JP2020045484A - Masterbatch for foam molding, and foam molded body - Google Patents

Abstract

To provide a masterbatch for foam molding capable of obtaining a foam molding which can be suitably used not only in molding to which a strong shear force is applied but also in molding requiring low molding temperature, has a high foam ratio, reduces a foam speed and has good appearance quality, and a foam molded body using the masterbatch for foam molding.SOLUTION: A masterbatch for foam molding contains a base resin and a thermally expandable microcapsule, in which the base resin contains a resin having a melt flow rate of 0.1-60 g/10 min and a melting point of 70-110°C, the thermally expandable microcapsule has an average particle size of 15-35 μm, and a content of the thermally expandable microcapsule is 52-70 wt.%.SELECTED DRAWING: None

Description

INDUSTRIAL APPLICABILITY The present invention can be suitably used for molding in which a strong shearing force is applied, or molding in which a low molding temperature is required, and has a high expansion ratio, a suppressed foaming speed, and a good appearance quality. The present invention relates to a masterbatch for foam molding capable of producing the same. The present invention also relates to a foamed molded article using the foam molding masterbatch.

Plastic foam can exhibit heat insulation, heat insulation, sound insulation, sound absorption, vibration absorption, light weight, etc. depending on the foam material and the state of the formed bubbles, so it can be used in various applications. Used. As a method for producing such a plastic foam, there is a method in which a masterbatch containing a chemical foaming agent is heated to foam and mold. However, a masterbatch containing a chemical foaming agent may not foam even when heated, and there is a problem that the foaming agent may be rapidly decomposed in an injection foaming molding machine, and is difficult to handle. Also, depending on the type of the resin, a sufficient expansion ratio cannot be obtained, and it may be difficult to obtain a desired hardness as a molded article.

On the other hand, Patent Document 1 discloses that using a masterbatch pellet of an ethylene-α-olefin copolymer containing a chemical foaming agent, regardless of the type of resin, the hardness and the foaming ratio are high and uniform bubbles are formed. It is described that an injection-molded molded article is obtained.
However, when the chemical foaming agent is thermally decomposed, a foaming residue is generated at the same time as the decomposition gas, and the residue remaining on the molded body sometimes affects the adhesive performance of the molded body. In addition, when a chemical foaming agent is used, not all of the cells become closed cells, and there are inevitably parts that become open cells, and there is a problem that it is difficult to obtain a foam molded article having high airtightness.

Patent Literature 2 describes a foamed resin masterbatch using a polyolefin resin or a styrene resin as a base resin, and using a heat-expandable microcapsule as a foaming agent instead of a chemical foaming agent.
However, when the heat-expandable microcapsules described in Patent Document 2 are used, the expansion ratio of the obtained foam is low, and it has been difficult to make the closed cells of the obtained foam a constant size.

On the other hand, Patent Literature 3 discloses a foam composite by foaming and molding using a resin composition in which a masterbatch containing thermally expandable microcapsules and a masterbatch containing a chemical foaming agent are blended. A method for making a board is described.
However, even when such a method is used, although a slight improvement in the expansion ratio is observed, the expansion ratio of the molded product is still low, and it is possible to obtain the desired performance such as light weight and heat insulation. could not. Further, it was difficult to obtain a product having good appearance quality.

Further, Patent Document 4 discloses a synthetic resin composition containing heat-expandable microcapsules and a base resin, and a method for producing the same. In such a synthetic resin composition, by using a base resin having a melt flow rate within a predetermined range, the miscibility of the heat-expandable microcapsules and the base resin can be maintained without breaking the shell of the heat-expandable microcapsules. , With excellent affinity.

JP 2000-178372 A JP-A-11-343362 JP 2005-212377 A JP-A-2002-264173

INDUSTRIAL APPLICABILITY The present invention can be suitably used for molding in which a strong shearing force is applied, or molding in which a low molding temperature is required, and has a high expansion ratio, a suppressed foaming speed, and a good appearance quality. It is an object of the present invention to provide a masterbatch for foam molding capable of obtaining the following. Another object of the present invention is to provide a foam molded article using the masterbatch for foam molding.

The present invention is a masterbatch for foam molding containing a base resin and heat-expandable microcapsules, wherein the base resin has a melt flow rate of 0.1 to 60 g / 10 minutes and a melting point of 70 to 110 ° C. The heat-expandable microcapsules containing a resin are a masterbatch for foam molding having an average particle diameter of 15 to 35 μm and a content of the heat-expandable microcapsules of 52 to 70% by weight.
Hereinafter, the present invention will be described in detail.

The present inventors have conducted intensive studies and as a result, using a resin having a predetermined melt flow rate and a melting point as a base resin, and using a heat-expandable microcapsule as a foaming component, the average particle diameter and content of the heat-expandable microcapsule are determined to a predetermined value. It has been found that when it is within the range, it can be suitably used for molding in which a strong shearing force is applied and molding in which a low molding temperature is required. Further, they have found that a foamed molded article having a high expansion ratio and good appearance quality can be obtained, and have completed the present invention.

The masterbatch for foam molding of the present invention contains a base resin.
In the present invention, a resin having a predetermined melt flow rate and a melting point is contained as the base resin. This makes it possible to suppress the foaming speed. In addition, a foam molded article having good appearance quality can be manufactured.

The lower limit of the melt flow rate of the resin constituting the base resin is 0.1 g / 10 minutes, and the upper limit is 60 g / 10 minutes.
By setting the melt flow rate to 0.1 g / 10 min or more, deformation of the master batch can be prevented, and by setting the melt flow rate to 60 g / 10 min or less, the appearance of the obtained molded article is improved. be able to.
A preferred lower limit of the melt flow rate is 1.0 g / 10 minutes, and a preferred upper limit is 55 g / 10 minutes.
In addition, the melt flow rate means an index indicating the fluidity of the resin, and a fixed amount of synthetic resin is heated at a predetermined temperature (for example, 190 ° C.) in a cylindrical container heated by a heater. It is indicated by the amount of resin extruded per 10 minutes from an opening (nozzle) provided at the bottom of the container by applying a pressure (for example, 2.16 kg). The unit used is g / 10 minutes, and is measured by the measurement method specified in JIS K7210-1.

The lower limit of the melting point of the resin constituting the base resin is 70 ° C., and the upper limit is 110 ° C.
By setting the melting point to 70 ° C. or higher, blocking of the master batch can be prevented, and by setting the melting point to 110 ° C. or lower, foaming during production of the master batch can be suppressed.
A preferred lower limit of the melting point is 75 ° C, and a preferred upper limit is 105 ° C.
In addition, the melting point means a peak temperature of a melting peak obtained by DSC measurement.

The base resin preferably contains at least one selected from the group consisting of acrylic resins, polyethylene resins, and olefin elastomers. This makes it possible to suppress the foaming speed. In addition, a foam molded article having good appearance quality can be manufactured.

