WO2019172204A1 - Polypropylene resin foamed particle and method of producing same - Google Patents

Abstract

Provided is a method of producing polypropylene resin foamed particles for in-mold foamed molding that has high productivity and in which blocking does not occur outside a pressure resistant vessel when using silicate as a dispersant even if the weight ratios of a polypropylene resin and an aqueous dispersion medium are similar. The polypropylene resin foamed particles without blocking can be obtained by using a polypropylene resin into which a specific polyethylene resin and an amine compound are mixed.

Description

Polypropylene-based resin expanded particles and method for producing the same

The present invention relates to a polypropylene resin expanded particle and a method for producing the same.

A polypropylene resin foam molded body (hereinafter also simply referred to as “in-mold foam molded body”) composed of polypropylene resin foam particles (hereinafter also referred to as “resin foam particles”, “foam particles” or “beads”). Excellent physical properties such as buffering property and heat insulating property. For this reason, polypropylene resin foam moldings are used in various fields such as packaging materials, cushioning materials, heat insulating materials, and building materials. In particular, the in-mold foam molding method for filling a mold with polypropylene resin foam particles and heating them with water vapor or the like to fuse the foam particles together to obtain an in-mold foam molded product of a predetermined shape is a product of various shapes. Since it can be obtained relatively easily, it is used in many applications.

The polypropylene resin expanded particles mainly contain polypropylene resin particles, water as a dispersion medium, an inorganic gas based foaming agent, a dispersing agent and a dispersion aid together in a pressure resistant container, and are dispersed by stirring. After heating and pressurizing the inside of the container, the dispersion liquid in the pressure-resistant container is discharged into a pressure region lower than the pressure in the container to foam the polypropylene resin particles. The dispersant is added to prevent fusion (blocking) between the resin particles in the pressure vessel or between the resin foam particles immediately after being released to the outside of the pressure vessel.

As the dispersing agent, tricalcium phosphate is preferably used (for example, Patent Documents 1 and 2).

Further, in Patent Document 2, a polypropylene resin foam that provides an in-mold foam molded article that takes advantage of the original strength of the base resin without losing physical properties and quality such as fusion and surface properties during in-mold foam molding. For the purpose of providing a method for producing particles, a method of using polypropylene resin particles comprising a polypropylene resin composition in which a specific polyethylene resin is mixed with a polypropylene resin is disclosed.

There is a method of using a viscosity mineral such as silicate that is difficult to be detached from the surface of the expanded particles as a dispersant (for example, Patent Document 3). Of the clay minerals, kaolin is preferably used.

Patent Document 3 discloses a method for producing expanded polypropylene resin particles containing an NH type hindered amine compound. This document describes an improvement in the blocking prevention effect at the time of foaming by an inorganic dispersant by containing a specific amount of an NH type hindered amine compound.

JP 2017-179281 A International Publication Number WO2017 / 090432 JP-A-11-147972

The object of one embodiment of the present invention is that when silicate is used as a dispersant, blocking outside the pressure vessel does not occur even if the weight ratio between the polypropylene resin particles and the aqueous dispersion medium is close, That is, an object of the present invention is to provide a method for producing polypropylene resin expanded particles for in-mold foam molding with high productivity.

As a result of intensive studies, the present inventors have used a polypropylene resin in which a specific polyethylene resin and an amine compound are mixed with the polypropylene resin, so that the weight ratio of the polypropylene resin particles to the aqueous dispersion medium is close. In addition, the present inventors have found that polypropylene-based resin expanded particles having no blocking can be obtained even under conditions in which a small amount of silicate is used as a dispersant, that is, conditions in which expanded particles are likely to be blocked outside the pressure vessel. That is, one embodiment of the present invention has the following configuration.

A method for producing polypropylene resin foam particles according to an embodiment of the present invention includes a polypropylene resin particle, an inorganic gas foaming agent, and an inorganic dispersant silicate in an aqueous dispersion medium in a sealed container. A step of dispersing in, forming a dispersion, heating the inside of the closed container to a temperature equal to or higher than the softening temperature of the polypropylene resin particles, and pressurizing the inside of the closed container, and a pressure lower than the internal pressure of the closed container A step of obtaining polypropylene-based resin expanded particles by releasing the dispersion into the region, wherein the polypropylene-based resin particles have a polypropylene-based resin (X) of 85 to 99% by weight and a density of 0.945 g / cm ³ or more. Polypropylene resin (Z) consisting of 1 to 15% by weight of polyethylene resin (Y) of the above (the total of (X) and (Y) is 100% by weight); 0.01 parts by weight or more and 1 part by weight or less of an amine compound with respect to 100 parts by weight of the resin (Z), and the dispersion is (i) 0 with respect to 100 parts by weight of the polypropylene resin particles. .05 parts by weight or more and 0.4 parts by weight or less of the silicate, and (ii) 100 parts by weight or more and 250 parts by weight or less of the aqueous dispersion medium.

Furthermore, in the polypropylene resin expanded particles according to an embodiment of the present invention, the polypropylene resin expanded particles include a polypropylene resin, and the polypropylene resin includes 85 to 99% by weight of the polypropylene resin (X) and Polypropylene resin (Z) consisting of 1 to 15% by weight of a polyethylene resin (Y) having a density of 0.945 g / cm ³ or more [the total of (X) and (Y) is 100% by weight], and the polypropylene resin 0.01 parts by weight or more and 1 part by weight or less of an amine compound with respect to 100 parts by weight of the resin (Z), and present on the surface of the expanded polypropylene resin particles with respect to 100 parts by weight of the polypropylene resin. The amount of silicate is more than 0 parts by weight and not more than 0.20 parts by weight.

One embodiment of the present invention has an effect that it is possible to provide a highly productive method for producing expanded polypropylene resin particles for in-mold foam molding.

One embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, and various modifications can be made within the scope shown in the claims. Further, embodiments or examples obtained by appropriately combining technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment. In addition, all the academic literatures and patent literatures described in this specification are used as references in this specification.

Unless otherwise specified in this specification, “A to B” representing a numerical range is intended to be “A or more (including A and greater than A) and B or less (including B and less than B)”.

Additionally, unless otherwise stated herein, as constituent units, a constituent unit derived from X ₁ monomer, a constitutional unit derived from the X ₂ monomer, ..., and X _n monomer (n is And an integer of 2 or more) is also referred to as “X ₁ / X ₂ /... / X _n copolymer”. The X ₁ / X ₂ /... / X _n copolymer is not particularly limited unless otherwise specified, and may be a random copolymer or a block copolymer. It may be a graft copolymer.

[1. Technical idea of one embodiment of the present invention]
As a result of intensive studies by the present inventors, it has been found that Patent Documents 1 to 3 described above have room for improvement or problems as described below.

In the techniques described in Patent Documents 1 and 2, tricalcium phosphate is used as a dispersant. The resin foam particles obtained by using tricalcium phosphate are separated from the resin foam particles by the tricalcium phosphate adhering to the surface of the resin foam particles during in-mold foam molding using the resin foam particles. The inventor has uniquely found that the metal deposits on the mold.

In the technique described in Patent Document 3, silicate is used. The case where silicate is used as a dispersant will be described. In this case, in order to ensure good productivity under conditions where the weight ratio between the polypropylene resin particles and the aqueous dispersion medium is close, if a large amount of silicate is not added, blocking immediately after release outside the pressure vessel Can not prevent. Also, polypropylene resin expanded particles obtained by using a large amount of silicate can be obtained although no silicate is deposited on the mold during in-mold expansion molding using the expanded particles. There existed a subject that the tendency for the melt | fusion property of an in-mold foam molding to deteriorate was seen. In addition, when a large amount of silicate is used, the treatment of waste water containing a large amount of silicate is costly and there is a problem in productivity.

In the technique described in Patent Document 3, the effect of preventing blocking was insufficient under conditions where the weight ratio between the polypropylene resin and the aqueous dispersion medium was close and blocking was likely to occur. That is, in the technique described in Patent Document 3, when the weight ratio between the polypropylene resin and the aqueous dispersion medium is close, a large amount of kaolin (silicic acid), which is an inorganic dispersant, is used to prevent blocking in the production process of the single-stage expanded particles. Salt) had to be added. However, the present inventors have uniquely found that the amount of kaolin (silicate) adhering to the surface of the expanded polypropylene resin particles increases, and as a result, the fusion property at the time of in-mold foam molding deteriorates.

