Polyolefin materials and molded products

Abstract

To provide a melt-mold polyolefin material and molded articles thereof that have excellent physical properties and chemical properties such as long-term durability. [Solution] A melt-mold polyolefin material comprising 10 to 90 parts by weight of a recycled polyolefin material derived from crosslinked polyolefin with an MFR of 0.2 g / 10 min or more, and 90 to 10 parts by weight of a polyolefin material not derived from recycled material (provided that the total of the recycled polyolefin material and the non-recycled polyolefin material is 100 parts by weight). A molded article of this melt-mold polyolefin material.

Description

[Technical Field]

[0001] The present invention relates to polyolefin materials and molded articles, and more particularly to melt-mold polyolefin materials and molded articles using recycled materials derived from crosslinked polyolefins. [Background technology]

[0002] Cross-linked polyolefins have been considered difficult to recycle because they do not melt even when heated. Decomposition under supercritical conditions has also been considered, but this is costly due to the large amount of chemicals used under high temperature and pressure.

[0003] Patent Document 1 describes a method for regenerating a polyolefin that can be melted by heat by partially cleaving the molecular chains of a cross-linked polyolefin, at a relatively low cost.

[0004] However, although the polyolefin obtained by the method described in Patent Document 1 can be melted and molded, the molded product has problems with physical properties such as strength, elongation, and heat resistance, as well as chemical properties such as long-term durability, making it difficult to use as is on its own in various products.

[0005] Patent document 2 describes a method for producing an improved recycled polyolefin material. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6735885 [Patent Document 2] Japanese Patent Publication No. 2024-151606 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a melt-mold polyolefin material and molded article that exhibits excellent physical properties and chemical properties such as long-term durability. [Means for solving the problem]

[0008] The gist of this invention is as follows:

[0009] [1] A melt-mold polyolefin material comprising 10 to 90 parts by weight of a recycled polyolefin material with an MFR of 0.2 g / 10 min or more derived from cross-linked polyolefins, and 90 to 10 parts by weight of a polyolefin material not derived from recycled materials (provided that the total of the recycled polyolefin material and the polyolefin material not derived from recycled materials is 100 parts by weight).

[0010] [2] A melt-mold polyolefin material of [1] comprising 30 to 80 parts by weight of the recycled polyolefin material and 70 to 20 parts by weight of a polyolefin material not derived from the recycled material (provided that the total of the recycled polyolefin material and the polyolefin material not derived from the recycled material is 100 parts by weight).

[0011] [3] The recycled polyolefin material is a melt-mold polyolefin material of [1] comprising crosslinked polyethylene, polypropylene, or polybutene.

[0012] [4] A melt-mold polyolefin material of the recycled polyolefin material having a gel fraction of 25% or less [1].

[0013] [5] The recycled polyolefin material is a melt-mold polyolefin material of [1] obtained by mixing a polyethylene resin containing silane-crosslinked polyethylene with an additive and applying shear stress and heat in an extruder to break the crosslinking points of the silane-crosslinked polyethylene.

[0014] [6] Further, a melt-moldable polyolefin material containing 1 to 30 parts by weight or less of at least one of a colorant, an antioxidant, and a lubricant with respect to a total of 100 parts by weight of the recycled polyolefin material and a polyolefin material not derived from a recycled material.

[0015] [7] A molded article of the melt-moldable polyolefin material according to any one of [1] to [6].

[0016] [8] The molded article according to [7], which is a tubular molded article.

[0017] [9] The molded article according to [7], which is a flexible corrugated tube.

[0018]

[10] The molded article according to [8] or [9], in which a layer made of another material is provided on at least one of the outer peripheral surface and the inner peripheral surface of the tubular molded article. [Advantages of the Invention]

[0019] The polyolefin material of the present invention contains 10 to 90% of a recycled polyolefin material derived from a crosslinked polyolefin (hereinafter sometimes simply referred to as a recycled polyolefin material) and 90 to 10% of a polyolefin material not derived from a recycled material (hereinafter sometimes referred to as a virgin polyolefin material), and thus is melt-moldable. [Embodiments for Carrying Out the Invention]

[0020] Hereinafter, the present invention will be described in more detail.

