JP2017197644A - Polypropylene resin particles for foaming and formed particles of the same, and in-mold foamed molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-mold foamed molding member which does not lose clear hue and glossiness of the surface and is excellent in color development property even when the in-mold foamed molding member uses a polypropylene resin having high strength.SOLUTION: Polypropylene resin particles for foaming are used which contain a polypropylene resin having a melting point of 150°C or higher and 160°C or lower, heat of crystal fusion of 75 mJ/mg or more and 100 mJ/mg or less and a melt index of 5 g/10 min or more and 13 g/10 min or less as a raw material, 1 pts.wt. or more and 6 pts.wt. or less of a pigment and 0.001 pts.wt. or more and 1 pts.wt. or less of a phosphoric acid crystal nucleator; and have a particle weight of 0.1 mg or more and 100 mg or less.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing expanded polypropylene resin particles. More specifically, the present invention relates to a polypropylene resin particle that provides an in-mold foam-molded member having a bright color and high strength.

  The polypropylene resin-in-mold foam molded product obtained by filling polypropylene resin foam particles in a mold and heat-sealing with steam is a lightweight and shock-absorbing characteristic that is a characteristic of a foam, and has an arbitrary shape. Since it can be molded freely, it is used for various purposes such as returnable boxes and cushion mats. Compared to polystyrene and polyethylene resin foam moldings, polypropylene resin foam moldings are superior in heat resistance, so there is little change in shape and physical properties even under high temperature conditions, and advanced physical properties and quality under severe conditions. It is also actively used for automobile parts that are required. In recent years, in applications such as automobile parts, further weight reduction has been demanded mainly for the purpose of reducing raw material costs and improving fuel consumption. Each member is required to have a certain strength, and it is necessary to satisfy the strength target. That is, in order to reduce the weight of the member, not only a technique for increasing the foaming of the resin but also a technique for improving the strength of the foamed molded body is required.

  The strength of the foamed molded product in the polypropylene resin mold is evaluated by the compressive strength of the foamed molded product. The compressive strength of the foamed molded product is proportional to the strength of the polypropylene resin that is usually used as a base material.

  It is known that the strength of a polypropylene resin is generally advantageous when it has a high melting point and a high crystallinity.

  On the other hand, the demand for the appearance of automobile members and the like has become stricter because the part where the foamed member can be used has been expanded and the chance of direct contact has increased. For example, a device has been devised, such as mixing a material with carbon black and coloring the member black to produce a high-class feeling.

  However, since a high-crystallinity polypropylene-based resin is used for a member that requires strength, the resin itself loses its transparency, and further foaming increases the gloss of the surface of the member. Even if it is lost, it is not possible to produce a vivid color even if it is colored.

  As a technique for increasing the crystallinity while maintaining the transparency of the polypropylene resin, there is a technique for adding a crystal nucleating agent.

  For example, Patent Document 1 discloses a packing band in which a nucleating agent of a phosphate ester metal salt is added to a polypropylene resin. However, there is no mention of the strength and color developability of the foamed member having a complex air bubble (hereinafter sometimes referred to as a cell) structure.

  Patent Document 2 discloses foamed particles made of a polypropylene resin composition containing one or more crystal nucleating agents selected from organic phosphorus crystal nucleating agents, aluminum crystal nucleating agents, and sorbitol crystal nucleating agents. Yes. However, a crystal nucleating agent is added for the purpose of suppressing fusion of the foamed particles in the production process, and there is no description about the strength as a foamed member or the color development improving effect when a pigment is added.

  Further, Patent Document 3 discloses that by adding an organoaluminum nucleating agent to polypropylene resin particles, it is possible to provide a polypropylene resin in-mold foam molded body with improved rigidity without impairing lightness. . However, there is no description regarding the color developability of the molded article.

JP 2004-346122 A JP2007-023172 JP 05-179049 A

  The present invention provides an in-mold foam molding excellent in color development without losing the vivid color and gloss of the surface, even if it is an in-mold foam molding member using a polypropylene resin having high strength and high crystallinity. The purpose is to provide materials.

  By adding 0.001 part by weight or more and 1 part by weight or less of a phosphate crystal nucleating agent to a resin composition comprising 1 part by weight or more and 6 parts by weight or less of pigment based on 100 parts by weight of a specific polypropylene resin. The present inventors have found that it is possible to provide a high-strength, high-strength polypropylene resin-in-mold foam-molded article with improved color development.