Examples of the acrylic resin include homopolymers of acrylic monomers such as acrylic acid, methacrylic acid, and (meth) acrylic acid esters, and (meth) acrylic copolymers containing these.
Examples of the (meth) acrylic acid ester include (meth) acrylates having an alkyl group having 1 to 10 carbon atoms, and specifically, methyl (meth) acrylate, ethyl (meth) acrylate, and isopropyl (meth) acrylate. A) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and the like. Examples of the (meth) acrylate include n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and n-octyl (meth) acrylate. There is. However, the above (meth) acrylic acid means acrylic acid or methacrylic acid.

In the above (meth) acrylic copolymer, other comonomers copolymerized with the acrylic monomer include α-olefin, styrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, vinyl acetate and the like. Can be mentioned.
Among them, a copolymer of an acrylic monomer and an α-olefin is preferable, and an ethylene-methyl methacrylate copolymer (EMMA) is more preferable.
These comonomers can be present in the acrylic resin in the form of a random copolymer, a graft copolymer, or a block copolymer.

In the case of the (meth) acrylic copolymer, the lower limit of the content of the acrylic monomer (weight% of the acrylic monomer component based on the entire (meth) acrylic copolymer) is preferably 10% by weight, and the upper limit is preferably 50% by weight. %.
By using a (meth) acrylic copolymer having an acrylic monomer content within the above range, moldability and dispersibility of the heat-expandable microcapsules can be improved.

The acrylic resin preferably has a weight average molecular weight of 10,000 or more.
By setting the weight average molecular weight within the above range, a molded article having excellent appearance can be obtained.
The weight average molecular weight (Mw) is measured as a molecular weight in terms of polystyrene by a gel permeation chromatography (GPC) method.

The acrylic resin preferably has a melting point of 75 to 105 ° C. Thereby, a foam molded article having excellent appearance can be obtained. In addition, the melting point means a peak temperature of a melting peak obtained by DSC measurement.

The lower limit of the melt flow rate of the acrylic resin is preferably 1 g / 10 minutes, and the upper limit is preferably 50 g / 10 minutes.
By setting the memelt flow rate to 1 g / 10 min or more, deformation of the master batch can be prevented, and by setting the memelt flow rate to 50 g / 10 min or less, the appearance of the obtained molded article is improved. Can be.

Examples of the polyethylene resin include a low density polyethylene resin, a medium density polyethylene resin, a linear low density polyethylene resin, and a high density polyethylene resin. Especially, a low density polyethylene resin is preferable.

Examples of the olefin-based elastomer include copolymers containing an olefin as a main component. Examples of the olefin as a main component include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene. Α-olefin copolymer. Among them, a propylene-based elastomer is preferable.
As the olefin-based elastomer, those having a diene component in addition to the olefin can be used. EPDM resin (ethylene-propylene-diene rubber) is preferable as the olefin-based elastomer having such a diene component.

In the base resin, at least one selected from the group consisting of an acrylic resin, a polyethylene resin, and an olefin elastomer may be 100% by weight, and one or more other resin components may be appropriately mixed. It is possible.
When the other resin component is used, the ratio of at least one selected from the group consisting of the acrylic resin, polyethylene resin, and olefin elastomer is preferably 80% by weight or more, and more preferably 90% by weight. More preferably, it is less than 100% by weight.

The other resin component includes a rubber component. Examples of the rubber component include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), chloroprene rubber (CR), Urethane rubber (U), silicone rubber (Si) and the like can be used. Further, one or more kinds selected from the above rubber components can be used in combination.

In addition, a general thermoplastic resin may be used as the other resin component.
Examples of the thermoplastic resin include general thermoplastic resins such as polyvinyl chloride, polypropylene, polypropylene oxide, and polystyrene, and engineering plastics such as polybutylene terephthalate, nylon, polycarbonate, and polyethylene terephthalate. Among these, at least one selected from the group consisting of polypropylene and polystyrene is preferable.

The preferred lower limit of the content of the base resin in the masterbatch for foam molding of the present invention is 40% by weight, and the preferred upper limit is 50% by weight. If the content of the base resin is less than 40% by weight, foaming may occur during the preparation of the masterbatch, and it may not be possible to form a masterbatch. If the content of the base resin exceeds 50% by weight, a desired expansion ratio may be obtained. May not be possible.

The masterbatch for foam molding of the present invention contains heat-expandable microcapsules.
The lower limit of the content of the thermally expandable microcapsules in the masterbatch for foam molding of the present invention is 52% by weight, and the upper limit is 70% by weight. By setting the content of the heat-expandable microcapsules to 52% by weight or more, a desired expansion ratio can be obtained. By setting the content of the heat-expandable microcapsules to 70% by weight or less, foaming during the production of the master batch can be prevented, and as a result, the foaming ratio of the foam molded article can be improved. A preferred lower limit of the content of the heat-expandable microcapsules is 55% by weight, and a preferred upper limit is 60% by weight.

The shell constituting the heat-expandable microcapsules is made of a polymer obtained by polymerizing a monomer mixture containing a polymerizable monomer (I) comprising at least one selected from acrylonitrile, methacrylonitrile, and vinylidene chloride. Is preferred.
By adding the polymerizable monomer (I), the gas barrier property of the shell can be improved.

In order to further improve the heat resistance, the shell constituting the heat-expandable microcapsules has a polymerizable monomer (I) of 40 to 90% by weight, a carboxyl group, and a carbon number of 3 to 8; Of a radically polymerizable unsaturated carboxylic acid monomer (II) of 5 to 50% by weight.

A preferred lower limit of the content of the polymerizable monomer (I) in the monomer mixture is 40% by weight, and a preferred upper limit is 90% by weight. If the content of the polymerizable monomer (I) in the monomer mixture is less than 40% by weight, the gas barrier property of the shell is reduced, and the expansion ratio may be reduced. When the content of the polymerizable monomer (I) in the monomer mixture exceeds 90% by weight, heat resistance may not be improved. A more preferred lower limit of the content of the polymerizable monomer (I) in the monomer mixture is 50% by weight, and a more preferred upper limit is 80% by weight.

As the radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxyl group and having 3 to 8 carbon atoms, for example, a monomer having one or more free carboxyl groups per molecule for ionic crosslinking may be used. it can. Specific examples thereof include unsaturated monocarboxylic acids, unsaturated dicarboxylic acids and anhydrides thereof, and monoesters of unsaturated dicarboxylic acids and derivatives thereof.
Examples of the unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid. Examples of the unsaturated dicarboxylic acid include maleic acid, itaconic acid, fumaric acid, citraconic acid, chloromaleic acid and the like. Examples of the monoester of the unsaturated dicarboxylic acid include monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate. These may be used alone or in combination of two or more. Of these, acrylic acid, methacrylic acid, maleic acid, maleic anhydride and itaconic acid are particularly preferred.

A preferred lower limit of the content of the segment derived from the radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxyl group and having 3 to 8 carbon atoms in the monomer mixture is 5% by weight, and a preferred upper limit is 50% by weight. %. When the content of the segment derived from the radically polymerizable unsaturated carboxylic acid monomer (II) is less than 5% by weight, the maximum foaming temperature may be 190 ° C. or lower, and the radically polymerizable unsaturated carboxylic acid monomer When the content of the segment derived from (II) exceeds 50% by weight, the maximum foaming temperature is improved, but the foaming ratio is reduced. A more preferred lower limit of the content of the segment derived from the radically polymerizable unsaturated carboxylic acid monomer (II) is 10% by weight, and a more preferred upper limit is 40% by weight.

