JP2023122346A - Resin composition, friction body, and writing utensil - Google Patents

Abstract

To provide a resin composition and a friction body that utilize flexibility and stress relaxation property that are features of a 4-methyl-1-pentene-α-olefin copolymer, where the resin composition reduces a coefficient of static friction and suppresses peeling and damage on a paper surface, when handwriting and drawing are erased by manual friction, on the other hand, promotes heat discoloration by improving a coefficient of dynamic friction, and can obtain excellent erasability to heat-discoloring ink, and a friction body contains the resin composition.SOLUTION: There are provided a resin composition which contains 10-50 pts.mass of a 4-methyl-1-pentene-α-olefin copolymer (A) satisfying a specific requirement, 10-50 pts.mass of a polyolefin-based thermoplastic elastomer (B), 5-30 pts.mass of an ethylene polymer (C), and 0.1-20 pts.mass of a petroleum resin (D) (provided that the total of (A), (B), (C) and (D) is 100 pts.mass); and a friction body containing the resin composition.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a resin composition, a friction body and a writing implement containing a 4-methyl-1-pentene/α-olefin copolymer. More particularly, the present invention relates to a resin composition, a friction body, and a writing instrument capable of erasing handwriting by thermally discoloring graphite, thermochromic ink, or the like by manual friction.

2. Description of the Related Art As a means for discoloring heat-discolored portions formed on paper by writing or drawing, there is used a friction body that uses an elastic material such as polyvinyl chloride or high-density polyethylene to discolor by frictional heat through manual friction.

Furthermore, in recent years, various writing instruments have been proposed that can discolor or decolor handwriting formed using thermochromic ink by heating, and are commercially available as ballpoint pens and marking pens. These "handwritings" refer to lines and drawings written or drawn on a writing surface or a drawing surface. In the writing instrument filled with the thermochromic ink, a friction body made of an elastic material is used in order to quickly and easily apply frictional heat to handwriting or drawing formed on the paper surface. These friction bodies are put into practical use in the form of separate bodies in addition to being attached to the rear end portion of the barrel of the writing instrument, the mouthpiece, the tip of the cap, or the like.

Patent Document 1 discloses a writing instrument set containing a reversible thermochromic ink and a writing instrument set using a resin material having a specific surface hardness or more as a friction body. Integration by molding has been proposed.

Patent Document 2 discloses a knock-type writing instrument filled with erasable ink, and proposes to use a polystyrene-based thermoplastic elastomer or the like as a friction body.

Patent Literature 3 proposes a viscoelastic body whose main component is a polystyrene-based thermoplastic elastomer with a specific surface hardness range, as a friction body for discoloring handwriting with thermochromic ink by frictional heat.

Japanese Patent Application Laid-Open No. 2007-223302 JP 2009-143207 A WO2018/116767

The writing instrument main body and the friction body containing the reversible thermochromic ink described in Patent Document 1 are formed with the support base material by two-color molding when the friction body is applied as a friction tool formed on the support base material. It is fused and fixed. However, in this writing instrument, the combination of the support base material and the friction body is limited, so the degree of freedom in selecting each material may be low. In addition, a complicated mold is required for molding the friction body, and there has been a tendency for the thickness of the friction body to become large in order to obtain good moldability. Furthermore, since the friction body is an elastic body, it is necessary to apply a considerable amount of force to erasing the handwriting or drawing, which promotes thermal discoloration.

The friction body described in Patent Document 2 mainly uses an elastic body such as polystyrene-based thermoplastic elastomer. However, when an erasable ink having a metallic tone with enhanced decorativeness is used, erasing of handwriting and drawings is not sufficient.

In Patent Document 3, a metallic luster pigment is contained in a thermochromic ink for the purpose of imparting metallic decorativeness. However, when the handwriting or drawing is erased by manual rubbing, there is a concern that the component derived from the metallic luster pigment diffuses on the paper surface and sufficient erasability cannot be obtained. Furthermore, when writing or drawing is performed on a paper material such as colored paper with low surface strength, there is a problem that if the handwriting or drawing is to be erased by manual friction, peeling or damage will occur on the paper surface.

An object of the present invention is to provide a resin composition that takes advantage of the flexibility and stress relaxation properties that are characteristics of a 4-methyl-1-pentene/α-olefin copolymer, and a friction body containing the resin composition, When erasing or drawing by manual friction, the static friction coefficient is reduced to suppress peeling and breakage on the paper surface, while the dynamic friction coefficient is improved to promote heat discoloration and prevent heat discoloration ink. An object of the present invention is to provide a resin composition capable of obtaining excellent erasability and a friction body containing the resin composition.

As a result of intensive studies to solve the above problems, a resin composition containing a 4-methyl-1-pentene/α-olefin copolymer, a polyolefin thermoplastic elastomer, an ethylene polymer, and a petroleum resin in a specific blending ratio. The inventors have found that the above-mentioned problems can be solved by a friction body containing the product and the resin composition, and have completed the present invention.

That is, the present invention includes the following [1] to [6].

[1] 10 to 50 parts by mass of a 4-methyl-1-pentene/α-olefin copolymer (A) satisfying the following requirements (Aa) to (Ae),
Polyolefin thermoplastic elastomer (B) 10 to 50 parts by mass,
Ethylene polymer (C) 5 to 30 parts by mass,
and petroleum resin (D) 0.1 to 20 parts by mass [where the total of (A), (B), (C) and (D) is 100 parts by mass. ] A resin composition containing;
(Aa) 60 to 78 mol% of structural units (i) derived from 4-methyl-1-pentene and 40 to 22 mol% of structural units (ii) derived from an α-olefin having 2 to 4 carbon atoms [However, the total of the structural unit (i) and the structural unit (ii) shall be 100 mol %. ];
(Ab) the intrinsic viscosity [η] measured in decalin at 135°C is in the range of 0.5 to 4.0 dl/g;
(Ac) The molecular weight distribution (Mw/Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gemipermeation chromatography (GPC), is 1.0 to 4.0. in the range of 0;
(A−d) having a density in the range of 825-860 kg/m ³ ;
(Ae) Melting point (Tm) measured by differential scanning calorimeter (DSC) is not observed.

[2] The resin composition according to [1], wherein the 4-methyl-1-pentene/α-olefin copolymer (A) satisfies the following requirements (Af) to (Ag);
(Af) In the temperature range of -40 to 150°C, dynamics measured under the conditions of torsion mode, frequency of 10 rad/s (1.6 Hz), heating rate of 2°C/min, and strain amount of 0.1%. the maximum value of the viscoelastic loss tangent tan δ is in the range of 1.0 to 5.0;
(Ag) In the temperature range of -40 to 150 ° C., the dynamics measured under the conditions of torsion mode, frequency of 10 rad/s (1.6 Hz), heating rate of 2 ° C./min, and strain amount of 0.1%. The temperature at which the value of the loss tangent tan δ of the physical viscoelasticity is maximized is in the range of 10 to 38°C.

[3] The resin composition according to [1] or [2], which satisfies the following requirements (x) and (y);
(x) Shore A hardness measured in accordance with ASTM D2240 15 seconds after the start of indenter contact is 60 to 85;
(y) In Shore A hardness measured in accordance with ASTM D2240, the difference between the value of Shore A hardness immediately after contact with the indenter and the value of Shore A hardness 15 seconds after contact with the indenter shown by the following formula ( ΔHS) is 5-18.
ΔHS = (Shore A hardness value immediately after contact with the incisor) - (Shore A hardness value 15 seconds after contact with the incisor)

[4] A friction body containing the resin composition according to any one of [1] to [3].

[5] The friction body according to [4], which is an injection molded body.

[6] A writing instrument having the friction body according to [4] or [5].

According to the present invention, there is provided a resin composition that takes advantage of the flexibility and stress relaxation properties that are characteristics of the 4-methyl-1-pentene/α-olefin copolymer, and a friction body containing the resin composition, When erasing drawings by manual friction, the static friction coefficient is reduced to suppress peeling and damage on the paper surface, while the dynamic friction coefficient is improved to promote thermal discoloration, making it excellent for thermochromic inks. It is possible to provide a resin composition that provides excellent erasability and a friction body containing the resin composition.

