Plastic letter erasure

Abstract

To provide a plastic eraser that not only has excellent erasability and generates eraser dust easily, but also excels in both lightness of eraser feeling and degree of accumulation of eraser dust, which was difficult to achieve at the same time.SOLUTION: A plastic eraser containing at least a vinyl chloride resin, a plasticizer, spherical particles, and an acrylic thermoplastic elastomer as a base resin has an erasability that can erase writing lines, which is the original performance of the eraser, and not only produces good erasing dust when erasing characters, but also achieves both a light erasing feeling and a degree of accumulation of erasing dust.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to erasing plastic letters.

Background Art

[0002] Erasers are widely used as an essential tool for erasing written lines because of their excellent erasing property.

[0003] The mechanism of erasing written lines with an eraser is as follows: the eraser is brought into close contact with the written line on the paper surface and rubbed, so that the written line is adsorbed by the eraser. At the same time, the surface part of the eraser that has adsorbed the written line (the part in close contact with the paper surface) is detached from the eraser as eraser dust, and the surface of the eraser is renewed, so that the written line can be adsorbed again. Therefore, the generation of eraser dust is essential for an eraser. An eraser that does not generate eraser dust or is less likely to generate eraser dust has insufficient erasing property because the surface of the eraser does not become new. Therefore, an eraser is required to be able to adsorb the written line well and detach the eraser dust from the eraser well.

[0004] For example, Patent Documents 1 and 2 disclose that by containing two or more thermoplastic elastomers including an acrylic thermoplastic elastomer as a base resin and a softening agent, excellent erasing property can be obtained because it can penetrate to the bottom of the paper surface recessed by writing, and an eraser with good generation of eraser dust can be obtained. In addition, with the improvement of the performance of erasers, various additional performances such as more excellent erasing property, light erasing feeling, and degree of accumulation of eraser dust have been required.

[0005] For example, Patent Document 3 discloses an eraser that uses a thermoplastic elastomer as a base resin and further contains a 1-butene homopolymer or a copolymer containing 1-butene as a main component, which is easy to produce eraser dust, has excellent erasing property, and has a very good erasing feeling. However, an eraser with excellent erasing performance is obtained by increasing the hardness of the eraser and reducing the frictional resistance between the eraser and the paper surface when erasing the writing lines. In this case, however, it is known that the degree of accumulation of eraser shavings detached from the eraser deteriorates significantly. When the degree of accumulation of eraser shavings is poor, there is a problem that the generated eraser shavings scatter in the vicinity and stain the surroundings and the paper surface, significantly reducing the writability. On the other hand, in order to improve the degree of accumulation of eraser shavings, if the hardness of the eraser is reduced and the frictional resistance is increased, the erasing feeling becomes heavy.

[0006] In an eraser, the lightness of the erasing feeling and the degree of accumulation of eraser shavings are in an antinomic relationship where improving one worsens the other, and no eraser that satisfies both the lightness of the erasing feeling and the degree of accumulation of eraser shavings has been proposed yet.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Disclosure of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a plastic eraser that is excellent in erasability, easily generates eraser shavings, and is excellent in both the lightness of the erasing feeling and the degree of accumulation of eraser shavings, which have been difficult to reconcile.

Means for Solving the Problems

[0009] As a result of intensive research to solve the above problems, the present inventor has found that a plastic eraser containing at least a vinyl chloride resin as a base resin, a plasticizer, spherical particles, and an acrylic thermoplastic elastomer can solve the problem of achieving both a light erasing feeling and a degree of accumulation of eraser shavings, and has reached the present invention.

[0010] That is, the present invention is as follows. (1) A plastic eraser characterized by containing at least a vinyl chloride resin as a base resin, a plasticizer, spherical particles, and an acrylic thermoplastic elastomer. (2) The plastic eraser according to (1) above, wherein the average particle diameter of the spherical particles is 1 to 50 μm. (3) The plastic eraser according to (1) or (2) above, wherein the content of the spherical particles is 1 to 5% by mass based on the total amount of the plastic eraser. (4) The plastic eraser according to any one of (1) to (3) above, wherein the content of the acrylic thermoplastic elastomer is 0.1 to 5% by mass based on the total amount of the plastic eraser. (5) The plastic eraser according to any one of (1) to (4) above, wherein the acrylic thermoplastic elastomer is a block copolymer composed of a hard segment having methyl methacrylate as a main constituent monomer and a soft segment having butyl acrylate, or butyl acrylate and 2-ethylhexyl acrylate as main constituent monomers.