In the monomer mixture, the content of the polymerizable monomer (I) and the segment having the carboxyl group and derived from the radically polymerizable unsaturated carboxylic acid monomer (II) having 3 to 8 carbon atoms is described above. Although not particularly limited as long as it is within the range, it is preferable to use the following monomer mixtures (1) to (3).

The monomer mixture (1) comprises 40 to 90% by weight of the polymerizable monomer (I) and the radically polymerizable unsaturated carboxylic acid monomer (II) having 3 to 8 carbon atoms and having a carboxyl group. % By weight and does not contain the polymerizable monomer (III) having two or more double bonds in the molecule.

The monomer mixture (1) does not contain a polymerizable monomer (III) having two or more double bonds in a molecule in the monomer mixture. The polymerizable monomer (III) is generally used as a crosslinking agent.
In the monomer mixture (1), a shell having sufficient strength can be obtained by using a monomer mixture containing a predetermined amount of the polymerizable monomer (I) and the radical polymerizable unsaturated carboxylic acid monomer (II). Thereby, even when the polymerizable monomer (III) having two or more double bonds in the molecule is not contained in the monomer mixture, the heat-expandable microcapsules having excellent shear resistance, heat resistance, and foaming property can be obtained. can do. Although the reason for having sufficient strength as described above is not clear, it is considered that cross-linking between carboxyl groups by a dehydration condensation reaction is involved.
Further, when the polymerizable monomer (III) is added, the particle shape of the heat-expandable microcapsules becomes distorted, and as a result, the bulk specific gravity decreases. If the bulk specific gravity is reduced, in the next step, particularly when a masterbatch is manufactured using extrusion molding, the heat-expandable microcapsules tend to be sheared, so that the heat-expandable microcapsules tend to foam. . As a result, a stable masterbatch cannot be produced due to a decrease in the true specific gravity of the masterbatch or the like, and when foaming is subsequently performed by injection molding or the like, the foaming ratio tends to vary.

Thus, in the monomer mixture (1), heat-expandable microcapsules having sufficient strength and heat resistance are obtained without using the polymerizable monomer (III) having two or more double bonds in the molecule. It is possible. In addition, in this specification, "it does not contain the polymerizable monomer (III) which has two or more double bonds in a molecule | numerator in the said monomer mixture" does not contain the polymerizable monomer (III) substantially. In the case where the polymerizable monomer (III) is contained in a very small amount, it is considered that the polymerizable monomer (III) is not contained.

The polymerizable monomer (III) includes a monomer having two or more radical polymerizable double bonds. Specifically, for example, divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) A) acrylate and the like. Also, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate having a molecular weight of 200 to 600, glycerin di (meth) acrylate, trimethylol And propane di (meth) acrylate.
Further, trimethylolpropane tri (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, triallyl formal tri (meth) acrylate and the like can be mentioned.
In addition, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dimethylol-tricyclodecanedi (meth) acrylate and the like can be mentioned.

The monomer mixture (2) comprises 40 to 90% by weight of the polymerizable monomer (I) and the radically polymerizable unsaturated carboxylic acid monomer (II) having 3 to 8 carbon atoms and having a carboxyl group. % By weight, 0.2% by weight or less of the polymerizable monomer (III), and 0.1 to 10% by weight of the metal cation hydroxide (IV).

The monomer mixture (2) preferably contains a polymerizable monomer (III) having two or more double bonds in the molecule. The polymerizable monomer (III) has a role as a crosslinking agent.
By containing the polymerizable monomer (III), the strength of the shell can be enhanced, and the cell walls are less likely to break during thermal expansion.

The polymerizable monomer (III) is not particularly limited as long as it has a carboxyl group and is different from the radically polymerizable unsaturated carboxylic acid monomer (II) having 3 to 8 carbon atoms. Is preferably a monomer having two or more radical polymerizable double bonds. Specifically, for example, divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) A) acrylate and the like.
Also, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate having a molecular weight of 200 to 600, glycerin di (meth) acrylate, trimethylol And propane di (meth) acrylate.
Furthermore, trimethylolpropane tri (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dimethylol-tricyclodecanedi (meth) acrylate And the like.

The preferable upper limit of the content of the polymerizable monomer (III) in the monomer mixture (2) is 0.2% by weight. When the polymerizable monomer (III) is added in excess of 0.2% by weight, the particle shape of the heat-expandable microcapsules becomes distorted, and as a result, the bulk specific gravity decreases. If the bulk specific gravity is reduced, in the next step, particularly when a masterbatch is manufactured using extrusion molding, the heat-expandable microcapsules tend to be sheared, so that the heat-expandable microcapsules tend to foam. . As a result, a stable masterbatch cannot be produced due to a decrease in the true specific gravity of the masterbatch or the like, and when foaming is subsequently performed by injection molding or the like, the foaming ratio tends to vary. In the present invention, a decrease in the bulk specific gravity can be prevented by setting the content of the polymerizable monomer (III) to 0.2% by weight or less. A preferred lower limit of the content of the polymerizable monomer (III) is 0% by weight, and a more preferred upper limit is 0.1% by weight.

The monomer mixture (2) preferably contains a metal cation hydroxide (IV).
By containing the metal cation hydroxide (IV), ionic bonding occurs with the carboxyl group of the radically polymerizable unsaturated carboxylic acid monomer (II), thereby increasing rigidity and increasing heat resistance. It becomes possible. As a result, a heat-expandable microcapsule that does not burst or shrink for a long time in a high-temperature region can be obtained. In addition, since the elastic modulus of the shell is not easily reduced even in a high temperature region, even when performing a molding process such as kneading molding, calender molding, extrusion molding, or injection molding in which a strong shearing force is applied, the heat-expandable micro The capsule does not rupture or shrink.
Further, since the bonding is not a covalent bond but an ionic bond, the particle shape of the heat-expandable microcapsules becomes close to a true sphere, and distortion is unlikely to occur. This is because the crosslinking by ionic bonding has a weaker bonding force than the crosslinking by covalent bonding, so that when the monomer during polymerization is converted into a polymer, the heat-expandable microcapsules shrink uniformly when the volume shrinks. This is probably the cause.

The metal cation of the metal cation hydroxide (IV) is not particularly limited as long as it is a metal cation that reacts with the radically polymerizable unsaturated carboxylic acid monomer (II) to form an ionic bond. , Li, Zn, Mg, Ca, Ba, Sr, Mn, Al, Ti, Ru, Fe, Ni, Cu, Cs, Sn, Cr, Pb and the like. However, since the purpose is to form an ionic bond with the above-mentioned radically polymerizable unsaturated carboxylic acid monomer (II), it is necessary to be a hydroxide, and a chloride such as NaCl has a weak ionic bond and is not applicable here. Among these, ions of Ca, Zn, and Al, which are divalent or trivalent metal cations, are preferable, and ions of Zn are particularly preferable. These metal cation hydroxides (IV) may be used alone or in combination of two or more.

