Resin part for writing implement and writing implement provided with same

Abstract

The purpose of the present invention is to provide a resin part for a writing implement that utilizes a recycled polyolefin resin as a raw material and has certain physical properties.　This resin part for a writing implement contains a recycled polyolefin resin composition, the recycled polyolefin resin composition containing a recycled polyolefin resin and a slidability-imparting additive. The slidability-imparting additive contains silicone and / or a silicone-containing copolymer, and the total content of the silicone and a constituent unit derived from silicone in the silicone-containing copolymer is 1.0-4.0 parts by mass with respect to 100 parts by mass of the recycled polyolefin resin.

Description

Resin parts for writing instruments and writing instruments equipped with them

[0001] The present invention relates to a resin part for a writing instrument and a writing instrument equipped with the same.

[0002] In recent years, as an environmental measure, attention has been focused on the use of post-consumer materials, which are recycled by collecting used products from the market. Recycled polyolefin resin is widely used as this post-consumer material. Writing instruments are one type of resin product that contains many resin parts, and the following writing instruments are known as writing instruments made from polyolefin resin.

[0003] For example, Patent Document 1 discloses a felt-tip pen whose entire components are made of block-type polypropylene resin in order to ensure the strength of the press-fit and mating parts and the hardness of the entire shaft.

[0004] Furthermore, the rotor of a knock-type writing instrument is required to have slidability in order to advance the writing lead.Patent Document 2 discloses a moving member for a writing instrument in which a sliding agent is mixed into a resin, the moving member for a writing instrument being formed by molding a polycarbonate composition containing 100 parts by weight of polycarbonate resin (A) with 1 to 20 parts by weight of sliding agent (B) and 0.1 to 0.8 parts by weight of sliding agent (C), the moving member being characterized in that a molded edge having a thickness of 3 mm injection molded from the composition has a light transmittance of 80% or more in accordance with JIS K7361.

[0005] JP 2000-025381 A JP 2015-217646 A

[0006] Recycled polyolefin resins as post-consumer materials often contain a variety of polyolefin resins, and therefore their physical properties are often not consistent. Therefore, when recycled polyolefin resins are used as raw materials, it is difficult to obtain resin parts for writing instruments with consistent physical properties.

[0007] Therefore, an object of the present invention is to provide resin parts for writing instruments that use recycled polyolefin resin as a raw material and have certain physical properties.

[0008] In the present invention, in order to obtain resin parts for writing instruments made from recycled polyolefin resin, attention was focused on improving the surface properties, particularly the sliding properties, of recycled polyolefin resin.

[0009] The present invention achieves the above object by the following means.

[0010] Aspect 1: A resin part for a writing instrument, comprising a recycled polyolefin resin composition, wherein the recycled polyolefin resin composition comprises a recycled polyolefin resin and a sliding property-imparting additive, wherein the sliding property-imparting additive comprises silicone and / or a silicone-containing copolymer, and the total content of structural units derived from the silicone and the silicone-containing copolymer is 1.0 to 4.0 parts by mass per 100 parts by mass of the recycled polyolefin resin. Aspect 2: The resin part for a writing instrument according to Aspect 1, wherein the recycled polyolefin resin composition has a dynamic friction coefficient of 0.10 to 0.40. Aspect 3: The resin part for a writing instrument according to Aspect 1 or 2, wherein the recycled polyolefin resin composition is contained in an amount of 60 parts by mass or more, relative to 100 parts by mass of the entire resin part for the writing instrument. Aspect 4: A writing instrument comprising the resin part for a writing instrument according to any one of Aspects 1 to 3.

[0011] According to the present invention, it is possible to provide resin parts for writing instruments having certain physical properties by using recycled polyolefin resin as a raw material.

[0012] FIG. 1 is a schematic diagram for explaining the resin part for a writing instrument and the writing instrument of the present invention (FIG. 1(A): schematic diagram of the appearance of the writing instrument, FIG. 1(B): schematic diagram of the cross section of the writing instrument shown in FIG. 1(A)).

[0013] Hereinafter, an embodiment of the present invention will be described in detail. Note that the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the gist of the present invention. In addition, in the description of the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted.

