WO2019189564A1

WO2019189564A1 - Polyolefin resin foamable particles, method for producing same, and foam molded article of polyolefin resin

Info

Publication number: WO2019189564A1
Application number: PCT/JP2019/013569
Authority: WO
Inventors: 福澤　淳
Original assignee: 株式会社カネカ
Priority date: 2018-03-30
Filing date: 2019-03-28
Publication date: 2019-10-03
Also published as: CN110317395A; JPWO2019189564A1; CN112004872B; CN112004872A; JP7227223B2

Abstract

An embodiment of the present invention provides polyolefin resin foamable particles, a method for producing the same, and a foam molded article of polyolefin resin. The polyolefin resin foamable particles contain a polyolefin resin and Ag zeolite as an additive. The polyolefin resin foamable particles have a good foaming performance, and light-weight polyolefin resin foamable particles exhibiting a good foaming effect can be obtained even without the use of an additive such as polyethylene glycol or glycerol.

Description

Polyolefin resin foamed particles, production method thereof, and foamed molded article of polyolefin resin

The present invention belongs to the technical field of polymer foam materials, and relates to a polyolefin resin foamed particle, a method for producing the foamed particle, and a polyolefin resin foam molded product obtained by foaming the polyolefin resin foamed particle in a mold. .

Foamed moldings of polyolefin resins are lighter than unfoamed molded products, so buffer packaging materials, recoverable containers, heat-insulating transport containers (for example, fresh seafood transport boxes, take-out transport boxes, etc.) ), Automotive parts (for example, toolboxes, floor core materials, etc.).

A foamed molded article of polyolefin resin can be obtained by in-mold foam molding of polyolefin resin foamed particles (hereinafter also simply referred to as “foamed particles”). Polyolefin resin foam particles are obtained by impregnating a polyolefin resin particle containing a polyolefin resin (hereinafter also simply referred to as “resin particles”) with a foaming agent and then foaming the polyolefin resin particles. Can do.

In the conventional production method, when polyolefin resin foamed particles are produced using water and / or carbon dioxide as a foaming agent, additives for hydrophilic organic substances such as polyethylene glycol and glycerin are used in order to improve lightness. (For example, Patent Document 1). When organic additives are used, the COD of the wastewater becomes high, and wastewater treatment is necessary as an environmental measure.

In the conventional production method, there is a method in which the amount of polyethylene glycol, glycerin, or the like is reduced by adding synthetic zeolite or natural zeolite (for example, Patent Document 2).

JP 2010-031243 A JP 2009-167236 A

However, the conventional techniques as described above have room for further improvement from the viewpoints of light weight, environmental load and in-mold foam moldability of the polyolefin resin foam particles obtained.

One embodiment of the present invention has been made in order to solve the above-described problems in the prior art, and its main purpose is to produce polyolefin resin foamed particles using a foaming agent, particularly as a foaming agent. When producing lightweight polyolefin-based resin expanded particles using water and / or carbon dioxide gas, it is possible to reduce or eliminate the use of hydrophilic organic chemical additives, so the COD of wastewater is low, An object of the present invention is to provide polyolefin resin expanded particles with reduced environmental burden and excellent in-mold moldability.

As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by using Ag-based zeolite as an additive. That is, when the present inventors produce polyolefin resin expanded particles using Ag-based zeolite as an additive, not only can the environmental load during production be reduced, but also a lightweight polyolefin resin having excellent in-moldability. It was uniquely found that expanded particles can be obtained.

That is, the polyolefin resin foam particles according to an embodiment of the present invention are foam particles obtained by foaming polyolefin resin particles with a foaming agent, and the polyolefin resin particles include a polyolefin resin and an additive. The Ag-based zeolite has an average particle diameter of 1.0 μm to 10.0 μm, and the content of the Ag-based zeolite is 0.2 with respect to 100 parts by weight of the polyolefin-based resin. Parts by weight to 3.0 parts by weight, and the expanded particles have a bulk density of 20 g / L to 55 g / L.

Further, the method for producing a polyolefin resin expanded particle according to an embodiment of the present invention is a method for producing a polyolefin resin expanded particle comprising a step of foaming a polyolefin resin particle in the presence of a foaming agent. The resin particles are made of a polyolefin resin composition containing 0.2 parts by weight to 3 parts by weight of Ag-based zeolite with respect to 100 parts by weight of the polyolefin resin, and the polyolefin resin expanded particles have a bulk density of 20 g / L to 55 g. The average particle diameter of the Ag-based zeolite is 1.0 μm to 10.0 μm.

Further, according to an embodiment of the present invention, the use of the zeolite used for the production of the polyolefin resin expanded particles is a use of zeolite for the production of the polyolefin resin expanded particles, and the zeolite is an Ag zeolite. The polyolefin resin is selected from a resin containing a polypropylene resin and / or a polyethylene resin, and the polyolefin resin foamed particles obtained by foaming the polyolefin resin have a bulk density. 20 g / L to 55 g / L.

According to one embodiment of the present invention, there is an effect that it is possible to provide polyolefin-based resin foam particles that are lightweight, have a small environmental load, and have excellent in-mold foam moldability.

Hereinafter, one embodiment of the present invention will be described, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications can be made within the scope of the right of the invention, that is, the scope shown in the claims. Further, all the embodiments or examples obtained by appropriately combining technical means respectively described in different embodiments and 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)”.

Also, 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 a copolymer comprising 2 or more _integer), also referred to as _{X 1 / X 2 / ··· /} X n copolymer body. 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.

In this specification, “foaming material” means a material obtained through a foaming process. In particular, a foam obtained by in-mold foam molding is referred to as an “in-mold foam molded body”.

[Technical idea of one embodiment of the present invention]
As described above, when a hydrophilic organic substance is used, it is necessary to perform wastewater treatment as an environmental measure in order to reduce the COD of wastewater. In order to reduce the amount of the hydrophilic organic substance used, a case where synthetic zeolite or natural zeolite is used as in Patent Document 2 will be described. In this case, in order to improve the foaming effect in the one-stage foaming process, that is, in order to obtain single-stage foamed particles having a low bulk density, it is necessary to use a large amount of synthetic zeolite and / or natural zeolite. The inventor noticed for the first time. Further, when the present inventors obtain a polyolefin-based resin expanded particle using a large amount of synthetic zeolite and / or natural zeolite, the open cell ratio of the obtained expanded particle is increased, and as a result, the expansion ratio of the expanded particle is increased. It was uniquely found that the dimensional shrinkage ratio of the in-mold foam molded product obtained from the foamed particles was increased, the surface wrinkles were conspicuous, and the surface appearance was deteriorated.

That is, an object according to an embodiment of the present invention is to provide polyolefin-based resin foamed particles that are lightweight, have a low environmental load, and have excellent in-mold foam moldability.

As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by using Ag-based zeolite, and has completed the present invention.

[Polyolefin resin foamed particles]
The polyolefin resin foam particles according to an embodiment of the present invention are foam particles obtained by foaming polyolefin resin particles with a foaming agent, and the polyolefin resin particles are a polyolefin resin and an additive. Ag-based zeolite, the average particle diameter of the Ag-based zeolite is 1.0 μm to 10.0 μm, and the content of the Ag-based zeolite is 0.2 with respect to 100 parts by weight of the polyolefin-based resin. Parts by weight to 3.0 parts by weight, and the expanded particles have a bulk density of 20 g / L to 55 g / L. The polyolefin-based resin expanded particles according to an embodiment of the present invention are hereinafter also referred to as the present expanded particles.
Provided is a polyolefin resin expanded particle having a configuration.

Since the expanded particles have the above-described configuration, they are lightweight, have a low environmental load, and have excellent in-mold expansion moldability. Specifically, since the present expanded particles contain Ag-based zeolite as an additive, they have excellent performance even when they do not contain hydrophilic organic substances such as polyethylene glycol and glycerin as additives. In addition, since the present foamed particles use Ag-based zeolite as an additive in the production thereof, lightweight foamed particles can be obtained while reducing or eliminating wastewater treatment, so the environmental load during production is reduced. Has the advantage of. Furthermore, the foamed particles can provide an in-mold foam molded article having excellent surface properties (for example, good appearance and inconspicuous wrinkles), low dimensional shrinkage, and excellent fusion rate.

