JP2008266478A - Carbon black-containing polypropylene resin foamed particles, and in-mold foam molding comprising the carbon black-containing polypropylene resin foamed particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide carbon black-containing polypropylene resin foamed particles having improved flame retardancy, and to provide a molding comprising the carbon black-containing polypropylene resin foamed particles. <P>SOLUTION: The carbon black-containing polypropylene resin foamed particles are obtained by dispersing carbon black-containing polypropylene resin particles obtained by melt-kneading a polyolefin resin containing carbon black in an amount of more than 40 wt.% and 60 wt.% or less and a polypropylene resin into a dispersion medium together with a foaming agent in an airtight container and releasing the carbon black-containing polypropylene resin particles to a low-pressure atmosphere from the airtight container at the softening temperature of the carbon black-containing polypropylene resin particles or higher together with the dispersion medium. Also disclosed is an in-mold foam molding obtained by mutually fusing the carbon black-containing polypropylene resin foamed particles. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carbon black-containing polypropylene resin expanded particle having improved flame retardancy, and a flame-retardant polypropylene resin expanded particle molded body obtained by fusing the carbon black-containing polypropylene resin expanded particle to each other. is there.

  In-mold foam moldings obtained by filling polypropylene resin foam particles with expanded polypropylene resin particles into a mold for in-mold foam molding and then heat-sealing them are already used as packaging materials, cushioning It is used in a wide range of applications such as wood, heat insulation, building materials, and automotive parts.

  Among these uses, in the field of building materials and automobile parts, it is required to have flame retardancy, and a polypropylene system containing a flame retardant and a flame retardant aid in the resin as necessary. In-mold foam moldings using resin foam particles and polypropylene resin foam particles have been proposed (for example, Patent Documents 1 and 2).

  In addition, there are cases where polypropylene resin foam particles colored from the viewpoint of appearance and in-mold foam moldings using the polypropylene resin foam particles are required, and in particular in the field of automobile parts, blackened polypropylene resin foam Since particles and in-mold foam moldings are required, polypropylene resin foam particles blackened with carbon black and in-mold foam moldings have been proposed (for example, Patent Document 3). In this literature, when blackening polypropylene resin foamed particles using carbon black, a polyolefin resin (masterbatch resin) containing 1 to 40% by weight of carbon black is used as a base resin. Melting and kneading with a polypropylene resin is disclosed.

Furthermore, a polypropylene-based resin foam particle and an in-mold foam molded body having both the above flame retardancy and blackness due to carbon black have also been proposed (for example, Patent Document 4).
JP-A-7-309967 JP-A-10-147661 JP-A-7-300537 JP 2004-263033 A

  Although the flame retardant level required for the in-mold foam molded product varies depending on the application, if the required flame retardant properties cannot be obtained with only the resin, generally, the resin contains a flame retardant or flame retardant aid, Has been given flame retardancy. As such flame retardants, halogen-based, phosphorus-based, nitrogen-based compounds, metal hydroxides, and the like are used, and as flame retardant aids, metal oxides, metal hydroxides, and the like are used. However, the polypropylene resin-in-mold foam-molded article containing these flame retardants and flame retardant aids has problems such as a decrease in mechanical strength and contamination of the mold caused by bleeding from the resin. Halogen-based flame retardants and phosphorus-based flame retardants are said to have environmental compatibility problems, and it is preferable that these flame retardants and flame retardant aids can be used to exhibit flame retardant properties. If impossible, it is preferable to reduce the amount of flame retardant and flame retardant auxiliary added as much as possible.

  On the other hand, when carbon black is used to blacken polypropylene resin foam particles and in-mold foam moldings, the carbon black reduces the flame retardancy, so it is much more difficult than when carbon black is not added. A flame retardant and a flame retardant aid will be required, and problems such as a decrease in mechanical strength will become apparent.

  The present invention has been made in view of these points, and the expanded polypropylene resin particles having excellent flame retardancy despite the addition of carbon black, and the expanded polypropylene resin particles. An object of the present invention is to provide a polypropylene resin foamed particle molded body that is fused to the resin.

