JP4869406B2 - Erasing and manufacturing method - Google Patents

Description

  The present invention relates to an eraser using an elastomer and a manufacturing method thereof, and more specifically, a character using an elastomer that is low in dependence on fossil resources, can be recycled, is environmentally friendly, and is compatible with a recycling society. The present invention relates to an eraser and a manufacturing method thereof.

Until now, industries and economies have been developed through the use of fossil resources such as oil and coal, and social systems for mass production, mass consumption and mass disposal have been established. It depends.
The current social system has created economic affluence and convenience, but on the other hand, it emits waste and carbon dioxide that exceed the natural purification capacity, aggravating environmental issues such as global warming and harmful substances. ing.

  In order to solve such problems, we have produced a large amount of products from finite resources so far, consumed and discarded a large amount of this, modified the one-way social system to reduce the generation of waste, There is a strong demand for a transition to a recycling society that effectively uses limited resources. To form this recycling-oriented society, the Cabinet decided on the “Biomass and Nippon Comprehensive Strategy” in December 2002 and is working to rebuild industrial competitiveness.

  Biomass is a continuously renewable organic resource that comes from the bounty of nature. Biomass emits carbon dioxide when combusted, but absorbs and fixes carbon dioxide in the atmosphere by photosynthesis during growth, and therefore has a feature that it does not substantially increase carbon dioxide. This is called “Carbon Neutral”, and by replacing energy and products derived from fossil resources with biomass, it is possible to significantly reduce carbon dioxide emissions. Therefore, there is a strong demand for technology and product development.

In recent years, many proposals have been made for polymer materials in consideration of the formation of a recycling society.
For example, a rubber production composition comprising natural rubber and biodegradable plastic (in the examples, vulcanizing agent and vulcanization accelerator are used) (Patent Document 1), biodegradable material and epoxidized polyisoprene, and necessary A biodegradable material composition obtained by further mixing a cross-linking agent (Patent Document 2), a biodegradable rubber composition obtained by adding a biodegradable resin and a filler to natural rubber (Patent Document 3), crystals A polylactic acid-based resin composition (patent document 4) composed of a basic polylactic acid and a rubber component selected from natural rubber and polyisoprene, and a dispersed phase composed of natural rubber or the like is uniformly fine in a continuous phase composed of polylactic acid. Examples thereof include a dispersed polymer blend material (Patent Document 5).

On the other hand, the eraser can be broadly divided into three types: PVC eraser made of vinyl chloride resin, non-PVC eraser made of styrene thermoplastic elastomer or olefin thermoplastic elastomer, and natural rubber eraser.
Of these, PVC eraser and non-PVC eraser account for over 90% of the eraser market, and the polymer materials, plasticizers, and softeners that make up these are all materials derived from fossil resources such as petroleum. Continuing to use erasure goes against the purpose of creating a recycling-based society.
On the other hand, natural rubber eraser uses biomass such as sub (factis) produced from natural rubber or vegetable oil, and is consistent with the purpose of forming a recycling society (Patent Document 6, Non-patent) Reference 1).
JP-A-10-274494 JP 2000-95898 A JP 2000-319446 A JP 2003-183488 A JP 2004-143315 A JP 2000-43492 A (see Examples 1 and 2) "Rubber Industry Handbook" (new edition) edited by Japan Rubber Association Table 25.2, pages 817, November 15, 1973 Issued by Rubber Association of Japan

  However, in the above-mentioned prior art, the rubber that is not vulcanized or crosslinked does not have sufficient tensile strength and elasticity, so its use may be limited. For example, rubber erasing material does not exhibit rubber elasticity. It is not appropriate. On the other hand, vulcanized or cross-linked ones are limited in application because they have too high tensile strength and elasticity. For example, they are not suitable because they become hard as a material for erasing and cannot provide rubber elasticity. Furthermore, the vulcanization and cross-linking steps are necessary, which not only complicates the manufacturing process, but also concerns the safety of vulcanizing agents such as sulfur as a vulcanizing agent, vulcanization accelerator, and zinc oxide as an auxiliary agent. I am confused.

  On the other hand, as described above, natural rubber eraser is suitable for the formation of a recycling-oriented society, but, for example, its eraser performance is inferior to that of PVC eraser, and it includes a vulcanization process. Compared with PVC eraser, the manufacturing process is complicated, and as described above, there are problems in the safety of vulcanizing agents such as sulfur and vulcanization accelerators. Furthermore, it is uneconomical because it is difficult to reuse the scrap generated in the manufacturing process, and there is a problem in productivity.

