JP2009215485A - Method for producing foamed polypropylenic resin particles, foamed particles of polypropylenic resin and in-mold expansion formed articles of polypropylenic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing foamed polypropylenic particles having low expansion ratio by using an inorganic foaming agent, free from non-foamed resin particles in the foamed particles, having small variation of the expansion ratio among the foamed particles and having small variation of the foam film thickness among the foamed particles. <P>SOLUTION: The method for producing foamed polypropylene particles includes a step of charging a pressure vessel with polypropylenic resin particles containing ≥0.005 pt.wt. and ≤1 pt.wt. of an inorganic compound containing crystal water based on 100 pts.wt. of the polypropylenic resin, together with water, an inorganic dispersing agent and a dispersion assistant, a step of stirring and dispersing the content in the presence of an inorganic foaming agent while raising the temperature to increase the pressure in the pressure vessel to ≥0.9 MPa(G) and ≤3.5 MPa(G) and a step of releasing the dispersion liquid in the pressure vessel to a space having a pressure lower than the inner pressure of the pressure vessel, to effect the expansion of the particles. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polypropylene resin foamed particle molded into a molded body such as a buffer wrapping material, a return box, a core material for an automobile bumper, a heat insulating material, and the like, and a method for producing the same. More specifically, for example, the present invention relates to a polypropylene resin foamed particle that can be suitably used as a raw material for an in-mold foam molded article and a method for producing the same.

  Conventionally, a method in which polypropylene resin particles are dispersed in an aqueous dispersion medium together with a foaming agent, heated to constant pressure and constant temperature, impregnated with the foaming agent in resin particles, and then released into a low-pressure atmosphere to obtain foamed particles. It has been known. Examples of the blowing agent include a method using a volatile organic blowing agent such as propane and butane (for example, Patent Document 1) and a method using an inorganic gas such as carbon dioxide, nitrogen, and air (for example, Patent Documents 2 and 3). It is disclosed.

  However, volatile organic foaming agents such as propane and butane are easy to obtain a high foaming ratio, but have the effect of plasticizing polypropylene resin, and the plasticizing action is large. Control is difficult. Moreover, since it is a flammable substance, it is necessary to make the equipment explosion-proof, resulting in high equipment costs.

  On the other hand, a method using an inorganic foaming agent such as nitrogen, air, carbon dioxide or water used as a dispersion medium has also been proposed. When such a foaming agent is used, the ability to impregnate polypropylene-based resin is relatively low, which is suitable for producing low-magnification foamed particles (for example, Patent Documents 4 and 5).

  However, large bubbles and small bubbles are mixed in the expanded particles, resulting in large variations in the bubble film thickness. As a result, when the expanded particles produced using an inorganic foaming agent are used as in-mold expanded molded articles, It has been pointed out that the mechanical strength is reduced, and voids are formed on the surface of the molded body to lower the surface property.

  As a method of solving such a problem that the film thickness variation becomes large, the foaming pressure is set to a relatively low foaming pressure of 0.6 to 1.4 MPa (G) while using an inorganic foaming agent, It has been proposed to reduce the pressure difference at the time of discharge (for example, Patent Document 6). Further, Patent Document 6 describes that when the foaming pressure is a high pressure of 1.47 MPa (G), the bubble film thickness variation in the foamed particles is as large as 0.709.

  However, when the foaming pressure is low, the variation in magnification between the foamed particles becomes large, and in some cases, there remains a problem that unfoamed resin particles are mixed in the foamed particles.

  On the other hand, Patent Document 4 describes a method for producing a polyolefin-based low-expanded particle with small magnification variation and small bubble variation, but the bubble variation in the document indicates the variation of the average cell diameter between the expanded particles. However, it does not disclose bubble variation or bubble film thickness variation within one foamed particle.

That is, in the production method for obtaining low expansion ratio polypropylene resin foamed particles using an inorganic foaming agent, unexpanded resin particles are not mixed in the expanded particles, and there is a variation in magnification between the expanded particles. No manufacturing method is known in which the bubble thickness variation in the expanded particles is small.
Japanese Patent Publication No.56-1344 Japanese Patent Publication No. 4-64332 Japanese Examined Patent Publication No. 4-64334 Japanese Patent Laid-Open No. 10-176077 Japanese Patent Laid-Open No. 2002-347025 JP 2001-151928 A

  The present invention provides a method for producing low-expanded polypropylene resin foam particles using an inorganic foaming agent, in which unfoamed resin particles are not mixed in the foam particles, It is an object of the present invention to provide a method for producing polypropylene-based resin expanded particles having small variation in magnification and small variation in cell thickness in expanded particles.

  As a result of intensive studies for solving the above problems, the present inventors have found that polypropylene-based resin expanded particles having a small variation in cell thickness when manufactured at a high expansion pressure, which has been impossible in the past, can be manufactured. Further, by adding specific production conditions, the bubble film thickness variation is small and the magnification variation is small, and the polypropylene resin expanded particles exhibiting a specific melting behavior are excellent in moldability. As a result, the present invention has been completed.

  That is, the first of the present invention is a polypropylene resin particle comprising 0.005 parts by weight or more and 1 part by weight or less of a crystal water-containing inorganic compound with respect to 100 parts by weight of a polypropylene resin, water, an inorganic dispersant, a dispersion After accommodating the auxiliary agent in the pressure vessel, the temperature is raised while stirring and dispersing in the presence of the inorganic foaming agent, and the pressure in the pressure vessel is increased to 0.9 MPa (G) or more and 3.5 MPa (G) or less. Then, the dispersion liquid in the pressure vessel is discharged into a pressure region lower than the internal pressure of the pressure vessel and foamed, wherein the polypropylene resin foam particles are 2 The melting peak ratio Z = Qh / (Ql + Qh) × calculated from the melting peak calorie Ql on the low temperature side and the melting peak calorie Qh on the high temperature side. 00 is 17% or more and 35% or less, the bubble film thickness variation S in the polypropylene resin expanded particles is less than 0.5, the expansion ratio is 2 times or more and 14 times or less, and the magnification variation R between the polypropylene resin expanded particles is It is related with the manufacturing method of the polypropylene resin expanded particle characterized by being 10% or less.

As a preferred embodiment,
(1) The pressure inside the pressure vessel is increased to 1.4 MPa (G) to 3.0 MPa (G) or less,
(2) When discharging and foaming the dispersion, the dispersion is discharged through a squeezing plate having an opening volume of 20 mm ³ or more and 150 mm ³ or less.
(3) The high temperature side melting peak ratio Z = Qh / (Ql + Qh) × 100 is 19% or more and 28% or less,
(4) Comprising 0.01 parts by weight or more and 3 parts by weight or less of the water-absorbing substance with respect to 100 parts by weight of the polypropylene resin.
(5) the water-absorbing substance is polyethylene glycol and / or melamine,
(6) The hardness of water is 0 mg / L or more and 180 mg / L or less,
It is related with the manufacturing method of the polypropylene resin expanded particle of the said description.

  The second aspect of the present invention is a foamed polypropylene resin particle comprising 0.005 parts by weight or more and 1 part by weight or less of a crystal water-containing inorganic compound with respect to 100 parts by weight of the polypropylene resin. It has two melting peaks, and among these melting peaks, the high-temperature side melting peak ratio Z = Qh / (Ql + Qh) × 100 calculated from the low-temperature side melting peak heat amount Ql and the high-temperature side melting peak heat amount Qh is 17% or more. 35% or less, the bubble film thickness variation S in the polypropylene resin expanded particles is less than 0.5, the expansion ratio is 2 times or more and 14 times or less, and the magnification variation R between the polypropylene resin expanded particles is 10%. The third aspect of the present invention relates to a foamed polypropylene resin particle characterized in that the mold is filled with the polypropylene resin foamed particle described above. And relates to a polypropylene resin-mold foamed article obtained by heating.

