Multilayer molded body

Abstract

To provide a multilayer molded article containing a biodegradable resin that has a good appearance, low leaching of biodegradable components and impurities derived from raw materials, and is lightweight. [Solution] The outer layer is a non-foamed layer made of petroleum-derived polyolefin resin alone or a mixed resin of petroleum-derived polyolefin resin and plant-derived polyolefin resin, in the latter case, the proportion of plant-derived polyolefin resin is 45 parts by weight or less, and the inner layer is a foamed layer made of a mixed resin of petroleum-derived polyolefin resin and plant-derived polyolefin resin, with the proportion of plant-derived polyolefin resin being 10 to 100 parts by weight.

Description

[Technical Field] 【0001】 This invention relates to a multilayer molded article. [Background technology] 【0002】 Currently, plastic products are widely used around the world, but the disposal of plastic waste is a problem. For example, it is said that it takes about 400 years for plastic to completely decompose when discarded in the soil. In addition, burning plastic often releases toxic gases, leading to air and soil pollution. Furthermore, it has been pointed out that the carbon dioxide produced by incineration contributes to global warming. 【0003】 Incidentally, polylactic acid (PLA) is widely studied as a bio-based polymer with high strength and high modulus of elasticity. However, PLA also has several limiting properties that hinder its use in a wider range of applications, including brittleness, low thermal stability, low elongation at fracture, low melt strength, and moisture sensitivity. Therefore, much research has been done on ways to improve the properties of PLA. This research has included, for example, the addition of small molecule plasticizers, blending with other ductile polymers, copolymerization, and the use of nanocomposite materials to improve the toughness and ductility of PLA and other corresponding materials. While these strategies have certainly resulted in improvements in ductility and toughness, they often result in a decrease in strength and modulus of elasticity. 【0004】 As for plastic products, packaging containers and packing materials that are foamed to provide features such as heat insulation and lightweight properties are widely used, and in order to address the aforementioned problems, there is a trend to replace the material from thermoplastic synthetic resins such as polystyrene to biodegradable resins or resins containing biodegradable substances. For example, a foaming resin composition has been proposed that contains 100 parts by mass of a mixture of 10% or more by mass of modified starch and 90% or less by mass of unprocessed starch, 10% or less by mass of biodegradable resin, 10 to 30% by mass of water, and 0.01 to 5 parts by mass of inorganic filler (see Patent Document 1). According to this composition, since it is biodegradable, a foam (foamed product) that takes environmental issues into consideration can be provided. 【0005】 However, while the foam described in Patent Document 1 addresses environmental issues, the technology involves foaming the foam (molded body) with water mixed into the resin composition, which can result in a rough surface and uneven thickness. Therefore, there is still room for improvement in terms of maintaining a consistent level of quality (surface roughness and impact strength) and preventing the leaching of odors, biodegradable components, and impurities. 【0006】 Furthermore, Patent Document 2 proposes a laminated sheet comprising a foamed layer containing a mixed resin of polystyrene resin and polyolefin resin, a first non-foamed layer formed of polystyrene resin and laminated on a first surface of the foamed layer, and a second non-foamed layer formed of polyolefin resin and laminated on a second surface different from the first surface of the foamed layer, wherein the foamed layer contains at least one of biomass polyethylene or biomass polypropylene as the polyolefin resin. Patent Document 2 also states that the amount of drawdown (the amount the sheet sags in the direction of gravity due to thermal deformation) can be reduced by keeping the bonding strength between the foamed layer and the non-foamed layer within an appropriate range. Moreover, Patent Document 2 states that because the foamed layer contains biomass polyethylene or biomass polypropylene, it contributes to achieving Sustainable Development Goal 13, "Take urgent action to combat climate change," etc., advocated by the United Nations. 