained foam has fine bubbles, so that the recoverability after compression is reduced. Furthermore, the moldability of the expanded particles is also reduced, the bonding between the resin particles is increased, and the yield is reduced, which is not preferable in production.

The foaming agents used in the present invention include volatile organic foaming agents having a normal pressure boiling point in the range of -50 to 100 ° C., for example, propane, n-butane, i-butane, n-butane.
Pentane, i-pentane, cyclopentane, pentene,
Hydrocarbons such as hexane, methylene chloride, dichlorodifluoromethane, trichloromonofluoromethane, monochlorodifluoromethane, 1,2-dichlorotetrafluoroethane, and halogenated hydrocarbons such as trichlorotrifluoroethane are preferred, and among them, n-butane, i -Butane is particularly preferred. Further, an inorganic gas-based foaming agent such as carbon dioxide and air can also be used.

These foaming agents can be used alone or in combination of two or more. The amount of foaming agent added
Although it may vary depending on the type, it is usually preferably 10 to 50% by weight based on 100% by weight of the olefin-based resin composition particles. More preferably, it is 20 to 30% by weight. When impregnating the foaming agent, in addition to the foaming agent, various additives usually used when forming the foamable resin particles, for example, a foaming auxiliary (solvent, plasticizer) and, if desired, an antistatic agent, A bonding inhibitor or the like at the time of foaming can also be added.

Examples of the foaming aid include toluene, ethylbenzene, cyclohexane, isoparaffin and the like. These foaming aids are usually added in an amount of about 0.1 to 5% by weight based on the olefin resin composition particles. The impregnation time of the blowing agent is not particularly limited, and may vary depending on the size (volume), shape, and the like of the raw material olefin resin composition particles. For example, the volume of the resin composition particles is 3.0 m.
When it is about m ³ , the impregnation is performed for 3 hours or more, preferably 4 hours or more after the desired temperature is reached. When the impregnation time is less than 3 hours, an unimpregnated portion called a core is easily formed at the central portion of the olefin-based resin composition particles, and when the expanded particles are formed, the expanded portion and the unexpanded portion are formed in one expanded particle. It is not preferable because it is mixed. The foam molded article obtained from such foam particles may not have a desired cushioning property.

The impregnation temperature of the foaming agent depends on the type of the olefin resin composition particles. For example, in the case of the olefin resin composition particles having a melting point of 135 ° C., it is about 135 to 145 ° C., preferably 135 to 143. It is about ° C. Each of the expandable olefin-based resin particles, the expanded olefin-based resin particles, and the expanded olefin-based resin molded article of the present invention, when heated from 20 ° C. to 220 ° C. at a rate of 10 ° C./min, has a scanning differential. D obtained by measuring with a calorimeter
The SC curve has two endothermic peaks, and is measured by a scanning differential calorimeter when the temperature is lowered from 220 ° C. to 40 ° C. at a rate of 10 ° C./min with the peak temperature on the higher temperature side of the two endothermic peaks. The difference from the crystallization temperature indicated by the exothermic peak in the DSC curve obtained by
Preferably not more than 59 ° C., and said crystallization temperature,
When the temperature was raised again from 40 ° C. to 220 ° C. at a rate of 10 ° C./min, the difference from the intrinsic peak temperature indicated by the endothermic peak in the DSC curve obtained by the measurement with the scanning differential calorimeter was 40 ° C. Or less, preferably 39 ° C. or less.

The measurement by the scanning differential calorimeter in the present invention is performed by setting 1 to 3 mg of a test sample of expandable resin particles, resin expanded particles, or resin foam molded article in the scanning differential calorimeter, and measuring at 10 ° C./min. After the temperature was raised from 20 ° C to 220 ° C at a rate of temperature increase, the temperature was lowered to 40 ° C at a rate of 10 ° C / min.
Next, from the DSC curve obtained when the temperature is raised again to 220 ° C. at a rate of 10 ° C./min, the peak temperature on the high temperature side, the crystallization temperature, and the intrinsic peak temperature can be obtained.

In the above measurements, the expandable resin particles, expanded resin particles and expanded resin molded article obtained by the present invention are:
For example, when the temperature rises first, it has two endothermic peaks as shown in FIG. 1, and when the temperature falls, it shows an exothermic peak due to crystallization as shown in FIG. Further, at the time of the second temperature rise, only one endothermic (intrinsic) peak is shown as shown in FIG.