  According to the production method of the present invention, low-expanding ratio polypropylene-based resin foamed particles can be obtained by expanding polypropylene-based resin foams with small variation in the ratio between the foamed particles with less bubble film thickness variation and no unexpanded particles intermingled. Particles can be obtained. In addition to the above properties, the obtained polypropylene foam particles exhibit a specific melting behavior. Therefore, when the polypropylene resin foam particles are used for in-mold foaming, the fusion rate is high, and the intergranular, shrinkage, and strain are high. It is possible to obtain an excellent polypropylene resin-in-mold foam-molded article having a small surface property and a beautiful surface property.

  In the present invention, polypropylene resin particles comprising 0.005 parts by weight or more and 1 part by weight or less of a crystal water-containing inorganic compound, water, an inorganic dispersant, and a dispersion aid are pressure-resistant to 100 parts by weight of a polypropylene resin. After being housed in a container, the temperature is raised while stirring and dispersing in the presence of an inorganic foaming agent, and the pressure in the pressure vessel is raised to 0.9 MPa (G) or more and 3.5 MPa (G) or less. A method for producing a expanded polypropylene resin particle, wherein the dispersion liquid in the container is released into a pressure range lower than the internal pressure of the pressure resistant container and foamed, wherein the expanded polypropylene resin particle has two melting peaks. The melting peak ratio Z = Qh / (Ql + Qh) × 100 calculated from the melting peak calorie Ql on the low temperature side and the melting peak calorie Qh on the high temperature side of the melting peak is 17%. 35% or less, the bubble film thickness variation S in the polypropylene resin foamed particles is less than 0.5, the expansion ratio is 2 to 14 times, the magnification variation R between the polypropylene resin expanded particles is 10% or less, It is a manufacturing method of the polypropylene resin expanded particle characterized by these.

  The polypropylene resin particles in the present invention comprise 0.005 parts by weight or more and 1 part by weight or less of a crystallization water-containing inorganic compound with respect to 100 parts by weight of the polypropylene resin. The water-containing inorganic compound has a function as a foam nucleating agent. The expanded polypropylene resin particles of the present invention are obtained through a high pressure condition in which the pressure inside the pressure vessel is increased to 0.9 MPa (G) or more and 3.5 MPa (G) or less. Polypropylene resin foam having a magnification variation R between the polypropylene resin foam particles of 10% or less and a bubble film thickness variation S within the polypropylene resin foam particles of less than 0.5 by using the polypropylene resin particles contained. Particles can be produced.

  The reason for this is not clear, but the polypropylene resin particles are placed under a high pressure condition of 0.9 to 3.5 MPa (G) in the water dispersion, and water is easily impregnated in the polypropylene resin particles. It is presumed that there is some relationship with the contact of the contained inorganic compound with water.

  Such a crystal water-containing inorganic compound is not particularly limited as long as it is an inorganic compound having crystal water or a hydrate of an inorganic compound. For example, aluminum oxide, aluminum sulfate, alum, barium hydroxide, barium nitrate, Barium silicate, calcium borate, calcium chloride, calcium nitrate, calcium phosphate, calcium hydrogen phosphate, calcium sulfate, iron chloride, iron nitrate, iron sulfate, iron phosphate, magnesium borate, magnesium carbonate, magnesium chloride, magnesium nitrate, phosphorus Magnesium oxide, magnesium sulfate, potassium carbonate, potassium borate, potassium phosphate, potassium hydrogen phosphate, potassium silicate, sodium borate, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium phosphate, sodium hydrogen phosphate, sulfuric acid Na Potassium, zinc nitrate, zinc borate, zinc phosphate, and inorganic compounds having such a crystalline water zinc sulfate, hydrates thereof. In addition, these crystal water containing inorganic compounds may be used independently and may use 2 or more types together.

  Furthermore, silicate minerals such as talc, montmorillonite, kaolin, halloysite, and zeolite, and borate minerals such as borax and colemanite also have water of crystallization or exist stably as hydrates. Therefore, it can be mentioned as the crystal water-containing inorganic compound of the present invention.

  Among these water-containing inorganic compounds, water-insoluble or sparingly soluble water-containing inorganic compounds are more preferable for expressing the effect of the foam nucleating agent. For example, aluminum oxide, calcium borate, calcium sulfate, boric acid Inorganic compounds containing crystal water such as magnesium, magnesium carbonate, zinc borate, zinc phosphate, etc., hydrates thereof, silicate minerals such as talc, montmorillonite, kaolin, halloysite, boron such as colemanite Examples include acid salt minerals. Of these, talc is most preferable.

  Such an inorganic compound containing crystal water that is insoluble or hardly soluble in water is suitable under conditions where water is easily impregnated into polypropylene resin particles at a high pressure of 0.9 MPa (G) to 3.5 MPa (G). However, it is presumed that it is difficult to dissolve in the impregnated water, and as a result, the effect as a foam nucleating agent is sufficiently exhibited, and the magnification variation R between the foamed particles targeted by the present invention is 10% or less. Thus, it is presumed that this is a preferred embodiment for producing polypropylene resin expanded particles having a bubble film thickness variation S of less than 0.5.

  Among these, in particular, it is a preferable aspect that talc is essential and other crystal water-containing inorganic compounds are used in combination, and specific examples include talc and sodium sulfate, talc and zinc borate, and the like.

  The amount of the crystal water-containing inorganic compound used in the present invention is 0.005 to 1 part by weight, preferably 0.01 to 0.5 part by weight, based on 100 parts by weight of the polypropylene resin. Parts by weight or less, most preferably 0.05 parts by weight or more and 0.3 parts by weight or less. If the amount is less than 0.005 parts by weight, the magnification variation R cannot be less than 10% and the cell thickness variation S cannot be less than 0.5. If the amount exceeds 1 part by weight, the average cell diameter of the polypropylene resin expanded particles is too small. In-mold foam moldability becomes poor. For example, when talc is used as an inorganic compound containing water of crystallization, a desired average cell diameter is easily obtained by using 0.02 parts by weight or more and 0.3 parts by weight or less with respect to 100 parts by weight of a polypropylene resin. It is preferable because the foam moldability is also good.

  As described above, in the present invention, the water-containing inorganic compound is contained in the polypropylene resin particles. As a matter of course, the water-containing inorganic compound is also contained in the resulting polypropylene resin foamed particles.

  The polypropylene resin expanded particles produced in the present invention have two melting peaks, and among these melting peaks, the high temperature side melting peak ratio Z calculated from the low temperature side melting peak heat quantity Ql and the high temperature side melting peak heat quantity Qh. = Qh / (Ql + Qh) × 100 is 17% or more and 35% or less, preferably 18% or more and 33% or less, and more preferably 19% or more and 28% or less. When the high-temperature side melting peak ratio is less than 17%, the obtained polypropylene resin foam particles are shrunk, wrinkles are generated, or the polypropylene resin in-mold foam molding obtained after in-mold foam molding tends to be deformed. When it exceeds 35%, the melt-bonding property and surface property of the polypropylene-based in-mold foam molded product are deteriorated.

