Flame-retardant polypropylene resin composition and molded body

Abstract

To provide a flame-retardant polypropylene resin composition which achieves both excellent designability and flame retardancy.SOLUTION: A flame-retardant polypropylene resin composition contains a polypropylene resin, 0.5 wt.% or less of carbon black, and a bromine-based flame retardant.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a flame-retardant polypropylene resin composition and a molded article thereof. [Background technology]

[0002] Polyolefin resins, which offer excellent strength, rigidity, moldability, and chemical resistance, are widely used in durable consumer goods such as home appliances, office equipment, information devices, and communication devices to improve product functionality, weight, and safety.

[0003] For example, Patent Document 1 discloses a thermoplastic resin composition containing 40 to 85 mass % of (A) a thermoplastic resin and 60 to 15 mass % of (B) carbon black, and further containing (C) a brominated organic phosphate flame retardant and (D) antimony trioxide as flame retardants, and describes that the (A) thermoplastic resin can be an olefin-based resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-255900 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, when a molded product is produced using resin recovered from plastic waste, black spots are likely to appear on the surface of the molded product due to the influence of foreign matter contained in the plastic waste, which can result in poor design. If a molded product is produced using a resin composition containing carbon black, as in the technology described in Patent Document 1, the black spots become less noticeable, improving design, but on the other hand, flame retardancy may be reduced.

[0006] An object of one aspect of the present invention is to provide a flame-retardant polypropylene resin composition that combines excellent design and flame retardancy. [Means for solving the problem]

[0007] In order to solve the above problems, a flame-retardant polypropylene resin composition according to one aspect of the present invention comprises a polypropylene resin, 0.5% by weight or less of carbon black, and a brominated flame retardant. [Effects of the Invention]

[0008] According to one aspect of the present invention, a flame-retardant polypropylene resin composition that combines excellent design and flame retardancy can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram showing the appearance of the molded bodies obtained in Comparative Example 1 and Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less."

[0011] 1. Flame-retardant polypropylene resin composition A flame-retardant polypropylene resin composition according to one embodiment of the present invention includes a polypropylene resin, 0.5% by weight or less of carbon black, and a brominated flame retardant. Hereinafter, the flame-retardant polypropylene resin composition may also be simply referred to as a "resin composition."

[0012] The resin composition contains carbon black, so that foreign matter mixed in the polypropylene resin is not noticeable, resulting in excellent design. Although a large amount of carbon black may reduce flame retardancy, the resin composition contains carbon black at a content of 0.5% by weight or less and contains a brominated flame retardant, so that both excellent design and flame retardancy can be achieved.

[0013] <1-1. Polypropylene resin> The resin composition contains a polypropylene resin. Examples of the polypropylene resin include a propylene homopolymer, a propylene-ethylene block copolymer, a propylene-ethylene random copolymer, a propylene-butene block copolymer, a propylene-butene random copolymer, a propylene-α-olefin block copolymer, and a propylene-α-olefin graft copolymer. Examples of the α-olefin include α-olefins having 3 to 20 carbon atoms, such as propylene, butene, and pentene. When the polypropylene resin is a copolymer, the structural units derived from propylene as a monomer may account for 50% by weight or more, 70% by weight or more, or even 90% by weight or more of 100% by weight of the structural units constituting the polypropylene resin. The polypropylene resin may also be a mixture of these resins.

[0014] The polypropylene resin may be recovered from used products or equipment having polypropylene resin components. This allows for the reuse of waste polypropylene resin recovered from used products or equipment. This effect also contributes to the achievement of, for example, Goal 12 of the Sustainable Development Goals (SDGs) advocated by the United Nations, "Ensure sustainable consumption and production patterns." In this specification, polypropylene resin recovered from used products or equipment is also referred to as "used polypropylene resin." The polypropylene resin contained in the resin composition may be virgin polypropylene resin or a mixture of virgin polypropylene resin and used polypropylene resin.

[0015] Examples of used products or devices include home appliances such as washing machines, refrigerators, air conditioners, and televisions, as well as office automation equipment, information equipment, and communication equipment. For example, the polypropylene resin may be polypropylene resin recovered from the outdoor unit of a used air conditioner. The outdoor unit of an air conditioner is installed outdoors. Therefore, polypropylene resin recovered from the outdoor unit of an air conditioner tends to have more foreign matter, such as sand and dust, which can cause black spots, attached to it, and to be more severely deteriorated, compared to polypropylene resin recovered from products or devices used indoors. Even polypropylene resin recovered from such outdoor units of an air conditioner can be reused by making it into the resin composition.