Effects of the Invention

[0011] According to the present invention, it is possible to provide an eraser that not only has good erasability, which is the original performance of an eraser, and good generation of eraser shavings when erasing writing lines, but also achieves both a light erasing feeling and a degree of accumulation of eraser shavings.

Brief Description of the Drawings

[0012]

Figure 1

Best Mode for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described in detail.

[0014] The present invention is characterized by containing at least a vinyl chloride-based resin and a plasticizer as base resins widely used in erasing plastic letters, as well as spherical particles and an acrylic thermoplastic elastomer.

[0015] [Base Resin] The present invention uses a vinyl chloride-based resin as the base resin. The vinyl chloride-based resin is suitable in that it can obtain erasable letters with a light erasing feeling.

[0016] As the vinyl chloride-based resin, all conventionally used vinyl chloride-based resins can be used. For example, in addition to polyvinyl chloride having a degree of polymerization of about 400 to 4,000, vinyl chloride-vinyl acetate copolymer, vinylidene chloride, vinyl chloride-methyl acrylate copolymer, vinyl chloride-methyl methacrylate copolymer, and vinyl chloride-octyl acrylate copolymer can be mentioned. These may be used alone or in combination of two or more as needed. As the vinyl chloride-based resin, a paste resin is preferable in terms of easy mixing and processing with a plasticizer or the like.

[0017] The content of the vinyl chloride-based resin is preferably 15 to 40% by mass based on the total amount of the composition constituting the erasable plastic letters. Within this range, the erasing feeling of the erasable letters will not become too heavy (light). More preferably, it is 20 to 35% by mass, and particularly preferably 20 to 30% by mass. Hereinafter, "% by mass" will be abbreviated as "%".

[0018] [Plasticizer] The present invention can use known plasticizers without particular limitation, and plasticizers having excellent miscibility with vinyl chloride resins are preferably used.

[0019] Specific examples of preferred plasticizers include, for example, Phthalic acid-based plasticizers such as di-2-ethylhexyl phthalate (DOP), di-n-octyl phthalate (n-DOP), diisononyl phthalate (DINP), dinonyl phthalate (DNP), diisodecyl phthalate (DIDP), ditridecyl phthalate (DTDP), diundecyl phthalate (DUP); Trimellitic acid-based plasticizers such as tri-2-ethylhexyl trimellitate (TOTM), triisodecyl trimellitate (TIDTM), triisooctyl trimellitate (TIOTM), triisononyl trimellitate; Pyromellitic acid-based plasticizers such as trioctyl pyromellitate (TOPM); Polyester-based plasticizers such as polyesters obtained by condensing at least one of dibasic acids (e.g., adipic acid), polyhydric alcohols (e.g., aliphatic glycols having 2 to 18 carbon atoms and polyalkylene glycols such as diethylene glycol and dipropylene glycol), and at least one selected from monohydric alcohols having 9 to 18 carbon atoms or monocarboxylic acids having 9 to 18 carbon atoms (including liquid polyester-based plasticizers); Epoxy-based plasticizers such as epoxidized oils and epoxidized fatty acid esters; Adipic acid-based plasticizers such as di-2-ethylhexyl adipate (DOA), diisononyl adipate (DINA), diisodecyl adipate (DIDA); Sebacic acid-based plasticizers such as di-2-ethylhexyl sebacate (DOS), dibutyl sebacate (DBS); Azelaic acid-based plasticizers such as di-2-ethylhexyl azelate (DOZ); Phosphoric acid-based plasticizers such as tricresyl phosphate (TCP), tri-2-ethylhexyl phosphate (TOP); Citric acid plasticizers such as triethyl citrate, acetyl tri-n-butyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-(2-ethylhexyl) citrate, etc.; Benzoic acid plasticizers such as PN-6120, PN-6122 (both are trade names, ADEKA Corporation, glycol diester), Benzoflex9-88 (dipropylene glycol dibenzoate), Benzoflex50 (a mixture of diethylene glycol dibenzoate and dipropylene glycol dibenzoate), Benzoflex2088 (a mixture of diethylene glycol dibenzoate, dipropylene glycol dibenzoate, and triethylene glycol dibenzoate) (all are trade names, EASTMAN), PB-3A, W-83 (both are trade names, DIC Corporation), etc.; Phenyl alkyl sulfonates such as Mesamoll, Mesamoll II (both are trade names, Lanxess); Cyclohexanedicarboxylic acid esters such as DINCH (trade name, BASF); And the like. The above plasticizers may be used alone or in combination of two or more as necessary.