  Note that the expanded polypropylene resin particles have two melting peaks, as shown in FIG. 1, in the DSC curve obtained by differential scanning calorimetry, which has two melting peaks, and the two melting peaks of the DSC curve. A point where the endothermic amount is the smallest between the peaks is A, and a tangent line is drawn from the point A to the DSC curve, and the portion surrounded by the tangent line and the DSC curve (the hatched portion in FIG. 1) is the high temperature side. The melting peak calorific value Qh and the low temperature side are defined as the melting peak calorie Ql on the low temperature side.

  In the case of the polypropylene resin foamed particles having two melting peaks, a polypropylene resin in-mold foam molded article having good in-mold foam moldability and good mechanical strength and heat resistance is obtained.

  Here, the DSC curve obtained by differential scanning calorimetry of the polypropylene resin expanded particles refers to 1 to 10 mg of polypropylene resin expanded particles from 40 ° C. to 220 ° C. at a temperature increase rate of 10 ° C./min by a differential scanning calorimeter. It is a DSC curve obtained when the temperature is raised.

  As described above, the expanded polypropylene resin particles having two melting peaks can be easily obtained by setting the temperature in the pressure resistant container at the time of foaming to an appropriate value. That is, in the case of the present invention, the temperature in the pressure vessel is usually not less than the softening temperature of the polypropylene resin as the base material, preferably not less than the melting point, more preferably not less than the melting point + 3 ° C., and preferably the melting end temperature. The melting end temperature is more preferably −2 ° C. or lower. In such a case, polypropylene resin expanded particles having two melting peaks tend to be obtained.

  The melting end temperature is a temperature of 10 to 10 ° C./min from 40 ° C. to 220 ° C. and then cooled to 40 ° C. at a rate of 10 ° C./min with a differential scanning calorimeter. The temperature at which the bottom of the melting peak of the DSC curve obtained when the temperature is raised again to 220 ° C. at a rate of 10 ° C./min returns to the baseline position on the high temperature side.

  Of the two melting peaks, the melting peak heat quantity Qh on the high temperature side is preferably 5 J / g or more and 30 J / g or less, and more preferably 7 J / g or more and 20 J / g or less. If it is less than 5 J / g, the open-cell ratio of the polypropylene resin foam particles tends to be high, and if it exceeds 30 J / g, the meltability in obtaining a polypropylene resin in-mold foam-molded product tends to decrease.

  The expansion ratio of the polypropylene resin expanded particles that can be produced in the present invention is 2 times or more and 14 times or less, preferably 3 times or more and 12 times or less, more preferably 3 times or more and 9 times or less. If it is less than 2 times, the buffering property is lowered, and if it exceeds 14 times, it becomes open-celled.

  Such an expansion ratio is obtained by setting the density of unexpanded particles to 900 g / L and dividing by the apparent density d of the polypropylene resin expanded particles.

  The magnification variation R between the expanded polypropylene resin particles produced in the present invention is 10% or less, more preferably 8% or less. When the magnification variation R exceeds 10%, the surface property of the polypropylene resin-in-mold foam-molded product is deteriorated.

  In addition, the magnification variation R is determined based on the standard sieves (nominal dimensions 1, 1.18, 1.4, 1.7, 2, 2.36, 2....) Of polypropylene resin expanded particles described in Appendix Table 2 of JIS Z8801 (1994). The weight fraction Wi of the foamed particles remaining on each sieve, the foaming ratio Ki, the average foaming ratio Kav, and the foaming ratio. Is calculated from the standard deviation σm, etc., and is represented by a magnification variation R = (σm / Kav) × 100 (%).

  The bubble film thickness variation S in the particles of the expanded polypropylene resin particles produced in the present invention is less than 0.5, preferably less than 0.4, and most preferably less than 0.2. Polypropylene resin-in-mold foam-molded products molded using polypropylene-based resin foam particles having a cell thickness variation S of 0.5 or more have low mechanical strength, poor fusion, and the like. A void-like hole is generated on the surface of the resin-molded foam-molded product, and the surface property is lowered.

The bubble thickness variation S of the present invention is an arithmetic average value of the bubble thickness variations sj (j = 1, 2, 3,..., 20) of 20 polypropylene resin foam particles randomly selected. is there. sj is determined in the same manner as the bubble film thickness variation described in Japanese Patent Laid-Open No. 2001-151928. ti is calculated from the average bubble film thickness tav, and is represented by bubble film thickness variation sj = Σ {(ti−tav) / tav} ² .

  In the present invention, the produced polypropylene resin expanded particles have an inter-particle magnification variation R of 10% or less, and the intra-cell bubble film thickness variation S satisfies both of the polypropylene resin expanded particles less than 0.5, When the above-described high-temperature side melting peak ratio Z = Qh / (Ql + Qh) × 100 is 17% or more and 35% or less, excellent characteristics are exhibited. In a polypropylene resin in-mold foam-molded article obtained using polypropylene resin foam particles having a size less than twice, the fusion-bonding property is excellent and the surface property is beautiful.

  The average cell diameter of the expanded polypropylene resin particles of the present invention is preferably 130 μm or more and 500 μm or less, more preferably 160 μm or more and 400 μm or less, and further preferably 210 μm or more and 350 μm or less. When the average cell diameter is less than 130 μm, the fusion-bonding property of the obtained polypropylene resin-in-mold foamed product tends to deteriorate, the shape tends to be distorted, and the surface tends to wrinkle. There exists a tendency for the buffering characteristic of an in-mold foaming molding to fall.

  Examples of the polypropylene resin used in the present invention include a propylene homopolymer, a propylene-α-olefin random copolymer, and a propylene-α-olefin block copolymer. Examples of the α-olefin include α-olefins having 2 to 4 to 15 carbon atoms, and these may be used alone or in combination of two or more. Further, two or more of the aforementioned propylene homopolymer, propylene-α-olefin random copolymer, and propylene-α-olefin block copolymer may be used in combination.

  Among these, in particular, a propylene-ethylene random copolymer, a propylene-ethylene-butene-1 random copolymer, and a propylene-butene-1 random copolymer, and the comonomer content other than propylene is 1 to 5% by weight. In some cases, it exhibits good foaming properties and can be suitably used.

  Although there is no restriction | limiting in particular in melting | fusing point of the polypropylene-type resin used by this invention, Foam limited in order to achieve the objective of this invention from which the bubble film thickness variation S becomes less than 0.5 even if it makes it foam by high foaming pressure. From the viewpoint of showing good foamability and moldability at a temperature, and easy to obtain expanded particles having excellent mechanical strength and heat resistance when formed into a polypropylene resin-molded foam-molded body, it should be 138 to 148 ° C. Preferably, it is 139-147 degreeC, Most preferably, it is 139-146 degreeC. When the melting point is less than 138 ° C., the heat resistance tends to decrease, and when it exceeds 148 ° C., the bubble film thickness variation S and the magnification variation R tend to increase.

  Here, the melting point is 1 to 10 mg of polypropylene resin is heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./min by a differential scanning calorimeter, and then cooled to 40 ° C. at a rate of 10 ° C./min. The peak temperature of the endothermic peak in the DSC curve obtained when the temperature is raised again to 220 ° C. at a rate of 10 ° C./min.

