JPWO2019117125A1 - Eraser - Google Patents

Abstract

The eraser (10) includes a base material (110) containing at least one of a resin component and an elastomer component and a plasticizer, and a porous foam (120) impregnated with the base material (110). ,including. The eraser (10) has a tensile modulus of 0.6 MPa or more and 1.2 MPa or less.

Description

  The present invention relates to eraser. This application claims priority based on Japanese Patent Application No. 2017-238080 filed on December 12, 2017, and incorporates all the contents described in the Japanese application.

  The eraser is generally called an eraser and is widely used. A general eraser is manufactured by blending a plasticizer, a filler, a coloring agent or the like as needed with a base resin such as a vinyl chloride resin, mixing them uniformly, and then heat molding. An example of such eraser is disclosed in Patent Document 1.

  Patent Literature 2 discloses a eraser including an elastic body of a eraser composition containing at least one of a rubber component and a resin component, and a skeletal structure.

JP-A-55-34990 JP 2001-138688 A

  For eraser, there is a need to selectively erase only characters in a desired narrow area so as not to erase surrounding characters. Further, there is a need to erase characters in such a narrow area accurately and neatly with a light force. In order to satisfy such needs, the eraser is designed to have a shape-retaining property in which even if the user applies force to erase the character to erase the character, the eraser itself is hardly bent and its shape is maintained. It is required to have the erasing ability which is the ability to erase.

  Therefore, an object of the present invention is to provide a eraser having both high shape retention and high erasure.

  The eraser according to the present invention includes a base material containing at least one of a resin component and an elastomer component, a plasticizer, and a porous foam impregnated with the base material. The eraser has a tensile modulus of 0.6 MPa or more and 1.2 MPa or less.

  In order to accurately erase a character at a desired position by eraser, it is important to maintain shape of eraser at the time of erase. When erasing a character written with a pencil on the paper by erasing, the eraser user rubs the paper by erasing the paper while applying pressure to the paper so that the eraser is pressed against the paper. Turn off. At this time, if the eraser does not have sufficient shape retention, the eraser bends due to the force applied by the user to the eraser. When the eraser is bent, the direction of the force applied to the eraser is dispersed, the force is not sufficiently transmitted, the frictional force on the paper surface is reduced, and the character is hardly erased. In addition, since the force applied to the eraser is dispersed by bending, an extra force needs to be applied to obtain a sufficient frictional force to erase the eraser.

  In addition, since the paper surface is hidden by the bending of the eraser, there is also a problem that the erased portion is difficult to see from the user, and it is difficult to erase a predetermined position. In addition, if the shape retention of the eraser is low, the followability of the movement of the ground contact portion with respect to the eraser paper surface with respect to the movement of the user's hand is deteriorated. As a result, the frictional force in the portion intended by the user may be insufficient and the characters may not be erased sufficiently, or may be erased to the portions not intended by the user. If the shape retention of the eraser is low as described above, there is a tendency that the usability of the eraser is deteriorated because the force is hardly transmitted at the time of erase and the erased portion is difficult to see.

  On the other hand, the eraser is required to have high eraseability as an essential property of the eraser. The mechanism by which a character is erased by eraser is as follows. When writing on paper with a pencil, graphite adheres to the surface of the paper. When this character is rubbed with a eraser, the eraser's texture is worn on the surface of the paper surface, and the graphite attached to the surface of the paper surface is adsorbed. A part of the eraser structure that has adsorbed graphite is detached from the eraser surface without being erased. The new eraser's tissue surface is exposed when the eraser detaches from the eraser surface. Characters disappear by repeating this cycle. Therefore, the eraser is required to have a wear-disintegrating property in which a portion rubbed by friction is detached while collapsing. High erasability is achieved by high wear collapse properties.

  However, it is not easy to combine high shape retention and high erasure. For example, to improve shape retention, it is conceivable to harden the eraser. However, if the hardness of the eraser is simply increased, the wear disintegration property tends to decrease, and as a result, the erase ability tends to decrease. Therefore, there has been a demand for a eraser having both high shape retention and high erasure.

  As a result of the study, the present inventors have found that (1) the eraser is formed by combining the base material and the porous foam, and (2) the tensile elastic modulus of the eraser is 0.6 MPa or more and 1.2 MPa or less. By satisfying these two conditions, it has been found that a character eraser having both high shape retention and high erasure can be provided. According to studies by the present inventors, if the eraser has a tensile elasticity of 0.6 MPa or more, sufficient shape retention is maintained in a normal use state, and the eraser is less likely to bend. On the other hand, simply setting the tensile modulus to 0.6 MPa or more and 1.2 MPa or less impairs the original property of the eraser for erasing characters. Therefore, by combining the base material of the raw material and the porous foam, and the manufacturing conditions of the eraser, the tensile elasticity is 0.6 MPa or more and 1.2 MPa or less, and both high shape retention and high eraseability are provided. Erasing can be provided.

  In the eraser of the present invention, the tensile modulus is more preferably 0.7 MPa or more. When the tensile elastic modulus of the eraser is 0.7 MPa or more, the shape eraser has a higher shape retention property and is harder to bend when erased.