[0020] Among the above phenyl alkyl sulfonates, they are represented by the following chemical formula. [Chemical formula]

[0021] Among the above plasticizers, non-phthalic acid plasticizers are preferred because of their high environmental adaptability. Among non-phthalic acid plasticizers, phenyl alkyl sulfonates and glycol dibenzoates, which are excellent in erasability and have little stickiness, are more preferred. These plasticizers have high compatibility with vinyl chloride resins, are easily mixed or kneaded, are less likely to cause plasticizer migration, and are excellent in heat resistance and processability. In addition, it is also preferable to use the above plasticizer in combination with a liquid acrylic polymer or a liquid polyester that is liquid at room temperature. By using the liquid acrylic polymer or the liquid polyester in combination with other ester-based plasticizers, the migration resistance of other plasticizers (suppressing the migration of the plasticizer to the erased surface) can be improved, and an erasable character with a non-sticky surface and high erasability can be obtained.

[0022] The content of the plasticizer is preferably 30 to 70% with respect to the total amount of the composition constituting the plastic erasable character. Within this range, the erasable character will not become too soft (hard), so there is no risk of a decrease in erasability, and there is also no risk of affecting the erasing feeling and the degree of accumulation of erasing debris. More preferably, it is 40 to 65%, and particularly preferably 45 to 60%.

[0023] [Spherical particles] In the present invention, as a filler with good friction, at least one kind of spherical particle selected from inorganic particles or organic particles is blended separately from the fillers described below. By blending spherical particles, the frictional resistance between the erasable character and the paper surface can be suppressed, and a good erasing feeling can be obtained. Examples of the inorganic spherical particles include shirasu balloons, fly ash balloons, glass beads, glass bubbles, titanium oxide, spherical silica, and the like. Examples of the organic spherical particles include spherical acrylic polymers, spherical urethane polymers, spherical styrene polymer particles, spherical nylon polymers, spherical fluororesin polymers, and the like. The above spherical particles may be used alone or in combination of two or more as required. Among these, glass beads and spherical silica are preferable in terms of being able to keep the frictional resistance low and being able to make the erasing feeling lighter.

[0024] The spherical particles preferably have an average particle diameter of 1 to 50 μm. If the average particle diameter is 1 μm or more, erasing debris is likely to occur, and a good erasable character with a light erasing feeling can be obtained. If the average particle diameter is 50 μm or less, there is no risk of a decrease in erasability due to the erasing feeling becoming too light. More preferably, the average particle diameter is 5 to 45 μm. The average particle diameter can be measured by the laser diffraction method.

[0025] The content of spherical particles is preferably 1 to 5% with respect to the total amount of the composition constituting the plastic eraser. If the blending amount of spherical particles is 1% or more, the erasing feeling can be sufficiently reduced. If it is 5% or less, the frictional resistance becomes too small and there is no risk of impairing the erasing property and the degree of accumulation of eraser dust. More preferably, it is 1 to 4%, particularly preferably 1.5 to 3.5%.

[0026] The mixing ratio of the spherical particles and the acrylic thermoplastic elastomer described below is preferably such that the spherical particles / acrylic thermoplastic elastomer is 50 / 50 to 90 / 10. Within this range, a light erasing feeling can be obtained, and erasing with a good degree of accumulation of eraser dust can be obtained. More preferably, it is 50 / 50 to 80 / 20.