In the expandable resin particles, expandable resin particles and expanded resin molded article of the present invention, of the endothermic and exothermic peaks appearing as described above, of the two peaks observed at the first temperature increase, It is recognized that the difference between the peak temperature and the crystallization temperature is 60 ° C. or less, and the difference between the crystallization temperature and the fixed peak temperature is 40 ° C. or less. If the difference between the peak temperature on the high temperature side and the crystallization temperature exceeds 60 ° C., or if the difference between the crystallization temperature and the intrinsic peak temperature exceeds 40 ° C., the expandability of the expandable resin particles decreases, In such a case, the time required for molding in the mold becomes longer, and the rigidity of the obtained foamed molded article is significantly reduced.

The expanded olefin-based resin particles obtained in the present invention can be pre-foamed by heating under stirring to obtain expanded olefin-based resin particles. Specifically, for example, preliminary foaming can be performed by heating the expandable olefin-based resin particles with steam having a vapor pressure of about 0.5 to 5.0 kgf / cm ² G in a preliminary foaming apparatus. The heating time during the prefoaming is, for example, generally 20 to 9
It is about 0 seconds.

The obtained olefin-based resin foamed particles are dispersed in a volatile organic foaming agent or an inorganic gas-based blowing agent having a normal pressure boiling point in the range of -50 to 100 ° C. for 1 to 10 k.
After holding under pressure at gf / cm ² G for about 4 hours, prefoaming may be performed again under the same conditions as above to obtain low-density expanded olefin resin particles. This step may be repeated a plurality of times.

[0065] The bulk density db olefinic resin foamed beads of the present invention is preferably from 0.017~0.2g / cm ^3, more preferably in the range of 0.02~0.1g / cm ^3. If the bulk density is lower than 0.017 g / cm ³ ,
Shrinkage tends to occur during molding, and it is difficult to obtain a molded article having a good appearance. On the other hand, if the bulk density is larger than 0.2 g / cm ³ , it is difficult to obtain sufficient flexibility.

The expanded olefin resin particles of the present invention preferably have a thickness of 10 to 50 μm, more preferably 1 to 50 μm.
It has a surface layer of 0 to 40 μm. Here, the surface layer is
It is a film formed on the surface of the expanded olefin resin particles, and is shown in the image diagram of FIG. 4 and the electrophotograph of FIG.

If the film thickness is less than 10 μm, the foamed film is easily broken during molding, so that sufficient foaming power cannot be obtained and the fusion between foamed particles becomes insufficient. It is easy to become a foam molded article, which is not preferable. When the film thickness is 5
If it exceeds 0 μm, fusion between the foamed particles becomes insufficient due to insufficient softening due to heat and the like, and a foamed molded article having poor physical properties tends to be produced, which is not preferable.

The obtained foamed particles are preferably left at room temperature for about one day, and then, using a volatile organic blowing agent or an inorganic gas-based blowing agent having a normal pressure boiling point in the range of -50 to 100 ° C. After being held under pressure for about 4 hours in a state of 1 to 10 kgf / cm ² G, it is subjected to foam molding.

In the foam molding, a steam having a vapor pressure of about 0.5 to 5.0 kgf / cm ² G, for example, is introduced into a mold which has a desired shape and can close the foamed particles but cannot be sealed. This can be done by introducing it into a mold. The obtained foamed molded product is taken out of the mold after water cooling or air cooling.

The density dm of this foam molded article is 0.017 to
Preferably, it is 0.2 g / cm ³ ,
More preferably, it is 1 g / cm ³ . The density dm is less than 0.017 g / cm ^3, becomes a molded article having poor contraction to facilitate appearance, become a molded article poor in only one flexible weight increase exceeds 0.2 g / cm ^3, both undesirable.

The average cell diameter of the foamed molded article is 100 to 100%.
Preferably it is 500 μm. Average bubble diameter is 100μ
If it is less than m, the foam film is easily broken and the moldability is reduced, and the recovery property when the molded body is compressed is reduced, and it is difficult to obtain a foamed molded body having excellent flexibility. Also,
If the average bubble diameter exceeds 500 μm, the impact resistance and the flexibility become low, which is not preferable.

The foam molded article of the present invention has a more excellent flexibility in that 10% compressive strength, which is one index indicating the flexibility of the foam, satisfies the following expression in relation to the foam density. . S ≦ 0.8− (1/100 dm) (1) S: 10% compressive strength (kgf / cm ² ) dm: Molded product density (g / cm ³ )

[0073]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the present invention, the bulk density of the foamed particles and the density of the foamed molded body were determined by the following formulas (2) and (3) according to a method based on JIS K6767.