Further, the friction body of the present invention can be formed of a single member, similar to friction bodies provided in conventional writing instrument bodies. Therefore, there is no need for complicated molds for each structure, and there are no restrictions on materials, so that a wide range of designs for writing instruments can be selected.

Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all, and can be carried out with appropriate modifications within the scope of the purpose of the present invention. be able to. In this specification, the term "polymer" includes homopolymers and copolymers unless otherwise specified.

<Resin composition>
One embodiment of the present invention is a 4-methyl-1-pentene/α-olefin copolymer (A), a polyolefin thermoplastic elastomer (B), an ethylene polymer (C), and a petroleum resin (D), which will be described later. It is a resin composition containing

[4-methyl-1-pentene/α-olefin copolymer (A)]
4-Methyl-1-pentene/α-olefin copolymer (A) (hereinafter sometimes abbreviated as “copolymer (A)”) is one of the components constituting the resin composition of the present invention. ] is a copolymer of 4-methyl-1-pentene and an α-olefin that satisfies the following requirements (Aa) to (Ae).

<Requirement (A-a)>
Consisting of 60 to 78 mol% of the structural unit (i) derived from 4-methyl-1-pentene and 40 to 22 mol% of the structural unit (ii) derived from an α-olefin having 2 to 4 carbon atoms [provided that , the total of structural unit (i) and structural unit (ii) is 100 mol %. ].

When the content of the structural unit (i) in the copolymer (A) is 60 mol % or more, stress relaxation properties can be imparted to the resin composition. When the content of the structural unit (ii) in the copolymer (A) is 22 mol % or more, flexibility is exhibited. Furthermore, in the friction body, which is another embodiment of the present invention, containing the above resin composition, when handwriting or drawing is erased by manual friction, it is excellent in following the shape on the paper surface (surface roughness). .

The value of the content (mol %) of the structural unit in the copolymer (A) is calculated by a measurement method using carbon-13 nuclear magnetic resonance ( ¹³ C-NMR). In addition, the specific measuring method is as described in Examples below.

The content of the structural unit (i) in the copolymer (A) is preferably in the range of 62-77 mol %, more preferably 64-76 mol %, still more preferably 68-75 mol %.

The content of the structural unit (ii) in the copolymer (A) is preferably in the range of 23-38 mol %, more preferably 24-36 mol %, still more preferably 25-32 mol %.

Examples of the α-olefin having 2 to 4 carbon atoms forming the structural unit (ii) in the copolymer (A) include ethylene, propylene and 1-butene. These can be used singly or in combination of two or more as long as the effects of the present invention are not impaired. Among these, propylene is particularly preferable, and is advantageous in exhibiting characteristics of both flexibility and stress relaxation.

<Requirements (A-b)>
The intrinsic viscosity [η] of the copolymer (A) measured in decalin at 135° C. is 0.5 to 4.0 dl/g, preferably 0.6 to 3.5 dl/g, more preferably 0.8 to It is in the range of 3.0 dl/g.

When the intrinsic viscosity [η] of the copolymer (A) is within the above range, the resin composition of the present invention is less sticky due to less low-molecular-weight components, which facilitates molding, which is preferable. A specific method for measuring the intrinsic viscosity [η] is as described in Examples below.

Furthermore, the copolymer (A) has a melt flow rate (MFR) value measured at a temperature of 230 ° C. and 21.18 N in accordance with ASTM D1238, preferably 0.1 to 100 g / 10 minutes, more The range is preferably 0.5 to 80 g/10 minutes, more preferably 1 to 50 g/10 minutes. When the copolymer (A) is within the above range, mixing dispersibility with the polyolefin thermoplastic elastomer (B), the ethylene polymer (C), and the petroleum resin (D), and the resin composition of the present invention It is preferable because the molding workability of is easy.

<Requirements (A-c)>
The molecular weight distribution (Mw/Mn), which is the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gemipermeation chromatography (GPC) in the copolymer (A), is 1.0 to It is in the range of 4.0. The molecular weight distribution (Mw/Mn) is preferably 1.2 to 3.5, more preferably 1.3 to 3.0, still more preferably 1.5 to 2.8.

When the molecular weight distribution (Mw/Mn) is 4.0 or less, the effect of the low molecular weight and low stereoregular polymer derived from the composition distribution is small, the stickiness of the resin composition of the present invention is reduced, and molding is easy. It is preferable because it becomes easier.

Further, the weight average molecular weight (Mw) measured by GPC in the copolymer (A) is preferably 500 to 10,000,000, more preferably 1,000 to 5,000,000 in terms of polystyrene, and further It is preferably in the range of 1,000 to 2,500,000. The details of the GPC measurement conditions and the like are as described in Examples below.

<Requirements (A-d)>
The density of copolymer (A) is in the range of 825-860 kg/m ³ , preferably 830-850 kg/m ³ . When the density is within the above range, the polyolefin-based thermoplastic elastomer (B), the ethylene polymer (C), and the petroleum resin (D) contained in the resin composition are mixed and dispersed uniformly. This is preferable because a friction element containing the resin composition can be obtained. Advantageously, the resulting friction body has flexibility. The details of the density measurement conditions and the like are as described in Examples below.

<Requirements (Ae)>
Copolymer (A) does not have a melting point (Tm) measured with a differential scanning calorimeter (DSC). Flexibility is expressed by satisfying such requirements. Furthermore, the friction body containing the resin composition of the present invention is excellent in shape follow-up on the paper surface (surface roughness) when handwriting or drawings are erased by manual friction.

The value of the melting point (Tm) is a value that varies depending on the stereoregularity of the copolymer (A) and the α-olefin of the monomer corresponding to the structural unit (ii) polymerized together with the structural unit (i). . The melting point (Tm) of the copolymer (A) can be adjusted by controlling the desired composition using the olefin polymerization catalyst described below. The details of the melting point (Tm) measurement conditions and the like are as described in Examples below.

The copolymer (A) preferably satisfies the following requirements (Af) to (Ag) in addition to the above requirements (Aa) to (Ae).

<Requirements (Af)>
Measured in the copolymer (A) in a temperature range of -40 to 150°C under the conditions of torsion mode, frequency of 10 rad/s (1.6 Hz), temperature increase rate of 2°C/min, and strain amount of 0.1%. The maximum value of the dynamic viscoelasticity loss tangent tan δ (hereinafter sometimes referred to as “tan δ peak value”) is preferably 1.0 to 5.0, more preferably 1.5 to 4.5, and further It is preferably in the range of 2.0 to 4.0.

The stress relaxation property of the copolymer (A) can be measured, for example, by the loss tangent tan δ indicated by the ratio (G″/G′) of the storage elastic modulus G′ and the loss elastic modulus G″ measured by dynamic viscoelasticity. , can be evaluated. The storage elastic modulus G' is an elastic component that retains the stress by storing the energy inside when stress is applied. The loss elastic modulus G″ is a viscous component that converts the energy into heat and releases it (diffuses to the outside) when stress is applied. Therefore, materials with a high loss tangent tan δ under a specific temperature environment The more it is, the easier it is to absorb the impact, and the higher the stress relaxation property will be expressed.

The tan δ peak value of the copolymer (A) alone used in the resin composition of the present invention should be 1.0 or more. Stress such as deformation can be easily relaxed, and the friction body is preferable because it is excellent in shape follow-up to the paper surface (surface roughness) when handwriting or drawings are erased by manual friction.

<Requirements (A-g)>
Measured in the copolymer (A) in a temperature range of -40 to 150°C under the conditions of torsion mode, frequency of 10 rad/s (1.6 Hz), temperature increase rate of 2°C/min, and strain amount of 0.1%. The temperature at which the value of the loss tangent tan δ of dynamic viscoelasticity is maximized (hereinafter sometimes referred to as “tan δ peak temperature”) is preferably 10 to 38 ° C., more preferably 15 to 37 ° C., and further It is preferably in the range of 20-36°C.