That is, this invention consists of the following structures.
[1] For 100 parts by weight of a polypropylene resin having a melting point of 150 ° C. or more and 160 ° C. or less, a crystal melting heat of 75 mJ / mg or more and 100 mJ / mg or less, and a melt index of 5 g / 10 min or more and 13 g / 10 min or less. Polypropylene resin particles for foaming having a particle weight of 0.1 mg or more and 100 mg or less, comprising a pigment of not less than 6 parts by weight and not more than 6 parts by weight and a phosphate crystal nucleating agent of not less than 0.001 part by weight and not more than 1 part by weight.
[2] The polypropylene resin particle according to [1], wherein the polypropylene resin contains 1-butene as a comonomer.
[3] The polypropylene resin particles as described in [1] to [2], wherein the pigment is carbon black.
[4] The polypropylene resin particles as described in [1] to [3], wherein the phosphate crystal nucleating agent is a sodium salt and / or an aluminum salt.
[5] The phosphate crystal nucleating agent is aluminum-hydroxy-bis [2,2′-methylene-bis (4,6-di-tert-butylphenyl) phosphate] and / or sodium- [2,2 ′. Polypropylene resin particles according to [1] to [4], which are -methylene-bis (4,6-di-tert-butylphenyl)] phosphate.
[6] The method for producing polypropylene resin particles according to any one of [1] to [6].
[7] Polypropylene resin expanded particles of the polypropylene resin particles according to any one of [1] to [6].
[8] A method for producing expanded polypropylene resin particles, wherein the expanded particles according to [7] are produced by a decompression foaming method.
[9] An in-mold foam molded product of the polypropylene resin foamed particles according to [7].

  According to the present invention, even a polypropylene resin in-mold foam-molded product whose strength is improved by using a resin having a high degree of crystallinity, a high-grade member that does not impair color developability with the addition of a small amount of pigment. Can provide.

It is a figure which shows the DSC curve of a polypropylene resin.

  The polypropylene resin particles for foaming of the present invention comprise 1 part by weight or more and less than 6 parts by weight pigment and 0.001 part by weight or more and 1 part by weight or less of a phosphorus crystal nucleating agent with respect to 100 parts by weight of a specific polypropylene resin. It is characterized by including.

  The polypropylene resin used in the present invention is not particularly limited, and is a polypropylene homopolymer, an ethylene / propylene random copolymer, a butene-1 / propylene random copolymer, an ethylene / butene-1 / propylene random copolymer, Examples thereof include an ethylene / propylene block copolymer, a butene-1 / propylene block copolymer, a propylene-chlorinated vinyl copolymer, and a propylene / maleic anhydride copolymer. Among these, those containing 1-butene as a comonomer such as butene-1 / propylene random copolymer and ethylene / butene-1 / propylene random copolymer have excellent melting point match strength and good moldability. From the point of having, it is suitable. The comonomer content in the butene-1 / propylene random copolymer or ethylene / butene-1 / propylene random copolymer is preferably 0.2% by weight to 10% by weight in 100% by weight of each copolymer. Used for.

  There is no restriction | limiting in particular as a polymerization catalyst at the time of synthesize | combining the polypropylene resin used by this invention, A Ziegler catalyst, a metallocene catalyst, etc. can be used.

  The melting point of the polypropylene-based resin used in the present invention is not less than 150 ° C. and not more than 150 ° C., since the effect of improving the strength and color developability of the in-mold foam-molded product which is the use form of the present invention appears remarkably. 156 ° C. or lower is preferable.

  When the temperature is lower than 150 ° C., the compression strength of the in-mold foam molded article is low, and the crystallinity of the resin itself is low. When it exceeds 160 degreeC, a moldability may deteriorate and it may become difficult to obtain a favorable in-mold foaming molding.

  The heat of crystal melting of the polypropylene resin used in the present invention is 75 mJ / mg or more and 100 mJ / mg or less of crystal melting heat. When the degree of crystallinity of the polypropylene resin is less than 75 mJ / mg, it is easy to obtain a glossy and colorful in-mold foam molded product without using the technique of the present invention. The compressive strength is low, which is disadvantageous for reducing the weight of the member. When it exceeds 100 mJ / mg, since the amount of crystals is large, moldability is deteriorated, and it becomes difficult to obtain a good in-mold foam molded article. The melting point and the heat of crystal melting of the polypropylene resin are obtained as follows. After melting 4 to 6 mg polypropylene resin from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min by DSC method (Seiko Instruments Inc .: DSC 6200 type), 10 ° C./min The crystal melting peak temperature of the DSC curve obtained when the temperature is lowered from 220 ° C. to 40 ° C. for crystallization and the temperature is raised again from 40 ° C. to 220 ° C. at a temperature raising rate of 10 ° C./min. The melting point of the system resin. Moreover, the calorie | heat amount computed from the area which a DSC curve and a base line enclose was made into the crystal melting calorie | heat amount of polypropylene resin.

