JP2002254894A - Eraser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eraser which leaves no trace of handwriting failing to be effaced, when the erasion effect is visually checked, in the eraser of a thermoplastic elastomer. SOLUTION: This eraser contains at least a styrene thermoplastic elastomer, a filler and an acetylated glycerine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eraser for erasing a writing line written on a paper surface with a pencil or a mechanical pencil, or an image drawn with a plastic crayon or a colored pencil.

[0002]

2. Description of the Related Art Conventionally, erasers are roughly classified into three types depending on the base material. The first is a vulcanized rubber-based eraser made by kneading and vulcanizing natural rubber or synthetic rubber with a sub, filler and softener. The second is a polyvinyl chloride-based eraser obtained by heating and molding a plastisol in which a polyvinyl chloride resin, a plasticizer, and a filler are mixed. The third is a thermoplastic elastomer-based eraser obtained by mixing a thermoplastic elastomer, a filler, a softening agent, and if necessary, a soft thermoplastic resin, and heat-molding the mixture without vulcanization.

[0003] Among these erasers, vulcanized rubber-based erasers have poor light resistance and their surfaces harden and do not disappear when exposed to sunlight. This is because the sub component, which is an essential component of the vulcanized rubber-based eraser, is easily degraded by light. The term “sub” is also called “substitute” or “factis” and is obtained by vulcanizing vegetable oil. As the eraser, those obtained by vulcanizing vegetable oils such as rapeseed oil, cottonseed oil, and soybean oil, which are called white sub, with sulfur chloride are mainly used. Since the sub is easily worn, it has an effect of making erased chips easily come out.

[0004] In contrast to vulcanized rubber-based erasers, polyvinyl chloride-based erasers have become the mainstream of erasers because of their good light resistance and good erasability. However, a polyvinyl chloride-based eraser has a remarkable effect on the performance of the temperature at the time of heat molding. For example, Japanese Patent Publication No. 32-8220 discloses a method for producing an eraser in which 80 to 160 parts by weight of a plasticizer is added to 100 parts by weight of a vinyl chloride paste resin and heated at a relatively low temperature to cause low gelation. It has been disclosed. DOP (di-2-ethylhexyl phthalate) as plasticizer
And BPBG (butylphthalylbutyl glycolate) are disclosed, and it is disclosed that 125 to 135 ° C. is suitable as a relatively low temperature.

On the other hand, a thermoplastic elastomer-based eraser has good light resistance, does not require precise temperature control during heat molding, and can easily obtain a stable eraser. Furthermore, it is unvulcanized and has the advantage that the defective shape generated in the molding step can be reused because the influence of the temperature on the performance is small.

[0006] A styrene-based thermoplastic elastomer is known as a thermoplastic elastomer used for a thermoplastic elastomer-based eraser. As a thermoplastic elastomer-based eraser using a styrene-based thermoplastic elastomer, JP-A-63-195000 discloses a styrene-based thermoplastic elastomer such as styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-ethylenebutylene copolymer. Polymers and styrene-ethylene propylene copolymers are disclosed. In addition, Japanese Patent Laid-Open No. 1-1
Japanese Patent Application Laid-Open No. 05799 discloses that the styrene-based thermoplastic elastomer is a block copolymer of polystyrene at the molecular end, and that a two-block copolymer of polystyrene at only one end of the molecule can be used in combination.

[0007]

Since the thermoplastic elastomer eraser does not require a vulcanizing step or precise temperature control, the production method is simple and the defective shape product can be reused, but it is economical. Erasability is inferior to polyvinyl chloride eraser. JIS S 6050-1994
It is stated that the erasing ability (erasing rate)% of the 2.2 performance must be 80% or more. The test method for determining the erasure rate is described in 4.4 Erasing capacity (erasure rate) of the JIS, but a 0.5 kg weight is placed on an eraser of a specified shape, and four reciprocating rubs are performed. I have. According to this test method,
The thermoplastic elastomer-based eraser also satisfies the erasure rate of 80% or more, similarly to the polyvinyl chloride-based eraser. However, when actually used, a handwriting residue is recognized by visual judgment as compared with a polyvinyl chloride-based eraser. That is, the polyvinyl chloride-based eraser cannot visually recognize handwriting other than the dent on the paper surface, whereas the conventional thermoplastic elastomer-based eraser can slightly recognize handwriting.

It is an object of the present invention to provide a thermoplastic elastomer eraser which does not cause any handwriting to be erased by visual confirmation of erasability.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is an eraser containing at least styrene-based thermoplastic elastomer, filler and acetylated glycerin.

The details will be described below. As the thermoplastic elastomer-based eraser in the present invention, various thermoplastic elastomers such as an olefin-based thermoplastic elastomer, a urethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, and a vinyl chloride-based thermoplastic elastomer can be used. Indispensable thermoplastic elastomer. The styrene-based thermoplastic elastomer is a block copolymer having polystyrene which is a molecular constraint component (hard segment) for preventing plastic deformation in the molecule and an elastic rubber component (soft segment). The molecular structure includes a linear type, a side chain type, and a radial type.