In the production of polypropylene resin particles, a case where the amount of a dispersion medium (for example, an aqueous dispersion medium) is large relative to the polypropylene resin particles will be described. In this case, polypropylene resin particles (raw materials) that can be supplied into containers having a certain volume (for example, sealed containers and pressure-resistant containers) are reduced, so that polypropylene can be produced per batch cycle (per production). Resin-based foamed particles are reduced. Therefore, it can be said that the production method is inferior in productivity as the amount of the dispersion medium with respect to the polypropylene resin particles is larger.

Here, the smaller the amount of the aqueous dispersion medium with respect to the polypropylene resin particles, the easier the blocking outside the sealed container occurs. Specifically, in the production of polypropylene resin particles, if the weight ratio between the polypropylene resin particles and the aqueous dispersion medium is close, blocking outside the container (such as a sealed container and a pressure-resistant container) tends to occur.

The object of one embodiment of the present invention is to (1) have high productivity by reducing the amount of aqueous dispersion medium relative to polypropylene resin particles, and (2) the weight of polypropylene resin particles and aqueous dispersion medium. An object of the present invention is to provide a method for producing polypropylene resin foamed particles for in-mold foam molding, in which blocking outside the container is prevented even when the ratio is close.

[2. Production method of expanded polypropylene resin particles]
A method for producing polypropylene resin foam particles according to an embodiment of the present invention includes a polypropylene resin particle, an inorganic gas foaming agent, and an inorganic dispersant silicate in an aqueous dispersion medium in a sealed container. A step of dispersing in, forming a dispersion, heating the inside of the closed container to a temperature equal to or higher than the softening temperature of the polypropylene resin particles, and pressurizing the inside of the closed container, and a pressure lower than the internal pressure of the closed container A step of obtaining polypropylene-based resin expanded particles by releasing the dispersion into the region, wherein the polypropylene-based resin particles have a polypropylene-based resin (X) of 85 to 99% by weight and a density of 0.945 g / cm ³ or more. Polypropylene resin (Z) consisting of 1 to 15% by weight of polyethylene resin (Y) of the above (the total of (X) and (Y) is 100% by weight); 0.01 parts by weight or more and 1 part by weight or less of an amine compound with respect to 100 parts by weight of the resin (Z), and the dispersion is (i) 0 with respect to 100 parts by weight of the polypropylene resin particles. .05 parts by weight or more and 0.4 parts by weight or less of the silicate, and (ii) 100 parts by weight or more and 250 parts by weight or less of the aqueous dispersion medium.

Since the method for producing expanded polypropylene resin particles according to an embodiment of the present invention has the above-described configuration, the aqueous dispersion medium for the polypropylene resin particles is compared with the conventional technique using silicate as an inorganic dispersant. Even when the amount is small, blocking outside the sealed container can be prevented. In other words, the method for producing expanded polypropylene resin particles according to an embodiment of the present invention can provide a method for producing expanded polypropylene resin particles for in-mold foam molding with high productivity.

(2-1. Polypropylene resin particles)
(Polypropylene resin (X))
The “polypropylene-based resin (X)” used in one embodiment of the present invention has a propylene-derived component as a main copolymer component, and includes a polypropylene homopolymer, an ethylene / propylene random copolymer, butene-1 / Propylene random copolymer, ethylene / butene-1 / propylene random copolymer, ethylene / propylene block copolymer, butene-1 / propylene block copolymer, propylene / chlorinated vinyl copolymer, propylene / maleic anhydride Examples thereof include copolymers and blends thereof. Among these, ethylene / propylene random copolymer, butene-1 / propylene random copolymer or ethylene / butene-1 / propylene random copolymer has good foamability and good moldability. To preferred. In this specification, “butene-1” may also be expressed as “1-butene”. Here, “the component derived from propylene is the main copolymer component” means that 50% or more of all copolymer components (also referred to as constituent components) in the copolymer are components derived from propylene. .

As the polypropylene resin (X), the content of the comonomer-derived component, which is a copolymer component other than the propylene-derived component, is 0.2 wt% to 10 wt% in 100 wt% of each copolymer. Are preferably used. As a polypropylene resin (X), only 1 type may be used and 2 or more types may be used together.

The polymerization catalyst for synthesizing the polypropylene resin (X) used in one embodiment of the present invention is not particularly limited, and a Ziegler catalyst, a metallocene catalyst, or the like can be used.

The melting point of the polypropylene resin (X) used in one embodiment of the present invention is not particularly limited, but is preferably 130 ° C. or higher and 160 ° C. or lower, more preferably 140 ° C. or higher and 155 ° C. or lower. When the melting point of the polypropylene resin (X) is in the above-described range, there is a tendency that an in-mold foam molded article having an excellent balance between mechanical strength and surface appearance tends to be obtained. In this specification, the melting point of the polypropylene resin (X) is a value obtained as a result of differential scanning calorimetry (DSC) performed using a differential scanning calorimeter. The specific operation procedure is as follows: (1) After 5-6 mg of polypropylene resin is melted by raising the temperature from 40 ° C. to 220 ° C. at a temperature raising rate of 10 ° C./min; (2) 10 After crystallizing by lowering the temperature from 220 ° C. to 40 ° C. at a temperature lowering rate of 3 ° C./min; The temperature of the peak (melting peak) of the DSC curve obtained at the second temperature increase (that is, (3)) can be determined as the melting point.

The melt flow rate (hereinafter sometimes referred to as MFR) of the polypropylene resin (X) used in one embodiment of the present invention is preferably 3.0 g / 10 min or more and 12 g / 10 min or less, more Preferably they are 5.0 g / 10min or more and 9.0 g / 10min or less. When the melt flow rate of the polypropylene-based resin is in the above-described range, there is a tendency that an in-mold foam-molded article with little deformation and excellent surface beauty is easily obtained. The MFR measurement in one embodiment of the present invention uses an MFR measuring instrument described in JIS K7210, with an orifice of 2.0959 ± 0.005 mmφ, an orifice length of 8.000 ± 0.025 mm, a load of 2160 g, and 230 ± 0.2. It is a value when measured under the condition of ° C.

(Polyethylene resin (Y))
The density of the polyethylene resin (Y) in one embodiment of the present invention is 0.945 g / cm ³ or more, preferably 0.960 g / cm ³ or more. When the density of the polyethylene resin (Y) is less than 0.945 g / cm ^{3, the} effect of suppressing the blocking of the polypropylene resin foamed particles is not sufficiently exhibited. There is no upper limit to the density of the polyethylene resin (Y), but the density of the polyethylene resin depends on the crystallinity, and generally it is about 0.970 g / cm ³ even if the crystallinity is increased. Limit.

The polyethylene resin (Y) used in one embodiment of the present invention may contain a component derived from a comonomer copolymerizable with ethylene in addition to the component derived from ethylene as long as it has a predetermined density.

As the comonomer copolymerizable with ethylene, an α-olefin having 3 to 18 carbon atoms can be used. Examples of the α-olefin having 3 to 18 carbon atoms include propene, 1-butene, 1-pentene, 1-hexene, 3,3-dimethyl / 1-butene, 4-methyl / 1-pentene, 4, Examples thereof include 4-dimethyl / 1-pentene and 1-octene, and these may be used alone or in combination of two or more.

The melting point of the polyethylene resin (Y) used in one embodiment of the present invention is not particularly limited, but those having a temperature of 125 ° C. or higher and 140 ° C. or lower are preferably used. In this specification, the melting point of the polyethylene resin (Y) is measured by the same method (DSC) as the melting point of the polypropylene resin (X) except that a polyethylene resin is used instead of the polypropylene resin. The obtained value.

The MFR of the polyethylene resin (Y) used in one embodiment of the present invention is not particularly limited, but is preferably the same as that of the polypropylene resin (X). In the present specification, the MFR of the polyethylene resin (Y) is a value obtained by measurement by the same method as the MFR of the polypropylene resin (X).

(Polypropylene resin (Z))
In the polypropylene resin (Z) used in an embodiment of the present invention, the mixing ratio of the polypropylene resin (X) and the polyethylene resin (Y) is 100% by weight of the polypropylene resin (Z) [in other words, The total of (X) and (Y) is 100 wt%], and the polyethylene resin (X) is 85 wt% or more and 99 wt% or less, and the polyethylene resin (Y) is 1 wt% or more and 15 wt% or less. . Furthermore, 90 to 95 weight% of polypropylene resin (X) and 5 to 10 weight% of polyethylene resin (Y) are preferable. The “mixing ratio” can be said to be a “content ratio”.