[0016] The content of the polypropylene resin in the resin composition can be determined so that the total content of the polypropylene resin, including the carbon black, the brominated flame retardant, the optional flame retardant aid, and other components, is 100% by weight. For example, the lower limit of the polypropylene resin content may be 70% by weight or more, 75% by weight or more, or 80% by weight or more. The upper limit of the polypropylene resin content may be 95% by weight or less, 90% by weight or less, or 85% by weight or less.

[0017] <1-2. Carbon Black> The resin composition contains 0.5% by weight or less of carbon black, such as ketjen black, furnace black, channel black, and acetylene black.

[0018] The upper limit of the carbon black content in the resin composition is preferably 0.4% by weight or less, more preferably 0.3% by weight or less, and even more preferably 0.2% by weight or less from the viewpoint of flame retardancy. The lower limit of the carbon black content is more than 0% by weight, and from the viewpoint of design, it is preferably 0.01% by weight or more, more preferably 0.03% by weight or more, and even more preferably 0.05% by weight or more.

[0019] <1-3. Brominated flame retardants> The resin composition contains a brominated flame retardant. In this specification, the term "brominated flame retardant" refers to a substance that contains a bromine atom and can impart flame retardancy to the resin composition.

[0020] Examples of brominated flame retardants include bis(pentabromophenyl)ethane, tetrabromobisphenol A, tetrabromobisphenol A·bis(dibromopropyl ether), tetrabromobisphenol S, tetrabromobisphenol S·bis(dibromopropyl ether), 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, ethylenebistetrabromophthalimide, bis(pentabromophenyl)ethane, and brominated epoxy oligomers. These may be used alone or in combination. From the viewpoint of further enhancing flame retardancy, it is preferable that the brominated flame retardant be at least one selected from the group consisting of tetrabromobisphenol A and tetrabromobisphenol S.

[0021] From the viewpoint of flame retardancy, the lower limit of the content of the brominated flame retardant in the resin composition is preferably 11% by weight or more, more preferably 12% by weight or more, and from the viewpoint of heat aging resistance, the upper limit of the content of the brominated flame retardant is preferably less than 20% by weight, more preferably 15% by weight or less.

[0022] <1-4. Flame retardant synergists> From the viewpoint of improving flame retardancy, the resin composition may contain a flame retardant aid. Examples of the flame retardant aid include antimony compounds such as antimony trioxide, antimony pentoxide, and antimony trichloride, boron compounds such as zinc metaborate, zinc tetraborate, and zinc borate, zirconium oxide, tin oxide, and molybdenum oxide. Among these, antimony compounds are preferred, as they are suitable as flame retardant aids to be used in combination with bromine-based flame retardants, and antimony trioxide is more preferred.

[0023] From the viewpoint of more sufficiently improving flame retardancy, the content of the flame retardant synergist in the resin composition is preferably at least one-third of the content of the brominated flame retardant by weight. Also, the content of the flame retardant synergist is preferably not more than one-half of the content of the brominated flame retardant by weight. For example, the content of the flame retardant synergist may be 3.7 to 8 wt%.

[0024] <1-5. Other ingredients> The resin composition may optionally contain other components within the scope of not impairing the effects of the present invention, such as antioxidants (phenolic, phosphorus, sulfur, etc.), anti-drip agents (fluorine-based resins, etc.), ultraviolet absorbers (benzophenone, hindered amine, etc.), fillers (glass fiber, mica, calcium carbonate, barium sulfate, etc.), lubricants, plasticizers, stabilizers, release agents, antistatic agents, colorants (pigments, dyes, etc.), metal deactivators, neutralizers, dispersants, etc.

[0025] <1-6. Method for producing flame-retardant polypropylene resin composition> The method for producing the resin composition is not particularly limited, and may include, for example, a step of mixing a polypropylene resin, 0.5% by weight or less of carbon black, a brominated flame retardant, and optionally a flame retardant aid and other components, wherein the carbon black is mixed so that its content in 100% by weight of the resin composition is 0.5% by weight or less.

[0026] The method for producing the resin composition may also include a step of recovering the polypropylene resin from a used product or device having a polypropylene resin component. For example, the used product or device may be disassembled to obtain the polypropylene resin component, and the polypropylene resin component may be crushed to obtain a crushed product. The crushed product may be purified to obtain the polypropylene resin.