[0027] [Acrylic thermoplastic elastomer] In the present invention, the acrylic thermoplastic elastomer is used for the purpose of imparting adhesiveness and mainly contributes to the degree of accumulation of eraser dust.

[0028] A thermoplastic elastomer is a material that exhibits rubber elasticity like crosslinked rubber at room temperature and exhibits plasticity like a thermoplastic resin when heated, enabling heat molding. As thermoplastic elastomers, styrene-based, olefin-based, acrylic-based, vinyl chloride-based, polyester-based, polyurethane-based, polyamide-based, chlorinated polyethylene copolymer crosslinked body alloys, etc. are known. Among them, acrylic thermoplastic elastomers are preferred because they can suppress an improvement in the degree of accumulation of eraser dust and an increase in the frictional resistance of erasing (the erasing feeling becomes heavier).

[0029] As the acrylic thermoplastic elastomer, those composed of a hard segment A having a methacrylic acid ester as a main constituent monomer for preventing plastic deformation and a soft segment B having an acrylic acid ester having elasticity as a main constituent monomer can be used. As the bonding form of the hard segment A and the soft segment B, there are AB type diblock copolymers, ABA type triblock copolymers, star block copolymers, etc. Among them, triblock copolymers are preferable because they are more likely to form a filamentous network in the vinyl chloride-based base resin.

[0030] Examples of the methacrylic acid ester which is the main constituent monomer of the hard segment A include esters of methacrylic acid and fatty acids having 1 to 18 carbon atoms. Among them, from the viewpoint of adhesion characteristics, monomers such as esters of methacrylic acid and alcohols having 3 or less carbon atoms, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate, are preferable, and methyl methacrylate is particularly preferable. Examples of the acrylic acid ester which is the main constituent monomer of the soft segment B include esters of acrylic acid and fatty acids having 1 to 12 carbon atoms. Among them, from the viewpoint of adhesion characteristics, n-butyl acrylate or a combination of n-butyl acrylate and 2-ethylhexyl acrylate is preferable.

[0031] The content of the hard segment A in the acrylic thermoplastic elastomer is preferably 5 to 30%, more preferably 10 to 30%, and still more preferably 10 to 25% based on the total amount of the triblock copolymer. Within this range, good chip accumulation degree and a light erasing feeling can be obtained.

[0032] If the weight average molecular weight of the acrylic thermoplastic elastomer is in the range of 60,000 to 400,000, good chip accumulation degree for erasing can be imparted, and the moldability is also good. When the weight average molecular weight becomes small, the cohesive force decreases. On the other hand, when the weight average molecular weight becomes large, the melt moldability for erasing tends to be poor. The weight average molecular weight is a value obtained from the polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC).

[0033] As the triblock copolymer, commercially available products can also be used. Examples of the triblock copolymer of methyl methacrylate and n-butyl acrylate include, for example, Clarite LA2140, LA2250, LA2270, LA2330, LA3320, LA4285, etc. Also, as the triblock copolymer of methacrylic acid and n-butyl acrylate / 2-ethylhexyl acrylate, there is Clarite LK9243, etc. (all of the above are trade names, manufactured by Kuraray Co., Ltd.). These may be used alone or in combination of two or more as required.

[0034] The acrylic thermoplastic elastomer is preferably contained in the range of 0.1 to 5% based on the total amount of the composition constituting the plastic eraser. If the content is 0.1% or more, the chip accumulation degree for erasing can be improved. If it is 5% or less, there is no risk of the erasing feeling becoming heavy. More preferably, it is 0.1 to 4%, and particularly preferably 0.2 to 3%.

[0035] In the present invention, the reason for obtaining an eraser with a light erasing feeling and a good chip accumulation degree by blending the acrylic thermoplastic elastomer is not clear, but it is presumed as follows. That is, generally, when the hardness of the eraser is reduced to increase the chip accumulation degree, the frictional resistance between the eraser and the paper surface increases, so the erasing feeling becomes heavy. However, it is presumed that the reason is that the acrylic thermoplastic elastomer forms a filamentous network inside the eraser, and spherical particles or fillers are arranged between the networks, so that the acrylic thermoplastic elastomer does not inhibit the behavior of the materials (spherical particles or fillers) that impart lightness.