As the styrene-based thermoplastic elastomer, specifically, as a styrene-butadiene copolymer in which the rubber component is butadiene, tufprene A and tufprene 12 are used.
5, 200, 315, 912, Solprene T-4
06, T-411, T-414, T-475, Asaprene T-420, T-430, T-431, T-450 (all manufactured by Asahi Kasei Corporation), Clayton D- 1101, D-1102, D-1155, D
-KX405, D-KX408, D-KX410,
D-KX414, D-KX415, D-111
6, D-1118, D-1184, D-1122
X, D-4270 and D-4271 (both manufactured by Clayton Polymer Japan KK) and the like.

Clayton D-1107, which is a styrene-isoprene copolymer whose rubber component is isoprene;
-1112, D-1113, D-1117, D-
1119, D-1124, D-1161, DK
X401, D-KX406, and D-KX603 (all manufactured by Clayton Polymer Japan Ltd.) and the like.

Examples of styrene-isoprene copolymers in which the rubber component is vinyl isoprene include Hybler 5127, 5125 and 7125 (all manufactured by Kuraray Co., Ltd.).

Tuftec L515, H1062, and H10 are styrene-ethylenebutylene copolymers in which the rubber component is ethylene butylene obtained by hydrogenating butadiene.
52, H1141, H1041, H1053, H1043, H1272 (above, Asahi Kasei Corporation)
Manufactured), Clayton G1650, G1651, G16
52, G1654X (all made by Clayton Polymer Japan KK), Septon 8004, 8006, 8
007 (all manufactured by Kuraray Co., Ltd.).

As a styrene-ethylene propylene copolymer in which the rubber component is ethylene propylene obtained by hydrogenating isoprene, Kraton G1730 (manufactured by Kraton Polymer Japan KK), Septon 2002, and 200
5, 2006, 2007, 2043, 206
3, 2104 (all made by Kuraray Co., Ltd.) and the like.

Septons 4033, 4055, and 4077 (all manufactured by Kuraray Co., Ltd.) are examples of styrene-ethylene-ethylene-propylene copolymers in which isoprene is hydrogenated ethylene and ethylene propylene.

As a styrene-butadiene butylene copolymer in which the rubber component is butadiene and butylene selectively hydrogenated, Tuftec P JT-83 and JT-82 (all manufactured by Asahi Chemical Industry Co., Ltd.) can be mentioned. .

As a special styrene-based thermoplastic elastomer, there is a two-block copolymer in which a molecular constraint component and a rubber component are each composed of one block. Clayton G1657 (containing 30% of a two-block copolymer) and G1726 (containing 70% of a two-block copolymer) as styrene-ethylenebutylene 2-block copolymer containing rubber as ethylene butylene (Clayton Polymer Japan Ltd.) Co., Ltd.). As a styrene-ethylene propylene diblock copolymer in which the rubber component is ethylene propylene, Kraton G1701 (above, manufactured by Kraton Polymer Japan Co., Ltd.), Septon 1001, and 10
50 (all manufactured by Kuraray Co., Ltd.).

As a styrene-based thermoplastic elastomer modified with maleic anhydride, Clayton FG1901X (manufactured by Clayton Polymer Japan Co., Ltd.) as a maleic anhydride-modified styrene-ethylenebutylene copolymer having a rubber component of ethylene butylene; Tuftec M1
943, M1911, and M1913 (all manufactured by Asahi Kasei Corporation). These styrene-based thermoplastic elastomers may be used alone or in combination of two or more, and may be used in combination with another thermoplastic elastomer or a soft thermoplastic resin.

The filler used in the present invention may be a filler conventionally used for an eraser. Specifically, heavy calcium carbonate, light calcium carbonate, colloidal calcium carbonate, diatomaceous earth, silica sand, silica, silicate compounds, shell powder, magnesium carbonate and the like can be used. These fillers may be used alone or in combination of two or more.

The acetylated glycerin in the present invention includes glycerin acetate and acetylated glyceride. Specific commercial products include triacetin (component glyceryl triacetate) (Daichi Chemical Co., Ltd.)
Manufactured), Riquemar PL-004, PL-012, P
L-012G, PL-014, Poem G-002 (component glycerin diacetomonolaurate), Poem G-038 (component glycerin diacetomonooleate), Poem G-508 (component glycerin monoacetomonostearate) (Both manufactured by Riken Vitamin Co., Ltd.). These acetylated glycerins can be used alone or
More than one species may be used in combination. Acetylated glycerin improves erasability in combination with a styrene-based thermoplastic elastomer. However, if the added amount is too large, erased debris sticks to the paper surface, so that the total amount of the thermoplastic elastomer and the resin is 30 parts by weight. It is desirable to use not more than parts by weight.