  In order to solve the above-mentioned problems of the prior art, the present inventors have made a matrix made of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate (hereinafter referred to as PHBH)) produced from a microorganism. There has already been proposed an eraser comprising an elastomer in which crosslinked natural rubber particles are dispersed in an island shape (Japanese Patent Application No. 2007-290488, filed on Nov. 8, 2007).

  However, the eraser containing PHBH is recyclable, environmentally friendly, compatible with a recycling society, and excellent in safety, but the eraser performance is not always sufficient compared to PVC eraser. It includes the problem.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the elastomer used in the present invention is excellent in compatibility with the vinyl chloride resin. It has been found that the erasing performance can be improved, and the present invention has been achieved.
That is, according to claim 1 of the present invention, crosslinked natural rubber particles are formed in a matrix made of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate (hereinafter referred to as PHBH)) produced from a microorganism. An eraser containing an elastomer dispersed in a shape and a vinyl chloride resin is included.

  According to a second aspect of the present invention, the composition ratio of the repeating units of PHBH is poly (3-hydroxybutyrate) / poly (3-hydroxyhexanoate) = 80/20 or more and 99/1 or less (mol / mol). The contents of the eraser according to claim 1 are as follows.

  According to a third aspect of the present invention, the elastomer is such that PHBH, natural rubber, and a rubber cross-linking agent are kneaded at a temperature not lower than the melting temperature of PHBH and not lower than the cross-linking temperature of the rubber cross-linking agent, so The eraser according to claim 1 or 2, characterized in that particles are dispersed.

  Claim 4 of the present invention is an elastomer eraser composition wherein the elastomer is 50 to 99% by weight of natural rubber, 50 to 1% by weight of PHBH, and the rubber cross-linking agent is 0.1 to 5 parts by weight with respect to 100 parts by weight of natural rubber. The eraser according to any one of claims 1 to 3, characterized in that the content is an object.

  Claim 5 of the present invention further includes a softening agent, and the eraser according to claim 4 is characterized.

  Claim 6 of the present invention includes the eraser according to claim 5, wherein the softening agent is derived from biomass.

  Claim 7 of the present invention includes the eraser according to claim 5 or 6, wherein the softener is selected from animal and vegetable oils and plasticizers derived therefrom.

  Claim 8 of the present invention is that the softener is 1 to 200 parts by weight with respect to 100 parts by weight of the total of natural rubber and PHBH, according to any one of claims 5 to 7. The content is erase.

  The ninth aspect of the present invention further includes a filler, and the content of the eraser according to any one of the fourth to eighth aspects.

  Claim 10 of the present invention includes the eraser according to claim 9, wherein the filler is derived from biomass.

  The eleventh aspect of the present invention includes the eraser according to the ninth or tenth aspect, wherein the filler is selected from shell powder and eggshell powder.

  Claim 12 of the present invention is characterized in that the filler is 10 to 1000 parts by weight with respect to 100 parts by weight of the total of natural rubber and PHBH. The content is erase.

  Claim 13 of the present invention is that the vinyl chloride resin is a vinyl chloride resin eraser composition comprising 100 parts by weight of vinyl chloride resin and 60 to 180 parts by weight of a plasticizer. The contents of the erasure described in item 1.

  A fourteenth aspect of the present invention includes a method for manufacturing an eraser, characterized by melt-kneading and molding an eraser made of an elastomeric eraser composition and an eraser made of a vinyl chloride resin eraser composition. And

  According to a fifteenth aspect of the present invention, the elastomer eraser composition comprises 50 to 99% by weight of natural rubber, 50 to 1% by weight of PHBH, and 0.1 to 5 parts by weight of the rubber cross-linking agent with respect to 100 parts by weight of natural rubber. The eraser manufacturing method according to claim 14 is characterized in that.

  Claim 16 of the present invention is that the vinyl chloride resin eraser composition comprises 100 parts by weight of a vinyl chloride resin and 60 to 180 parts by weight of a plasticizer. Is the content.

  Claim 17 of the present invention is characterized in that the eraser made of an elastomeric eraser composition is 30 to 90% by weight, and the eraser made of a vinyl chloride resin eraser composition is 70 to 10% by weight. The manufacturing method of the eraser described in any one of 14 to 16.