[0021] The polyolefin material of the present invention contains a recycled polyolefin material and a virgin polyolefin material.

[0022] As the crosslinked polyolefin in the recycled polyolefin material, crosslinked polyethylene, crosslinked polypropylene, or crosslinked polybutylene is preferable.

[0023] While silane crosslinking is a commonly known method for crosslinking crosslinked polyolefins, other methods such as crosslinking using peroxides or electron beams may also be used.

[0024] The recycled polyolefin material used in this invention has an MFR of 0.2 g / 10 min or more, preferably 0.3 to 5.0 g / 10 min, and particularly preferably 0.4 to 2.0 g / 10 min. An MFR of 0.4 g / 10 min or more in the recycled polyolefin material results in good moldability of the polyolefin material.

[0025] Furthermore, the recycled polyolefin material used in this invention preferably has a gel fraction of 25% or less, and more preferably 15% or less. Using a material with a gel fraction of 25% or less results in good processability.

[0026] Specifically, the recycled polyolefin material used in this invention is preferably the composition described in Patent Document 2.

[0027] The composition described in Patent Document 2 is manufactured as follows: A polyethylene resin containing silane-crosslinked polyethylene and an additive are mixed in a twin-screw extruder to produce a polymer compound before thermoplasticization. The polyethylene resin may be silane-crosslinked polyethylene alone, or it may be silane-crosslinked polyethylene combined with one or more types of polyethylene selected from peroxide-crosslinked polyethylene, high-density polyethylene, and low-density polyethylene.

[0028] The polymer compound is subjected to shear stress and heat inside a twin-screw extruder, which breaks the crosslinking points of the silane-crosslinked polyethylene and causes it to thermoplasticize.

[0029] Subsequently, the thermoplasticized polymer compound is discharged to the outside of the twin-screw extruder and becomes a recycled polyolefin material composition.

[0030] Specifically, the composition described in Patent Document 2 can be the series of products with the product name XLLS, produced by Repeplus Co., Ltd. (Yokohama City, Kanagawa Prefecture).

[0031] This recycled polyolefin material can be manufactured by the following method (Patent Document 2).

[0032] <Method for manufacturing recycled polyolefin material> A method for producing recycled polyolefin material by thermoplasticizing cross-linked polyethylene using an extruder, A mixing step of mixing the aforementioned crosslinked polyethylene, first non-crosslinked polyethylene, and an additive to produce a mixture, A thermoplasticization step in which the mixture is introduced from the first input section of the extruder and heat and shear stress are applied to thermoplasticize the crosslinked polyethylene, The process includes a kneading step in which a second non-crosslinked polyethylene is added to the mixture after the thermoplasticization step from the second input section of the extruder and kneaded, The amount of the first non-crosslinked polyethylene in the mixing step is 1 to 5 parts by weight per 100 parts by weight of the crosslinked polyethylene. The additive comprises at least one non-crosslinked polymer compound selected from ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, ethylene ethyl acrylate copolymer, ethylene methyl methacrylate copolymer, or ethylene ethyl methacrylate copolymer. The amount of the additive is 0.1 to 3 parts by weight per 100 parts by weight of the cross-linked polyethylene. The shear stress in the thermoplasticization process is 10,000 to 15,000 s -1 Generate at this shear rate for 5 to 30 seconds. A method for producing recycled polyolefin material, wherein the amount of the second non-crosslinked polyethylene introduced in the kneading step is 50 to 150 parts by weight per 100 parts by weight of the crosslinked polyethylene.

[0033] In the present invention, the virgin polyolefin material used together with the recycled polyolefin material is preferably polyethylene, polypropylene, or polybutylene that is not derived from recycled materials, and polyethylene is particularly preferred.