  In the eraser, the porous foam is preferably a melamine foam. Melamine foam is easily collapsed by friction, has an appropriate tensile strength, and has high affinity with a base material. It is particularly suitable as a material for obtaining erasers having both high shape retention and high eraseability.

  In the above eraser, the resin component is preferably polyvinyl chloride. Polyvinyl chloride is particularly suitable as a material for obtaining eraser having both high shape retention and high eraseability.

  In the eraser, the tensile modulus of the porous foam is preferably from 0.03 MPa to 0.8 MPa, more preferably from 0.05 MPa to 0.4 MPa. By setting the tensile modulus of the porous foam within the above range, it is possible to appropriately maintain the flexibility and shape retention of the eraser.

In the eraser, the density of the porous foam is preferably from 3.5 kg / m ^{3 to} 12.0 kg / m ³ . By setting the density of the porous foam within the above range, it becomes easy to obtain a preferable form during production and use.

  According to the eraser, it is possible to provide an eraser having both high shape retention and high eraseability.

It is the schematic which shows the eraser of this invention. It is an enlarged sectional view of eraser. It is a figure showing the state where stress was applied to eraser. It is a figure which shows the state in which stress was applied to the eraser and the eraser was bent.

Next, one embodiment of the eraser according to the present invention will be described with reference to FIGS. FIG. 1 shows a eraser 10 according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view of the eraser.
A part of the eraser 10 is exposed for erase, and the other part is covered with a cover 20 for preventing contamination. As shown in FIG. 2, the eraser 10 has a structure in which the base material 110 is filled in the voids of the porous foam 120. The details will be described below.

[Base material]
The eraser 10 includes a base material 110 containing at least one of a resin component and an elastomer component and a plasticizer.

  Although not particularly limited, resins constituting the above resin component include thermoplastic resins, thermosetting resins, ultraviolet curable resins, electron beam curable resins, multi-component curable resins (such as two-component curable resins), and catalysts. Various resins such as a curable resin and a cellulose ester are exemplified. Among them, a thermoplastic resin is preferable. Such a resin can be used in a form dissolved in a solvent, in a form dispersed in a solvent, or in an emulsified form.

  Specific examples of the more preferable resin include polyvinyl chloride, vinyl chloride resin such as vinyl chloride-vinyl acetate resin, vinyl chloride-ethylene-vinyl acetate resin, and vinyl acetate resin such as ethylene-vinyl acetate resin. Is mentioned. Among them, a vinyl chloride resin, particularly polyvinyl chloride, is preferred because it is easily mixed with a plasticizer and is suitable for obtaining eraser having both high shape retention and high eraseability.

  Examples of the elastomer component include polyisoprene (natural rubber), styrene, butadiene, isoprene, ethylene-propylene, nitrile, chloroprene, urethane, acrylic, polyester, and olefin elastomers. Can be

  These resin components and elastomer components may be used alone or, if necessary, two or more of them may be used in combination.

  The plasticizer can be appropriately selected according to the thermoplastic resin used. For example, when the base material 110 contains polyvinyl chloride, phthalate-based plasticizers such as dioctyl phthalate, diheptyl phthalate, and dibutyl phthalate; acetyl citrate-based plasticizers such as acetyl tributyl citrate; Preferred are adipic ester plasticizers such as ethylhexyl adipate and adipic polyester, alkyl sulfonate plasticizers such as phenyl alkyl sulfonate, epoxy plasticizers, trimellitic plasticizers, and benzoic esters. Used for These plasticizers may be used alone or, if necessary, two or more of them may be used in combination.

  The base material 110 is preferably impregnated in the porous foam 120 in a state of a sol composition containing the vinyl chloride resin, particularly polyvinyl chloride, and a plasticizer. This is because the sol-like composition including the vinyl chloride resin and the plasticizer has fluidity in impregnating and absorbing the porous foam 120, and is easily cured in the voids of the porous foam 120.

  In the eraser 10, the total ratio of the resin component and the elastomer component in the base material 110 is not particularly limited. For example, at least one of the resin component and the elastomer component is contained in 100% by mass of the base material 110 in an amount of 10% by mass to 80% by mass, preferably 20% by mass to 70% by mass.

  In the eraser 10, the ratio of the plasticizer is, for example, 10% to 80% by mass, preferably 20% to 70% by mass in 100% by mass of the base material 110 (however, the resin component, The total of the elastomer component and the plasticizer is 100% by mass or less.)

  The base material 110 may further include a filler such as calcium carbonate, magnesium carbonate, magnesium oxide, silica, talc, clay, diatomaceous earth, quartz powder, alumina, alumina silicate, and mica. The proportion of the filler is, for example, 0% by mass or more and 70% by mass or less, preferably 5% by mass or more and 40% by mass or less in 110% by mass of the base material.

  The base material 110 may further include other additives such as an abrasive, a stabilizer, a coloring agent, a fragrance, a surfactant, and glycols. Examples of the stabilizer include metal soap, barium-zinc stabilizer, calcium-zinc stabilizer, magnesium-zinc stabilizer, phosphite stabilizer, and the like. As the colorant, known pigments such as organic pigments, inorganic pigments, and fluorescent pigments, known dyes, and the like can be used.