  As a result of intensive studies for solving the above problems, the inventors of the present invention produced polypropylene resin particles as foamed particles using a polyolefin resin containing carbon black in an amount exceeding 40% by weight. In other words, by changing the method of adding carbon black to polypropylene resin by preparing a master batch with a high carbon black concentration and adding it to polypropylene resin, the obtained carbon black-containing polypropylene resin expanded particles are fused to each other. Conventionally known flame retardant properties of in-mold foam molded products are fused with polypropylene resin foam particles obtained in the same manner using a polyolefin resin containing, for example, 40% by weight or less of carbon black. We found unexpectedly improved flame retardancy compared to the in-mold foam molded product.Furthermore, it has been found that the problem of color unevenness which is generally a concern in colored particles can be solved by containing a silicate compound or a metal borate.

  That is, in the first aspect of the present invention, carbon black-containing polypropylene resin particles obtained by melt-kneading a polyolefin resin containing more than 40 wt% and not more than 60 wt% of carbon black and a polypropylene resin are contained in a sealed container. Disperse the carbon black-containing polypropylene resin particles in the dispersion medium together with the foaming agent at a temperature lower than the softening temperature of the carbon black-containing polypropylene resin particles and the carbon black-containing polypropylene resin particles together with the dispersion medium. It is related with the carbon black containing polypropylene resin expanded particle obtained by discharge | releasing in the atmosphere of this.

As a preferred embodiment,
(1) Carbon black content is 0.01 wt% or more and 10 wt% or less,
(2) 0.01 parts by weight or more and 3 parts by weight or less of a silicate compound with respect to 100 parts by weight of the carbon black-containing polypropylene resin particles,
(3) The boric acid metal salt is included in an amount of 0.01 parts by weight to 3 parts by weight with respect to 100 parts by weight of the carbon black-containing polypropylene resin particles.
It relates to the carbon black-containing polypropylene resin expanded particles described above.

  The second of the present invention relates to an in-mold foam-molded article comprising the carbon black-containing polypropylene-based resin foam particles described above.

  The in-mold foam molded article comprising the carbon black-containing polypropylene resin expanded particles of the present invention has a remarkable improvement in flame retardancy as compared with the in-mold foam molded article having the same carbon black concentration in the FMVSS302 combustion test method. There is no uneven color.

  The polypropylene resin used in the present invention is a resin comprising propylene as a monomer component, preferably 60% by weight or more, more preferably 80% by weight or more, and a monomer copolymerizable with propylene. It may be included. Specifically, polypropylene, ethylene-propylene block copolymer, ethylene-propylene random copolymer, butene-propylene random copolymer, butene-propylene block copolymer, ethylene-butene-propylene random copolymer, etc. Can be mentioned. Among these, an ethylene-propylene random copolymer, a butene-propylene random copolymer, and an ethylene-butene-propylene random copolymer are particularly preferable. Among them, ethylene-propylene random copolymer having an ethylene content of 0.1 wt% or more and 10 wt% or less, or a total of 0.1 wt% or more and 10 wt% or less of ethylene and 1-butene, An ethylene-butene-propylene random copolymer containing 1-butene in an amount of 0.5% by weight or more is more preferable from the viewpoints of moldability and mechanical strength.

  These polypropylene resins may be non-cross-linked or cross-linked, but are preferably non-cross-linked from the viewpoint of recycling.

  In the present invention, a carbon black-containing polypropylene is prepared by melt-kneading a polyolefin-based resin (hereinafter sometimes referred to as a master batch resin) containing more than 40% by weight and not more than 60% by weight of carbon black and the polypropylene-based resin. System resin particles are obtained.

  Although there is no restriction | limiting in the preparation method of the said masterbatch resin, it mixes with polyolefin resin so that carbon black concentration may be more than 40 weight% and 60 weight% or less, and this is a pressure kneader, a Banbury mixer, single screw extrusion. It can be produced by sufficiently kneading with a machine, a twin screw extruder or the like. Carbon black and polyolefin resin may be mixed in advance and homogenized with a mixer or the like. When using an extruder or the like, the polyolefin resin is introduced from the hopper upstream of the extruder. The carbon black can also be mixed by feeding it halfway (side feed).

  Examples of the polyolefin resin that can be used in the present invention include the above-mentioned polypropylene resins, polyethylene resins such as low density polyethylene, linear low density polyethylene, high density polyethylene, and ethylene-vinyl acetate copolymer. It is done.