A preferred lower limit of the content of the metal cation hydroxide (IV) in the monomer mixture (2) is 0.1% by weight, and a preferred upper limit is 10% by weight. If the content of the metal cation hydroxide (IV) is less than 0.1% by weight, the effect on heat resistance may not be obtained, and the content of the metal cation hydroxide (IV) may be 10% by weight. %, The expansion ratio may be significantly deteriorated. A more preferred lower limit of the content of the metal cation hydroxide (IV) is 0.5% by weight, and a more preferred upper limit is 5% by weight.

The monomer mixture (3) comprises 40 to 90% by weight of the polymerizable monomer (I) and 5 to 50% by weight of a radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxyl group and having 3 to 8 carbon atoms. % And 0.1 to 10% by weight of the metal cation hydroxide (IV), and does not contain the polymerizable monomer (III) having two or more double bonds in the molecule.

The monomer mixture (3) does not contain a polymerizable monomer (III) having two or more double bonds in the molecule.
Crosslinking by ionic bonds between the radically polymerizable unsaturated carboxylic acid monomer (II) and the metal cation hydroxide (IV) causes polymerization in the monomer mixture having two or more double bonds in the molecule. Even if it does not contain the water-soluble monomer (III), the obtained shell has sufficient strength and heat resistance. When the polymerizable monomer (III) is added, the particle shape of the heat-expandable microcapsules becomes distorted, and as a result, the bulk specific gravity decreases. If the bulk specific gravity is reduced, in the next step, particularly when a masterbatch is manufactured using extrusion molding, the heat-expandable microcapsules tend to be sheared, so that the heat-expandable microcapsules tend to foam. . As a result, a stable masterbatch cannot be produced due to a decrease in the true specific gravity of the masterbatch or the like, and when foaming is subsequently performed by injection molding or the like, the foaming ratio tends to vary.

In the monomer mixture (3), the cross-linking due to ionic bonds is mainly performed, and the cross-linking due to covalent bonds is reduced, so that the polymerizable monomer (III) having two or more double bonds in the molecule can be used without sufficient strength. And heat-expandable microcapsules having heat resistance can be obtained. In addition, in this specification, "it does not contain the polymerizable monomer (III) which has two or more double bonds in a molecule | numerator in the said monomer mixture" does not contain the polymerizable monomer (III) substantially. In the case where the polymerizable monomer (III) is contained in a very small amount, it is considered that the polymerizable monomer (III) is not contained.

In addition to the polymerizable monomer (I) and the radical polymerizable unsaturated carboxylic acid monomer (II), other monomers may be added to the monomer mixture. Examples of the other monomers include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, acrylates such as dicyclopentenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobornyl methacrylate, and the like. Examples include methacrylic acid esters, vinyl monomers such as vinyl acetate and styrene. These other monomers can be appropriately selected and used according to the properties required for the heat-expandable microcapsules, and among them, methyl methacrylate, ethyl methacrylate, methyl acrylate, and the like are preferably used. The content of other monomers in all the monomers constituting the shell is preferably less than 10% by weight. When the content of the other monomer is 10% by weight or more, the gas barrier property of the cell wall is reduced, and the thermal expansion property is apt to be deteriorated.

In order to polymerize the monomer, a polymerization initiator is contained in the monomer mixture.
As the polymerization initiator, for example, dialkyl peroxide, diacyl peroxide, peroxyester, peroxydicarbonate, azo compound and the like are suitably used.
Examples of the dialkyl peroxide include methyl ethyl peroxide, di-t-butyl peroxide, isobutyl peroxide, dicumyl peroxide and the like.
Examples of the diacyl peroxide include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide and the like.
Examples of the peroxyester include t-butyl peroxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, 1-cyclohexyl-1-methyl Ethyl peroxy neodecanoate and the like can be mentioned.
Examples of the peroxydicarbonate include bis (4-t-butylcyclohexyl) peroxydicarbonate, di-n-propyl-oxydicarbonate, diisopropylperoxydicarbonate, di (2-ethylethylperoxy) dicarbonate, And dimethoxybutyl peroxydicarbonate.
Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile, and 2,2′-azobis (2,4-dimethylvalero). Nitrile), 1,1′-azobis (1-cyclohexanecarbonitrile) and the like.

A preferred lower limit of the weight average molecular weight of the polymer constituting the shell is 100,000, and a preferred upper limit is 2,000,000. If the weight average molecular weight is less than 100,000, the strength of the shell may decrease. If the weight average molecular weight exceeds 2,000,000, the strength of the shell may become too high and the expansion ratio may decrease.

The shell may further contain, if necessary, a stabilizer, an ultraviolet absorber, an antioxidant, an antistatic agent, a flame retardant, a silane coupling agent, a coloring agent, and the like.

In the heat-expandable microcapsules, a volatile expanding agent is encapsulated in the shell as a core agent.
The volatile swelling agent is a substance that becomes gaseous at a temperature equal to or lower than the softening point of the polymer constituting the shell, and is preferably a low-boiling organic solvent.
Examples of the volatile swelling agent include low molecular weight hydrocarbons, chlorofluorocarbons, tetraalkylsilanes, and the like.
Examples of the low molecular weight hydrocarbon include ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, isooctane, petroleum ether and the like.
As the _{chlorofluorocarbons, CCl 3 F, CCl 2 F} 2, CClF 3, CClF 2 -CClF 2 , and the like.
Examples of the tetraalkylsilane include tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane.
Of these, isobutane, n-butane, n-pentane, isopentane, n-hexane, isooctane, petroleum ether, and mixtures thereof are preferred. These volatile swelling agents may be used alone or in combination of two or more.
Further, as the volatile expanding agent, a thermally decomposable compound which is thermally decomposed by heating and becomes gaseous may be used.

In the thermally expandable microcapsules, among the volatile expanders described above, it is preferable to use a low-boiling hydrocarbon having 5 or less carbon atoms. By using such a hydrocarbon, it is possible to obtain a heat-expandable microcapsule which has a high expansion ratio and starts foaming promptly.
Further, as the volatile expanding agent, a thermally decomposable compound which is thermally decomposed by heating and becomes gaseous may be used.

In the masterbatch for foam molding of the present invention, the preferred lower limit of the content of the volatile expanding agent used as the core agent is 10% by weight, and the preferred upper limit is 25% by weight.
The thickness of the shell varies depending on the content of the core agent, but when the content of the core agent is reduced, the foaming performance is reduced when the shell is too thick, and when the content of the core agent is increased, the strength of the shell is reduced. I do. When the content of the above-mentioned core agent is 10 to 25% by weight, it is possible to achieve both prevention of sagging of the heat-expandable microcapsules and improvement of the foaming performance.