  Further, the base material 110 contains a color-change coloring component (pressure-sensitive color-change coloring component) composed of pressure-sensitive microcapsules that are crushed by rubbing force, and a color-change coloring component containing a heat-sensitive coloring component that changes color by rubbing heat. It may contain a dye component (thermochromic dye component).

[Porous foam]
The eraser 10 according to the present embodiment includes a porous foam 120 impregnated with a base material 110. The porous foam 120 preferably has a skeletal structure that can be impregnated with the base material 110 and that has a skeleton structure in which the skeleton of the porous foam 120 is separated and detached by the frictional force against the paper surface with the wear of the base material 110.

  The porous foam 120 is made of a thermosetting resin such as a melamine resin, an epoxy resin, a urethane resin, a urea resin, a phenol resin, a styrene resin such as polystyrene, an ester resin such as polyester, or a polyacrylate. Examples thereof include resins composed of various resins and elastomers such as thermoplastic resins such as acrylic resins such as acrylic resins, olefin resins such as polyethylene, and vinyl chloride resins such as polyvinyl chloride. Also, a natural polymer porous material such as sponge can be used. Furthermore, various rubber components such as natural rubber, styrene-butadiene rubber, nitrile-butadiene rubber, and natural fibers such as cotton, silk, and hemp, cellulose-based fibers, ester-based fibers, acrylic-based fibers, and amide-based fibers are synthesized. Various fibers such as fibers may be included.

  Among these, the porous foam 120 is formed of a melamine resin from the viewpoint of high affinity with the base material 110, the tissue is easily divided by the frictional force against the paper surface, and from the viewpoint of imparting an appropriate tensile modulus. It is preferably a melamine foam.

  The porous foam 120 is formed by selecting an appropriate material and controlling the thickness of the skeleton, the pore diameter of the void, the porosity, and the like, so that the tensile elastic modulus of the eraser 10 is 0.6 MPa or more and 1.2 MPa or less. It is formed so that With such a porous foam 120, it is possible to provide the eraser 10 having both high shape retention and high erasure and having appropriate flexibility. By having appropriate flexibility, it is possible to provide the eraser 10 in which force is easily applied when erasing characters and characters are easily erased.

[Manufacturing method of eraser 10]
The eraser 10 of the present invention is manufactured such that the base material 110 penetrates into the voids of the porous foam 120 and the base material 110 is included in the voids. Although the production method is not particularly limited, the following method is given as an example.

  First, the components of the base material 110 such as at least one of the resin component and the elastomer component, a plasticizer, and a filler and other additives added as necessary are sufficiently stirred and mixed to form a mother material. A material 110 is prepared. When a vinyl chloride resin is used as the resin component, for example, a granular resin is used. Separately, a sheet-like porous foam 120 is prepared.

  Next, the base material 110 is filled into the voids of the porous foam 120 by impregnating the base material 110 into the porous foam 120. For example, in a state where the porous foam 120 is allowed to stand, an uncured base material 110 may be charged in an amount sufficient to fill the voids of the porous foam 120, and the base material 110 may be absorbed into the voids. . Alternatively, by immersing the porous foam 120 in a mold on a plate filled with the uncured base material 110, the uncured base material 110 may be impregnated into the entire porous foam 120. When the porous foam 120 was impregnated with the uncured base material 110, the porous foam 120 was impregnated with the uncured base material 110 so that the uncured base material 110 spread over the entire voids of the porous foam 120. In this state, the porous foam 120 may be compressed by a press. Further, the eraser 10 may be degassed under reduced pressure so as not to include pores. Further, in order to uniformly and increase the encapsulation amount of the base material 110, the uncured base material 110 may be further poured over the porous foam 120 impregnated with the uncured base material 110 to be impregnated.

  The ratio between the porous foam 120 and the base material 110 is not particularly limited, and the porosity of the porous foam 120 (apparent rate of the porous foam 120) is set so that the base material is sufficiently filled in the voids of the porous foam 120. (The ratio of the total volume of the void to the volume of the gap) and the characteristics required for the eraser 10. As an example, the amount is 50 parts by mass or more and 200 parts by mass, preferably 100 parts by mass or more and 150 parts by mass or less with respect to 1 part by mass of the porous foam.

  The base material 110 is cured in a state where the uncured base material 110 is impregnated in the porous foam 120. In order to enhance productivity, curing is preferably performed by heating. Heating is preferably performed by a hot press because heating can be performed uniformly up to the center of the porous foam 120. The hot press is performed by pressing the porous foam 120 impregnated with the base material 110 with a plurality of press plates having dimensions larger than the porous foam 120. Further, the hot press may serve as both a press for spreading the base material 110 over the entire void portion of the porous foam 120 and a press for promoting hardening by heating.

The above-described curing by heating is preferably performed at a temperature of 100 ° C. to 160 ° C. for a heating time of 1 minute to 50 minutes. In particular, it is preferable to perform the heating at 110 ° C. or more and 120 ° C. or less for 1 minute or more and 20 minutes or less in order to manufacture a eraser having both high shape retention and high erasability. The heating is preferably performed under pressure by a press. The pressure at the time of pressing is appropriately set as needed. For example, the pressing pressure when pressing the eraser sheet can be set to 5 kgf / cm ² (49 N / cm ² ) or more and 150 kgf / cm ² (1470 N / cm ² ) or less.

