JP7456825B2 - Composition for friction body, friction body and writing instrument - Google Patents

Description

The present invention relates to a composition for a friction body containing a 4-methyl-1-pentene/α-olefin polymer, a friction body, and a writing instrument equipped with the friction body. In particular, the present invention relates to a composition for a friction body, a friction body, and a writing instrument equipped with a friction body for thermally discoloring handwriting, printed images, etc. made of graphite, thermochromic ink, etc. by friction.

As a means of discoloring the heat discolored areas formed on the paper surface by writing or printing, a friction body is used that uses an elastic material such as an eraser made of polyvinyl chloride (PVC) or rubber, and discolors due to the frictional heat generated by manual friction. . In addition, in recent years, thermochromic writing implements have been widely used that contain thermochromic ink and can erase or change the color of handwriting by heating it. In the above-mentioned writing instruments, a friction body made of an elastic material is used in order to quickly and easily heat-change the handwriting formed on the paper surface, and the friction body is integrally formed on the rear end of the barrel, the base, the cap, etc. of the writing instrument. In addition, it is put into practical use by being provided separately.

On the other hand, since the friction materials currently on the market are elastic materials, they cannot be used against handwriting made with current heat-erasable ink that uses only thermochromic materials as coloring components. Can be chemically decolored.

Patent Document 1 describes a writing instrument that uses a resin material with a specific hardness or higher as a friction body, and when applying the friction body as a friction part formed on a support base material of the friction implement, it is possible to use a writing instrument using two-color molding. It is described that it is fixed to a supporting base material. However, in this writing instrument, the combinations of the support base material and the friction body are limited, so the degree of freedom of each material is low. In addition, complex molds are required to mold the friction body, and the thickness of the friction body must be increased in order to obtain moldability.Furthermore, since the friction body is an elastic body, it is difficult to erase handwriting. It was necessary to apply considerable force.

Patent Documents 2 and 3 disclose writing implements using an elastic body such as a styrene elastomer as a friction body, but these friction bodies do not have sufficient heat erasing properties, especially for metallic handwriting. There was a need for improvement. Further, Patent Document 4 discloses that a heat-erasable ink contains a metallic luster pigment for the purpose of creating metallic handwriting, and a friction body, a writing instrument, and a writing instrument that exhibit a heat-erasable effect on these handwritings are also disclosed. Although a writing set has been disclosed, when the heat erasing effect is increased, the friction body becomes soft and breaks due to heating, so further improvements are required in order to achieve both mechanical strength and heat erasability.

JP 2007-223302 A Japanese Patent Application Publication No. 2009-143207 Japanese Patent Application Publication No. 2011-156832 WO2018/116767

The present invention solves the above-mentioned problems in a friction body, and provides handwriting using a new metallic-like ink in which a metallic luster pigment is added to graphite, non-color-changing ink, or thermochromic ink. Another object of the present invention is to provide a friction body that can simultaneously erase graphite, erase or change color of thermochromic materials, and peel off metallic luster pigments by rubbing handwriting.

Furthermore, the present invention can erase ink without causing breakage due to the rubbing of the friction body with paper, ensure sufficient handwriting erasability with a light force without damaging the appearance during erasing, and erase color of thermochromic materials. The purpose of this invention is to provide a convenient and practical friction body and writing instrument that have both chemical and physical erasability, and can simultaneously perform color change and particle peeling. .

In addition, the present invention does not require complicating the respective structures or molds when attaching the friction portion to the support base material, and does not limit the material, and therefore, the attachment position can be adjusted without incurring high costs. The present invention provides a friction body with a wide range of designs and a writing instrument equipped with the friction body.

As a result of intensive studies to solve the above problems, it was discovered that the above problems could be solved by using a viscoelastic material, which is a combination of an elastic material and a viscous material, as a friction body, leading to the present invention. Note that the viscoelastic body is made of a material that has both the properties of a viscous body and the properties of an elastic body. Generally, a viscous material deforms in response to external force and does not return to its original shape even after the external force is removed. On the other hand, an elastic body deforms in response to external force, but returns to its original shape when the external force is removed. Whether a material is a viscoelastic material, or is close to a viscous material or an elastic material can be determined, for example, by looking at the relaxation time of stress relaxation (time change in stress) when a certain strain is applied to the material. If the relaxation time is sufficiently short relative to the time scale of observation, it can be said to be a viscous body, and if it is long, it can be said to be an elastic body, and if the relaxation time is on the same scale, it can be said to be a viscoelastic body.

That is, the gist of the present invention is as follows.
[1] Contains a 4-methyl-1-pentene/α-olefin copolymer (A) and a thermoplastic elastomer (B) that satisfy the following requirements (a) to (b), and the 4-methyl-1- A resin composition for a friction body in which the mass ratio [(A)/(B)] of the pentene/α-olefin copolymer (A) and the thermoplastic elastomer (B) is 10/90 to 67/33 ( X).
Requirement (a) : The melting point (Tm) of the copolymer (A) is 110° C. or higher and 160° C. or lower when calorimetrically measured using a differential scanning calorimeter (DSC).
Requirement (b) ; Copolymer (A) is derived from structural unit (i) derived from 4-methyl-1-pentene and α-olefin (excluding 4-methyl-1-pentene). 79 to 90 mol% of the structural unit (i) and 10 mol% of the structural unit (ii), assuming the total of the structural unit (i) and the structural unit (ii) to be 100 mol%. ~21 mol%.

[2] The resin composition (X) for a friction body according to [1], which satisfies the following requirements (x) to (y).
Requirement (x) ; Shore A hardness of the resin composition for friction body (X) 15 seconds after the start of contact with the indenter, measured with three 2 mm thick sheets stacked in accordance with JIS K6253. is 70 or more and 95 or less.
Requirement (y) : In accordance with JIS K6253, the Shore A hardness of the friction body resin composition (X) is measured by stacking three sheets with a thickness of 2 mm, and is expressed by the following formula. The difference ΔHS between the Shore A hardness value immediately after contact with the indenter and the Shore A hardness value 15 seconds after contact with the indenter is 5 or more and 20 or less.
ΔHS = (Shore A hardness value immediately after contact with the indenter - Shore A hardness value 15 seconds after contact with the indenter)

[3] The resin composition (X) for a friction body according to [1] or [2], which satisfies the following requirement (z).
Requirement (z) : A 2 mm thick sheet made of the friction body resin composition (X) is brought into contact with copy paper, and the 100 mm width is tested 200 times at 23° C. and 2 kg load at a test speed of 7500 mm/min. The amount of wear when reciprocating is 0.1 mg or less, and the amount of wear when reciprocating 500 times at 40° C. with a load of 1 kg is 0.1 mg or less.
[4] The friction body resin composition (X ).
Requirement ( c): The tan δ peak temperature obtained by performing dynamic viscoelasticity measurement at a frequency of 10 rad/s (1.6 Hz) in the temperature range of -40 to 150 °C is 20 °C or more and 45 °C or less.

[5] The resin composition (X) for a friction body according to [1] to [3], further comprising a crystalline polyolefin (C).
[6] A friction body comprising the friction body composition according to any one of [1] to [5].
[7] The friction body according to [6], wherein the friction body is produced by injection molding.

[8] A writing instrument comprising a writing instrument body and the friction body according to [6] or [7] attached to the writing instrument body, and containing thermochromic ink inside the writing instrument body.
[9] The writing instrument according to [8], wherein the thermochromic ink contains a thermochromic microcapsule pigment having an average particle diameter of 0.05 μm or more and 5.0 μm or less.
[10] The writing instrument according to [8], wherein the thermochromic ink contains a metallic luster pigment having an average particle diameter of 0.1 μm or more and 50 μm or less.

The friction body of the present invention erases graphite by rubbing the handwriting, even if the handwriting is made of graphite, non-color-changing ink, or metallic newly composed ink in which metallic luster pigment is added to thermochromic ink. It is also possible to simultaneously erase or change the color of thermochromic materials and remove metallic luster pigments.