The mixing ratio of the polypropylene resin (X) and the polyethylene resin (Y) is more than 99% by weight of the polypropylene resin (X) with respect to 100% by weight of the polypropylene resin (Z), and the polyethylene resin (Y). If it is less than 1% by weight, the effect of inhibiting blocking is not sufficiently exhibited in the production of polypropylene resin expanded particles. On the other hand, the mixing ratio of the polypropylene resin (X) and the polyethylene resin (Y) is less than 85% by weight of the polypropylene resin (X) with respect to 100% by weight of the polypropylene resin (Z), and the polyethylene resin ( Y) If it exceeds 15% by weight, the elongation of the polypropylene resin foamed particles during in-mold molding may be reduced, and the surface appearance may be deteriorated.

The MFR of the polypropylene resin (Z) used in one embodiment of the present invention is preferably 3.0 g / 10 min or more and 12 g / 10 min or less, more preferably 5.0 g / 10 min or more and 9.0 g / min. 10 minutes or less. When the melt flow rate of the polypropylene-based resin (Z) is in the above-described range, there is a tendency that an in-mold foam-molded product with little deformation and excellent surface beauty is easily obtained. In the present specification, the MFR of the polypropylene resin (Z) is a value obtained by measurement by the same method as the MFR of the polypropylene resin (X).

(Amine compounds)
The “amine compound” used in one embodiment of the present invention is not particularly limited as long as it is available. For example, a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium salt. Hindered amines, and the like. These may be used alone or in combination of two or more. In particular, hindered amine is preferable because it has an effect as an ultraviolet absorber that enhances the light resistance of the foamed resin particles and the in-mold foam molded article. Specifically, condensation of bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol Products, a mixture of stearyl diethanolamine monostearate and stearyl diethanolamine, and alkyl (C ₁₆ -C ₁₈ ) trimethylammonium chloride. “Alkyl (C ₁₆ -C ₁₈ )” is intended to be alkyl having 16 to 18 carbon atoms.

The content of the amine compound according to one embodiment of the present invention is 0.01 part by weight or more and 1 part by weight or less with respect to 100 parts by weight of the polypropylene resin (Z). More preferably, it is 0.1 parts by weight or more and 0.5 parts by weight or less. When the content of the amine compound is less than 0.01 parts by weight with respect to 100 parts by weight of the polypropylene resin (Z), the dispersion stability during the production of the expanded polypropylene resin particles is deteriorated, and the expanded particles cannot be obtained. . Even if the amount of the amine compound is more than 1 part by weight with respect to 100 parts by weight of the polypropylene resin (Z), there is no difference in the effect of suppressing blocking outside the pressure vessel (sealed container). This is disadvantageous in terms of production cost.

(2-2. Method for producing polypropylene resin particles)
The method for producing expanded polypropylene resin particles according to an embodiment of the present invention may further include a step of producing polypropylene resin particles.

Examples of the method for producing polypropylene resin particles according to an embodiment of the present invention include the following methods.

First, a mixture of a polypropylene resin (X), a polyethylene resin (Y), an amine compound, and, if necessary, other additives is mixed by a mixing method such as a dry blend method or a master batch method.

Next, after the obtained mixture is melt-kneaded using an extruder, kneader, Banbury mixer (registered trademark), and a roll, the obtained melt-kneaded product is shredded using a cutter, a pelletizer, and the like. By setting the particle shape, polypropylene resin particles can be obtained.

(2-3. Other additives)
The polypropylene resin particles according to an embodiment of the present invention may contain a cell nucleating agent, a hydrophilic compound, an antioxidant, an antistatic agent, a flame retardant, and the like as other additives as necessary. Can do. Such other additives may be added to other resins in a high concentration in advance to form a master batch, and this master batch resin may be added to the polypropylene resin (Z). The resin used for such a masterbatch resin is preferably a polyolefin resin, and more preferably a masterbatch using a polypropylene resin.

Examples of the cell nucleating agent used as needed in one embodiment of the present invention include inorganic nucleating agents such as talc, calcium stearate, calcium carbonate, silica, kaolin, titanium oxide, bentonite, and barium sulfate. Generally used. These may be used alone or in combination of two or more. Among these cell nucleating agents, a cell having uniform talc can be obtained, which is preferable. The content of the cell nucleating agent may be appropriately adjusted according to the intended cell diameter and the type of cell nucleating agent to be used. As content of a cell nucleating agent, 0.001 weight part or more and 2 weight part or less are preferable with respect to 100 weight part of polypropylene-type resin (Z), for example, More preferably, 0.01 part or more and 1 weight part are preferable. It is as follows. When the content of the cell nucleating agent is within the range, cells having a uniform size suitable for expanded particles can be easily obtained. Here, the “cell” may be referred to as “bubble”.

In one embodiment of the present invention, a hydrophilic compound is used as necessary. When the polypropylene resin particles contain a hydrophilic compound, water contained in the aqueous dispersion medium also acts as a foaming agent, and this water is preferable because it contributes to an improvement in the expansion ratio. Specific examples of the hydrophilic compound used in one embodiment of the present invention include, but are not limited to, glycerin, polyethylene glycol, polypropylene glycol, and melamine. Particularly preferred are glycerin and polyethylene glycol.

In one embodiment of the present invention, the weight per polypropylene resin particle (hereinafter also referred to as “grain weight”) is preferably 0.2 mg or more and 10 mg or less, and more preferably 0.5 mg or more and 6.0 mg or less. . When the weight per one polypropylene-based resin particle is in the range, the dimensions and filling properties of the obtained in-mold foam molded product are likely to be good. In this specification, the weight per one polypropylene resin particle is an average resin particle weight obtained from 100 particles of randomly selected polypropylene resin particles.

Usually, the composition and particle weight of the polypropylene resin particles are hardly changed even after the foaming process and the in-mold foam molding process, and the same properties are exhibited even when the foam particles and the in-mold foam molding are remelted. Therefore, by analyzing the foamed particles and the in-mold foamed molded product, the composition and particle weight of the used polypropylene resin particles can be determined.

(2-4. Production method of expanded polypropylene resin particles)
In one embodiment of the present invention, polypropylene-based resin expanded particles can be produced using the polypropylene-based resin particles thus obtained. Polypropylene resin foamed particles can also be produced using polypropylene resin particles produced by methods other than the production methods described above or commercially available polypropylene resin particles.

Examples of the foaming agent in one embodiment of the present invention include “inorganic gas-based foaming agent” such as water, carbon dioxide, nitrogen, air (that is, a mixture of oxygen, nitrogen and carbon dioxide). As the inorganic gas-based foaming agent, carbon dioxide is preferably used. By using carbon dioxide among inorganic gas-based foaming agents having a small environmental load, a polypropylene resin in-mold foam-molded article having a good appearance can be obtained. Hereinafter, the “inorganic gas-based foaming agent” may be simply referred to as “foaming agent”.

As a foaming agent used in an embodiment of the present invention, an inorganic gas such as air, nitrogen, oxygen or the like may be used in combination with carbon dioxide as long as the quality of the obtained foamed polypropylene resin mold is not impaired. . For example, air remaining in a sealed container used for foaming has little influence on the quality of the obtained polypropylene-based resin-molded foam-molded product, and may be used together with carbon dioxide.

The method for producing the expanded polypropylene resin particles in one embodiment of the present invention may be the following method. That is, (1) a step of dispersing polypropylene resin particles and an inorganic dispersant silicate in an aqueous dispersion medium in an airtight container to obtain a dispersion; (2) carbon dioxide as a foaming agent in the airtight container. (2) a step of impregnating polypropylene resin particles with the carbon dioxide while adding pressure to the inside of the sealed container by adding; (3) a step of heating the inside of the sealed container to a temperature equal to or higher than the softening temperature of the polypropylene resin particles; 4) A method comprising a step of obtaining polypropylene-based resin expanded particles by releasing a dispersion containing polypropylene-based resin particles into a pressure region lower than the internal pressure of the sealed container. Such processes (1) to (4) may be collectively referred to as a “single-stage foaming process”, and the polypropylene resin foam particles obtained in the “single-stage foaming process” may be referred to as “single-stage foam particles”. is there.

In the production method according to one embodiment of the present invention, “above the softening temperature of polypropylene resin particles” means that the melting point of the polypropylene resin particles according to one embodiment of the present invention is −10 ° C. or more.

The heating temperature in the closed container (in other words, the foaming temperature) is not particularly limited, and may be any temperature above the softening temperature of the polypropylene resin particles. For example, the melting point of the polypropylene resin (Z) used is −10 ° C. or more. The melting point is preferably 10 ° C. or lower.

In this specification, the melting point of the polypropylene resin particles is obtained by measuring by the same method (DSC) as the melting point of the polypropylene resin (X) except that polypropylene resin particles are used instead of the polypropylene resin. Value.