  Although there is no restriction | limiting in particular in the melt index of the polypropylene-type resin used by this invention, It is limited in order to achieve the objective of this invention that even if it makes it foam by high foaming pressure, the bubble film thickness variation S is less than 0.5. 4 to 9 g / 10 min g from the viewpoint of showing good foamability and moldability at the foaming temperature, and easily obtaining expanded particles having excellent mechanical strength and heat resistance when formed into a polypropylene resin mold. / 10 minutes are preferable, more preferably 4 to 8 g / 10 minutes, and most preferably 4 to 7 g / 10 minutes. When the melt index is less than 4 g / 10 minutes, the variation in magnification between the expanded particles tends to increase. When the melt index exceeds 9 g / 10 minutes, the bubble thickness variation S tends to exceed 0.5 and the expanded cell is broken. Foaming tends to increase the open cell rate of the polypropylene resin expanded particles.

  The melt index in the present invention is a value measured at a temperature of 230 ° C. and a load of 2.16 kg in accordance with JIS K7210.

  A preferred embodiment of the present invention includes adding a water-absorbing substance to the polypropylene-based resin, and such a water-absorbing substance is preferable because it has an effect of reducing the bubble film thickness variation S. Moreover, since there exists an effect which improves foamability, even if it does not set a big foaming pressure, there exists a tendency which can implement | achieve the foaming magnification of 10-14 times.

  Such a water-absorbing substance generally means a water-absorbing, hygroscopic, water-soluble or compatible substance, such as a water-soluble polymer, a water-absorbing polymer, a hydrophilic polymer, Water-soluble organic substances, water-absorbing organic substances, hydrophilic organic substances, water-soluble inorganic substances, water-absorbing inorganic substances, hydrophilic inorganic substances and the like can be mentioned.

  Although there is no restriction | limiting in particular in the water absorption rate of these substances, From a viewpoint of improving the expansion ratio of the polypropylene resin expanded particle obtained, 0.1% or more is preferable, More preferably, it is 0.5% or more. As a measuring method of such a water absorption rate, it can measure, for example based on ASTM D570.

  Specific examples of such a water-absorbing substance include the following substances.

  That is, (A) a copolymer having a polyalkylene glycol block (for example, peristat from Sanyo Chemical Industries, Ltd.), a compound having a polyalkylene glycol chain such as polypropylene glycol or polyethylene glycol, (B) sodium polyacrylate, Examples thereof include hydrophilic polymers such as cellulose and polyvinyl alcohol, (C) inorganic compounds such as zeolite, bentonite, synthetic hectorite (laponite), and boric acid metal salts.

  Further, (D) (a) cationic surfactants such as aliphatic amine salts, hydroxyalkyl monoethanolamine salts, aliphatic quaternary ammonium salts, (b) higher alcohol sulfate esters, alkane sulfonates, alkylbenzene sulfones. Acid salt, alkylnaphthalene sulfonate, sulfosuccinate, α-olefin sulfonate, N-acyl sulfonate, alkyl sulfate, alkyl ether sulfate, alkyl allyl ether sulfate, alkyl amide sulfate, alkyl phosphoric acid Anionic surfactants such as salts, alkyl ether phosphates, alkyl allyl ether phosphates, alkyl ether carboxylates, N-acyl amino acid salts,

  (C) Alkyl and alkylallyl polyoxyethylene ether, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropyl alkyl ether, glycerin ester polyoxyethylene ether, sorbitan ester polyoxyethylene ether, sorbitol ester poly Oxyethylene ether, polyethylene glycol fatty acid ester, glycerin ester, higher fatty acid glycerin ester, higher fatty acid and glycerin monoester, higher fatty acid and glycerin diester, higher fatty acid and glycerin triester, polyglycerin ester, sorbitan ester, propylene glycol ester , Sucrose ester, aliphatic alkanolamide, polyoxyethylene fatty acid ester De, polyoxyethylene alkylamine, nonionic surfactants such as amine oxides,

  (D) surfactants such as amphoteric surfactants such as carboxybetaine, imidazolinium betaine, and aminocarboxylate; (e) antistatic agents based on the above surfactants; (f) polyolefins An antistatic agent having a structure in which a block and a hydrophilic polymer block are repeatedly and alternately bonded through at least one bond selected from an ester bond, an amide bond, an ether bond, a urethane bond, and an imide bond. And antistatic agents described in claims of No. 3488163.

  (E) Melamine (chemical name: 1,3,5-triazine-2,4,6-triamine), ammelin (chemical name: 1,3,5-triazine-2-hydroxy-4,6-diamine) , Ammelide (chemical name: 1,3,5-triazine-2,4-hydroxy-6-amine), cyanuric acid (chemical name: 1,3,5-triazine-2,4,6-triol), isocyanuric acid (Chemical name: 1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione), acetoguanamine (chemical name: 1,3,5-triazine-2,4-diamine-6) Methyl), benzoguanamine (chemical name: 1,3,5-triazine-2,4-diamine-6-phenyl), tris (methyl) isocyanurate, tris (ethyl) isocyanurate, tris (butyl) isocyanurate Tris (2-hydroxyethyl) isocyanurate, such as melamine-isocyanuric acid condensation product, the molecular weight per unit triazine skeleton has a triazine skeleton may also be mentioned compounds of 300 or less. These water-absorbing substances may be used alone or in combination of two or more.

  Among these, more preferable water-absorbing substances are compounds having a polyalkylene glycol chain and compounds having a triazine skeleton and a molecular weight per unit triazine skeleton of 300 or less. Among these, polyethylene glycol or melamine is more preferable. Polyethylene glycol is a substance having extremely low toxicity, and it is possible to use the obtained polypropylene resin-in-mold foam-molded product for an application in contact with food.

  Furthermore, among polyethylene glycols, polyethylene glycol having an average molecular weight of 200 or more and 9000 or less is preferable, and polyethylene glycol having an average molecular weight of 200 or more and 600 or less is most preferable. In general, glycols have properties that are slightly inferior in compatibility with polypropylene resins, but for polyethylene glycol having a relatively low molecular weight such as an average molecular weight of 200 or more and 9000 or less, the polypropylene resin and polyethylene glycol are kneaded in an extruder, Polypropylene with small dispersion in bubble film thickness S and small magnification variation R with less occurrence of troubles such as strand breakage due to poor dispersion in the process of producing polypropylene resin particles by the strand cut method and unstable feeding of molten resin -Based resin expanded particles are obtained. Furthermore, the polypropylene resin mold in-mold molded using the polypropylene resin foam particles is beautiful with small intergranular / shrinkage / distortion, and the fusion rate of the polypropylene resin mold in the mold is small. It tends to be high and the heat-resistant dimensional stability is sufficient. It is also possible to use a mixture of polyethylene glycols having different molecular weights.

  The average molecular weight of polyethylene glycol can be measured using a liquid chromatograph mass spectrometer (for example, LCQ Advantage manufactured by Thermo Fisher Scientific).

  The amount of the water-absorbing substance used in the present invention is appropriately selected depending on the expansion ratio and the like. The amount of the water-absorbing substance is 0.01 to 3 parts by weight with respect to 100 parts by weight of the polypropylene resin. Preferably, it is 0.01 to 1 part by weight. If it is less than 0.01 part by weight, it may be difficult to obtain high-magnification polypropylene-based resin expanded particles. When the amount exceeds 3 parts by weight, the bubble film thickness variation S tends to deteriorate.

  In the present invention, in addition to the crystal water-containing inorganic compound and the water-absorbing substance, a compatibilizer, antistatic agent, colorant, stabilizer, weathering agent, flame retardant, etc. are appropriately added to such an extent that the effects of the present invention are not impaired. Is possible.