In addition, in the present invention, conventionally known softeners, stabilizers, antioxidants, coloring agents and the like can be used as the thermoplastic elastomer eraser. In particular, a softener is not necessary for a hard and rigid eraser such as a thin shape or a long shape, or may be added in a very small amount, but when a large amount is added to a soft eraser such as a commonly used office eraser. There is important. JP-A-5-124391 discloses that a petroleum-based oil is added to a styrene-based thermoplastic elastomer.
Japanese Patent Application Laid-Open No. H05-305, discloses an eraser used in an amount of up to three times.
No. 147392 discloses an eraser in which polybutene having a kinematic viscosity of 1000 cSt (40 ° C.) or less is used in an amount of 1 to 3 times the amount of a styrene-based thermoplastic elastomer. Conventionally known softeners usable in the present invention include liquid paraffin, mineral oils such as process oils and extender oils which are mixtures of paraffinic hydrocarbons and naphthenic ring hydrocarbons, liquid polybutenes and liquid α-olefin oligomers. And liquid ethylene-α-olefin oligomers.

[0023]

[Function] It is not clear why the combined use of a styrene-based thermoplastic elastomer and acetylated glycerin improves the erasability in a thermoplastic elastomer eraser. However, acetylated glycerin has a weak affinity for the styrene block of the styrene-based thermoplastic elastomer. It is presumed that graphite constituting the handwriting of a pencil or a mechanical pencil, or coloring pigment constituting the image of a plastic crayon or a colored pencil, easily adheres to the styrene block.

Hereinafter, the present invention will be described in more detail with reference to examples. “Parts” in Examples and Comparative Examples indicates “parts by weight”. Example 1 Mirastomer 3070N (olefin-based thermoplastic elastomer, manufactured by Mitsui Chemicals, Inc.) 25 parts Clayton G1650 12.5 parts Clayton G1726 12.5 parts IRGANOX1010 (stabilizer, manufactured by Ciba Geigy, Germany) 1 part Heavy calcium carbonate (Average particle size: 1.25 μm) 150 parts Triacetin 10 parts
6. Kneading is performed sufficiently while adding Grayton G1650 and Mirastomer 3070N in this order. After sufficiently kneading, the above-mentioned thermoplastic elastomer mixture kneaded on two rolls, heavy calcium carbonate, liquid paraffin,
Continue kneading while adding triacetin little by little. After adding all of them, kneading is further performed sufficiently. A sufficiently kneaded product is press-formed at 120 ° C. for 5 minutes in a mold made so that a sheet having a thickness of 10 mm can be formed.
An eraser having a thickness of 0 mm was obtained.

Example 2 Septon 2002 25 parts Septon 4055 20 parts Clayton FG1901X 5 parts IRGANOX1010 (stabilizer, manufactured by Ciba Geigy, Germany) 1 part Heavy calcium carbonate (average particle size 10.5 μm) 350 parts Liquid paraffin 95 parts Liquemar PL-012 5 parts An eraser was obtained in the same manner as in Example 1 except that the temperature of the two rolls was 150 ° C and the press temperature was 50 ° C.

Comparative Example 1 An eraser was obtained in the same manner as in Example 1 except that triacetin was not added. Comparative Example 2 An eraser was obtained in the same manner as in Example 2 except that liquemar PL-012 was not added.

[0027]

The erasers obtained in the above Examples 1 and 2 and Comparative Examples 1 and 2 are used in accordance with JIS S6050-1994.
The erasing rate was measured by the method of 4.4 Erasing ability (erasing rate), and the following results were obtained. Example 1 Erasure rate 89% Example 2 Erasure rate 92% Comparative example 1 Erasure rate 82% Comparative example 2 Erasure rate 85%

The erasers obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were 10 mm thick, 16 mm wide and 45 mm long.
Into a block-shaped eraser. JIS S6050-1994, except that the pencil was changed to a mechanical pencil (core diameter 0.5 mm, core hardness HB, high polymer 100, manufactured by Pentel Co., Ltd.), and the object pitch was set to 2 mm or more so that handwriting did not overlap. A colored paper was produced in the same manner as in the 4.4 Erasing ability (erasing rate) test.

Holding the block-shaped eraser by hand,
The handwriting of this colored paper was rubbed back and forth four times to perform an erasing operation.
After visually checking the handwriting on the colored paper after the erasing work,
In Examples 1 and 2, no dents were found except for the dents in the handwriting, but in Comparative Examples 1 and 2, it was recognized that the dents in the paper were slightly colored in black.

As described above, the eraser according to the present invention was such that, in an actual use condition, similarly to the polyvinyl chloride eraser, handwriting disappeared slightly by visual confirmation of the erasability.

Claims (1)

[Claims] 1. An eraser containing at least a styrene-based thermoplastic elastomer, a filler and acetylated glycerin.