Furthermore, the friction body of the present invention can erase ink without causing breakage due to rubbing against paper, can ensure sufficient handwriting erasability with a light force without impairing appearance during erasing, and can be used to erase thermochromic materials. Color or discoloration and particle exfoliation can be performed at the same time. That is, the friction body and writing instrument of the present invention are convenient and practical, having both chemical erasability and physical erasability.

In addition, the friction body of the present invention does not require complicated structures or molds when attaching the friction portion to the support base material, and does not require any restrictions on the material. You can choose from a wide range of mounting positions and designs.

The friction body resin composition (X), friction body, and writing instrument of the present invention will be explained below. The friction body resin composition (X) of the present invention comprises a 4-methyl-1-pentene/α-olefin copolymer (A) (hereinafter also referred to as copolymer (A)) and a thermoplastic elastomer (B). including.

In the friction body resin composition (X), the mass ratio of the 4-methyl-1-pentene/α-olefin copolymer (A) and the thermoplastic elastomer (B) [(A)/(B) ] is from 10/90 to 67/33. Specifically, when the total amount of the 4-methyl-1-pentene/α-olefin copolymer (A) and the thermoplastic elastomer (B) is 100 parts by mass, from the viewpoint of flexibility and stress relaxation, the above-mentioned The upper limit of the content of copolymer (A) in the composition is usually 67 parts by weight, preferably 50 parts by weight, more preferably 45 parts by weight, particularly preferably 40 parts by weight, and the lower limit is usually 10 parts by weight. Parts by weight, preferably 25 parts by weight, more preferably 30 parts by weight, particularly preferably 35 parts by weight.

The lower limit of the content of thermoplastic elastomer (B) is usually 33 parts by mass, preferably 50 parts by mass, more preferably 55 parts by mass, and particularly preferably 60 parts by mass, and the upper limit is usually 90 parts by mass, preferably 75 parts by mass, more preferably 70 parts by mass, and particularly preferably 65 parts by mass.
The friction body composition (X) of the present invention preferably satisfies the following requirements (x) and (y).

Requirement (x) ;
In accordance with JIS K6253, the Shore A hardness of the friction body composition (X) 15 seconds after the start of contact with the pusher needle is 70 or more and 95 or less, as measured by stacking three sheets with a thickness of 2 mm. and is preferably 75 or more and 95 or less, more preferably 78 or more and 95 or less.

Those whose Shore A hardness value immediately after the start of contact with the indenter is equal to or higher than the lower limit are particularly preferable because they have a high frictional heat generation efficiency and can easily thermally discolor handwriting. Note that the Shore A hardness value may be a value obtained by converting a measured Shore D hardness.

Requirement (y) ;
In accordance with JIS K6253, the Shore A hardness of friction body composition (X) is measured with three sheets stacked with a thickness of 2 mm, and the Shore A hardness value immediately after contact with the indenter and the indenter The difference ΔHS from the Shore A hardness value 15 seconds after contact is 5 or more and 20 or less, preferably 5 or more and 15 or less, and more preferably 5 or more and 13 or less.

Note that the above ΔHS is a value determined according to the following formula.
ΔHS = (Shore A hardness value immediately after contact with the indenter - Shore A hardness value 15 seconds after contact with the indenter)
When ΔHS is below the upper limit value, frictional heat can be generated more efficiently when handwriting on a paper surface is rubbed with a friction body obtained from the friction body composition (X). Moreover, when it is more than the said lower limit, the particulate matter (pigment) contained in handwriting can be more easily adsorbed and peeled off. ΔHS can be arbitrarily changed by changing the amount of the 4-methyl-1-pentene/α-olefin copolymer (A), comonomer species, and comonomer composition, and can also be adjusted arbitrarily by mixing multiple types.
It is preferable that the friction body composition (X) of the present invention further satisfies the following requirement (z).

Requirement (z) ;
When a 2 mm thick sheet made of the friction body resin composition (X) was brought into contact with copy paper and reciprocated 200 times across a 100 mm width at a test speed of 7500 mm/min at 23°C and a load of 2 kg. The amount of wear is 0.11 mg or less, preferably 0.10 mg or less. Further, the amount of wear when reciprocating 500 times at 40° C. under a load of 1 kg is 0.1 mg or less, preferably 0.08 mg or less, and more preferably 0.07 mg or less. When the amount of wear is below the upper limit value, no damage occurs when the friction body obtained from the friction body composition (X) rubs the handwriting and ink on the paper surface, and no shavings are generated. The amount of wear can be arbitrarily changed by changing the amount of the 4-methyl-1-pentene/α-olefin copolymer (A), the comonomer type, and the comonomer composition, and can also be adjusted arbitrarily by mixing multiple types.

The 4-methyl-1-pentene/α-olefin copolymer (A), thermoplastic elastomer (B), and crystalline polyolefin (C) that constitute the friction body resin composition (X) will be explained below.

<4-Methyl-1-pentene/α-olefin copolymer (A)>
The 4-methyl-1-pentene/α-olefin copolymer (A) satisfies the following requirements (a) and (b), preferably also satisfies (c), and further satisfies (d). More preferred.

Requirement (a) : The 4-methyl-1-pentene/α-olefin copolymer (A) has a melting point (Tm) of 110° C. or higher and 160° C. or lower when calorimetrically measured using a differential scanning calorimeter (DSC). By satisfying these requirements, it becomes possible to improve the tensile properties, reduce the amount of wear, and adjust the surface hardness of the friction body of the present invention.

Requirement (b) ; The 4-methyl-1-pentene/α-olefin copolymer (A) contains a structural unit (i) derived from 4-methyl-1-pentene and an α-olefin (however, 4-methyl -1-Excluding pentene), the total of which is 100 mol%, the structural unit (i) is 79 to 90 mol%, and the structural unit (ii) is 10 to 21 mol%. Consisting of

That is, the lower limit of the proportion of the structural unit (i) is 79 mol%, preferably 80 mol%, and more preferably 82 mol%. On the other hand, the upper limit of the proportion of the structural unit (i) is 90 mol%, preferably 88 mol%, and more preferably 86 mol%. As described above, in the present invention, the proportion of the structural unit (i) in the 4-methyl-1-pentene/α-olefin copolymer (A) is equal to or higher than the lower limit, so that the peak value of tan δ is reduced near room temperature. Since it has a high temperature, it has excellent shape followability and stress relaxation properties, and also has appropriate flexibility because the proportion of the structural unit (i) is below the upper limit.

Further, the upper limit of the proportion of the structural unit (ii) is 21 mol%, preferably 20 mol%, and more preferably 18 mol%. On the other hand, the lower limit of the proportion of structural unit (ii) is 10 mol%, preferably 12 mol%, and more preferably 14 mol%.

Examples of the α-olefin leading to the structural unit (ii) include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1- Straight chain α-olefins having 2 to 20 carbon atoms, preferably 2 to 15 carbon atoms, more preferably 2 to 10 carbon atoms, such as tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3 -Methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4,4-dimethyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene Branched α-olefins having 5 to 20 carbon atoms, preferably 5 to 15 carbon atoms, such as , 4-ethyl-1-hexene, and 3-ethyl-1-hexene. Among these, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene are preferred, and ethylene and propylene are particularly preferred.

Here, in one embodiment of the present invention, the 4-methyl-1-pentene/α-olefin copolymer (A) usually consists of only the structural unit (i) and the structural unit (ii). However, the 4-methyl-1-pentene/α-olefin copolymer (A) may further contain, as the structural unit (iii), a structural unit derived from another monomer that is neither 4-methyl-1-pentene nor the α-olefin that derives the structural unit (ii), in addition to the structural units (i) and (ii), so long as the amount is small enough not to impair the object of the present invention (for example, 10 mol % or less). Specific examples of such other monomers include 5-vinyl-2-norbornene and 5-ethylidene-2-norbornene when the copolymer (A) is a 4-methyl-1-pentene/propylene copolymer.