<Polyolefin resin particles>
The polyolefin resin particles according to one embodiment of the present invention are used for producing the present expanded particles. That is, the foamed particles are produced by foaming the polyolefin resin particles according to an embodiment of the present invention. The polyolefin resin particles in one embodiment of the present invention include an additive such as a polyolefin resin and Ag zeolite.

In one embodiment of the present invention, the polyolefin resin may be selected from a resin including a polypropylene resin and / or a polyethylene resin. Examples of the polyolefin resin include a polyethylene resin and a polypropylene resin. They may be used alone or in combination of two or more.

The polyolefin resin is preferably selected from resins including a polypropylene resin and / or a polyethylene resin. According to the said structure, it has the advantage that it is excellent in chemical-resistance, heat resistance, and the distortion recovery property after compression. The excellent strain recovery property intends to have a high strain recovery rate.

Examples of the polyethylene resin used in an embodiment of the present invention include high density polyethylene, medium density polyethylene, low density polyethylene, and linear low density polyethylene. They may be used alone or in combination of two or more.

The polypropylene resin used in an embodiment of the present invention may be, for example, a propylene homopolymer or copolymer, and these polypropylene resins may be partially crosslinked or crosslinked. It may not be. The copolymer may be a copolymer composed of an α-olefin and propylene, wherein the copolymer is an α-olefin / propylene random copolymer, an α-olefin / propylene block copolymer. It may be a coalescence or the like. They may be used alone or in combination of two or more.

Other polyolefin resins that can be used in an embodiment of the present invention are not particularly limited, and may be polyolefin resins that are commonly used in the art (technical field). When the polyolefin resin includes a polyolefin resin other than the polyethylene resin and the polypropylene resin, the total amount of the polyethylene resin and the polypropylene resin is 70% by mass or more based on the total mass of the polyolefin resin, preferably It is preferable to be 80% by mass or more, more preferably 90% by mass or more.

Among the polyolefin-based resins, propylene / ethylene random copolymer is particularly preferable because of the excellent foamability when obtaining expanded polyolefin-based resin particles and the surface properties of the in-mold foam-molded product of polyolefin-based resin that can be provided by the expanded particles. Polymers, propylene / ethylene / butene-1 random copolymers and propylene / butene-1 random copolymers can be suitably used. As the polyolefin resin, those having a content of components derived from a comonomer other than propylene of 1 to 5% by weight can be suitably used.

Although there is no restriction | limiting in particular in the melt index of the polyolefin-type resin used by one Embodiment of this invention, It is preferable that the said melt index is 0.5 g / 10min or more and 30 g / 10min or less, More preferably, 2 g / It is 10 minutes or more and 15 g / 10 minutes or less. In particular, when the polyolefin resin is a polypropylene resin, the melt index is most preferably 4 g / 10 min or more and 9 g / 10 min or less. When the melt index is less than 0.5 g / 10 min, expanded particles having a high expansion ratio tend not to be obtained, and bubbles tend to be non-uniform. In addition, when the melt index exceeds 30 g / 10 min, foamed particles with a high expansion ratio tend to be easily obtained, but the foamed cells may be broken to increase the open-cell ratio of the foamed particles. And air bubbles may be non-uniform. The melt index of the polyolefin resin in one embodiment of the present invention is a value measured at a temperature of 230 ° C. and a load of 2.16 kg in accordance with ASTM D1238 in the case of (a) a polypropylene resin, and (b) In the case of polyethylene resin, it is a value measured at a temperature of 190 ° C. and a load of 2.16 kg in accordance with ASTM D1238.

The melting point of the polypropylene resin is preferably 130 ° C. or higher and 165 ° C. or lower, and more preferably 135 ° C. or higher and 155 ° C. or lower. When the melting point of the polypropylene resin is less than 130 ° C., the heat resistance and mechanical strength tend to be insufficient. Moreover, when the melting point of the polypropylene resin exceeds 165 ° C., it tends to be difficult to ensure the fusion at the time of in-mold foam molding. Here, the melting point of the polypropylene resin is a temperature of 10 to 10 ° C./min from 40 ° C. to 220 ° C., and then 10 ° C./min to 40 ° C. with a differential scanning calorimeter. It is the peak temperature of the endothermic peak in the DSC curve obtained when it is cooled down at 220 ° C. and heated again at a rate of 10 ° C./min.

The melting point of the polyethylene resin is preferably 105 ° C. or higher and 135 ° C. or lower, and more preferably 115 ° C. or higher and 125 ° C. or lower. The melting point of the polyethylene resin can be measured by the same method as the method for measuring the melting point of the polypropylene resin except that a polyethylene resin is used instead of the polypropylene resin.

In the polyolefin resin foamed particles produced using polyolefin resin particles, the structure of the polyolefin resin particles changes, but the composition of the polyolefin resin particles does not change. In addition, in the polyolefin resin-in-mold foam-molded article produced using the polyolefin resin foam particles produced using the polyolefin resin particles, the structure of the polyolefin resin foam particles changes, but the polyolefin resin foam The composition of the particles does not change. Therefore, the content, melting point, or melt index value of the comomer-derived component obtained by analyzing the polyolefin resin expanded particles or the polyolefin resin in-mold foam molded product, respectively, is the polyolefin resin that is the raw material thereof. It can be regarded as the value of the content, melting point, or melt index of the comomer-derived component of the particles.

Further, by analyzing the polyolefin resin foamed particles or the polyolefin resin in-mold foam molded product, it is possible to analyze the composition of the polyolefin resin contained in the polypropylene resin particles as the raw material.

In this specification, the melting point of the polyolefin resin expanded particles or the polyolefin resin-in-mold-in-molded molded product is the same as that of the polyolefin-based resin expanded particles or polyolefin-based resin-in-mold expanded molded product, respectively, instead of the polypropylene resin. The value obtained by measurement by the same method as the method for measuring the melting point of the polypropylene resin.

The melt index of the polyolefin resin foam particles can be measured as follows: (A1) The polyolefin resin foam particles are placed in an oven that can be depressurized so that the polyolefin resin foam particles do not contact each other. (A2) Next, the polyolefin resin was treated at a pressure of −0.05 to −0.10 MPa · G and a melting point of the polyolefin resin expanded particles of +20 to 35 ° C. for 30 minutes. Returning the polyolefin resin foamed particles to the polyolefin resin while removing the air inside the foamed particles; (A3) Then, taking out the polyolefin resin from the oven and sufficiently cooling the polyolefin resin; (A4); Using the same method as for polyolefin resin, the melt index of the above polyolefin resin is used. Scan to measure.

The melt index of the polyolefin resin in-mold foam molding can be measured as follows: (B1) The polyolefin resin in-mold foam molding is pulverized using a mixer or the like; (B2) Next, the polyolefin The same treatment ((A1) and (A2)) as that for the polyolefin resin foam particles described above was performed, except that a pulverized polyolefin resin mold foam molded body was used instead of the resin foam particles. (B3) Then, the polyolefin resin is taken out from the oven, and the polyolefin resin is sufficiently cooled. (B4) Thereafter, the polyolefin resin is recovered by the same method as the polyolefin resin. Measure the melt index.

In addition to the polyolefin resin, various additives can be added to the polyolefin resin particles according to an embodiment of the present invention, and it is essential to add Ag zeolite. Ag-based zeolite is also called Ag-supported zeolite, and the zeolite is used as a support, and by adsorption or ion exchange, Ag ions or Ag ions and a plurality of metal ions such as zinc are stably formed into a framework structure of the zeolite. It is a powder that is distributed and combined with various auxiliaries. The content of Ag ions in the Ag-based zeolite is 0.1 to 10% with respect to the mass of the Ag-based zeolite, and Ag-based zeolite using metal ions such as zinc and copper in combination with Ag ions is also used. can do. Examples of commercially available Ag-based zeolites include ZEMIC from Sinanen Zeomic Co., Ltd., and silver ion-supported zeolite from Newstone International Co., Ltd.