Bulk density db (g / cm ³ ) = wb / vb (2) vb: Bulk volume of expanded particles (cm ³ ) wb: Weight of expanded particles (g) Density dm (g / cm ³ ) = w / v (3) v: Volume of foamed molded article (cm ³ ) w: Weight of foamed molded article (g)

The evaluation of the flexibility was performed by measuring the 10% compressive strength of the obtained foamed molded article according to a method in accordance with JIS K6767. That is, the upper surface and the lower surface are parallel, and the whole circumference is a cut surface, and is 50 mm long × 50 mm wide
X A rectangular parallelepiped having a thickness of 25 mm was cut out from the molded foamed body to obtain a sample piece, which was set in a compression tester to 10 mm
The sample was compressed to 10% of the thickness of the specimen at a speed of / min, and the load was measured 20 seconds after the specimen was stopped.

10% compressive strength (kgf / cm ² ) = P / WL (4) P: Load (kgf / c) after compressing 10% and elapse of 20 seconds
m ² ) L: length of sample piece (cm) W: width of sample piece (cm) The heat resistance of the foamed molded article was evaluated by holding the molded article at 90 ° C. under an atmospheric pressure atmosphere for 24 hours, and shrinking after cooling. Evaluation was made by visually observing the appearance such as presence or absence of deformation.

The evaluation of the foaming retention period was performed by the following method. That is, in a pressure vessel, the olefin-based resin composition particles dispersed in the aqueous suspension are impregnated with a foaming agent to form foamable resin particles, and then the pressure vessel is opened to take out the foamable resin particles. Store at ℃ and atmospheric pressure. When the expandable olefin-based resin particles immediately after impregnation are expanded, the bulk density of the expandable particles when the expansion reaches the maximum is db1, and when the expandable olefin-based resin particles are stored for a predetermined time and expanded, Next, the bulk density of the foamed particles when the foaming reached the maximum was defined as db2, and both bulk densities were substituted into the following equation to calculate the foaming retention force.

When the following formula was satisfied, it was evaluated that the foaming property was maintained. (1 / db1)-(1 / db2) <5 (5) In each example, the following olefin-based resins (A to C) and ethylene-styrene random copolymers (d to h) were used.

Olefin resin (MI value is JIS K6
A: Ethylene random polypropylene (MI value 5.
0, melting point 136 ° C., ethylene content 4.7%) B: homopolypropylene (MI value 1.5, melting point 163)
° C) C: Ethylene block polypropylene (MI value 1.8, melting point 162 ° C, ethylene content 9.8%)

Ethylene-styrene random copolymer (manufactured by Dow Chemical Company) (MI value was obtained in accordance with AST MD1238) d: ethylene / styrene weight ratio 25/75 MI value 1.0 e: ethylene / styrene weight Ratio 31/69 MI value 1.0 f: Ethylene / styrene weight ratio 40/60 MI value 0.5 g: Ethylene / styrene weight ratio 75/25 MI value 1.0 h: Ethylene / styrene weight ratio 80/20 MI Value 1.0

Example 1 30 parts by weight of ethylene-styrene random copolymer f and olefin resin A 7
0 parts by weight were melt-mixed at 250 to 260 ° C. using a twin-screw extruder, extruded from a die in a strand shape, and cut into pellet-shaped resin composition particles having a length of 2.0 mm and a diameter of 1.5 mm. . When the obtained resin composition particles were heated from 20 ° C. to 220 ° C. at a rate of 10 ° C./min,
According to a DSC curve obtained by measurement with a scanning differential calorimeter, the melting point of the resin composition particles was 136 ° C.

Next, 5 kg of water and tertiary calcium phosphate as a dispersant were placed in an autoclave having an internal volume of 10 liters.
60 g, 3 g of sodium dodecylbenzenesulfonate as an activator were added, and 1.5 g of ethylenebisstearic acid amide was further added as a foam regulator to obtain an aqueous medium. Next, 3 kg of the resin composition particles were suspended in the aqueous medium and stirred at a stirring speed of 150 rpm. Thereafter, 750 g of isobutane as a volatile foaming agent was injected by using nitrogen pressure, and the temperature was raised to 144 ° C.
The impregnation was carried out for a certain period of time, and after cooling to 20 ° C., the product was taken out by dehydration to obtain expandable olefin-based resin particles.

The DSC curves of the obtained expandable resin particles obtained by scanning differential calorimetry are shown in FIGS. 1 to 3, wherein the high temperature side peak temperature is 155.4 ° C. and the crystallization temperature is 97.7.
C., the intrinsic peak temperature was 136.0 ° C., the difference between the high-temperature side peak temperature and the crystallization temperature was 57.7 ° C., and the difference between the intrinsic peak and the crystallization temperature was 38.3 ° C. Immediately after taking out the obtained expandable olefin-based resin particles from the pressure-resistant container,
When heated in a prefoaming machine for 30 seconds in an atmosphere of steam pressure of 4.5 kgf / cm ² G, the maximum foaming bulk density was 0.0
It showed 45 g / cm ³ .