In the thermally expandable microcapsules, the lower limit of the maximum foaming temperature (Tmax) is preferably 180 ° C, and the upper limit is preferably 230 ° C. When the maximum foaming temperature is lower than 180 ° C., the heat resistance is lowered, so that the heat-expandable microcapsules burst or shrink in a high-temperature region or during molding. In addition, foaming occurs due to shearing during the production of the masterbatch, and an unfoamed masterbatch cannot be produced stably. A more preferred lower limit of the maximum foaming temperature is 210 ° C.
In the present specification, the maximum foaming temperature is defined as a value when the diameter of the heat-expandable microcapsule is maximized (maximum displacement) when the diameter of the heat-expandable microcapsule is measured while heating the same from room temperature. Means temperature.

In the thermally expandable microcapsules, a preferable lower limit of the maximum displacement (Dmax) measured by thermomechanical analysis is 300 μm, and a preferable upper limit is 1500 μm.
The maximum displacement is a value when the diameter of the predetermined amount of the thermally expandable microcapsules is maximized when the diameter of the thermally expandable microcapsules is measured while heating the predetermined amount of the thermally expandable microcapsules from normal temperature. .
The preferred upper limit of the foaming start temperature (Ts) is 160 ° C, and the preferred upper limit is 165 ° C.
In the present specification, the maximum foaming temperature means the temperature at which the thermally expandable microcapsule reaches the maximum displacement when its diameter is measured while heating the thermally expandable microcapsule from normal temperature.

The lower limit of the average particle diameter of the heat-expandable microcapsules is 15 μm, and the upper limit is 35 μm. When the average particle diameter is 15 μm or more, foaming of the obtained molded article becomes sufficient, and when the average particle diameter is 35 μm or less, the appearance of the obtained molded article becomes good and the strength of the molded article is reduced. It can be sufficient. The preferred lower limit of the average particle size is 18 μm, and the preferred upper limit is 30 μm.
The average particle size of the heat-expandable microcapsules means a volume average particle size measured using a particle size distribution analyzer.

A preferable lower limit of the bulk specific gravity of the heat-expandable microcapsules is 0.40 g / cm ³ . When the bulk specific gravity is less than 0.40 g / cm ³ , the heat-expandable microcapsules tend to be sheared, particularly when a masterbatch is produced by extrusion, so that the heat-expandable microcapsules tend to foam. Becomes As a result, a stable masterbatch cannot be produced due to a decrease in the true specific gravity of the masterbatch or the like, and when foaming is subsequently performed by injection molding or the like, the foaming ratio tends to vary. A preferred lower limit of the bulk specific gravity is 0.42 g / cm ³ .
The bulk specific gravity refers to a specific gravity based on the volume of the thermally expandable microcapsule aggregate that is most closely packed in a container or the like. The bulk specific gravity can be measured according to JIS K6721.

Examples of the method for producing the heat-expandable microcapsules include a step of preparing an aqueous medium, 40 to 90% by weight of the polymerizable monomer (I), a radical having a carboxyl group and having 3 to 8 carbon atoms. A step of dispersing an oily mixed solution containing 5 to 50% by weight of the polymerizable unsaturated carboxylic acid monomer (II) and a volatile expanding agent in an aqueous medium is performed. After that, a method of performing a step of polymerizing the above-mentioned monomer is exemplified.

When producing the above-mentioned heat-expandable microcapsules, a step of preparing an aqueous medium is first performed. Specifically, for example, an aqueous dispersion medium containing a dispersion stabilizer is prepared by adding water, a dispersion stabilizer, and, if necessary, an auxiliary stabilizer to a polymerization reaction vessel. If necessary, an alkali metal nitrite, stannous chloride, stannic chloride, potassium bichromate, or the like may be added.

Examples of the dispersion stabilizer include silica, calcium phosphate, magnesium hydroxide, aluminum hydroxide, ferric hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, calcium carbonate, barium carbonate, and carbonate. Magnesium and the like.

The amount of the dispersion stabilizer is not particularly limited, and is appropriately determined depending on the type of the dispersion stabilizer, the particle size of the heat-expandable microcapsules, and the like. Parts, a preferred upper limit is 20 parts by weight.

Examples of the co-stabilizer include a condensation product of diethanolamine and an aliphatic dicarboxylic acid, and a condensation product of urea and formaldehyde. Further, polyvinyl pyrrolidone, polyethylene oxide, polyethylene imine, tetramethylammonium hydroxide, gelatin, methyl cellulose, polyvinyl alcohol, dioctyl sulfosuccinate, sorbitan ester, various emulsifiers and the like can be mentioned.

The combination of the dispersion stabilizer and the auxiliary stabilizer is not particularly limited, for example, a combination of colloidal silica and a condensation product, a combination of colloidal silica and a water-soluble nitrogen-containing compound, magnesium hydroxide or calcium phosphate. Examples thereof include a combination with an emulsifier. Among these, a combination of colloidal silica and a condensation product is preferred.
Further, as the above condensation product, a condensation product of diethanolamine and an aliphatic dicarboxylic acid is preferable, and a condensation product of diethanolamine and adipic acid, and a condensation product of diethanolamine and itaconic acid are particularly preferable.

Examples of the water-soluble nitrogen-containing compound include polyvinyl pyrrolidone, polyethylene imine, polyoxyethylene alkylamine, polydialkylaminoalkyl (meth) acrylate, polydialkylaminoalkyl (meth) acrylamide, polyacrylamide, polycationic acrylamide, and polyamine sulfone. , Polyallylamine and the like.
Examples of the polydialkylaminoalkyl (meth) acrylate include polydimethylaminoethyl methacrylate and polydimethylaminoethyl acrylate.
Examples of the polydialkylaminoalkyl (meth) acrylamide include polydimethylaminopropyl acrylamide and polydimethylaminopropyl methacrylamide. Among these, polyvinylpyrrolidone is preferably used.

The amount of the colloidal silica to be added is appropriately determined depending on the particle size of the heat-expandable microcapsules, and a preferable lower limit is 1 part by weight and a preferable upper limit is 20 parts by weight based on 100 parts by weight of the vinyl monomer. A more preferred lower limit of the amount of colloidal silica added is 2 parts by weight, and a more preferred upper limit is 10 parts by weight. Further, the addition amount of the condensation product or the water-soluble nitrogen-containing compound is also appropriately determined depending on the particle diameter of the heat-expandable microcapsules. The upper limit is 2 parts by weight.

In addition to the dispersion stabilizer and the auxiliary stabilizer, inorganic salts such as sodium chloride and sodium sulfate may be further added. By adding the inorganic salt, heat-expandable microcapsules having a more uniform particle shape can be obtained. Usually, the amount of the inorganic salt is preferably from 0 to 100 parts by weight based on 100 parts by weight of the monomer.

The aqueous dispersion medium containing the dispersion stabilizer is prepared by blending the dispersion stabilizer and the auxiliary stabilizer in deionized water, and the pH of the aqueous phase at this time depends on the type of the dispersion stabilizer and the auxiliary stabilizer to be used. Is determined as appropriate. For example, when silica such as colloidal silica is used as a dispersion stabilizer, polymerization is carried out in an acidic medium. To make an aqueous medium acidic, an acid such as hydrochloric acid is added as necessary to adjust the pH of the system to 3 or more. ~ 4. On the other hand, when magnesium hydroxide or calcium phosphate is used, it is polymerized in an alkaline medium.