The range of the average particle diameter of Ag-based zeolite is very wide, there is an average particle diameter on the nano order, and an average particle diameter on the order of millimeters. When using Ag-based zeolite as an additive for producing polyolefin resin expanded particles according to an embodiment of the present invention, Ag-based zeolite having an average particle size of 1.0 μm to 10.0 μm can be used. The average particle size of the Ag-based zeolite is preferably 1.2 μm to 5 μm, more preferably 1.5 μm to 3.5 μm, and even more preferably 1.5 μm to 2.5 μm. When the average particle diameter of Ag-based zeolite is smaller than 1 μm, the surface beauty and dimensional shrinkage of the molded article of polyolefin resin expanded particles tend to deteriorate. When the average particle diameter is larger than 10 μm, polyolefin resin expanded There is a tendency that the dimensional shrinkage ratio of the molded body of particles deteriorates. The average particle size of the Ag-based zeolite in one embodiment of the present invention can be measured by a laser diffraction-scattering method. The deterioration of the dimensional shrinkage rate of the molded product is intended to mean that the dimensional shrinkage rate of the molded product is large.

The amount of Ag-based zeolite used in one embodiment of the present invention is 0.2 to 3 parts by weight with respect to 100 parts by weight of the polyolefin-based resin. Further, in order to obtain an in-mold foam molded article having a good appearance and a low dimensional shrinkage ratio, the addition amount of the Ag-based zeolite is more preferably 0.2 to 2.5 parts by weight. If the added amount of Ag-based zeolite is less than 0.2 parts by weight, it becomes difficult to obtain expanded particles having a high expansion ratio. In addition, the bubbles of the expanded particles become coarse or non-uniform, and the surface smoothness of the in-mold expanded molded product tends to deteriorate. When the added amount of Ag-based zeolite is larger than 3 parts by weight, the foamed molded product obtained by in-mold foam molding using the obtained foamed particles is deteriorated because the bubbles of the obtained foamed particles become too small. Tend. In addition, the bubbles in the expanded particles become continuous, and the in-mold foam molded product after the in-mold foam molding is likely to have a large dimensional shrinkage.

In this specification, “addition” can also be said to be “use”. In addition, “addition” and “use” are concepts in manufacturing, and can be said to be “content” in a substance obtained by manufacturing. Therefore, in the present specification, “addition”, “use” and “containing”, or “addition amount”, “use amount” and “content” are interchangeable.

In addition, when Ag-based zeolite is used as an additive, Ag-based zeolite not only has water absorption properties but also has a nucleating action. Therefore, when using Ag-based zeolite as an additive, it is possible not only to reduce the amount of hydrophilic organic compound used or to realize the non-use of hydrophilic organic compound, but also to use an additive such as a foam nucleating agent. The amount can also be reduced.

In addition, since silver ions have an antibacterial action, foamed molded articles produced by adding Ag-based zeolite to polyolefin resin particles also have antibacterial performance.

More specifically, polyolefin resin foam particles produced by adding Ag-based zeolite to polyolefin resin particles, and in-mold foam moldings obtained by in-mold foam molding of the foam particles also have antibacterial performance. Have.

The polyolefin resin foamed particles according to an embodiment of the present invention may further contain a hydrophilic compound. The hydrophilic compound means a compound having a hydrophilic group such as a carboxy group, a hydroxy group, an amino group, a sulfo group, or a polyoxyethylene group in the molecule or a derivative thereof, and includes a hydrophilic polymer.

Specific examples of the hydrophilic compound include a carboxy group-containing compound and a hydroxy-containing compound.

More specifically, for example, carboxy group-containing compounds include lauric acid and sodium laurate, and hydroxy-containing compounds include ethylene glycol and glycerin. Other hydrophilic organic compounds include organic compounds having a triazine ring, such as melamine, isocyanuric acid, and isocyanuric acid condensates. A hydrophilic compound may be used individually by 1 type, and may use 2 or more types together.

Further, the hydrophilic polymer is (a) a polymer having a water absorption rate of 0.5% by weight or more measured according to ASTM D570, including a so-called hygroscopic polymer, and (b) dissolved in water. Without being able to absorb water of several to several hundred times its own weight, it is difficult to dehydrate even under pressure, that is, a water-absorbing polymer, and (c) soluble in water at room temperature or high temperature. It means a polymer, that is, a water-soluble polymer.

Examples of hydrophilic polymers include: (a) carboxy group-containing polymers such as ethylene / (meth) acrylic copolymers; (b) polyamides such as nylon-6, nylon-6,6, and copolymerized nylon; Nonionic water-absorbing polymers such as polyethylene glycol and polypropylene glycol; (d) Polyether / polyolefin resin block copolymer represented by PELESTAT (trade name, manufactured by Sanyo Chemical Industries, Ltd.) and the like; (e) AQUACALK (Trade name, manufactured by Sumitomo Seika Co., Ltd.) These hydrophilic polymers may be used individually by 1 type, and may use 2 or more types together.

However, when a hydrophilic polymer is used, the COD of wastewater becomes high and wastewater treatment is necessary as an environmental measure. Therefore, in one embodiment of the present invention, it is preferable to add a small amount of hydrophilic polymer or not. In the embodiment of the present invention, since the above Ag-based zeolite is used as an additive, a foaming effect can be obtained without using a hydrophilic polymer as in the prior art.

A foam nucleating agent that promotes the formation of bubble nuclei may be further added to the polyolefin resin particles. Examples of the foam nucleating agent used in one embodiment of the present invention include foam nucleating agents such as talc, calcium stearate, calcium carbonate, silica, kaolin, titanium oxide, bentonite, and barium sulfate. They may be used alone or in combination of two or more. Among these foam nucleating agents, talc, calcium carbonate, and calcium stearate are preferable because they are inexpensive and easily obtain uniform bubbles. In one embodiment of the present invention, the addition amount of the foam nucleating agent varies depending on the type of foaming agent used. In general, the addition amount of the foam nucleating agent is preferably 0.005 to 2 parts by weight and more preferably 0.01 to 1 part by weight with respect to 100 parts by weight of the polyolefin resin. Further preferred. When the addition amount of the foam nucleating agent is less than 0.005 parts by weight, there is a tendency that it is difficult to increase the expansion ratio of the polyolefin resin foamed particles, and the uniformity of the bubbles may be lowered. When the amount of the foam nucleating agent exceeds 2 parts by weight, the average cell diameter of the polyethylene resin foamed particles tends to be too small, and the in-mold foam moldability tends to be poor. In one embodiment of the present invention, Ag-based zeolite also has an effect as a foam nucleating agent, and therefore foaming is possible even when the above-described foaming nucleating agent is not further added.

Additives such as an antistatic agent, a colorant, a flame retardant, a heat stabilizer, a light stabilizer, and a radiation heat transfer inhibitor are added to the polyolefin resin particles as necessary within a range not inhibiting the effect of one embodiment of the present invention. May be added. Examples of the heat stabilizer include hindered amine compounds, phosphorus compounds, and epoxy compounds. Examples of the light-resistant stabilizer include hindered amines, phosphorus-based stabilizers, and epoxy compounds, and further include phenol-based antioxidants, nitrogen-based stabilizers, sulfur-based stabilizers, and benzotriazoles.

Examples of the colorant that can be used in an embodiment of the present invention include carbon black, ketjen black, iron black, cadmium yellow, cadmium red, cobalt violet, cobalt blue, bitumen, ultramarine, yellow lead, zinc yellow, barium yellow, and the like. And inorganic pigments such as perylene, polyazo, quinacridone, phthalocyanine, perinone, anthraquinone, thioindigo, dioxazine, isoindolinone, and quinophthalone.

