JP7788239B2 - Recycled plastic composition - Google Patents

Description

The present invention relates to a recycled plastic composition containing waste plastic.

Plastics are widely used for a variety of purposes due to their properties, such as ease of molding, light weight, and moderate durability, resulting in the generation of large amounts of waste plastic (plastic waste). From the perspectives of resource conservation and environmental protection, there is a desire to expand the recycling of waste plastic. However, recycled plastic products obtained from recycled waste plastic have the problem of generating an odor due to components that have become ingrained in the waste plastic, even when the waste plastic is washed and used. For this reason, there has been a demand for a way to remove the odor from recycled plastic.

As a technology for deodorizing odors from recycled plastics, Patent Document 1 discloses the production of recycled plastic molded products that maintain sufficient strength for practical use while eliminating odors such as pungent odors and the smell of food waste by adding 1 to 5% by weight of calcium hydroxide to waste plastic. Patent Document 2 discloses the prevention of odors caused by natural fibers in plastic molded products by adding calcium oxide/calcium hydroxide. Patent Document 3 discloses the reduction of odors from exhaust gases when heating waste materials such as plastics by heating the waste in the presence of steam or by mixing steam with the exhaust gas after heating and then cooling it to condense. Patent Document 4 discloses the deodorization of used foam molded products such as fish crates by (a) treating them with an aqueous solution of phosphoric acid, a water-soluble phosphate, or a mixture, or (b) treating them with steam. Patent Document 5 also teaches that a plastic material made by blending polyethylene and/or polypropylene, diatomaceous earth, iron oxide masterbatch, and lubricant, drying, and then heating and granulating it has flame retardant and deodorizing properties, and can also be recycled.

Japanese Patent Application Laid-Open No. 2007-210199 Japanese Patent Application Laid-Open No. 2002-194231 Japanese Patent Application Laid-Open No. 2001-162249 Japanese Patent Application Publication No. 6-322174 Japanese Patent Application Laid-Open No. 2018-28023

As mentioned above, recycling of waste plastics is widely desired, but there have been cases where the odors caused by waste plastics could not be sufficiently reduced.
There is also a demand for expanded recycling of used automobiles, and there is a desire to recycle ASR (Automobile Shredder Residue). However, ASR retains a distinctive odor even after being remolded through steam cleaning or the like, and further deodorization is required in order to apply it to various uses.

The objective of the present invention is to provide a recycled plastic composition containing waste plastics and having a highly reduced odor. In particular, the objective is to provide a recycled plastic composition in which the odor of waste plastics, which has an odor that cannot be removed by general deodorizing methods such as ASR, has been sufficiently reduced, and to provide a method for reducing the odor of waste plastics.

In light of the above situation, the inventors conducted extensive research and discovered that the above-mentioned objectives could be achieved by using a recycled plastic composition containing a specific odor-removal catalyst that can decompose the odor-causing components of waste plastic without causing decomposition of the waste plastic itself, leading to the completion of the present invention.

That is, the present invention relates to, for example, the following items [1] to [7].
[1] waste plastic (A);
and an odor removal catalyst (B) consisting of one or more of the following (B1) and (B2):
a recycled plastic composition in which the content of the odor removal catalyst (B) is 0.01 to 30 mass%;
(B1) An odor removal catalyst in which one or more metal elements of Groups 8 to 12 are supported on a porous carrier;
(B2) An odor removal catalyst comprising a composite oxide containing two or more transition metal elements, or a mixture of two or more transition metal element oxides.

[2] The recycled plastic composition according to [1], wherein the odor removal catalyst (B1) contains an element selected from Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au.
[3] The recycled plastic composition according to [1] or [2], wherein the odor removal catalyst (B1) contains Pt.

[4] The odor removal catalyst (B2) is
at least one first metallic element selected from the group consisting of Ru, Rh, Pd, Os, Ir, and Pt;
Al, Si, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, La
and at least one second metal element selected from the group consisting of Sm, and Ce. The recycled plastic composition according to any one of [1] to [3], comprising an oxide or a composite oxide of Ce.