[0034] The polyethylene used in the virgin polyolefin material can be either high-density polyethylene (HDPE) or low-density polyethylene (LDPE). Linear low-density polyethylene (LLDPE) is preferred as the low-density polyethylene.

[0035] The total amount of recycled polyolefin material and virgin polyolefin material is preferably 10 to 90 parts by weight, particularly 20 to 80 parts by weight, in a total of 100 parts by weight. Increasing the proportion of recycled polyolefin material can promote the reuse of crosslinked polyolefin material.

[0036] Furthermore, by using a virgin polyolefin material ratio of 10 parts by weight or more, the resulting product will have good moldability and physical properties.

[0037] In this invention, additives such as antioxidants and colorants may be added to the recycled polyolefin material and the virgin polyolefin material. These additives are preferably added in the form of a masterbatch.

[0038] The amount of antioxidant masterbatch, colorant, and lubricant added per 100 parts by weight of the total recycled polyolefin material and virgin polyolefin material is preferably 1 to 30 parts by weight or less, and more preferably 2 to 10 parts by weight or less.

[0039] A material comprising recycled polyolefin material and virgin polyolefin material, along with additives added as needed, is fed into an extruder, preferably heated to 150-210°C, kneaded, and then extruded.

[0040] Examples of molded products include pipes, tubes, bellows pipes, and other types of pipes, as well as combine pipes containing multiple inner pipes within an outer pipe. The pipes may have a circular, elliptical, or polygonal cross-section. Examples include straight pipes and corrugated pipes, which have alternating annular peaks (convex radially outward) and annular valleys (concave radially outward) formed along the axial direction to create a bellows-like structure. In the case of corrugated pipes, the peaks and valleys may be offset at a certain angle from the axial direction, creating an oblique shape (however, from the viewpoint of bending construction, a bellows-like structure is preferable).

[0041] The above-mentioned pipe may be a single-layer pipe or a multi-layer pipe made of laminated materials. It may also be a multi-layer pipe with different color tones. Examples of other materials include chlorinated polyolefin, PVC, styrene resin, amide resin, fluororesin, and silicone resin. An adhesive layer may be provided between the layers.

[0042] The molding method is not limited to extrusion molding; blow molding may also be used.

[0043] It is preferable to use an extruder with a barrel diameter of approximately 25 mm to 200 mm (single-screw, twin-screw, including conical type, etc.).

[0044] An oxygen permeability-preventing layer made of polyvinyl alcohol copolymer or the like may be provided.

[0045] Additionally, heat-resistant materials may be used for the inner layer, or light-shielding materials may be combined with it. [Examples]

[0046] Examples and comparative examples are described below.

[0047] [Materials used] The materials used in the following examples and comparative examples are as follows:

[0048] <Recycled polyolefin material> Recycled polyolefin material (A): Recycled polyethylene material containing cross-linked polyethylene-derived components manufactured by Repeeplus Co., Ltd. (Prototype number: XLLS-A, MFR = 0.53 g / 10 min, density 0.935 g / cm³) 3 (Contains approximately 40% cross-linked polyethylene and 15% gel) Recycled polyolefin material (B): Recycled polyethylene material containing cross-linked polyethylene-derived components manufactured by Repeeplus Co., Ltd. (Prototype number: XLLS-B, MFR = 0.36 g / 10 min, density 0.935 g / cm³) 3 (Contains approximately 40% cross-linked polyethylene and 18% gel) Recycled polyolefin material (C): Recycled polyethylene material containing cross-linked polyethylene-derived components manufactured by Repeeplus Co., Ltd. (Prototype number: XLLS-C, MFR = 0.25 g / 10 min, density 0.935 g / cm³) 3 (Contains approximately 40% cross-linked polyethylene and 16% gel) Recycled polyolefin material (D): Recycled polyethylene material containing cross-linked polyethylene-derived components manufactured by Repeeplus Co., Ltd. (Prototype number: XLLS-D, MFR = 0.18 g / 10 min, density 0.935 g / cm³) 3 (Contains approximately 40% cross-linked polyethylene and 16% gel) Recycled polyolefin material (E): Recycled polyethylene material containing cross-linked polyethylene-derived components manufactured by Repeeplus Co., Ltd. (Prototype number: XLLS-E, MFR = 0.03 g / 10 min, density 0.935 g / cm³) 3 (Cross-linked polyethylene content: approximately 40%, gel fraction: 40%) Recycled polyolefin material (F): Recycled polyethylene material containing cross-linked polyethylene-derived components manufactured by Repeeplus Co., Ltd. (Prototype number: XLLS-F, MFR = 0.06 g / 10 min, density 0.937 g / cm³) 3 (Cross-linked polyethylene content: approximately 40%, gel fraction: 21%)