[0036] [Filler] In the eraser of the present invention, a filler can be blended to adjust the hardness and erasing feeling. As the filler, it is common to use silica powder (main component: silicon dioxide) or limestone powder (heavy calcium carbonate), and these inorganic powders are used in a finely divided form so as not to damage the writing surface. In addition, diatomaceous earth, talc, shirasu powder, magnesium carbonate, inorganic and organic hollow particles, etc. can be used. Limestone powder is preferred because a good erasing feeling can be obtained.

[0037] The blending amount of the filler is preferably 15 to 40% based on the total amount of the composition constituting the plastic eraser. If the blending amount is 15% or more, the erasing feeling does not become heavy and erasing chips are likely to come out, so the erasing property does not decrease. Also, if it is 40% or less, the area of the base resin in contact with the paper surface is sufficiently ensured, so the erasing property does not decrease. More preferably, it is 20 to 35%, and particularly preferably 20 to 30%.

[0038] [Stabilizer] In the eraser of the present invention, a stabilizer can be used as necessary to prevent the base resin from deteriorating at high temperature during molding, and a light stabilizer such as an ultraviolet absorber can also be blended to improve the light stability. In addition, additives such as a viscosity modifier, a lubricant, a solvent, a coloring agent, a preservative, a fungicide, and a fragrance can be blended. The blending amounts of these additives are not particularly limited as long as they are within a range that does not inhibit the effects of the present invention.

[0039] [Erasing feeling] In the present invention, the erasing feeling can be represented by the dynamic friction coefficient between the eraser and the paper surface, and the smaller the numerical value, the lighter the erasing feeling during erasing. The kinetic friction coefficient is preferably 0.60 or more and less than 0.90. In actual use, if the kinetic friction coefficient is too small, the writing line will stretch, and it will be difficult to scrape the erasing surface, so it will disappear before the erasing is completed. If the kinetic friction coefficient is 0.60 or more, the eraser can firmly bite into the paper and erase the writing line. On the other hand, if the kinetic friction coefficient is less than 0.90, a good erasing feeling can be obtained. More preferably, it is 0.60 to 0.85, and particularly preferably 0.60 to 0.80.

[0040] <Manufacturing method> The eraser of the present invention can be manufactured by kneading a predetermined amount of a base resin, a plasticizer, spherical particles, an acrylic thermoplastic elastomer, a filler, a stabilizer, and various additives as required by a conventional method, and then molding by a known method such as press molding, injection molding, or extrusion molding. The molding temperature is 90 to 150°C. The molded product is cut into a predetermined size to obtain the product. The manufacturing method is not particularly limited, and a manufacturing method that can obtain a light erasing feeling and a degree of eraser chip accumulation can be selected.

Examples

[0041] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The kinetic friction coefficient and the degree of eraser chip accumulation of the eraser were measured and evaluated by the following methods.

[0042] [Kinetic friction coefficient] The method for measuring the kinetic friction coefficient will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing the method for measuring the kinetic friction coefficient. (a) is a view of the entire friction tester seen from the side, and (b) is a view of the metal plate 2 with four test pieces 1 and the wire 6 attached seen from below (bottom side). Note that since FIG. 1 is a schematic diagram, the ratio of the sizes and the shapes of the respective parts are not accurate. (1) A rectangular plate-shaped eraser with a width of 12 mm, a height of 8 mm, and a thickness (length) of 5 mm, whose lower tip (the part in contact with the test paper 4) is formed into an arc with a radius of 6 mm, was used as the test piece 1, and a total of 4 pieces were produced. (2) Four test pieces 1 were attached one by one to the four corners of the lower surface of a square (60 mm in length × 60 mm in width) metal plate 2 with a thickness (height) of 6 mm, with the arcs of the test pieces facing downward and in the same orientation (see Fig. 1(b)). (3) The friction tester 5 installed horizontally on the ground includes a test bench 5b that can move horizontally above the main body 5a and a load cell 5c. A test paper 4, which is PPC paper with a whiteness of 90% or more, was attached to the test bench 5b. (4) On the above test paper 4, the metal plate in (2) above was placed with the test piece 1 on the lower side and in such a direction that the moving direction of the test bench 5b is the tangential direction of the vertex of the arc of the test piece 1 (the direction perpendicular to the thickness direction of the test piece 1), and the four test pieces 1 were brought into perpendicular contact with the test paper 4. (5) A weight 3 was placed on the center of the upper surface of the metal plate 2 so that the combined weight with the metal plate 2 is 0.5 kg. (6) The metal plate 2 was connected to the load cell 5c via a wire 6, and the test bench 5b (and the test paper 4) was moved 50 mm in the direction opposite to the load cell 5c side (the arrow direction in Fig. 1(a)) at a speed of 200 mm / min, and the coefficient of kinetic friction between the four test pieces 1 and the test paper 4 was measured, and the median value of the three measurements was taken as the measured value.