The expandable resin particles have the formula (5)
The period for filling and maintaining the foaming property was 15 days.
Then, for foam molding, under the above-mentioned pre-foaming conditions,
Degree 0.045g / cm ^ThreeWas obtained. Obtained departure
The film thickness of the surface layer of the foam particles was 30 μm. This foamed grain
The DSC curve of the child is the same as that shown for the expandable resin particles.
And the high-temperature side peak temperature is 155.3 ° C. and the crystallization temperature
Is 97.8 ° C., the intrinsic peak temperature is 135.5 ° C.,
Difference between high temperature peak temperature and crystallization temperature is 57.5 ℃, unique
The difference between the peak and the crystallization temperature was 37.7 ° C.

After leaving the foamed particles at 23 ° C. for one day, keeping the foamed particles in the air at 5.0 kgf / cm ² G for 5 hours, the foamed particles can be closed but sealed. Into a mold that does not have a vapor pressure of 4.0 kgf / cm ²
G steam was introduced into the mold for 20 seconds and heated, then cooled to a density of 0.046 g / cm ³ and an average bubble diameter of 350 μm.
And a 10% compressive strength of 0.48 kgf / cm ² , and a foam molded article satisfying the formula (1) and having excellent flexibility was obtained.

The foamed molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The DSC curve of the foamed molded product is the same as that of the expandable resin particles. The high-temperature side peak temperature is 155.6 ° C, the crystallization temperature is 97.5 ° C, and the intrinsic peak temperature is 136.0 ° C. The difference between the high temperature side peak temperature and the crystallization temperature was 57.1 ° C., and the difference between the intrinsic peak and the crystallization temperature was 38.5 ° C.

Example 2 Expandable resin particles were obtained in the same manner as in Example 1 except that olefin resin B was used instead of olefin resin A, and the impregnation temperature was 170 ° C. When the obtained expandable resin particles were expanded immediately after being taken out in the same manner as in Example 1, the highest expanded bulk density was 0.049.
g / cm ³ . The period during which the expandability of the expandable resin particles could be maintained was 15 days.

Next, foamed particles having a bulk density of 0.049 g / cm ³ were obtained under the same prefoaming conditions as in Example 1. The thickness of the surface layer of the obtained expanded particles was 35 μm. The expanded particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.0
A foam molded article having 50 g / cm ³ , an average cell diameter of 300 μm, a 10% compressive strength of 0.5 kgf / cm ² and excellent flexibility satisfying the formula (1) was obtained. The foam molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The details of the results are shown in Tables 1 and 2.

Example 3 Expandable resin particles were obtained in the same manner as in Example 1 except that olefin resin C was used in place of olefin resin A and the impregnation temperature was 170 ° C. When the obtained resin particles were foamed immediately after being taken out in the same manner as in Example 1, the highest foamed bulk density was 0.051 g / c.
m ³ . The period during which the expandability of the expandable resin particles could be maintained was 15 days.

Next, foamed particles having a bulk density of 0.051 g / cm ³ were obtained under the same prefoaming conditions as in Example 1. The thickness of the surface layer of the obtained expanded particles was 40 μm. The expanded particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.0
A foam molded article having 52 g / cm ³ , an average cell diameter of 350 μm, a 10% compressive strength of 0.51 kgf / cm ² and excellent flexibility satisfying the formula (1) was obtained. The foam molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The details of the results are shown in Tables 1 and 2.

Example 4 Expandable resin particles were obtained in the same manner as in Example 1 except that ethylene-styrene copolymer e was used instead of ethylene-styrene copolymer f. When the obtained expandable resin particles were expanded immediately after being taken out in the same manner as in Example 1, the highest expanded bulk density was 0.046 g / c.
m ³ . The period during which the expandability of the expandable resin particles could be maintained was 15 days. Next, foamed particles having a bulk density of 0.046 g / cm ³ were obtained under the same preliminary foaming conditions as in Example 1. The thickness of the surface layer of the obtained expanded particles was 25 μm.

The foamed particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.047 g / cm ³ and an average cell diameter of 260 μm.
A 10% compressive strength of 0.46 kgf / cm ² and a foamed article excellent in flexibility satisfying the formula (1) were obtained. The foam molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The details of the results are shown in Tables 1 and 2.

Example 5 Expandable resin particles were obtained in the same manner as in Example 1, except that ethylene-styrene copolymer g was used instead of ethylene-styrene copolymer f.
When the obtained expandable resin particles were expanded immediately after being taken out in the same manner as in Example 1, the highest expanded bulk density was 0.044 g /
cm ³ . The period during which the expandability of the expandable resin particles could be maintained was 14 days.