[5] The recycled plastic composition according to any one of [1] to [4], wherein the odor removal catalyst (B2) contains an oxide or a composite oxide of Ru, Cu, and Ce.
[6] The recycled plastic composition according to any one of [1] to [5], wherein the waste plastic (A) contains a plastic component in ASR (Automobile Shredder Residue).
[7] A deodorizing method comprising melt-kneading and/or heating the recycled plastic composition according to any one of [1] to [6].

The present invention can provide a recycled plastic composition containing waste plastics and having a highly reduced odor, as well as a deodorizing method. In particular, it can provide a recycled plastic composition that sufficiently reduces the odor of waste plastics that have odors that cannot be removed by common deodorizing methods such as ASR.

<Waste plastic (A)>
The waste plastic (A) used in the present invention means waste plastic products in general, and may be either industrial waste or general waste.

Industrial waste includes all waste generated by resin and molding manufacturers. Examples of industrial waste plastics (A) include rubbers such as ethylene-propylene copolymers (EPR, EPDM), styrene-butadiene-styrene copolymers (SBS), and their hydrogenated derivatives (SEBS); olefin copolymers such as polyethylene (PE), polypropylene (PP), and copolymers based on these; vinyl polymers such as polystyrene (PS), polymethyl methacrylate (PMMA), acrylonitrile-styrene copolymers (AS), acrylonitrile-butadiene-styrene copolymers (ABS), and polyvinyl chloride (PVC); and engineering plastics such as polyamide (PA), polyesters (PBT, PET), polyacetal (POM), polycarbonate (PC), polyphenylene ether (PPE), and polyphenylene sulfide (PPS). This waste also includes polyarloys, laminates, and mixed waste.

The waste plastic (A) used in the present invention can be waste plastic obtained after shredding durable consumer goods such as automobiles, household appliances, and electronic devices and recovering metals. In particular, the residue, primarily composed of plastic, remaining after shredding automobiles and recovering metals is called ASR (Automobile Shredder Residue), and can be used in the present invention.

Municipal waste refers to all waste generated by ordinary households, and specific examples of waste plastic (A) that is municipal waste include the same waste plastic (A) that is industrial waste. Furthermore, the waste plastic (A) used in the present invention may be a mixture of industrial waste and municipal waste.

<Odor Removal Catalyst (B)>
The odor removal catalyst according to the present invention comprises one or more of the following (B1) and (B2):

Odor Removal Catalyst (B1)
The odor removal catalyst (B1) according to the present invention is an odor removal catalyst in which one or more metal elements of Groups 8 to 12 are supported on a porous carrier.
Porous Carrier The porous carrier constituting the odor removal catalyst (B1) is capable of supporting a metal component consisting of one or more metal elements of Groups 8 to 12, and examples thereof include oxide-based carriers such as zeolite, alumina, silica, silica-alumina, and titania, and activated carbon-based carriers. Of these, oxide-based carriers are preferred, and composite oxide carriers are more preferred.
The composite oxide support is not particularly limited as long as it can support a metal component, and examples thereof include calcium titanate, aluminum silicate, magnesium aluminate, etc. Among these, zeolite (crystalline aluminosilicate) is preferred, and MFI type zeolite is particularly preferred.

When the composite oxide support is an MFI-type zeolite, its silica/alumina ratio (SiO ₂ /Al ₂ O ₃ (mol/mol)) is usually 45 or less, preferably 40 or less, and more preferably in the range of 20 to 30. A silica/alumina ratio in this range is preferred because it provides an excellent adsorption effect for odorous substances, etc. The average particle size of the composite oxide support is more preferably in the range of 10 nm to 20 μm, and an especially preferred range is 10 nm to 10 μm.

Metal elements of groups 8 to 12 (metal components)
In the odor removal catalyst (B1) according to the present invention, a porous carrier supports one or more metal elements (metal components) from Groups 8 to 12 of the periodic table. The supported metal components are metal elements from Groups 8 to 12 of the periodic table, such as Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, and Cd, and preferably one or more of Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au.