Next, in the method for producing the heat-expandable microcapsules, the polymerizable monomer (I) is contained in an amount of 40 to 90% by weight and a radically polymerizable unsaturated carboxylic acid monomer (II) having a carboxyl group and having 3 to 8 carbon atoms. A) a step of dispersing an oily mixed solution containing 5 to 50% by weight and a volatile expanding agent in an aqueous medium. In this step, the monomer and the volatile swelling agent may be separately added to the aqueous dispersion medium to prepare an oily mixture in the aqueous dispersion medium, but usually, both are mixed in advance to form an oily mixture. Is added to the aqueous dispersion medium. At this time, the oily mixture and the aqueous dispersion medium are prepared in advance in separate containers, and the oily mixture is dispersed in the aqueous dispersion medium by mixing with stirring in another container. It may be added.
In order to polymerize the monomer, a polymerization initiator is used. The polymerization initiator may be added to the oil-based mixed solution in advance, and the aqueous dispersion medium and the oil-based mixed solution are mixed in a polymerization reaction vessel. May be added after stirring.

Examples of the method of emulsifying and dispersing the above oily mixed solution in an aqueous dispersion medium at a predetermined particle size include a method of stirring with a homomixer (for example, manufactured by Tokushu Kika Kogyo Co., Ltd.), a line mixer and an element type static disperser. And the like.
The aqueous dispersion medium and the polymerizable mixture may be separately supplied to the stationary dispersion device, or a dispersion liquid that has been mixed and stirred in advance may be supplied.

The heat-expandable microcapsules can be manufactured by, for example, performing a step of polymerizing a monomer by heating the dispersion obtained through the above-described steps. The heat-expandable microcapsules produced by such a method have a high maximum foaming temperature, excellent heat resistance, and do not burst or shrink even in a high-temperature region or during molding. In addition, since the bulk specific gravity is high, foaming due to shearing during production of the masterbatch does not occur, and an unfoamed masterbatch can be produced stably.

The masterbatch for foam molding of the present invention may contain a chemical foaming agent. By including the chemical foaming agent, for example, when a chemical foaming agent such as sodium hydrogen carbonate is used, the foaming performance can be improved by CO ₂ generated when decomposed. In addition, by using the above-mentioned heat-expandable microcapsules and a chemical foaming agent in combination, it is possible to suppress the generation of open cells which tend to occur when the chemical foaming agent is used alone.

The chemical foaming agent is not particularly limited as long as it is in the form of a powder at normal temperature, and those conventionally used widely as chemical foaming agents can be used. Specifically, for example, an inorganic chemical blowing agent such as sodium hydrogencarbonate, or an organic compound such as azodicarbonamide, N, N'-dinitrosopentamethylenetetramine, P, P'-oxybisbenzenesulfonylhydrazide, or paratoluenesulfonylhydrazide. Chemical blowing agents.

The masterbatch for foam molding of the present invention may contain additives such as a lubricant. By containing the above lubricant, the share of the heat-expandable microcapsules during production of the masterbatch is suppressed, microfoaming and the like are less likely to occur, and the dispersibility of the heat-expandable microcapsules can be improved, It becomes easier to manufacture masterbatches. As a result, a masterbatch having a high concentration of thermally expandable microcapsules can be stably manufactured with good production efficiency.

The lubricant is not particularly limited as long as it dissolves at the temperature at the time of the production of the masterbatch, and those generally used as a lubricant can be used. Specific examples include polyethylene wax having a viscosity average molecular weight of 3,000 or less, fatty acid esters, fatty acids such as stearic acid, fatty acid derivatives, and so-called composite lubricants containing fatty acid amide as a main component.
Examples of the fatty acid ester include glycerin fatty acid esters such as glycerin monostearate and diglycerin stearate. Examples of the fatty acid derivative include a fatty acid to which a hydroxyl group is added.
Among them, a fatty acid derivative is preferable. Particularly, by using a fatty acid to which a hydroxyl group is added, it becomes possible to produce a masterbatch in which a high-viscosity base resin contains thermally expanded microcapsules at a high concentration.
Further, the fatty acid constituting the fatty acid ester, fatty acid or fatty acid derivative preferably has 15 to 40 carbon atoms, more preferably 18 to 36 carbon atoms, and still more preferably 18 to 20 carbon atoms.
In addition, the content of the lubricant in the masterbatch for foam molding of the present invention is preferably 1 to 15% by weight, and more preferably 5 to 12% by weight.

The shape of the masterbatch for foam molding of the present invention may be any of various shapes such as powder, granule, lump, strand, pellet, and sheet.

A preferable lower limit of the true specific gravity of the masterbatch for foam molding of the present invention is 0.80 g / cm ³ . When the true specific gravity is less than 0.80 g / cm ³ , it means that the heat-expandable microcapsules in the master batch are swollen, so that the foaming ratio of a molded product obtained after molding may be reduced. .
A more preferred lower limit of the true specific gravity is 0.90 g / cm ³ , and a preferred upper limit is 1.0 g / cm ³ .
The true specific gravity refers to the specific gravity of only the material excluding pores, and represents the ratio of the mass of a unit volume of the master batch at 20 ° C. to the equivalent mass of water at 4 ° C. The true specific gravity can be measured by a method based on JIS K 7112 A method (underwater replacement method).

A preferred lower limit of the bulk density of the foam-forming masterbatch of the present invention is 0.35 g / cm ^3. If the bulk specific gravity is less than 0.35 g / cm ³ , especially in the case of injection molding, the volume of the master batch is measured with a constant volume. In some cases, the expansion ratio of the molded article may be reduced.
A more preferred lower limit of the bulk specific gravity is 0.38 g / cm ³ , and a preferred upper limit is 0.50 g / cm ³ .
The bulk specific gravity refers to a specific gravity based on the volume of a master batch aggregate that is most closely packed in a container or the like.
The bulk specific gravity can be measured according to JIS K6721.

When the masterbatch for foam molding of the present invention is in the form of granules or pellets, the preferable lower limit of the particle size is 450 mg / 30. If the particle size is less than 450 mg / 30 particles, the particle size is small, so the surface area increases, and the base resin dissolves earlier in the molding machine due to temperature, shearing, etc., and the heat-expandable microcapsules foam earlier in the cylinder. In some cases, the effect of increasing the melting point of the base resin in the master batch may be reduced.
A more preferred lower limit of the particle size is 470 mg / 30, and a preferred upper limit is 600 mg / 30.
The particle size is a measure of the size of the master batch, and is represented by the total weight of 30 master batches.
The particle size can be measured by randomly collecting 30 master batches and measuring the weight.

The method of producing the masterbatch for foam molding of the present invention is not particularly limited. For example, a raw material such as a base resin containing an olefin-based elastomer, various additives such as a lubricant, and a coaxial twin-screw extruder are used. And knead in advance. Next, after heating to a predetermined temperature and adding a foaming agent composed of thermally expanded microcapsules, the kneaded material obtained by further kneading is cut into a desired size with a pelletizer to form a pellet into a masterbatch. And the like. If fine foaming is performed at this point, it is difficult to obtain a desired expansion ratio in the subsequent foam molding, and the variation becomes large.
Also, a method of kneading raw materials such as a base resin, a heat-expandable microcapsule, and a lubricant with a batch-type kneader, and then granulating with a granulator, or a method of manufacturing a pellet-shaped masterbatch with an extruder and a pelletizer. May be used.