Next, foamed particles having a bulk density of 0.044 g / cm ³ were obtained under the same prefoaming conditions as in Example 1. The thickness of the surface layer of the obtained expanded particles was 40 μm. The expanded particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.0
A foam molded article having 44 g / cm ³ , an average cell diameter of 340 μm, a 10% compressive strength of 0.49 kgf / cm ² and excellent flexibility satisfying the formula (1) was obtained. The foam molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The details of the results are shown in Tables 1 and 2.

Example 6 Expandable resin particles were obtained in the same manner as in Example 1, except that the ethylene-styrene copolymer f was 7 parts by weight and the olefin resin A was 93 parts by weight.
When the obtained resin particles were foamed immediately after being taken out in the same manner as in Example 1, the highest foamed bulk density was 0.043 g / cm ^3.
showed that. The period during which the expandability of the expandable resin particles could be maintained was 10 days.

Next, foamed particles having a bulk density of 0.043 g / cm ³ were obtained under the same prefoaming conditions as in Example 1. The film thickness of the surface layer of the obtained foamed particles was 45 μm. The expanded particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.0
43 g / cm ³ , average bubble diameter 400 μm, 10%
A foam molded article having a compressive strength of 0.51 kgf / cm ² and excellent flexibility satisfying the formula (1) was obtained. The foam molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The details of the results are shown in Tables 1 and 2.

Example 7 Expandable resin particles were obtained in the same manner as in Example 1, except that the ethylene-styrene copolymer f was 43 parts by weight and the olefin resin A was 57 parts by weight. When the obtained expandable resin particles were expanded immediately after being taken out in the same manner as in Example 1, the highest expanded bulk density was 0.047.
g / cm ³ . The period during which the expandability of the expandable resin particles could be maintained was 17 days.

Next, foamed particles having a bulk density of 0.047 g / cm ³ were obtained under the same prefoaming conditions as in Example 1. The film thickness of the surface layer of the obtained expanded particles was 15 μm. The expanded particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.0
48 g / cm ³ , average bubble diameter 140 μm, 10%
A foamed molded article having a compressive strength of 0.44 kgf / cm ² and excellent flexibility satisfying the formula (1) was obtained. The foam molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The details of the results are shown in Tables 1 and 2.

Example 8 Expandable resin particles were obtained in the same manner as in Example 1 except that 750 g of n-butane was used instead of 750 g of isobutane as a volatile blowing agent. When the obtained expandable resin particles were expanded immediately after being taken out in the same manner as in Example 1, the highest expandable bulk density was 0.1 g / cm ³ . The period during which the expandability of the expandable resin particles can be maintained is 1
0 days.

Next, foamed particles having a bulk density of 0.13 g / cm ³ were obtained under the same prefoaming conditions as in Example 1. The thickness of the surface layer of the obtained expanded particles was 50 μm. The expanded particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.15.
g / cm ³ , the average cell diameter was 270 μm, the 10% compressive strength was 0.62 kgf / cm ² , and a foamed article excellent in flexibility satisfying the formula (1) was obtained. The foam molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The details of the results are shown in Tables 1 and 2.

Example 9 The bulk density obtained in Example 1 was 0.0
The expanded particles of 45 g / cm ³ were left at 23 ° C. for 12 hours. Then, the foamed particles are subjected to 5k using nitrogen in a pressure vessel.
g / cm ² for 12 hours and then again with a prefoaming machine under an atmosphere of steam pressure of 4.5 kgf / cm ^2.
The mixture was heated for 2 seconds to foam, and foamed particles having a bulk density of 0.017 g / cm ³ were obtained. The foamed particles which were foamed twice had a surface layer having a thickness of 15 μm.

The foamed particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.018 g / cm ³ and an average cell diameter of 450 μm.
m, a 10% compressive strength of 0.17 kgf / cm ² , and a foamed article excellent in flexibility satisfying the formula (1) was obtained. The foam molded article thus obtained had a uniform cell diameter, a small shrinkage of the molded article, and a beautiful appearance. The details of the results are shown in Tables 1 and 2.

[Comparative Example 1] Expandable resin particles were obtained in the same manner as in Example 1 except that only the olefin resin A was used without adding the ethylene-styrene copolymer. When the obtained expandable resin particles were expanded immediately after being taken out in the same manner as in Example 1, the maximum expanded bulk density was 0.066 g / c.
m ³ , showing a large value. The period during which the expandability of the expandable resin particles can be maintained was as short as 10 minutes.