[0014] <<Resin Parts for Writing Instruments>> The resin parts for writing instruments of the present invention comprise a recycled polyolefin resin composition, wherein the recycled polyolefin resin composition comprises a recycled polyolefin resin and a sliding property-imparting additive, wherein the sliding property-imparting additive comprises silicone and / or a silicone-containing copolymer, and wherein the total content of silicone-derived structural units in the silicone and the silicone-containing copolymer is 1.0 to 4.0 parts by mass relative to 100 parts by mass of the recycled polyolefin resin.

[0015] According to the present invention, it is possible to provide resin parts for writing instruments having certain physical properties by using recycled polyolefin resin as a raw material.

[0016] Unlike fillers and bulking agents that impart functional properties to resin parts, the sliding property-imparting additives containing silicone-derived structural units, such as silicone or silicone-containing copolymers, impart sliding property (reducing the coefficient of friction) through the silicone portions exposed on the surface of the resin part, so sliding property is determined by the sliding property-imparting additive on the surface. Therefore, even when adding a sliding property-imparting additive to recycled polypropylene resin, which often has inconsistent physical properties, the resulting sliding property does not depend largely on the type of recycled polyolefin resin, and variation in sliding property can be reduced. This makes it suitable for use in writing instrument resin parts, especially in components that require sliding property.

[0017] Fig. 1 is a schematic diagram showing one embodiment of a writing instrument equipped with a resin part for a writing instrument of the present invention, but is not limited to this. Fig. 1(A) is a schematic diagram of the appearance of the writing instrument, and Fig. 1(B) is a schematic diagram of a cross section of Fig. 1(A).

[0018] The writing instrument 10 includes resin parts such as a knock bar 11, a clip inner cylinder 12, a shaft 13, a mouth 14, and a rotor 15. For example, the knock bar 11, which is a resin part for a writing instrument, contains a recycled polyolefin resin composition, and the recycled polyolefin resin composition may have an average dynamic friction coefficient of 0.10 to 0.40. The resin part for a writing instrument of the present invention is not particularly limited, and can be used as a resin part of the writing instrument 10. For example, the knock bar 11, the clip inner cylinder 12, the shaft 13, the mouth 14, the rotor 15, etc. are preferred. Among these, the knock bar 11, the clip inner cylinder 12, the rotor 15, or a combination thereof is preferred.

[0019] <Configuration of Recycled Polyolefin Resin Composition> In the resin part for a writing instrument of the present invention, the recycled polyolefin resin composition contains a recycled polyolefin resin and a sliding property-imparting additive, and may contain other additives as necessary.

[0020] In the resin parts for writing instruments of the present disclosure, the content of the recycled polyolefin resin composition may be, for example, 60 parts by mass or more, 70 parts by mass or more, 80 parts by mass or more, or 90 parts by mass or more, or 100 parts by mass or less, 99 parts by mass or less, 95 parts by mass or less, or 90 parts by mass or less, based on 100 parts by mass of the entire resin part for writing instruments.

[0021] <Recycled Polyolefin Resin> The recycled polyolefin resin is not particularly limited, but may contain a polypropylene resin and / or a polyethylene resin.

[0022] In the present invention, the recycled polyolefin resin is not particularly limited, but from the viewpoint of realizing sustainable development, it is preferable to use a polyolefin resin recovered from waste.

[0023] The polyolefin resin recovered from waste is preferably derived from, for example, post-consumer or pre-consumer materials. Post-consumer materials are defined in JIS Q14021:2000 as materials discarded from households or from commercial, industrial, and other end-user facilities that produce products that can no longer be used for their intended purposes. Pre-consumer materials are defined in JIS Q14021:2000 as materials removed from the waste stream during manufacturing processes.

[0024] (Polypropylene Resin) The polypropylene resin is not particularly limited, but examples thereof include homopolypropylene, random polypropylene, block polypropylene, etc. The polypropylene resin is not particularly limited, but one type may be used alone, or two or more types may be used in combination. When two or more types of polypropylene resins are used in combination, the content of the polypropylene resin is the sum of the respective contents.

[0025] As the homopolypropylene, for example, a polymer of a propylene monomer can be used.

[0026] Examples of random polypropylene include a random copolymer of propylene and ethylene, and a random copolymer of propylene and an α-olefin having 4 to 20 carbon atoms.

[0027] Examples of the α-olefins include 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. Among these, α-olefins having 4 to 8 carbon atoms are preferred, and specifically, 1-butene, 3-methyl-1-butene, 1-hexene, and 4-methyl-1-pentene are preferred. One type of α-olefin may be used alone, or two or more types may be used in combination.