Requirement (c) ;
The tan δ peak temperature of the copolymer (A) obtained by performing dynamic viscoelasticity measurement at a frequency of 10 rad/s (1.6 Hz) in the temperature range of -40 to 150 °C is 20 °C or higher and 45 °C or lower. The temperature is preferably 25°C or more and 45°C or less, more preferably 30°C or more and 41°C or less, and even more preferably 35°C or more and 41°C or less. By setting the tan δ peak temperature of the 4-methyl-1-pentene/α-olefin copolymer (A) within the above temperature range, the value of tan δ at room temperature and the strength during friction can be further increased. Furthermore, by having a tan δ peak value at room temperature, the erasability of graphite and thermochromic ink of the friction body obtained from the copolymer (A) is improved.

Requirement (d);
The tan δ peak value obtained by performing dynamic viscoelasticity measurement at a frequency of 10 rad/s (1.6 Hz) in a temperature range of -40 to 150 ° C. is preferably 0.5 or more and 5.0 or less. , more preferably 0.7 or more and 4.0 or less, and even more preferably 0.9 or more and 3.5 or less.

When the tan δ peak value is within the above range, the viscosity characteristics at room temperature are increased, and as a result, the erasability of graphite and thermochromic ink of the friction body is improved.
A particularly preferable form of the 4-methyl-1-pentene/α-olefin copolymer (A) satisfies the following requirements (e) in addition to the above requirements (a), (b), (c) and (d). - (g) One or more, preferably two or more, more preferably all of the following are satisfied.

Requirement (e) ;
The density (measured according to ASTM D1505) is 830 to 870 kg/m ³ , preferably 830 to 865 kg/m ³ , more preferably 830 to 855 kg/m ³ . The details of the measurement conditions and the like are as described in the Examples section below.

The density can be changed as appropriate by changing the comonomer composition ratio of the 4-methyl-1-pentene/α-olefin copolymer (A), and the copolymer (A) with a density within the above range can be used as a lightweight friction body. Can be molded.

Requirement (f) ;
The ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (molecular weight distribution; Mw/Mn) measured by gel permeation chromatography (GPC) is 1.0 to 3.5, preferably 1. It is in the range of 2 to 3.0, more preferably 1.5 to 2.8. The details of the measurement conditions and the like are as described in the Examples section below. If the Mw/Mn is larger than 3.5, there is a concern that the influence of the low molecular weight, low stereoregular polymer resulting from the composition distribution may result in poor moldability.

Here, in the present invention, if the catalyst described below is used, 4-methyl-1-pentene α- satisfies the above requirement (f) within the range of the intrinsic viscosity [η] shown in the above requirement (g) An olefin copolymer (A) can be obtained. Note that the above Mw/Mn and the following Mw values are values measured by a method adopted in Examples described later.

Furthermore, the weight average molecular weight (Mw) of the 4-methyl-1-pentene/α-olefin copolymer (A) measured by gel permeation chromatography (GPC) is preferably 500 to 10 ,000,000, more preferably 1,000 to 5,000,000, even more preferably 1,000 to 2,500,000.

Requirement (g) ;
The intrinsic viscosity [η] measured in decalin at 135°C is in the range of 0.1 to 5.0 dL/g, preferably 0.5 to 4.0 dL/g, more preferably 0.5 to 3.5 dL/g. It is.
As will be described later, when hydrogen is used in combination during polymerization to produce a copolymer, the molecular weight can be controlled, and the intrinsic viscosity [η] can be adjusted by freely obtaining a product ranging from a low molecular weight product to a high molecular weight product. If the limiting viscosity [η] is smaller than 0.1 dL/g or larger than 5.0 dL/g, injection molding processability may be impaired.

<Production method of 4-methyl-1-pentene/α-olefin copolymer (A)>
The method for producing the 4-methyl-1-pentene/α-olefin copolymer (A) is not particularly limited. α-olefin leading to structural unit (ii)” in the presence of a suitable polymerization catalyst.

Here, as the polymerization catalyst that can be used in the present invention, conventionally known catalysts, such as magnesium-supported titanium catalyst, WO 01/53369 pamphlet, WO 01/27124 pamphlet, and JP-A-3-193796 Metallocene catalysts described in publications or JP-A-02-41303, International Publication No. 2011/055803, International Publication No. 2014/050817, etc. are preferably used.

<Thermoplastic elastomer (B)>
The thermoplastic elastomer used in the present invention is a polymer that exhibits thermoplastic properties when heated above its melting point, while exhibiting rubber elastic properties at room temperature. Specific examples of the thermoplastic elastomer (B) include the following polyolefin elastomer (B-1) and polystyrene elastomer (B-2).

≪Olefin elastomer (B-1)≫
The first embodiment of the olefinic elastomer (B-1) includes one selected from the group consisting of polyethylene and polypropylene, and polybutadiene, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, polyisobutylene, and α-olefin. A copolymer with one selected from the group consisting of: The form of copolymerization may be either block copolymerization or graft copolymerization, but only in the case of a copolymer consisting of one selected from the group consisting of polyethylene and polypropylene and an α-olefin, the form of copolymerization is random copolymerization. It may also be polymerization. The α-olefin is an olefin having a double bond at one end of its molecular chain, 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 exhibiting amorphous property as a soft part can be mentioned. Examples include crystalline), ethylene, butylene, and olefin block copolymers, polypropylene, polyolefin (amorphous), and polypropylene block copolymers. Specific examples include the product name DYNARON (registered trademark) from JSR Corporation, the product name Tafmer (registered trademark) and Notio (registered trademark) from Mitsui Chemicals, and the product name ENGAGE from Dow Chemical Co., Ltd. (registered trademark), VERSIFY (registered trademark), and those commercially available from ExxonMobil Chemical Corporation under the trade name Vistamaxx (registered trademark).

The second embodiment of the polyolefin elastomer in the present invention includes one selected from the group consisting of polyethylene and polypropylene, ethylene/propylene copolymer, ethylene/propylene/diene copolymer, ethylene/butene copolymer, Examples include blends with one selected from the group consisting of hydrogenated styrene butadiene. At this time, the ethylene/propylene copolymer, ethylene/propylene/diene copolymer, or ethylene/butene copolymer may be partially or completely crosslinked.

Specific examples include the product name Milastomer (registered trademark) from Mitsui Chemicals, the product name Esporex (registered trademark) from Sumitomo Chemical, and the product names Thermolan (registered trademark) and Xelas (registered trademark) from Mitsubishi Chemical Corporation. (registered trademark), and those commercially available from ExxonMobil Chemical Company under the trade name Santoprene (registered trademark).

Further, the olefin elastomer according to the present invention includes at least one type selected from the group consisting of acid anhydride groups, carboxyl groups, amino groups, imino groups, alkoxysilyl groups, silanol groups, silyl ether groups, hydroxyl groups, and epoxy groups. may be modified with a functional group.

≪Styrenic elastomer (B-2)≫
The styrene elastomer (B-2) is a block copolymer (SBS) of a polystyrene block as a hard part (crystal part) and a diene monomer block as a soft part, a hydrogenated styrene/butadiene/styrene block copolymer, etc. Polymer (HSBR), styrene/ethylene/propylene/styrene block copolymer (SEPS), styrene/ethylene/butene/styrene block copolymer (SEBS), styrene/isoprene/styrene block copolymer (SIS), styrene - Examples include isobutylene-styrene copolymer (SIBS) and styrene-isobutylene copolymer (SIB). Styrenic elastomers may be used singly or in combination of two or more.

Specific examples of the hydrogenated styrene-butadiene-styrene block copolymer include those commercially available from JSR Corporation under the trade name Dynalon (registered trademark). The styrene/ethylene/propylene/styrene block copolymer is obtained by hydrogenating a styrene/isoprene/styrene block copolymer (SIS). Specific examples of SIS include JSR Corporation's product name: JSR SIS (registered trademark), Kuraray Co., Ltd.'s product name: Hybler (registered trademark), and Shell Co., Ltd.'s product name: Clayton D (registered trademark). Examples include those that are commercially available.

Further, specific examples of SEPS include those commercially available from Kuraray Co., Ltd. under the trade name: Septon (registered trademark) or from Shell Co., Ltd. under the trade name: Clayton (registered trademark).

Further, specific examples of SEBS include those commercially available from Asahi Kasei Corporation under the trade name: Tuftec (registered trademark) or from Shell Co., Ltd. under the trade name: Clayton (registered trademark).