Regarding the resin composition of the present invention, the tan δ peak temperature of the copolymer (A) is in the range of 22 to 35°C. It becomes easy to relax the stress of, and it is preferable because it is excellent in flexibility. Furthermore, since the tan δ peak temperature is in the range of 22 to 35° C., the viscosity of the friction body containing the resin composition of the present invention is increased at room temperature, which is particularly advantageous for the erasability of thermochromic ink. be. A specific method for measuring the loss tangent tan δ of dynamic viscoelasticity is as described in Examples below.

The tan δ peak value and tan δ peak temperature can be adjusted by the composition ratio of structural unit (i)/structural unit (ii) in the copolymer (A).

<Method for producing copolymer (A)>
The method for producing the copolymer (A) is not particularly limited, but for example, 4-methyl-1-pentene and the above α-olefin having 2 to 4 carbon atoms are mixed with a magnesium-supported titanium catalyst, a metallocene catalyst, or the like. It can be produced by polymerization in the presence of an appropriate polymerization catalyst.

Here, the polymerization catalyst that can be used includes conventionally known catalysts such as magnesium-supported titanium catalysts, International Publication Nos. 01/53369, WO 01/27124, JP-A-3-193796, Alternatively, metallocene catalysts described in JP-A-2-41303, WO 2011/055803, WO 2014/050817, etc. are preferably used. Polymerization can be carried out by appropriately selecting from a liquid phase polymerization method including solution polymerization and suspension polymerization, a gas phase polymerization method, and the like.

In the liquid phase polymerization method, an inert hydrocarbon solvent can be used as a solvent that constitutes the liquid phase. Examples of such inert hydrocarbons include aliphatic hydrocarbons including propane, butane, pentane, hexane, heptane, octane, decane, dodecane, and kerosene, cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, and the like. aromatic hydrocarbons, including benzene, toluene, and xylene; and halogenated hydrocarbons, including ethylene chloride, chlorobenzene, dichloromethane, trichloromethane, and tetrachloromethane, and mixtures thereof. included.

Further, in the liquid phase polymerization method, the monomer corresponding to the structural unit (i) derived from the 4-methyl-1-pentene (that is, 4-methyl-1-pentene), the α- Bulk polymerization can also be carried out using the monomer corresponding to the structural unit (ii) derived from the olefin (that is, the α-olefin having 2 to 4 carbon atoms) itself as a solvent.

The 4-methyl-1-pentene/α-olefin copolymer (A ) and the composition distribution of the structural unit (i) derived from 4-methyl-1-pentene and the structural unit (ii) derived from an α-olefin having 2 to 4 carbon atoms can be controlled appropriately. can.

The polymerization temperature is preferably -50 to 200°C, more preferably 0 to 100°C, even more preferably 20 to 100°C. The polymerization pressure is preferably normal pressure to 10 MPa gauge pressure, more preferably normal pressure to 5 MPa gauge pressure.

Hydrogen may be added during polymerization for the purpose of controlling the molecular weight and polymerization activity of the polymer to be produced. An appropriate amount of hydrogen to be added is about 0.001 to 100 NL per 1 kg of the total amount of 4-methyl-1-pentene and α-olefin having 2 to 4 carbon atoms.

[Polyolefin Thermoplastic Elastomer (B)]
The thermoplastic polyolefin elastomer (B) according to the present invention is a polymer that exhibits thermoplastic properties when heated to a melting point or higher and exhibits rubber elasticity at room temperature (5 to 35° C.).

The polyolefin thermoplastic elastomer (B) according to the present invention can be mixed and dispersed with the copolymer (A), the ethylene polymer (C), and the petroleum resin (D), and has desired fluidity and moldability. There are no particular limitations as long as the appearance of the body, mechanical properties, and the like can be obtained.

In addition, by including the polyolefin-based thermoplastic elastomer (B) in the resin composition of the present invention, the friction body containing the resin composition can be imparted with appropriate rigidity for erasing handwriting and drawings by manual friction.

As a first form of the polyolefin thermoplastic elastomer (B) according to the present invention, one selected from the group consisting of ethylene and propylene, butadiene, hydrogenated butadiene, isoprene, hydrogenated isoprene, isobutylene, and α- It is a copolymer with one selected from the group consisting of olefins and has a density of 900 kg/m ³ or less. The form of the copolymer may be either a block copolymer or a graft copolymer. It is an olefin having a double bond at one end, and 1-butene, 1-octene, etc. are preferably used.

For example, a block copolymer of a polyolefin block forming a highly crystalline polymer such as polypropylene as a hard part and a monomer copolymer block showing non-crystallinity as a soft part can be mentioned. Examples include polyolefin (crystalline)/ethylene/butylene/olefin block copolymers and polypropylene/polyolefin (non-crystalline)/polypropylene block copolymers.

Specific examples include DYNARON (registered trademark) manufactured by JSR Corporation, Tafmer (registered trademark) manufactured by Mitsui Chemicals, Inc. ENGAGE (registered trademark) and VERSIFY (registered trademark) manufactured by Dow Chemical Company, and Vistamaxx (registered trademark) manufactured by ExxonMobil Chemical. etc. are commercially available.

Further, the second form of the polyolefin thermoplastic elastomer (B) according to the present invention includes one selected from the group consisting of polyethylene and polypropylene, an ethylene/propylene copolymer, and an ethylene/propylene/diene copolymer. and one selected from the group consisting of ethylene-butene copolymers. Here, the ethylene/propylene copolymer, ethylene/propylene/diene copolymer, and ethylene/butene copolymer are preferably partially or completely crosslinked.

Specific examples include Milastomer (registered trademark) manufactured by Mitsui Chemicals, Esporex (registered trademark) manufactured by Sumitomo Chemical, Thermorun (registered trademark) manufactured by Mitsubishi Chemical, Zelas TPO (registered trademark), and Santoprene (registered trademark) manufactured by Celanese. ) are commercially available.

The thermoplastic polyolefin elastomer (B) according to the present invention is modified with at least one functional group selected from the group consisting of acid anhydride groups, carboxyl groups, amino groups, hydroxyl groups and epoxy groups. good too.

[Ethylene polymer (C)]
The ethylene polymer (C) according to the present invention is an ethylene homopolymer and an ethylene copolymer.

Examples of ethylene copolymers include ethylene/propylene copolymers, ethylene/1-butene copolymers, ethylene/1-pentene copolymers, ethylene/1-hexene copolymers, and ethylene/1-heptene copolymers. polymers, ethylene/α-olefin copolymers such as ethylene/1-octene copolymers, and the like.

Examples of the ethylene polymer (C) include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE).

Among these, linear low-density polyethylene (LLDPE) is preferable from the viewpoint that the density and surface hardness of the resin composition of the present invention can be easily adjusted by the content of the ethylene polymer (C).

In addition, by including the ethylene polymer (C) in the resin composition of the present invention, the friction body containing the resin composition can adjust the surface hardness suitable for erasing handwriting and drawing by manual friction, and can be heated. Exhibits excellent erasability for color-changing inks.

[Petroleum resin (D)]
The petroleum resin (D) according to the present invention means mainly 5 carbon atoms (C5) or carbon atom It is a resin component obtained by solidifying with an acidic catalyst without isolating unsaturated hydrocarbons from the fraction of number 9 (C9).

Examples of the petroleum resin (D) include aromatic petroleum resins, aliphatic petroleum resins, aliphatic/aromatic petroleum resins, dicyclopentadiene petroleum resins, and hydrogenated derivatives thereof. Among these, from the viewpoint of compatibility with the copolymer (A), the polyolefin thermoplastic elastomer (B), and the ethylene polymer (C), and the color tone and thermal stability of the resulting friction body, hydrogen It is preferred to use additive derivatives.

In addition, by including the petroleum resin (D) in the resin composition of the present invention, the friction body containing the resin composition can improve the dynamic friction coefficient when handwriting or drawing is erased by manual friction. Therefore, it exhibits excellent erasability for handwriting and drawing with thermochromic ink.

Specific examples include Rigalite (registered trademark) manufactured by Eastman Chemical Co., Ltd., Alcon (registered trademark) manufactured by Arakawa Chemical Industries, Ltd., Imarve (registered trademark) manufactured by Idemitsu Kosan Co., Ltd., and T-REZ H (registered trademark) manufactured by ENEOS. Commercially available products can be mentioned.