  The carbon black content in the masterbatch resin in the present invention is very important from the viewpoint of flame retardancy. That is, in order to improve flame retardancy, a content exceeding 40% by weight is required. By setting the carbon black content in the masterbatch resin to a concentration exceeding 40% by weight, the dispersion state of the carbon black in the carbon black-containing polypropylene resin foam particles finally obtained is affected. It is estimated that it contributes to the improvement of the flame retardance of a molded object.

  When the carbon black content in the masterbatch resin is 40% by weight or less, the flame retardancy of the in-mold foam molded article obtained from the polypropylene resin foamed particles is lowered.

  On the other hand, when it exceeds 60% by weight, uneven color of the in-mold foam molded product obtained from the polypropylene resin expanded particles cannot be suppressed. From the viewpoint of exhibiting flame retardancy and suppressing color unevenness, it is preferably 42 wt% or more and 50 wt% or less, more preferably 43 wt% or more and 48 wt% or less.

  Next, the carbon black-containing polypropylene resin is melt-kneaded with a predetermined amount of masterbatch resin and a predetermined amount of polypropylene resin so that the carbon black content in the carbon black-containing polypropylene resin particles becomes a desired amount. Resin particles are used. For example, a predetermined amount of masterbatch resin and a predetermined amount of polypropylene resin are melt-kneaded with an extruder or the like, extruded into a strand through a die, cooled in a water tank, granulated with a pelletizer, and then a carbon black-containing polypropylene resin Make particles. Or resin melt-kneaded with an extruder etc. is extruded through a die | dye, and it cuts with the knife rotated in water, making contact with the die surface of the extrusion side, and produces. If necessary, before supplying the master batch resin and a predetermined amount of polypropylene resin to the extruder, they may be mixed by a generally used high-speed mixer, Henschel mixer, tumbler or the like.

  The weight of the carbon black-containing polypropylene resin particles granulated at this time is not particularly limited, but from the viewpoint of moldability when the carbon black-containing polypropylene resin foam particles are subjected to in-mold foam molding, 0.1 to 5 mg / Granules are preferred, more preferably 0.5 to 2.5 mg / grain, most preferably 0.8 to 2.2 mg / grain. Further, the ratio L / D between the length L and the diameter D of the resin particles is not particularly limited, but is preferably 0.5 to 5 and more preferably 0.7 to 4.5 from the viewpoint of moldability. And most preferably 0.8-4.

  The carbon black used in the present invention is not particularly limited, and ketjen black, thermal black, furnace black, channel black, lamp black, gas black, roller black, acetylene black and the like can be used.

  The particle size of carbon black used in the present invention is not particularly limited, but the particle size is preferably 0.1 to 10,000 nm. If it is less than 0.1 nm, it tends to be difficult to handle, and if it exceeds 10,000 nm, the dispersibility in the resin tends to be poor and color unevenness tends to be caused. Further, the size of the structure in which the particles are aggregated may be approximately several tens nm to several hundreds nm.

  When producing carbon black-containing polypropylene resin particles as described above, various types of carbon black dispersant, flame retardant, antistatic agent, antioxidant, light stabilizer, lubricant, etc. Additives can also be mixed in any proportion. In particular, when a silicate compound or a boric acid metal salt is added, the carbon black-containing polypropylene resin expanded particles finally obtained, or an in-mold expanded molded article obtained by fusing the polypropylene resin expanded particles to each other From the point that uneven color is suppressed, this is a preferred form in the present invention. This point will be described later.

  The flame retardant is not particularly limited, and known halogen flame retardants, phosphorus flame retardants, nitrogen flame retardants, metal hydroxides, metal oxides, and the like can be used.

Examples of halogen flame retardants include tetrabromoethane, tetrabromocyclooctane, hexabromocyclododecane, dibromoethyldibromocyclohexane, dibromodimethylhexane, 2- (bromomethyl) -2- (hydroxymethyl) -1,3-propanediol, and dibromo. Neopentyl glycol, tribromoneopentyl alcohol, pentaerythrityl tetrabromide, monobromodipentaerythritol, dibromodipentaerythritol, tribromodipentaerythritol, tetrabromodipentaerythritol, pentabromodipentaerythritol, hexabromodipentaerythritol, Brominated aliphatic compounds such as hexabromotripentaerythritol, polybrominated polypentaerythritol, or derivatives thereof, Rui bromine cycloaliphatic compounds or derivatives thereof;
Hexabromobenzene, pentabromotoluene, ethylenebispentabromodiphenyl, decabromodiphenyl ether, octabromodiphenyl ether, bis (2,4,6-tribromophenoxy) ethane, tetrabromophthalic anhydride, octabromotrimethylphenylindane, pentabromobenzyl Brominated aromatic compounds such as acrylate, tribromophenyl allyl ether, 2,3-dibromopropyl pentabromophenyl ether or derivatives thereof;