  The melt index (hereinafter referred to as “MI”) of the polypropylene resin used in the present invention is 5 g / 10 min or more and 13 g / 10 min or less. In this case, it is easy to obtain expanded particles and in-mold expanded molded articles having a high magnification and a high closed cell ratio. Here, the MI value is a value measured according to JIS K7210 under the conditions of a load of 2160 g and 230 ± 0.2 ° C.

  Examples of the phosphoric acid crystal nucleating agent contained in the polypropylene resin particles in the present invention include aluminum-hydroxy-bis-2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate, sodium. -2,2'-methylene-bis- (4,6-di-t-butylphenyl) phosphate, sodium-bis- (4-t-butylphenyl) phosphate, magnesium-2,2'-methylene-bis -(4,6-di-t-butylphenyl) phosphate, potassium-2,2'-methylene-bis- (4,6-di-t-butylphenyl) phosphate, calcium-2,2'-methylene -Bis- (4,6-di-t-butylphenyl) phosphate, zinc-2,2'-methylene-bis- (4,6-di-t-butylphenyl) phosphate Sodium-2,2′-methylene-bis- (4-methyl-6-tert-butylphenyl) phosphate, sodium-2,2′-methylene-bis- (4-ethyl-6-tert-butylphenyl) ) Phosphate, sodium-2,2′-methylene-bis- (4,6-dimethylphenyl) phosphate, sodium-2,2′-methylene-bis- (4,6-di-t-octylphenyl) phosphate It is preferable that it is 1 type or 2 types or more, such as a fate.

  Of these crystal nucleating agents, aluminum-hydroxy-bis-2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate, sodium More preferably one or more of 2,2′-methylene-bis- (4,6-di-t-butylphenyl) phosphate and sodium-bis- (4-t-butylphenyl) phosphate, Aluminum-hydroxy-bis-2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate, sodium-2,2′-methylene-bis- (4,6-di-t-butyl) Most preferred is phenyl) phosphate. The addition amount of the phosphoric acid based crystal nucleating agent is 0.001 part by weight or more and 1 part by weight or less, preferably 0.005 part by weight or more and 0.1 part by weight or less with respect to 100 parts by weight of the polypropylene resin. . When the addition amount of the phosphoric acid based crystal nucleating agent is less than 0.001 part by weight, the effect on the crystallization of the resin is small, and the effects of the present invention may not be sufficiently exhibited. When the amount exceeds 1 part by weight, the effect as a nucleating agent is manifested, and the cells of the expanded particles are miniaturized, so that the color may be light and variations may occur.

  Examples of the pigment contained in the polypropylene resin particles in the present invention include inorganic pigments such as carbon black, titanium dioxide, iron sesquioxide, yellow iron sesquioxide, black iron oxide, and calcium carbonate, and C.I. I. Pigment Blue, C.I. I. Pigment Yellow, C.I. I. Pigment Red, C.I. I. Examples thereof include, but are not limited to, organic pigments such as Pigment Violet. In the present invention, in particular, when an inorganic pigment is used, the color developability improving effect of the present invention is easily exhibited. Among inorganic pigments, carbon blacks such as furnace black, channel black, acetylene black, and lamp black, and carbon blacks having a particle diameter of preferably 30 nm or less, more preferably 20 nm or less are particularly effective. Easy to demonstrate. In the present invention, it is preferable to disperse the particles uniformly as fine particles, rather than the conductive carbon black that forms a network in the resin and exists as an aggregate.

  In the polypropylene resin particles of the present invention, various additives can be added as long as the effects of the present invention are not impaired. Examples of the additives include water absorbing agents, antioxidants, bubble nucleating agents, and light resistance. Examples include property improvers, flame retardants, antistatic agents, and conductive agents.

  Examples of the water absorbing agent include polyethylene glycol, glycerin [chemical name 1,2,3-propanetriol], melamine [chemical name 1,3,5-triazine-2,4,6-triamine] and the like. It is not limited to these. Particularly preferred water-absorbing agents include polyethylene glycol and glycerin.

  When a water absorbing agent is added, the amount added varies depending on the type of the water absorbing agent, but is preferably 1 part by weight or less, more preferably 0.5 part by weight or less. If the amount exceeds 1 part by weight, the foamed particles obtained by foaming the resin particles may shrink due to condensation of the internal water, and if severe, the foamed particles may be crushed.