In the present specification, the melting point of the polypropylene resin (Z) is a value obtained by measurement by the same method (DSC) as the melting point of the polypropylene resin (X).

The pressure for impregnating the foaming agent in the closed container in one embodiment of the present invention (in other words, foaming pressure) is preferably about 1.5 MPa (gauge pressure) or more and 5.0 MPa (gauge pressure) or less, More preferably, the pressure is 1.5 MPa (gauge pressure) or more and 3.5 MPa (gauge pressure) or less. When the said foaming pressure exists in the said range, what has the favorable external appearance of the in-mold foaming molding obtained is easy to be obtained.

In one embodiment of the present invention, the dispersion liquid containing expanded polypropylene resin particles heated and pressurized in a sealed container is released into a cylindrical container, piping, a sealed tank or the like, preferably released into the cylindrical container. Is done. The cylindrical container may be referred to as a “foamed cylinder”.

In one embodiment of the present invention, for the purpose of adjusting the expansion ratio, the temperature of the atmosphere of the foam cylinder from which the dispersion is discharged may be adjusted to about room temperature to about 110 ° C. In particular, in order to obtain expanded particles with a high expansion ratio, it is desirable to set the temperature of the atmosphere of the expanded cylinder from which the dispersion is discharged to about 100 ° C. with steam or the like. Further, at this time, when the manufacturing method according to the embodiment of the present invention is not used, blocking in the foamed cylinder is more likely to occur as the temperature of the atmosphere of the foamed cylinder from which the dispersion is discharged is higher. However, when the manufacturing method according to an embodiment of the present invention is used, there is an advantage that blocking does not occur in the foam cylinder even when the temperature of the atmosphere of the foam cylinder that discharges the dispersion is high.

Specific examples of the “one-stage foaming step”, which is an example of a method for producing polypropylene-based resin foam particles in one embodiment of the present invention, include the following methods.

(I) After the polypropylene resin particles, the aqueous dispersion medium, the silicate which is an inorganic dispersant, etc. are charged into the sealed container, the inside of the sealed container is evacuated as necessary; (ii) Next, the inside of the sealed container Carbon dioxide is introduced as a foaming agent into a dispersion; (iii) The inside of the sealed container is then heated to a temperature higher than the softening temperature of the polypropylene resin; (iv) The pressure in the sealed container is about 1. The amount of carbon dioxide as a blowing agent is adjusted so as to increase from 5 MPa (gauge pressure) to 5 MPa (gauge pressure); (v) if necessary, (vi) after heating the sealed container, (V-ii) Carbon dioxide as a foaming agent may be added to the sealed container to adjust the inside of the sealed container to a desired foaming pressure; (vi) Then, the sealed container is maintained so as to maintain the foaming temperature. Adjust the temperature of However, the foaming pressure and foaming temperature are maintained for more than 0 minutes and not more than 120 minutes; (vii) Next, the pressure is adjusted to 80 ° C. or more and 110 ° C. or less with water vapor or the like and lower than the internal pressure of the sealed container The dispersion is discharged into a foamed cylinder having a region (usually atmospheric pressure) to obtain polypropylene-based resin foamed particles.

As a method of introducing the foaming agent different from the above in one embodiment of the present invention, the following methods (1) to (3) may be mentioned.

(1) A foaming agent is prepared by charging polypropylene resin particles, an aqueous dispersion medium, a silicate which is an inorganic dispersant, etc. into a sealed container, and simultaneously charging solid carbon dioxide as dry ice into the sealed container. In a closed container.

(2) After charging polypropylene resin particles, aqueous dispersion medium, inorganic dispersant silicate, etc. in a sealed container, and vacuuming the sealed container as needed, the polypropylene resin A method of introducing a foaming agent into a sealed container while heating the sealed container to a temperature equal to or higher than the softening temperature.

(3) After charging polypropylene resin particles, aqueous dispersion medium, silicate which is an inorganic dispersant, etc. into the sealed container, after evacuating the inside of the sealed container, if necessary, to near the foaming temperature A method in which the inside of the sealed container is heated and the foaming agent is introduced into the sealed container at this point.

In addition, as a method of increasing the expansion ratio of the polypropylene resin expanded particles, for example, a method of increasing the internal pressure in the sealed container, a method of increasing the pressure release speed, a method of increasing the temperature in the sealed container before discharge, As described above, there is a method of increasing the temperature of the atmosphere of the foamed cylinder from which the dispersion is discharged.

As the aqueous dispersion medium used in one embodiment of the present invention, it is preferable to use only water, but a dispersion medium in which methanol, ethanol, ethylene glycol, glycerin or the like is added to water can also be used.

The sealed container used in one embodiment of the present invention is not particularly limited as long as it can withstand the pressure in the container and the temperature in the container in the production process of the expanded particles. Examples of the sealed container include an autoclave-type pressure-resistant container that can be sealed.

In the method for producing polypropylene-based expanded particles according to an embodiment of the present invention, the fusion of the polypropylene-based resin particles in the sealed container and in the expanded cylinder after discharging the dispersion liquid from the sealed container (pressure container) to the foamed cylinder In order to prevent (blocking), it is preferable to use a silicate which is an inorganic dispersant in an aqueous dispersion medium. The “fusion” is sometimes referred to as “fusion”.

Specific examples of “silicates” that are inorganic dispersants according to an embodiment of the present invention include clay minerals such as kaolin, montmorillonite, talc, and sericite. These inorganic dispersants may be used alone or in combination of two or more. Of these inorganic dispersants, it is more preferable to use at least kaolin.

In one embodiment of the present invention, the amount (content) of the silicate that is an inorganic dispersant in the dispersion is 0.05 parts by weight or more and 0.4 parts by weight with respect to 100 parts by weight of the polypropylene resin particles. Parts by weight or less, more preferably 0.1 parts by weight or more and 0.2 parts by weight or less. When the amount of the silicate that is an inorganic dispersant is less than 0.05 parts by weight, the effect of preventing blocking in the foamed cylinder is sufficient even if the polypropylene resin particles according to one embodiment of the present invention are used. If it exceeds 0.4 parts by weight, blocking in the foamed cylinder can be suppressed, but the fusing property at the time of in-mold foam molding deteriorates.

In the method for producing polypropylene-based expanded particles in one embodiment of the present invention, it is preferable to use a dispersion aid together with the inorganic dispersant described above.

Examples of the “dispersion aid” used in one embodiment of the present invention include an anionic surfactant. Specific examples of the anionic surfactant include sodium dodecylbenzene sulfonate, sodium alkane sulfonate, sodium alkyl sulfonate, sodium alkyl diphenyl ether disulfonate, sodium α-olefin sulfonate, and the like. It is not limited.

These dispersion aids may be used alone or in combination of two or more. In one embodiment of the present invention, it is more preferable to use at least sodium dodecylbenzenesulfonate.

When the inorganic dispersant and the dispersion aid are used in combination, it is preferable to use kaolin as the inorganic dispersant and sodium dodecylbenzenesulfonate as the dispersion aid.

In one embodiment of the present invention, the amount (content) of the dispersion aid used in the dispersion is 0.002 to 0.2 parts by weight of the dispersion aid with respect to 100 parts by weight of the polypropylene resin particles. preferable.

As a preferable aspect of the method for producing polypropylene-based expanded particles in one embodiment of the present invention, in order to ensure high productivity of the polypropylene-based expanded resin particles, the weight ratio between the polypropylene-based resin particles and the aqueous dispersion medium is close. There are some. The weight ratio between the polypropylene resin particles and the aqueous dispersion medium is directly related to the production amount of the polypropylene resin foam particles obtained per batch.

The dispersion according to an embodiment of the present invention is 100 parts by weight or more and 250 parts by weight or less of an aqueous dispersion medium, preferably 100 parts by weight or more and 200 parts by weight or less of an aqueous dispersion medium, with respect to 100 parts by weight of polypropylene resin particles, More preferably, it contains 130 parts by weight or more and 200 parts by weight or less of an aqueous dispersion medium. The dispersion according to an embodiment of the present invention contains 230 parts by weight or less, 190 parts by weight or less, 150 parts by weight or less, or 130 parts by weight or less of an aqueous dispersion medium with respect to 100 parts by weight of the polypropylene resin particles. Also good. The dispersion according to an embodiment of the present invention may contain 150 parts by weight or more, 180 parts by weight or more, or 200 parts by weight or more of an aqueous dispersion medium with respect to 100 parts by weight of the polypropylene resin particles. In one embodiment of the present invention, it can be said that the amount of the aqueous dispersion medium used in the dispersion is from 100 parts by weight to 250 parts by weight with respect to 100 parts by weight of the polypropylene resin particles. When the amount of the aqueous dispersion medium used is less than 100 parts by weight, even if 0.4 part by weight of the silicate that is the dispersant is added, the dispersion stability of the polypropylene resin particles in the pressure vessel tends to deteriorate, When the amount exceeds 250 parts by weight, which tends to cause blocking in the foamed cylinder, the productivity of the polypropylene resin foamed particles per batch is lowered, which is not preferable.