[0027] [2. Molded body] A molded article according to one embodiment of the present invention includes the flame-retardant polypropylene resin composition described above. In other words, the molded article may be a molded article obtained by molding the resin composition described above. For example, a molded article can be obtained from the resin composition by melt molding, extrusion molding, injection molding, or the like. The molded article may be composed solely of the resin composition described above, or may contain portions containing other materials. The molded article can be used for housings or mechanical parts of home appliances such as washing machines, refrigerators, air conditioners, and televisions, as well as office equipment, information equipment, and communication equipment.

[0028] 〔summary〕 The flame-retardant polypropylene resin composition according to the first aspect of the present invention contains a polypropylene resin, 0.5% by weight or less of carbon black, and a brominated flame retardant.

[0029] According to the above-mentioned configuration, by combining a specific amount of carbon black with a brominated flame retardant, it is possible to obtain a molded article that has both excellent design and flame retardancy.

[0030] A flame-retardant polypropylene resin composition according to a second aspect of the present invention may be the flame-retardant polypropylene resin composition according to the first aspect, wherein the polypropylene resin is recovered from used products or equipment having polypropylene resin members.

[0031] According to the above configuration, polypropylene resin recovered from used products or equipment, which are waste materials, can be reused.

[0032] A flame-retardant polypropylene resin composition according to a third aspect of the present invention may be the flame-retardant polypropylene resin composition according to the second aspect, wherein the polypropylene resin is a polypropylene resin recovered from the outdoor unit of a used air conditioner.

[0033] According to the above-mentioned configuration, even polypropylene resin recovered from the outdoor unit of an air conditioner, which tends to deteriorate rapidly, can be reused by making it into the resin composition.

[0034] The flame-retardant polypropylene resin composition according to Aspect 4 of the present invention, in any one of Aspects 1 to 3, may have a brominated flame retardant content of 11% by weight or more.

[0035] According to the above-mentioned configuration, the flame retardancy of the obtained molded article can be further improved.

[0036] The flame-retardant polypropylene resin composition according to a fifth aspect of the present invention, in any one of the above first to fourth aspects, may have a brominated flame retardant content of less than 20% by weight.

[0037] According to the above-mentioned configuration, a molded article having excellent heat aging resistance can be obtained.

[0038] A flame-retardant polypropylene resin composition according to a sixth aspect of the present invention may be any one of the first to fifth aspects, in which the brominated flame retardant is at least one selected from the group consisting of tetrabromobisphenol A and tetrabromobisphenol S.

[0039] According to the above configuration, the flame retardancy can be further improved.

[0040] The flame-retardant polypropylene resin composition according to Aspect 7 of the present invention, in any one of Aspects 1 to 6 above, may contain a flame-retardant auxiliary.

[0041] According to the above configuration, the flame retardancy can be further improved.

[0042] The flame-retardant polypropylene resin composition according to an eighth aspect of the present invention may be the composition of the seventh aspect, wherein the content of the flame-retardant synergist is at least one-third of the content of the brominated flame retardant by weight.

[0043] According to the above configuration, the flame retardancy can be improved more suitably.

[0044] A ninth aspect of the present invention relates to the flame-retardant polypropylene resin composition of the seventh or eighth aspect, wherein the flame-retardant synergist is antimony trioxide.

[0045] According to the above-mentioned configuration, antimony trioxide is compatible with bromine-based flame retardants, and therefore, flame retardancy can be improved more suitably.

[0046] A molded article according to a tenth aspect of the present invention comprises the flame-retardant polypropylene resin composition according to any one of the first to ninth aspects.

[0047] According to the above configuration, by using a flame-retardant polypropylene resin composition containing a specific amount of carbon black and a brominated flame retardant, it is possible to achieve both excellent design and flame retardancy in a molded product.

[0048] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. [Example]

[0049] An embodiment of the present invention will now be described.

[0050] [Evaluation method] <Design evaluation method> The brightness of the ASTM-compliant bending test specimens described below was measured using a color difference meter (testing machine: ZE-7700, manufactured by Nippon Denshoku Industries Co., Ltd.). The lower the brightness, the less noticeable black spots caused by foreign matter, and the better the design.

[0051] <Flame retardancy evaluation method> A vertical flame test was conducted using a flame retardancy test piece conforming to the UL94 standard described below, and the flammability classification was determined. In the UL94 standard, flame retardancy decreases in the order of V-0, V-1, and V-2.

[0052] <Test method for heat aging resistance> Oven test (Testing machine: DKM600 Yamato Scientific Co., Ltd. constant temperature incubator) A bending test was performed in accordance with JIS K 7171 using a bending test specimen conforming to ASTM (described below), and bending strength was measured. This was taken as the initial bending strength. Similarly, bending test specimens prepared were placed in a constant temperature incubator set at 120°C or higher, removed after each time period, and a bending test was performed in accordance with JIS K 7171 using the specimen to measure bending strength. The time at which the bending strength decreased to less than 90% of the initial bending strength was defined as the property deterioration time and evaluated. The initial bending strengths of all test specimens were comparable. The longer the property deterioration time, the better the heat aging resistance was judged to be.