  Examples of the bubble nucleating agent include, but are not limited to, talc, kaolin, barium sulfate, zinc borate, silicon dioxide and the like.

  The cell nucleating agent is preferably 0.01 parts by weight or more and 0.5 parts by weight or less, and more preferably 0.05 parts by weight or more and 0.2 parts by weight or less. When the amount is less than 0.01 part by weight, the variation in the cells of the expanded particles becomes large, and the moldability and color developability may be deteriorated. If it exceeds 0.5 parts by weight, the cell becomes fine, and the moldability and color developability may deteriorate.

  Examples of the antioxidant include, but are not limited to, phenolic antioxidants and phosphorus antioxidants.

  Examples of the light resistance improver include hindered amine light resistance improvers, but are not limited thereto.

  Examples of the flame retardant include, but are not limited to, halogen flame retardants, phosphorus flame retardants, hindered amine flame retardants, and the like.

  The additive can be melt-kneaded with a polypropylene resin using an extruder, kneader, Banbury mixer, roll, or the like in advance, but is not limited thereto. Among these, from the viewpoint of productivity, an extruder such as a single screw extruder or a co-directional twin screw extruder is more preferably used. In order to melt the polypropylene resin with an extruder, the temperature of the melt kneading part of the extruder is preferably 180 ° C. or higher and 250 ° C. or lower. If it is less than 180 ° C, the melting point of the polypropylene resin may be 150 ° C or higher, so that it may not melt sufficiently. If it exceeds 250 ° C, degradation of the polypropylene resin and various additives is promoted, resulting in deterioration of physical properties, quality, and molding defects. May be invited.

  As a method of molding the polypropylene resin particles of the present invention, the resin is extruded in a strand form from the tip of the extruder, the resin is sufficiently solidified through a cooling tank, and then the strand is cut with a pelletizer or the like. There is an underwater cut method in which a cutter is directly attached to the tube and cutting in a semi-molten state in warm water, and a watering cutter method in which cutting is performed in the air, but is not limited thereto. The strand cut method is preferred in the sense that the equipment cost is low and the handling property is excellent.

  The weight per one polypropylene resin particle in the present invention is from 0.1 mg to 100 mg, preferably from 0.3 mg to 10 mg. The resin particles of the present invention are foamed by a foaming process to be described later to become polypropylene resin foamed particles. When the weight per resin particle is less than 0.1 mg, the expansion ratio of the polypropylene resin foamed particles tends to be difficult when foaming the resin particles. When the weight exceeds 100 mg, the resin particles When the foamed polypropylene resin particles are subjected to in-mold foam molding, which will be described later, the filling property into a thin portion tends to be poor. Here, the weight per one of the resin particles is the average resin particle weight obtained from 100 particles selected at random.

  In addition, the weight per one polypropylene resin particle hardly changes even after the foaming process, and the weight per one resin particle may be a problem as the weight per one polypropylene resin particle. There is no.

  The shape of the polypropylene resin particles is not particularly limited, but an elliptical columnar shape, a cylindrical shape, or a spherical shape is easily obtained from the viewpoint of ease of manufacture.

  The polypropylene resin particles of the present invention include a crystal nucleating agent and a pigment. The melting point, MI, and crystal melting heat amount of the resin particles are almost the same as the melting point, MI, and crystal melting heat amount of the polypropylene resin as the base resin. There is no change and can be regarded as equivalent. When the foamed particles of the resin particles and the in-mold foam-molded product are melted at 200 ° C. under vacuum and returned to a resin state without bubbles, the physical properties are hardly changed. Further, the amounts of the crystal nucleating agent and the pigment contained in the resin particles hardly change even in the foaming process and the in-mold foam molding process.

  Polypropylene resin foamed particles can be produced using the polypropylene resin particles of the present invention thus obtained. Examples of the method for producing foamed particles (foaming step) include a decompression foaming method, an extrusion foaming method, a pre-foaming method, and the like. Although not limited thereto, a decompression foaming step is suitable.