  Tetrabromobisphenol A, tetrabromobisphenol A diallyl ether, tetrabromobisphenol A dimethallyl ether, tetrabromobisphenol A diglycidyl ether, tribromophenol adduct of tetrabromobisphenol A diglycidyl ether, tetrabromobisphenol A bis (2, 3-dibromopropyl ether), tetrabromobisphenol A bis (2-bromoethyl ether), tetrabromobisphenol A bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol S bis (2,3-dibromo) Brominated bisphenols such as propyl ether) and tetrabromobisphenol S and derivatives thereof;

Brominated bisphenol derivatives oligomers such as tetrabromobisphenol A polycarbonate oligomers, tetrabromobisphenol A diglycidyl ether and brominated bisphenol adduct epoxy oligomers;
Brominated acrylic resins such as pentabromobenzyl acrylate polymer; ethylene bistetrabromophthalimide, ethylene bisdibromonorbornane dicarboximide, 2,4,6-tris (2,4,6-tribromophenoxy) 1,3,5- Bromine and nitrogen atom containing compounds such as triazine, tris (2,3-dibromopropyl) isocyanurate, (g) Bromine and phosphorus atom containing compounds such as tris (tribromoneopentyl) phosphate, tris (bromophenyl) phosphate;

  Examples include chlorine-containing compounds such as chlorinated paraffin, chlorinated naphthalene, perchloropentadecane, chlorinated aromatic compounds, and chlorinated alicyclic compounds; brominated inorganic compounds such as ammonium bromide.

  Examples of phosphorus flame retardants include phosphorous oxides such as red phosphorus, phosphorus trioxide, phosphorus tetroxide, and phosphorus pentoxide, phosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid, pyrophosphoric acid, polyphosphoric acid, and the like. Phosphate compounds, monoammonium phosphate, diammonium phosphate, ammonium phosphates such as ammonium polyphosphate (ammonium polyphosphate), melamine phosphates such as melamine monophosphate, melamine diphosphate, melamine polyphosphate, lithium phosphate, Phosphate salts such as metal phosphates such as sodium phosphate, potassium phosphate, calcium phosphate, magnesium phosphate;

  Aliphatic phosphate esters such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri (2-ethylhexyl) phosphate, tributoxyethyl phosphate, monoisodecyl phosphate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate Kind;

  Triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tris (isopropylphenyl) phosphate, tris (phenylphenyl) phosphate, trinaphthyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, diphenyl (2-ethylhexyl) phosphate , Aromatic phosphate esters such as di (isopropylphenyl) phenyl phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate; phosphate esters having two or more phosphate ester groups;

  Halogen-containing phosphate esters such as tris (tribromoneopentyl) phosphate; phosphazenes such as phosphazenes and polyphosphazenes, phosphate amines, phosphate amides, and the like.

  Examples of nitrogen-based flame retardants include triazine skeleton-containing compounds such as melamine, melam, melem, melon, and methylol melamine; cyanuric acid, methyl cyanurate, diethyl cyanurate, trimethyl cyanurate, triethyl cyanurate, isocyanuric acid, methyl isocyanurate, N, N′-diethylisocyanurate, trismethylisocyanurate, trisethylisocyanurate, bis (2-carboxyethyl) isocyanurate, 1,3,5-tris (2-carboxyethyl) isocyanurate, tris (2,3 -Cyanuric acid such as epoxypropyl) isocyanurate, tris (1,2-dihydroxyethyl) isocyanurate, 1,3,5-tris (2-hydroxyethyl) cyanurate, isocyanuric acid or derivatives thereof;

  Examples thereof include a salt composed of a triazine skeleton-containing compound such as melamine cyanurate and cyanuric acid or isocyanuric acid and derivatives thereof; a hindered amine compound, and the like.