  As described above, polypropylene resin particles containing a polypropylene resin, a crystal water-containing inorganic compound, and, if necessary, a water-absorbing substance are used. As a method for producing polypropylene resin particles, a conventionally known method may be used. For example, a polypropylene resin, a crystal water-containing inorganic compound, and a blend of a water-absorbing substance and various additives as necessary are used in an extruder. And melt-kneading, extruding from a die, cooling, and then forming polypropylene resin particles with a cutter.

  In addition, the inorganic compound containing water of crystallization, and the water-absorbing substance and additives to be added as necessary are masterbatched with a polyolefin-based resin in advance, and the polypropylene-based resin is used so that the final addition amount is obtained. And melt-kneaded with an extruder to form polypropylene resin particles.

In the present invention, the hardness of water stored in the pressure vessel is preferably 0 mg / L or more and 180 mg / L or less. More preferably, the hardness is 0 mg / L or more and 120 mg / L or less, more preferably 0 mg / L or more and 60 mg / L or less, and most preferably more than 0 mg / L and 20 mg / L or less. Here, the hardness is a so-called American hardness obtained by converting the amount of calcium / magnesium contained in water into the amount of calcium carbonate, which is a commonly used hardness, and is generally expressed by the following equation. Can do.
Hardness (mg / L) = calcium amount (mg / L) × 2.5 + magnesium amount (mg / L) × 4.1

  If this hardness exceeds 180 mg / L, it is estimated that calcium or magnesium in water tends to deactivate the surfactant as a dispersion aid, and as a result, the dispersion in the pressure vessel is stabilized. In other words, the sticking phenomenon in which the obtained polypropylene resin foam particles are adhered to each other appears or the foam particles are flattened, whereby the magnification variation R tends to increase or the bubble film thickness variation S tends to increase. .

  If the water hardness exceeds 180 mg / L, the amount of the dispersion aid or inorganic dispersant may need to be increased, and if the amount of the inorganic dispersant increases, it adheres to the surface of the resulting polypropylene resin foam particles. There is a tendency that the amount of the inorganic dispersant to be increased increases and the fusing property of the polypropylene resin-in-mold foam-molded product is lowered.

  There is no restriction | limiting in particular in the measuring method of water hardness, What is necessary is just to measure using a conventionally well-known measuring method and apparatus. For example, measurement by chelate titration method using ethylenediaminetetraacetic acid (EDTA), flame-atomic absorption photometry, ion chromatography, inductively coupled plasma emission spectrometry, inductively coupled plasma mass spectrometry (ICP / MS method), etc. can do.

  There is no restriction | limiting in particular as an inorganic type dispersing agent used by this invention, The inorganic type dispersing agent generally used can be used.

  Specifically, aluminosilicates (kaolin, talc, etc.) based on barium sulfate and silica-alumina, aluminum oxide, titanium oxide, calcium phosphate (tricalcium phosphate, etc.), calcium carbonate, magnesium pyrophosphate, magnesium phosphate , Basic magnesium carbonate, basic zinc carbonate and the like.

  Among these, an aluminosilicate containing barium sulfate and / or silica-alumina as a main component is preferable from the viewpoint of having a dispersion effect with a small amount of use and a small wastewater treatment load.

  The amount of such an inorganic dispersant added is not particularly limited and is appropriately adjusted in order to express the stabilizing effect of the dispersion, and also takes into account the addition ratio with the dispersion aid. Although appropriately adjusted, it is preferably 0.01 parts by weight or more and 5 parts by weight or less, more preferably 0.05 parts by weight or more and 4 parts by weight or less, with respect to 100 parts by weight of the polypropylene resin particles. Most preferably, it is 0.1 to 3 parts by weight. If the amount is less than 0.05 parts by weight, the dispersibility of the resin particles tends to decrease at a temperature higher than the softening point temperature of the resin particles. If the amount exceeds 5 parts by weight, a large amount of the dispersant tends to adhere to the surface of the polypropylene resin expanded particles. .

  The surfactant that is a dispersion aid used in the present invention is not particularly limited, and generally used anionic, nonionic, cationic surfactants, and amphoteric surfactants may be used. I can do it.

  Specific examples of the dispersion aid used in the present invention include (i) higher alcohol sulfate ester salt, alkane sulfonate salt, alkyl sulfonate salt, alkyl benzene sulfonate salt, alkyl naphthalene sulfonate salt, sulfosuccinate salt, α-olefin sulfonate, N-acyl sulfonate, alkyl sulfate, alkyl ether sulfate, alkyl allyl ether sulfate, alkyl amide sulfate, alkyl phosphate, alkyl ether phosphate, alkyl allyl ether phosphate Anionic surfactants such as salts, alkyl ether carboxylates, N-acyl amino acid salts,

  (B) Alkyl and alkylallyl polyoxyethylene ether, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropyl alkyl ether, glycerin ester polyoxyethylene ether, sorbitan ester polyoxyethylene ether, sorbitol ester poly Oxyethylene ether, polyethylene glycol fatty acid ester, glycerin ester, higher fatty acid glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester, sucrose ester, aliphatic alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, amine Nonionic surfactants such as oxides,

  (C) Cationic surfactants such as aliphatic amine salts, hydroxyalkyl monoethanolamine salts and aliphatic quaternary ammonium salts; (d) Amphoteric surfactants such as carboxybetaine, imidazolinium betaine and aminocarboxylates. , Etc.

  From the viewpoint of the effect of stabilizing the dispersibility, the surfactant is preferably an anionic surfactant, more preferably an alkane sulfonate, an alkylbenzene sulfonate, an alkyl naphthalene sulfonate, a sulfosuccinate, or an α-olefin sulfone. Sulfonates such as acid salts, N-acyl sulfonates, alkyl sulfates, alkyl ether sulfates, alkyl allyl ether sulfates, alkyl amide sulfates, most preferably alkane sulfonates, α-olefin sulfonic acids Salt, alkylbenzene sulfonate.

  The addition amount of such a dispersion aid is not particularly limited and may be appropriately adjusted in order to develop a dispersibility stabilizing effect, but is 0.001 part by weight with respect to 100 parts by weight of the polypropylene resin particles. The amount is preferably 0.5 parts by weight or less, more preferably 0.003 parts by weight or more and 0.3 parts by weight or less, and most preferably 0.005 parts by weight or more and 0.2 parts by weight or less. If the amount is less than 0.001 part by weight, the dispersibility of the polypropylene resin particle tends to be lowered at a temperature higher than the softening point temperature of the polypropylene resin particle. If the amount exceeds 0.5 part by weight, foaming of the dispersion becomes intense and wastewater treatment is difficult. The load tends to increase.

  Next, the manufacturing method of the polypropylene resin expanded particle in this invention is demonstrated.

  The polypropylene resin expanded particles in the present invention are obtained by accommodating the polypropylene resin particles prepared as described above, water, an inorganic dispersant, and a surfactant as a dispersion aid in a pressure resistant container, and then expanding the inorganic resin foam. While increasing the temperature while stirring and dispersing in the presence of the agent, the pressure inside the pressure vessel is increased to 0.9 MPa (G) or more and 3.5 MPa (G) or less, and then the pressure is reduced to a pressure range lower than the pressure inside the pressure vessel. The dispersion in the container is released and foamed.

  There is no restriction | limiting in particular as an inorganic type foaming agent used by this invention, Air, nitrogen, oxygen, a carbon dioxide, water, helium, neon, argon etc. are mentioned, You may use these 2 or more types together. Among them, it is preferable to use any of air, nitrogen, carbon dioxide, and water from the viewpoint of safety and cost.