The metal component may contain one or more metal elements from Groups 8 to 12, preferably platinum (Pt). In other words, the odor removal catalyst (B1) according to the present invention preferably supports one or more metal components, including Pt. Specifically, the metal component may be Pt alone, or Pt and other metal elements may be supported on the porous support. When the metal component includes Pt and other metal elements, examples of the metal elements other than Pt include Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Cu, Ag, and Au. The supported metal species may be Pt alone or a combination of Pt and other metals, preferably Pt alone or a combination of Pt and at least one selected from Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Cu, Ag, and Au. The proportion of Pt in all supported metal elements (total of Pt and other metals) is usually 1 mol% or more, preferably 10 mol% or more.

The amount of metal components in the odor removal catalyst (B1), calculated as the metal amount of all metal components, is usually in the range of 0.01 to 10 mass%, preferably 0.01 to 5 mass%, and more preferably 0.01 to 1 mass%. When the amount of supported metal components is in this range, a sufficient odor removal effect can be achieved, which is preferable.
The odor removing catalyst (B1) according to the present invention may be a single type, or a combination of two or more types.

-Method for producing odor removal catalyst (B1) As a method for producing the odor removal catalyst (B1) of the present invention, any method for supporting the above-mentioned Group 8 to 12 metal element component on the above-mentioned porous carrier can be used without particular limitation.

Examples of methods for producing the odor removal catalyst (B1) include methods in which a Group 8 to 12 metal, metal compound, or mixture thereof is supported on a porous support such as a composite oxide by impregnation, physical mixing, ion exchange, pore filling, or other methods, and then reduced as needed. A preferred method is to impregnate a porous support with a solution or dispersion of the metal compound, dry it as needed, and then reduce it.

When the metal component contains Pt, examples of Pt compounds used for impregnation include platinum chloride, platinum oxide, platinum nitrate, platinum dinitrodiamine, platinum acetate, and platinum oxalate. Compounds of other metals include metal salts and metal oxides. Furthermore, when multiple metals are supported, the metal compound used for impregnation may be a double salt containing multiple metals.

The reduction of metal compounds supported by impregnation can be carried out by, for example, thermal decomposition reduction, reduction using a gaseous reducing agent such as hydrogen or carbon monoxide, or reduction using a liquid reducing agent such as ethanol, methanol, hydrazine, or sodium borohydride. Furthermore, by using a liquid-phase reduction method, the metal components can be supported on the porous support and reduced simultaneously. The metal compound support and reduction can be carried out in a single operation, or they can be repeated multiple times.

Odor removal catalyst (B2)
The odor removal catalyst (B2) according to the present invention comprises a composite oxide containing two or more transition metal elements, or a mixture of two or more transition metal element oxides.

Preferably, at least one first metal element selected from the group consisting of Ru (ruthenium), Rh (rhodium), Pd (palladium), Os (osmium), Ir (iridium) and Pt (platinum);
at least one second metal element selected from the group consisting of Al (aluminum), Si (silicon), Sc (scandium), Ti (titanium), V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Zn (zinc), Y (yttrium), La (lanthanum), and Sm (samarium);
and Ce (cerium),
When the odor removal catalyst (B2) according to the present invention is a composite oxide or a mixture of oxides (hereinafter also referred to as oxides) of the first metal element, the second metal element, and Ce, it is preferable that the ratio of Ce atoms to the total of the atoms of the first metal element, the atoms of the second metal element, and Ce atoms is 15 mol % or more.

The first metal element is a noble metal element that exhibits a high oxidizing activity similar to Ru, and the second metal element contributes to the dispersion of the first metal element. Among the second metal elements, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn are transition metal elements (Zn is also considered a transition metal element) that are prone to valence changes, thereby promoting the valence change of Ce, thereby facilitating the formation of oxygen defects. The presence of oxygen defects stabilizes the oxide of the first metal element (only), even in small particles, thereby achieving high dispersion within the oxide particles of Ce and the second metal element. Among the second metal elements, Sc, Y, La, and Sm, which belong to the rare earth group, are easily dissolved in Ce oxide and promote the formation of oxygen defects, thereby contributing to the high dispersion of the first metal element. Furthermore, among the second metal elements, Al and Si have oxides with high specific surface areas, thereby contributing to the high dispersion of the first metal element. It is believed that the second metal elements function in this manner. For this reason, it is believed that the odor removal catalyst (B2) of the present invention exhibits excellent odor removal performance.