The kneading machine is not particularly limited as long as it can knead without breaking the thermally expandable microcapsules, and examples thereof include a pressure kneader and a Banbury mixer.

A resin composition obtained by adding a matrix resin such as a thermoplastic resin to the masterbatch for foam molding of the present invention is molded using a molding method such as injection molding, and foamed by the heat-expandable microcapsules by heating during molding. By doing so, a foam molded article can be manufactured. Such a foam molded article is also one of the present invention.
The foam molded article of the present invention obtained by such a method has a high expansion ratio and high appearance quality, uniform closed cells are formed, and is excellent in lightness, heat insulation, impact resistance, rigidity and the like. It can be suitably used for applications such as building materials for houses, members for automobiles, shoe soles, and the like.

The matrix resin such as the thermoplastic resin is not particularly limited as long as the object of the present invention is not impaired.For example, a general thermoplastic resin such as polyvinyl chloride, polystyrene, polypropylene, polypropylene oxide, and polyethylene is used. . Further, engineering plastics such as polybutylene terephthalate, nylon, polycarbonate, polyethylene terephthalate and the like can be mentioned. In addition, thermoplastic elastomers such as ethylene-based, vinyl chloride-based, olefin-based, urethane-based, and ester-based resins may be used, or these resins may be used in combination. Further, as the matrix resin, it is preferable to use a resin similar to the base resin.

The amount of the masterbatch for foam molding of the present invention to be added to 100 parts by weight of the thermoplastic resin is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight.

The method for molding the foam molded article of the present invention is not particularly limited, and examples thereof include kneading molding, calender molding, extrusion molding, and injection molding. In the case of injection molding, the method of construction is not particularly limited, and a short-short method in which a resin material is partially filled in a mold and foaming, or a core-back method in which the mold is fully foamed after fully filling the resin material with the mold. And the like.

Another aspect of the present invention is a foaming masterbatch having a foaming rate of 15% or less after 3 minutes when heated to 180 ° C. and 25% or less after 5 minutes.
The foaming rate after 3 minutes is preferably 12% or less. The foaming rate after 5 minutes is preferably 24% or less.

The foaming ratio after 3 minutes is a ratio of “foaming height after 3 minutes” to “foaming height after 30 minutes” when 0.2 g of the foaming master batch is heated at 180 ° C. for 30 minutes. Say.
Further, the foaming ratio after 5 minutes refers to a ratio of “foaming height after 5 minutes” to “foaming height after 30 minutes” when the masterbatch for foam molding is heated at 180 ° C. for 30 minutes. .

Examples of uses of the molded products obtained by the method of the present invention and another embodiment of the foamed molded article of the present invention include, for example, automobile interior materials such as door trims and instrument panels (instrument panels) and automobile exterior materials such as bumpers. Is mentioned. In addition, it can be used for building materials such as wood flour plastics, shoe soles, artificial corks and the like.

ADVANTAGE OF THE INVENTION According to this invention, it can use suitably also in the shaping | molding with which a strong shearing force is applied, and the shaping | molding which requires a low shaping | molding temperature, foaming ratio is high, foaming speed is suppressed, and foaming with favorable appearance quality is achieved. A masterbatch for foam molding capable of obtaining a molded article can be provided. Further, by achieving the suppression of the foaming speed, it becomes possible to prevent the coalescence of the masterbatches for foam molding and the coalescence of the heat-expandable microcapsules in the molding machine. Furthermore, a foam molded article using the masterbatch for foam molding can be provided.

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

(Production of heat-expandable microcapsules)
In a polymerization reaction vessel, 300 parts by weight of water, 89 parts by weight of sodium chloride as a regulator, 0.07 parts by weight of sodium nitrite as a water-soluble polymerization inhibitor, and 8 parts by weight of colloidal silica (manufactured by Asahi Denka Co., Ltd.) as a dispersion stabilizer And 0.3 parts by weight of polyvinylpyrrolidone (manufactured by BASF) were added to prepare an aqueous dispersion medium. Next, an oily mixed solution comprising the metal salt, the monomer, the volatile swelling agent, and the polymerization initiator in the amounts shown in Table 1 was added to the aqueous dispersion medium and mixed to prepare a dispersion. The total dispersion is 15 kg. The resulting dispersion is stirred and mixed with a homogenizer, charged into a nitrogen-substituted pressure polymerization reactor (20 L), pressurized (0.2 MPa), and reacted at 60 ° C. for 20 hours to prepare a reaction product. did. The obtained reaction product was repeatedly dehydrated and washed with a centrifuge, and then dried to obtain heat-expandable microcapsules (Nos. 1 to 6).
In Table 1, the polymerizable monomer (I) was defined as the monomer (I), the radically polymerizable unsaturated carboxylic acid monomer (II) was defined as the monomer (II), and the polymerizable monomer (III) was defined as the monomer (III).

(Examples 1 to 9, Comparative Examples 1 to 9)
(Preparation of master batch pellets)
100 parts by weight of the base resin shown in Table 2 and a lubricant of the kind and blending amount shown in Table 2 were kneaded with a Banbury mixer. When the temperature reached about 100 ° C., the obtained thermally expandable microcapsules are shown in Table 2. The mixture was added in a blending amount, and the mixture was further kneaded for 30 seconds, extruded, and simultaneously pelletized to obtain a master batch pellet. In Table 2, EMMA represents an ethylene-methyl methacrylate copolymer, LDPE represents low-density polyethylene, and TPO represents an olefin-based elastomer.
The following resin was used.
[EMMA (1)] Ethylene-methacrylate copolymer: melt flow rate 20 g / 10 min, melting point 79 ° C., MMA content 25% by weight (Sumitomo Chemical Co., Ltd., Aklift WK402)
[EMMA (2)] ethylene-methacrylate copolymer: melt flow rate 7 g / 10 min, melting point 80 ° C., MMA content 25% by weight (Sumitomo Chemical Co., Ltd., Aklift WK307)
[EMMA (3)] Ethylene-methacrylate copolymer: melt flow rate 450 g / 10 min, melting point 67 ° C., MMA content 28% by weight (Aclift CM5021, manufactured by Sumitomo Chemical Co., Ltd.)
[LDPE (1)] Low-density polyethylene resin: melt flow rate 45 g / 10 min, melting point 108 ° C. (Torosoh, Petrocene 209)
[LDPE (2)] Low-density polyethylene resin: melt flow rate 7.6 g / 10 min, melting point 120 ° C. (Tosoh Corporation, Petrocene 1384R)
[TPO] Propylene-based elastomer: Melt flow rate 3.6 g / 10 min, melting point 80 ° C., ethylene content 11% by weight (Vistamax 3000 manufactured by Exon Mobil)

(Manufacture of foam moldings)
3 parts by weight of the obtained masterbatch pellets and 100 parts by weight of an olefin-based elastomer (Milastomer 7030BS manufactured by Mitsui Chemicals, Inc.) are mixed, and the obtained mixed pellets are supplied to a hopper of an extruder, melt-kneaded, and extruded. Molding was performed to obtain a plate-shaped foam molded article. Extrusion conditions were a mold temperature: 190 ° C.