[0028] The block polypropylene may be, for example, a polypropylene in which polyethylene is dispersed in homopolypropylene to form a sea-island morphology, but is not limited to this. The block polypropylene may also be, but is not particularly limited to, a mixture of a propylene homopolymer and a propylene-ethylene copolymer.

[0029] (Polyethylene Resin) Examples of polyethylene resins include, but are not limited to, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene. The polyethylene resin may also include, but is not limited to, both an ethylene homopolymer and a copolymer of ethylene and another monomer copolymerizable with the ethylene (e.g., a binary or tertiary copolymer). The bonding form of the copolymer is also not limited to, but may be random or block. The polyethylene resin may also be, but is not limited to, one type alone or two or more types in combination. When two or more types of polyethylene resins are used in combination, the content of the polyethylene resins is the sum of the respective contents.

[0030] Other monomers copolymerizable with ethylene include, but are not limited to, α-olefin compounds, vinyl compounds, non-conjugated polyene compounds, etc. One type of other monomer may be used alone, or two or more types may be used in combination. Examples of the α-olefin compounds include α-olefin compounds having 3 to 20 carbon atoms, such as propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, and 1-tetradecene. Examples of the vinyl compounds include vinylcyclohexene, styrene, and derivatives thereof. Examples of the non-conjugated polyene compounds include 1,5-hexadiene and 1,7-octadiene.

[0031] (Composition of recycled polyolefin resin) The total content of polypropylene resin and polyethylene resin in the recycled polyolefin resin may be, for example, 60 parts by mass or more, 70 parts by mass or more, 80 parts by mass or more, or 90 parts by mass or more, or 100 parts by mass or less, 99 parts by mass or less, 95 parts by mass or less, or 90 parts by mass or less, based on 100 parts by mass of the entire recycled polyolefin resin.

[0032] The content of polypropylene resin is not particularly limited, but may be 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, 80 parts by mass or more, or 90 parts by mass or more, or 100 parts by mass or less, 90 parts by mass or less, or 80 parts by mass or less, based on 100 parts by mass of the total recycled polyolefin resin.

[0033] The content of polyethylene resin is not particularly limited, but may be 1 part by mass or more, 5 parts by mass or more, or 10 parts by mass or more, or 50 parts by mass or less, 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, or 10 parts by mass or less, based on 100 parts by mass of the total recycled polyolefin resin.

[0034] Recycled polyolefin resins, particularly recycled polyolefin resins recovered from waste, may contain other resins and impurities in addition to the polypropylene resin and polyethylene resin as the main components. The total content of the other resins and impurities other than the main components may be 0 parts by mass or more, 1 part by mass or more, or 5 parts by mass or more, or 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, or 10 parts by mass or less, based on 100 parts by mass of the entire recycled polyolefin resin. The other resins and impurities other than the main components are not particularly limited, but it is preferable that they are not included.

[0035] Resins other than the main component that may be contained in the recycled polyolefin resin are not particularly limited, but examples include general-purpose resins other than polypropylene resin and polyethylene resin, engineering plastics, and super engineering plastics.

[0036] <Slidability-Imparting Additive> In the resin part for a writing instrument of the present invention, the sliding property-imparting additive contains silicone and / or a silicone-containing copolymer.

[0037] (Silicone) Silicone is not particularly limited, but can be exemplified by polysiloxane, etc., more specifically, silicone oil, silicone gum (or silicone rubber) etc. Here, polysiloxane is a polymer compound containing siloxane bond, and among silicones, oily silicone is called silicone oil, and rubbery silicone is called silicone gum (silicone rubber). Silicone is not particularly limited, but can be used alone or in combination of two or more kinds. When two or more kinds of silicone are used in combination, the content of silicone is the sum of the respective contents.

[0038] Examples of polysiloxanes include, but are not limited to, dimethylpolysiloxane, diphenylpolysiloxane, methylphenylpolysiloxane, and modified products thereof. Here, examples of modified products include, but are not limited to, vinyl-modified silicones in which some of the methyl and / or phenyl groups of the polysiloxane are substituted with vinyl groups, hydrogenpolysiloxanes in which they are substituted with hydrogen atoms, alkyl-modified silicones in which they are substituted with alkyl groups, fluorine-modified silicones in which they are substituted with fluorine atoms or fluorinated alkyl groups, polyether-modified silicones in which they are substituted with polyether groups, amino-modified silicones in which they are substituted with groups having amino groups, carbinol-modified silicones in which they are substituted with hydroxyalkyl groups, epoxy-modified silicones in which they are substituted with groups having oxirane rings, and carboxy-modified silicones in which they are substituted with groups having carboxyl groups.