The first metal element is at least one selected from the group consisting of Ru, Rh, Pd, Os, Ir, and Pt, preferably at least one selected from the group consisting of Ru, Rh, and Pd, and more preferably Ru.

The second metal element is at least one selected from the group consisting of Al, Si, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, La, and Sm, for example, at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, at least one selected from the group consisting of Sc, Y, La, and Sm, or at least one selected from the group consisting of Al and Si, preferably at least one selected from the group consisting of Fe, Co, Ni, and Cu, and more preferably Cu.

Examples of the oxides include a mixture of an oxide of the first metal element, an oxide of the second metal element, and an oxide of Ce (hereinafter also referred to as an "oxide mixture"), and a composite oxide of the first metal element, the second metal element, and Ce. Among these, the composite oxide is preferred. While the detailed structure of the composite oxide is not necessarily clear, the composite oxide may include, for example, an oxide containing Ce in which the first metal element or the second metal element is solid-dissolved, or an oxide particle of the first metal element dispersed in oxide particles of Ce and the second metal element.

The oxide mixture is preferably a mixture of an oxide of the first metal element, which is at least one selected from the group consisting of Ru, Rh, and Pd, an oxide of the second metal element, which is at least one selected from the group consisting of Fe, Co, Ni, and Cu, and an oxide of Ce, and is more preferably a mixture of an oxide of Ru, an oxide of Cu, and an oxide of Ce.

The composite oxide is preferably a composite oxide of the first metal element, which is at least one selected from the group consisting of Ru, Rh, and Pd; the second metal element, which is at least one selected from the group consisting of Fe, Co, Ni, and Cu; and Ce, and more preferably a composite oxide of Ru, Cu, and Ce.

The ratio of Ce atoms to the total of the atoms of the first metal element, the atoms of the second metal element, and Ce atoms in the oxides is 15 mol% or more. When the Ce ratio is within this range, an odor removal catalyst with good odor removal performance can be obtained. On the other hand, if this ratio is less than 15 mol%, the removal performance of the resulting odor removal catalyst may be inferior.

The proportions of the atoms of the first metal element, the atoms of the second metal element, and Ce atoms in the oxides are, based on the above criteria, preferably 0.05 to 75 mol%, 5 to 79.95 mol%, and 18 to 94.95 mol%, respectively; more preferably 0.05 to 10 mol%, 5 to 75 mol%, and 18 to 85 mol%, respectively; and even more preferably 0.05 to 7 mol%, 15 to 75 mol%, and 20 to 84.95 mol%, respectively.

The oxides may contain the first metal element with different valences (e.g., Ru(III) and Ru(IV)), the second metal element with different valences (e.g., Cu(I) and Cu(II)), and Ce with different valences (e.g., Ce(III) and Ce(IV)).

The specific surface area of the odor removing catalyst (B2) according to the present invention, as measured by the BET method, is, for example, 50 to 500 ^{m 2} /g, and preferably 100 to 300 m ² /g. This specific surface area can be adjusted, for example, by pulverizing the odor removing catalyst (B2).
The odor removing catalyst (B2) according to the present invention may be a single type, or a combination of two or more types.

-Method for producing odor removal catalyst (B2) As a method for producing the odor removal catalyst (B2) of the present invention, any method capable of producing a composite oxide containing two or more transition metal elements or a mixture of two or more transition metal element oxides can be used without any particular limitation.

When the odor removal catalyst (B2) according to the present invention is a mixture of an oxide of the first metal element, an oxide of the second metal element, and an oxide of Ce, the method may include a step of mixing the oxide of the first metal element (e.g., ruthenium oxide), the oxide of the second metal element (e.g., copper oxide), and an oxide of Ce. The ratio of Ce atoms to the total of the atoms of the first metal element, the atoms of the second metal element, and Ce atoms contained in these oxides is preferably 15 mol% or more. When the Ce ratio is within this range, an odor removal catalyst (B2) with good odor removal performance can be obtained. On the other hand, when this ratio is less than 15 mol%, the removal performance of the resulting odor removal catalyst may be inferior. These oxides are mixed so that the ratio of the atoms of the first metal element, the atoms of the second metal element, and Ce atoms to the total of the atoms of the first metal element, the atoms of the second metal element, and Ce atoms in the odor removal catalyst (B2) according to the present invention is the above-mentioned ratio. The oxides are preferably in powder or particulate form.

