Polyolefin-based resin composition

Abstract

Provided is a resin composition containing a post-consumer recycled (PCR) polyolefin reduced in an aldehyde-derived odor.　A polyolefin-based resin composition comprises a post-consumer recycled (PCR) polyolefin and an aldehyde scavenger. The aldehyde scavenger is an aminooxyalkyl group-supporting carrier in which a compound represented by formula (1) and a carrier are bonded to each other through a chemical bond. The aminooxyalkyl group-supporting carrier has one or more structures selected from the structures represented by formulae (2) to (4). [In formulae (1) to (4), R represents an alkyl group having 1-4 carbon atoms; X represents an alkoxy group having 1-4 carbon atoms; m represents an integer of 0-2; m' represents an integer of 0-1; and n represents an integer of 1-12; wherein, when m is 0 or 1 or m' is 0, the plurality of X's may be the same or different from each other, and when m is 2, the plurality of R's may be the same or different from each other.]

Description

Polyolefin resin composition

[0001] The present disclosure relates to a polyolefin resin composition having reduced odor derived from aldehydes.

[0002] In recent years, environmental pollution caused by plastics has become a problem, and material recycling of plastic products has been promoted.

[0003] Plastic recycling can be divided into two categories, "post-consumer recycling (PCR)" and "post-industrial recycling (PIR)," depending on the raw materials and source of separation. Post-consumer recycling (PCR) refers to the collection and recycling of used products in the market, while post-industrial recycling (PIR) refers to the recycling and reuse of materials generated in the manufacturing process of products before they reach the market.

[0004] The process of reusing waste plastics to obtain molded products generally includes washing, dehydrating, crushing, re-pelletizing, and molding the recovered waste plastics.

[0005] Here, waste plastics subjected to post-consumer recycling (PCR) contain a wide variety of substances in addition to the main components, and these impurities often remain even after the cleaning process. For this reason, molded products made from recycled plastic materials as raw materials not only emit an odor due to aldehydes and other impurities, making them difficult to use, but also have the problem of reduced moldability.

[0006] Under these circumstances, the removal of impurities contained in waste plastics has been studied to date.

[0007] For example, a method has been proposed in which an acid acceptor such as magnesium oxide or hydrotalcite is added to waste plastics containing vinyl chloride resin, such as waste plastic containers and packaging and other general plastic product waste, to suppress the generation of hydrochloric acid (see, for example, Patent Document 1).

[0008] In addition, a low-odor recycled resin container has been proposed in which an adsorbent such as zeolite is added to a multilayer plastic container containing a recycled resin layer from a polyolefin-based packaging container, thereby adsorbing hydrocarbon volatiles generated by thermal degradation (see, for example, Patent Document 2).

[0009] However, the method described in Patent Document 1 is a method for suppressing hydrochloric acid, and the method described in Patent Document 2 is a method for reducing odors by adsorption of hydrocarbon volatiles, but neither method is considered for reducing aldehydes. Furthermore, resin molding is generally performed at temperatures above 200°C, which can deactivate existing aldehyde scavengers.

[0010] Japanese Patent No. 4828836 Japanese Patent Application Laid-Open No. 1995-33172

[0011] The present invention has been made in view of the above background art, and an object of the present invention is to provide a polyolefin resin composition in which the odor derived from aldehydes is reduced.

[0012] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that a polyolefin resin composition containing a specific aldehyde scavenger can solve the above-mentioned problems, and have thus completed the present invention.

[0013] That is, the present disclosure includes the following embodiments.

[0014] [1] A polyolefin-based resin composition comprising a post-consumer recycled (PCR) polyolefin and an aldehyde scavenger, wherein the aldehyde scavenger is an aminooxyalkyl group-supported carrier in which a compound represented by the following formula (1) is chemically bonded to the carrier, and the aminooxyalkyl group-supported carrier has one or more structures represented by the following formulas (2) to (4).

[0015]

[0016]

[0017] [In the above formulas (1) to (4), R represents an alkyl group having 1 to 4 carbon atoms, X represents an alkoxy group having 1 to 4 carbon atoms, m represents an integer of 0 to 2, m' represents an integer of 0 to 1, and n represents an integer of 1 to 12. When m is 0 or 1, or when m' is 0, multiple Xs may be the same or different, and when m is 2, multiple Rs may be the same or different.] [2] The polyolefin-based resin composition according to the above [1], wherein the polyolefin in the post-consumer recycled (PCR) polyolefin is polyethylene.