  Next, a method for converting the carbon black-containing polypropylene resin particles into carbon black-containing polypropylene resin foam particles will be described, but the present invention is not particularly limited thereto.

  The carbon black-containing polypropylene resin particles obtained as described above are dispersed in a dispersion medium such as water while stirring and flowing the contents together with the foaming agent in a sealed pressure vessel, and more specifically, at a temperature higher than the softening temperature of the polypropylene resin. Is heated to the melting point of the polypropylene-based resin from −10 ° C. to the melting point + 10 ° C. and held at this temperature (foaming temperature) for a certain period of time. While maintaining the above pressure, the carbon black-containing polypropylene resin particles and the dispersion medium are simultaneously released in a low-pressure atmosphere (usually under atmospheric pressure) from inside the container to foam the carbon black-containing polypropylene resin particles, As a result, carbon black-containing polypropylene resin expanded particles can be obtained.

  The melting point of the resin is about 4 to 6 mg of sample heated to 220 ° C. at a rate of temperature increase of 10 ° C./min with a differential scanning calorimeter, and then cooled to about 50 ° C. at a rate of temperature decrease of 10 ° C./min. The temperature at the top of the endothermic peak (inherent peak) in the DSC curve obtained when the temperature is raised again to 220 ° C. at a rate of 10 ° C./min.

  Examples of foaming agents for foaming carbon black-containing polypropylene resin particles include aliphatic hydrocarbons such as butane, propane, pentane, hexane, heptane, cyclobutane, and cyclopentane, air, nitrogen, carbon dioxide, helium, and neon. Inorganic substances such as argon and water can be used, and two or more of these may be used in combination. In addition, when using water as a foaming agent, the water of the dispersion medium used when obtaining foamed particle can be utilized.

  The amount of the foaming agent used is appropriately adjusted in relation to the expansion ratio and expansion temperature of the expanded particles to be obtained. The pressure is 1.5 to 7 MPa (G) at the expansion temperature during or after heating. It is preferable to press-fit into the container so as to be in the range, or to charge in advance an amount that shows the pressure at the foaming temperature before heating.

  The dispersion medium for dispersing the carbon black-containing polypropylene resin particles may be any dispersion medium that does not dissolve the resin particles. Examples of such a dispersion medium include water, methanol, ethanol, ethylene glycol, glycerin, and the like. However, it is most preferable to use water.

  A dispersant can be used to prevent fusion of resin particles when carbon black-containing polypropylene resin particles are dispersed in a dispersion medium and heated to a foaming temperature. Examples of such a dispersant include calcium phosphate, aluminum oxide, titanium oxide, aluminum hydroxide, kaolin, talc, and mica. Although there is no restriction | limiting in particular in the average particle diameter of a dispersing agent, 0.001-50 micrometers is preferable, More preferably, it is 0.01-20 micrometers. When it is less than 0.001 μm, it may be difficult to handle, and when it exceeds 50 μm, the performance as a dispersant tends to decrease.

  The addition amount of the dispersant is appropriately adjusted to prevent the carbon black-containing polypropylene resin particles from fusing each other depending on the foaming temperature, the addition amount of the foaming agent, and the type of the foaming agent. 0.01-5 weight part is preferable with respect to 100 weight part of black containing polypropylene resin particles. If the amount is less than 0.01 part by weight, the performance as a dispersant may be reduced, and fusion between the carbon black-containing polypropylene resin particles may be observed. Absent.

  Examples of the dispersion aid include surfactants such as sodium alkylbenzene sulfonate, sodium alkyl sulfate, sodium n-paraffin sulfonate, sodium oleate, polyoxyethylene alkylphenyl ether, lauryltrimethylammonium chloride, and fatty acid diethanolamide. It is done.

  The amount of such a dispersion aid added is appropriately adjusted depending on the foaming temperature, the amount of foaming agent added, the type of foaming agent, the type of dispersant, and the amount added. 0.001-2 weight part is preferable with respect to 100 weight part of the resin particles. If the amount is less than 0.001 part by weight, the performance as a dispersion aid may be reduced and the resin particles may be fused. If the amount exceeds 2 parts by weight, no significant improvement in the anti-fusing performance is observed.

  The carbon black content in the carbon black-containing polypropylene resin expanded particles of the present invention is not particularly limited, and may be appropriately adjusted according to the desired blackness. It is preferable that it is 10 to 10 weight%. If it is less than 0.01% by weight, the degree of blackness may be thin, and if it exceeds 10% by weight, the moldability when obtaining a molded product may be reduced.