【0007】 Meanwhile, on May 10, 2019, the United Nations made a landmark decision to protect people and the planet from hazardous chemicals and waste, including plastic waste. As of 2019, 100 million tons of plastic had been dumped into the ocean, the majority of which originated on land. Recycling such plastic products in the regeneration process is in accordance with the aforementioned UN decision, but because it is difficult to separate materials that are combined from multiple different materials, they are disposed of by methods other than recycling, such as landfill or incineration. However, this method cannot realize a circular economy centered on the Sustainable Development Goals (SDGs). 【0008】 Therefore, "monomaterialization," which involves manufacturing products composed of multiple different materials from a single material, is preferable because it contributes to material recycling. Compared to recycling methods (chemical recycling) that decompose plastic waste into hydrogen and carbon dioxide through heat or chemical treatment and then use these as raw materials to create other materials, material recycling requires significantly less energy to produce reusable materials. In this respect, the laminated sheet described in Patent Document 2 contains a heterogeneous mixture of polystyrene resin and polyolefin resin, making it difficult to recycle and thus unable to contribute to the realization of a circular economy. [Prior art documents] [Patent Documents] 【0009】 [Patent Document 1] Japanese Patent Publication No. 2010-260923 [Patent Document 2] Patent No. 7470468 specification [Overview of the Initiative] [Problems that the invention aims to solve] 【0010】 In view of the above problems, the object of the present invention is to provide a multilayer molded article containing a plant-derived resin that does not have the drawbacks of the prior art, has a good appearance, has little leaching of biodegradable components and impurities derived from raw materials, and is lightweight. Furthermore, the object of the present invention is to provide a multilayer molded article that contributes to the realization of a circular economy. [Means for solving the problem] 【0011】 The first invention of this application, which aims to achieve the above objective, is characterized in that the outer layer is a non-foamed layer made of a petroleum-derived polyolefin resin alone or a mixed resin of a petroleum-derived polyolefin resin and a plant-derived polyolefin resin, wherein in the latter case, the proportion of the plant-derived polyolefin resin is 45 parts by weight or less, and the inner layer is a foamed layer made of a mixed resin of a petroleum-derived polyolefin resin and a plant-derived polyolefin resin, wherein the proportion of the plant-derived polyolefin resin is 10 to 100 parts by weight. 【0012】 The second invention of this application is characterized in that, in the first invention of this application, an innermost layer is provided inside the inner layer, the innermost layer is a non-foaming layer, and the innermost layer consists of a petroleum-derived polyolefin resin alone or a mixed resin of a petroleum-derived polyolefin resin and a plant-derived polyolefin resin, and in the latter case of the mixed resin, the proportion of the plant-derived polyolefin resin is 5 to 30 parts by weight. 【0013】 The third invention of this application is characterized in that, in the first or second invention of this application, the polyolefin resin is obtained by polymerizing a single olefin. [Effects of the Invention] 【0014】 According to the first invention of this application, the outer layer is made of petroleum-derived polyolefin resin alone, or the ratio of plant-derived polyolefin resin in a mixed resin is appropriate, resulting in a good appearance, low leaching of impurities, and cleanliness. The inner layer is a foamed layer, resulting in lightness. According to the second invention of this application, the innermost layer inside the inner layer is made of petroleum-derived polyolefin resin alone, or the ratio of plant-derived polyolefin resin in a mixed resin is appropriate, resulting in a good appearance, low leaching of impurities, and cleanliness. By using monomaterialization according to the third invention of this application, material recycling can be achieved, contributing to the realization of a circular economy. [Brief explanation of the drawing] 【0015】 [Figure 1] This diagram illustrates a method for cutting out samples to determine the cleanliness of a multilayer molded body. [Figure 2]It is a plan view of an example of a lead frame. [Figure 3] It is a cross-sectional view of an example of a semiconductor package. 