(Evaluation)
The following performances were evaluated for the heat-expandable microcapsules (Nos. 1 to 6) and the molded articles obtained in Examples 1 to 9 and Comparative Examples 1 to 9. The results are shown in Tables 1 and 2.

(1) Evaluation of heat-expandable microcapsules (1-1) Volume average particle diameter The volume average particle diameter was measured using a particle size distribution analyzer (LA-910, manufactured by HORIBA).

(1-2) Foaming start temperature, maximum foaming temperature, maximum displacement Using a thermomechanical analyzer (TMA) (TMA2940, manufactured by TA instruments), foaming start temperature (Ts), maximum displacement (Dmax), and maximum foaming The temperature (Tmax) was measured. Specifically, 25 μg of a sample is placed in an aluminum container having a diameter of 7 mm and a depth of 1 mm, and heated from 80 ° C. to 220 ° C. at a rate of 5 ° C./min while applying a force of 0.1 N from above. Then, the displacement of the measuring terminal in the vertical direction was measured, the temperature at which the displacement began to rise was defined as the foaming start temperature, the maximum value of the displacement was defined as the maximum displacement, and the temperature at the maximum displacement was defined as the maximum foaming temperature.

(2) Evaluation of master batch pellets (2-1) Measurement of foaming rate (foaming rate after 3 minutes, foaming rate after 5 minutes) Regarding the masterbatch for foam molding, 0 was added to a test tube (φ16 mm, length 100 mm). Then, while heating at 180 ° C. using an ESPEC oven, the foaming height was measured after 3 minutes, 5 minutes, and 30 minutes.
Then, the ratio (%) of the “foaming height after 3 minutes” to the “foaming height after 30 minutes” was calculated and defined as “foaming rate after 3 minutes”. Similarly, the ratio (%) of the “foaming height after 5 minutes” to the “foaming height after 30 minutes” was calculated and defined as “foaming ratio after 5 minutes”.

(2-2) Measurement of True Specific Gravity The true specific gravity of the master batch pellet was measured using a hydrometer MD-200S (manufactured by Mirage Co., Ltd.) by a method based on the JIS K 7112 A method (underwater replacement method).

(2-3) Measurement of bulk specific gravity It was measured by a method based on JIS K6721.

(2-4) Measurement of Particle Size Thirty pieces were randomly sampled from the obtained master batch pellets, and the total weight was measured.

(3) Evaluation of molded article (3-1) The density, density before expansion, and density of the obtained molded article (after foaming) were determined by a method based on the JIS K 7112 A method (water substitution method). It was measured.
The expansion ratio was calculated from the density of the molded body before and after foaming.

(3-2) Surface roughness The surface roughness (Rz) of the surface of the molded product was measured with a 3D shape measuring instrument (manufactured by Keyence Corporation). As a criterion, ○ was given when the measured Rz value was less than 50 μm, Δ was given when 50 μm ≦ Rz value ≦ 100 μm, and × was given when more than 100 μm.

ADVANTAGE OF THE INVENTION According to this invention, it can use suitably also in the shaping | molding with which a strong shearing force is applied, and the shaping | molding which requires a low shaping | molding temperature, foaming ratio is high, foaming speed is suppressed, and foaming with favorable appearance quality is achieved. A masterbatch for foam molding capable of obtaining a molded article can be provided. Further, a foam molded article using the masterbatch for foam molding can be provided.

Claims (10)

A base resin, a masterbatch for foam molding containing heat-expandable microcapsules,
The base resin contains a resin having a melt flow rate of 0.1 to 60 g / 10 minutes and a melting point of 70 to 110 ° C,
The heat-expandable microcapsules have an average particle size of 15 to 35 μm,
A masterbatch for foam molding, wherein the content of the thermally expandable microcapsules is 52 to 70% by weight. The masterbatch for foam molding according to claim 1, wherein the base resin contains at least one selected from the group consisting of an acrylic resin, a polyethylene resin, and an olefin elastomer. The heat-expandable microcapsules contain a volatile expanding agent as a core agent in a shell made of a polymer,
2. The shell according to claim 1, wherein the shell is made of a polymer obtained by polymerizing a monomer mixture containing at least one polymerizable monomer (I) selected from acrylonitrile, methacrylonitrile and vinylidene chloride. 3. 2. The masterbatch for foam molding according to 2. The shell has a polymerizable monomer (I) composed of at least one selected from acrylonitrile, methacrylonitrile and vinylidene chloride in an amount of 40 to 90% by weight, a carboxyl group, and a radical polymerizable monomer having 3 to 8 carbon atoms. The masterbatch for foam molding according to claim 1, comprising a polymer obtained by polymerizing a monomer mixture containing 5 to 50% by weight of an unsaturated carboxylic acid monomer (II). The monomer mixture contains 40 to 90% by weight of a polymerizable monomer (I) composed of at least one selected from acrylonitrile, methacrylonitrile and vinylidene chloride, a carboxyl group, and a radical polymerizable monomer having 3 to 8 carbon atoms. 3. A polymerizable monomer (II) containing 5 to 50% by weight of an unsaturated carboxylic acid monomer (II) and containing no polymerizable monomer (III) having two or more double bonds in a molecule. 5. The masterbatch for foam molding according to 3 or 4. The monomer mixture contains 40 to 90% by weight of a polymerizable monomer (I) composed of at least one selected from acrylonitrile, methacrylonitrile and vinylidene chloride, a carboxyl group, and a radical polymerizable monomer having 3 to 8 carbon atoms. 5 to 50% by weight of an unsaturated carboxylic acid monomer (II) and 0.2% by weight or less of a polymerizable monomer (III) having two or more double bonds in a molecule, and / or a metal cation hydroxide (IV) 5. The masterbatch for foam molding according to claim 1, wherein the masterbatch contains 0.1 to 10% by weight. The monomer mixture is a polymerizable monomer (I) composed of at least one selected from acrylonitrile, methacrylonitrile and vinylidene chloride in an amount of 40 to 90% by weight, a carboxyl group, and a radical polymerizable monomer having 3 to 8 carbon atoms. A polymerizable polymer containing 5 to 50% by weight of an unsaturated carboxylic acid monomer (II) and 0.1 to 10% by weight of a metal cation hydroxide (IV) and having two or more double bonds in a molecule. The masterbatch for foam molding according to claim 1, 2, 3 or 4, wherein the masterbatch contains no monomer (III). The masterbatch for foam molding according to claim 1, 2, 3, 4, 5, 6, or 7, wherein the heat-expandable microcapsules have a maximum foaming temperature of 180 ° C or higher. A masterbatch for foam molding, wherein the foaming ratio after 3 minutes when heated to 180 ° C. is 15% or less, and the foaming ratio after 5 minutes is 25% or less. A foam molded article, characterized by using the masterbatch for foam molding according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9.