  In this invention, the aspect which contains 0.01 to 3 weight part of silicate compounds with respect to 100 weight part of carbon black containing polypropylene resin particles is a more preferable aspect. By adding a silicate compound, it is possible to refine the cell diameter of the foamed resin particles and uniformly adjust the foamed resin particles, and in the present invention using a masterbatch resin containing more than 40% by weight and less than 60% by weight of carbon black In addition, it is possible to obtain an in-mold foam-molded product in which beautiful carbon black-containing polypropylene resin expanded particles without color unevenness, and further, carbon black-containing polypropylene resin expanded particles are fused to each other. If the amount of the silicate compound is less than 0.01 parts by weight, the effect of reducing color unevenness may be small. If it exceeds 3 parts by weight, the bubble diameter becomes too small, and the moldability when obtaining an in-mold foam molded product is lowered. There is a case.

  Examples of silicate compounds include feldspar, zeolite, talc, kaolin and mica. These may be used alone or in combination of two or more. Among these, it is more preferable to use talc from the viewpoint of reducing color unevenness.

  In the present invention, an aspect including 0.01 to 3 parts by weight of a boric acid metal salt with respect to 100 parts by weight of the carbon black-containing polypropylene resin particles is another more preferable aspect. When metallic borate is added, beautiful carbon black-containing polypropylene resin expanded particles with no color unevenness, and in-mold expanded molded products in which carbon black-containing polypropylene resin expanded particles are fused together. However, it is considered to be different from the mechanism of color unevenness reduction by addition of a silicate compound. The mechanism is unknown at this stage, but when producing carbon black-containing polypropylene resin particles, there is also an effect of reducing color unevenness when carbon black and boric acid metal salt are melted and kneaded with the resin. It is presumed that some kind of interaction is exerted at the time of producing the color to reduce the color unevenness.

  Examples of the borate metal salt include zinc borate, magnesium borate, calcium borate, barium borate, aluminum borate, sodium borate and the like, and these can be used alone or in combination of two or more. Among these, it is more preferable to use zinc borate from the viewpoint of reducing color unevenness.

  If the addition amount of the metal borate is less than 0.01 parts by weight, the effect of reducing color unevenness may be small, and if it exceeds 3 parts by weight, the shrinkage of the carbon black-containing polypropylene resin expanded particles may increase.

  Although there is no restriction | limiting in particular in the production method of the carbon black containing polypropylene resin expanded particle of this invention, It can produce by the following well-known methods. That is, a carbon black-containing polypropylene obtained by melt-kneading a polyolefin resin (masterbatch resin) containing more than 40% by weight and not more than 60% by weight of carbon black, a polypropylene resin and various additives as required. The resin particles are dispersed in a dispersion medium together with a foaming agent in a closed container together with a dispersant and a dispersion aid as necessary, and the temperature of the closed container is increased, and the carbon black-containing polypropylene resin particles are carbonized. Although the temperature is equal to or higher than the softening temperature of the black-containing polypropylene resin particles, the foaming agent is press-fitted in at least one stage before, during, or after the temperature rise as necessary. Release the carbon black-containing polypropylene resin particles together with the dispersion medium at a temperature equal to or higher than the softening temperature of the carbon black-containing polypropylene resin particles into a low-pressure atmosphere (usually under atmospheric pressure) from the inside of the above-mentioned sealed container. Resin foam particles can be obtained.

  In addition, when releasing in a low-pressure atmosphere (usually under atmospheric pressure) from the inside of the above-mentioned sealed container, the pressure in the sealed container is maintained, for example, with an inorganic gas such as nitrogen, air, carbon dioxide, etc. so as not to decrease. It is preferable.

  The in-mold foam-molded article comprising the carbon black-containing polypropylene resin expanded particles of the present invention was selected from air, oxygen, nitrogen, carbon dioxide, or these as needed. The carbon black-containing polypropylene-based resin expanded particles are left as they are in a mold for molding that can be closed but cannot be sealed after applying a predetermined internal pressure within the particles by applying pressure aging with an inorganic gas that is a plurality of mixed gases. Alternatively, the molded product can be filled by pressurizing and compressing, heating the carbon black-containing polypropylene resin foamed particles with water vapor at a temperature near the melting point of the polypropylene resin, thereby fusing the particles together, and then cooling. It can be obtained by an in-mold molding method.