Further, specific examples of SIB and SIBS include those commercially available from Kaneka Corporation under the trade name: SIBSTAR (registered trademark).
In the friction body resin composition (X1), the total amount of the 4-methyl-1-pentene/α-olefin copolymer (A), the thermoplastic elastomer (B), and the crystalline polyolefin (C) is 100 parts by mass. Then, from the viewpoint of flexibility and stress relaxation properties, the upper limit of the content of the copolymer (A) in the composition is usually 50 parts by mass, preferably 48 parts by mass, more preferably 45 parts by mass, and particularly preferably The lower limit is usually 20 parts by weight, preferably 25 parts by weight, and more preferably 30 parts by weight.

The lower limit of the content of the thermoplastic elastomer (B) is usually 20 parts by mass, preferably 25 parts by mass, more preferably 30 parts by mass, and the upper limit is usually 80 parts by mass, preferably 75 parts by mass, even more preferably is 70 parts by weight, particularly preferably 65 parts by weight.

The lower limit of the content of crystalline polyolefin (C) is usually 5 parts by weight, preferably 7 parts by weight, more preferably 10 parts by weight, and the upper limit is 40 parts by weight, preferably 35 parts by weight, and Preferably it is 30 parts by mass.

<Crystalline polyolefin (C)>
The friction body composition (X) of the present invention may contain a crystalline polyolefin (C). The crystalline polyolefin (C) includes conventionally known low-density, medium-density, high-density polyethylene, high-pressure low-density polyethylene, isotactic polypropylene, syndiotactic polypropylene, poly-1-butene, poly-4-methyl-1 -Pentene, poly-3-methyl-1-butene, ethylene/α-olefin copolymer, propylene/α-olefin copolymer, 1-butene/α-olefin copolymer, cyclic olefin copolymer, chlorinated polyolefin Examples include.
When the amount of crystalline polyolefin (C) is within the above range, it is possible to impart appropriate hardness to the resulting friction body and contribute to erasability.

<Additives>
The friction body resin composition (X) of the present invention may be subjected to various modifications by adding secondary additives. Specific examples of secondary additives include plasticizers, ultraviolet absorbers, infrared absorbers, optical brighteners, mold release agents, antibacterial agents, nucleating agents, heat stabilizers, antioxidants, slip agents, and antistatic agents. agents, color inhibitors, conditioners, matting agents, antifoaming agents, preservatives, gelling agents, latex, fillers, inks, colorants, dyes, pigments, fragrances, and the like, but are not limited to these. These secondary additives may be used alone or in combination.

Examples of plasticizers include aromatic carboxylic acid esters (dibutyl phthalate, etc.), aliphatic carboxylic acid esters (methyl acetyl ricinoleate, etc.), aliphatic dialboxylic acid esters (adipic acid-propylene glycol polyester, etc.), aliphatic tricarboxylic acids. Examples include esters (triethyl citrate, etc.), phosphoric triesters (triphenyl phosphate, etc.), epoxy fatty acid esters (epoxybutyl stearate, etc.), petroleum resins, and the like.

Examples of mold release agents include lower (C1-4) alcohol esters of higher fatty acids (butyl stearate, etc.), polyhydric alcohol esters (C4-30) of fatty acids (hydrogenated castor oil, etc.), glycol esters of fatty acids, liquid paraffin, etc. can be mentioned.

Examples of antioxidants include phenolics (2,6-di-t-butyl-4-methylphenol, etc.), polycyclic phenols (2,2'-methylenebis(4-methyl-6-t-butylphenol), etc.) , phosphorus-based (tetrakis(2,4-di-t-butylphenyl)-4,4-biphenylene diphosphonate, etc.), and amine-based (N,N-diisopropyl-p-phenylenediamine, etc.) antioxidants. Can be mentioned.

Examples of the ultraviolet absorbing agent include benzotriazole-based, benzophenone-based, salicylic acid-based, and acrylate-based agents.
Examples of the antibacterial agent include quaternary ammonium salts, pyridine compounds, organic acids, organic acid esters, halogenated phenols, and organic iodines.

Surfactants include nonionic, anionic, cationic or amphoteric surfactants. Examples of 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, polypropylene glycol ethylene oxide adducts, polyethylene oxide, and fatty acid esters of glycerin. , fatty acid esters of pentaerythritol, fatty acid esters of sorbitol or sorbitan, alkyl ethers of polyhydric alcohols, aliphatic amides of alkanolamines, and other polyhydric alcohol-type nonionic surfactants.As anionic surfactants, For example, sulfate ester salts such as alkali metal salts of higher fatty acids, sulfonates such as alkylbenzene sulfonates, alkyl sulfonates, and paraffin sulfonates, phosphate ester salts such as higher alcohol phosphate ester salts, etc. Examples of the cationic surfactants include quaternary ammonium salts such as alkyltrimethylammonium salts. Examples of the amphoteric surfactant include amino acid type double-sided surfactants such as higher alkylaminopropionates, betaine type amphoteric surfactants such as higher alkyl dimethyl betaine, and higher alkyl hydroxyethyl betaine.

Examples of the antistatic agent include the above-mentioned surfactants, fatty acid esters, and polymeric antistatic agents. Examples of fatty acid esters include stearic acid and oleic acid esters, and examples of polymer antistatic agents include polyether ester amide.

Examples of pigments include inorganic pigments (titanium oxide, iron oxide, chromium oxide, cadmium sulfide, etc.) and organic pigments (azo lake type, thioindigo type, phthalocyanine type, anthraquinone type). Examples of dyes include azo dyes, anthraquinone dyes, and triphenylmethane dyes. The amount of these pigments and dyes added is not particularly limited, but the total amount is usually 5 parts by weight or less, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the copolymer (A).

Slip agents include waxes (carnauba wax, etc.), higher fatty acids (stearic acid, etc.), training fatty acid salts (calcium stearate, etc.), higher alcohols (stearyl alcohol, etc.), higher fatty acid amides (stearic acid amide, erucic acid amide, etc.) etc.

The amount of the various additives mentioned above is not particularly limited depending on the application as long as it does not impair the purpose of the present invention. The amount is preferably 0.01 to 30 parts by mass, respectively.

<Method for producing resin composition for friction body (X)>
The method for producing the resin composition (X) for friction bodies of the present invention is not particularly limited, and, for example, conventionally known production methods can be used. It is also possible to manufacture a composition by uniformly mixing a solution of each component dissolved in a solvent and then removing the solvent, but this method does not require steps such as dissolving raw materials in a solvent and removing the solvent, making it a practical method of manufacturing. It is preferable to employ a melt-kneading method in which a composition is produced by melt-kneading each component. There are no particular restrictions on the melt-kneading method; for example, a commonly used known mixer such as a kneader, roll mill, Banbury mixer, single-screw or twin-screw extruder, etc. may be used to melt-knead the mixture at 180 to 250°C. After smelting, a method of granulation or pulverization can be adopted. Among them, from the viewpoint of mixability and productivity, it is preferable to use a twin-screw extruder. By this method, high quality resin composition pellets in which each component and additive are uniformly dispersed and mixed can be obtained.

<Friction body>
The friction body of the present invention is characterized by containing the friction body resin composition (X). The friction body of the present invention can be suitably produced by injection molding from the friction body resin composition (X), for example, although there is no particular restriction on the method for producing the friction body.

The friction body, like conventional friction bodies, is used to erase or change the color of handwriting by rubbing the handwriting made with thermochromic ink using frictional heat. In this case, the friction body of the present invention acts as an elastic body to generate frictional heat, and also acts as a viscous body to obtain adsorption and peeling performance. It also has the ability to erase objects.

By using the friction body, even if the ink is of a new composition, the ink can be erased without breaking due to rubbing against the paper, and there is no residual color left on the ink or its surroundings during erasure, which impairs the appearance. This results in a writing instrument and writing set that are highly convenient and practical, and can ensure sufficient erasability of handwriting. In this case, the friction body of the present invention can be formed from a single member, just like the friction body provided on the main body of a conventional writing instrument, so that the exterior of the writing instrument can be used as is, making it highly versatile. In addition, since the friction body can exert a similar effect to a conventional eraser, it can also peel graphite from the paper surface, for example. Therefore, the friction body of the present invention can be used to form a new eraser that allows the thermochromic ink to be thermally discolored and the handwriting to be removed with a pencil lead, mechanical pencil lead, etc., all with a single friction body.