  In addition, when a polypropylene resin particle contains a water absorptive substance, water and / or carbon dioxide are suitable as a foaming agent.

The inorganic foaming agent other than water may be introduced into the pressure vessel at any stage before the dispersion is discharged to the low pressure region, and may be introduced into the pressure vessel before heating and heating. In addition, it may be introduced during heating and heating, may be introduced after heating, or may be introduced immediately before foaming. Further, foaming may be performed while being introduced so that the pressure in the pressure vessel does not decrease during foaming.
Furthermore, it may be introduced in several times or a plurality of inorganic foaming agents may be introduced. From the viewpoint of sufficiently impregnating polypropylene resin particles with an inorganic foaming agent and increasing foaming power, it is preferably introduced before heating, from the viewpoint of suppressing the magnification variation R of the resulting polypropylene resin foamed particles. Is preferably introduced during foaming.

  In the present invention, the pressure vessel internal pressure needs to be 0.9 MPa (G) or more and 3.5 MPa (G) or less, and is adjusted by appropriately introducing an inorganic foaming agent so as not to exceed this pressure. Can do. The pressure vessel internal pressure is preferably more than 1.4 MPa (G) and not more than 3.0 MPa (G). When the pressure is less than 0.9 MPa (G), the expansion ratio variation R between the expanded particles becomes large, or in some cases, unexpanded resin particles are mixed in the expanded particles. When it exceeds 3.5 MPa (G), the bubble diameter of the polypropylene resin foamed particles becomes fine, and the fusibility of the foamed molded product in the polypropylene resin mold decreases.

  In the present invention, other physical foaming agents may be used as needed, for example, saturated hydrocarbons having 3 to 5 carbon atoms, dimethyl ether, or boiling point below the foamable temperature. Alcohols such as methanol and ethanol can also be used.

In the present invention, when the dispersion is discharged and foamed, it is preferable to discharge the dispersion through a diaphragm having an opening volume of 20 mm ³ or more and 150 mm ³ or less. More preferred aperture volume is 40 mm ³ or more ～90Mm ³ or less.

As such a diaphragm, an orifice type, a nozzle type, a venturi type, etc. can be used, and these can also be combined. If the opening volume is 20 mm ³ or more and 150 mm ³ or less, the cross-sectional area, cross-sectional shape, and length (length of the portion through which the dispersion liquid passes) of the opening are such that the resin particles that are released are not clogged. If there is no limit.

If an aperture volume of less than 20 mm ³ is used to make a diaphragm that does not clog resin particles, the diaphragm thickness tends to be very thin. In addition, if the aperture volume exceeds 150 mm ³ and an attempt is made to make a diaphragm that does not clog polypropylene-based resin particles, the bubble film thickness variation S tends to increase.

  An example of an orifice type diaphragm is shown in FIGS. The product of the orifice cross-sectional area M in FIG. 2 and the orifice length L in FIG. 3 (L direction is the dispersion passing direction) is the opening volume.

  The foamed molded product within the polypropylene resin mold of the present invention is obtained by a molding method in which the polypropylene resin foam particles obtained as described above are filled in a mold and heated.

  There is no restriction | limiting in particular as such a shaping | molding method, A general method can be employ | adopted. For example, a method in which a polypropylene resin foamed particle can be closed but cannot be sealed is filled in a mold, heated with water vapor, etc., and the polypropylene resin foamed particles are heated and fused together to form the mold. It is done. In order to obtain a foamed molded product in a polypropylene-based resin mold with good fusing properties, mechanical strength, surface appearance, etc., the polypropylene-based resin foamed particles are pressurized under an inorganic gas such as air, nitrogen or carbon dioxide. It is preferable to adopt a method in which the inner pressure is applied to the expanded polypropylene resin particles while being held in the mold, and then filled into the mold and molded.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to such examples.

  In addition, evaluation in Examples and Comparative Examples was performed by the following method.

(Water hardness)
The calcium and magnesium concentrations in the aqueous medium were measured by inductively coupled plasma mass spectrometry, and were calculated in terms of the amount of calcium carbonate.

(Magnification variation R)
1 kg of the polypropylene resin expanded particles was added to a standard sieve (nominal dimensions 1, 1.18, 1.4, 1.7, 2, 2.36, 2.8, 3.35, described in Table 2 of JIS Z8801 (1994). 11 sieves (4, 4.75, 5.6). The weight fraction Wi and the expansion ratio Ki of the polypropylene resin expanded particles remaining on each sieve are measured, and the average expansion ratio Kav is calculated from the following formula (1).

次に重量分率Ｗｉ、発泡倍率Ｋｉと平均発泡倍率Ｋａｖを用いて式（２）

Next, using the weight fraction Wi, the expansion ratio Ki, and the average expansion ratio Kav, the formula (2)

から発泡倍率の標準偏差σｍを計算し、式（３）

Calculate the standard deviation σm of the foaming ratio from the equation (3)

から倍率バラツキＲ（％）を求めた。

From this, the magnification variation R (%) was determined.

In addition, the expansion ratio Ki of the polypropylene resin expanded particles remaining on each sieve was determined as follows. The weight Gi of the polypropylene resin foam particles remaining on each sieve is accurately weighed to 0.001 g (rounded off to the fourth decimal place), and then the weighed polypropylene resin foam particles of known weight are added with 100 ml of water at 23 ° C. The volume yi (cm ³ ) of the polypropylene resin foam particles is read from the scale that is raised when submerged in the water in the graduated cylinder accommodated, and the weight Gi (g) of the polypropylene resin foam particles is calculated as the polypropylene resin foam. By dividing by the volume yi (cm ³ ) of the particles and converting this to g / L units, the apparent density di of the polypropylene resin foamed particles of each sieve is determined. Finally, the expansion ratio Ki = ds / di was determined from the ratio with the density ds (= 900 g / L) of the base resin.

(Bubble thickness variation S)
Observe the cross section of the expanded polypropylene resin particles that have been cut so that they pass through almost the center of the randomly selected expanded polypropylene resin particles, and set the X and Y axes perpendicular to each other through the approximate midpoint O of the expanded foam cross section. Pull. Next, assuming that the intersections of the outermost layer of the expanded particle cross section and the X axis and Y axis are A, A ′, B, and B ′, respectively, four of line segment OA, line segment OA ′, line segment OB, and line segment OB ′ Get the line segment. Specifically, the number N of bubble walls on the line segment length li from the point O to each point A, A ′, B, B ′ on the screen or micrograph showing the cut surface on the microscope The average bubble diameter Li is determined from the following equation (4). However, when the point O exists on the bubble wall, the bubble wall is counted.

また、点Ｏから各点Ａ、Ａ’、Ｂ、Ｂ’までの線分上にある気泡膜厚ｔｉを下記の式（５）より求めた。

In addition, the bubble film thickness ti on the line segment from the point O to each point A, A ′, B, B ′ was determined from the following formula (5).

更に、４つのｔｉの相加平均を平均気泡膜厚ｔａｖとして下記の式（６）より求めた。

Furthermore, the arithmetic average of the four ti was obtained from the following formula (6) as the average cell thickness tav.