  The carbon black-containing polypropylene-based resin expanded particles of the present invention have little color unevenness, and the in-mold foam-molded product composed of the carbon black-containing polypropylene-based resin expanded particles has excellent flame retardancy and no color unevenness. Since it is lightweight and has little heat change, it can be used in a wide range of applications such as packaging materials, cushioning materials, heat insulating materials, building materials, and automotive parts.

  Next, the carbon black-containing polypropylene-based resin expanded particles of the present invention and the in-mold foam-molded article comprising the carbon black-containing polypropylene-based resin expanded particles will be described in more detail with reference to examples. “Parts” and “%” are based on weight unless otherwise specified.

  Evaluation of the carbon black-containing polypropylene-based resin expanded particles and the in-mold expanded molded article was performed as follows.

<Foaming ratio>
Ethanol is placed in a 200 ml graduated cylinder, and then the carbon black-containing polypropylene resin expanded particles whose weight is precisely weighed are added. The volume increment is read with a graduated cylinder, and the density of the carbon black-containing polypropylene resin expanded particles is calculated. The density of the carbon black-containing polypropylene resin particles was 0.9 g / ml, and the density of the carbon black-containing polypropylene resin particles was divided by the density of the carbon black-containing polypropylene resin foam particles to obtain the expansion ratio.

<Molded body density>
The vertical, horizontal, and thickness dimensions of the molded body were measured, and the density was calculated by measuring the weight.

<Flame retardance>
A test piece of 356 mm × 102 mm × 12 mm was cut out from the molded body, and a flammability test was performed according to FMVSS302. From one end side (a side) in the longitudinal direction of the test piece, 38 mm was set as an A mark line, 254 mm from the A mark line was set as a B mark line, and the other end side was held by a clamp or the like so as to be horizontal. The burner mouth is 19 mm below the lower surface of the test piece and the flame height is 38 mm. The flame is applied to one end side (a side) of the test piece for 15 seconds, and then the burner flame is turned off. When reached, time measurement was started with a stopwatch and evaluated according to the following criteria.
○: Extinguish fire before flame reaches A mark or within 50 seconds within 50 seconds after passing A mark (self-extinguishing)
Δ: A mark exceeding the A mark until reaching the B mark, or if the mark does not reach the B mark, the burning speed until exceeding the A mark and extinguishing is 100 mm / min or less. If it does not reach the B mark line, or if it does not reach the B mark line, the burning rate to exceed the A mark line and extinguish the fire exceeds 100 mm / min.

<Color unevenness>
The appearance of the compact was visually evaluated and evaluated according to the following criteria.
○: Almost no part with different color of the molded product Δ: Some parts with different color of the molded product are slightly seen ×: Many parts with different color of the molded product

(Reference example)
<Preparation of masterbatch resin>
Copolymer A (ethylene-propylene random copolymer: ethylene content 3.2%, MI = 6 g / 10 min) and carbon black (MCF88B manufactured by Mitsubishi Chemical Co., Ltd., average particle size 18 nm) were mixed at the ratio shown in Table 1. Then, it was sufficiently kneaded with a Banbury mixer to prepare a master batch resin.

<Production of carbon black-containing polypropylene resin particles>
Master batch resin and copolymer A or copolymer B (ethylene-butene-propylene random copolymer: ethylene content 1.2%, 1-butene content 4.8%, MI = 7 g / 10 min. ) Was mixed so that the composition ratio with respect to carbon black would be the amount shown in Table 1, and the resin additive was mixed with 100 parts by weight of the mixed resin so as to have the amount shown in Table 1. This mixture was put into an extruder with a diameter of 50 mm, melted and kneaded, discharged into a strand, cooled with water, and cut with a pelletizer to obtain carbon black-containing polypropylene resin particles. During cutting, the particle weight of the carbon black-containing polypropylene resin particles was adjusted to 1.2 mg / particle.