[0039] As the silicone, for example, pellets in which silicone is masterbatched with another resin can be used. Specific examples of masterbatches containing silicone include, but are not limited to, silicone master pellets X-22-2101 and X-22-2147 manufactured by Shin-Etsu Chemical Co., Ltd., and EverGlide (trademark) manufactured by West One Corporation.

[0040] (Silicone-containing copolymer) The silicone-containing copolymer is not particularly limited, but may be a copolymer of the above silicone and another polymerizable monomer. Examples of the other polymerizable monomer include, but are not limited to, (meth)acrylic acid esters, (meth)acrylic acid esters having other functional groups such as epoxy groups or hydroxyl groups, and olefins. Here, "(meth)acrylic acid esters" refers to either or both of "acrylic acid esters" and "methacrylic acid esters."

[0041] The silicone-containing copolymer is not particularly limited, but examples thereof include silicone / acrylic copolymer, silicone / olefin copolymer, etc. Specific examples of silicone / acrylic copolymers include Chaline R-170S, R-175S, and R-200 manufactured by Nissin Chemical Industry Co., Ltd., and Cymac (trademark) US-450 and US-480 manufactured by Toagosei Co., Ltd. Furthermore, examples of silicone / olefin copolymers include Exfora (trademark) PP2000 manufactured by Mitsui Fine Chemicals, and BY27-001 and BY27-201 manufactured by DuPont Toray Specialty Materials.

[0042] The silicone-containing copolymer is not particularly limited, and one type may be used alone, or two or more types may be used in combination. When two or more types of silicone-containing copolymers are used in combination, the content of the silicone-containing copolymer is the sum of the respective contents.

[0043] (Amount of Sliding Property-Providing Additive Added) In the resin part for a writing instrument of the present disclosure, the total content of silicone and silicone-derived structural units in the silicone-containing copolymer is 1.0 to 4.0 parts by mass relative to 100 parts by mass of the recycled polyolefin resin, and may be 1.5 parts by mass or more, 2.0 parts by mass or more, or 2.5 parts by mass or more, or 4.0 parts by mass or less, 3.8 parts by mass or less, or 3.6 parts by mass or less.

[0044] <Other Additives> The recycled polyolefin resin composition may contain known additives such as antioxidants, slip agents, neutralizing agents, light stabilizers, antistatic agents, and pigments, as needed.

[0045] (Antioxidant) The antioxidant is not particularly limited, but examples thereof include phenol-based antioxidants, phenol-phosphorus-based antioxidants, and phosphorus-based antioxidants.

[0046] Examples of phenolic antioxidants include, but are not limited to, 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, and tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane.

[0047] Examples of phenol-phosphorus antioxidants include, but are not limited to, 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepine.

[0048] Examples of phosphorus-based antioxidants include, but are not limited to, tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylene-di-phosphonite, tris(2,4-di-t-butylphenyl)phosphite, and cyclic neopentanetetraylbis(2,4-t-butylphenylphosphite).

[0049] (Slip Agent, Neutralizing Agent) The slip agent or neutralizing agent is not particularly limited, but examples thereof include aliphatic hydrocarbons, higher fatty acids, higher fatty acid metal salts, fatty acid esters of alcohols, waxes, higher fatty acid amides, silicone oils, rosin, etc. Examples of the slip agent or neutralizing agent include, but are not limited to, stearates, specifically calcium stearate, magnesium stearate, zinc stearate, etc.

[0050] (Light Stabilizer) The light stabilizer is not particularly limited, but examples thereof include benzotriazole-based light stabilizers and hindered amine-based light stabilizers.

[0051] Examples of the benzotriazole-based light stabilizer include, but are not limited to, 2-(5-methyl-2-hydroxyphenyl)benzotriazole and 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole.

[0052] Examples of the hindered amine light resistance stabilizer include, but are not limited to, bis(2,2,6,6-tetramethyl-4-piperidine) sebacate and poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}].

[0053] (Antistatic Agent) The antistatic agent is not particularly limited, but examples thereof include aluminosilicates, kaolin, clay, natural silica, synthetic silica, silicates, talc, diatomaceous earth, and glycerin fatty acid esters.