In one embodiment of the present invention, the single-stage expanded particles are impregnated with an inorganic gas-based foaming agent (for example, air, nitrogen, carbon dioxide, etc.), an internal pressure is applied to the single-stage expanded particles, By bringing the water vapor and the first-stage expanded particles into contact with each other, it is possible to obtain polypropylene-based resin expanded particles having an expansion ratio improved compared to the first-stage expanded particles. In this way, the foaming process in which the polypropylene resin foamed particles (single-stage foamed particles) are further foamed to obtain polypropylene-based resin foamed particles having a higher expansion ratio may be referred to as a “two-stage foaming process”. Polypropylene resin foam particles obtained through such a two-stage foaming process may be referred to as “two-stage foam particles”.

The internal pressure of the inorganic gas-based foaming agent impregnated in the first-stage expanded particles is desirably changed as appropriate in consideration of the expansion ratio of the second-stage expanded particles, but is 0.12 MPa (absolute pressure) or more. The pressure is preferably 6 MPa (absolute pressure) or less.

In the two-stage foaming process, it is desirable that the pressure of water vapor brought into contact with the first-stage foamed particles is appropriately changed in consideration of the expansion ratio of the second-stage foamed particles. The water vapor pressure is preferably adjusted to 0.02 MPa (gauge pressure) or more and 0.25 MPa (gauge pressure) or less, and can be adjusted to 0.03 MPa (gauge pressure) or more and 0.15 MPa (gauge pressure) or less. More preferred. In the two-stage foaming process, the higher the water vapor pressure, the more easily the polypropylene resin foam particles are blocked.

The expansion ratio of the expanded polypropylene resin particles of the present invention obtained by the method for producing expanded polypropylene particles according to an embodiment of the present invention is not particularly limited, and may be adjusted as necessary. From the viewpoint of mechanical strength, it is preferably 3 to 50 times, more preferably 5 to 45 times. Here, the expansion ratio of the polypropylene resin expanded particles is a value calculated by the method described in the examples.

The surface of the polypropylene resin foam particles obtained by the method for producing polypropylene foam particles according to one embodiment of the present invention is always attached with silicate, and even if washed, it is difficult to remove completely. It is.

In one embodiment of the present invention, the amount of silicate (that is, adhering silicate) present on the surface of the expanded polypropylene resin particle is more than 0 parts by weight with respect to 100 parts by weight of the polypropylene resin, and 0.20. It is preferable that it is below the weight part. Furthermore, the amount of silicate present on the surface of the expanded particles with respect to 100 parts by weight of the polypropylene resin is more preferably 0.020 parts by weight or more and 0.20 parts by weight or less, and 0.03 parts by weight or more and 0 or less. Most preferably, it is 10 parts by weight or less. When the amount of silicate adhering to the surface of the expanded particles is 0 part by weight, that is, when no silicate is used, blocking occurs when the dispersion containing the expanded particles is discharged into the expanded cylinder. Therefore, it is not preferable. In the case of 0.020 part by weight or more, blocking in the two-stage foaming step can be sufficiently prevented, and in the case of 0.20 part by weight or less, there is an advantage that fusion at the time of in-mold foam molding is difficult to deteriorate. The amount of silicate present on the surface of the polypropylene resin expanded particles can be adjusted by the amount of silicate used as the inorganic dispersant in the one-stage foaming step.

The average cell diameter of the expanded polypropylene resin particles obtained by the method for producing expanded polypropylene resin particles according to an embodiment of the present invention is preferably 100 μm or more and 500 μm or less, and more preferably 120 μm or more and 400 μm or less. preferable. When the average cell diameter of the obtained polypropylene resin foamed particles is within this range, the appearance of the polypropylene resin in-mold foam molded product obtained using the polypropylene resin foamed particles tends to be good.

Here, the average cell diameter of the expanded polypropylene resin particles is a value measured by the method described in Examples.

In the polypropylene resin expanded particles produced using the polypropylene resin particles, the structure of the polypropylene resin particles changes, but the composition of the polypropylene resin particles does not change. In addition, in a polypropylene resin-in-mold foam-molded article produced using polypropylene resin foam particles produced using polypropylene resin particles, the structure of the polypropylene resin foam particles changes, but the polypropylene resin foam The composition of the particles does not change. Therefore,
(I) The content, melting point, or MFR value of the component derived from the comomer obtained by analyzing the expanded polypropylene resin particles or the expanded foam in the polypropylene resin mold, respectively, is the polypropylene resin that is the raw material thereof. It can be regarded as the content, melting point, or MFR value of the comomer-derived component of the particle,
(Ii) By analyzing the polypropylene resin foamed particles or the polypropylene resin in-mold foam molded product, the polypropylene resin (X) in the polypropylene resin (Z) contained in the polypropylene resin particles that are the raw materials thereof, and The mixing ratio with the polyethylene resin (Y) can be obtained when the types of the polypropylene resin (X) and the polyethylene resin (Y) contained in the polypropylene resin (Z) are known. it can.

Further, the content, melting point, or MFR value of the component derived from the comomer of the polypropylene resin particles is the content, melting point, or component of the comomer derived component of the polypropylene resin (Z) contained in the polypropylene resin particle, respectively. It can also be said to be the value of MFR.

In the present specification, the melting point of the polypropylene resin expanded particles or the polypropylene resin molded in-mold molded product is that the polypropylene resin expanded particles or the polypropylene resin molded in-mold molded product are used in place of the polypropylene resin, respectively. The value obtained by measurement by the same method (DSC) as the melting point of the polypropylene resin (X).

The MFR of the polypropylene resin expanded particles can be measured as follows: (A1) The polypropylene resin expanded particles are left in an oven that can be decompressed so that the polypropylene resin expanded particles do not contact each other; (A2) Next, the polypropylene resin foam is treated by treatment for 30 minutes under a pressure of -0.05 to -0.10 MPa · G and a melting point of the polypropylene resin foamed particles + 20 to 35 ° C. While removing the air inside the particles, the expanded polypropylene resin particles are returned to the polypropylene resin; (A3) Then, the polypropylene resin is taken out from the oven and the polypropylene resin is sufficiently cooled; (A4) The polypropylene resin is then cooled. MFR of the polypropylene resin is measured by the same method as that for the resin (X).

The MFR of the polypropylene resin in-mold foam molding can be measured as follows: (B1) The polypropylene resin in-mold foam molding is pulverized using a mixer or the like; (B2) Next, the polypropylene series Except for using a pulverized polypropylene resin mold foam molded body instead of the resin foam particles, the same processing ((A1) and (A2)) as the above polypropylene resin foam particles is performed, and the polypropylene resin mold foam is performed. (B3) Then, the polypropylene resin is removed from the oven and the polypropylene resin is sufficiently cooled. (B4) Thereafter, the polypropylene is recovered by the same method as the polypropylene resin (X). The MFR of the resin is measured.

[3. Polypropylene resin foam particles)
The expanded polypropylene resin particles according to an embodiment of the present invention are expanded polypropylene resin particles and include a polypropylene resin. The polypropylene resin includes 85 to 99% by weight of the polypropylene resin (X) and a density of 0. Polypropylene resin (Z) consisting of 1 to 15% by weight of polyethylene resin (Y) of 945 g / cm ³ or more [total of (X) and (Y) is 100% by weight], and the above polypropylene resin ( Z) 0.01 part by weight or more and 1 part by weight or less of an amine compound with respect to 100 parts by weight, and silicic acid present on the surface of the polypropylene resin expanded particles with respect to 100 parts by weight of the polypropylene resin The amount of salt is more than 0 parts by weight and not more than 0.20 parts by weight.

As a method for producing the expanded polypropylene resin particles according to an embodiment of the present invention, [2. It is preferable that it is a manufacturing method of the polypropylene resin expanded particle which concerns on one Embodiment of this invention as described in the manufacturing method of a polypropylene resin expanded particle].

Each component (for example, polypropylene resin (X), polyethylene resin (Y), polypropylene resin (Z), amine compound, and silicate) contained in the expanded polypropylene resin particles according to an embodiment of the present invention Etc.) and the aspect of the polypropylene-based resin expanded particles include a preferable aspect, and [2. It may be the same as each component described in the section of [Production method of polypropylene resin expanded particles] and the aspect of the obtained polypropylene resin expanded particles.