The elastomer used in the present invention does not depend on fossil resources, and the material used as a raw material is natural rubber derived from biomass and PHBH, which is a biodegradable polyester plastic derived from biomass. It is an environment-adaptive elastomer that is decomposed in the natural environment without increasing carbon dioxide.
Therefore, the eraser made of the elastomer of the present invention and the vinyl chloride resin can reduce the burden on the environment as compared with the conventional vinyl chloride eraser. In the disposal stage, the vinyl chloride resin can be separated and recovered by biodegrading the elastomer in advance by means of compost or the like.

  In addition, since the elastomer used in the present invention is a thermoplastic elastomer, the end material produced at the time of molding can be easily recycled, so that the cost can be reduced and it is suitable for a resource recycling society.

  Since the elastomer used in the present invention is obtained by simultaneously kneading natural rubber and PHBH and crosslinking natural rubber, the process is simplified and the productivity is high. In addition, since a vulcanizing agent such as sulfur or zinc oxide or a vulcanization accelerator is not used for crosslinking natural rubber, safety is high.

Furthermore, while the conventional natural rubber eraser requires a cross-linking step separately from the kneading step, the elastomer used in the present invention is cross-linked simultaneously with the kneading, so the process is simplified and the productivity is high. .
In addition, conventional natural rubber eraser uses vulcanizing agents and vulcanization accelerators such as sulfur and zinc oxide, whereas the eraser of the present invention does not use such chemicals and is therefore highly safe. .

  Furthermore, the eraser of the present invention has a higher erase ability than conventional natural rubber eraser and non-vinyl chloride eraser.

The eraser of the present invention is characterized by containing an elastomer in which crosslinked natural rubber particles are dispersed in an island shape in a matrix made of PHBH and a vinyl chloride resin.
The eraser of the present invention may be formed by melt-kneading and molding an elastomer and a vinyl chloride resin together with additives such as a softener, a filler, a plasticizer, a colorant, and a fragrance, but comprises an elastomer eraser composition. Mixing the eraser and the eraser made of the vinyl chloride resin eraser composition and kneading them together is preferable because the eraser performance can be improved effectively. Therefore, it demonstrates along this preferable method below.

The elastomer used in the present invention has a sea-island structure in which crosslinked natural rubber particles are dispersed in an island shape in a matrix (sea) made of PHBH.
The natural rubber used in the present invention is classified into sheet rubber, pale crepe, brown crepe, blanket crepe, block rubber, crumb rubber, etc., depending on the method of processing from latex to solid rubber, but there are various rating grades, but these are not limited. There are no restrictions on the production area. In addition, natural rubber derivatives such as epoxidized natural rubber can be used. These may be used alone or in combination of two or more as required.

  PHBH used in the elastomer in the present invention is produced from microorganisms as described in JP-A-2007-77232, and the composition ratio of repeating units is poly (3) from the viewpoint of balance between flexibility and strength. -Hydroxybutyrate) / poly (3-hydroxyhexanoate) is preferably 80/20 or more and 99/1 or less (mol / mol). PHBH can change the melting point and crystallinity by changing the composition ratio of repeating units, and can change the physical properties such as Young's modulus and heat resistance. It is possible to have it.

  The composition ratio of natural rubber and PHBH may be appropriately determined depending on the intended use and physical properties of the elastomer composition. For example, as the eraser base material, natural rubber is 50 to 99% by weight, and PHBH is 50 to 50%. The range of 1% by weight is preferable, more preferably 70 to 95% by weight of natural rubber, and 30 to 5% by weight of PHBH. If PHBH is less than 1% by weight, the fluidity of the elastomer composition may be poor and there may be a problem in moldability. When PHBH exceeds 50% by weight, the elastomer composition becomes hard and rubber elasticity does not sufficiently develop, and there is a tendency that sufficient erasing performance is not exhibited.

  As the rubber cross-linking agent used in the present invention, an organic peroxide can be suitably used. Specifically, dicumyl peroxide (for example, Park Mill D manufactured by NOF Corporation), 2,5-dimethyl-2,5-di-t-butylperoxyhexane (for example, Perhexa 25B manufactured by NOF Corporation), di-t. -Butylperoxydiisopropylbenzene (for example, Perbutyl P manufactured by NOF Corporation), 2,5-dimethyl-2,5-di-t-butylperoxyhexine-3 (for example, Perxin 25B manufactured by NOF Corporation) and the like. . Other organic vulcanizing agents can also be used. Specifically, N, N'-m-phenylene dimaleimide (for example, Balunock PM manufactured by Ouchi Shinsei Chemical), p-quinone dioxime (for example, Balnock GM manufactured by Ouchi Shinsei Chemical), alkylphenol formaldehyde resin (for example, Taoka) And Tacchi roll 201) manufactured by Kagaku Corporation. These may be used alone or in combination of two or more as required.