The antistatic agent that can be used in one embodiment of the present invention is not particularly limited, and examples thereof include low molecular weight antistatic agents such as fatty acid ester compounds, aliphatic ethanolamine compounds, and aliphatic ethanolamide compounds; An inhibitor etc. are mentioned. These antistatic agents may be used individually by 1 type, and may use 2 or more types together. Examples of the antistatic agent include Electro Stripper TS-11B (manufactured by Kao Corporation) as a commercial product of a mixture of octadecyl diethanolamine monostearate and octadecyl diethanolamine. As a commercial product of a mixture with an aliphatic alcohol, Electro Stripper TS-15B (manufactured by Kao Corporation) and the like can be mentioned. In one embodiment of the present invention, the content of the antistatic agent is preferably 0.1 to 3.0 parts by weight, and preferably 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the polyolefin resin. Is particularly preferred. When the content of the antistatic agent is less than 0.1 parts by weight, the antistatic performance cannot be exhibited. When the content exceeds 3 parts by weight, the deformation shrinkage rate of the obtained in-mold foam molded product is large, and molding is performed. The stretching of the body surface also tends to deteriorate. The “deformation shrinkage rate” is used in the same meaning as the “dimensional shrinkage rate”.

As a radiation heat transfer inhibitor (a substance having a property of reflecting, scattering or absorbing light in the near infrared or infrared region (for example, a wavelength region of about 800 to 3000 nm)) used in an embodiment of the present invention, For example, graphite, graphene, activated carbon, carbon black, titanium oxide, metal aluminum, and the like can be given.

<Production method of polyolefin resin particles>
Examples of the method for producing the polyolefin resin particles in one embodiment of the present invention include the following production process (also referred to as “granulation process”). First, a polyolefin resin and an Ag-based zeolite are blended with other additives as required by a mixing method such as a dry blend method or a master batch method. Next, the blended product obtained using an extruder, kneader, Banbury mixer, etc. is melt-kneaded and then extruded, and the extruded blended product (melt-kneaded product) is shredded with a cutter, pelletizer, etc., cylindrical, Polyolefin resin particles having a desired shape such as an elliptical shape, a spherical shape, a cubic shape, and a rectangular parallelepiped shape are used. Alternatively, the blend may be cut into particles immediately after being extruded directly from a die into water and cooled.

In one embodiment of the present invention, a method using an extruder (for example, a twin screw extruder) is used, but the method is not limited thereto. Specifically, a blended product is prepared by previously blending a polyolefin-based resin with an Ag-based zeolite additive, a foam nucleating agent, and other additives added as necessary. The obtained blended product is charged into an extruder and melt-kneaded, and the resulting melt-kneaded product is extruded into a strand through a die, and the resulting extrudate is chopped after water cooling to produce polyolefin resin particles. . Or when using a liquid hydrophilic compound, you may add and knead | mix a liquid hydrophilic compound to the molten polyolefin-type resin in the intermediate part of an extruder. Further, the hydrophilic compound may be supplied quantitatively in liquid form at the polyolefin resin supply port of the extruder. At this time, in order to reduce the transpiration of the raw material, the temperature of the cylinder and the die part of the extruder is preferably 300 ° C. or lower, more preferably 280 ° C. or lower.

<Polyolefin resin foam particles>
The polyolefin resin expanded particles according to an embodiment of the present invention are obtained by expanding polyolefin resin particles.

The bulk density of the expanded polyolefin resin particles according to an embodiment of the present invention is 20 g / L to 55 g / L. The bulk density is preferably 32 g / L to 55 g / L, and the bulk density is more preferably 35 g / L to 55 g / L. When the bulk density is less than 20 g / L, the resulting foamed molded product of polyolefin resin tends to shrink or deform, and the mechanical performance tends to decrease. The fact that the molded body is easily shrunk or deformed means that the dimensional shrinkage rate or deformation shrinkage rate of the molded body tends to be large. When the bulk density exceeds 55 g / L, the mechanical strength of the obtained in-mold foam molded product tends to be high, but the advantage of reducing the weight of the in-mold foam molded product cannot be obtained, and the obtained in-mold There exists a tendency for the softness | flexibility and buffer characteristic of a foaming molding to become inadequate. The tendency that the mechanical strength of the in-mold foam-molded product tends to increase means that the dimensional shrinkage rate of the in-mold foam-molded product tends to be suppressed.

The average cell diameter of the expanded polyolefin resin particles according to an embodiment of the present invention is preferably 60 μm to 250 μm, and more preferably 100 μm to 190 μm. When the average cell diameter is smaller than 60 μm, the surface aesthetics of the obtained in-mold foam molded product tends to be lowered, and the compressive strength tends to be lowered. When the average cell diameter exceeds 250 μm, the uniformity of the cell diameter tends to decrease, and the surface beauty of the foamed molded product tends to decrease.

The open cell ratio of the polyolefin resin expanded particles according to an embodiment of the present invention is preferably 10% or less. When the open cell ratio is 10% or more, when the foamed particles obtained are subjected to in-mold foam molding, the foamed particles do not shrink and the surface properties of the resulting foamed molded article of polyolefin resin may be reduced. Absent. Here, the open cell ratio of the polyolefin resin expanded particles can be measured by performing the method described in Procedure D (PROCEDURE C) of ASTM D2856-87 for the polyolefin resin expanded particles.

The water content of the polyolefin resin expanded particles according to an embodiment of the present invention is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.7% by mass or more and 8% by mass or less. More preferably, it is 1 mass% or more and 5 mass% or less. If the moisture content is less than 0.1%, only polyolefin resin foam particles having a low expansion ratio may be obtained. If the moisture content exceeds 10%, the inside of the polyolefin resin foam particles after foaming is low. Due to the internal pressure, the foamed particles tend to shrink, and even after aging (also referred to as curing) in the oven after foaming, the foamed particles tend to remain shrunk. By the shrinkage remaining in the expanded particles, it is intended that the expanded particles remain contracted.

[Method for producing polyolefin resin expanded particles]
The method for producing expanded polyolefin resin particles according to an embodiment of the present invention is a method for producing expanded polyolefin resin particles comprising a step of foaming polyolefin resin particles in the presence of a foaming agent. Comprises a polyolefin resin composition containing 0.2 parts by weight to 3.0 parts by weight of Ag zeolite with respect to 100 parts by weight of the polyolefin resin, and the polyolefin resin expanded particles have a bulk density of 20 g / L to The average particle diameter of the Ag-based zeolite is 1.0 μm to 10.0 μm. The method for producing polyolefin resin expanded particles according to one embodiment of the present invention is also referred to as this production method.

Since this production method has the above-described configuration, it is lightweight, can provide an expanded polyolefin resin particle having a low environmental burden and excellent in-mold foam moldability.

Examples of the method for producing the polyolefin resin expanded particles in one embodiment of the present invention include the following production process (foaming process).

The polyolefin resin expanded particles according to an embodiment of the present invention contain a dispersion liquid containing the polyolefin resin particles obtained as described above, an aqueous medium, an inorganic dispersant, and a dispersion aid in a pressure resistant container. A step of increasing the temperature in the pressure vessel above the softening point temperature of the polyolefin resin particles in the presence of a foaming agent while stirring the dispersion, and a pressure resistance lower than the internal pressure of the pressure vessel. It can be manufactured by a manufacturing method (manufacturing process) having a step of discharging the dispersion in the container to foam the polyolefin resin particles.

“The dispersion in the pressure vessel” can be said to be “the contents of the pressure vessel”. The “pressure range lower than the internal pressure of the pressure vessel” is also referred to as “low pressure range”.

In the process of releasing the pressure vessel contents to a pressure range lower than the internal pressure of the pressure vessel, inorganic gas such as carbon dioxide, nitrogen or air is put into the pressure vessel at any stage before the dispersion is released to the low pressure range. By press-fitting, the internal pressure in the pressure-resistant container can be increased, the pressure release speed at the time of foaming can be adjusted, and the foaming ratio and the average cell diameter can be adjusted.

As the aqueous medium used in an embodiment of the present invention, for example, water, alcohol, ethylene glycol or the like can be used, and among these, water is preferably used.