【Mode for Carrying Out the Invention】 【0016】 Hereinafter, embodiments of the present invention will be described in detail. 【0017】 The petroleum-derived polyolefin resin preferably contains polyethylene, and examples thereof include high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE) produced from fossil raw materials such as naphtha. Further, examples of petroleum-derived polyolefins include polyvinyl acetate (EVA), ethylene ethyl acrylate (EEA), polypropylene (PP), poly-1-butene, 1,2-polybutadiene and its hydrogenated product, polyisobutylene, random copolymers or block copolymers of propylene with ethylene and / or 1-butene in any ratio, polymethylpentene, cyclic polyolefins such as copolymers of cyclopentadiene with ethylene and / or propylene, and ethylene-propylene-diene terpolymers in which the diene component is 50% by weight or less in any ratio of ethylene to propylene, etc. 【0018】 The plant-derived polyolefin resin preferably contains polyethylene. Plant-derived polyethylene can be obtained by fermenting sugars contained in starch raw materials such as corn, sweet potato, wheat, and tapioca, and sugar raw materials such as sugarcane and sugar beet with a fermenting agent to produce ethanol, converting this ethanol to ethylene using a catalyst such as γ-alumina, and then obtaining plant-derived polyethylene from this ethylene through a conventional method such as a gas-phase polymerization method. 【0019】 When the outer layer is a non-foaming layer made of a mixed resin of petroleum-derived polyolefin resin and plant-derived polyolefin resin, it is preferable that the proportion of plant-derived polyolefin resin is 45 parts by weight or less. However, if the proportion of plant-derived polyolefin resin exceeds 45 parts by weight, the surface of the outer layer becomes rough and the appearance deteriorates. 【0020】 The inner layer is a foamed layer made of a mixed resin of petroleum-derived polyolefin resin and plant-derived polyolefin resin, and it is preferable that the proportion of plant-derived polyolefin resin is 10 to 100 parts by weight. A proportion of 10 parts by weight or more of plant-derived polyolefin resin can contribute to the reduction of carbon dioxide. On the other hand, if the proportion of plant-derived polyolefin resin exceeds 100 parts by weight, it becomes difficult to foam due to the influence of the plant-derived polyolefin resin, and there is a risk of foam bursting, which is undesirable. 【0021】 The innermost layer is located inside the inner layer, and the innermost layer is a non-foaming layer. When the innermost layer consists of a petroleum-derived polyolefin resin alone or a mixed resin of a petroleum-derived polyolefin resin and a plant-derived polyolefin resin, it is preferable that the proportion of plant-derived polyolefin resin in the latter mixed resin is 5 to 30 parts by weight. A proportion of 5 parts by weight or more of plant-derived polyolefin resin can contribute to the reduction of carbon dioxide. On the other hand, if the proportion of plant-derived polyolefin resin exceeds 30 parts by weight, it is undesirable because some impurities may leach out. 【0022】 The thickness of the outer non-foamed layer is preferably smaller than the thickness of the inner foamed layer in order to reduce the amount of petroleum-derived polyolefin resin used, maximize the foaming ratio, and reduce weight. In the case of a three-layer structure having an outer non-foamed layer, an inner foamed layer, and a second non-foamed layer inside the inner layer, the thickness of the outer non-foamed layer is preferably greater than the thickness of the second non-foamed layer in order to reduce weight further by increasing the foaming ratio and thickness of the foamed layer and making the non-foamed layer thinner. 【0023】 Methods for obtaining a foamed layer include extruding and foaming from an extruder using a physical foaming agent, foaming within a mold, foaming using a chemical foaming agent, and foaming using a pyrolysis-type chemical foaming agent. 