When the odor removal catalyst (B2) according to the present invention is a composite oxide of the first metal element, the second metal element, and Ce, a method for producing the same can be, for example,
a step (1) of dissolving the salt of the first metal element, the salt of the second metal element, and the salt of Ce in a solvent (preferably water) in which the salts are soluble to prepare a solution (preferably an aqueous solution);
Step (2) of mixing the solution with a base to form a precipitate and prepare a slurry;
(3) obtaining a catalyst precursor from the slurry; and (4) calcining the catalyst precursor to produce an odor removal catalyst.
The method includes the steps of:

Examples of the salts used in step (1) include chlorides, bromides, nitrates, sulfates, and acetates of the first metal element, the second metal element, or Ce, with chlorides, nitrates, and acetates being preferred. These may also be hydrates. Specific examples of the salts include ruthenium(III) chloride, copper(II) nitrate trihydrate, and cerium(III) nitrate hexahydrate.

The solution may or may not further contain an oxide of one or more elements selected from the group consisting of the first metal element, the second metal element, and Ce. These oxides may be added to the solvent when dissolving the salt of the first metal element, the salt of the second metal element, and the Ce salt in the solvent, or may be mixed with the prepared solution. Examples of the oxides include oxides of the first metal element such as ruthenium oxide, oxides of the second metal element such as copper oxide, and cerium oxide. The oxides are preferably in powder or particulate form.

The ratio of Ce atoms to the total of the atoms of the first metal element, the atoms of the second metal element, and Ce atoms contained in these salts and any oxides is preferably 15 mol% or more. When the Ce ratio is within this range, an odor removal catalyst with good odor removal performance can be obtained. On the other hand, if this ratio is less than 15 mol%, the removal performance of the resulting odor removal catalyst may be inferior.

The proportions of the atoms of the first metal element, the atoms of the second metal element, and Ce atoms contained in these salts and any oxides are, based on the above criteria, preferably 0.05 to 75 mol%, 5 to 79.95 mol%, and 18 to 94.95 mol%, respectively, more preferably 0.05 to 10 mol%, 5 to 75 mol%, and 18 to 85 mol%, respectively, and even more preferably 0.05 to 7 mol%, 15 to 75 mol%, and 20 to 84.95 mol%, respectively.

Examples of bases used in step (2) include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, ammonia, and urea. These may be in the form of a solution (preferably an aqueous solution). The resulting slurry is preferably stirred.

In step (3), a catalyst precursor is obtained from the slurry obtained in step (2). The catalyst precursor may be a solid recovered from the slurry (by filtration or other means), or may be a solid prepared by subjecting the slurry to hydrothermal synthesis; the latter is preferred. This hydrothermal synthesis is carried out, for example, at 80 to 300°C for 5 to 48 hours. The catalyst precursor is preferably washed with distilled water and then dried by heating.

The calcination in step (4) is carried out, for example, at 120 to 600° C. for 1 to 48 hours. The calcination is preferably carried out in an oxygen-containing atmosphere, for example, in an air stream.
The odor removing catalyst obtained by calcination may be used as it is or may be crushed before use.

The method for producing the odor removing catalyst (B2) which is a composite oxide further includes the following steps:
Step (11) of dissolving the salt of the first metal element and the salt of the second metal element in a solvent (preferably water) in which the salts are soluble to prepare a solution (preferably an aqueous solution);
Step (12) of dispersing cerium oxide in the solution to prepare a dispersion;
a step (13) of removing the solvent from the dispersion to obtain a solid content; and a step (14) of calcining the solid content to produce an odor removal catalyst.
The method includes the steps of:

The details of the salt of the first metal element and the salt of the second metal element used in step (11) are the same as those of the salts used in step (1) described above.
The cerium oxide used in step (12) is preferably in the form of a powder or particles.