  The base material 110 is, for example, a sol-state base material of 100 to 20,000 mPa · s (preferably 800 to 7,000 mPa · s) under the measurement conditions of a temperature of 20 ° C., a B-type viscometer, and a rotation speed of 6 rpm. It is desirable to use a material 110, particularly a sol composition of a polyvinyl chloride resin, as the uncured base material 110. This is because the base material 110 having a viscosity within this range has a suitable fluidity for impregnating and absorbing the uncured base material 110 in the porous foam 120 at normal temperature. In addition, this is because the void portion is easily filled and is easily cured in the filled state. It should be noted that even the uncured base material 110 having a high viscosity exceeding 20,000 mPa · s can be impregnated by decreasing the viscosity by heating or reducing the pressure.

  The eraser 10 is manufactured by cutting the sheet-shaped eraser substrate obtained by curing as described above into a predetermined size as necessary.

[Erasing]
The eraser 10 has a structure in which the base material 110 is impregnated in a porous foam 120. FIG. 2 is an enlarged sectional view of the eraser 10. Referring to FIG. 2, eraser 10 has base material 110 impregnated in porous foam 120 so that base material 110 is filled in pores of porous foam 120. In the eraser 10 state, the base material 110 is cured by heating and held in the porous foam 120.

  The eraser 10 is configured so that the base material 110 is worn away by rubbing during the erase operation and separates from the eraser, and the skeletal structure of the porous foam 120 is separated and separated with the wear of the base material 110. preferable.

  The eraser 10 manufactured as described above has a tensile modulus of 0.6 MPa or more and 1.2 MPa or less. According to the study of the present inventors, if the tensile elasticity of the eraser 10 is 0.6 MPa or more, sufficient shape retention is maintained in a normal use state, and the eraser is less likely to be bent.

  FIG. 3 and FIG. 4 are views showing a state where the eraser 10 is pressed against the paper surface 30 and the character is erased. When erasing characters on the paper 30 by the eraser 10, the user erases the characters drawn on the paper 30 by rubbing the eraser 10 against the paper 30 while pressing it. At this time, a force component f in the direction perpendicular to the paper surface 30 acts on the eraser 10. If the tensile elasticity is 0.6 MPa or more, the eraser 10 has a sufficient shape-retaining property, so that the deformation of the eraser 10 is small as shown in FIG. In this state, the deformation of the grounding portion 40 is small, and the grounding portion 40 moves and follows the movement of the hand, and the bending is small. Further, the user can easily see the ground portion 40 from the viewpoint of the user. Therefore, it is easy to erase even fine characters. In addition, since it is easy to apply force to the eraser 10, characters can be erased with a light touch (with a small force), and the usability is excellent.

  On the other hand, when the tensile modulus is less than 0.6 MPa, the bending of the eraser 10 is increased by the action of the force component f, as shown in FIG. Therefore, the contact area of the contact portion 50 is increased, and the ability of the contact portion 50 to follow the movement of the hand is also deteriorated. In addition, the grounding portion 50 is difficult to see from the user because it is blocked by the eraser 10. Therefore, it is difficult to selectively erase small characters. In addition, since the force applied to the eraser 10 is dispersed due to bending, an extra force is required to obtain a sufficient frictional force. In addition, since the outer peripheral side 12 of the bent portion is pulled, the eraser 10 is easily broken at the sleeve portion 22 which is a boundary between the eraser 10 and the cover 20. Therefore, the eraser shown in FIG. 4 is inferior in usability as compared with the eraser shown in FIG. If the tensile modulus is larger than 1.2 MPa, the eraser 10 is hardly bent, and as a result, the eraser is hardly erased.

  As described above, when the tensile elasticity of the eraser 10 is 0.6 MPa or more and 1.2 MPa or less, sufficient shape retention is maintained in a normal use state, and the eraser 10 is less likely to bend. As a result, it is possible to provide a character eraser 10 that is easy to erase fine characters, can erase characters with a light touch, and is excellent in usability.

  The tensile modulus is more preferably 0.7 MPa or more. When the tensile elastic modulus is 0.7 MPa or more, the above-mentioned effect due to the high tensile elastic modulus is more sufficiently exhibited.

  The tensile modulus can be measured, for example, by using a sample cut out in a dumbbell shape by a tensile tester in accordance with JIS K6251.

  The eraser 10 having the above-described tensile elasticity and having excellent erasure properties has a density and a pore suitable for forming the eraser 10 having a tensile elasticity of 0.6 MPa or more and 1.2 MPa or less. It can be obtained by selecting the porous foam 120 having properties such as the rate, adjusting the heating conditions when forming the eraser 10, and adjusting the type and amount of the plasticizer. As an example, a melamine foam is used as the porous foam 120, and the uncured base material 110 is hot-pressed at a temperature of 100 ° C. or more and 160 ° C. or less for 2 minutes or more and 50 minutes or less with the melamine foam impregnated. By heating while heating, the eraser 10 having a tensile modulus of 0.6 MPa or more and 1.2 MPa or less, and having both high shape retention and high erasure can be obtained.