[0018] [3] The polyolefin resin composition according to the above [1] or [2], wherein in the formulas (1), (2a) to (2c), R is a methyl group, and each X is independently a methoxy group, an ethoxy group, or an isopropoxy group.

[0019] [4] The polyolefin resin composition according to any one of [1] to [3] above, wherein the carrier is silica gel, alumina, zeolite, magnesia, titania, zirconia, ceria, diatomaceous earth, activated carbon, cellulose, or hydroxyapatite.

[0020] [5] The polyolefin resin composition according to the above [4], wherein the carrier is silica gel.

[0021] [6] The polyolefin resin composition according to the above [1] or [2], wherein the content of the aldehyde scavenger is 0.01 mass% or more and 10 mass% or less relative to the total amount of the polyolefin resin composition.

[0022] [7] The polyolefin resin composition according to any one of [1] to [6] above, wherein the post-consumer recycled (PCR) polyolefin contains an aldehyde.

[0023] [8] The polyolefin resin composition according to the above [7], wherein the aldehyde contained in the post-consumer recycled (PCR) polyolefin is acetaldehyde and / or butyraldehyde.

[0024] In this disclosure, post-consumer recycled (PCR) polyolefins that have been used in the market are referred to as "post-consumer recycled (PCR) polyolefins."

[0025] Molded articles obtained by molding the polyolefin resin composition of the present disclosure have less aldehyde odor than molded articles derived from conventional post-consumer recycled (PCR) polyolefins, and can therefore be used for daily necessities, industrial parts, office supplies, chemical products, etc. As a result, the reuse of post-consumer recycled (PCR) polyethylene is promoted, thereby reducing the environmental impact.

[0026] In the present disclosure, the polyolefin-based resin composition includes a post-consumer recycled (PCR) polyolefin and an aldehyde scavenger.

[0027] The polyolefin in the post-consumer recycled (PCR) polyolefin is not particularly limited, and examples thereof include homopolymers or copolymers of α-olefins having 2 to 12 carbon atoms, such as ethylene, propylene, and 1-butene, and copolymers of these, and copolymers of ethylene with vinyl esters and / or acrylic esters. Specific examples include ethylene homopolymers such as high-pressure low-density polyethylene and high-density polyethylene, ethylene-based polymers such as ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers, ethylene-4-methyl-1-pentene copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic ester copolymers, and ethylene-methacrylic ester copolymers, propylene homopolymers, propylene-ethylene copolymers, propylene-1-butene copolymers, poly-1-butene, poly-1-hexene, and poly-4-methyl-1-pentene. Of these, polyethylene is preferred.

[0028] The post-consumer recycled (PCR) polyolefin is not particularly limited, but examples thereof include polyolefins used as automobile and railway seats, sofas, sheets, gloves, container lids, bottles, cups, trays, tubes, etc.

[0029] The post-consumer recycled (PCR) polyolefin refers to a polyolefin recovered from waste for reuse. Because the polyolefin has been discarded, it may contain contaminants and other waste-derived substances that become mixed in during the disposal and recovery process. Contaminants on the polyolefin include sweat and sebum from human or animal use, as well as odorous components derived from these. Examples of such odorous components include organic acids, aldehydes, ketones, and ammonia. Examples of organic acids include acetic acid, butyric acid, and isovaleric acid. Examples of aldehydes include acetaldehyde, butylaldehyde, and 2-nonenal. Examples of ketones include 2,3-butanedione.

[0030] The post-consumer recycled (PCR) polyolefin may be one that has been subjected to a process of crushing a molded product and a process of washing the product with water or the like.

[0031] In the present disclosure, the aldehyde scavenger is an aminooxyalkyl group-supported carrier in which a compound represented by the following formula (1) is chemically bonded to the carrier, and the aminooxyalkyl group-supported carrier has one or more structures represented by the following formulas (2) to (4):

[0032]

[0033]

[0034] [In the above formulas (1) to (4), R represents an alkyl group having 1 to 4 carbon atoms, X represents an alkoxy group having 1 to 4 carbon atoms, m represents an integer of 0 to 2, m' represents an integer of 0 to 1, and n represents an integer of 1 to 12. When m is 0 or 1, or when m' is 0, multiple Xs may be the same or different, and when m is 2, multiple Rs may be the same or different.] Examples of the aldehyde scavenger include those obtained by chemically modifying a support with a compound represented by the above formula (1) (hereinafter also referred to as a "silane coupling agent") (hereinafter also referred to as a "silane coupling reaction").