The method for removing the solvent in the step (13) includes heating the dispersion to evaporate the solvent.
The calcination conditions in step (14) are the same as those in the above-mentioned step (4). The odor removing catalyst obtained by calcination may be used as is or may be crushed before use.

・Odor removal catalyst (B)
The odor removal catalyst (B) according to the present invention comprises one or more of the odor removal catalyst (B1) and the odor removal catalyst (B2). That is, the odor removal catalyst (B) according to the present invention may be either the odor removal catalyst (B1) or the odor removal catalyst (B2), or may be a combination of the odor removal catalyst (B1) and the odor removal catalyst (B2) in any ratio.

The odor removal catalyst (B1) and odor removal catalyst (B2) of the present invention both have excellent deodorizing effects and are particularly effective in reducing and removing odorous substances such as aldehydes, carboxylic acids, and esters. Specifically, at least a portion of the odorous substances in the surrounding gas that comes into contact with the odor removal catalyst of the present invention are decomposed, resulting in the reduction and removal of the odorous substances.

Both the odor removal catalyst (B1) and odor removal catalyst (B2) of the present invention are less likely to release odorous substances and diffuse odors, even when exposed to high temperatures. Furthermore, because the adsorbed odorous substances are decomposed and diffused, their adsorption capacity does not decrease significantly, allowing them to be used for deodorization over an extended period of time. Therefore, even when mixed with waste plastic (A), heating and melt-kneading are performed, and the recycled plastic composition is produced and molded, the odor of waste plastic (A) can be decomposed and reduced without impairing its deodorizing performance.

In addition, both the odor removal catalyst (B1) and odor removal catalyst (B2) of the present invention are less likely to cause the decomposition of plastics, and therefore do not promote the decomposition of plastics in the recycled plastic composition, and can decompose and reduce odors originating from waste plastic (A) without impairing the original strength of molded articles and the like obtained from the recycled plastic composition.

Photocatalyst _TiO2 is known as a catalyst with odor-decomposing properties, and this catalyst is in a form that can be kneaded into resin. However, when this catalyst is mixed with waste plastic, it breaks down the odor and also causes the resin to decompose, which creates the problem of degradation in a short period of time when used as recycled plastic for manufacturing molded products, etc.

<Recycled Plastic Composition>
The recycled plastic composition of the present invention contains the waste plastic (A) and the odor removal catalyst (B). The content of the odor removal catalyst (B) in the recycled plastic composition of the present invention is usually 0.01 to 30 mass%, preferably 0.1 to 20 mass%, and more preferably 0.5 to 10 mass%.

The recycled plastic composition may consist solely of the waste plastic (A) and the odor removal catalyst (B), or may contain optional components such as virgin resin and various additives, provided that the object of the invention is not impaired.
Examples of unused resins include rubbers such as ethylene-propylene copolymers (EPR, EPDM), styrene-butadiene-styrene copolymers (SBS) and hydrogenated products thereof (SEBS); olefin copolymers such as polyethylene (PE), polypropylene (PP), and copolymers based on these; vinyl polymers such as polystyrene (PS), polymethyl methacrylate (PMMA), acrylonitrile-styrene copolymers (AS), acrylonitrile-butadiene-styrene copolymers (ABS), and polyvinyl chloride (PVC); and engineering plastics such as polyamide (PA), polyesters (PBT, PET), polyacetal (POM), polycarbonate (PC), polyphenylene ether (PPE), and polyphenylene sulfide (PPS).

Additives that can be added to plastic compositions can be used without particular restriction depending on the application, etc. Examples of additives include nucleating agents, antiblocking agents, pigments, dyes, fillers, lubricants, plasticizers, release agents, antioxidants, flame retardants, UV absorbers, antibacterial agents, surfactants, antistatic agents, weather stabilizers, heat stabilizers, antislip agents, foaming agents, crystallization aids, antifogging agents, antioxidants, hydrochloric acid absorbers, impact modifiers, crosslinking agents, co-crosslinking agents, crosslinking aids, adhesives, softeners, and processing aids. These additives may be used alone or in combination of two or more.