[0049] The recycled polyolefin material contains recycled polyethylene other than cross-linked polyethylene, which causes a wide range of physical properties. Therefore, the above physical property values are the measured values of the lots used.

[0050] <Virgin Polyethylene> HDPE: Density 0.938 g / cm 3 , MFR (190°C - 2.16 kg) 0.2 g / 10 min LLDPE: Density 0.922 g / cm 3 , MFR (190°C - 2.16 kg) 0.7 g / 10 min

[0051] <Additive> Color masterbatch: Masterbatch containing titanium oxide, various pigments, and dyes Black masterbatch: Masterbatch containing carbon black, etc. Antioxidant masterbatch: Masterbatch containing phenolic antioxidants, etc. Lubricant masterbatch: Masterbatch containing stearic acid-based or metal soap-based lubricants

[0052] <Forming Method> Each material was supplied to an extrusion molding machine (TR60 manufactured by OLMAS) at the blending ratio shown in Table 1, kneaded and melted at about 180°C, and a bellows tube (outer diameter: diameter of the mountain part 16.2 mm, inner diameter 12.4 mm, pitch of the mountain part 3.3 mm, wall thickness 0.35 mm) was formed by continuous extrusion molding.

[0053] <Evaluation Method and Criteria>

[0054] Surface condition: Observed visually and evaluated in five grades. The evaluation criteria are as follows. Note that the following unevenness refers to the unevenness on the flat part of the product surface, not the unevenness of the bellows tube. A: (Extremely good): The level where no minute unevenness can be felt even by palpation B: (Somewhat good): The level where minute unevenness can be felt by palpation C: (Good): The level where no minute unevenness can be confirmed visually D: (Slightly inferior): Minute irregularities can be seen with the naked eye. E: (Very poor): Surface irregularities are visible even to the naked eye.

[0055] Compressive strength: The molded bellows tube was used as the test specimen, and the strength was measured using our own method based on BLTPI-07: Compression recovery test of sheath tubes (the clamping jig was 10 mm thick with a rounded tip). Laboratory temperature: 23℃, Sample length: 150mm, Pressurization rate: 12mm / min The maximum load was measured when the outer diameter was compressed to a rate of 30% or more in 30 seconds.

[0056] Furthermore, to confirm the effectiveness of the acid-resistant and weather-resistant material, a 120°C exposure test was conducted, and the change in compressive strength over time was investigated. Since the product strength increases due to the annealing effect at 120°C, the compressive strength after 120°C exposure was used for comparison.

[0057] <Result> The results are shown in Table 1.

[0058] [Table 1]

[0059] <Consideration> (1) Example 1 involves adding 20 parts by weight of virgin HDPE material to 80 parts by weight of recycled polyethylene material (A) with MFR = 0.53 g / 10 min, and then adding a colored masterbatch (MB), an antioxidant masterbatch, and a lubricant masterbatch. The surface appearance is good and the compressive strength is high.

[0060] (2) Example 2 is the same as Example 1, but with a black masterbatch added instead of a colored masterbatch to improve weather resistance, and without a lubricant masterbatch. Even without a lubricant, the balance and surface appearance are good, and the compressive strength is also high. However, because it is black, it is thought that there are limitations on its applications.