[0035] In the above formulas (1), (2a) to (2c), R represents an alkyl group having 1 to 4 carbon atoms, and X represents an alkoxy group having 1 to 4 carbon atoms.

[0036] Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a 2-methylpropyl group, a 1-methylpropyl group, and a tert-butyl group.

[0037] Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a 2-methylpropyloxy group, a 1-methylpropyloxy group, and a tert-butoxy group.

[0038] In terms of efficiency of the silane coupling reaction, R is preferably a methyl group, X is preferably a methoxy group, an ethoxy group, or an isopropoxy group, m is preferably an integer of 0 to 1, m' is preferably 0, and n is preferably an integer of 3 to 9. Multiple Xs may be the same or different.

[0039] The silane coupling agent represented by the formula (1) may be a commercially available product, but it can also be synthesized according to the method described in Organic Preparations and Procedures International, 1994, Vol. 26, pp. 111-113, JP-A-7-233132, and Tetrahedron Letters, 2005, Vol. 46, pp. 7973-7975.

[0040] In the aminooxyalkyl group-carrying carrier, part or all of the aminooxyalkyl groups may be in the form of a chemically acceptable salt with an inorganic or organic acid. The type of salt is not particularly limited, but examples include inorganic acid salts such as hydrochloride, hydrobromide, perchlorate, silicate, tetrafluoroborate, hexafluorophosphate, sulfate, nitrate, and phosphate; and organic acid salts such as acetate, citrate, fumarate, maleate, trifluoromethanesulfonate, trifluoroacetate, benzoate, and p-toluenesulfonate. Inorganic acid salts are preferred because they are inexpensive, and hydrochloride is more preferred.

[0041] The amount of aminooxyalkyl group supported on the carrier can be adjusted as desired depending on the purpose and is not particularly limited, but it is preferable that the amount of aminooxyalkyl group is in the range of 0.01 mmol / g or more and 10 mmol / g or less relative to the mass of the carrier.

[0042] In the present disclosure, the carrier on which the aminooxyalkyl group is supported may be any carrier insoluble in water, and is not particularly limited, but examples thereof include polymer carriers such as styrene-based polymers such as polystyrene and cross-linked polystyrene, polyolefins such as polyethylene and polypropylene, poly(halogenated olefins) such as polyvinyl chloride and polytetrafluoroethylene, nitrile-based polymers such as polyacrylonitrile, (meth)acrylic polymers such as polymethyl methacrylate and polyethyl acrylate, high molecular weight polysaccharides such as cellulose, agarose, and dextran, inorganic carriers such as silica gel, alumina, zeolite, magnesia, titania, zirconia, ceria, diatomaceous earth, activated carbon, cellulose, and hydroxyapatite, etc. As the carrier to be mixed with the silane coupling agent, inorganic carriers are preferred, and silica gel is more preferred, in terms of the efficiency of the silane coupling reaction.

[0043] The shape of the carrier is not particularly limited, but examples include shapes commonly used as separation substrates, such as spherical (e.g., spherical particles), granular, fibrous, granular, monolithic column, hollow fiber, and membrane (e.g., flat membrane), among which spherical, membrane, granular, granular, and fibrous shapes are preferred. Spherical, granular, or granular carriers are particularly preferred because the volume used can be freely set when used in a column method or batch method. The particle size of spherical, granular, or granular carriers is usually in the range of 0.1 μm to 10 mm on average, but is preferably 0.1 μm to 100 μm in terms of good dispersibility in liquid.

[0044] The carrier may be porous or non-porous. The average pore size of the porous carrier is usually 0.1 nm to 1 μm, but is preferably in the range of 0.1 nm to 300 nm in terms of the aldehyde capture rate.

[0045] The content of the aminooxyalkyl group-supported carrier is preferably 0.01% by mass or more and 10% by mass or less relative to the total amount of the polyethylene resin composition. If the content of the aminooxyalkyl group-supported carrier is less than 0.01% by mass, the aldehyde reduction effect may be insufficient. On the other hand, if the content of the aminooxyalkyl group-supported carrier is more than 10% by mass, the resin physical properties such as tensile strength may be impaired.