Although there is no restriction | limiting in particular as the usage-amount of an aqueous medium, From a viewpoint of productivity, 100 to 500 weight part is preferable with respect to 100 weight part of polyolefin-type resin particles, More preferably, 130 to 300 weight part is more preferable. And most preferably 150 parts by weight or more and 210 parts by weight or less. When the amount of the aqueous medium used is (a) less than 100 parts by weight, the dispersion containing the polyolefin resin particles, the aqueous medium, the inorganic dispersant, and the dispersion aid may not be stable, and (b) 500 weights If it exceeds the part, productivity may decrease.

There is no restriction | limiting in particular as an inorganic type dispersing agent which can be used by one Embodiment of this invention, The inorganic type dispersing agent generally used can be used. Specifically, aluminosilicates based on silica-alumina such as barium sulfate, kaolin and talc, aluminum phosphate, titanium oxide, calcium phosphate such as tricalcium phosphate, calcium carbonate, magnesium phosphate, basic magnesium carbonate, Examples thereof include basic zinc carbonate.
Of these, aluminosilicate, calcium phosphate, and magnesium phosphate mainly composed of barium sulfate and silica-alumina are preferable from the viewpoint of having a dispersion effect with a small amount of use and a small wastewater treatment load.

The addition amount of such an inorganic dispersant is not particularly limited, and is appropriately adjusted so that the stabilizing effect of the dispersion is exhibited. The addition amount of the inorganic dispersant is appropriately adjusted in consideration of the addition ratio of the inorganic dispersant and the dispersion aid. The amount of the inorganic dispersant added is preferably 0.01 parts by weight or more and 5 parts by weight or less, and 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 polyolefin resin particles. Most preferably, it is 0.1 parts by weight or more and 3 parts by weight or less. If the amount of the inorganic dispersant added is (a) less than 0.01 parts by weight, the stability of the dispersion tends to decrease at a temperature higher than the softening point temperature of the polyolefin resin particles, and (b) exceeds 5 parts by weight. As a result, a large amount of the dispersant adheres to the surface of the resulting polyolefin resin foamed particles, and as a result, the fusion property of the polyolefin resin in-mold foam molded product tends to decrease when the foamed particles are molded in-mold. .

As the dispersion aid used in one embodiment of the present invention, it is preferable to use a surfactant. As the surfactant, generally used anionic, nonionic, cationic surfactants, amphoteric surfactants and the like can be used. Among these, from the viewpoint of the stability of the dispersion liquid comprising polyolefin resin particles, an aqueous medium, an inorganic dispersant, and a dispersion aid, an anionic surfactant is preferable as the surfactant. Acid salt, alkane sulfonate, alkylbenzene sulfonate, alkyl naphthalene sulfonate, sulfosuccinate, α-olefin sulfonate, N-acyl sulfonate, alkyl sulfate, alkyl ether sulfate, alkyl allyl ether sulfate More preferred are sulfonates such as salts and alkyl amide sulfates, and most preferred are alkyl sulfonates, alkane sulfonates, α-olefin sulfonates, and alkyl benzene sulfonates.

The amount of such a dispersion aid added is not particularly limited and can be appropriately adjusted so that the dispersion is stable. The addition amount of the dispersion aid is preferably 0.001 part by weight or more and 0.5 part by weight or less, more preferably 0.003 part by weight or more and 0.3 part by weight with respect to 100 parts by weight of the polyolefin resin particles. Part or less, and most preferably 0.005 part by weight or more and 0.2 part by weight or less. If the added amount of the dispersion aid is (a) less than 0.001 part by weight, the stability of the dispersion tends to decrease above the softening point temperature of the resin particles. There is a tendency that the foaming of the liquid becomes intense and the load of wastewater treatment increases.

The foaming agent used in one embodiment of the present invention is not particularly limited, and a commonly used foaming agent can be used. Specific examples of the foaming agent include inorganic foaming agents such as carbon dioxide, air, oxygen, nitrogen, and water. When water is used as the foaming agent, water used as the aqueous medium may be used as the foaming agent. preferable.

The foaming agent is preferably water and / or carbon dioxide. According to the said structure, it has the advantage that an environmental load is small and there is no combustion risk.

Among the foaming agents described above, in one embodiment of the present invention, even when carbon dioxide is used as the foaming agent, the cell diameter of the polyolefin resin foamed particles does not become extremely fine, and in-mold foam moldability is achieved. Excellent foamed polyolefin resin particles can be obtained. Therefore, in one Embodiment of this invention, it becomes a preferable aspect to use a carbon dioxide as a foaming agent.

The foaming agent in one embodiment of the present invention may be introduced into the pressure vessel at any stage until foaming, and may be introduced in several steps, but at least from the viewpoint of foamability. It is preferable to introduce some foaming agents into the pressure vessel before raising the temperature in the pressure vessel. For example, when adding a foaming agent containing carbon dioxide, (a) carrying out a step of accommodating a dispersion containing polyolefin resin particles, an aqueous medium, an inorganic dispersant and a dispersion aid in a pressure vessel. In addition, solid carbon dioxide (dry ice) may be charged into the pressure vessel, or (b) a dispersion containing polyolefin resin particles, an aqueous medium, an inorganic dispersant, and a dispersion aid. After the step of containing the pressure vessel in the pressure vessel, immediately after, during the temperature rise in the pressure vessel, or after the temperature rise in the pressure vessel, the step of releasing the dispersion into the low pressure region is carried out You may implement the process which introduce | transduces a gaseous or liquid carbon dioxide into a pressure-resistant container in any one of the previous steps. Or the method which combined these methods is also employable. From the viewpoints of foamability, small variation in magnification of the resulting polyolefin resin foamed particles, and small variation in bubble diameter, use of carbon dioxide and water in combination as a foaming agent is also one preferred embodiment.

The amount of the foaming agent added is not particularly limited and can be appropriately adjusted depending on the expansion ratio. The amount of the foaming agent added is preferably 0.1 to 50 parts by weight, more preferably 2 to 30 parts by weight, and most preferably 100 parts by weight of the polyolefin resin particles. Is 3 parts by weight or more and 20 parts by weight or less. If the amount of the foaming agent added is (a) less than 0.1 parts by weight, the expansion ratio tends to be difficult to develop, and if it exceeds (b) 50 parts by weight, the foamed polyolefin resin foam particles are broken and open bubbles There is a tendency to become.

In the method for producing polyolefin resin expanded particles according to an embodiment of the present invention, the “step of expanding the polyolefin resin particles in the presence of a foaming agent” is a one-stage expansion step, and the polyolefin resin expanded particles are: The first-stage expanded particles obtained in the first-stage expanded process are preferable. In this production method, since Ag-based zeolite is used, expanded particles having a bulk density of 20 g / L to 55 g / L and excellent in-mold foam moldability with a small environmental load by a one-stage foaming process. Can be obtained.

The method for producing expanded polyolefin resin particles according to an embodiment of the present invention can be said to be a production method for obtaining first-stage expanded particles having a bulk density of 20 g / L to 55 g / L.

The first stage expanded particles of the polyolefin resin may be further subjected to a foaming process (also called a multistage foaming process). Specifically, the pressure inside the particles is increased to atmospheric pressure or higher by pressurizing with an inorganic gas, and then using water vapor having a pressure of 0.02 MPa to 0.12 MPa, the particles are kept for at least 20 seconds. By performing the heat treatment, it is possible to obtain second-stage expanded particles of a polyolefin-based resin that are further expanded and have a higher expansion ratio. Thus, it is also possible to perform the multistage foaming process with respect to the obtained second-stage expanded particles of the polyolefin-based resin to obtain third-stage expanded particles of the polyolefin-based resin.

As described above, a production method including a multi-stage foaming step is also included in one embodiment of the present invention. Therefore, the second bullet expanded particle and the third stage expanded particle are also included in the scope of one embodiment of the present invention.

The foaming agent used in the foaming step may be, but is not limited to, water and / or carbon dioxide gas, air, nitrogen gas, etc. These foaming agents may be used individually by 1 type, and may use multiple types together. Such a foaming agent has a small environmental load and has no combustion risk. Carbon dioxide gas is most preferable as the foaming agent because low-bulk density expanded particles can be obtained more easily.