[Quantity ratio]
The resin composition of the present invention comprises 10 to 50 parts by mass of a copolymer (A), 10 to 50 parts by mass of a polyolefin thermoplastic elastomer (B), 5 to 30 parts by mass of an ethylene polymer (C), and a petroleum resin ( D) 0.1 to 20 parts by mass [where the total of (A), (B), (C) and (D) is 100 parts by mass. 〕including.

From the viewpoint of flexibility and stress relaxation of the friction body containing the resin composition of the present invention, the content of the copolymer (A) is preferably 12 to 48 parts by mass, more preferably 15 to 46 parts by mass, and 20 parts by mass. ~45 parts by mass is more preferred.

In addition, from the viewpoint of imparting appropriate rigidity to the friction body containing the resin composition of the present invention, the content of the polyolefin thermoplastic elastomer (B) is preferably 12 to 48 parts by mass, more preferably 15 to 46 parts by mass. Preferably, 20 to 45 parts by mass is more preferable.

Next, from the viewpoint of adjusting the surface hardness of the friction body containing the resin composition of the present invention to an appropriate level, the content of the ethylene polymer (C) is preferably 8 to 28 parts by mass, more preferably 10 to 26 parts by mass. , 12 to 24 parts by mass is more preferable.

Furthermore, from the viewpoint of adjusting the friction body containing the resin composition of the present invention to an appropriate dynamic friction coefficient, the content of the petroleum resin (D) is preferably 0.5 to 18 parts by mass, more preferably 1 to 16 parts by mass. Preferably, 2 to 15 parts by mass is more preferable.

The resin composition of the present invention preferably satisfies the following requirements (x) and (y).

[Requirement (x)]
The Shore A hardness measured in accordance with ASTM D2240 15 seconds after the start of contact with the indenter is 60 to 85, preferably 62 to 82, more preferably 64 to 80, and still more preferably 65 to 78. A specific method for measuring the surface hardness is as described in Examples below.

Those having a Shore A hardness value within the above range immediately after the start of contact with an indenter are particularly effective in generating frictional heat, and are suitable because handwriting and drawings can be easily thermally discolored.

[Requirement (y)]
In Shore A hardness measured in accordance with ASTM D2240, the difference (ΔHS) between the value of Shore A hardness immediately after contact with the indenter and the value of Shore A hardness 15 seconds after contact with the indenter is 5 to 18. Yes, preferably 6 to 18, more preferably 8 to 18, still more preferably 10 to 18.

ΔHS is a value obtained according to the following formula.
ΔHS = (Shore A hardness value immediately after contact with the incisor) - (Shore A hardness value 15 seconds after contact with the incisor)

When ΔHS is equal to or less than the above upper limit, the frictional body obtained from the resin composition can more effectively generate frictional heat when rubbing handwriting or drawing on paper. Further, when the thickness is equal to or higher than the above lower limit, particles (pigments, etc.) contained in handwriting or drawing can be more easily adsorbed and peeled off. ΔHS can be arbitrarily changed depending on the comonomer species and comonomer composition of the copolymer (A). Also, it can be adjusted by mixing a plurality of types.

[Other ingredients]
The resin composition of the present invention comprises a copolymer (A), a polyolefin thermoplastic elastomer (B), an ethylene polymer (C), and a petroleum resin (D), as long as the effects of the present invention are not impaired. ) (hereinafter also referred to as “other additives”) may be further included. Such "other additives" include known additives.

Examples of additives include softeners, antioxidants, flame retardants, ultraviolet absorbers, surfactants, antistatic agents, pigments, dyes, weather stabilizers, heat stabilizers, infrared absorbers, antiblocking agents, Antifogging agents, plasticizers, antioxidants, hydrochloric acid absorbers, crystal nucleating agents, antifungal agents, antibacterial agents, organic fillers, and the like, but are not limited thereto. These additives may be used singly or in combination of two or more.

Softeners include, for example, petroleum-based materials, including process oils, lubricating oils, paraffins, liquid paraffins, polyethylene waxes, polypropylene waxes, petroleum asphalts and petroleum jelly; coal tars, including coal tar and coal tar pitch; castor oil. , fatty oils including linseed oil, rapeseed oil, soybean oil and coconut oil; waxes including tall oil, beeswax, carnauba wax and lanolin; ricinoleic acid, palmitic acid, stearic acid, 12-hydroxy stearic acid, montan Acids, fatty acids including oleic acid and erucic acid, or metal salts thereof; synthetic polymers including coumarone-indene resins and atactic polypropylene; ester plasticizers including dioctyl phthalate, dioctyl adipate and dioctyl sebacate; Wax, liquid polybutadiene or modified or hydrogenated products thereof; and known softeners including liquid thiocol.

Further, softening agents include, for example, aromatic carboxylic acid esters (dibutyl phthalate, etc.), aliphatic carboxylic acid esters (methylacetyl ricinoleate, etc.), aliphatic dicarboxylic acid esters (adipic acid-propylene glycol-based polyesters, etc.), Aliphatic tricarboxylic acid esters (triethyl citrate, etc.), phosphate triesters (triphenyl phosphate, etc.), epoxy fatty acid esters (epoxybutyl stearate, etc.), and the like can be mentioned.

Examples of antioxidants include phenolic antioxidants (2,6-di-t-butyl-4-methylphenol, etc.), polycyclic phenolic antioxidants (2,2′-methylenebis(4-methyl- 6-t-butylphenol) and other methylene-bridged polycyclic phenols), phosphorus antioxidants (tetrakis(2,4-di-t-butylphenyl)-4,4-biphenylene diphosphonate, etc.), amines system antioxidants (N,N-diisopropyl-p-phenylenediamine, etc.) and the like.

Examples of flame retardants include ammonium polyphosphate, ethylenebistris(2-cyanoethyl)phosphonium chloride, tris(tribromophenyl)phosphate, tris(tribromophenyl)phosphate, tris(3-hydroxypropyl)phosphine oxide, and the like. Chlorinated paraffin, chlorinated polyolefin, perchlorocyclopentadecane and other chlorinated flame retardants; hexabromobenzene, ethylenebisdibromonorbornanedicarboximide, ethylenebistetrabromophthalimide, tetrabromobisphenol Brominated flame retardants such as A derivatives, tetrabromobisphenol S, and tetrabromodipentaerythritol; and mixtures thereof.

Examples of ultraviolet absorbers include benzotriazole-based, benzophenone-based, salicylic acid-based, acrylate-based, and the like.

Antibacterial agents include, for example, quaternary ammonium salts, pyridine compounds, organic acids, organic acid esters, halogenated phenols, organic iodine and the like.

Surfactants can include, for example, nonionic, anionic, cationic or amphoteric surfactants. Nonionic surfactants include polyethylene glycol type nonionic surfactants such as higher alcohol ethylene oxide adducts, fatty acid ethylene oxide adducts, higher alkylamine ethylene oxide adducts and polypropylene glycol ethylene oxide adducts; Examples include polyhydric alcohol type nonionic surfactants such as fatty acid esters, pentaerythritol fatty acid esters, sorbit or sorbitan fatty acid esters, polyhydric alcohol alkyl ethers, and alkanolamine fatty amides. Examples of anionic surfactants include sulfate ester salts such as alkali metal salts of higher fatty acids, sulfonates such as alkylbenzenesulfonates, alkylsulfonates and paraffin sulfonates; and higher alcohol phosphates. phosphate ester salts such as Cationic surfactants include quaternary ammonium salts such as alkyltrimethylammonium salts. Amphoteric surfactants include amino acid-type amphoteric surfactants such as higher alkylaminopropionates; and betaine-type amphoteric surfactants such as higher alkyldimethylbetaines and higher alkyldihydroxyethylbetaines.

Antistatic agents include, for example, the above surfactants, fatty acid esters and polymeric antistatic agents. Examples of fatty acid esters include esters of stearic acid and oleic acid, and examples of polymeric antistatic agents include polyether ester amides.

Examples of pigments include inorganic pigments (titanium oxide, iron oxide, chromium oxide, cadmium sulfide, etc.) and organic pigments (azo lake-based, thioindigo-based, phthalocyanine-based, anthraquinone-based). Examples of dyes include azo-type, anthraquinone-type and triphenylmethane-type dyes.