<Writing implement having friction body composition>
The frictional body composition and the frictional body are configured in a form capable of rubbing handwriting and are used for practical purposes. In this case, the frictional body may be configured independently, or may be configured in a form capable of being held, such as by being attached to another member such as a hard resin in such a form that the frictional part can contact handwriting (paper surface). In addition, the frictional body may be configured as a thermochromic writing instrument provided in a writing instrument having thermochromic ink built in, or as a writing instrument having a thermochromic ink built in as a separate body. For example, the writing instrument of the present invention includes a writing instrument body and the frictional body attached to the writing instrument body, and the thermochromic ink is built in the writing instrument body.

Forms of the writing instruments include fountain pens, marking pens, ballpoint pens, retractable solid writing instruments, etc. In addition to cap-type forms with a cap that covers the pen tip, there are also knock-type, rotary-type, sliding-type, etc. It may be of a retractable type that has a retractable mechanism and can accommodate the pen tip within the barrel. In the case of a refill type, it is possible to use not only a type that accommodates one refill, but also a multiple type that accommodates two or more refills and allows a desired refill to selectively appear and retract. Further, it may be a double-ended type in which pen nibs of different shapes or pen nibs that produce ink of different hues are attached.

As a marking pen, for example, a marking pen nib such as a fiber tip, felt tip, plastic tip, metal tip, etc. is attached to the writing tip, and an ink storage body made of a fiber bundle housed inside the barrel is impregnated with ink. A structure that stores ink directly inside the barrel and supplies a predetermined amount of ink to the writing tip by interposing a comb-shaped ink flow rate adjustment member or an ink flow rate adjustment member made of fiber bundles. Examples include a marking pen that has a structure that supplies ink, and a structure that stores ink directly inside the barrel and supplies a predetermined amount of ink to the writing tip using a valve mechanism.

A ballpoint pen, for example, has an ink storage tube filled with an ink composition in its barrel, and the ink storage tube communicates with a tip with a ball attached to the tip, and furthermore, an ink backflow is provided on the end surface of the ink. A structure in which the preventer is in close contact with the tip, the tip is connected to the tip of the barrel, and the ink composition is directly filled into the barrel, and an ink backflow preventer is in close contact with the end face of the ink, and the tip is housed inside the barrel. A structure in which an ink absorbing body made of fiber bundles is impregnated with ink to supply ink to the chips, and a predetermined amount of ink is supplied to the chips by interposing a comb-shaped ink flow rate adjustment member and an ink flow rate adjustment member made of fiber bundles. An example of such a structure is a ballpoint pen. Further, a ballpoint pen having a structure in which the tip is connected to the tip of the barrel and ink is directly filled may have a structure in which a transfer layer is formed on the ink-filled exterior and then housed in the transparent outer barrel.

As the ink contained in the writing instrument, in addition to being able to accommodate normal non-color-changing ink, conventional general-purpose thermochromic ink that can be erased or changed color by heating can be used.
The thermochromic area that is rubbed by the friction tool of the present invention includes not only handwriting formed on paper with the thermochromic writing instrument, but also the impression of a stamp, and the thermochromic layer formed by printing or painting (image form or solid shape). ) shall apply.

<Thermochromic writing instruments>
The thermochromic writing instrument equipped with the friction body may be of any form, regardless of water-based ink or oil-based ink, as long as it contains thermochromic ink and can form thermochromic handwriting. good. Note that the thermochromic ink according to the present invention is a general term for materials that form handwriting, and also includes forms such as pencil lead. Details will be explained below.

As the thermochromic ink contained in the writing instrument, any ink that can be erased or changed in color by heating can be used. As the colorant to be mixed in the ink, a reversible thermochromic composition containing at least the three essential components of an electron donating color-forming organic compound, an electron accepting compound, and a reaction medium that determines the temperature at which the color reaction between the two occurs is preferably used. In particular, a microencapsulated pigment in which a reversible thermochromic composition is encapsulated in a microcapsule is effective.

The reversible thermochromic composition has a temperature that changes at a predetermined temperature (color change point) as described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-29398, etc. It changes color before and after, exhibits a decolored state in a temperature range above the high temperature side discoloration point, and a colored state in a temperature range below the low temperature side discoloration point, and of the above two states, only one specific state exists in the normal temperature range, The other state is maintained as long as the heat or cold required to bring it about is applied, but when the heat or cold is no longer applied, it returns to the state it exhibits at room temperature, with a hysteresis width. A reversible thermochromic composition having relatively small characteristics (ΔH of 1° C. or more and 7° C. or less) can be exemplified, and a heat-decolorable microcapsule pigment in which this composition is encapsulated in microcapsules can be applied.

Furthermore, as the reversible thermochromic composition, relatively large compositions described in JP-A-4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936, etc. Those exhibiting hysteresis characteristics (ΔH value of 8°C or higher and 50°C or lower), JP-A No. 2006-137886, JP-A No. 2006-188660, JP-A No. 2008-45062, JP-A No. 2008-280523, etc. Examples include those exhibiting large hysteresis characteristics as described in . When the hysteresis characteristic is large, the shape of the curve plotting the change in coloring density due to temperature change is such that the shape of the curve is such that the temperature increases from the lower side than the discoloration temperature range, and vice versa. This means that discoloration follows very different routes depending on the situation. Such a reversible thermochromic composition has a coloring state in a low temperature range below the complete coloring temperature, or a discoloring state in a high temperature range above the complete coloring temperature, and has color memory in a specific temperature range, A heat-decolorable microcapsule pigment containing this pigment can also be applied.

Specifically, the reversible thermochromic composition having color memory properties has a complete coloring temperature that can only be obtained in a freezing room, a cold region, etc., that is, -50°C or more and 0°C or less, preferably -40°C. ℃ or more and -5℃ or less, more preferably -30℃ or more and -10℃ or less, and the temperature at which a complete color erasure temperature can be obtained by the frictional heat of the friction body, that is, 50℃ or more and 95℃ or less, preferably 50℃ or more and 90℃ or more. By specifying the temperature within the range of ℃ or lower, more preferably 60℃ or higher and 80℃ or lower, and specifying the ΔH value within the range of 40℃ or higher and 100℃ or lower, it effectively functions to maintain the color that appears under normal conditions (daily living temperature range). I can list things that can be done.

When using microcapsule pigments, the average particle diameter is, for example, in the range of 0.05 μm or more and 5.0 μm or less, preferably 0.1 μm or more and 4.0 μm or less, and more preferably 0.5 μm or more and 3.0 μm or less. This is preferable in terms of 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 diameter of the microcapsule pigment is set to 2.0 μm or more, chemical decolorization using frictional heat is performed. This makes it possible to erase (discolor) using physical erasure by adsorption and peeling, which is highly effective for irreversible erasure and discoloration. In addition, the average particle diameter is determined by determining the area of the particle using the image analysis particle size distribution measurement software "Macview" manufactured by Mountech, and calculating the projected area circle equivalent diameter (Heywood diameter) from the area of the particle area. , is the value measured as the average particle diameter of particles equivalent to a sphere with equal volume.

In addition, if the particle diameter of all or most of the particles exceeds 0.2 μm, use a particle size distribution analyzer (manufactured by Beckman Coulter Co., Ltd., product name: Multisizer 4e) to measure the equivalent volume of an equal volume sphere by the Coulter method. It is also possible to measure the average particle size as the average particle size of the particles. Further, as a colorant component, dyes, general pigments, etc. can be used in order to impart a desired hue to the handwriting without thermal discoloration. For example, as the dye, acid dyes, basic dyes, direct dyes, etc. 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, and dispersed pigment products that are finely and stably dispersed in a medium using surfactants etc. is used. In addition, metallic luster pigments such as metal powder and pearl pigments, fluorescent pigments, phosphorescent pigments, and special pigments such as titanium dioxide can also be applied. Incidentally, these coloring components may be used in combination with the above-mentioned microcapsule pigment, or can be encapsulated in the above-mentioned microcapsule pigment.