【0024】 As physical blowing agents, volatile hydrocarbons such as propane, n-butane, isobutane, n-pentane, and isopentane; halogenated hydrocarbons such as dichlorodifluoromethane, 1,1,1-trifluoroethane, and methylene chloride; ethers such as diethyl ether and methyl ethyl ether; carbon dioxide; and nitrogen can be used. These may be used individually or in combination of two or more. Alcohol and water can also be used as blowing aids. Among these, carbon dioxide in a supercritical state is preferred in terms of safety and reducing the burden on the global environment. 【0025】 Examples of chemical foaming agents include azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide, azobisisobutyronitrile, barium azodicarboxylate, and bicarbonates such as sodium bicarbonate. These may be used individually or in combination of two or more. If necessary, using a foaming agent decomposition accelerator such as zinc oxide or zinc stearate is a preferred embodiment for obtaining a uniform foam. 【0026】 When foaming is performed using a pyrolysis-type chemical foaming agent, the resin may be crosslinked. Crosslinking the resin makes it less prone to bubble bursting and results in a foam with a beautiful appearance. Methods for crosslinking the resin include crosslinking with organic peroxides and crosslinking by ionizing radiation irradiation, but polyfunctional monomers may be included in the resin composition as needed. 【0027】 The foaming ratio of the foamed layer is preferably between 1.2 and 3.0. A foaming ratio of 1.2 or higher increases the proportion of air bubbles, thus achieving weight reduction. On the other hand, a foaming ratio exceeding 3.0 is undesirable because it makes the foam more prone to bursting. 【0028】 The cell diameter (bubble diameter) of the foamed layer is preferably 50 to 100 μm. In the polyolefin resin used in the present invention, by extrusion molding, microcells with a cell diameter of less than 50 μm cannot be formed by the chemical foaming method. A cell diameter of 50 μm or more results in a good appearance, while a cell diameter exceeding 100 μm is undesirable because it causes bubbles to burst, affecting the outer layer and resulting in a poor appearance. 【0029】 The foamed layer may contain inorganic fillers. Preferred inorganic fillers include talc, calcium carbonate, clay, precipitated barium sulfate, silica, kaolin, diatomaceous earth, calcium silicate, mica, alumina, aluminum sulfate, calcium sulfate, magnesium carbonate, carbon fiber, glass fiber, glass spheres, graphite, zeolite, and limestone. These may be used individually or in combination of two or more. Among these, talc is preferred in terms of rigidity and cost. 【0030】 The multilayer molded body of the present invention can be manufactured by general manufacturing methods for producing laminates, such as co-extrusion, T-die, casting, calendering, injection molding, and pressing. Applications of the multilayer molded body of the present invention include, for example, in automotive applications, interior materials such as doors, instrument panels, seat back garnishes, console boxes, ceilings, and floor mats, various insulators such as dash panel insulators and rear side trim insulators, trunk sides, and wheel well covers. It can also be used as a thermal insulation material for pipe covers, spiral hoses, long roofs, etc. It can also be used as a cushioning material for various mats such as desk mats and floor mats, and as cushioning material for paper tube cores. Furthermore, it can be used as a protective material for lead frames, which are important components used in the packaging of semiconductor devices (such as ICs and LSIs), supporting semiconductor chips and providing electrical connections to the outside. 【0031】 The multilayer molded article of the present invention may contain, as needed, conventional additives added to foam molding resin compositions, such as fillers, flame retardants, antioxidants, clearing agents, plasticizers, antistatic agents, compatibilizers, nucleating agents, ultraviolet absorbers, weathering agents, heat stabilizers, light stabilizers, binders, antiblocking agents, lubricants, neutralizing agents, crystallization accelerators, colorants, waterproofing agents, water repellents, antibacterial agents, antifogging agents, and impact resistance enhancers. [Examples] 【0032】 The following describes embodiments of the present invention, but this does not limit the present invention in any way, and various changes and modifications are possible without departing from the technical scope of the present invention. 