  The surface hardness of the eraser 10 is not particularly limited, and is, for example, 50 to 85, preferably 60 to 75. The surface hardness can be measured by a method according to JIS S6050.

  The coefficient of friction of the eraser 10 is preferably 1.0 or less. If the friction coefficient of the eraser 10 is 1.0 or less, there is no problem in practical use. More preferably, the coefficient of friction of the eraser 10 is 0.8 or less. If the friction coefficient of the eraser 10 is 0.8 or less, the eraser can be easily erased with a light touch. Further, the wear rate of the eraser 10 is preferably 0.7% or more. When the wear rate is 0.7% or more, the surface is hardly stained when erasing characters, and erasing can be performed more easily.

  The erase ratio (%) of the eraser 10 is preferably 85% or more, more preferably 90% or more, more preferably 93% or more, and particularly preferably 94% or more. With such a erasure rate, characters can be efficiently erased by an appropriate number of times of friction. The erasure rate can be measured by a method based on JIS S 6050: 2002 6.4.

  As described above, according to the eraser 10 according to the present embodiment, it is possible to provide an eraser having both high shape retention and high eraseability.

  Hereinafter, the present invention will be described more specifically with reference to examples. The scope of the present invention is not to be construed as being limited by the description of these examples.

(Example 1)
(Preparation of eraser)
Example erasers were prepared using a base material having the following composition and a porous foam shown below. In addition, about the measurement of the particle diameter mentioned later, it performed by the method based on JISK5600-2-5; 1999, and measured the 3rd with a 100 micrometer glide gauge.

[Base material]
(1) Resin: polyvinyl chloride (trade name “ZEST P21”, manufactured by Shin-Daiichi PVC Co., Ltd.) (particle size: 55 μm, degree of polymerization 1550, K value 75.1, viscosity 5300 (mPa · s)) 0 parts by mass (2) Plasticizer (2-1) DOP (dioctyl phthalate) (manufactured by Nippon Rika Co., Ltd.) 32.3 parts by mass (2-2) DBP (dibutyl phthalate) (manufactured by Nippon Rika Co., Ltd.) 8 0.0 parts by mass (3) Filler 25.0 parts by mass of heavy calcium carbonate (manufactured by Bihoku Powder Chemical Industry Co., Ltd.) (4) Stabilizer (4-1) Magnesium-zinc-based stabilizer (trade name “EMBILIZER R- 23 L, manufactured by Tokyo Fine Chemical Co., Ltd.) 0.5 parts by mass (4-2) Organophosphorus stabilizer (trade name “EMBILIZER TC-110S, manufactured by Tokyo Fine Chemical Co., Ltd.) 0.2 parts by mass Total 100 The amount part

[Porous foam]
Melamine foam (trade name “Basoctect”, manufactured by BASF) (tensile modulus of melamine foam: 0.22 MPa, density: 9.0 kg / m ³ )

The components constituting the base material were charged into a stirring vessel and stirred until uniform, thereby preparing the base material. 20 parts by mass of a base material was impregnated into 0.15 parts by mass of a sheet-like melamine foam cut into a predetermined size (60 mm × 23 mm × 10 mm). With the base material impregnated in the melamine foam, the shape eraser A was prepared by hot pressing at a temperature of 105 ° C. and a press pressure of 10 kgf / cm ² (= 98 N / cm ² ) for 25 minutes to cure the base material. The friction coefficient of the obtained eraser A was 0.74.

(Example 2)
A eraser B was prepared in the same procedure as in Example 1 except that the conditions of the hot press were changed to a temperature of 113 ° C., a press time of 5 minutes, and a press pressure of 10 kgf / cm ² (= 98 N / cm ² ).

Example 3
With respect to polyvinyl chloride used as a resin component, eraser G was prepared in the same procedure as in Example 1 except that polyvinyl chloride having a particle diameter of 45 μm was used.

(Example 4)
With respect to polyvinyl chloride used as a resin component, eraser H was prepared in the same procedure as in Example 1 except that the one having a particle diameter of 63 μm was used.

(Example 5)
The eraser I was prepared in the same procedure as in Example 1 except that the melamine foam used had a tensile modulus of 0.14 MPa. The friction coefficient of the obtained eraser I was 0.66. Note that the density of the melamine foam is 5.6 kg / m ³ .

(Example 6)
The eraser J was prepared in the same procedure as in Example 1 except that the melamine foam used had a tensile modulus of 0.09 MPa. The friction coefficient of the obtained eraser J was 0.68. In addition, the density of the melamine foam is 8.9 kg / m ³ .

(Example 7)
The eraser K was prepared in the same procedure as in Example 1 except that the melamine foam used had a tensile modulus of 0.32 MPa. The friction coefficient of the obtained eraser K was 0.64. The density of the melamine foam is 6.2 kg / ^{m 3.}

(Example 8)
A eraser L was prepared in the same procedure as in Example 1 except that ATBC (tributyl acetyl citrate) was used as a plasticizer and the base material had the following structure.