The method for producing polyolefin resin expanded particles according to an embodiment of the present invention may be as follows. That is, a step of dispersing the polyolefin resin particles in a dispersion medium together with a foaming agent in a container, a step of heating the container to a temperature equal to or higher than a softening temperature of the polyolefin resin particles, and pressurizing the container, Releasing the dispersion medium in which the polyolefin resin particles and the foaming agent are dispersed into a pressure region lower than the internal pressure of the container to obtain polyolefin resin foam particles, and the polyolefin resin particles include: The polyolefin resin composition comprises 0.2 to 3.0 parts by weight of Ag-based zeolite with respect to 100 parts by weight of the polyolefin-based resin, and the polyolefin resin expanded particles have a bulk density of 20 g / L to 55 g. / L, and the average particle diameter of the Ag-based zeolite is 1.0 μm to 10.0 μm. Manufacturing method.

<Polyolefin-based resin foam and production method thereof>
A foamed molded article of polyolefin resin according to an embodiment of the present invention is the polyolefin resin foamed particle described in the section of [Polyolefin resin foamed particle] or the method for producing the polyolefin resin foamed particle. The polyolefin resin foamed particles produced by the production method described above are filled in a mold and then foam-molded in the mold. Since the polyolefin resin foam molded body according to an embodiment of the present invention has the above-described configuration, it is lightweight, has a low environmental load, and has excellent in-mold foam moldability.

In one embodiment of the present invention, a foamed molded article of polyolefin resin can be obtained by performing the following in-mold foam molding. That is, the polyolefin resin expanded particles obtained in the above-described form are filled in a mold and heated with water vapor or the like to fuse the expanded particles.

As an in-mold foam molding method, for example,
1) Pressurizing the polyolefin resin foam particles with an inorganic gas (for example, air or nitrogen gas, carbon dioxide gas, etc.), impregnating the polyolefin resin foam particles with the inorganic gas, and applying a predetermined internal pressure to the polyolefin resin foam particles. A method of filling the mold and heat-sealing with water vapor,
2) A method of compressing polyolefin resin foam particles with gas pressure and filling the mold in a state where the internal pressure of the particles is increased, and heat-sealing with water vapor, or
3) A method in which polyolefin resin expanded particles are filled in a mold and heat-sealed with water vapor without any pretreatment can be used.

For example, in the case of 1), air pressure is preliminarily pressurized in a pressure-resistant container, air is press-fitted into the polypropylene resin foam particles, and the foam particle internal pressure is set to about 0.08 MPa (absolute pressure) or more and 0.3 MPa (absolute pressure) or less. The foaming ability is imparted by this, and it is filled in a molding die that can be closed but cannot be sealed, and steam is used as a heating medium at a pressure of about 0.05 MPa (gauge pressure) to 0.4 MPa (gauge pressure). Molding is performed with a heating steam pressure for about 1 second to 120 seconds or less, and the polypropylene resin foamed particles are fused to each other. Thereafter, the molding mold is taken out of the foamed molded product in the mold by water cooling. By cooling to such an extent that deformation can be suppressed, a polypropylene resin-in-mold foam-molded product can be obtained. From the viewpoint that the surface properties, mechanical properties, dimensional stability, etc. of the obtained foamed polypropylene resin mold are good, the foamed particle internal pressure is 0.1 MPa (absolute pressure) or more and 0.25 MPa (absolute pressure) or less. The heating water vapor pressure is preferably 0.05 MPa (gauge pressure) or more and 0.25 MPa (gauge pressure) or less, and the heating time is preferably 5 seconds or more and 60 seconds or less.

Since the in-mold foam-molded article of the polyolefin resin thus obtained has excellent in-mold moldability, a buffer packaging material, a recoverable container, a heat retaining transport container (for example, a transport box for fresh fish and shellfish, The present invention can be applied to uses such as a take-out transport box and the like, and automobile parts (for example, a tool box and a floor core material). According to an embodiment of the present invention, it is possible to reduce the environmental load during the manufacturing operation.

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

[1] Foamed particles obtained by foaming polyolefin-based resin particles with a foaming agent, wherein the polyolefin-based resin particles contain a polyolefin-based resin and an Ag-based zeolite as an additive, and the Ag-based particles The average particle diameter of the zeolite is 1.0 μm to 10.0 μm, and the content of the Ag zeolite is 0.2 parts by weight to 3.0 parts by weight with respect to 100 parts by weight of the polyolefin resin. A polyolefin resin expanded particle, wherein the expanded resin has a bulk density of 20 g / L to 55 g / L.

[2] The polyolefin resin foamed particles according to [1], wherein the foaming agent is water and / or carbon dioxide gas.

[3] The polyolefin resin foamed particles according to [1] or [2], wherein the foamed particles have an average cell diameter of 60 μm to 250 μm.

[4] The polyolefin according to any one of [1] to [3], wherein the polyolefin resin is selected from a resin containing a polypropylene resin and / or a polyethylene resin Resin foam particles.

[5] In a method for producing a polyolefin resin foamed particle comprising a step of foaming a polyolefin resin particle in the presence of a foaming agent, the polyolefin resin particle is based on 100 parts by weight of the polyolefin resin, based on Ag zeolite 0. The polyolefin-based resin composition containing 2 to 3.0 parts by weight of the polyolefin-based resin foamed particles has a bulk density of 20 g / L to 55 g / L, and the average particle size of the Ag-based zeolite is A method for producing expanded polyolefin resin particles, characterized by being 1.0 μm to 10.0 μm.

[6] The “step of foaming the polyolefin resin particles in the presence of a foaming agent” is a one-stage foaming step, and the polyolefin resin foam particles are the first-stage foamed particles obtained in the first-stage foaming step. The method for producing expanded polyolefin resin particles according to [5], wherein

[7] The method for producing expanded polyolefin resin particles according to [5] or [6], wherein the foaming agent is water and / or carbon dioxide gas.

[8] The method for producing foamed polyolefin resin particles according to any one of [5] to [7], wherein the foamed particles have an average cell diameter of 60 μm to 250 μm.

[9] Polyolefin resin expanded particles according to any one of [1] to [4], or a polyolefin resin produced by the production method according to any one of [5] to [8] A foamed molded article of polyolefin resin, which is obtained by filling foamed particles into a mold and then foam-molding in the mold.

[10] Use of zeolite used in the production of polyolefin resin expanded particles, wherein the zeolite is an Ag zeolite, and the polyolefin resin is selected from a resin containing a polypropylene resin and / or a polyethylene resin. In the production of polyolefin resin foamed particles, the polyolefin resin foamed particles obtained by foaming the polyolefin resin have a bulk density of 20 g / L to 55 g / L. Use of zeolite used.

[11] The average particle diameter of the Ag-based zeolite is 1 μm to 10 μm, and the Ag-based zeolite contains 0.2 to 3.0 parts by weight with respect to 100 parts by weight of the polyolefin-based resin. Use of the zeolite used for manufacture of the polyolefin resin expanded particle as described in [10], which is characterized.

The following examples further illustrate one embodiment of the present invention, but are not limited thereto.

Hereinafter, evaluation methods used in Examples, Comparative Examples, and Reference Examples will be described.

<Moisture content>
The foamed particles immediately after foaming were used to blow off water adhering to the surface of the foamed particles with an air stream to dehydrate the foamed particles. Thereafter, the weight (W1) of the expanded particles was measured. Separately, the weight (W2) after the foamed particles were dried in an oven at 80 ° C. for 12 hours was measured. The water content was calculated from the following formula (1).
Moisture content (%) = (W1-W2) / W2 × 100 (1)
<Measurement of bulk density>
The internal volume (internal volume V [L]) of the container was measured at 23 ° C. under standard atmospheric pressure (0.1 MPa). Thereafter, the obtained foamed particles were put in the container, and the container was filled with the foamed particles while vibrating the container for 30 seconds with a vibrator. The expanded particles are placed so that the upper surface of the expanded particles is higher than the upper end surface of the container, and after filling the expanded particles, the upright plate is placed so that the upper end surface of the container and the surface of the expanded particles are flush with each other. The upper end surface of the container was scraped off. Next, the weight W [g] of the expanded particles remaining in the container was measured. The bulk density of the polyolefin resin expanded particles at 23 ° C. and 0.1 MPa (standard atmospheric pressure) was calculated by the formula (2).
Bulk density (g / L) = W ÷ V (2)
<Average bubble diameter>
Cut almost the center of the polyolefin resin foam particles so that the cellular membrane (cell membrane) of the polyolefin resin foam particles is not destroyed, and observe the cut surface using a microscope [Keyence: VHX Digital Microscope] Observation photographs were taken. In a microscopic observation photograph, a line segment corresponding to a length of 1000 μm was drawn on the portion excluding the surface layer part, the number of bubbles n passing through the line segment was measured, and the bubble diameter was calculated as 1000 / n (μm). . The same operation was performed with 10 expanded particles, and the average value of the calculated cell diameters was defined as the average cell diameter of the polyolefin resin expanded particles.