Next, foamed particles having a bulk density of 0.066 g / cm ³ were obtained under the same prefoaming conditions as in Example 1. The thickness of the surface layer of the obtained expanded particles was 60 μm. The expanded particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.0
68 g / cm ³ , average bubble diameter 600 μm, 10%
A foam molded article having a compressive strength of 1.3 kgf / cm ² , not satisfying the formula (1), and having poor flexibility was obtained. The foam molded article thus obtained was poor in appearance, probably due to low foamability. The details of the results are shown in Tables 1 and 2.

Comparative Example 2 A general-purpose linear low-density polyethylene (MI value 0.9, melting point 124 ° C.) was used in place of the ethylene-styrene random copolymer f.
Expandable resin particles were obtained in the same manner as in Example 1. When the obtained resin particles were foamed immediately after being taken out in the same manner as in Example 1, the highest foamed bulk density was 0.061 g / cm ³ , which was a large value.

The period during which the expandability of the expandable resin particles can be maintained was as short as 10 minutes. Next, foamed particles having a bulk density of 0.061 g / cm ³ were obtained under the same preliminary foaming conditions as in Example 1. The thickness of the surface layer of the obtained expanded particles was 60 μm. The foamed particles were molded in a mold in the same manner as in Example 1,
A foam molded article having a density of 0.065 g / cm ³ , an average cell diameter of 650 μm, a 10% compressive strength of 1.1 kgf / cm ² and not satisfying the formula (1) and having poor flexibility was obtained.
The foam molded article thus obtained had poor appearance. The details of the results are shown in Tables 1 and 2.

[Comparative Example 3] A general-purpose polystyrene (MI value 1.
0, the molecular weight Mw was 180,000), and an attempt was made to obtain expandable resin particles in the same manner as in Example 1. These resin particles were not foamed by the same method as in Example 1, and foamed particles and foamed molded articles could not be obtained. The details of the results are shown in Tables 1 and 2.

[Comparative Example 4] Expandable resin particles were obtained in the same manner as in Example 1 except that the impregnation temperature was set at 134 ° C. When the obtained expandable resin particles were expanded immediately after being taken out in the same manner as in Example 1, the maximum expanded bulk density was 0.063 g /
cm ³ , which was a large value. The period during which the expandability of the expandable resin particles could be maintained was as short as 60 minutes. Then
The bulk density is 0.063 g under the same pre-foaming conditions as in Example 1.
/ Cm ³ of foamed particles. The thickness of the surface layer of the obtained expanded particles was 65 μm. The expanded particles were molded in a mold in the same manner as in Example 1, and had a density of 0.065 g / cm ³ , an average cell diameter of 700 μm, and a 10% compressive strength of 0.7 kgf.
/ Cm ² , which did not satisfy the formula (1), and a foamed molded article having poor flexibility was obtained. The foam molded article thus obtained had poor appearance. The details of the results are shown in Tables 1 and 2.

[Comparative Example 5] Expandable resin particles were obtained in the same manner as in Example 1 except that the impregnation temperature was changed to 148 ° C.
Bonding between the resin particles occurred during the impregnation, and the yield was low. When the obtained expandable resin particles were expanded immediately after being taken out in the same manner as in Example 1, the maximum expanded bulk density was 0.06.
The value was ³ g / cm ³ , which was a large value. The period during which the expandability of the expandable resin particles can be maintained was as short as one day.

Next, foamed particles having a bulk density of 0.063 g / cm ³ were obtained under the same preliminary foaming conditions as in Example 1. The film thickness of the surface layer of the obtained foamed particles was 55 μm. The expanded particles were molded in a mold in the same manner as in Example 1 to obtain a density of 0.0
65 g / cm ³ , average bubble diameter of 550 μm, 10%
A foamed molded article having a compressive strength of 0.65 gf / cm ² , not satisfying the formula (1), and having poor flexibility was obtained. The foam molded article thus obtained had poor appearance. The details of the results are shown in Tables 1 and 2.

Comparative Example 6 An attempt was made to obtain expandable resin particles in the same manner as in Example 1, except that the ethylene-styrene random copolymer d was used instead of the ethylene-styrene random copolymer f. . The expandable resin particles are
With the above foaming method, foaming did not occur, and foamed particles and foamed molded articles could not be obtained. The details of the results are shown in Tables 1 and 2.

Comparative Example 7 Expandable resin particles were obtained in the same manner as in Example 1, except that the ethylene-styrene random copolymer h was used instead of the ethylene-styrene random copolymer f. When the obtained resin particles were foamed immediately after being taken out in the same manner as in Example 1, the highest foamed bulk density was 0.063 g / cm ³ , which was a large value. The period during which the expandability of the expandable resin particles can be maintained was as short as one day.