[0054] (Pigment) The pigment is not particularly limited, but examples thereof include inorganic pigments, organic pigments, etc. Examples of inorganic pigments include, but are not limited to, titanium oxide, carbon black, iron oxide pigments, etc. Examples of organic pigments include, but are not limited to, azo pigments, phthalocyanine pigments, condensed polycyclic pigments, etc.

[0055] The recycled polyolefin resin composition can be produced by applying known methods (e.g., dry blending, masterbatch, extrusion kneading, melt kneading, etc.). For example, the recycled polyolefin resin composition can be easily produced by melt kneading raw materials containing the above-mentioned various components.

[0056] <Physical properties of recycled polyolefin resin composition> The recycled polyolefin resin composition may have a dynamic friction coefficient of 0.10 to 0.40. The dynamic friction coefficient may be 0.15 or more, 0.17 or more, 0.19 or more, or 0.21 or more, or 0.40 or less, 0.38 or less, or 0.36 or less.

[0057] The dynamic friction coefficient of the recycled polyolefin resin composition can be determined in accordance with JIS K7125: 1999. Specifically, two test samples (80 mm x 200 mm x 1 mm thick: JIS K7154-2: 2002, small square plate type D1) are prepared, stacked, and placed on an automatic load testing machine (manufactured by Nippon Keisoku Systems, model number: MAX-1KN-H-1). The test samples are then rubbed against each other under conditions of a load of 200 g ± 2 g (1.96 N ± 0.02 N) and a friction speed of 100 mm / min, and the dynamic friction coefficient is measured.

[0058] <Molding of Resin Parts for Writing Instruments> Resin parts for writing instruments can be molded from recycled polyolefin resin compositions by applying known methods. For example, resin parts for writing instruments can be easily molded by injection molding the recycled polyolefin resin composition.

[0059] <Writing Instrument> The writing instrument of the present invention includes the above-described resin part for a writing instrument.

[0060] The writing implement of the present invention can be made from recycled polyolefin resin.

[0061] 1, the writing instrument 10 may include the above-described resin parts for a writing instrument in the knock bar portion 11, the clip inner cylinder portion 12, the shaft portion 13, the mouth portion 14, the rotor portion 15, etc. In particular, it is preferable that at least one of the knock bar portion 11, the clip inner cylinder portion 12, and the rotor portion 15 include the resin parts.

[0062] The writing implement of the present invention is not particularly limited, but may be a ballpoint pen or a marking pen.

[0063] The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples.

[0064] The recycled polyolefin resins and additives for imparting sliding properties used in the examples and comparative examples are as follows.

[0065] (Recycled polyolefin resin) 1-1. Recycled colored PP: Polypropylene resin as a post-consumer material, which is colored. 1-2. Recycled PP: Polypropylene resin as a post-consumer material.

[0066] (Slidability-imparting additives) 2-1. R-170S: Chaline R-170S (manufactured by Nissin Chemical Industry Co., Ltd., silicone / acrylic copolymer, 70% by mass of structural units derived from silicone). 2-2. X-22-2101: Silicone master pellet X-22-2101 (manufactured by Shin-Etsu Chemical Co., Ltd., polypropylene resin silicone master pellet, 50% by mass of structural units derived from silicone). 2-3. PP2000: Exfora PP2000 (manufactured by Mitsui Chemicals Fine Chemicals, silicone / ethylene copolymer, 30% by mass of structural units derived from silicone). 2-4. P-10: Arflow P-10 (manufactured by NOF Corp., fatty acid amide). 2-5. L5000: Lubmar L5000 (manufactured by Mitsui Chemicals, ultra-high molecular weight polyethylene).

[0067] Example 1 Preparation of Recycled Polyolefin Resin Composition Recycled colored PP as the recycled polyolefin resin and R-170S as the sliding property-imparting additive were extrusion molded (melt temperature 200°C) to prepare a recycled polyolefin resin composition. The content of silicone-derived structural units in R-170S was 1.0 part by mass per 100 parts by mass of the recycled colored PP.