(Examples 1-6)
<Production of carbon black-containing polypropylene resin expanded particles>
100 parts by weight of carbon black-containing polypropylene resin particles prepared by the method described in Reference Example were charged into a 10-liter pressure vessel together with the dispersion medium, dispersant, and dispersion aid shown in Table 1, and then heated to a predetermined temperature. At this time, the foaming agent was charged so that the pressure shown in Table 1 was reached before heating until reaching the predetermined temperature, and after reaching the predetermined temperature as necessary. Thereafter, while maintaining the internal pressure of the container with nitrogen gas, the valve under the pressure container was opened to release the contents of the pressure container to the atmosphere, and carbon black-containing polypropylene resin expanded particles were obtained. Table 1 shows the expansion ratio of the obtained carbon black-containing polypropylene resin expanded particles.

<Production process of carbon black-containing polypropylene resin in-mold foam molding>
Next, the obtained carbon black-containing polypropylene resin expanded particles were charged into another pressure vessel, and air was injected to apply an internal pressure of 0.19 MPa to the carbon black-containing polypropylene resin expanded particles.

  The foamed carbon black-containing polypropylene resin particles to which an internal pressure was applied were filled in a 400 mm × 300 × 120 mm mold, heated with 0.3 MPa of water vapor for 10 seconds, and fused to obtain an in-mold foam molded article. Table 1 shows the characteristics of the obtained molded body.

(Examples 7 to 9)
In the same manner as in Examples 1 to 6, carbon black-containing polypropylene-based resin expanded particles having the contents described in Table 1 were obtained. Table 1 shows the expansion ratio of the obtained carbon black-containing polypropylene resin expanded particles. Then, in order to increase the expansion ratio of the carbon black-containing polypropylene-based resin expanded particles, the following two-stage expansion was performed.

  That is, the carbon black-containing polypropylene resin expanded particles are charged into another pressure vessel, air is injected to apply a predetermined amount of air pressure to the carbon black-containing polypropylene resin expanded particles, and then the pressure vessel is equipped with a stirring function. After the addition, water vapor of a predetermined pressure was blown in while stirring to obtain carbon black-containing polypropylene resin expanded particles having an expansion ratio larger than that of the original carbon black-containing polypropylene resin expanded particles. Table 1 shows the expansion ratio of the two-stage expanded carbon black-containing polypropylene resin expanded particles.

  Next, an internal pressure of 0.19 MPa was applied to the carbon black-containing polypropylene-based resin expanded particles expanded in two steps in the same manner as in Examples 1 to 6, and molded to obtain an in-mold expanded molded body. Table 1 shows the characteristics of the obtained molded body.

(Comparative Examples 1 and 2)
In the same manner as in Reference Examples and Examples 1 to 6, in-mold foam molded articles were obtained with the contents shown in Table 1. Table 1 shows the characteristics of the obtained in-mold foam molded article.

(Comparative Example 3)
A mold was prepared in the same manner as in Examples 1 to 6 except that carbon black masterbatch resin was not used, and carbon black was directly added to the polypropylene resin as described in Table 1 to produce carbon black-containing polypropylene resin particles. An inner foamed molded product was obtained. Table 1 shows the characteristics of the obtained in-mold foam molded article.

Claims (5)

  Carbon black-containing polypropylene resin particles obtained by melt-kneading a polyolefin resin containing more than 40% by weight and less than 60% by weight of carbon black with a polypropylene resin are used as a dispersion medium together with a foaming agent in a closed container. Obtained by dispersing and releasing the carbon black-containing polypropylene resin particles together with the dispersion medium at a temperature equal to or higher than the softening temperature of the carbon black-containing polypropylene resin particles and releasing the carbon black-containing polypropylene resin particles in a low-pressure atmosphere from the inside of the closed container. Carbon black-containing polypropylene-based resin expanded particles.   The carbon black-containing polypropylene resin expanded particles according to claim 1, wherein the carbon black content is 0.01 wt% or more and 10 wt% or less.   The carbon black-containing polypropylene resin expanded particles according to claim 1 or 2, comprising 0.01 parts by weight or more and 3 parts by weight or less of a silicate compound with respect to 100 parts by weight of the carbon black-containing polypropylene resin particles.   The carbon black-containing polypropylene resin foamed particles according to claim 1 or 2, comprising 0.01 parts by weight or more and 3 parts by weight or less of a metal borate with respect to 100 parts by weight of the carbon black-containing polypropylene resin particles.   An in-mold foam-molded article comprising the carbon black-containing polypropylene-based resin foam particles according to any one of claims 1 to 4.