The amount of the various additives added is not particularly limited depending on the application as long as the effects of the present invention are not impaired. It is preferably 10 parts by mass.

Further, the resin composition of the present invention includes a copolymer (A), a polyolefin thermoplastic elastomer (B), an ethylene polymer (C), a petroleum resin (D), and Polymers that do not correspond to "other additives" (hereinafter also referred to as "other polymers") may be contained. In that case, the content of the "other polymer" in the resin composition is a total of 100 mass of the copolymer (A), the polyolefin thermoplastic elastomer (B), the ethylene polymer (C), and the petroleum resin (D). It is preferably 20 parts by mass or less, more preferably 10 parts by mass or less.

[Method for producing resin composition]
The method for producing the resin composition of the present invention is not particularly limited, and for example, conventionally known production methods can be used. A copolymer (A), a polyolefin thermoplastic elastomer (B), an ethylene polymer (C), a petroleum resin (D), and optionally "other components" and/or "others" constituting the resin composition of the present invention A method of dry-blending the "polymer" using a known mixer can be mentioned. Here, examples of the mixer include a Henschel mixer, a tumbler blender, a V-blender, and the like.

After dry blending with the above mixer, for example, a method of melt kneading with a single screw extruder, twin screw extruder, Banbury mixer, kneader, roll mill, etc. at a temperature setting of 180 to 240 ° C., and then granulating or pulverizing. can be adopted. Among these, melt-kneading using a twin-screw extruder or a Banbury mixer is preferable from the viewpoint of mixability and productivity of each component. By these methods, it is possible to obtain resin composition pellets in which each component is uniformly mixed and dispersed.

<Friction body>
One embodiment of the present invention is a friction body containing the above resin composition. The friction body of the present invention can be suitably produced by injection molding from the above resin composition, although there is no limitation on the production method thereof.

The friction body of the present invention is used for discoloring and erasing handwriting and drawing by rubbing handwriting and drawing with thermochromic ink in the same manner as conventional friction bodies. At that time, the frictional body of the present invention acts as an elastic body to generate frictional heat during rubbing, and further acts as a viscous body to obtain the performance of adsorbing and peeling the thermochromic ink. That is, a single friction body can have both chemical erasability and physical erasability.

By attaching the friction body of the present invention to the main body of a conventional writing instrument, even if the handwriting or drawing is made with the newly configured ink, residual color is generated around the handwriting or drawing when erasing, and the appearance is spoiled. It is possible to obtain a writing instrument having both convenience and practicality that can ensure sufficient erasability. In this case, since the friction body of the present invention can be formed of a single member in the same manner as the friction body provided in the conventional writing instrument main body, the exterior itself of the writing instrument can be used as it is, resulting in high versatility.

In addition, since the friction body of the present invention can exhibit a physical erasing action by adsorption and detachment similar to that of a conventional eraser, it is possible to detach graphite from paper, for example. Therefore, the friction body of the present invention can constitute a new erasing tool that enables the thermal discoloration of thermochromic ink and the removal of handwriting or drawing with a pencil lead, a sharp lead, or the like, with a single friction body.

Furthermore, the friction body of the present invention can reduce the coefficient of static friction and suppress peeling and breakage on paper when handwriting or drawing is manually rubbed. On the other hand, since thermal discoloration can be accelerated by improving the coefficient of dynamic friction, excellent erasability for thermochromic ink can be obtained. In particular, it is advantageous for erasing handwriting and drawings on paper such as colored paper with low surface strength. As the "surface strength" of paper, for example, JAPAN TAPPI No. It can be evaluated by a test method based on 1:2000. A specific method for measuring the coefficient of friction is as described in Examples below.

[Thermochromic ink]
As the thermochromic ink, any conventional general-purpose ink that can be discolored or decolored by heating can be applied. The colorant to be incorporated in the ink includes at least the three essential components of the reaction medium that determine the temperature at which the color reaction of the electron-donating organic compound, the electron-accepting compound, and the color reaction of the above two occur. Pigments using a discoloring composition are preferred, and microcapsule pigments obtained by encapsulating a reversible thermochromic composition in microcapsules are particularly effective.

As a reversible thermochromic composition, before and after a predetermined temperature (discoloration point) described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-29398, etc. At a temperature range above the high-temperature side color change point, it becomes a discolored state, and at a temperature range below the low-temperature side color change point, it exhibits a colored state. One state is maintained as long as the heat or cold required to develop that state is applied, but when the application of the heat or cold is no longer applied, the hysteresis width returns to the state exhibited in the normal temperature range. A reversible thermochromic composition having a relatively small characteristic (ΔH of 1 to 7° C.) can be exemplified, and a heat-discolorable microcapsule pigment obtained by encapsulating this in microcapsules can be applied.

Furthermore, as reversible thermochromic compositions, relatively large Those exhibiting hysteresis characteristics (ΔH value is 8 to 50 ° C.), described in JP-A-2006-137886, JP-A-2006-188660, JP-A-2008-45062, JP-A-2008-280523, etc. An example that exhibits a large hysteresis characteristic can be exemplified. A large hysteresis characteristic means that the shape of the curve that plots changes in color density due to temperature changes is when the temperature rises from the lower temperature side than the discoloration temperature range, and conversely, when the temperature falls from the higher temperature side than the discoloration temperature range. This suggests that in some cases the color change follows very different routes.

Such a reversible thermochromic composition has a color memory property in a specific temperature range in a coloring state in a low temperature range below the complete coloring temperature or in a decoloring state in a high temperature range above the complete coloring temperature. A heat-erasable microcapsule pigment containing is also applicable.

As a reversible thermochromic composition having color memory, specifically, the complete coloring temperature is -30 ° C. to -10 ° C. as a temperature that can be obtained only in a freezer room, a cold region, etc., and the color is completely decolored. By specifying the temperature in the range of 60° C. to 80° C. as the temperature obtained by the frictional heat of the friction body and specifying the ΔH value in the range of 40° C. to 100° C., the color exhibited in the normal state (daily life temperature range). What works effectively for retention can be mentioned.

When using the microcapsule pigment encapsulating the reversible thermochromic composition, those having an average particle diameter of, for example, 0.5 μm to 3.0 μm are suitable from the viewpoint of writing performance and handwriting density. Furthermore, for the purpose of more efficiently exhibiting the decoloring performance using the friction body of the present invention, when the average particle size of the microcapsule pigment is 2.0 μm or more, chemical decoloring due to frictional heat Since decoloring (discoloration) using physical erasing by adsorption and peeling becomes possible, it is highly effective for irreversible erasing and discoloration. For the average particle diameter, for example, the particle area is determined using image analysis type particle size distribution measurement software (Mac-View manufactured by Mountec), and the projected area circle equivalent diameter (Heywood diameter) is calculated from the area of the particle area. It is a value measured as an average particle diameter of particles equivalent to a sphere of equal volume based on the calculated value.

Further, when the particle diameter of all or most of the particles of the microcapsule pigment encapsulating the reversible thermochromic composition exceeds 0.2 μm, for example, a precision particle size distribution measuring device (Beckman Coulter Multisizer 4e) can be used to measure the average particle size of particles equivalent to a sphere of equal volume by the Coulter method.

Furthermore, as the colorant component, dyes, general pigments, and the like can be used in order to impart a desired hue to handwriting without thermal discoloration. For example, as dyes, acid dyes, basic dyes, direct dyes, and the like can be used. General pigments include inorganic pigments such as carbon black and ultramarine blue, organic pigments such as copper phthalocyanine blue and benzidine yellow, as well as dispersion pigment products that are finely and stably dispersed in a medium using surfactants in advance. is used. In addition, metallic luster pigments such as metal powders and pearl pigments, fluorescent pigments, phosphorescent pigments, and special pigments such as titanium dioxide can also be used. These colorant components may be used in combination with the microcapsule pigment containing the reversible thermochromic composition, or may be encapsulated in the microcapsule pigment.