  The rubber cross-linking agent is usually used in an amount of 0.1 to 5.0 parts by weight with respect to 100 parts by weight of natural rubber. If the rubber cross-linking agent is less than 0.1 parts by weight, the cross-linking is insufficient, and natural rubber does not become particles and the desired structure cannot be obtained. It tends to be too large and cause problems in formability.

  The elastomer eraser composition comprising PHBH, natural rubber, and rubber cross-linking agent as described above may further include a softener, a filler, a coloring material such as an organic / inorganic pigment, a dye, a fragrance, a stabilizer, an oxidation agent. Other additives such as an inhibitor, an ultraviolet absorber, a photodegradation inhibitor and an antifungal agent can be optionally added as appropriate.

  As the softener, mineral oil, animal and vegetable oil, or a plasticizer derived therefrom can be used. Specific examples of the mineral oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. Specific animal and vegetable oils include rapeseed oil, castor oil, cottonseed oil, linseed oil, soybean oil, sesame oil, corn oil, safflower oil, palm oil, coconut oil, peanut oil, wood wax, rosin, pine tar, tall oil, etc. . Examples of plasticizers derived from animal and vegetable oils include glycerin fatty acid esters, and specific examples include glycerin diacetate monolaurate, glycerin triacetate, and glycerol diacetate. These may be used alone or in combination of two or more as required. From the standpoint of providing a more environmentally adaptable elastomer composition, it is preferable to use a biomass-derived animal or vegetable oil or a plasticizer derived therefrom, which is a renewable resource.

  The blending amount of the softening agent is usually 1 to 200 parts by weight with respect to 100 parts by weight of the mixture of natural rubber and PHBH. The amount is preferably 10 to 150 parts by weight. If the amount of the softener is less than 1 part by weight, the amount of the softener added is not sufficient, while if it exceeds 200 parts by weight, bleeding may occur.

Fillers include heavy calcium carbonate, light calcium carbonate, silica, diatomaceous earth, magnesium oxide, titanium oxide, talc, sericite, quartz powder, montmorillonite, scallops, oysters, spotted shell powder, eggshell powder, organic hollow particles And inorganic hollow particles. These may be used alone or in combination of two or more as required. From the standpoint of providing a more environmentally adaptable elastomer composition, it is preferable to use shellfish powders such as scallops and oysters, oysters or eggshell powders that are generated in large quantities as waste.
The blending amount of the filler is usually 10 to 1000 parts by weight with respect to 100 parts by weight of the mixture of natural rubber and PHBH. Preferably it is 50-500 weight part. If the amount is less than 10 parts by weight, the effect of adding the filler is not sufficient. On the other hand, if the amount exceeds 1000 parts by weight, the composition becomes hard, sufficient rubber elasticity does not appear, and sufficient erasing performance tends not to be exhibited.

The elastomer eraser composition as described above can be obtained by kneading at a temperature higher than the melting temperature of PHBH and higher than the crosslinking temperature of the rubber cross-linking agent. Kneading is preferably performed under high shear, and examples of such a kneader include a twin-screw kneading extruder, a Banbury mixer, a pressure kneader, and a mixing roll. Of these, a twin-screw kneading extruder is preferably used.
The temperature higher than the melting temperature of PHBH is preferably 10 to 50 ° C. higher than the melting temperature of PHBH, and the temperature higher than the crosslinking temperature of rubber cross-linking agent is preferably a temperature 5 to 20 ° C. higher than the cross-linking temperature of rubber cross-linking agent.

  The elastomer eraser composition is molded by press molding, injection molding, extrusion molding, or the like, and cut into a predetermined dimension to be erased.

  On the other hand, the vinyl chloride resin used in the present invention is not particularly limited, and a known vinyl chloride resin is used, and either a paste resin or a straight resin may be used. A plasticizer is added to the vinyl chloride resin, and additives such as stabilizers, coloring agents, and fragrances can be optionally added as necessary.

  Examples of plasticizers include dioctyl phthalate (DOP), dinonyl phthalate (DNP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), ditridecyl phthalate (DTDP), and diundecyl phthalate (DUP). Examples include ester plasticizers; trimellitic acid ester plasticizers such as diisooctyl trimellitic acid (TIOTM); polyester plasticizers, and the like. These may be used alone or in combination of two or more as required.