<Beautiful surface of molded product>
A 350 mm long x 450 mm wide surface of the obtained in-mold foam-molded product was visually observed, and surface aesthetics were judged according to the following criteria.
◎ (Beautiful surface appearance): No wrinkles and almost no intergranularity ○ (Surface appearance is good): Some wrinkles and intergranularity are seen △ (Surface appearance is acceptable): Slight wrinkles, intergranular but sink No x (surface appearance is unacceptable): Wrinkles or sink marks are conspicuous on the surface.
Note that “sink” means a dent on the surface and is sometimes referred to as “sink mark”.

<Dimensional shrinkage of molded product>
The length of the major axis (450 mm direction of the mold) was measured using a digital caliper (manufactured by Mitutoyo) for the obtained in-mold foam molded body to be evaluated. The dimension of the corresponding mold was set to L0, the dimension of the foamed molded product was set to L1, and the dimensional shrinkage ratio for the mold was calculated by the following formula (3), and evaluated according to the following criteria.
Dimensional shrinkage for mold = (L0-L1) / L0 x 100 (3)
A: Dimensional shrinkage with respect to the mold is 3.5% or less.
○: The dimensional shrinkage ratio with respect to the mold exceeds 3.5% and is 5% or less.
X: The dimensional shrinkage ratio with respect to the mold exceeds 5%.

<Fusing rate of molded product>
The fusion rate of the in-mold foam molded product is the ratio of the number of foam particles in which material destruction has occurred in the foam particles appearing on the cut surface obtained by cutting the in-mold foam molded product. Specifically, after cutting about 10 mm into the in-mold foam molded product along the thickness direction of the foam molded product with a utility knife, the in-mold foam molded product is broken, the fracture surface is observed, and the fracture surface is observed. The number (b) of the expanded particles present in the material and the number (b) of the expanded particles in which the material breakage occurred were measured, and the ratio (b / n) of (b) and (n) was expressed as a percentage. (%).
Those with a fusion rate of 60% or more are accepted and those with a fusion rate of less than 60% are rejected.

<CODcr of waste water>
When the polyolefin resin particles are heated to a temperature higher than the softening point temperature of the polyolefin resin particles and then the dispersion in the pressure vessel is discharged to a pressure range lower than the internal pressure of the pressure vessel to foam the polyolefin resin particles, they are discharged together with the foam particles. The COD value of the waste water was measured based on ISO 6060 standard.

In the examples, comparative examples and reference examples, the ones used were as follows, and were used without being particularly purified.

In the examples, comparative examples and reference examples, a polypropylene resin was used as the polyolefin resin. The polypropylene resin used was obtained from a manufacturer (Nippon Polypro Co., Ltd., Sun Allomer, Prime Polymer Co., Ltd., LG Chemical, Borealis, etc.) as a commercial product.

Example 1
[Preparation of polyolefin resin particles]
Ag zeolite (manufactured by Fuji Chemical Co., Ltd., BM) with an average particle size of 2 μm per 100 parts by weight of polypropylene resin (manufactured by Prime Polymer Co., Ltd., ethylene content 3.0% by weight, MI = 6 g / 10 min, melting point 144 ° C.) -102 NS (hereinafter abbreviated as A) 0.5 parts by weight was dry blended. Thereafter, the mixture obtained by dry blending is supplied to a twin-screw extruder, melt-kneaded at a cylinder temperature of about 220 ° C., and is formed into a strand shape from a cylindrical die having a diameter of 1.6 mm installed at the tip of the extruder. And then cooled with water and cut with a cutter to obtain polypropylene resin particles. The average particle weight of the polypropylene resin particles was 1.2 mg.

[Production of polyolefin resin expanded particles]
In a pressure-resistant container having a capacity of 0.3 m ³ , 100 parts by weight (80 kg) of the obtained polypropylene resin particles, 200 parts by weight of water, and tricalcium phosphate (made by Taihei Chemical Sangyo Co., Ltd.) 0.6 as a hardly water-soluble inorganic compound Add 0.04 parts by weight of sodium alkanesulfonate (Kao Co., Ltd., LATEMUL PS) as a surfactant and add 6 parts by weight of carbon dioxide gas as a foaming agent to the pressure vessel while stirring the charged raw materials. And a dispersion was prepared. The temperature in the pressure vessel was raised to 150 ° C., and the contents of the pressure vessel were heated to a foaming temperature of 150 ° C. Carbon dioxide gas was additionally injected to increase the pressure inside the pressure vessel to a foaming pressure of 3.0 MPa (gauge pressure), held at the foaming temperature and the foaming pressure for 30 minutes, and then the valve at the bottom of the pressure vessel was opened at 3.6 mmφ. Through the opening orifice of one hole, the content of the pressure vessel was discharged under atmospheric pressure to obtain expanded polypropylene resin particles. The water content of the obtained expanded polypropylene resin particles was measured. Then, the obtained polypropylene resin foamed particles were sent into a dryer, and water in the foamed particles was blown away with hot air of about 80 ° C. The bulk density and average cell diameter of the obtained polypropylene resin foamed particles were measured, and the results are shown in Table 1.

[Production of in-mold foam molded products]
The obtained foamed particles were put into a pressure vessel, pressurized with air to an air pressure of about 0.2 MPa (absolute pressure), filled into a 450 mm × 350 mm × 50 mm mold, and 0.30 MPa ( In-mold foam molding was performed with saturated water vapor (gauge pressure) to obtain an in-mold foam molded article. Furthermore, after leaving the obtained in-mold foam molding for about 1 hour under atmospheric pressure, it is dried under atmospheric pressure for 24 hours using an oven set at 75 ° C. An inner foamed molded product was obtained. The obtained polypropylene resin foamed molded article was evaluated for surface aesthetics, measured for the dimensional shrinkage of the molded article and the fusion rate of the molded article, and the results are shown in Table 1.

Example 2
Resin particles were prepared in the same manner as in Example 1 except that silver-zinc zeolite having an average particle diameter of 1.5 μm (manufactured by Fuji Chemical Co., Ltd., BM-102NSC, hereinafter abbreviated as B) was used instead of A. Production of resin foam particles and in-mold foam molding were performed. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Example 3
Resin particles, resin foam particles, and in-mold foam molding were performed in the same manner as in Example 1, except that 0.2 parts by weight of A was used instead of 0.5 parts by weight of A. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Example 4
Resin particle production, resin foam particle production, and in-mold foam molding were performed in the same manner as in Example 1 except that 1.0 part by weight of A was used instead of 0.5 part by weight of A. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Example 5
Resin particles, resin foam particles, and in-mold foam molding were performed in the same manner as in Example 1 except that 2.5 parts by weight of A was used instead of 0.5 parts by weight of A. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Example 6
Resin particles were produced, resin foam particles were produced, and in-mold foam molding was performed in the same manner as in Example 1 except that 3.0 parts by weight of A was used instead of 0.5 parts by weight of A. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Comparative Example 1
In place of A, 0.1 part by weight of talc (manufactured by Hayashi Kasei Co., Ltd., TALCAN PAWDER PK-S) was used. Foam molding was performed. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Comparative Example 2
Resin particles and foamed resin particles were prepared in the same manner as in Example 1 except that synthetic zeolite having an average particle size of 3 μm (Zeostar NA100P, hereinafter abbreviated as C) was used instead of A. And in-mold foam molding was performed. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Comparative Example 3
Preparation of resin particles and resin expanded particles in the same manner as in Example 1 except that natural zeolite having an average particle size of 2 μm (SP # 600, hereinafter abbreviated as D) was used instead of A And in-mold foam molding were performed. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Comparative Example 4
Resin in the same manner as in Comparative Example 2 except that 3 parts by weight of C and 0.1 parts by weight of talc (TALCAN PAWDER PK-S, manufactured by Hayashi Kasei Co., Ltd.) were used instead of 0.5 parts by weight of C. Preparation of particles, preparation of resin foam particles, and in-mold foam molding were performed. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Comparative Example 5
Instead of A, the production of resin particles, the production of resin foam particles, and in-mold were performed in the same manner as in Example 1 except that Ag zeolite (commercially available, hereinafter abbreviated as E) having an average particle size of 0.3 μm was used. Foam molding was performed. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Comparative Example 6
Resin particles, resin foam particles, and in-mold foam molding were prepared in the same manner as in Example 1 except that Ag zeolite (commercially available, hereinafter abbreviated as F) having an average particle diameter of 20 μm was used instead of A. went. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