In particular, when a metallic luster pigment is added to a thermochromic ink, a metallic-like ink can be formed, so that when writing, a glossy and highly decorative handwriting is formed, making it more useful. Furthermore, when the thermochromic microcapsule pigment described above is used as a coloring agent, the handwriting on the white paper obtained when the thermochromic microcapsule pigment becomes transparent has no glitter and appears to have been completely erased. Transparent metallic luster pigments are useful because they are visually visible.

When erasing the handwriting, it is necessary to perform thermal discoloration and exfoliation removal, so conventionally it has been necessary to use two types of friction bodies: a friction body made of an elastic body with a high Shore hardness, and an elastic body or eraser with a low Shore hardness. Ta. However, with the friction body of the present invention, discoloration (discoloration) due to frictional heat and adsorption and peeling can be achieved by one friction using one friction body, making it particularly convenient. In particular, when the average particle diameter of the metallic luster pigment used is 10 μm or more, highly glittering handwriting can be obtained, and the adsorption and releasability is also high, so it is highly effective in handwriting decoration and irreversible erasability. Demonstrate.

The transparent metallic luster pigment is a glitter pigment in which the core material is a material selected from natural mica, synthetic mica, flat glass pieces, flaky aluminum oxide, etc., and the core material is coated with a metal oxide, or a cholesteric liquid crystal glitter pigment. Examples include pigments.

Effective bright pigments whose core material is natural mica include 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.Specifically, , the trade name "Iriodin" manufactured by Merck & Co., and the trade name "Lumina Colors" manufactured by Engelhard. Bright pigments whose core material is synthetic mica are effective if their surfaces are coated with metal oxides such as titanium oxide. Examples of metal oxides include metal oxides such as titanium, zirconium, chromium, vanadium, and iron. Examples thereof include metal oxides containing titanium oxide as a main component. Specifically, the product name "Ultimica" manufactured by Nihon Koken Kogyo Co., Ltd. can be exemplified. Bright pigments whose core material is flat glass pieces are those whose surfaces are coated with metal oxides such as titanium oxide. Specifically, the product name "Metashine" manufactured by Nippon Sheet Glass Co., Ltd. is effective. etc. can be exemplified.

Bright pigments whose core material is flaky aluminum oxide are effective if their surfaces are coated with metal oxides such as titanium oxide.Metal oxides include metals such as titanium, zirconium, chromium, vanadium, and iron. Examples include oxides, preferably metal oxides containing titanium oxide as a main component. Specifically, the product name "Ciralic" manufactured by Merck & Co., Ltd. can be exemplified. Liquid crystal polymers used as cholesteric liquid crystal glitter pigments have the property of reflecting only a part of the incident light over a wide spectral range due to the light interference effect, and transmitting all other light. It has excellent metallic luster and a color flop property where the hue changes depending on the viewpoint. It also has transparency. A specific example of the cholesteric liquid crystal glitter pigment is "Helicone HC" (trade name) manufactured by Wacker Chemie. Further, as a glittering material in which a metal such as gold or silver is vacuum-deposited onto a film, the foil is peeled off, and the film is finely pulverized, the product name "ELG neo" manufactured by Oike Kogyo Co., Ltd. can be exemplified.

The metallic luster pigment preferably has an average particle diameter of 0.1 μm or more and 50 μm or less, preferably 2 μm or more and 40 μm or less, and more preferably 10 μm or more and 40 μm or less, from the viewpoint of writing performance and brightness. The average particle size is measured using a laser diffraction/scattering particle size distribution analyzer (LA-300, manufactured by Horiba, Ltd.), and based on the measured value, the average particle size is determined by volume. Calculate the diameter (median diameter).

In particular, those having an average particle diameter of 10 μm or more have extremely high brightness, but are difficult to penetrate into the paper surface during writing. Therefore, when rubbed with a conventional friction body made of an elastic body, the metallic luster pigment tends to scatter, and depending on the viewing angle, the metallic luster pigment scattered over the entire rubbed area may be visible, spoiling the appearance. In particular, on black paper, the high brightness is emphasized, resulting in an even worse appearance. On the other hand, by rubbing with a friction body made of a viscoelastic material, it becomes possible to adsorb the metallic luster pigment, and it is possible to peel it off without scattering it on the scratched area, thereby making it possible to cleanly erase handwriting. Therefore, handwriting made with metallic luster thermochromic ink can be erased (discolored) using chemical erasure using frictional heat and physical erasure using adsorption and peeling, so irreversible erasure and discoloration can be avoided. Particularly effective.

Various other additives can also be added to the thermochromic ink as necessary. For water-based inks, conventionally applied agents such as pH adjusters, rust preventives, preservatives or anti-mold agents, wetting agents, antifoaming agents, surfactants, lubricants, fixing agents such as resins, shear reduction agents, etc. A tackifying agent, a nib drying prevention agent, a sag prevention agent, etc. can be added. In addition, if it is an oil-based ink, conventionally applied viscosity modifiers, preservatives, rust preventive agents, antifoaming agents, lubricants, dispersants, anti-staining agents, anti-leakage agents, surfactants, etc. are added. can do.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, various physical properties in Examples and Comparative Examples were measured by the following methods.

〔composition〕
The content (mol%) of each structural unit (4-methyl-1-pentene (4MP1) and α-olefin (AO)) in the 4-methyl-1-pentene/α-olefin copolymer (A) is Measured by ¹³ C-NMR.
・Measurement device: Nuclear magnetic resonance device (ECP500 type, manufactured by JEOL Ltd.)
・Observation nucleus: ^13C (125MHz)
・Sequence: Single pulse proton decoupling ・Pulse width: 4.7 μs (45° pulse)
・Repetition time: 5.5 seconds ・Number of integration: 10,000 times or more ・Solvent: Orthodichlorobenzene/deuterated benzene (volume ratio: 80/20) mixed solvent ・Sample concentration: 55 mg/0.6 mL
・Measurement temperature: 120℃
・Chemical shift standard value: 27.50ppm

[Intrinsic viscosity [η]]
The intrinsic viscosity [η] of the copolymer was measured at 135° C. in a decalin solvent using an Ubbelohde viscometer as a measuring device.
After about 20 mg of the specific 4MP1 copolymer is dissolved in 25 ml of decalin, the specific viscosity η _sp is measured in an oil bath at 135° C. using an Ubbelohde viscometer. After diluting this decalin solution by adding 5 ml of decalin, the specific viscosity η _sp is measured in the same manner as above. This dilution operation is repeated two more times, and the value of ηsp/C when the concentration (C) is extrapolated to 0 is determined as the intrinsic viscosity [η] (unit: dl/g) (see Equation 1 below).
[η]=lim(ηsp/C) (C→0)...Formula 1

[Weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn)]
The weight average molecular weight (Mw) of the copolymer and the molecular weight distribution (Mw/Mn) expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) are determined by gel permeation chromatography (GPC). Calculated by standard polystyrene conversion method using Permeation Chromatography).

-conditions-
Measuring device: GPC (ALC/GPC 150-C plus type, suggested refractometer detector integrated, manufactured by Waters)
Column: 2 GMH6-HT (manufactured by Tosoh Corporation) and 2 GMH6-HTL (manufactured by Tosoh Corporation) connected in series Eluent: o-dichlorobenzene Column temperature: 140°C
Flow rate: 1.0mL/min

[Melt flow rate (MFR)]
Melt Flow Rate (MFR) was measured at 230° C. under a load of 2.16 kg in accordance with ASTM D1238. The unit is g/10min.

〔density〕
The density of the copolymer was measured in accordance with JIS K7112 (density gradient tube method). This density (kg/m ³ ) was used as an index of lightness.