[0061] (3) Example 3 is the same as Example 1 but with 50 parts by weight of recycled polyolefin material and 50 parts by weight of virgin HDPE material. The surface appearance is good and the compressive strength is high. However, the cost is higher because the proportion of virgin material is high.

[0062] (4) Example 4 had the same formulation as Example 1 except that a lubricant masterbatch was not used. The compressive strength was high, but it was slightly difficult to mold, and the surface condition was slightly worse.

[0063] (5) Example 5 is a variation in which virgin LLDPE material was used instead of virgin HDPE in Example 1. The surface appearance was good, but the compressive strength was slightly lower compared to Example 1.

[0064] (6) Example 6 is the same as in Example 1, but the recycled polypropylene material is replaced with recycled polyolefin material (B) with an MFR of 0.36 g / 10 min. Due to the low MFR, it was slightly more difficult to mold and the surface condition was slightly worse.

[0065] (7) Example 7 is the same as Example 6 but without the addition of a lubricant masterbatch. Compared to Example 6, it was more difficult to mold and the surface condition was worse.

[0066] (8) Example 8 is the same as in Example 1, but the recycled poly material is replaced with recycled polyolefin material (C) with MFR = 0.25 g / 10 min. Due to the low MFR, it was slightly more difficult to mold and the surface condition was slightly worse.

[0067] (9) Comparative Example 1 is obtained by changing the recycled poly material in Example 1 to a recycled polyolefin material (D) with MFR = 0.18 g / 10 min. The moldability was poor and the surface condition was poor.

[0068] (10) Comparative Example 2 is the same as in Example 1, but the recycled poly material is replaced with a recycled polyolefin material (E) with an MFR of 0.03 g / 10 min. The moldability was very poor, and it was not possible to obtain a product.

[0069] (11) Comparative Example 3 uses recycled polyolefin material (F) with MFR = 0.06 g / 10 min instead of virgin polyethylene material as in Example 1. The surface condition was poor and the moldability was also poor.

Claims

1. A melt-mold polyolefin material comprising 10 to 90 parts by weight of recycled polyolefin material with an MFR of 0.2 g / 10 min or more derived from cross-linked polyolefins, and 90 to 10 parts by weight of polyolefin material not derived from recycled materials (provided that the total of the recycled polyolefin material and the non-recycled polyolefin material is 100 parts by weight).

2. A melt-mold polyolefin material according to claim 1, comprising 30 to 80 parts by weight of the recycled polyolefin material and 70 to 20 parts by weight of a polyolefin material not derived from the recycled material (provided that the total of the recycled polyolefin material and the polyolefin material not derived from the recycled material is 100 parts by weight).

3. The recycled polyolefin material is a melt-mold polyolefin material according to claim 1, comprising crosslinked polyethylene, polypropylene, or polybutene.

4. The melt-mold polyolefin material according to claim 1, wherein the gel fraction of the recycled polyolefin material is 25% or less.

5. The recycled polyolefin material is a melt-mold polyolefin material according to claim 1, wherein the recycled polyolefin material is obtained by mixing a polyethylene resin containing silane-crosslinked polyethylene with an additive, and applying shear stress and heat in an extruder to break the crosslinking points of the silane-crosslinked polyethylene.

6. Furthermore, the melt-mold polyolefin material according to claim 1 further comprises at least one of a colorant, an antioxidant, and a lubricant in an amount of 1 to 30 parts by weight or less per 100 parts by weight of the total of the recycled polyolefin material and the non-recycled polyolefin material.

7. A molded article made of a melt-mold polyolefin material according to any one of claims 1 to 6.

8. The molded product according to claim 7, wherein the molded product is a tubular molded product.

9. The molded product according to claim 7, wherein the molded product is a flexible corrugated tube.

10. The molded article according to claim 8 or 9, wherein at least one of the outer and inner surfaces of the tubular molded article is provided with a layer made of another material.

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