Reference example 1
Instead of A, 0.2 part by weight of glycerin (manufactured by LION Co., Ltd., glycerin # 300, hereinafter abbreviated as G) and 0.1 part by weight of talc (manufactured by Hayashi Kasei Co., Ltd., TALCAN PAWDER PK-S) were used. Except that, resin particles were produced, resin foam particles were produced, and in-mold foam molding was performed in the same manner as in Example 1. The evaluation results for the polypropylene resin expanded particles and the polypropylene resin expanded molded article are shown in Table 1.

In Examples 1 to 6, lightweight foamed particles with a bulk density of 55 g / L or less were obtained, and when the polyolefin resin foamed particles according to one embodiment of the present invention were used, the appearance was good. Thus, it was found that a foamed molded product free from wrinkles could be obtained, and that the dimensional shrinkage rate of the molded product and the fusion rate of the molded product were both good. Moreover, the CODcr of waste water when foaming into expanded particles is as low as 200 ppm or less, and it was found that the environmental load was reduced.

In Comparative Example 1, since neither a hydrophilic organic compound nor an Ag-based zeolite was added, the bulk density of the polyolefin resin expanded particles could not be within the range of one embodiment of the present invention, and the product (expanded particles) It is found that the unit volume weight of the molded body is obviously higher than that of the product (foamed particles) according to one embodiment of the present invention, and the merit of lightness is not expressed. It was.

In Comparative Examples 2 and 4, synthetic zeolite was used. When the amount of the synthetic zeolite added is low, the bulk density of the polyolefin resin expanded particles is high, the weight cannot be reduced, and the dimensional shrinkage rate and the fusion rate of the molded article are not good. In order to lower the bulk density of the polyolefin resin expanded particles, Comparative Example 4 increased the amount of synthetic zeolite added. However, in Comparative Example 4, the open-cell ratio of the expanded particles is increased, and as a result, the dimensional shrinkage ratio of the obtained in-mold foam-molded product is increased, surface wrinkles become conspicuous, and surface appearance (surface properties) ) Got worse.

From the comparison between Examples 1 and 2 and Comparative Examples 2 and 3, when the addition amount of the additive is the same, the polyolefin obtained after adding the Ag-based zeolite as compared with the case of adding the synthetic zeolite or natural zeolite It was found that the resin-based resin expanded particles are superior in performance such as appearance of the molded product, dimensional shrinkage, and fusion rate of the molded product.

Examples 1 and 2 and Comparative Examples 5 and 6 were all the same except for the difference in the particle size of Ag zeolite. From the comparison between Examples 1 and 2 and Comparative Examples 5 and 6, when the average particle size range of the Ag-based zeolite required in one embodiment of the present invention is satisfied, the appearance is good and there are no wrinkles. It was found that polyolefin-based resin foamed particles can be obtained in which the foamed molded article and the dimensional shrinkage ratio of the molded article and the fusion rate of the molded article are both good.

From the comparison between Examples 1 to 6 and Reference Example 1, when foaming into expanded particles, the CODcr of wastewater is 200 ppm or less in Examples 1 to 6, but the CODcr of wastewater is as high as 700 ppm in Reference Example 1, and the wastewater The COD reduction process was at a necessary level. When the polyolefin resin foamed particles according to one embodiment of the present invention are used, the hydrophilic organic compound and the foam nucleating agent are used even when the hydrophilic organic compound and the foam nucleating agent that increase the environmental load are not used. It was found that a polyolefin resin foam molded article having the same performance as that obtained can be obtained.

According to one embodiment of the present invention, it is possible to provide polyolefin resin foamed particles that are lightweight, have a low environmental impact, and have excellent in-mold foam moldability. Therefore, an embodiment of the present invention includes a buffer wrapping material, a recoverable container, a heat retaining transport container (for example, a transport box for fresh seafood, a transport box for takeout), an automobile part (for example, a tool box, a floor core material). Etc.) can be suitably used.

Claims

Expanded particles obtained by foaming polyolefin resin particles with a foaming agent,
The polyolefin resin particles contain a polyolefin resin and an Ag zeolite that is an additive,
The average particle diameter of the Ag-based zeolite is 1.0 μm to 10.0 μm, and the content of the Ag-based zeolite is 0.2 parts by weight to 3.0 parts by weight with respect to 100 parts by weight of the polyolefin resin. Yes,
Polyolefin resin foamed particles, wherein the foamed particles have a bulk density of 20 g / L to 55 g / L.
2. The polyolefin-based resin expanded particles according to claim 1, wherein the foaming agent is water and / or carbon dioxide gas.
3. The polyolefin-based resin expanded particles according to claim 1 or 2, wherein an average cell diameter of the expanded particles is 60 μm to 250 μm.
The polyolefin resin expanded particles according to any one of claims 1 to 3, wherein the polyolefin resin is selected from a resin containing a polypropylene resin and / or a polyethylene resin.
In a method for producing a polyolefin resin foamed particle comprising a step of foaming a polyolefin resin particle in the presence of a foaming agent,
The polyolefin resin particles consist of a polyolefin resin composition containing 0.2 parts by weight to 3.0 parts by weight of an Ag zeolite with respect to 100 parts by weight of the polyolefin resin.
The polyolefin resin expanded particles have a bulk density of 20 g / L to 55 g / L,
The method for producing foamed polyolefin resin particles, wherein the Ag-based zeolite has an average particle size of 1.0 μm to 10.0 μm.
The “step of foaming polyolefin resin particles in the presence of a foaming agent” is a one-stage foaming step,
The method for producing expanded polyolefin resin particles according to claim 5, wherein the expanded polyolefin resin particles are first-stage expanded particles obtained in the first-stage expansion step.
The method for producing expanded polyolefin resin particles according to claim 5 or 6, wherein the foaming agent is water and / or carbon dioxide gas.
The method for producing polyolefin resin foamed particles according to any one of claims 5 to 7, wherein the foamed particles have an average cell diameter of 60 袖 m to 250 袖 m.
Filling the mold with the expanded polyolefin resin particles according to any one of claims 1 to 4 or the expanded polyolefin resin particles produced by the production method according to any one of claims 5 to 8. Then, a polyolefin-based resin foam-molded product obtained by foam-molding in a mold.
The use of zeolite for the production of polyolefin resin expanded particles,
The zeolite is an Ag-based zeolite,
The polyolefin resin is selected from resins including a polypropylene resin and / or a polyethylene resin,
Use of zeolite used for the production of polyolefin resin foamed particles, wherein the polyolefin resin foamed particles obtained by foaming the polyolefin resin have a bulk density of 20 g / L to 55 g / L.
The average particle diameter of the Ag-based zeolite is 1 μm to 10 μm, and the Ag-based zeolite contains 0.2 to 3.0 parts by weight with respect to 100 parts by weight of the polyolefin resin. Use of the zeolite used for manufacture of the polyolefin-type resin expanded particle of Claim 10.