Then, the mixture was treated under the same pre-expansion conditions as in Example 1 to obtain expanded particles having a bulk density of 0.063 g / cm ³ . The thickness of the surface layer of the obtained expanded particles was 60 μm. The foamed particles were molded in a mold in the same manner as in Example 1, and had a density of 0.064 g / cm ³ , an average cell diameter of 590 μm, and a 10% compressive strength of 0.9 kgf / cm ^2. A foam molded article that was not satisfied and was inferior in flexibility was obtained. The foam molded article thus obtained had poor appearance. The details of the results are shown in Tables 1 and 2.

Comparative Example 8 Expandable resin particles were obtained in the same manner as in Example 1, except that the ethylene-styrene random copolymer f was 3 parts by weight and the olefin resin A was 97 parts by weight. When the obtained expandable resin particles are expanded immediately after being taken out in the same manner as in Example 1, the maximum expanded bulk density is 0.1%.
063 g / cm ³ , which was a large value. The period during which the expandability of the expandable resin particles could be maintained was as short as 60 minutes.

Then, the mixture was treated under the same pre-expansion conditions as in Example 1 to obtain expanded particles having a bulk density of 0.064 g / cm ³ . The film thickness of the surface layer of the obtained foamed particles was 55 μm. The foamed particles were molded in a mold in the same manner as in Example 1, and had a density of 0.065 g / cm ³ , an average cell diameter of 550 μm, and a 10% compressive strength of 1.3 kgf / cm ^2. A foam molded article which was not satisfied and was inferior in flexibility was obtained.
The details of the results are shown in Tables 1 and 2.

Comparative Example 9 An attempt was made to obtain expandable resin particles in the same manner as in Example 1 except that the ethylene-styrene random copolymer f was 49 parts by weight and the olefin resin A was 51 parts by weight. Was. The expandable resin particles did not expand in the same manner as in Example 1, and no expanded particles and expanded molded articles could be obtained. The details of the results are shown in Tables 1 and 2.

[0117]

[Table 1]

[0118]

[Table 2]

As is clear from Tables 1 and 2, it can be seen that the expandable resin particles of the present invention can maintain the expandability that can be used for expansion for a long time. Further, the surface layer of the foamed particles obtained from the foamable resin particles of the present invention has a film thickness suitable for later in-mold molding, and the obtained foamed molded article has excellent flexibility, low density, and appearance. Is also excellent.

[0120]

According to the present invention, the expandable resin particles of the present invention can maintain the expandability which can be used for foaming for a long time. Furthermore, the foamed resin particles produced from the foamable resin particles have excellent moldability in a wide range of foaming densities. The foamed resin article obtained from the foamed resin particles is substantially non-crosslinked, excellent in recyclability, excellent in flexibility and the like in a wide foaming density range, and excellent in appearance.

Further, since the period during which the foaming property can be maintained becomes longer, the foaming resin particles can be transported in the form of foaming resin particles instead of bulky foaming particles, and the transportation cost can be reduced. In addition, the foamed molded article of the present invention has good flexibility, so that it can be applied to a wide range of applications, and because of its low density, reduces the amount of resin used, saves resources,
Cost reduction becomes possible. Furthermore, since it is non-crosslinked, it is excellent in recyclability and can easily cope with environmental problems.

[Brief description of the drawings]

FIG. 1 is a DSC curve showing the peak temperature on the high temperature side of the expandable resin particles of the present invention.

FIG. 2 shows the crystallization temperature of the expandable resin particles of the present invention.
It is an SC curve.

FIG. 3 is a DSC curve showing an intrinsic peak temperature of the expandable resin particles of the present invention.

FIG. 4 is an image diagram showing a surface layer of the foamed resin particles of the present invention.

FIG. 5 is an electrophotograph of a cut surface of the foamed resin particles of the present invention.

Continued on the front page F term (reference) 4F074 AA17 AA17B AA24 AA25 AA32 AB02 AB03 AE07 BA32 BA35 BA36 BA37 BA38 BA39 BA40 BA44 BA53 BA54 BA55 BA57 BA59 CA23 CA24 CA34 CA35 CA38 CC04X CC22X DA02 DA08 DA19 DA33 4J002 BB041BB EA016 EB026 EB066 FA091 FA092 FD326 GG02

Claims (14)