[0068] Measurement of the dynamic friction coefficient of the recycled polyolefin resin composition Two test samples (80 mm x 200 mm x 1 mm thick: JIS K7154-2:2002, small square plate type D1) were prepared using the resulting recycled polyolefin resin composition. The two test samples were stacked and placed on an automatic load testing machine (manufactured by Nippon Keisoku Systems, model number: MAX-1KN-H-1). The test samples were then rubbed against each other under conditions of a load of 200 g ± 2 g (1.96 N ± 0.02 N) and a friction speed of 100 mm / min to measure the dynamic friction coefficient. The dynamic friction coefficient was measured five times, and Table 1 shows the average of the five measurements.

[0069] <Preparation of Resin Parts for Writing Instruments and Evaluation of Knock Operation> A recycled polyolefin resin composition was injection molded (melt temperature 200°C, mold temperature 30°C, filling speed 50 mm / s) to prepare resin parts for writing instruments, such as the knock bar 11, clip inner tube 12, and rotor 15 of a knock-type ballpoint pen as shown in Figures 1(A) and 1(B). These were then assembled to prepare a feeding mechanism 17. The feeding mechanism 17 was subjected to 3,000 retraction and extension operations, and its operation was confirmed and knock operation was evaluated. Here, the knock load (pressure load required for the retraction and extension of the writing refill) during the retraction and extension operation was 3 N. The knock operation test was conducted five times and evaluated according to the following criteria. A: Smooth sliding properties were maintained in all samples. B: Sliding resistance was increased, and some samples were difficult to extend.

[0070] Examples 2 to 4 and Comparative Examples 1 to 5 Preparation of Recycled Polyolefin Resin Compositions and Measurement of Dynamic Friction Coefficient of Recycled Polyolefin Resin Composition Portion Recycled polyolefin resin compositions were prepared in the same manner as in Example 1, except that the materials shown in Table 1 were used. The dynamic friction coefficient of each recycled polyolefin resin composition was measured in the same manner as in Example 1. The dynamic friction coefficient of each recycled polyolefin resin composition was as shown in Table 1.

[0071] <Preparation of Resin Parts for Writing Instruments and Evaluation of Knock Operation> Resin parts for writing instruments were prepared in the same manner as in Example 1, except that the recycled polyolefin resin compositions prepared in Examples 2 to 4 and Comparative Examples 1 to 5 were used. The knock operation of each resin part for a writing instrument was evaluated in the same manner as in Example 1. The knock operation of each resin part for a writing instrument was as shown in Table 1.

[0072]

[0073] By adding a predetermined amount of silicone (Example 3) or a silicone-containing copolymer (Examples 1, 2, and 4) as a sliding property-imparting additive to recycled polyolefin resin, it was confirmed that the resin parts for writing instruments and writing instruments have certain physical properties, specifically, a specific dynamic friction coefficient, and therefore good knock operability. On the other hand, polyolefin resin compositions that do not contain a sliding property-imparting additive (Comparative Examples 1 and 2) or that contain a sliding property-imparting additive other than silicone or a silicone-containing copolymer (Comparative Examples 4 and 5) did not have good knock operability. Furthermore, when the total content of silicone-derived structural units in the sliding property-imparting additive was lower than the predetermined range, and therefore the dynamic friction coefficient of the polyolefin resin composition was not within the predetermined range (Comparative Example 3), good knock operability was not obtained.

[0074] Although preferred embodiments of the resin part for a writing instrument and the writing instrument of the present invention have been described, modifications can be made without departing from the scope of the claims.

[0075] 10 Writing implement 11 Knock bar portion 12 Clip inner cylinder portion 13 Shaft portion 14 Mouth portion 15 Rotor portion 16 Writing lead 17 Feeding mechanism portion

Claims

1. A resin part for a writing instrument, comprising a recycled polyolefin resin composition, wherein the recycled polyolefin resin composition comprises recycled polyolefin resin and a sliding property-imparting additive, wherein the sliding property-imparting additive comprises silicone and / or a silicone-containing copolymer, and wherein the total content of silicone-derived structural units in the silicone and the silicone-containing copolymer is 1.0 to 4.0 parts by mass per 100 parts by mass of the recycled polyolefin resin.

2. The resin part for a writing instrument according to claim 1, wherein the recycled polyolefin resin composition has a dynamic friction coefficient of 0.10 to 0.

40.

3. A resin part for a writing instrument as described in claim 1 or 2, wherein the content of the recycled polyolefin resin composition is 60 parts by mass or more, based on 100 parts by mass of the entire resin part for the writing instrument.

4. A writing instrument comprising the resin part for a writing instrument according to any one of claims 1 to 3.

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