  The plasticizer is added in an amount of 60 to 180 parts by weight, preferably 100 to 160 parts by weight, based on 100 parts by weight of the vinyl chloride resin. If the amount is less than 100 parts by weight, the composition becomes hard and sufficient erasing performance cannot be exhibited. On the other hand, if the amount exceeds 160 parts by weight, the plasticizer may migrate or bleed.

In the case of a paste resin, an erasing composition comprising the paste resin and a plasticizer and, if necessary, other additives is kneaded, defoamed, and poured into a molding die of a predetermined depth, for a predetermined time. After being heated, it is cooled, taken out from the mold, cut into a predetermined size, and erased.
On the other hand, in the case of a straight resin, an erasing composition composed of a straight resin and a plasticizer and, if necessary, other additives is molded by an injection molding machine, an extrusion molding machine, etc., and cut into a predetermined size. It will be erased.

  The eraser comprising the elastomer eraser composition obtained as described above and the eraser comprising the vinyl chloride resin eraser composition are weighed in a desired ratio, kneaded with a heated kneader, cooled and then ground. Then, it is formed into a pellet, molded by injection molding, extrusion molding, or the like, and cut into a predetermined size to make the eraser of the present invention.

  The mixing ratio of the eraser made of the elastomer eraser composition and the eraser made of the vinyl chloride resin eraser composition is not particularly limited, and the former elastomer is used when weight is put on the reduction of the burden on recycling and the environment. Increasing the rate of erasing, on the other hand, when placing weight on the erasing performance, it is sufficient to increase the rate of erasing of the latter vinyl chloride resin, but if the amount of erasing of vinyl chloride resin is small, the object of the present invention The improvement effect of erasing ability is reduced. Accordingly, the vinyl chloride resin eraser is preferably 70 to 10% by weight with respect to 30 to 90% by weight of the elastomer eraser, and more preferably the vinyl chloride resin eraser is 70 to 30% by weight of the elastomer eraser. -20% by weight. Even if the vinyl chloride resin eraser exceeds 70% by weight, the eraser performance is substantially constant, and the load on the environment tends to increase.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, these do not restrict | limit the scope of the present invention at all.

  The materials used in the following Reference Examples, Examples and Comparative Examples are shown in Table 1.

Reference Example 1: Manufacture of elastomer eraser Natural rubber, softener, filler and ultraviolet absorber among the materials shown in Table 2 are kneaded with a pressure kneader in advance, and a rubber cross-linking agent is added using a roll to rubber. A kneaded product was obtained. The obtained rubber kneaded product was cut into pellets of about 5 mm square. Next, rubber kneaded pellets and biodegradable plastic pellets are listed in Table 2 using a twin screw extruder KZW-15TW-60 (same direction complete meshing type, screw diameter 15 mm, L / D = 60) manufactured by Technobel. Each of them was supplied by a quantitative feeder so as to have the blending ratio shown, kneaded at a screw rotation speed of 400 rpm and a cylinder temperature of 110 to 155 ° C., and cut into 3 mm square pellets.
The pellets of the obtained composition were extruded into a square bar shape with a single screw extruder (cylinder temperature 100 to 120 ° C., head temperature 130 ° C.) and cut to produce an elastomer character (size 12 × 18 × 43 mm). .

As the erasing characteristics, hardness and erasing performance (erasing rate) were measured and evaluated. The results are shown in Table 2.
The hardness was measured in accordance with “JIS S 6050 Plastic Eraser” using a C-type hardness meter (Type C hardness meter manufactured by Kobunshi Keiki).
The erasure rate was measured by the following method.
(1) A sample was cut into a plate having a thickness of 5 mm, and a test piece was prepared by finishing a contact portion with a test paper into an arc having a radius of 6 mm.
(2) The test piece is brought into contact with the colored paper perpendicularly and at right angles to the colored line, and the weight is placed on the test piece so that the sum of the weight of the weight and the holder is 0.5 kg. The colored part was brushed back and forth four times at a speed of 150 ± 10 cm / min.
(3) Using a densitometer (DENITOMETER PDA65 Sakura), the density of the non-colored part of the colored paper was set to 0, and the density of the colored part and the wear part was measured.
(4) The erasure rate was calculated by the following formula.
Erase rate (%) = (1− (density of wear part ÷ density of colored part)) × 100

Reference Example 2: Manufacture of a vinyl chloride resin eraser As shown in Table 3, a vinyl chloride resin, a plasticizer, a filler and a stabilizer were mixed and stirred to obtain a paste sol. The obtained paste sol was vacuum degassed, then poured into a molding die (internal dimension: 100 × 100 × 10 mm) kept at 130 ° C., heated for 26 minutes, cooled, taken out from the die, and cut. A vinyl chloride resin eraser (size 10 × 18 × 43 mm) was produced.
The obtained erasing hardness and erasing rate were measured and evaluated in the same manner as in Reference Example 1. The results are shown in Table 3.