なお、式（５）に示したように、点Ｏから各点Ａ、Ａ’、Ｂ、Ｂ’までの線分上にある気泡膜厚ｔｉを上記Ｌｉとポリプロピレン系樹脂発泡粒子の見かけ密度ｄ及び基材樹脂の密度ｄｓより求めたが、本件発明においてｄｓは、９００ｇ／Ｌとする。

As shown in the equation (5), the bubble film thickness ti on the line segment from the point O to each point A, A ′, B, B ′ is expressed as the apparent density d of the Li and polypropylene resin expanded particles. In the present invention, ds is set to 900 g / L.

  From the obtained ti and tav, the bubble film thickness variation sj of one polypropylene resin foamed particle is obtained from the following formula (7).

同様に更に１９個の無作為に選んだポリプロピレン系樹脂発泡粒子について、前述の通りにして気泡膜厚バラツキｓｊを求め、ｓｊ（ｊ＝１、２、３、・・・、２０）の相加平均を下記の式（８）により求め、これを本発明の気泡膜厚バラツキＳとした。

Similarly, for 19 randomly selected expanded polypropylene resin particles, the bubble film thickness variation sj is obtained as described above, and the addition of sj (j = 1, 2, 3,..., 20). The average was obtained by the following formula (8), and this was used as the bubble film thickness variation S of the present invention.

なお、発泡粒子の見かけ密度ｄは、約５ｇ（４．５００〜５．５００ｇ）のポリプロピレン系樹脂発泡粒子をとり、これを０．００１ｇまで正確に秤量し（小数点以下４桁目を四捨五入）、次いで秤量された重量既知のポリプロピレン系樹脂発泡粒子を２３℃の水１００ｍｌが収容されたメスシリンダー内の水に水没させたときに上昇した目盛りから、ポリプロピレン系樹脂発泡粒子の体積Ｙ（ｃｍ^３）を算出し、ポリプロピレン系樹脂発泡粒子の重量（ｇ）をポリプロピレン系樹脂発泡粒子の体積Ｙ（ｃｍ^３）で除すことにより求められる。この場合単位はｇ／ｃｍ^３となるが、これをｇ／Ｌに換算した。

The apparent density d of the expanded particles is about 5 g (4.500-5.500 g) of polypropylene resin expanded particles, and this is accurately weighed to 0.001 g (rounded off to the fourth decimal place) Next, a volume Y (cm ³ ) of the polypropylene resin foamed particles is measured from a scale that rises when the weighed polypropylene resin foam particles of known weight are submerged in water in a graduated cylinder containing 100 ml of water at 23 ° C. Is calculated, and the weight (g) of the polypropylene resin expanded particles is divided by the volume Y (cm ³ ) of the polypropylene resin expanded particles. In this case, the unit is g / cm ³ , but this was converted to g / L.

(Average bubble diameter Lav)
The average bubble diameter Lav was calculated from the following formula (9) from Li measured on the screen or micrograph of the foamed particle cut surface of the above formula (4).

(Foaming ratio)
Using the apparent density d of the above-mentioned expanded particles, the expansion ratio K = ds / d was determined from the ratio to the density ds (= 900 g / L) of the base resin.

(Expanded particle shrinkage / wrinkles)
○: The surface of the expanded particle is beautiful without wrinkles. ×: The surface of the expanded particle is wrinkled and the expanded particle is contracted.

(Mold surface properties)
○: No wrinkles, little intergranularity (dents between foamed particles, holes, etc.), beautiful Δ: slight wrinkles, intergranular but good ×: wrinkles or intergranular , Poor appearance due to sink marks

(Molded product fusion rate)
After a crack having a depth of about 5 mm was made with a knife on the surface of the polypropylene resin mold in the foam molding, the polypropylene resin mold in the mold was cut along the crack, and the fracture surface was observed and all observed. The ratio of the number of broken particles to the number of particles was determined and used as the molded product fusion rate.

  Next, examples of the present invention will be described.

Example 1
For 100 parts by weight of a polypropylene resin (propylene / ethylene random copolymer: ethylene content 2.9% by weight, melt index 7 g / 10 min, melting point 144 ° C.), talc (produced by Hayashi Kasei Co., Ltd.) Talcan powder PK-S) 0.3 parts by weight was added and blended. This was supplied to a 50φ single-screw extruder, melt-kneaded at a die tip temperature of 200 ° C., extruded from a cylindrical die having a diameter of 1.8 mm, cooled with water, cut with a cutter, and cylindrical polypropylene resin particles (1. 8 mg / grain) was obtained.

  100 parts by weight of the obtained polypropylene resin particles were put into a pressure vessel together with 200 parts by weight of water (hardness <0.1 mg / L), 0.7 parts by weight of tribasic calcium phosphate and 0.02 parts by weight of sodium alkanesulfonate. Then, it heated at 151 degreeC, stirring. The pressure vessel internal pressure at this time was about 0.5 MPa (G). Further, air was added over 10 minutes, the pressure in the pressure vessel was adjusted to the pressure shown in Table 1, and the pressure was maintained for 20 minutes. Then, the valve | bulb of the pressure | voltage resistant container lower part was opened, and the dispersion liquid (resin particle | grains and aqueous dispersion medium) was discharge | released to the low pressure container through the orifice which has the opening volume of Table 1, and the polypropylene resin expanded particle was obtained. During discharge, a water vapor inlet was provided immediately after passing through the orifice so that the water vapor was in contact with the discharged water dispersion. The steam blowing temperature at this time was about 98 ° C. During discharge, the pressure inside the pressure vessel was maintained with heated air so that the pressure inside the vessel did not decrease.

  Next, the polypropylene-based resin expanded particles obtained here were washed with acid, dried at 60 ° C. for 6 hours, and then pressurized with air in a pressure-resistant container to obtain an air pressure of about 0.2 MPa. A 200 mm × 50 mm mold was filled, and in-mold foam molding was performed with saturated steam of 0.30 MPa (G) to obtain a polypropylene resin in-mold foam molded body. Table 1 shows the results of the evaluation of the polypropylene resin expanded particles and the polypropylene resin in-mold foam molded product.

（実施例２）
タルクを０．３重量部と吸水性物質としてメラミン０．５重量部をブレンドした以外は実施例１と同様にしてポリプロピレン系樹脂粒子を得た。

(Example 2)
Polypropylene resin particles were obtained in the same manner as in Example 1 except that 0.3 part by weight of talc and 0.5 part by weight of melamine as a water-absorbing substance were blended.

  Further, polypropylene-based resin foamed particles were obtained and foam-molded in the mold in the same manner as in Example 1, except that the pressure-resistant container internal pressure and the orifice having an open volume described in Table 1 were used. Table 1 shows the results of the evaluation of the polypropylene resin expanded particles and the polypropylene resin in-mold foam molded product.

(Example 3)
Polypropylene resin particles were obtained in the same manner as in Example 1 except that 0.1 part by weight of talc and 0.2 part by weight of polyethylene glycol (molecular weight 300) as a water-absorbing substance were blended.

  Next, 100 parts by weight of the obtained polypropylene resin particles were put into a pressure-resistant container together with 200 parts of water, 2.0 parts by weight of tricalcium phosphate and 0.05 parts by weight of sodium alkanesulfonate, and then deaerated and stirred. Then, 4 parts by weight of initial carbon dioxide gas was put in a pressure vessel and heated to 148 ° C. The pressure vessel internal pressure at this time was about 2.3 MPa (G). Further, carbon dioxide gas was added, and the pressure in the pressure vessel was adjusted to the pressure shown in Table 1 and held for 10 minutes. Thereafter, the valve at the lower part of the pressure vessel is opened, and the aqueous dispersion containing the polypropylene resin particles and the aqueous dispersion medium is discharged under atmospheric pressure through the orifice having the opening volume shown in Table 1 to obtain the expanded polypropylene resin particles. Obtained. During discharge, the pressure was maintained with carbon dioxide gas so that the pressure in the container did not decrease.