[0046] The polyolefin resin composition may contain, within the scope of not impairing the effects of the present invention, a thermoplastic resin other than post-consumer recycled (PCR) polyethylene, an antistatic agent, a light stabilizer, an ultraviolet absorber, a nucleating agent, a lubricant, an antioxidant, an antiblocking agent, a flow improver, a mold release agent, a colorant, an inorganic neutralizing agent, a hydrochloric acid absorber, a filler conductive agent, a chain extender, a hydrolysis inhibitor, and the like.

[0047] The polyolefin resin composition can be suitably used as a raw material for a molded article.

[0048] Molded articles obtained by molding the polyolefin resin composition are useful as daily commodities, industrial parts, office supplies, chemical supplies, etc.

[0049] Next, a method for producing the polyolefin resin composition will be described.

[0050] The method for producing the polyolefin resin composition is not particularly limited as long as it can disperse each component, and the composition can be produced using, for example, a commonly used resin kneading device, such as a single-screw extruder, a twin-screw extruder, a multi-screw extruder, a Banbury mixer, a pressure kneader, a rotating roll, or an internal mixer.

[0051] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0052] In the examples and comparative examples, the post-consumer recycled (PCR) polyolefin, aldehyde scavenger, and antioxidant used were as follows:

[0053] Post-consumer recycled (PCR) polyolefin: Post-consumer recycled (PCR) polyethylene, a fibrous molded product, obtained from Taisen Sangyo Co., Ltd. Since the amount of aldehyde released varies depending on the production lot, these are referred to as Lot A, Lot B, and Lot C, respectively.

[0054] Aldehyde scavenger A: the aminooxyalkyl group-supported carrier obtained in Synthesis Example 1, Aldehyde scavenger B: Kesmon NS-750 manufactured by Toagosei Co., Ltd., Aldehyde scavenger C: adipic acid dihydrazide manufactured by Tokyo Chemical Industry Co., Ltd., Antioxidant: Sumilizer GP, a phosphite-based product manufactured by Sumitomo Chemical Co., Ltd.

[0055] Synthesis Example 1 19.94 g of silica gel (NIPGEL BY-400, manufactured by Tosoh Silica Corporation) and 173.4 g of toluene were mixed, and then a mixture of 8.08 g of a silane coupling agent represented by the chemical formula (1') and 43.35 g of toluene was added dropwise under a nitrogen atmosphere, followed by stirring at 25°C for 120 hours.

[0056]

[0057] The resulting reaction solution was filtered, and the residue was dried at 120°C for 4 hours using a hot air dryer (DRJ433DA, manufactured by Advantec Co., Ltd.) to obtain a support on which aminooxyalkyl groups were supported by chemical bonding (hereinafter referred to as "aminooxyalkyl group-supported support"). Elemental analysis of the obtained aminooxyalkyl group-supported support revealed that the aminooxyalkyl group content was 1.4 mmol / g relative to the support mass.

[0058] Example 1 Post-consumer recycled (PCR) polyolefin pulverized with a rotary cutter, an aldehyde scavenger, and an antioxidant were mixed in advance in a tumbler in the proportions shown in Table 1, and the mixture was melt-kneaded at a temperature of 210°C and a discharge rate of 20 kg using a twin-screw extruder (TEX25αIII manufactured by The Japan Steel Works, Ltd.) to obtain resin composition pellets. From the obtained pellets, a compression molded sheet having a thickness of 2 mm was produced at a temperature of 200°C using a compression molding machine (Shinto AWFA-50 double-acting hydraulic two-stage molding machine manufactured by Shinto Metal Industries Co., Ltd.).

[0059] The resulting compression-molded sheet was cut into a square with a side length of 50 mm to form a test specimen, and this test specimen was sealed in a 2 L sampling bag together with 1 L of nitrogen gas. The sampling bag was heated at 65 ° C for 2 hours using a hot air dryer (Advantec, DRJ433DA), and the gas in the Tedlar bag was then adsorbed onto a cartridge (Fujifilm Wako Pure Chemical Industries, Presep-C DNPH) carrying 2,4-dinitrophenylhydrazine (DNPH). The cartridge was treated with acetonitrile, and the DNPH-aldehyde condensate was eluted. Subsequently, the eluate was analyzed using a liquid chromatograph (Shimadzu Corporation, LC-2030C Plus) to quantify the acetaldehyde and butyraldehyde volatilized from the test specimen. The results are shown in Table 1.

[0060] Examples 2 to 7 and Comparative Examples 1 to 6 Compression-molded sheets were obtained in the same manner as in Example 1, except that the compounding ingredients and their amounts were changed to the proportions shown in Table 1, and the amount of aldehyde volatilized was quantified. The results are shown in Tables 1 and 2.