[0053] [Materials used] <Component (A)> Polypropylene resin recovered from used home appliances (washing machines, refrigerators, and air conditioners (outdoor units)). <(B) component> Brominated flame retardant (tetrabromobisphenol) <(C) component> Flame retardant synergist (antimony trioxide) <(D) component> carbon black [Examples 1 to 6, Comparative Examples 1 and 2] Used home appliances (washing machines, refrigerators, and air conditioners (outdoor units)) were collected and manually disassembled. Polypropylene resin parts were collected from the used home appliances and further crushed to particles of approximately 10 mm to obtain crushed material. Component (A) was obtained from the crushed material.

[0054] Next, components (A), (B), (C), (D), and other components were added and mixed in the blending ratios shown in Table 1 to obtain a mixture. Next, the mixture was heated, melted, and kneaded at a set temperature of 200°C using a twin-screw melt-kneading extruder, and the melt-kneaded mixture was extrusion-molded into strands. The resulting molded product was then cut to obtain pellets of a flame-retardant polypropylene resin composition.

[0055] The above-mentioned pelletized flame-retardant polypropylene resin composition was injection molded under the injection molding conditions of a set temperature of 220°C to prepare a test piece for a bending test in accordance with ASTM.Furthermore, it was injection molded under the injection molding conditions of a set temperature of 220°C to prepare a test piece (thickness 1.5 mm) for measuring flame retardancy in accordance with the UL94 standard.

[0056] [Evaluation results] The compositions and evaluation results of the examples and comparative examples are shown in Table 1. Note that the compositions in Table 1 are shown with the entire resin composition taken as 100% by weight, but small amounts of additives that do not affect the design and flame retardancy are omitted.

[0057] [Table 1]

[0058] Examples 1 to 3, which used resin compositions containing 0.5 wt% or less of carbon black and a brominated flame retardant, were excellent in design and flame retardancy, and also in heat aging resistance. On the other hand, Comparative Example 1, which used a resin composition containing no carbon black, was inferior in design compared to the examples.

[0059] Fig. 1 is a diagram showing the appearance of the molded bodies obtained in Comparative Example 1 and Example 2. Fig. 1 shows that the molded body of Comparative Example 1, which has a brightness of 61, has more noticeable black spots than the molded body of Example 2, which has a brightness of 32.

[0060] Furthermore, Comparative Example 2, in which the carbon black content exceeded 0.5% by weight, was inferior in flame retardancy and heat aging resistance compared to Examples 1 to 3. Furthermore, in Examples 4 to 6, in which the carbon black content was kept at 0.5% by weight or less and the contents of the brominated flame retardant and flame retardant aid were changed, molded articles with excellent design and flame retardancy were obtained. [Industrial Applicability]

[0061] The present invention can be used for molded articles and the like that require designability and flame retardancy.

Claims

1. A flame-retardant polypropylene resin composition comprising a polypropylene resin, 0.5% by weight or less of carbon black, and a brominated flame retardant.

2. The flame-retardant polypropylene resin composition according to claim 1, wherein the polypropylene resin is a polypropylene resin recovered from used products or equipment having polypropylene resin components.

3. The flame-retardant polypropylene resin composition according to claim 2, wherein the polypropylene resin is a polypropylene resin recovered from an outdoor unit of a used air conditioner.

4. 2. The flame-retardant polypropylene resin composition according to claim 1, wherein the content of the brominated flame retardant is 11% by weight or more.

5. 2. The flame-retardant polypropylene resin composition according to claim 1, wherein the content of the brominated flame retardant is less than 20% by weight.

6. 2. The flame-retardant polypropylene resin composition according to claim 1, wherein the brominated flame retardant is at least one selected from the group consisting of tetrabromobisphenol A and tetrabromobisphenol S.

7. The flame-retardant polypropylene resin composition according to claim 1, further comprising a flame-retardant synergist.

8. 8. The flame-retardant polypropylene resin composition according to claim 7, wherein the content of the flame-retardant synergist is at least one-third of the content of the brominated flame retardant by weight.

9. The flame-retardant polypropylene resin composition according to claim 7, wherein the flame-retardant synergist is antimony trioxide.

10. A molded article obtained by molding the flame-retardant polypropylene resin composition according to any one of claims 1 to 9.

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