  For example, when producing the foamed particles using a decompression foaming method, the polypropylene resin particles, an aqueous medium, an inorganic dispersant, a foaming agent, and the like are housed in a pressure resistant container and dispersed under stirring conditions. After raising the temperature above the softening point temperature of the polypropylene-based resin particles, if necessary, hold the temperature after the temperature rise for more than 0 minutes and not more than 120 minutes, and then in a pressure vessel lower than the pressure inside the pressure vessel The dispersion liquid therein can be discharged to produce polypropylene resin expanded particles. The pressure range lower than the internal pressure of the pressure vessel is preferably atmospheric pressure. The dispersion is a mixed liquid in which polypropylene resin particles, an aqueous medium, an inorganic dispersant, a foaming agent, and the like are contained in a pressure vessel and dispersed under stirring conditions. There is no restriction | limiting in particular in the pressure | voltage resistant container used at the time of polypropylene-type resin expanded particle manufacture, What is sufficient is able to endure the pressure in a container and the temperature in a container, For example, an autoclave-type pressure | voltage resistant container is mentioned. Here, when the temperature in the pressure vessel is raised to the softening point temperature or higher, the temperature rises to a temperature in the range of the melting point of the polypropylene resin particles −20 ° C. or higher and the melting point of the resin particles + 10 ° C. or lower. It is preferable to warm it in order to ensure foamability. The temperature rising temperature is preferably in the range of 130 ° C. or higher and 170 ° C. or lower, but is appropriately determined depending on the type of polypropylene resin used as a raw material, the type of foaming agent, the target expansion ratio, and the like.

  As the aqueous medium, for example, water, alcohol, ethylene glycol, glycerin and the like can be used alone or in combination, but water is preferably used from the viewpoint of foamability, workability or safety, and water alone. It is most preferable to use in. The amount of the aqueous medium can be used as 50 to 500 parts by weight, preferably 100 to 350 parts by weight, with respect to 100 parts by weight of the polypropylene resin particles. If it is less than 50 parts by weight, coalescence of a plurality of polypropylene resin particles is likely to occur in the pressure vessel, and if it exceeds 500 parts by weight, the productivity is lowered, which is not preferable from the viewpoint of production.

  Examples of the inorganic dispersant include tricalcium phosphate, tribasic magnesium phosphate, magnesium carbonate, calcium carbonate, zinc carbonate, aluminum oxide, iron oxide, titanium oxide, aluminosilicate, kaolin, and barium sulfate. These can be used alone or in combination, but from the viewpoint of the stability of the dispersion, tricalcium phosphate, kaolin or barium sulfate is preferred. When the stability of the dispersion is lowered, a plurality of polypropylene resin particles are coalesced or agglomerated in the pressure vessel to obtain fused polypropylene resin foam particles, or a polypropylene resin in the pressure vessel In some cases, a lump of particles may remain and polypropylene resin foam particles cannot be produced, or the productivity of polypropylene resin foam particles may be reduced.

  In order to improve the stability of the dispersion in the pressure vessel, it is preferable to use a dispersion aid. Examples of the dispersion aid include anionic surfactants, and specifically, for example, sodium dodecylbenzenesulfonate, sodium alkanesulfonate, sodium alkylsulfonate, sodium alkyldiphenyl ether disulfonate, α-olefinsulfonic acid. Sodium etc. are mentioned.

  The amount of the inorganic dispersant and dispersion aid used varies depending on the type and the type and amount of polypropylene resin particles used, but usually 0.1 wt.% Of the inorganic dispersant with respect to 100 parts by weight of the aqueous medium. It is preferably 5 parts by weight or more and 5 parts by weight or less, and preferably 0.001 part by weight or more and 0.3 parts by weight or less of the dispersion aid. If the amount is too small, the coalescence of a plurality of polypropylene resin particles in the pressure vessel cannot be inhibited. If the amount is too large, the amount of the dispersant remaining on the surface of the expanded polypropylene resin particles increases, which is not preferable because it causes the fusion between the expanded polypropylene resin particles in the molding described later.

  Examples of the foaming agent include organic foaming agents such as propane, normal butane, isobutane, normal pentane, isopentane, hexane, cyclopentane, and cyclobutane, and inorganic foaming agents such as carbon dioxide, water, air, and nitrogen. . These foaming agents may be used alone or in combination of two or more. Among these foaming agents, isobutane and normal butane are superior from the viewpoint of easily improving the expansion ratio, but from the viewpoint of safety, inorganic foaming agents such as carbon dioxide, water, air, and nitrogen are used. It is preferable to use a foaming agent containing carbon dioxide gas.

  There is no limitation on the amount of the foaming agent used, and the foaming agent may be appropriately used according to the desired expansion ratio of the polypropylene resin foam particles. Usually, it is 2 parts by weight or more and 60 parts by weight with respect to 100 parts by weight of the polypropylene resin particles. It is preferable that it is below the weight part.

  By the way, if necessary, the expanded polypropylene resin particles (referred to as “one-stage expanded particles”) obtained by expanding the expanded polypropylene resin particles may be expanded again to expand the high-magnification expanded particles (“two-stage expanded particles”). Called "particles").