The recycled plastic composition of the present invention may be a simple mixture of the components, or may be prepared by melt-kneading. The recycled plastic composition of the present invention deodorizes the odor of waste plastics by melt-kneading or heating, so the recycled plastic composition of the present invention prepared by melt-kneading has reduced or eliminated the odor caused by waste plastic (A). Furthermore, when the recycled plastic composition of the present invention is a simple mixture of the components, melt-kneading or heating during molding or use reduces or eliminates the odor caused by waste plastic (A).

<How to remove odors>
The recycled plastic composition of the present invention is melt-kneaded or heated to deodorize the odor of waste plastics. That is, the odor removal method of the present invention includes a step of melt-kneading and/or heating the recycled plastic composition of the present invention. Examples of melt-kneading and/or heating include melt-kneading the recycled plastic composition of the present invention using, for example, a single-screw or twin-screw extruder, a Banbury mixer, a roll, or various kneaders. The melt-kneading temperature is preferably a temperature at which at least a portion, preferably the entirety, of the waste plastic (A) is melted. For example, the melt-kneading temperature can be typically 130 to 400°C, preferably 160 to 280°C. When odor removal is performed by heating without melt-kneading, the temperature can be typically 50 to 200°C, preferably 80 to 150°C.

The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

[Production Example 1]
Preparation of odor removal catalyst A
0.05 g of hexachloroplatinic (IV) acid hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) containing Pt was weighed and dissolved in 50 cc of distilled water. This solution was placed in a 200 cc eggplant-shaped flask, and then MFI type zeolite (H-ZSM-5, manufactured by Tosoh Corporation) was added.
2.0 g of HSZ 822HOA (silica/alumina ratio ( _SiO2 / _{Al2O3 ratio} (mol/mol)): 23, average particle size: 5 μm) was added, and the Pt compound solution was impregnated into the zeolite to achieve a 1% Pt/zeolite ratio. The flask was then attached to an evaporator, and water was evaporated at 80°C under vacuum, and the remaining powder was recovered. The recovered powder was heated to 120°C at a rate of 5°C/min in a 100% _H2 flow, and hydrogen reduction was performed for 2 hours to prepare odor removal catalyst A, which is a Pt/zeolite catalyst.

[Example 1]
Preparation and evaluation of recycled plastic composition (1)
The recovered plastic ASR-1 (Automobile Shredder Residue) was obtained from a grant project related to research, studies, and demonstrations that contribute to the advancement of automobile recycling. Its composition is as follows: 91% PP, 9% PE.
10 g of ARS-1 and 1 g of the odor removal catalyst A obtained in Production Example 1 were kneaded at 200°C using a small kneading machine DSM-Xplore (manufactured by DSM) to obtain a strand of recycled plastic composition (1). The resulting strand was cut, and 1 g of the cut strand was placed in a 3 L sampling bag: Freck Sampler (manufactured by Omi Odor Air Service Co., Ltd.). 2.5 L of air passed through an activated carbon filter was introduced, and the dedicated lid was closed. The sample was left at 80°C, and the odor intensity was evaluated sensorily after 1 day and 3 days, and the results are shown in Table 1. Here, odor intensity is an index that quantifies the degree of odor shown in Table 2. This index for sensory evaluation was also used in the following examples and comparative examples.

[Example 2]
Preparation and evaluation of recycled plastic composition (2)
Recycled plastic (2) was prepared and evaluated in the same manner as in Example 1, except that the amount of odor removal catalyst A used was 0.1 g. The results are shown in Table 1.

[Comparative Example 1]
The same procedure as in Example 1 was carried out except that only 10 g of ARS-1 was used. The results are shown in Table 1.

Claims (3)

Waste plastic (A);
and an odor removal catalyst (B) consisting of the following (B1):
a recycled plastic composition in which the content of the odor removal catalyst (B) is 0.01 to 30 mass%;
(B1) An odor removal catalyst in which Pt is supported on MFI zeolite . The recycled plastic composition according to claim 1 , wherein the waste plastic (A) is ASR (Automobile Shredder Residue). A deodorizing method comprising melt-kneading and/or heating the recycled plastic composition according to claim 1 or 2 .