  Thereafter, in-mold foam molding was performed in the same manner as in Example 1. Table 1 shows the results of the evaluation of the polypropylene resin expanded particles and the polypropylene resin in-mold foam molded product.

Example 4
Polypropylene resin particles were obtained in the same manner as in Example 1 except that 0.1 part by weight of talc and 0.5 part by weight of polyethylene glycol were blended.

  Next, polypropylene resin expanded particles were obtained in the same manner as in Example 3, and molded in-mold. However, the initial carbon dioxide gas is the amount shown in Table 1. The pressure inside the pressure vessel when heated to 148 ° C. is about 2.5 MPa (G). Further, carbon dioxide is added and the pressure inside the pressure vessel is shown in Table 1. Pressure. Table 1 shows the results of the evaluation of the polypropylene resin expanded particles and the polypropylene resin in-mold foam molded product.

(Example 5)
Instead of talc, which is an inorganic compound containing water of crystallization, 0.1 part by weight of kaolin (ASP-400P, Hayashi Kasei Co., Ltd.), which is an inorganic compound of water of crystallization, was used except that blended with 0.5 parts by weight of polyethylene glycol. After obtaining polypropylene resin particles in the same manner as in Example 1, polypropylene resin foam particles and a polypropylene resin in-mold foam molded article were obtained in the same manner as in Example 4. The evaluation results are shown in Table 1.

(Comparative Example 1)
Instead of talc, polypropylene resin particles were obtained in the same manner as in Example 1 except that 1 part by weight of polyvinyl alcohol (PVA205S, manufactured by Kuraray) was blended.

  Next, expanded polypropylene resin particles were obtained in the same manner as in Example 3 except for heating to 150 ° C., and molded in-mold. However, the initial carbon dioxide gas is the amount shown in Table 1, the pressure inside the pressure vessel when heated to 150 ° C. is about 2.6 MPa (G), and carbon dioxide is further added to show the pressure inside the pressure vessel as shown in Table 1. Pressure. Table 1 shows the results of the evaluation of the polypropylene resin expanded particles and the polypropylene resin in-mold foam molded product.

(Comparative Example 2)
Polypropylene resin particles were obtained in the same manner as in Example 1 except that the amounts of talc and melamine added were blended as shown in Table 1.

  Next, expanded polypropylene resin particles were obtained in the same manner as in Example 3 except for heating to 147 ° C., and molded in-mold. However, the initial carbon dioxide gas is the amount shown in Table 1. The pressure inside the pressure vessel when heated to 147 ° C. is 3.0 MPa (G). Pressure was used. Table 1 shows the results of the evaluation of the polypropylene resin expanded particles and the polypropylene resin in-mold foam molded product.

(Comparative Example 3)
In place of talc, which is an inorganic compound containing water of crystallization, 0.3 parts by weight of anhydrous sodium sulfate (anhydrous without water of crystallization: Wako Pure Chemical Reagent) as a foam nucleating agent and 0.5 parts by weight of polyethylene glycol Except that, polypropylene resin particles were obtained in the same manner as in Example 1, and then polypropylene resin foam particles and a polypropylene resin in-mold foam molded article were obtained in the same manner as in Example 4. The evaluation results are shown in Table 1.

It is an example of a DSC curve obtained when the polypropylene resin foamed particles of 1 to 10 mg of the present invention are heated from 40 ° C. to 220 ° C. at a temperature rising rate of 10 ° C./min by a differential scanning calorimeter. A point where the endotherm is the smallest between the two melting peaks of the DSC curve is A, and a tangent line is drawn from the point A to the DSC curve, and among the parts surrounded by the tangent line and the DSC curve, the high temperature side is the high temperature side. The melting peak heat amount Qh, and the low temperature side is the melting peak heat amount Ql on the low temperature side. It is an example of a diaphragm and is a front view of an orifice type diaphragm. The portion other than the shaded portion is the orifice surface, and the orifice sectional area is M. It is an example of a diaphragm and is sectional drawing of an orifice type diaphragm. L other than the shaded portion is the orifice length direction.

Claims (9)

  Polypropylene resin particles containing 0.005 parts by weight or more and 1 part by weight or less of a water-containing inorganic compound, water, an inorganic dispersant, and a dispersion aid are contained in a pressure resistant container with respect to 100 parts by weight of the polypropylene resin. Then, the temperature is raised while stirring and dispersing in the presence of an inorganic foaming agent, and the pressure in the pressure vessel is increased to 0.9 MPa (G) or more and 3.5 MPa (G) or less, and then dispersed in the pressure vessel. A method for producing a polypropylene resin foamed particle, characterized in that the liquid is discharged into a pressure range lower than the internal pressure of the pressure vessel and foamed, the polypropylene resin foamed particle having two melting peaks, Among melting peaks, the melting peak calorie Ql on the low temperature side and the melting peak calorie Qh on the high temperature side calculated from the melting peak calorie Qh Z = Qh / (Ql + Qh) × 100 is 17% or more and 35% Below, the bubble film thickness variation S in the polypropylene resin expanded particles is less than 0.5, the expansion ratio is 2 to 14 times, and the magnification variation R between the polypropylene resin expanded particles is 10% or less. A method for producing expanded polypropylene resin particles.   2. The method for producing expanded polypropylene resin particles according to claim 1, wherein the pressure inside the pressure vessel is increased from 1.4 MPa (G) to 3.0 MPa (G). ^{3. The} method for producing expanded polypropylene resin particles according to claim 1, wherein when the dispersion is discharged and foamed, the dispersion is discharged through a diaphragm having an opening volume of 20 mm ³ or more and 150 mm ³ or less. .   The method for producing expanded polypropylene resin particles according to any one of claims 1 to 3, wherein the high temperature side melting peak ratio Z = Qh / (Ql + Qh) × 100 is 19% or more and 28% or less.   The method for producing expanded polypropylene resin particles according to any one of claims 1 to 4, comprising 0.01 to 3 parts by weight of a water-absorbing substance with respect to 100 parts by weight of the polypropylene resin.   The method for producing expanded polypropylene resin particles according to any one of claims 1 to 5, wherein the water-absorbing substance is polyethylene glycol and / or melamine.   The hardness of water is 0 mg / L or more and 180 mg / L or less, The manufacturing method of the polypropylene resin expanded particle as described in any one of Claims 1-6.   In a polypropylene resin foamed particle comprising 0.005 parts by weight or more and 1 part by weight or less of a crystal water-containing inorganic compound with respect to 100 parts by weight of the polypropylene resin, the polypropylene resin foamed particles have two melting peaks. Among the melting peaks, the high-temperature side melting peak ratio Z = Qh / (Ql + Qh) × 100 calculated from the low-temperature side melting peak heat amount Ql and the high-temperature side melting peak heat amount Qh is 17% or more and 35% or less. The film thickness variation S in the foamed resin particles is less than 0.5, the expansion ratio is 2 to 14 times, and the magnification variation R between the polypropylene resin expanded particles is 10% or less. Expanded polypropylene resin particles.   A polypropylene resin in-mold foam-molded article obtained by filling the polypropylene resin foam particles according to claim 8 in a mold and heating.

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