  For example, single-stage expanded particles are produced by pressure-reducing foaming, and the single-stage expanded particles are put in a pressure-resistant container and applied at a pressure of 0.1 MPa (gauge pressure) to 0.6 MPa (gauge pressure) with nitrogen, air, carbon dioxide gas, or the like. It is possible to obtain a two-stage expanded particle having a high expansion ratio by heating the first-stage expanded particle with steam or the like after the pressure in the first-stage expanded particle is made higher than the normal pressure by pressure treatment. Is possible.

  The cell diameter of the obtained expanded particles is preferably 100 μm or more and less than 400 μm, more preferably 150 μm or more and less than 400 μm. If the thickness is less than 100 μm, the thickness of the cell membrane of the foam particles is reduced, and the amount of carbon black per unit area is reduced, so that the colors of the foam particles and the in-mold foam molded product may be deteriorated. If it is 400 μm or more, even if the moldability and color look good, the strength of the expanded particles and the in-mold expanded molded product may be extremely reduced.

  In the present invention, as a method for producing a polypropylene resin-molded foam-molded body from polypropylene-based resin foamed particles, for example, the polypropylene resin foamed particles are filled in a mold that can be closed but cannot be sealed, As a heating medium, the polypropylene resin foamed particles are fused together by heating for about 3 seconds to 30 seconds with a steam pressure of about 0.05 MPa (gauge pressure) or more and 0.5 MPa (gauge pressure) or less. Then, after the mold is cooled with water and cooled to such an extent that the deformation of the in-mold foam molded article after the in-mold foam molded article is taken out, the mold is opened to obtain an in-mold foam molded article. It is done.

  The foamed molded body obtained by in-mold molding the foamed particles obtained using the polypropylene resin particles of the present invention is preferably used for automobile interior materials such as tool boxes and flooring materials, and electrification Examples include, but are not limited to, product packing materials and returnable boxes.

  Next, although this experiment is demonstrated based on an Example and a comparative example, this invention is not limited to these Examples.

Moreover, the evaluation in an Example and a comparative example was performed with the following method.
(Resin and additive used in Examples and Comparative Examples)
(1) Polypropylene resin / polypropylene resin A: Butene-propylene random copolymer Melting point 153 ° C., heat of crystal melting 88 mJ / mg, MI = 8.8 g / min
Polypropylene resin B: ethylene-propylene-butene random copolymer Melting point 150 ° C., heat of crystal melting 81 mJ / mg, MI = 12.3 g / min
(2) Pigment / carbon black: # 1000 (Mitsubishi Chemical)
(3) Crystal nucleating agent / crystal nucleating agent A: Aluminum-hydroxy-bis-2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate / crystal nucleating agent B: sodium-2, 2'-methylene-bis- (4,6-di-t-butylphenyl) phosphate / crystal nucleating agent C: 1,3: 2,4-bis-O- (4-methylbenzylidene) -D-sorbitol

(Melting point of polypropylene resin and heat of crystal melting)
The measurement was carried out in the following steps by the DSC method (Seiko Instruments Co., Ltd .: DSC6200 type).
(1) Resin 4 mg or more and 6 mg or less at 40 ° C. to 220 ° C. at a temperature rising rate of 10 ° C./min
The temperature was raised to 0 ° C. to melt.
(2) Next, the temperature was lowered from 220 ° C. to 40 ° C. at a temperature lowering rate of 10 ° C./min to cause crystallization.
(3) Again, the melting point is the crystal melting peak temperature of the DSC curve obtained when the temperature is raised from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min, and the heat of crystal melting from the area surrounded by the baseline and the DSC curve. Got. As shown in FIG.

(MI of polypropylene resin)
Based on JIS K7210, the measurement was performed under the conditions of a load of 2160 g and 230 ± 0.2 ° C.

(True magnification of expanded particles)
The weight w (g) of the foamed particles having a bulk volume of about 50 cm ³ and the ethanol submerged volume v (cm ³ ) were obtained, and obtained from the density d = 0.9 (g / cm ³ ) of the resin particles before foaming by the following equation. .
Expansion ratio of expanded particles (times) = d × v / w

(Density of in-mold foam molding)
A test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the obtained in-mold foam molded article. The vertical, horizontal and thickness dimensions were measured with calipers to determine the density (g / L).

(Cell diameter)
10 samples are taken out from the expanded particles, and the cut surface of each sample cut with great care so as not to destroy the cell membrane is observed with a microscope (manufactured by KEYENCE: VHX digital microscope), and the surface layer portion is removed. A line segment corresponding to a length of 1 mm was drawn on the part, and the number of cells through which the outer line segment passed was measured. Thereafter, the average cell diameter was measured according to ASTM D3576.