[0043] [Degree of aggregation] (1) The eraser was cut into a plate shape with a thickness of 5 mm, and the tip portion in contact with the test paper was formed into an arc with a radius of 6 mm as the test piece. (2) The above test piece was fixed to a test piece holder used for the test of erasing ability (erasure rate) in JIS S6050:2002 6.4. (3) The above test piece was reciprocated 20 times (erasure distance: 160 cm, speed: 150 cm / s) under a constant load (erasure load: 500 gf) on an uncolored test paper (basis weight: 90 g / m 2 or more, high-quality paper with a whiteness of 75% or more), and the number of eraser dust generated was counted visually and evaluated. The evaluation criteria are as shown in Table 1.

[0044]

Table 1

[0045] (Examples 1 to 14, Comparative Examples 1 to 5) Each composition shown in Table 2 was blended at the blending ratios (numbers are parts by mass) shown in the same table, kneaded with a pressure kneader, and then heat-extruded at 110 °C to obtain an eraser (test piece).

[0046] For the obtained eraser (test piece), the coefficient of kinetic friction was measured and the degree of accumulation of eraser shavings was evaluated. The results are shown in Table 2.

[0047] [Table 2]

[0048] From the results in Table 2, it can be seen that the plastic erasers of the present invention (Examples 1 to 14) can suppress the coefficient of kinetic friction while improving the degree of accumulation of eraser shavings by an acrylic thermoplastic elastomer and spherical particles. That is, it is possible to erase the writing line with a light erasing feeling and to make an eraser in which the detached eraser shavings do not scatter but gather. On the other hand, in Comparative Examples 2 to 4 in which a polymer component other than the acrylic thermoplastic elastomer was blended, the degree of accumulation of eraser shavings was improved, but the coefficient of kinetic friction also increased, and a light erasing feeling was not obtained. The same applies to Comparative Example 5 that does not contain spherical particles. In Examples 1 to 14, it is presumed that spherical particles and fillers are arranged between the filamentous networks formed by the acrylic thermoplastic elastomer and do not inhibit the behavior (lightness of the erasing feeling) imparted by these.

Industrial Applicability

[0049] The plastic eraser of the present invention can be suitably used for erasing writing lines such as those of pencils and mechanical pencils.

Explanation of Signs

[0050] 1 Test piece (eraser) 2 Metal plate 3 Weight 4 Test paper 5 Friction tester 5a Main body part 5b Test bench 5c Load cell 6 wires

Claims

1. A plastic eraser characterized by containing at least a vinyl chloride resin as a base resin, a plasticizer, spherical particles, and an acrylic thermoplastic elastomer.

2. The plastic eraser according to Claim 1, wherein the average particle diameter of the spherical particles is 1 to 50 μm.

3. The plastic eraser according to Claim 1 or 2, wherein the content of the spherical particles is 1 to 5% by mass based on the total amount of the plastic eraser.

4. The plastic eraser according to any one of Claims 1 to 3, wherein the content of the acrylic thermoplastic elastomer is 0.1 to 5% by mass based on the total amount of the plastic eraser.

5. The plastic eraser according to any one of Claims 1 to 4, wherein the acrylic thermoplastic elastomer is a block copolymer composed of a hard segment having methyl methacrylate as a main constituent monomer and a soft segment having butyl acrylate, or butyl acrylate and 2-ethylhexyl acrylate as main constituent monomers.

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