【0033】 The following compounds were mixed in the formulations and amounts (parts by weight) shown in Table 1 below to obtain foamed resin compositions used for the production of multilayer molded articles in Examples 1-4 and Comparative Examples 1-2. Biopolyethylene 1: Polyethylene obtained from sugarcane through a fermentation process (product name "SHE150(HD)" manufactured by Plaschem, density 0.948 g / cm³) 3 MFR 1.0g / 10 min (190℃), Biomass ratio 94% Biopolyethylene 2: Polyethylene obtained from sugarcane through a fermentation process (product name "SEB853(LD)" manufactured by Plaschem, density 0.923 g / cm³) 3 MFR 2.7g / 10 min (190℃), Biomass ratio 95% Petroleum-derived LDPE: Petroleum-derived low-density polyethylene (product name "Sumikasen" manufactured by Sumitomo Chemical Co., Ltd., density 0.924 g / cm³) 3 MFR 2.0g / 10 minutes (190℃) Petroleum-derived HDPE: Petroleum-derived high-density polyethylene (product name "Suntech" manufactured by Asahi Kasei Corporation, density 0.963 g / cm³) 3 MFR 1.4g / 10 minutes (190℃) Foaming agent: Polystyrene, manufactured by Eiwa Kasei Co., Ltd., decomposition temperature 200℃ Pigment: Sumika Color Co., Ltd. product name "SUMIKA COLOR", white 【0034】 The resin compositions of the outer layer and the innermost layer shown in Table 1 were dry-blended and supplied to a single-screw extruder for the outer layer. The resin composition of the inner layer shown in Table 1 was supplied to a single-screw extruder for the inner layer. They were melt-kneaded at 250 °C respectively, and three-layer co-extrusion was carried out using a feed block. Then, they were cooled together with a metal mirror roll / matte-finished metal roll set at 30 °C to obtain a multilayer molded body with a three-layer structure having the configuration and properties shown in Table 1. 【0035】 In Table 1, the biomass ratio of the foam sheet was measured in accordance with "ASTM D6866 Method B". Specifically, the foam sheet was burned, and the CO2 generated by the combustion of the foam sheet was quantified. For the quantified CO2, the concentration of 14 C was measured using an accelerator mass spectrometer (AMS), and the biomass ratio was determined by comparing the concentration of 14 C in the CO2 in the atmosphere with the measured concentration of 14 C. Also, the expansion ratio was obtained by measuring the specific volume (cc / g) before and after foaming and calculating the ratio of the specific volume after foaming to the specific volume before foaming. 【0036】 In Table 1, the cleanliness was determined as follows. From each multilayer molded body, as shown in Fig. 1, a sample of about 200 cm 2 × 0.5 mm including the outer layer 1, the inner layer 2, and the innermost layer 3 was cut out. This sample was put into a polypropylene bag, 50 mL of ultrapure water was added, and after sealing, it was left standing in a constant-temperature water bath at 60 °C for 60 minutes. Then, the polypropylene bag was taken out of the constant-temperature water bath and allowed to cool to room temperature. The ultrapure water was taken out of the polypropylene bag, and the amount of ions eluted into the ultrapure water was determined by a suppressor-type ion chromatograph as described below. Chloride ions (Cl - ), nitrite ions (NO2 - ), nitrate ions (NO3 - ), sulfate ions (SO4 2- ), and phosphate ions (PO4 3-When measuring (Na), an ion chromatograph ICS-5000 manufactured by Nippon Dionex Co., Ltd. was used, with KOH (concentration mM, 0 min: 4.0, 17.5 min: 28.0, 20 min: 28.0) as the eluent, and "IonPacAG17C + IonPacAS17C" as the column, with a flow rate of 1.2 mL / min and a sample introduction volume of 10 μL. + ) and ammonium ions (NH4 + ) and potassium ions (K + When measuring the ions, we used the "Ion Chromatograph ICS-5000+" manufactured by Nippon Dionex Co., Ltd., with 20 mM methanesulfonic acid as the eluent and "IonPacCG12A+IonPacCS12A" as the column, with a flow rate of 1.0 mL / min and a sample introduction volume of 10 μL. As a result, we obtained the results shown in Tables 2 and 3 below. 