[Melting point (Tm)]
The melting point (Tm) of the copolymer was measured using a differential scanning calorimeter (Model DSC220C, manufactured by Seiko Instruments Inc.) as a measuring device. Approximately 5 mg of polymer is sealed in an aluminum measuring pan and heated from room temperature to 200°C at 10°C/min. To completely melt the polymer, hold at 200°C for 5 minutes and then cool to -50°C at 10°C/min. After leaving it at -50°C for 5 minutes, it is heated a second time to 200°C at 10°C/min, and the peak temperature (°C) at this second heating is taken as the melting point (Tm) of the polymer. Note that when multiple peaks are detected, the peak detected on the highest temperature side is adopted.

[Dynamic viscoelasticity]
In measuring the dynamic viscoelasticity of the copolymer and resin composition, the temperature dependence of the dynamic viscoelasticity from -40 to 150°C was measured at a frequency of 10 rad/s using MCR301 manufactured by ANTON Paar. The temperature at which the loss tangent (tan δ) due to the glass transition temperature reaches its peak value (maximum value) in the range of ~40°C (hereinafter also referred to as "peak value temperature"), and the loss tangent (tan δ) at that time The value of was measured.

[Shore A hardness]
In the measurement of Shore A hardness, three sheets with a thickness of 2 mm obtained in the Examples and Comparative Examples were stacked and used as a measurement sample, and the value was read immediately after the needle was pushed in accordance with JIS K6253, and the value was read in that state for 15 seconds. I read the numbers when I let it stand still. In addition, the change in Shore A hardness ΔHS was calculated using the following formula.
ΔHS = (Shore A hardness value immediately after the start of indenter contact - Shore A hardness value 15 seconds after indenter contact)

[Wear resistance evaluation]
In the measurement of abrasion, the 2 mm thick sheets obtained in the examples and comparative examples were cut into 5 mm x 5 mm pieces to be used as measurement samples, and the measurement samples were attached to the abrasion fixture of a Gakushin abrasion tester (Tribogear Type 30S) manufactured by Shinto Scientific Co., Ltd., and in a state where the friction body was in contact with copy paper (PPC Paper Type Fw), a predetermined load was applied and the friction body was reciprocated a predetermined number of times (200 times or 500 times) over a width of 100 mm at a test speed of 7500 mm/min. The test was performed under two conditions: 200 times at 23°C with a load of 2 kg, and 500 times at 40°C with a load of 1 kg. The mass obtained by subtracting the mass of the measurement sample after the measurement from the mass of the measurement sample before the measurement was calculated as the wear amount of the friction body.

[Pencil and ballpoint pen erasability test]
Using a commercially available ballpoint pen and a commercially available pencil (Tombow Pencil Co., Ltd., 8900-B), ten spiral circles were handwritten in succession on writing paper A (white paper), and the handwritten marks were rubbed with a friction body to erase them, and the state of the marks was visually confirmed. The evaluation of the test results is shown in Table 2.
A: Thermochromic marks or graphite marks were erased without leaving any residual color.
B: Thermochromic marks or graphite marks remained faintly, and the graphite scattered and stained the area around the marks.
C: Thermochromic marks or graphite marks were not erased at all.

[Occurrence of erased residue]
Using a commercially available ballpoint pen and a commercially available pencil (manufactured by Tombow Pencil, 8900-B), 10 consecutive spiral circles were handwritten on writing paper A (blank paper), and then the handwriting was rubbed with a friction body. After rubbing, it was confirmed whether eraser scum (eraser debris) was generated from the friction body. Evaluation of the test results is listed in Table 2.
A: No generation of eraser residue was observed, and there was no problem in practical use.
B: The surface of the friction body was peeled off, a small amount of erasing scum was generated, and the erasing scum adhered to the friction body, but there was no problem in practical use.
C: A large amount of eraser residue was generated, causing a practical problem.

<Synthesis Example 1>
<Synthesis of 4-methyl-1-pentene/α-olefin copolymer (A-1)>
A 1.5-liter SUS autoclave equipped with an agitator and thoroughly purged with nitrogen was charged with 300 ml of normal hexane (dried over activated alumina in a dry nitrogen atmosphere) and 450 ml of 4-methyl-1-pentene at 23° C. 0.75 ml of a 1.0 mmol/ml toluene solution of triisobutylaluminum (TIBAL) was added to the autoclave and stirred.

Next, the autoclave was heated to an internal temperature of 60° C. and pressurized with propylene so that the total pressure was 0.19 MPa (gauge pressure). Subsequently, 1 mmol of methylaluminoxane prepared in advance in terms of Al was added to diphenylmethylene (1-ethyl-3-t-butyl-cyclopentadienyl) (2,7-di-t-butyl-fluorenyl) zirconium dichloride. 0.34 ml of a toluene solution containing 0.01 mmol of was pressurized with nitrogen into the autoclave to start polymerization. During the polymerization reaction, the temperature was adjusted so that the internal temperature of the autoclave was 60°C. 60 minutes after starting the polymerization, 5 ml of methanol was pressurized with nitrogen into the autoclave to stop the polymerization, and the autoclave was depressurized to atmospheric pressure. Then, acetone was poured into the reaction solution with stirring.

The obtained powder-like polymer containing the solvent was dried at 100° C. under reduced pressure for 12 hours. The weight of the obtained 4-methyl-1-pentene/α-olefin copolymer (A-1) (hereinafter also referred to as copolymer (A-1)) was 44.0 g. The -1-pentene content was 84.1 mol%, and the propylene content was 15.9 mol%. When measured by DSC, the melting point was 132°C. Table 1 shows the measurement results of various physical properties of the obtained copolymer (A-1).

<Synthesis of 4-methyl-1-pentene/α-olefin copolymer (a-1)>
300 ml of n-hexane (dried on activated alumina in a dry nitrogen atmosphere) and 450 ml of 4-methyl-1-pentene were placed in a 1.5 L SUS autoclave equipped with stirring blades and sufficiently purged with nitrogen. It was charged at 23°C. This autoclave was charged with 0.75 ml of a 1.0 mmol/ml toluene solution of triisobutylaluminum (TIBAL), and the stirrer was turned.

Next, the autoclave was heated until the internal temperature reached 60° C., and pressurized with propylene to a total pressure (gauge pressure) of 0.40 MPa.
Next, 0.34 ml of a toluene solution containing 1 mmol of methylaluminoxane and 0.01 mmol of diphenylmethylene(1-ethyl-3-t-butyl-cyclopentadienyl)(2,7-di-t-butyl-fluorenyl)zirconium dichloride, which had been previously prepared, was pressurized into the autoclave with nitrogen to initiate the polymerization reaction. During the polymerization reaction, the internal temperature of the autoclave was adjusted to 60° C.

60 minutes after the start of polymerization, 5 ml of methanol was pressurized into the autoclave with nitrogen to stop the polymerization reaction, and then the pressure inside the autoclave was depressurized to atmospheric pressure. After depressurizing, acetone was added to the reaction solution while stirring it to obtain a polymerization reaction product containing a solvent.

Next, the obtained polymerization reaction product containing the solvent was dried at 100° C. for 12 hours under reduced pressure to obtain 36.9 g of powdered 4-methyl-1-pentene/α-olefin copolymer (a-1 ) (hereinafter also referred to as copolymer (a-1)) was obtained. Table 1 shows the measurement results of various physical properties of the obtained copolymer (a-1).

The content of 4-methyl-1-pentene in copolymer (a-1) was 72.5 mol%, and the content of propylene was 27.5 mol%. When measured by DSC, no melting point (Tm) was observed.

<Thermoplastic elastomer (B)>
The following thermoplastic elastomer (B) was used.
Thermoplastic elastomer (B-1): Milastomer manufactured by Mitsui Chemicals, Inc. (brand: 8030NS)
Thermoplastic elastomer (B-2): Milastomer manufactured by Mitsui Chemicals, Inc. (brand: 5030NS)
Thermoplastic elastomer (B-3): Milastomer manufactured by Mitsui Chemicals, Inc. (brand: 7030NS)
Thermoplastic elastomer (B-4): Tuftec manufactured by Asahi Kasei Corporation (brand name: H1221)

<Crystalline polyolefin (C)
The following crystalline polyolefin (C) was used.