[Base material]
(1) Resin: 36.0 parts by mass (2) Plasticizer: 40.0 parts by mass (3) Filler: 23.4 parts by mass (4-1): Magnesium-zinc stabilizer: 0.5 part by mass (4-2): Organic phosphorus-based stabilizer: 0.1 part by mass

Example 9
A eraser M was prepared in the same procedure as in Example 8, except that the base material had the following structure.

[Base material]
(1) Resin: 32.0 parts by mass (2) Plasticizer: 46.0 parts by mass (3) Filler: 21.5 parts by mass (4-1): Magnesium-zinc stabilizer: 0.4 part by mass (4-2): Organic phosphorus-based stabilizer: 0.1 part by mass

(Example 10)
A eraser N was prepared in the same procedure as in Example 8 except that the base material had the following structure.

[Base material]
(1) Resin: 31.0 parts by mass (2) Plasticizer: 48.0 parts by mass (3) Filler: 20.5 parts by mass (4-1): Magnesium-zinc stabilizer: 0.4 parts by mass (4-2): Organic phosphorus-based stabilizer: 0.1 part by mass

Example 11
An eraser O was prepared in the same procedure as in Example 8, except that the base material had the following structure.

[Base material]
(1) Resin: 30.0 parts by mass (2) Plasticizer: 50.0 parts by mass (3) Filler: 19.5 parts by mass (4-1): Magnesium-zinc stabilizer: 0.4 parts by mass (4-2): Organic phosphorus-based stabilizer: 0.1 part by mass

Example 12
DOA (di-2-ethylhexyl adipate) as a plasticizer, polyvinyl chloride (trade name “ZEST P22”, manufactured by Shin Daiichi PVC Co., Ltd.) as a resin (particle diameter: 55 μm, degree of polymerization 1060, K value 67.1, A eraser P was prepared in the same procedure as in Example 8, except that the viscosity was 3000 (mPa · s)) and the base material had the following structure.

[Base material]
(1) Resin: 36.0 parts by mass (2) Plasticizer: 40.0 parts by mass (3) Filler: 23.4 parts by mass (4-1): Magnesium-zinc stabilizer: 0.5 part by mass (4-2): Organic phosphorus-based stabilizer: 0.1 part by mass

(Example 13)
A eraser Q was prepared in the same procedure as in Example 12 except that the base material had the following structure.

[Base material]
(1) Resin: 32.0 parts by mass (2) Plasticizer: 46.0 parts by mass (3) Filler: 21.5 parts by mass (4-1): Magnesium-zinc stabilizer: 0.4 part by mass (4-2): Organic phosphorus-based stabilizer: 0.1 part by mass

(Example 14)
A eraser R was prepared in the same procedure as in Example 12, except that the base material had the following structure.

[Base material]
(1) Resin: 31.0 parts by mass (2) Plasticizer: 48.0 parts by mass (3) Filler: 20.5 parts by mass (4-1): Magnesium-zinc stabilizer: 0.4 parts by mass (4-2): Organic phosphorus-based stabilizer: 0.1 part by mass

(Example 15)
Except that polyvinyl chloride (trade name “ZEST P21”, manufactured by Shin-Daiichi PVC Co., Ltd.) (particle size: 55 μm, degree of polymerization 1550, K value 75.1, viscosity 5300 (mPa · s)) was used as the resin. A eraser S was prepared in the same procedure as in Example 13.

(Example 16)
A eraser T was prepared in the same procedure as in Example 8, except that ATBC and DOA were used as plasticizers and the base material had the following structure.

[Base material]
(1) Resin: 32.0 parts by mass (2-1) Plasticizer: ATBC: 23.0 parts by mass (2-2) Plasticizer: DOA: 23.0 parts by mass (3) Filler: 21.5 parts by mass Part (4-1): Magnesium-zinc stabilizer: 0.4 part by mass (4-2): Organophosphorus stabilizer: 0.1 part by mass

(Comparative Example 1)
An eraser C was prepared in the same procedure as in Example 2 except that no melamine foam was used.

(Comparative Example 2)
Using the same procedure as in Example 2 except that the melamine foam was not used and the temperature was 125 ° C., the pressing time was 10 minutes, and the pressing pressure was 10 kgf / cm ² (= 98 N / cm ² ). Prepared.

(Comparative Example 3)
A eraser E was prepared in the same procedure as in Example 2 except that melamine foam was not used and the amount of DOP (dioctyl phthalate) was changed to 33.0 parts by mass.

(Comparative Example 4)
A eraser F was prepared in the same procedure as in Example 2 except that melamine foam was not used and the amount of DOP (dioctyl phthalate) was changed to 25.0 parts by mass.

[Measurement of physical properties and evaluation of properties]
Each physical property of the eraser was measured by the following procedure, and the characteristics were evaluated.

[Tensile modulus]
The eraser 10 was punched out in the shape of a dumbbell with a mark line distance of 30 mm to prepare a test piece for a tensile test. Using the prepared test piece, the tensile modulus (MPa) was measured by a method according to JIS K6251.