Examples 1-6
The elastomer eraser obtained in Reference Example 1 and the vinyl chloride resin eraser obtained in Reference Example 2 were mixed at a mixing ratio (weight basis) shown in Table 4, and the pressure kneader kept at 120 ° C. for 5 minutes. Kneaded. The obtained composition was cooled and then pulverized into pellets, extruded into a predetermined shape with a single screw extruder, and cut to create an eraser (size 12 × 18 × 43 mm).
The obtained erasing hardness and erasing rate were measured and evaluated in the same manner as in Reference Example 1. The results are shown in Table 4.

  As described above, since the eraser of the present invention uses an elastomer mainly composed of biodegradable PHBH and natural rubber, the dependence on fossil resources can be reduced, and even if discarded, the dioxide in the atmosphere can be reduced. In addition to increasing the amount of carbon, being friendly to the environment, and adapting to a recycling-oriented society, by using a vinyl chloride resin in combination, it is possible to provide erasing with excellent erasing ability. In the eraser of the present invention, the vinyl chloride resin can be separated and recovered by biodegrading the elastomer in advance at the stage of composting or the like at the disposal stage.

Claims (17)

  An elastomer in which crosslinked natural rubber particles are dispersed in islands in a matrix made of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate (hereinafter referred to as PHBH)) produced from a microorganism; An eraser characterized by containing a vinyl resin.   The composition ratio of repeating units of PHBH is poly (3-hydroxybutyrate) / poly (3-hydroxyhexanoate) = 80/20 or more and 99/1 or less (mol / mol), The erasure described in 1.   The elastomer is obtained by dispersing the crosslinked rubber particles in the matrix made of PHBH by kneading PHBH, natural rubber, and a rubber crosslinking agent at a temperature higher than the melting temperature of PHBH and higher than the crosslinking temperature of the rubber crosslinking agent. The eraser according to claim 1 or 2, characterized in that.   The elastomer is an elastomer eraser composition comprising 50 to 99% by weight of natural rubber, 50 to 1% by weight of PHBH, and 0.1 to 5 parts by weight of a rubber cross-linking agent with respect to 100 parts by weight of natural rubber. The eraser according to any one of claims 1 to 3.   The eraser according to claim 4, further comprising a softening agent.   6. The eraser according to claim 5, wherein the softening agent is derived from biomass.   The eraser according to claim 5 or 6, wherein the softener is selected from animal and vegetable oils and plasticizers derived therefrom.   The eraser according to any one of claims 5 to 7, wherein the softening agent is 1 to 200 parts by weight based on 100 parts by weight of the total of natural rubber and PHBH.   The eraser according to any one of claims 4 to 8, further comprising a filler.   The eraser according to claim 9, wherein the filler is derived from biomass.   The eraser according to claim 9 or 10, wherein the filler is selected from shell powder and eggshell powder.   The eraser according to any one of claims 9 to 11, wherein the filler is 10 to 1000 parts by weight with respect to 100 parts by weight of the total of natural rubber and PHBH.   The eraser composition according to any one of claims 1 to 12, wherein the vinyl chloride resin is a vinyl chloride resin eraser composition comprising 100 parts by weight of a vinyl chloride resin and 60 to 180 parts by weight of a plasticizer. .   A method for producing an eraser, comprising melting and kneading an eraser comprising an elastomer eraser composition and an eraser comprising a vinyl chloride resin eraser composition.   The elastomer eraser composition comprises 50 to 99% by weight of natural rubber, 50 to 1% by weight of PHBH, and 0.1 to 5 parts by weight of rubber cross-linking agent with respect to 100 parts by weight of natural rubber. The manufacturing method of the eraser described.   16. The eraser manufacturing method according to claim 14 or 15, wherein the vinyl chloride resin eraser composition comprises 100 parts by weight of a vinyl chloride resin and 60 to 180 parts by weight of a plasticizer.   The eraser comprising the elastomer eraser composition is 30 to 90% by weight, and the eraser comprising the vinyl chloride resin eraser composition is 70 to 10% by weight. The manufacturing method of the eraser as described in 2.