Polyolefin (C-1): Evolu manufactured by Prime Polymer Co., Ltd. (Brand: SP4030)
Polyolefin (C-2): Prime Polypro (brand name: J-2000GP) manufactured by Prime Polymer Co., Ltd.

<Example 1>
40 parts by mass of 4-methyl-1-pentene/α-olefin copolymer (A-1) and 60 parts by mass of thermoplastic elastomer (B-2) were mixed to form a heat-resistant secondary antioxidant. 0.2 parts by mass of n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propinate as a stabilizer was blended. After that, using a twin screw extruder BT-30 (screw system 30 mmφ, L/D = 46) manufactured by Plastic Engineering Research Institute Co., Ltd., under the conditions of a set temperature of 230 ° C., a resin extrusion rate of 60 g/min, and 200 rpm. It was granulated and pelletized to obtain a resin composition. This resin composition was put into a hopper of an injection molding machine (manufactured by Toshiba Machinery Co., Ltd.). Then, the cylinder temperature was set to 230°C and the die temperature was set to 230°C, and a sheet of 120 x 120 x 2 mm was molded. Table 2 shows the results of evaluating the physical properties of the obtained sheet and the results of evaluating the erasability of the sheet cut into a size of 5 mm x 5 mm as a friction body.

<Example 2>
By the same method as Example 1 except that 40 parts by mass of thermoplastic elastomer (B-1) was used instead of thermoplastic elastomer (B-2) and 20 parts by mass of crystalline polyolefin (C-1) was used. The sheet and friction body of Example 2 were obtained. Table 2 shows the results of physical property evaluation of the obtained sheet and friction body.

<Example 3>
Performed except that 20 parts by mass of 4-methyl-1-pentene/α-olefin copolymer (A-1) and 80 parts by mass of plastic elastomer (B-3) were used instead of plastic elastomer (B-2). A sheet and friction body of Example 4 were obtained in the same manner as in Example 1. Table 2 shows the results of physical property evaluation of the obtained sheet and friction body.

<Example 4>
Performed except that 30 parts by mass of 4-methyl-1-pentene/α-olefin copolymer (A-1) and 70 parts by mass of plastic elastomer (B-3) were used instead of plastic elastomer (B-2). A sheet and friction body of Example 5 were obtained in the same manner as in Example 1. Table 2 shows the results of physical property evaluation of the obtained sheet and friction body.

<Comparative example 1>
In place of the 4-methyl-1-pentene/α-olefin copolymer (A-1), 30 parts by mass of the 4-methyl-1-pentene/α-olefin copolymer (a-1) and the plastic elastomer (B A sheet and a friction body of Comparative Example 1 were obtained in the same manner as in Example 1 except that 70 parts by mass of the plastic elastomer (B-3) was used instead of -2). Table 2 shows the results of physical property evaluation of the obtained sheet and friction body.

<Comparative Example 2>
A sheet of Comparative Example 2 was obtained in the same manner as in Example 1 and the friction body, except that the 4-methyl-1-pentene/α-olefin copolymer (A-1) was not used, and 100 parts by mass of the thermoplastic elastomer (B-4) was used instead of the thermoplastic elastomer (B-2). The results of evaluating the physical properties of the obtained sheet and friction body are shown in Table 2. However, regarding the evaluation of abrasion properties, the paper broke during the test at 23° C., 2 kg load for 200 times, and the test at 40° C., 1 kg load for 500 times, and therefore the amount of abrasion could not be determined.

<Comparative example 3>
4-Methyl-1-pentene/α-olefin copolymer (A-1) is not used, 50 parts by mass of thermoplastic elastomer (B-4) is used instead of thermoplastic elastomer (B-2), and A sheet and friction body of Comparative Example 3 were obtained in the same manner as in Example 1 except that 50 parts by mass of crystalline polyolefin (C-2) was used. Table 2 shows the results of physical property evaluation of the obtained sheet and friction body. However, regarding abrasion evaluation, in 200 tests at 23° C. and a load of 2 kg, the amount of wear could not be determined because the paper broke during the test.

<Comparative example 4>
A comparative example was prepared in the same manner as in Example 1, except that 100 parts by mass of the 4-methyl-1-pentene/α-olefin copolymer (A-1) was used and the thermoplastic elastomer (B-2) was not used. A sheet and friction body of No. 4 were obtained. Table 2 shows the results of physical property evaluation of the obtained sheet and friction body.

From Table 2, the specific results of the erasability test show that by repeatedly rubbing handwriting, the friction material of the present invention exhibits the performance as a viscous material, and frictional heat is generated, making the thermochromic pigment transparent. I understand that. Furthermore, the results of the abrasion test show that it does not break even when rubbed, and the amount of wear is small. Therefore, it is thought that the handwriting was erased cleanly without contaminating the paper surface.

Claims (10)

Contains a 4-methyl-1-pentene/α-olefin copolymer (A) and a thermoplastic elastomer (B) that satisfy the following requirements (a) to (b), and the 4-methyl-1-pentene/α - A resin composition for a friction body (X) in which the mass ratio [(A)/(B)] of the olefin copolymer (A) and the thermoplastic elastomer (B) is 10/90 to 67/33.
Requirement (a) : The melting point (Tm) of the copolymer (A) is 110° C. or higher and 160° C. or lower when calorimetrically measured using a differential scanning calorimeter (DSC).
Requirement (b) ; Copolymer (A) is derived from structural unit (i) derived from 4-methyl-1-pentene and α-olefin (excluding 4-methyl-1-pentene). 82 to 90 mol% of the structural unit (i) and 10 to 90 mol% of the structural unit (ii), assuming the total of the structural unit (i) and the structural unit (ii) to be 100 mol%. 18 mol% , and the α-olefin is propylene . The resin composition (X) for a friction body according to claim 1, which satisfies the following requirements (x) and (y).
Requirement (x) ;
In accordance with JIS K6253, the Shore A hardness of the friction body resin composition (X) at 15 seconds after the start of contact with the indenter is 70 or more, as measured by stacking three sheets with a thickness of 2 mm. 95 or less.
Requirement (y) ;
In accordance with JIS K6253, the Shore A hardness of the friction body resin composition (X) is measured by stacking three sheets with a thickness of 2 mm, and is expressed by the following formula, immediately after contact with the indenter. The difference ΔHS between the Shore A hardness value at and the Shore A hardness value 15 seconds after contact with the indenter is 5 or more and 20 or less.
ΔHS = (Shore A hardness value immediately after contact with the indenter - Shore A hardness value 15 seconds after contact with the indenter) The resin composition (X) for a friction body according to claim 1 or 2, which satisfies the following requirement (z).
Requirement (z) ;
When a 2 mm thick sheet made of the friction body resin composition (X) was brought into contact with copy paper and reciprocated 200 times across a 100 mm width at a test speed of 7500 mm/min at 23°C and a load of 2 kg. The amount of wear is 0.11 mg or less, and the amount of wear when reciprocating 500 times at 40° C. and a load of 1 kg is 0.10 mg or less. The resin composition for a friction body according to any one of claims 1 to 3, wherein the 4-methyl-1-pentene/α-olefin copolymer (A) satisfies the following requirement (c): Thing (X).
Requirement (c) : The tan δ peak temperature obtained by performing dynamic viscoelasticity measurement at a frequency of 10 rad/s (1.6 Hz) in a temperature range of -40 to 150°C is 20°C or more and 45°C or less. The resin composition (X) for a friction body according to any one of claims 1 to 4, further comprising a crystalline polyolefin (C). A friction body comprising the friction body resin composition (X) according to any one of claims 1 to 5. The friction body according to claim 6, characterized in that it is produced by injection molding. Comprising a writing instrument main body and the friction body according to claim 6 or 7 attached to the writing instrument main body,
A writing instrument having thermochromic ink built into the writing instrument body. 9. The writing instrument according to claim 8, wherein the thermochromic ink contains a thermochromic microcapsule pigment having an average particle diameter of 0.05 μm or more and 5.0 μm or less. 9. The writing instrument according to claim 8 , wherein the thermochromic ink contains a metallic luster pigment having an average particle diameter of 0.1 μm or more and 50 μm or less.