[Claims] An expandable olefin-based resin particle obtained by impregnating a foaming agent with olefin-based resin composition particles obtained by melt-mixing an olefin-based resin and an ethylene-styrene random copolymer. Resin particles are 10
DSC obtained by measuring with a scanning differential calorimeter when the temperature was raised from 20 ° C. to 220 ° C. at a temperature rising rate of ° C./min.
The curve has two endothermic peaks. When the temperature of the expandable resin particles is decreased from 220 ° C. to 40 ° C. at a rate of 10 ° C./min from the high end side of the two endothermic peaks, the scanning type D obtained by measuring with a differential calorimeter
The difference between the crystallization temperature shown as an exothermic peak in the SC curve is 60 ° C. or less, and the crystallization temperature;
When the expandable resin particles are heated again from 40 ° C. to 220 ° C. at a rate of 10 ° C./min, an intrinsic peak temperature shown as an endothermic peak in a DSC curve obtained by a scanning differential calorimeter The foamable olefin-based resin particles having a difference of not more than 40 ° C. 2. The expandable olefin resin particles according to claim 1, wherein the olefin resin is a propylene resin. 3. The expandable olefin resin particles according to claim 1, wherein the content of the ethylene-styrene random copolymer is 5 to 45% by weight. 4. The weight ratio of ethylene / styrene in the ethylene-styrene random copolymer is 30 / 70-7.
The expandable olefin-based resin particles according to any one of claims 1 to 3, wherein the ratio is 5/25. 5. An ethylene-styrene random copolymer represented by the general formula: (Wherein, a, b and c each represent an integer of 1 or more). The expandable olefin-based resin particles according to any one of claims 1 to 4, wherein 6. An expanded olefin-based resin particle obtained by pre-expanding the expandable olefin-based resin particle according to any one of claims 1 to 5, wherein the resin expanded particle is:
When the temperature was raised from 20 ° C. to 220 ° C. at a rate of 10 ° C./min, D obtained by measurement with a scanning differential calorimeter
When the SC curve has two endothermic peaks and the temperature of the peak on the higher temperature side of the two endothermic peaks and the temperature of the resin expanded particles are decreased from 220 ° C. to 40 ° C. at a rate of 10 ° C./min, scanning is performed. The difference between the crystallization temperature shown as an exothermic peak in a DSC curve obtained by measurement with a type differential calorimeter is 60 ° C. or less, and the crystallization temperature is increased by 10 ° C./min. 40 ° C at heating rate
Wherein the difference from the intrinsic peak temperature shown as an endothermic peak in a DSC curve obtained by measuring with a scanning differential calorimeter when the temperature is raised again to 220 ° C. is 40 ° C. or less. Expanded particles. 7. An expanded olefin resin particle having a thickness of 10
The expanded olefin-based resin particles according to claim 6, which has a surface layer having a thickness of from 50 m to 50 m. 8. An olefin resin foam molded article obtained by in-mold molding the olefin resin foam particles according to claim 6 or 7, wherein the resin foam molded article has a temperature of 10 ° C. /
When the temperature is raised from 20 ° C to 220 ° C at a heating rate of
The DSC curve obtained by a scanning differential calorimeter has two endothermic peaks, and the peak temperature of the higher end side of the two endothermic peaks and the temperature of the resin foam molded article are 10 ° C.
When the temperature is lowered from 220 ° C. to 40 ° C. at a temperature lowering rate of / min, the difference from the crystallization temperature shown as an exothermic peak in a DSC curve obtained by measuring with a scanning differential calorimeter is 60 ° C. or less, and The crystallization temperature and the temperature of the resin foam molded article are reduced from 40 ° C. to 22 ° C. at a rate of 10 ° C./min.
When the temperature is raised to 0 ° C. again, a difference from an intrinsic peak temperature shown as an endothermic peak in a DSC curve obtained by measuring with a scanning differential calorimeter is 40 ° C. or less. Molded body. 9. The density is 0.017 to 0.2 g / cm ³ and the 10% compressive strength is as follows: S ≦ 0.8− (1/100 dm) (1) S: 10% compressive strength (kgf / Cm ² ) The olefin resin foam molded article according to claim 8, which satisfies dm: molded article density (g / cm ³ ). 10. An olefin-based resin composition particle obtained by melt-mixing an olefin-based resin and an ethylene-styrene random copolymer, in a range from the melting point of the resin composition particle to a temperature higher by 10 ° C. than the melting point. A method for producing expandable olefin-based resin particles, comprising impregnating a foaming agent with a foaming agent. 11. The method for producing expandable olefin resin particles according to claim 10, wherein the olefin resin composition particles are dispersed in an aqueous suspension in a pressure vessel and impregnated with a blowing agent. . 12. A method for producing expanded olefin resin particles, wherein the expandable olefin resin particles obtained by the method according to claim 10 or 11 are pre-expanded. 13. A pre-expansion is further performed once or more times by using the expanded olefin resin particles obtained by the method according to claim 12 in a gas atmosphere containing a foaming agent while applying pressure. For producing expanded olefin resin particles. 14. A method for producing a foamed olefin-based resin article, comprising molding the foamed olefin-based resin particles obtained by the method according to claim 12 in a mold.