[0061] As shown in Tables 1 and 2, the polyolefin resin compositions of Examples 1 to 7 were found to emit less aldehyde than the polyolefin resin compositions of Comparative Examples 1 and 2, which did not contain an aldehyde scavenger, and the polyolefin resin compositions of Comparative Examples 3 to 6, which contained an existing aldehyde scavenger.

[0062]

[0063]

[0064] Example 8 A compression-molded sheet was obtained in the same manner as in Example 1, except that post-consumer recycled (PCR) polyolefin Lot C was used instead of Lot A, and the aldehyde scavenger and antioxidant were mixed in the proportions shown in Table 3. The amount of aldehyde volatilized was then quantified. The results are shown in Table 3.

[0065]

[0066] Example 9: A compression-molded sheet was obtained in the same manner as in Example 8, except that aldehyde scavenger A was preheated at 200°C for 30 minutes in an electric furnace (Yamato Scientific Co., Ltd., FO810), and the amount of aldehyde volatilized was quantified. The results are also shown in Table 3.

[0067] Example 10, Comparative Examples 7 to 10 Compression-molded sheets were obtained in the same manner as in Example 8, except that the compounding ingredients, compounding amounts, and preheating conditions for the aldehyde scavenger were changed to those shown in Table 3, and the amount of aldehyde volatilized was quantified. The results are also shown in Table 3.

[0068] As shown in Table 3, the polyolefin resin compositions of Examples 9 and 10, which contained preheat-treated scavenger A, had the same amount of aldehyde volatilization as the polyolefin resin composition of Example 8, which contained non-preheat-treated scavenger A, and the amount of aldehyde volatilization was significantly reduced compared to Comparative Example 7, in which no scavenger was added.

[0069] On the other hand, when existing scavengers were preheated and blended into a polyolefin-based resin composition, an increase in the amount of aldehyde volatilized was observed (see Comparative Examples 9 and 10), suggesting that the scavengers were degraded by the preheat treatment.

[0070] These results demonstrate that the aldehyde scavenger contained in the polyolefin resin composition of the present disclosure maintains its aldehyde scavenging effect even when previously exposed to high temperatures of 200 to 230°C (estimated heating temperatures during resin molding), and has higher heat resistance than existing scavengers.

[0071] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0072] The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2023-135134, filed on August 23, 2023, are hereby incorporated by reference as the disclosure of the present invention.

Claims

1. A polyolefin-based resin composition comprising a post-consumer recycled (PCR) polyolefin and an aldehyde scavenger, the aldehyde scavenger being an aminooxyalkyl group-bearing carrier in which a compound represented by the following formula (1) is chemically bonded to the carrier, and the aminooxyalkyl group-bearing carrier has one or more structures selected from the structures represented by the following formulas (2) to (4). [In the above formulas (1) to (4), R represents an alkyl group having 1 to 4 carbon atoms, X represents an alkoxy group having 1 to 4 carbon atoms, m represents an integer of 0 to 2, m' represents an integer of 0 to 1, and n represents an integer of 1 to 12. When m is 0 or 1, or m' is 0, multiple Xs may be the same or different, and when m is 2, multiple Rs may be the same or different.] 2. The polyolefin resin composition according to claim 1, wherein the polyolefin in the post-consumer recycled (PCR) polyolefin is polyethylene.

3. The polyolefin resin composition according to claim 1, wherein in formulas (1), (2a) to (2c), R is a methyl group, and each X is independently a methoxy group, an ethoxy group, or an isopropoxy group.

4. The polyolefin resin composition according to claim 1 or 2, wherein the support is silica gel, alumina, zeolite, magnesia, titania, zirconia, ceria, diatomaceous earth, activated carbon, cellulose, or hydroxyapatite.

5. The polyolefin resin composition according to claim 4, wherein the carrier is silica gel.

6. A polyolefin resin composition according to claim 1 or 2, wherein the content of the aldehyde scavenger is from 0.01% by mass to 10% by mass, based on the total amount of the polyolefin resin composition.

7. The polyolefin resin composition according to claim 1 or 2, wherein the post-consumer recycled (PCR) polyolefin contains an aldehyde.

8. The polyolefin resin composition according to claim 7, wherein the aldehyde contained in the post-consumer recycled (PCR) polyolefin is acetaldehyde and / or butyraldehyde.

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