In the polypropylene resin foam particles according to an embodiment of the present invention, the amount of silicate present on the surface of the polypropylene resin foam particles is 0.020 parts by weight or more and 0.20 weights per 100 parts by weight of the polypropylene resin. Part or less.

[4. Foam molded body)
The foamed molded product according to one embodiment of the present invention is the above [3. This is a foamed molded article using polypropylene-based resin expanded particles].

The foamed molded product according to an embodiment of the present invention is not particularly limited, but may be, for example, an in-mold foamed molded product manufactured using a mold.

The method for producing an in-mold foam molded article from polypropylene resin foam particles according to an embodiment of the present invention includes, for example, (1) filling foam particles in a mold that can be closed but cannot be sealed; (2) Next, the foamed particles are heated and fused with each other in the mold, and molded according to the mold, and the mold and the molded body are cooled with a coolant such as water; (3) Thereafter, the molded product is taken out from the mold to obtain an in-mold foam molded product.

It is preferable that the polypropylene-based resin expanded particles are given a pressure higher than atmospheric pressure inside the expanded particles before in-mold foam molding. When in-mold foam molding is performed using foam particles having a pressure higher than atmospheric pressure inside the foam particles, a polypropylene resin in-mold foam molded body with good surface appearance and little deformation is easily obtained. There is no particular limitation on the method for applying a pressure higher than atmospheric pressure to the inside of the expanded particles, but for example, pressure can be applied to the inside of the expanded particles by a conventionally known method such as an internal pressure applying method and a compression filling method. .

The pressure applied to the inside of the expanded particles, in other words, the internal pressure of the expanded particles is preferably 0.12 MPa (absolute pressure) or more and 0.40 MPa (absolute pressure) or less, 0.14 MPa (absolute pressure) or more and 0.30 MPa (absolute Pressure) or less is more preferable. When the internal pressure of the polypropylene resin expanded particles is within the above range, it tends to be easy to obtain an in-mold expanded molded article having a beautiful appearance. As the inorganic gas used for applying the internal pressure, air, nitrogen, helium, neon, argon, carbon dioxide or the like can be used. These inorganic gases may be used alone or in combination of two or more. Among these, highly versatile air and nitrogen are preferable.

According to the above method, (1) after filling polypropylene resin foamed particles into a mold or the like, using steam or the like as a heating medium at a heating steam pressure of about 0.15 to 0.4 MPa (gauge pressure) After molding with heating time of about 50 seconds, (2) after fusing the polypropylene resin foam particles together, after cooling the mold and the molded body by water cooling, (3) opening the mold, polypropylene resin mold An inner foam molded article can be obtained. When heating the mold and the molded body using water vapor, it is preferable to increase the pressure over a period of about 5 to 30 seconds until the target heating water vapor pressure is reached.

An embodiment of the present invention may have the following configuration.

[1] A step of dispersing a polypropylene resin particle, an inorganic gas foaming agent, and an inorganic dispersant silicate in an aqueous dispersion medium in a sealed container to obtain a dispersion, the polypropylene resin Polypropylene resin foamed particles by heating the inside of the closed container up to the softening temperature of the particles and pressurizing the inside of the closed container, and releasing the dispersion into a pressure region lower than the internal pressure of the closed container And the polypropylene resin particles comprise a polypropylene resin (X) 85 to 99 wt% and a polyethylene resin (Y) 1 to 15 wt% having a density of 0.945 g / cm ³ or more. Resin (Z) [total of (X) and (Y) is 100% by weight] and 0.01 part by weight or more and 1 part by weight with respect to 100 parts by weight of the polypropylene resin (Z). And the following dispersion (i) 0.05 parts by weight or more and 0.4 parts by weight or less of the silicate with respect to 100 parts by weight of the polypropylene resin particles, and (ii) A method for producing polypropylene resin expanded particles, comprising 100 parts by weight or more and 250 parts by weight or less of the aqueous dispersion medium.

[2] The dispersion liquid contains 100 parts by weight or more and 200 parts by weight or less of the aqueous dispersion medium with respect to 100 parts by weight of the polypropylene resin particles. Production method.

　 [3] Polypropylene resin expanded particles containing a polypropylene resin, and the polypropylene resin is a polyethylene resin (Y) having a polypropylene resin (X) of 85 to 99% by weight and a density of 0.945 g / cm ³ or more. 1) to 15% by weight of a polypropylene resin (Z) [the sum of (X) and (Y) is 100% by weight] and 0.01% by weight with respect to 100 parts by weight of the polypropylene resin (Z). 1 part by weight or more and 1 part by weight or less of an amine compound, and the amount of silicate present on the surface of the polypropylene resin expanded particles exceeds 0 part by weight relative to 100 parts by weight of the polypropylene resin. Polypropylene-based resin foamed particles characterized by being 20 parts by weight or less.

[4] The amount of the silicate present on the surface of the expanded polypropylene resin particles is 0.020 part by weight or more and 0.20 part by weight or less with respect to 100 parts by weight of the polypropylene resin. The expanded polypropylene resin particles according to [3].

[5] A foamed molded article using the expanded polypropylene resin particles according to [3] or [4].

An embodiment of the present invention may have the following configuration.

[A1] Polypropylene resin particles, an inorganic gas-based foaming agent, and an inorganic dispersant silicate are dispersed in an aqueous dispersion medium in a sealed container to obtain a dispersion, up to the softening temperature of the polypropylene resin particles or higher In the production method of obtaining polypropylene resin foamed particles by heating and pressurizing the inside of the sealed container and then releasing the dispersion into a pressure range lower than the internal pressure of the sealed container, the polypropylene resin particles are polypropylene resin (X). Polypropylene resin (Z) consisting of 85 to 99% by weight and polyethylene resin (Y) of 1 to 15% by weight with a density of 0.945 g / cm ³ or more. The total of (X) and (Y) is 100% by weight. ] And 100 parts by weight of the polypropylene resin (Z) and 0.01 parts by weight or more and 1 part by weight or less of an amine compound, and the dispersion is 100 weights of polypropylene resin particles. Parts to 0.05 part by weight to 0.4 parts by weight of the silicate, the production method of the polypropylene resin foamed beads which comprises an aqueous dispersion medium of 100 parts by weight to 250 parts by weight or less.

[A2] Polypropylene resin expanded particles, wherein the polypropylene resin is from 85 to 99% by weight of polypropylene resin (X) and 1 to 15% by weight of polyethylene resin (Y) having a density of 0.945 g / cm ³ or more. The amine resin of 0.01 to 1 part by weight relative to 100 parts by weight of the polypropylene resin (Z) [total of (X) and (Y) is 100% by weight] and polypropylene resin (Z) A polypropylene resin foamed particle comprising a compound, wherein the amount of silicate present on the surface of the foamed particle exceeds 0 part by weight and is 0.20 part by weight or less based on 100 parts by weight of the polypropylene resin.

[A3] The polypropylene system according to [A2], wherein the amount of silicate present on the surface of the expanded particles is 0.020 part by weight or more and 0.20 part by weight or less with respect to 100 parts by weight of the polypropylene resin Resin foam particles.

[A4] [A4] and / or a foamed molded article using the polypropylene resin expanded particles described in [A3].

Next, the expanded polypropylene resin particles and the method for producing the same according to an embodiment of the present invention will be described in detail with reference to examples and comparative examples, but are not limited thereto.

In the examples and comparative examples, the substances used were as follows, but were used without any particular purification.
・ Polypropylene resin (X) (commercially available)
Polypropylene resin: ethylene / butene-1 / propylene random copolymer [MFR = 7.5 g / 10 min, melting point 142 ° C.]
・ Polyethylene resin (Y) (commercially available)
Polyethylene resin A: [density 0.964 g / cm ³ , melting point 135 ° C.]
Polyethylene resin B: [density 0.923 g / cm ³ , melting point 121 ° C.]
Amine compound Amine compound A: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate [manufactured by ADEKA, Adeka Stub LA-77G]
Amine compound B: Condensation product of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol [manufactured by BASF, TINUVIN 622 SF]
Amine compound C: a mixture of stearyl diethanolamine monostearate and stearyl diethanolamine [manufactured by Kao Corporation, Electro Stripper TS-15B]
Amine compound D: alkyl chloride (C ₁₆ -C ₁₈ ) trimethylammonium [manufactured by Lion Specialty Chemicals, Lipocard T-28]
・ Other additives Glycerin [manufactured by Lion Corporation]
Talc [manufactured by Hayashi Kasei Co., Ltd., Talcan powder PK-S].