(Compressive strength of in-mold foam molding)
A test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the obtained in-mold foam molded product and compressed at a rate of 50% when compressed at a speed of 10 mm / min according to NDS-Z-0504. Stress (MPa) was measured and used as compressive strength.

(Color developability of in-mold foam molding (blackness))
An RGB analysis was performed using image processing software (DIBAS32) on an image obtained by scanning the surface of an in-mold foam molded body having a thickness of 10 mm with a printer multifunction machine (iR-ADV C5035).

The average value (measured value) of the total R, G, and B on the surface of the obtained molded body was quantified by the following formula on the basis of black 0 (100%) and white 255 (0%) to obtain blackness.
Blackness (%) of in-mold foam molded product = (255−measured value) / 255 × 100
The blackness of the in-mold foam molding is good when 88% or higher, and very good when 89% or higher.

(Examples 1-9, 11)
[Preparation of polypropylene resin particles]
Mixing polypropylene resin, carbon black as a pigment, crystal nucleating agent, and 0.5 parts by weight of polyethylene glycol and 0.1 parts by weight of talc, and mixing in the types and amounts shown in Table 1, with an extruder of 50 mmφ After kneading (resin temperature 210 ° C.) and extruding into a strand shape from the tip of the extruder, granulation was performed by cutting to produce resin particles (1.2 mg / particle).
[Production of polypropylene resin single-stage expanded particles]
A 10 L pressure vessel is charged with 300 parts by weight of water, 100 parts by weight of the obtained polypropylene resin particles, 1.0 part by weight of tribasic calcium phosphate as a dispersing agent, and 0.5 part by weight of norman paraffin sodium sulfonate as a dispersing aid. Further, 6.0 parts by weight of carbon dioxide gas was added as a foaming agent, the temperature was raised with stirring, and the mixture was held at the foaming temperature (container temperature) and foaming pressure (container pressure) shown in Table 1 for 30 minutes. While maintaining the foaming pressure with gas, the dispersion was discharged through a 3 mmφ orifice provided at the bottom of the pressure vessel into a foaming atmosphere maintained in the state shown in Table 1 to obtain single-stage foamed particles.
[Preparation of in-mold foam molding from single-stage expanded polypropylene resin particles]
Next, an internal pressure of 0.2 MPa (absolute pressure) was applied to the obtained single-stage expanded particles, and the resulting product was filled in a rectangular parallelepiped mold having a major axis of 400 mm, a minor axis of 300 mm, and a thickness of 50 mm, and water vapor (0.32 MPa (gauge pressure) )) For 12 seconds and fused to obtain an in-mold foam molded product, which was taken out of the mold. The in-mold foam molded product taken out from the mold was dried and cured in a dryer at 75 ° C. for 24 hours, and then the quality of the in-mold foam molded product was confirmed. The results are shown in Table 1.

(Example 10)
[Preparation of polypropylene resin particles]
Mixing polypropylene resin, carbon black as a pigment, crystal nucleating agent, and 0.5 parts by weight of polyethylene glycol and 0.1 parts by weight of talc, and mixing in the types and amounts shown in Table 1, with an extruder of 50 mmφ After kneading (resin temperature 210 ° C.) and extruding into a strand shape from the tip of the extruder, granulation was performed by cutting to produce resin particles (1.2 mg / particle).
[Production of polypropylene resin single-stage expanded particles]
A 10 L pressure vessel is charged with 300 parts by weight of water, 100 parts by weight of the obtained polypropylene resin particles, 1.0 part by weight of tribasic calcium phosphate as a dispersing agent, and 0.5 part by weight of norman paraffin sodium sulfonate as a dispersing aid. Further, 6.0 parts by weight of carbon dioxide gas was added as a foaming agent, the temperature was raised with stirring, and the mixture was held at the foaming temperature (container temperature) and foaming pressure (container pressure) shown in Table 1 for 30 minutes. While maintaining the foaming pressure with gas, the dispersion was discharged through a 3 mmφ orifice provided at the bottom of the pressure vessel into a foaming atmosphere maintained in the state shown in Table 1 to obtain single-stage foamed particles.
[Production of two-stage expanded polypropylene resin particles]
The obtained first-stage expanded particles were charged into a 1 m ³ pressure-resistant container and air-pressurized to give an internal pressure higher than normal pressure to the first-stage expanded particles. Subsequently, after transferring to a two-stage foaming machine, it was further foamed by heating with steam of 0.08 MPa (gauge pressure). When the magnification described in Table 1 was reached, heating was stopped to obtain two-stage expanded particles.
[Preparation of in-mold foam moldings from polypropylene resin two-stage expanded particles]
Next, an internal pressure of 0.2 MPa (absolute pressure) was applied to the obtained two-stage expanded particles, which was filled in a rectangular parallelepiped mold having a major axis of 400 mm, a minor axis of 300 mm, and a thickness of 50 mm, and water vapor (0.32 MPa (gauge Pressure)) for 12 seconds and fused to obtain an in-mold foam molded product, which was taken out of the mold. The in-mold foam molded product taken out from the mold was dried and cured in a dryer at 75 ° C. for 24 hours, and then the quality of the in-mold foam molded product was confirmed. The results are shown in Table 1.