In particular, when a metallic luster pigment is added to a thermochromic ink, a metallic ink can be formed, so that when writing, a glossy and highly decorative handwriting is formed, which makes the ink more useful. Further, when the microcapsule pigment encapsulating the reversible thermochromic composition is used as a coloring agent, the handwriting on the white paper obtained when the thermochromic microcapsule pigment becomes transparent has no luster. Transparent metallic luster pigments are useful because they appear to be completely erased.

When erasing the above handwriting, it is necessary to perform heat discoloration and peeling removal, so conventionally, it was necessary to use two types of friction body made of an elastic body with a high surface hardness and an elastic body or an eraser with a low surface hardness. . However, the friction body of the present invention is particularly convenient because it can be decolored (discolored) by frictional heat and adsorption/separation in a single rubbing operation using one friction body. The metallic luster pigment to be used is a solid powder, and when the average particle diameter is 10 μm or more, a handwriting with high luster can be obtained and the adsorption and detachment properties are high. is used as a writing utensil set, it exerts a high effect on handwriting decoration and irreversible erasability.

Examples of transparent metallic luster pigments include luster pigments having a core material selected from natural mica, synthetic mica, flat glass flakes, and flaky aluminum oxide coated with a metal oxide, and cholesteric pigments. Liquid crystal type luster pigments and the like can be mentioned. Luminous pigments generally refer to pigments that develop a pearl-like deep luster by utilizing multiple reflections of light and interference phenomena.

Luminescent pigments having natural mica as a core substance are effective in those whose surface is coated with titanium oxide, and those whose upper layer of titanium oxide is coated with iron oxide or non-thermochromic dyes and pigments. , Merck's Iriodin (registered trademark), and BASF's Lumina (registered trademark).

Luster pigments having synthetic mica as a core material are effective when the surface is coated with a metal compound such as titanium oxide. Examples of metal oxides include metal oxides of titanium, zirconium, chromium, vanadium, iron, and the like, preferably metal oxides containing titanium oxide as a main component. Specifically, commercially available products such as Ultimica (registered trademark) manufactured by Nihon Koken Kogyo Co., Ltd. can be mentioned.

Luminescent pigments having a flat glass piece as a core material are effective when the surface is coated with a metal oxide such as titanium oxide. I can list what is being done.

Luster pigments having flaky aluminum oxide as a core substance are effective when the surface is coated with a metal oxide such as titanium oxide. Examples of oxides include metal oxides containing titanium oxide as a main component. Specifically, commercial products such as Xirallic (registered trademark) manufactured by Merck Co., Ltd. can be mentioned.

The liquid crystal polymer used as the cholesteric liquid crystal type bright pigment has the property of reflecting only a part of the incident light in a wide spectral range due to the interference effect of light, and transmitting the light in all other regions. , It has both excellent metallic luster, color flop properties that change the hue depending on the viewpoint, and transparency. Specific examples of the cholesteric liquid crystal type bright pigment include commercially available products such as Helicone HC (registered trademark) manufactured by Wacker Chemie. In addition, commercially available products such as Elgy neo (registered trademark) manufactured by Oike Kogyo Co., Ltd. may be mentioned as bright pigments obtained by vacuum-depositing a metal such as gold or silver on a film, peeling off the foil, and finely pulverizing the pigment. can.

The above metallic luster pigment preferably has an average particle size of 10 to 40 μm from the viewpoint of writing performance and brightness. The average particle size is measured using, for example, a laser diffraction/scattering particle size distribution analyzer (LA-350 manufactured by Horiba, Ltd.), and the average particle size ( median diameter) can be calculated.

In particular, metallic lustrous pigments having an average particle size of 10 μm or more have extremely high brightness, but are difficult to penetrate into the surface of paper during writing. Therefore, rubbing with a conventional friction body made of an elastic body tends to scatter, and depending on the viewing angle, the metallic luster pigment scattered over the entire rubbed portion can be seen, which may impair the appearance. In particular, on black paper, high brilliance is emphasized, which makes the appearance even worse. On the other hand, by rubbing with a friction body made of a viscoelastic material, the metallic luster pigment can be adsorbed and peeled off without being scattered on the rubbed portion, and the handwriting can be erased cleanly. Therefore, handwriting with metallic luster thermochromic ink can be decolored (discolored) using chemical decoloring by frictional heat and physical erasing by adsorption peeling, so irreversible erasing and discoloration It is particularly effective.

Various additives can also be added to the thermochromic ink as necessary. In the case of water-based inks, conventionally applied pH adjusters, rust inhibitors, antiseptics or anti-mold agents, wetting agents, antifoaming agents, surfactants, lubricants, fixing agents such as resins, shear thinning agents, etc. Viscosity-imparting agents, anti-drying agents for nib, anti-sagging agents, etc. can be added. In the case of oil-based inks, conventionally applied viscosity modifiers, preservatives, rust inhibitors, antifoaming agents, lubricants, dispersants, anti-scratch agents, anti-leaking agents, surfactants, etc. are added. be able to.

<Writing implements>
One embodiment of the present invention is a writing instrument having the above friction body. In the writing instrument of the present invention, the friction body is constructed in a form capable of rubbing handwriting and put into practical use. In this case, the friction body may be configured independently, or may be configured in a grippable state, such as being attached to another member such as a hard resin in such a manner that the friction portion can come into contact with handwriting (paper surface). In addition, it can be configured as a thermochromic writing instrument form provided in a writing instrument containing thermochromic ink, or as a writing instrument form containing thermochromic ink as a separate body. For example, the writing instrument of the present invention includes a writing instrument main body and the above-described friction body attached to the writing instrument body, and incorporates thermochromic ink in the writing instrument body.

Examples of the form of the writing instrument of the present invention include a fountain pen, a marking pen, a ballpoint pen, a lame ballpoint pen, and a retractable solid writing instrument. Alternatively, the pen tip may be of a retractable type that has a retractable mechanism such as a slide type, and the pen tip can be accommodated in the barrel. In the case of the retractable form, not only a type that accommodates one refill, but also a multiple type that accommodates two or more refills and allows desired refills to appear selectively. Moreover, it may be a double-ended type in which pen tips of different shapes are attached, or pen tips that lead out inks of different hues are attached.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Methods for measuring physical properties of resins, materials used for resin compositions, methods for preparing test pieces, and methods for evaluating physical properties in the following examples and comparative examples are as follows.

<Method for measuring resin physical properties>
[Constituent unit content]
Quantification of the contents of 4-methyl-1-pentene and α-olefin in the polymer was based on results measured by ¹³ C-NMR using the following equipment and conditions. However, the α-olefin content in the measurement results does not include the 4-methyl-1-pentene content.

Using a JEOL ECP500 type nuclear magnetic resonance apparatus, ortho-dichlorobenzene/deuterated benzene (80/20% by volume) mixed solvent, sample concentration 55 mg/0.6 mL, measurement temperature 120° C., observation nucleus is ¹³ C (125 MHz), sequence is single pulse proton decoupling, pulse width is 4.7 μs (45° pulse), repetition time is 5.5 seconds, integration count is 10,000 or more, chemical shift reference value is 27.50 ppm measured as The ¹³ C-NMR spectrum obtained was used to quantify the composition of 4-methyl-1-pentene/α-olefin.

[Limiting viscosity]
Intrinsic viscosity was measured at 135° C. in decalin solvent using an Ubbelohde viscometer. Specifically, about 20 mg of polymerized powder and pellets or resin lumps were first collected, dissolved in 15 mL of decalin, and the specific viscosity ηsp was measured in an oil bath heated to 135°C. Next, 5 mL of the decalin solvent was added to the decalin solution to dilute it, and then the specific viscosity ηsp was measured in the same manner. This dilution operation was repeated twice, and the value of ηsp/C when the concentration (C) was extrapolated to zero was calculated as the intrinsic viscosity (see the formula below).
[η]=lim(ηsp/C) (C→0)

[Melt flow rate (MFR)]
Measured at a temperature of 230° C. and 21.18 N according to ASTM D1238.

[Weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw/Mn value)]
Molecular weights were measured by gel permeation chromatography (GPC).
Specifically, a Waters ALC/GPC150-Cplus type (integrated differential refractometer detector) is used as a liquid chromatograph, and two Tosoh GMH6-HT and two GMH6-HTL are used as separation columns. Used in series connection, using o-dichlorobenzene as a mobile phase medium and 0.025% by mass of dibutylhydroxytoluene (manufactured by Takeda Pharmaceutical Co., Ltd.) as an antioxidant, the mobile phase medium was moved at 1.0 mL/min. , the sample concentration was 15 mg/10 mL, the sample injection volume was 500 μL, and a differential refractometer was used as the detector. As standard polystyrene, standard polystyrene manufactured by Tosoh Corporation was used with a weight average molecular weight (Mw) of 1,000 or more and 4,000,000 or less.

By analyzing the obtained chromatogram by creating a calibration curve using a standard polystyrene sample by a known method, the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw / Mn value ) was calculated. The measurement time per sample was 60 minutes.

〔density〕
Density was measured using a density gradient tube according to JIS K7112.

[Melting point (Tm)]
Based on JIS K7121, using a differential scanning calorimeter Discovery DSC2500 manufactured by TA Instruments Co., Ltd., the highest temperature at the top of the melting peak measured at a heating rate of 10° C./min was taken as the melting point.

Materials Used for Resin Composition <Synthesis of Copolymer (A)>
As a copolymer (A), a copolymer (A-1) in which the content of 4-methyl-1-pentene and the content of an α-olefin having 2 to 4 carbon atoms are adjusted is prepared as follows. Synthesized.

<Synthesis of copolymer (A-1)>
300 ml of n-hexane (dried over activated alumina under a dry nitrogen atmosphere) and 450 ml of 4-methyl-1-pentene were placed in a 1.5 L SUS autoclave equipped with a stirring blade that was sufficiently purged with nitrogen at 23°C. entered. The autoclave was charged with 0.75 ml of a 1.0 mmol/ml toluene solution of triisobutylaluminum (TIBAL) and stirred.

Next, the autoclave was heated to an internal temperature of 60° C. and pressurized with propylene so that the total pressure (gauge pressure) was 0.40 MPa. Subsequently, 1 mmol of methylaluminoxane prepared in advance in terms of aluminum and 0.01 mmol of diphenylmethylene (1-ethyl-3-t-butyl-cyclopentadienyl)(2,7-di-t-butyl 0.34 ml of a toluene solution containing zirconium dichloride (fluorenyl) was injected into the autoclave with nitrogen to initiate the polymerization reaction.

During the polymerization reaction, the temperature was adjusted so that the internal temperature of the autoclave was 60°C. After 60 minutes from the initiation of polymerization, 5 ml of methanol was injected into the autoclave under pressure with nitrogen to stop the polymerization reaction, and then the pressure inside the autoclave was released to atmospheric pressure. After the pressure was released, the reaction solution was stirred while adding acetone.

The obtained powdery copolymer containing the solvent was dried at 100° C. under reduced pressure for 12 hours. The weight of the copolymer (A-1) as a product was 36.9 g, the content of 4-methyl-1-pentene in the copolymer (A-1) was 72.4 mol%, and the content of propylene was 72.4 mol%. The amount was 27.6 mol %. No melting point was observed when measured with a differential scanning calorimeter (DSC). Table 1 shows the measurement results of each physical property.

<Measurement of dynamic viscoelasticity>
A predetermined amount of the copolymer (A-1) obtained by the above method was filled in a SUS mold. Set the heating platen to 200 ° C., use a hydraulic heat press (NSF-50 manufactured by Shindo Kinzoku Kogyo Co., Ltd.), preheat for 7 minutes, pressurize for 2 minutes at a gauge pressure of 10 MPa, and then set to 20 ° C. Cooling. It was transferred to a board, compressed at a gauge pressure of 10 MPa and cooled for 3 minutes to prepare a press sheet for measurement with a thickness of 2 mm.

Next, the press sheet for measurement with a thickness of 2 mm obtained by the above method was measured by a rheometer (MCR301 manufactured by Anton Paar) in torsion mode, frequency of 10 rad/s (1.6 Hz), strain amount of 0.1%, and elevation. The temperature dispersion of dynamic viscoelasticity was observed at -40 to 150°C at a temperature rate of 2°C/min, and the tanδ peak value and tanδ peak temperature were measured. Table 1 shows the results.

<Polyolefin Thermoplastic Elastomer (B)>
The following was used as the polyolefin thermoplastic elastomer (B).
Polyolefin-based thermoplastic elastomer (B-1): Mitsui Chemicals Milastomer 6030NS [MFR: 40 g/10 minutes (temperature: 230°C, 98.07 N), density: 880 kg/m ³ , surface hardness: Shore A58]
Polyolefin-based thermoplastic elastomer (B-2): Mitsui Chemicals Milastomer 7030NS [MFR: 35 g/10 minutes (temperature: 230°C, 98.07 N), density: 880 kg/m ³ , surface hardness: Shore A70]

<Ethylene polymer (C)>
The following was used as the ethylene polymer (C).
Ethylene polymer (C-1): Prime Polymer Evolue SP4030 [linear low-density polyethylene (LLDPE), <MFR: 3.8 g/10 min (temperature: 190°C, 21.18 N)], density: 938 kg/ m ³ , melting point (Tm): 127° C., surface hardness: Shore D59]

<Petroleum resin (D)>
The following were used as the petroleum resin (D).
Petroleum resin (D-1): Alcon P-125 [alicyclic saturated hydrocarbon resin, softening point 125° C.] manufactured by Arakawa Chemical Industries, Ltd. was used.

Production of resin composition Tri(2,4-di -t-butylphenyl) phosphate at 1000 ppm, n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl) propinate at 1000 ppm as a heat stabilizer, and stearate as a hydrochloric acid absorbent. 500 ppm of calcium phosphate was blended.

Next, using a twin-screw extruder (TEX25αIII manufactured by Japan Steel Works, Ltd., screw diameter Φ25 mm, L / D = 52), a strand is extruded under the conditions of a cylinder setting temperature of 200 ° C., an extrusion rate of 5 kg / hour, and a screw rotation speed of 100 rpm. It was discharged, and while immersed in a water tank, was guided to a pelletizer (KM-100 manufactured by Katsumic Co., Ltd.), where it was granulated to obtain pellets as an exemplary form of the resin composition.

<Production of press sheet for measurement>
A predetermined amount of each pellet of the resin composition obtained by the above method was filled in a SUS mold. The heating platen temperature was set to 200 ° C., and a hydraulic heat press (NSF-50 manufactured by Shindo Kinzoku Kogyo Co., Ltd.) was used to preheat for 7 minutes and pressurize for 2 minutes at a gauge pressure of 10 MPa, and then set to 20 ° C. It was transferred to a cooling plate, compressed at a gauge pressure of 10 MPa and cooled for 3 minutes to prepare a press sheet for measurement with a thickness of 2 mm.

<Surface hardness>
Three press sheets for measurement with a thickness of 2 mm obtained by the above method were stacked to form a test piece, and immediately after pressing the indenter of the hardness tester against the surface of the test piece at 23 ° C. and after 15 seconds according to ASTM D2240. The Shore A hardness was measured for each of Based on each Shore A hardness value, the value of ΔHS was calculated by the following formula. Those results are shown in Table 2.
ΔHS = [Shore A hardness value immediately after start of contact with indenter] - [Shore A hardness value 15 seconds after start of contact with indenter]

<Stress absorption>
A press sheet for measurement with a thickness of 2 mm prepared according to the method of "Preparation of press sheet for measurement" was punched into predetermined dimensions (length 35 mm, width 10 mm), and a rheometer (MCR301 manufactured by Anton Paar) was used. Then, under the conditions of torsion mode, frequency of 10 rad/s (1.6 Hz), strain amount of 0.1%, and temperature increase rate of 2 ° C./min, the temperature dispersion of dynamic viscoelasticity was observed at -40 to 150 ° C., The tan delta peak value and tan delta peak temperature were measured. Table 2 shows the results.

Preparation of test piece Each pellet of the resin composition obtained by the above method is processed using an injection molding machine (ES75SX III manufactured by Toshiba Machine Co., Ltd.: clamping force 735 kN, screw diameter Φ32 mm) according to the examples and comparative examples described later. A test piece was prepared for use in calculating the coefficient of friction. The molding conditions and the contents of the test pieces are as follows.