Hereinafter, the evaluation methods implemented in the examples and comparative examples will be described.

<Dispersion stability during production of expanded particles>
The dispersion stability during the production of polypropylene resin expanded particles was evaluated based on the following criteria.
○: Resin particles are not fused (fused) in an autoclave (pressure vessel), and foamed particles can be produced.
X: Resin particles are coalesced and agglomerated in the autoclave, and foamed particles cannot be produced.

<Blocking of single-stage expanded particles and / or double-stage expanded particles>
The obtained polypropylene resin expanded particles were evaluated based on the following criteria.
○: No blocking is observed in the total amount of the expanded particles.
X: Blocking is observed in the total amount of expanded particles.

<Measurement of amount of attached kaolin (silicate present on the surface of expanded particles)>
The amount of attached kaolin (silicate present on the surface of the expanded particles) is measured by combusting the polypropylene resin expanded particles obtained by the one-stage expansion process and the polypropylene resin particles as raw materials, respectively, and remaining after the combustion. It calculated | required from the weight difference of the ash content of the resin foam particle, and the ash content of a polypropylene resin particle. That is, the calculated formulas are Formula 1 and Formula 2.
Formula 1: Adhesive kaolin (silicate present on the surface of expanded particles) amount (part by weight) = (Amount of ash content of polypropylene resin expanded particles (part by weight) −Amount of ash content of polypropylene resin particles (part by weight)) / Kaolin ( Ratio of non-volatile content ratio of silicate) 2: Ratio of non-volatile content of kaolin (silicate) = Kaolin (silicate) ash content (g) / Kaolin (silicate) content before combustion (G).

The method for measuring the amount of ash was performed as follows. First, a measurement sample (polypropylene resin particles, polypropylene resin expanded particles, or kaolin (silicate)) was dried in an oven at 60 ° C. for 12 hours, and then allowed to cool in a desiccator for 1 hour together with silica gel. Next, in a room adjusted to an air temperature of 20 ° C. and a relative humidity of 50%, the weight (g) of the dried crucible was measured to the fourth decimal place (the fifth decimal place was rounded off). Next, the measurement sample was weighed into a crucible so as to be about 3 g, and the weight (g) of the combined crucible and measurement sample was measured to the fourth decimal place (the fifth decimal place was rounded off). The weight of the crucible at this time was W0, and the combined weight of the measurement sample and the crucible was W1. The crucible containing the measurement sample was heated at 750 ° C. for 1 hour using an electric furnace to burn the measurement sample. Next, after the measurement sample was cooled at room temperature for 1 hour, the combined weight (g) of the crucible and the ash content of the measurement sample was measured to the fourth decimal place (the fifth decimal place was rounded off). The combined weight of the crucible and the ash content of the measurement sample was W2. And the amount of ash was computed from the following formula 3.
Formula 3: Ash content of measurement sample (parts by weight) = (W2 (g) −W0 (g)) / (W1 (g) −W0 (g))
The amount of attached kaolin (silicate present on the surface of the expanded particles) in the two-stage foaming process according to one embodiment of the present invention was not changed from the amount of attached kaolin in the one-stage foaming process. Therefore, the amount of attached kaolin (silicate present on the surface of the expanded particles) of the two-stage expanded particles is the value of the amount of attached kaolin of the first-stage expanded particles.

<Foaming ratio>
“Foaming ratio” is a value calculated by the following calculation. The weight (g) (referred to as w) of the polypropylene resin expanded particles was measured. Thereafter, the polypropylene resin expanded particles are submerged in a graduated cylinder containing ethanol, and the volume (cm ³ ) of the expanded polypropylene resin particles (v ³ ) (v Measured). And the true specific gravity ((rho) b = w / v) of the polypropylene resin expanded particle was computed. Furthermore, the expansion ratio was calculated as the ratio (ρr / ρb) between the true specific gravity of the polypropylene resin expanded particles and the density ρr of the polypropylene resin particles before expansion.

<Measurement of average cell diameter of expanded particles>
Polypropylene resin foam particles were cut at the center of the foam particles using a double-edged razor (Feather, high stainless steel double-edged). In the image obtained by observing the cut surface with an optical microscope [manufactured by Keyence, VHX-100] at a magnification of 50 times, a straight line passing through almost the center of the expanded particle is drawn, and the straight line penetrates. The number of bubbles (assumed to be n) and the diameter of foamed particles (μm) (referred to as L) determined from the intersection of the straight line and the surface of the foamed particles were read. The average cell diameter of the expanded particles was calculated from the following formula 4.
Formula 4: Average bubble diameter (μm) = L / n
Calculation of the average cell diameter by the above formula 4 was carried out for 10 polypropylene resin foamed particles, and the average value was obtained.

<Surface appearance of in-mold foam molding>
The obtained in-mold foam molded article was visually observed and evaluated according to the following criteria.
○: There is no unevenness on the surface of the in-mold foamed product, and no wrinkles are observed.
X: There are irregularities on the surface of the in-mold foam molded product, and wrinkles are seen.

<Fusibility of in-mold foam molding>
On the line connecting the point A of 100 mm in the vertical axis direction from one apex of the obtained in-mold foam molded article and the point B of 100 mm in the horizontal axis direction from the apex, the depth of about 10 mm is obtained with an art knife. The cut surface was cut and the fracture surface was observed. Of the expanded particles existing within the 15 mm × 15 mm area of the fracture surface, the number (number) of particles (number Ns) broken at the particle interface in the total number of particles (number N) is expressed by the following equation 5 The value obtained was taken as the fusion rate (%) of the in-mold foam molded product.
Formula 5: Fusion rate of in-mold foam molding (%) = 100 × (1−Ns / N)
Moreover, the fusing property of the in-mold foam molded product was evaluated according to the following criteria.
A: The fusion rate of the in-mold foam molded product is 80% or more.
X: The fusion rate of the in-mold foam molding is less than 80%.

Example 1
[Production of polypropylene resin particles]
The amine compound A is added to 100 parts by weight of the polypropylene resin (X) and the polyethylene resin (Y) in Table 1 (that is, the total of (X) and (Y) is 100% by weight). The type and amount shown in Table 1 and 0.25 part by weight of glycerin were added, and these were dry blended. The mixture obtained by dry blending was melt kneaded at a resin temperature of 220 ° C. using a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., TEM26-SX), and the melt-kneaded product was extruded from the extruder. The extruded strand (melt kneaded product) was cooled with water in a 2 m long water tank and then cut to produce polypropylene resin particles (1.0 mg / particle).

[Production of single-stage expanded polypropylene resin particles]
In a pressure-resistant autoclave (sealed container) having a capacity of 10 L, 100 parts by weight (2.4 kg) of the polypropylene-based resin particles obtained as described above, 200 parts by weight of water, kaolin which is a silicate as an inorganic dispersant [ After 0.2 part by weight of ASP-170 manufactured by BASF and 0.006 part by weight of sodium dodecylbenzenesulfonate [manufactured by Kao Corporation, Neopelex G-15] as a surfactant, the charged raw materials were stirred. Then, 4.8 parts by weight of carbon dioxide as a foaming agent was added to the autoclave while stirring the raw materials to prepare a dispersion.

The autoclave contents (in the sealed container) were heated and heated to a foaming temperature of 146.0 ° C. Thereafter, carbon dioxide as a foaming agent was additionally injected into the autoclave, and the autoclave internal pressure was increased to a foaming pressure of 2.9 MPa. The inside of the autoclave was held for 30 minutes at the foaming temperature and foaming pressure. Then, the valve | bulb of the autoclave lower part was opened, the dispersion liquid was discharge | released in the air | atmosphere of 95 degreeC atmosphere through the opening orifice with a diameter of 3.6 mm, and the polypropylene-type resin single-stage expanded particle of expansion ratio about 15 time was obtained. At this time, the pressure in the container was maintained by adding carbon dioxide so that the pressure in the container did not decrease during the discharge of the dispersion. The dispersion stability during the production of polypropylene resin expanded particles was evaluated. Moreover, about the obtained polypropylene resin expanded particle, evaluation of blocking, the amount of adhesion kaolin (silicate which exists in the expanded particle surface), and the average bubble diameter were measured. These results are shown in Table 1.

[Production of two-stage expanded polypropylene resin particles]
The obtained single-stage expanded particles were dried at 75 ° C. to remove moisture, and then placed in a pressure-resistant container and pressurized to impregnate the single-stage expanded particles with air. Then, after adjusting the internal pressure of the one-stage expanded particles to 0.35 MPa (absolute pressure), the two-stage expansion process is performed by heating with water vapor (water vapor pressure 0.060 MPa-G (gauge pressure)), and the expansion ratio is about 30 Double polypropylene resin two-stage expanded particles were obtained. The obtained two-stage expanded particles were evaluated for blocking and average cell diameter. These results are shown in Table 1.