[Evaluation of eraser characteristics]
Next, various characteristics as a general eraser were evaluated. As the characteristics, the erasing rate (%), the ease of applying force at the time of erasing, the easiness of erasing fine characters, and the easiness of soiling of the eraser surface were evaluated. The evaluation procedure is as follows.

[Erase rate]
The erasure rate was measured according to the following procedure based on JIS S 6050: 2002 6.4.

  (1) The eraser was cut into a plate having a thickness of 5 mm, and the end portion in contact with the colored paper was finished into an arc having a radius of 6 mm to obtain a test piece.

(2) Using an imager, colored paper was produced using pencil HB specified in JIS S 6006, high-quality paper having a basis weight of 90 g / m ² or more and a whiteness of 75% or more. The test piece was brought into contact with the colored paper perpendicularly and perpendicular to the colored line. In this state, a weight was placed on the test piece so that the sum of the weight of the weight and the weight of the holder was 0.5 kg, and the colored portion was rubbed four times at a speed of 150 ± 10 cm / min.

  (3) Using a densitometer, the density of the non-colored portion of the colored paper was set to 0, and the densities of the colored portion and the abrasion portion were measured.

  (4) The erasure rate was calculated by the following equation, and the average value of three times was obtained.

  Erase rate (%) = (1− (density of abraded area / density of colored area)) × 100

[Easy entry of power, easy erasure of fine characters, easy erasure of eraser surface]
By actually erasing using the erasers of the examples and comparative examples, the easiness of applying force and the easiness of erasing fine characters were evaluated. In addition, the degree of dirt on the eraser surface after erasure was confirmed, and the degree of dirt on the surface was evaluated. Regarding the ease of applying force, the order of superiority was expressed as good, almost good, average, and difficult to enter.

[Hard to break]
A paper and a sample of eraser 10 in which a cover 20 was covered so as to expose a 12 mm × 23 mm × 10 mm portion at the tip of a eraser 10 of 60 mm × 23 mm × 10 mm were prepared. While holding the cover 20 with the operator's thumb and index finger, the eraser 10 was brought into contact with the paper so that the angle between the eraser 10 and the paper was about 45 °. In this state, a reciprocating motion is performed 70 times in a range of 130 mm while applying a load of 1 kgf (9.8 N), and then reciprocating 70 times in a range of 130 mm in length while applying a load of 2.5 kgf (24.5 N). Exercise. After the reciprocation, it was determined whether the eraser was broken. This evaluation was performed for each sample with the sample number n = 5. The case where the number of samples broken (broken) during the reciprocating motion was 0 was evaluated as “good”, the case of 2 or less was evaluated as “slightly poor”, and the case of 3 or more was evaluated as “poor”.

  Each eraser of the example and the comparative example was evaluated as described above. The results are shown in Tables 1, 2, 3 and 4.

注釈）※１ 字消しの屈曲は少ないが、紙面上で摩耗しないため摩擦力が少なく、滑りやすい。
※２）表面組織が充分に摩耗しないため、筆跡が伸びて紙面が汚れる。

Note) * 1 Although the erasure is less bent, it does not wear on the paper surface, so it has less friction and is slippery.
* 2) Since the surface structure is not sufficiently worn, the handwriting extends and the paper surface becomes dirty.

(result)
Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 9, Example 10, Example 11, Example 12, Example Thirteenth, fourteenth, fifteenth, and sixteenth examples are examples of erasers that fall within the scope of the present invention. Comparative Examples 1 and 2 are examples of erasers having a tensile modulus of less than 0.6 MPa. Comparative Examples 3 and 4 are erasers that have a tensile modulus of 0.6 MPa or more but do not include a porous foam. The erasers of Comparative Examples 1 and 2 also do not include a porous foam.

  In the case of the erasers of Comparative Example 1 and Comparative Example 2 in which the tensile elastic modulus is less than 0.6 MPa, a force is hardly applied since the eraser is bent at the time of erase. Therefore, it is difficult to erase fine characters. Black stains are likely to remain on the eraser surface after erase. Furthermore, as shown in the evaluation of the difficulty in breaking, it was also found that the material was very fragile and the life of the eraser was shortened. In particular, since the erasers of Comparative Examples 1 and 2 had low tensile elasticity and were easily bent, it was found that the eraser 10 was in contact with the sleeve 22 at the boundary between the eraser 10 and the cover 20 in FIG. .

  The erasers of Comparative Examples 3 and 4 have a tensile modulus of 0.6 MPa or more. However, when the tensile elastic modulus is increased without using the porous foam, the eraser does not have the characteristics that the original should have. Specifically, the erasure rate is significantly lower than those of the other examples and comparative examples. For this reason, the characters are not sufficiently erased, and the graphite of the characters is stretched by friction, so that the paper surface is significantly stained. In addition, since the tensile modulus is 0.6 MPa or more, it is difficult to bend at the time of erasing, but since it does not wear on the surface, the frictional force against the paper surface is small and it is easy to slide. Therefore, it is practically difficult to use as eraser.