【0037】 [Table 1] 【0038】 [Table 2] 【0039】 [Table 3] 【0040】 As shown in Table 2, the multilayer molded articles of Examples 1 to 4 exhibited less elution of inorganic ions and were cleaner compared to the multilayer molded articles of Comparative Examples 1 and 2 shown in Table 3. Furthermore, visual inspection of the multilayer molded articles of Examples 1 to 4 revealed that the outer layer surface was smooth. However, in Comparative Example 1, since the outer layer, inner layer, and innermost layer are all made of biopolyethylene, it does not foam properly and a large amount of inorganic ions are leached out, indicating that it is not clean. Furthermore, a visual inspection of the multilayer molded body of Comparative Example 1 revealed that the surface of the outer layer was rough. Furthermore, since the multilayer molded body of Comparative Example 2 contains biopolyethylene in all three layers—outer, inner, and innermost—it is clear that it is not clean due to the large amount of inorganic ions that leach out. In addition, a visual inspection of the multilayer molded body of Comparative Example 2 revealed that the outer layer surface was rough. 【0041】 The multilayer molded body of the present invention can be used as a component to prevent damage to precision electronic components, such as lead frames, during transport. A lead frame is a component in semiconductor packages such as ICs and LSIs that supports and fixes semiconductor chips while simultaneously connecting to external wiring with multiple external connection terminals, or "outer leads," that protrude from the package like the legs of a centipede. A finished semiconductor package of this form is also called a "lead frame package," and the outer leads exposed from the resin are simply called "leads." A plan view of an example of a lead frame is shown in Figure 2, and a cross-sectional view of an example of a semiconductor package is shown in Figure 3. 【0042】 In Figures 2 and 3, 4 is the inner lead, 5 is the outer lead, 6 is the die pad, 7 is the frame, 8 is the dam bar, 9 is the semiconductor chip, 10 is the electrode pad, 11 is the resin package, and 12 is the bonding wire. Lead frames are generally made of thin sheets of materials with excellent electrical conductivity, mechanical strength, thermal conductivity, and corrosion resistance, such as Cu alloy or iron alloy. These thin sheets are subjected to press processing such as punching, drawing, and bending to form the "die pad" that supports and fixes the semiconductor chip, the "inner lead" that connects to the semiconductor chip, and the "outer lead" that connects to the external wiring. In addition to machining, the manufacturing process of lead frames includes surface treatment processes such as etching and plating. Lead frames are used in packages for integrated circuits such as ICs and LSIs, as well as for discrete semiconductors, photocouplers, LEDs, and more. In recent years, with the miniaturization of electronic devices and the increasing density of electronic circuits, extremely high precision is required for lead frames and their connections. Naturally, damage to precision electronic components such as lead frames during transport is absolutely unacceptable. Therefore, by protecting precision electronic components such as lead frames by sandwiching them on both sides with the multilayer molded body of the present invention, damage to precision electronic components such as lead frames during transport can be prevented. [Explanation of Symbols] 【0043】 1 outer layer 2. Inner layer 3. Innermost layer 4. Inner Lead 5. Outer lead 6 Die Pads 7 Frame section 8 Dam Bar 9 Semiconductor chips 10 electrode pads 11. Resin packaging 12 Bonding wires

Claims

[Claim 1] A multilayer molded article characterized in that the outer layer is a non-foamed layer made of petroleum-derived polyolefin resin alone or a mixed resin of petroleum-derived polyolefin resin and plant-derived polyolefin resin, in the latter case, the proportion of plant-derived polyolefin resin is 45 parts by weight or less, and the inner layer is a foamed layer made of a mixed resin of petroleum-derived polyolefin resin and plant-derived polyolefin resin, with the proportion of plant-derived polyolefin resin being 10 to 100 parts by weight. [Claim 2] The multilayer molded article according to claim 1, characterized in that it has an innermost layer inside the inner layer, the innermost layer is a non-foaming layer, and the innermost layer consists of a petroleum-derived polyolefin resin alone or a mixed resin of a petroleum-derived polyolefin resin and a plant-derived polyolefin resin, and in the latter case, the ratio of the plant-derived polyolefin resin is 5 to 30 parts by weight. [Claim 3] The multilayer molded article according to claim 1 or 2, characterized in that the polyolefin resin is obtained by polymerizing a single olefin.

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