[Manufacture of expanded foam in polypropylene resin mold]
The obtained two-stage expanded particles (polypropylene-based resin expanded particles) are put into a pressure-resistant container and pressurized to impregnate the two-stage expanded particles with air, so that the internal pressure of the expanded particles is 0.20 MPa (absolute pressure) in advance. Adjusted as follows. The expanded polypropylene resin particles with the adjusted internal pressure were filled into a mold having a length of 300 mm, a width of 400 mm, and a thickness of 50 mm. The inside of the mold chamber was heated with water vapor for 10 seconds to fuse the expanded particles. After water-cooling the inside of the mold and the surface of the molded body, the molded body was taken out to obtain a foamed molded body in a polypropylene resin mold. The obtained in-mold foam molding was allowed to stand at 23 ° C. for 2 hours, and then cured at 75 ° C. for 16 hours. And after leaving still in a 23 degreeC room | chamber interior for 4 hours, evaluation was implemented about the meltability and surface appearance. These results are shown in Table 1.

(Examples 1 to 10, Comparative Examples 1 to 13)
In Examples 2 to 10 and Comparative Examples 1 to 13, in the above-mentioned [Production of Polypropylene Resin Particles], the types of additives and resin formulations were changed as shown in Tables 1 and 2, and the above-mentioned [Polypropylene Resin In the production of single-stage expanded particles], the polypropylene-based resin particles, the polypropylene-based resin single-stage expanded particles, the polypropylene-based resin two-stage expanded particles, and A polypropylene resin molded in-mold foam was produced. In Comparative Examples 1 to 5, 7 to 8, and 11 in which blocking is generated or dispersion stability is poor (×) during the production of the first-stage expanded particles, the production of the second-stage expanded particles and the in-mold expansion are performed. The molded body was not manufactured.

Tables 1 and 2 show the evaluation results of the obtained polypropylene resin single-stage expanded particles, polypropylene resin double-stage expanded particles, and polypropylene resin in-mold foam-molded articles. In addition, about Example 10 and Comparative Examples 12 and 13 which were described as "not implemented" in the two-stage foaming section of Tables 1 and 2, using the single-stage foamed particles instead of the two-stage foamed particles, the same as the above method An in-mold foam-molded article was produced by the method described above, and the evaluation of the obtained in-mold foam-molded article is described.

As can be seen from Examples 1 to 10, the polypropylene resin single-stage expanded particles obtained by the production method according to one embodiment of the present invention are close in weight ratio between the polypropylene resin and the aqueous dispersion medium, and are expanded (dispersed). Blocking did not occur even under conditions where the foam particles were likely to be fused (blocked) when the liquid was released. Further, the in-mold foam molded article made of the polypropylene resin foam particles obtained by the production method according to one embodiment of the present invention was excellent in surface appearance and fusion property.

As in Comparative Examples 1 and 7, when the amine compound is not added, or when the addition amount of the amine compound is less than the range of the present invention, the dispersion stability during the production of the single-stage expanded particles deteriorates, and the expanded particles It is understood that cannot be obtained.

As in Comparative Examples 2, 3, 4, and 5, when a polyethylene resin is not mixed, when the amount of the polyethylene resin is less than the range of the present invention, or a polyethylene resin having a density lower than the range of the present invention is used. When used, it can be seen that blocking occurs during the production of single-stage expanded particles.

When the mixing amount of the polyethylene resin exceeds the range of the present invention as in Comparative Examples 6 and 12, the elongation of the polypropylene resin foamed particles at the time of in-mold foam molding using the obtained foamed particles is reduced, and thus obtained. It can be seen that the surface appearance of the in-mold foam molded article deteriorates.

As in Comparative Example 8, when the amount of kaolin (silicate), which is an inorganic dispersant, is less than the range of the present invention, it can be seen that blocking occurs during the production process of the single-stage expanded particles.

When the amount of kaolin (silicate), which is an inorganic dispersant, is larger than the range of the present invention as in Comparative Examples 9, 10, and 13, kaolin adhering to the resin foam particles during the production of the single-stage foam particles The amount of (silicate present on the surface of the expanded particles) increases. As a result, it can be seen that the fusion property of the in-mold foam-molded article produced using the obtained foamed particles is lowered.

As in Comparative Example 11, when the amount of water, which is a dispersion medium, is less than the range of the present invention relative to the polypropylene resin particles, the polypropylene resin particles in the pressure-resistant container are produced during the production process of the single-stage expanded particles. It can be seen that the dispersion stability deteriorates and the expanded particles cannot be obtained.

Tables 1 and 2 also show the following. As in Comparative Example 2, when the polyethylene resin particles are not mixed and the weight ratio between the polypropylene resin and the aqueous dispersion medium is close, it can be seen that blocking occurs during the production of the single-stage expanded particles. In Comparative Example 9, the polyethylene resin particles are not mixed, and the weight ratio of the polypropylene resin and the aqueous dispersion medium is closer than that of Comparative Example 2. In Comparative Example 9, since a larger amount of kaolin (silicate) than the range of the present invention was added, blocking did not occur in the production process of the single-stage expanded particles. However, in Comparative Example 9, it can be seen that the amount of kaolin (silicate) adhering to the surface of the expanded polypropylene resin particles increased, and as a result, the fusion property during in-mold foam molding deteriorated. On the other hand, Example 1 in which a polyethylene resin (Y) having a density of 0.945 g / cm ³ or more is mixed is a condition in which the weight ratio of the polypropylene resin and the aqueous dispersion medium is closer than that of Comparative Example 2. In Example 1, the same amount of kaolin (silicate) as in Comparative Example 2 was added, but it was found that no blocking occurred in the production process of the single-stage expanded particles.

According to one embodiment of the present invention, polypropylene resin expanded particles for in-mold foam molding can be obtained with high productivity. Therefore, one Embodiment of this invention can be utilized suitably in various fields, such as a packaging material, a shock absorbing material, a heat insulating material, and a building member.

Claims (5)

1. A step of dispersing a polypropylene resin particle, an inorganic gas-based foaming agent, and a silicate which is an inorganic dispersant in an aqueous dispersion medium in a sealed container to obtain a dispersion;
   A step of heating the inside of the closed container up to a softening temperature of the polypropylene resin particles or higher and pressurizing the inside of the closed container, and releasing the dispersion into a pressure region lower than the internal pressure of the closed container. Obtaining resin-based resin expanded particles,
   The polypropylene resin particles are composed of a polypropylene resin (Z) [(X) consisting of 85 to 99% by weight of a polypropylene resin (X) and 1 to 15% by weight of a polyethylene resin (Y) having a density of 0.945 g / cm ³ or more. ) And (Y) is 100% by weight]
   0.01 parts by weight or more and 1 part by weight or less of an amine compound with respect to 100 parts by weight of the polypropylene resin (Z),
   The dispersion is based on 100 parts by weight of the polypropylene resin particles (i) 0.05 to 0.4 parts by weight of the silicate, and (ii) 100 to 250 parts by weight of the silicate. A method for producing expanded polypropylene resin particles, comprising an aqueous dispersion medium.
2. 2. The method for producing expanded polypropylene resin particles according to claim 1, wherein the dispersion contains 100 to 200 parts by weight of the aqueous dispersion medium with respect to 100 parts by weight of the polypropylene resin particles.
3. Polypropylene-based resin expanded particles,
   Including polypropylene resin,
   The polypropylene resin is
   Polypropylene resin (Z) consisting of 85 to 99% by weight of polypropylene resin (X) and 1 to 15% by weight of polyethylene resin (Y) having a density of 0.945 g / cm ³ or more [total of (X) and (Y) Is 100% by weight]
   0.01 parts by weight or more and 1 part by weight or less of an amine compound with respect to 100 parts by weight of the polypropylene resin (Z),
   A polypropylene resin characterized in that the amount of silicate present on the surface of the expanded polypropylene resin particles is more than 0 parts by weight and less than 0.20 parts by weight with respect to 100 parts by weight of the polypropylene resin. Expanded particles.
4. The amount of the silicate present on the surface of the expanded polypropylene resin particles is 0.020 part by weight or more and 0.20 part by weight or less with respect to 100 parts by weight of the polypropylene resin. Item 4. The expanded polypropylene resin particles according to Item 3.
5. A foam molded article using the polypropylene resin foamed particles according to claim 3 or 4.