  On the other hand, the erasers of Examples 1 to 16 were satisfactory evaluation results for all the characteristics. Specifically, the erasers of Examples 1 and 16 have a tensile modulus of 0.6 MPa or more and 1.2 MPa or less, so that force is easily applied at the time of erase, and characters are erased with a light touch. Can be. In addition, since there is little bending even when a force is applied, the user can easily see the contact surface with the paper surface, and the contact surface follows the movement of the user's hand with high follow-up. Therefore, it is easy to erase fine characters. In addition, since melamine foam is contained as a porous foam, the eraser scraps worn from the eraser during the eraser are easily detached and new tissues are exposed one after another, so that the surface of the eraser is less stained. Also, in the evaluation of the difficulty of breaking, no sample that was broken during the reciprocating motion was observed. This is because the erasers in Examples 1 to 16 in which the tensile elastic modulus is within the above range are hardly bent, and the eraser has less contact with the sleeve portion. These results indicate that the erasers of Examples 1 to 16 have high shape retention.

  It should be noted that the high erasure rate does not always correlate with the good usability of eraser. This is because in the measurement of erasure rate, a normal eraser is used in which a test piece to erase is applied perpendicularly to the paper surface while applying a load in a direction perpendicular to the paper surface. This is because, in the use scene, the character is frequently erased while applying a load obliquely to the paper surface. The eraser bends when a load is applied obliquely to the paper surface. At this time, a character eraser having a tensile modulus of 0.6 MPa or more and 1.2 MPa or less has an advantageous characteristic that it has sufficient resistance to bending, so that it is easy to apply force and it is easy to erase fine characters.

  As described above, the base material containing at least one of the resin component and the elastomer component, and the plasticizer, and the porous foam impregnated with the base material, including 0.6 MPa or more and 1.2 MPa or less. By using the eraser having a tensile elasticity, it is possible to achieve both high shape retention and high eraseability. As a result, it is possible to provide a character eraser that is easy to apply power, can erase characters with a light touch, and can easily erase fine characters.

  In Examples 5, 6, and 7, the coefficient of friction for eraser is 0.8 or less. Therefore, it is easy to erase characters with a light touch.

  Further, in Examples 1, 3 and 4, polyvinyl chloride particles having different particle diameters were used. All of these have good evaluations. Here, if the particle size of the polyvinyl chloride is too large, for example, more than 100 μm, the gel hardness of the obtained eraser tends to be low. Further, the obtained eraser is soft as a characteristic, and tends to be largely collapsed during use. Further, a granular mass appears on the surface of the obtained eraser, which tends to be unfavorable in appearance. On the other hand, if the particle size of polyvinyl chloride is too small, for example, smaller than 20 μm, the resulting gel eraser tends to have a high gel hardness. In addition, the obtained eraser tends to be hard and has a tendency to crumble like powder when used. In addition, erased dust after use tends to be very fine, and contaminates the surrounding environment. Further, the eraser surface after use tends to be contaminated. Therefore, if the particle size of polyvinyl chloride is 20 μm or more and 100 μm or less, it becomes easy to manufacture the eraser in a preferable form. By setting the particle diameter of polyvinyl chloride to 45 μm or more and 63 μm or less as shown in Example 1, Example 3, and Example 4, the eraser can be more reliably manufactured in a preferable form.

As for the porous foam used, if the porous foam is very soft and has a coarse density, that is, if the gap formed in the porous foam is large, it is difficult to sufficiently obtain the effect of impregnation utilizing the capillary phenomenon at the time of production. Therefore, the resin component melted in the porous foam tends to be hardly impregnated. Also, the obtained eraser has no so-called stiffness and tends to bend easily. In addition, the eraser wear during use tends to be largely collapsed without being finely collapsed. Further, voids tend to be easily formed inside the obtained eraser. On the other hand, when the porous foam is very hard and has a high density, that is, when the gap formed in the porous foam is small, it tends to be difficult to impregnate the inside of the porous foam with a resin component melted during the production. Also, the obtained eraser tends to have a reduced amount of eraser wear during use, less likely to have a new surface, and inferior erasability. Therefore, by setting the density of the porous foam to, for example, 3.5 kg / m ³ or more and 12.0 kg / m ³ or less, it becomes easy to obtain a preferable form during production and use.

  It should be understood that the embodiments disclosed this time are illustrative in all aspects and are not restrictive in any aspect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The eraser according to the present invention can be particularly advantageously applied in a field in which eraser having both high shape retention and high eraseability is required.

10 character eraser, 12 outer peripheral side of bent portion, 20 cover, 22 sleeve portion, 30 paper surface, 40 ground portion, 50 ground portion, 110 base material, 120 porous foam

Claims (5)

A base material containing at least one of a resin component and an elastomer component, and a plasticizer,
A porous foam impregnated with the base material,
An eraser having a tensile modulus of 0.6 MPa or more and 1.2 MPa or less.   2. The eraser according to claim 1, wherein the porous foam is a melamine foam.   3. The eraser according to claim 1, wherein the resin component is polyvinyl chloride.   The eraser according to any one of claims 1 to 3, wherein a tensile modulus of the porous foam is 0.05 MPa or more and 0.4 MPa or less. The eraser according to any one of claims 1 to 4, wherein the density of the porous foam is 3.5 kg / m ³ or more and 12.0 kg / m ³ or less.

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