〔Molding condition〕
Cylinder setting temperature: 180-220°C
Screw rotation speed: 100 rpm
Injection pressure: 18-24MPa
Injection speed: 15-20 mm/sec Mold temperature: 40°C
Cooling time: 40 seconds

〔Test pieces〕
A test piece was prepared by rounding one end of a cylinder (8 mm diameter, 50 mm length) with an R value of 4 mm.

<Calculation of friction coefficient>
A "friction body" was obtained by cutting a piece having a length of 10 mm from the rounded end portion of the test piece. Next, using a Gakushin abrasion tester (Tribogear Type 30S manufactured by Shinto Kagaku Co., Ltd.), the indenter was attached so that the rounded end of the "friction body" became a sliding part, and the test load was 1000 gf. At a speed of 7500 mm/min and a moving distance of 100 mm, one sheet of each of the following two types of paper was placed on the sliding table, and the static friction coefficient and the dynamic friction coefficient were calculated. Table 2 shows the results.

[Paper type]
・Plain paper (white paper): PPC Paper Type-Fw (thickness 0.090 mm, basis weight 67 g/m ² )
- Black paper: colored drawing paper manufactured by Toyo Corporation (thickness 0.174 mm, basis weight 114 g/m ² )

<Erasure test>
A black pencil (Mitsubishi Pencil 9800H) and a writing instrument filled with thermochromic ink ("Friction Ball" manufactured by Pilot Corporation: Black, 0.7 mm) are handwritten on the surface of the above "plain paper (white paper)" to create a spiral shape. After five consecutive circles were written, the paper surface was rubbed by hand so that the rounded edge of the "test piece" and the paper surface were in contact with each other, and the decolored state was visually observed and evaluated. Also, the state of the paper surface after rubbing was visually observed and evaluated.

Furthermore, on the surface of the "black paper", a writing instrument filled with a thermochromic ink containing a metallic luster pigment (lame ballpoint pen "Keserame" manufactured by Pilot Corporation: pink, 0.7 mm) is handwritten to draw a spiral circle. After five consecutive writings were made, the paper surface was rubbed with a hand so that the rounded edge of the "test piece" and the paper surface were in contact with each other, and the decolorized state was visually observed and evaluated. Also, the state of the paper surface after rubbing was visually observed and evaluated. Criteria for each evaluation are as follows. These results are shown in Table 2.

[Handwriting erasability]
A: No residual color was observed, and the handwriting was erased.
B: A faint handwriting remained.
C: Graphite or thermochromic ink diffused on the paper surface, making it difficult to erase handwriting.

[Paper condition]
A: There was no problem with the paper surface.
B: Slight peeling was observed on the paper surface.
C: Peeling and breakage were observed on the paper surface.

[Example 1]
Copolymer (A-1) 35 parts by mass, polyolefin thermoplastic elastomer (B-1) 40 parts by mass, ethylene polymer (C-1) 20 parts by mass, and petroleum resin (D-1) 5 parts by mass A total of 100 parts by mass [with respect to 100 parts by mass of the resin component, 1000 ppm of tri(2,4-di-t-butylphenyl) phosphate, n-octadecyl-3-(4'-hydroxy-3',5'- 1000 ppm of di-t-butylphenyl)propinate and 500 ppm of calcium stearate were blended. ] to obtain pellets of the resin composition (X-1) according to the method of “Preparation of resin composition” above.

Next, a "measurement press sheet" and a "test piece" were produced according to the above method, and the physical properties were evaluated according to the above contents.

[Example 2]
A pellet of the resin composition (X-2) was obtained in the same manner as in Example 1 except that the resin component was changed to the composition shown in Table 2, and the physical properties were evaluated in the same manner as in Example 1. Ta.

[Example 3]
A pellet of the resin composition (X-3) was obtained in the same manner as in Example 1 except that the resin component was changed to the composition shown in Table 2, and the physical properties were evaluated in the same manner as in Example 1. .

[Example 4]
A pellet of the resin composition (X-4) was obtained in the same manner as in Example 1 except that the resin component was changed to the composition shown in Table 2, and the physical properties were evaluated in the same manner as in Example 1. Ta.

[Comparative Example 1]
A pellet of the resin composition (Y-1) was obtained in the same manner as in Example 1 except that the resin component was changed to the composition shown in Table 2, and the physical properties were evaluated in the same manner as in Example 1. Ta.

[Comparative Example 2]
A pellet of the resin composition (Y-2) was obtained in the same manner as in Example 1 except that the resin component was changed to the composition shown in Table 2, and the physical properties were evaluated in the same manner as in Example 1. Ta. In Table 2, the thermoplastic polystyrene elastomer (E-1) is S.T. O. E. "S1605", MFR: 5 g/10 min (temperature 230°C, 21.18 N), surface hardness: Shore A87)) was used.

Table 2 shows the results of evaluation of physical properties of Examples 1-4 and Comparative Examples 1-2.

Since the friction bodies obtained in Examples 1 to 4 exhibit performance as elastic bodies, it was shown that graphite and thermochromic ink can be effectively erased by rubbing handwriting. In addition, when rubbing writing on colored paper with low surface strength, the static friction coefficient is reduced to suppress peeling and damage on the paper surface, while the dynamic friction coefficient is improved to promote thermal discoloration, resulting in a metallic luster. It was shown that the pigment can be adsorbed and removed, and that the erasability of the thermochromic ink is excellent.

Claims (6)

10 to 50 parts by mass of a 4-methyl-1-pentene/α-olefin copolymer (A) satisfying the following requirements (Aa) to (Ae),
Polyolefin thermoplastic elastomer (B) 10 to 50 parts by mass,
Ethylene polymer (C) 5 to 30 parts by mass,
and petroleum resin (D) 0.1 to 20 parts by mass [where the total of (A), (B), (C) and (D) is 100 parts by mass. ] A resin composition containing;
(Aa) 60 to 78 mol% of structural units (i) derived from 4-methyl-1-pentene and 40 to 22 mol% of structural units (ii) derived from an α-olefin having 2 to 4 carbon atoms [However, the total of the structural unit (i) and the structural unit (ii) shall be 100 mol %. ];
(Ab) the intrinsic viscosity [η] measured in decalin at 135°C is in the range of 0.5 to 4.0 dl/g;
(Ac) The molecular weight distribution (Mw/Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gemipermeation chromatography (GPC), is 1.0 to 4.0. in the range of 0;
(A−d) having a density in the range of 825-860 kg/m ³ ;
(Ae) Melting point (Tm) measured by differential scanning calorimeter (DSC) is not observed. The resin composition according to claim 1, wherein the 4-methyl-1-pentene/α-olefin copolymer (A) satisfies the following requirements (Af) to (Ag);
(Af) In the temperature range of -40 to 150°C, dynamics measured under the conditions of torsion mode, frequency of 10 rad/s (1.6 Hz), heating rate of 2°C/min, and strain amount of 0.1%. the maximum value of the viscoelastic loss tangent tan δ is in the range of 1.0 to 5.0;
(Ag) In the temperature range of -40 to 150 ° C., the dynamics measured under the conditions of torsion mode, frequency of 10 rad/s (1.6 Hz), heating rate of 2 ° C./min, and strain amount of 0.1%. The temperature at which the value of the loss tangent tan δ of the physical viscoelasticity is maximized is in the range of 10 to 38°C. The resin composition according to claim 1 or 2, which satisfies the following requirements (x) and (y);
(x) Shore A hardness measured in accordance with ASTM D2240 15 seconds after the start of indenter contact is 60 to 85;
(y) In Shore A hardness measured in accordance with ASTM D2240, the difference between the value of Shore A hardness immediately after contact with the indenter and the value of Shore A hardness 15 seconds after contact with the indenter shown by the following formula ( ΔHS) is 5-18.
ΔHS = (Shore A hardness value immediately after contact with the incisor) - (Shore A hardness value 15 seconds after contact with the incisor) A friction body comprising the resin composition according to any one of claims 1 to 3. 5. The friction body according to claim 4, which is an injection molded body. A writing instrument comprising the friction body according to claim 4 or 5.