(Comparative Examples 1-4, 6-10)
An in-mold foam molded article was obtained in the same manner as in Example 1 except that the polypropylene resin shown in Table 2, carbon black as a pigment, crystal nucleating agent, foaming temperature, and foaming pressure were used, and the quality was confirmed. The results are shown in Table 2.

(Comparative Example 5)
An in-mold foam molded article was obtained in the same manner as in Example 10 except that the crystal nucleating agent was not used, and the quality was confirmed. The results are shown in Table 2.

  Table 1 shows the results of evaluating the compression strength and color developability (blackness) of the obtained in-mold foamed molded products for Examples 1 to 10.

  From the results of Examples 1 to 10, it is shown that the foamed polypropylene resin particles obtained by the production method satisfying the requirements of the present invention can provide an in-mold foam molded article having good compressive strength and color developability.

  On the other hand, Table 2 shows the results of evaluating the compression strength and blackness of the obtained in-mold foamed molded products for Comparative Examples 1 to 10.

  In Comparative Examples 1 to 4, since no crystal nucleating agent was added, the blackness was low as compared with Examples 1 to 4 in Table 1, and in-mold foam molded articles having good color development were not obtained.

  In Comparative Example 5, since no crystal nucleating agent was added, an in-mold foam molded article having a low blackness and good color development was not obtained as compared with Example 10 in Table 1.

  In Comparative Examples 6 to 8, since the sorbitol crystal nucleating agent was used as the crystal nucleating agent, the effect of improving the coloring property was not exhibited with respect to Comparative Example 1, and an in-mold foam molded article having good coloring property was obtained. There wasn't.

  In Comparative Example 9, since the addition amount of the crystal nucleating agent was small, the effect of improving the color development was not exhibited with respect to Comparative Example 1, and an in-mold foam molded article having good color development was not obtained.

  In Comparative Example 10, since the amount of the crystal nucleating agent added is too large, the foamed cells are made finer, the blackness of the foamed particles is low and the variation occurs, and an in-mold foam-molded article with good color developability is obtained. There wasn't.

Claims (9)

  1 part by weight or more with respect to 100 parts by weight of a polypropylene resin having a melting point of 150 ° C. or more and 160 ° C. or less, a crystal melting heat of 75 mJ / mg or more and 100 mJ / mg or less, and a melt index of 5 g / 10 min or more and 13 g / 10 min or less. Polypropylene resin particles for foaming having a particle weight of 0.1 mg or more and 100 mg or less, comprising 6 parts by weight or less of pigment and 0.001 part by weight or more and 1 part by weight or less of a phosphoric acid crystal nucleating agent.   The polypropylene-based resin particles for foaming according to claim 1, wherein the polypropylene-based resin contains 1-butene as a comonomer.   The foaming polypropylene resin particles according to claim 1, wherein the pigment is carbon black.   The foaming polypropylene resin particles according to claim 1, wherein the phosphoric acid crystal nucleating agent is a sodium salt and / or an aluminum salt.   Phosphoric acid based crystal nucleating agent is aluminum-hydroxy-bis [2,2′-methylene-bis (4,6-di-tert-butylphenyl) phosphate] and / or sodium- [2,2′-methylene-bis It is a (4, 6- di-tert- butylphenyl)] phosphate, The polypropylene-type resin particle for foaming of Claims 1-4 characterized by the above-mentioned.   The manufacturing method of the polypropylene resin particle for foaming in any one of Claims 1-5.   Polypropylene resin expanded particles of the expanded polypropylene resin particles according to any one of claims 1 to 5.   A method for producing expanded polypropylene resin particles, wherein the expanded polypropylene resin particles for foaming according to any one of claims 1 to 5 are formed into a expanded particle by decompression foaming.   An in-mold foam molded product of the polypropylene resin expanded particles according to claim 7.

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