JPH0357123B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a plastic eraser with excellent strength and erasability. Traditionally, plastic erasers have been widely used due to their excellent erasing properties, but they are weaker than rubber erasers, and as a result, they have been made with smaller diameters, such as pencils with erasers and mechanical pencils with erasers. There was a problem that it could not be applied to the required eraser. To solve this problem, we have developed erasers made by mixing vinyl chloride resin, about twice the amount of vinylidene chloride, and about the same weight of plasticizer as the total amount of both resins, and heating and gelling the mixture, carborundum, Hard erasers such as so-called "sand erasers" are known, in which mineral powders such as alundum, diamond sand, glass powder, and silica sand are added to the resin. There is a problem that the elasticity is reduced, and the latter is only hard and brittle.
There was also the problem of damaging the paper surface. Therefore, the inventors of the present invention have conducted intensive research to develop a base material for plastic erasers, in order to solve the above problems, that is, to improve the strength and eraseability on par with conventional plastic erasers. It has been found that good results can be obtained when a polymerizable vinyl monomer containing two or more double bonds in one molecule is blended and heated to gel, especially when heated to gel in the presence of a polymerization initiator. Heading: This completes the invention. It is not clear why the present invention makes it possible to obtain a plastic eraser that is comparable in erasability to conventional plastic erasers and has improved strength, but it is possible to obtain a plastic eraser that is comparable in erasability to conventional plastic erasers and has improved strength. The monomer surrounds the
Strength is improved by having a weak network structure, and the strength of these bonds is moderately brittle against the force applied during erasing, so it is inferior in terms of erasability. It is assumed that there is no such thing. Next, the present invention will be explained in detail. The base material is mainly composed of a resin and a plasticizer, and other stabilizers, fillers, etc. are added as appropriate. Most of the resins used in known plastic erasers can be used, but polyvinyl chloride, polyacetic acid, etc. can be used in consideration of erasability, compatibility with other materials, stability during molding, etc. Vinyl and vinyl chloride-vinyl acetate copolymers are particularly preferred. The amount used is based on the total amount of erasers.
40-50% by weight is preferred. Examples of plasticizers include phthalic acid-based plasticizers such as dioctyl phthalate and dinonyl phthalate, adipine-based plasticizers such as dioctyl adipate, fatty acid-based plasticizers such as dioctyl azelate, and epoxy-based plasticizers such as epoxidized soybean oil, which is also used as a stabilizer. Plasticizers etc. are used. The amount used is preferably 30 to 50% by weight based on the total amount of the eraser. As the stabilizer, various metal salts such as potassium stearate and barium stearate, phosphorus stabilizers such as trinonylphenyl phosphate, etc. are used. The amount used is 5% for the total amount of eraser.
It is preferably less than % by weight. As the filler, inorganic fillers such as calcium carbonate, silicic acid, and talc are preferred. The amount used is preferably 10% by weight or less based on the total amount of the eraser, taking into account other materials. In addition, pigments, fragrances, etc. may be added as appropriate in addition to the above-mentioned materials. Next, let's talk about polymerizable vinyl monomers.
The polymerizable vinyl monomer has the above-mentioned effect,
It is presumed to improve the strength of the eraser,
It must contain two or more double bonds in one molecule, and specific examples include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and nonaethylene. Glycol dimethacrylate, tetradecyl ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, nonapropylene glycol dimethacrylate methacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate,
Methacrylates such as trimethacryl formal, tetramethylolmethanetetramethacrylate, and tetramethyloltrimethacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, laethylene glycol diacrylate, nonaethylene glycol diacrylate, and tetradecyl ethylene Glycol diacrylate, 1.3-butylene glycol diacrylate,
1.4-butylene glycol diacrylate, 1.6-
Hexane glycol diacrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, nonapropylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate, triacryl formal, tetramethylolmethane tetraacrylate Other monomers include triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, divinylbenzene, and the like. These monomers may be used alone or in appropriate combinations, and the amount used is preferably 1 to 100 parts by weight per 100 parts by weight of the base resin.
This is because if it is less than 1 part by weight, the strength may not be improved, and if it is more than 100 parts by weight, it may be difficult to separate the eraser from the paper surface. The monomers mentioned above can be polymerized alone or with a polymerization initiator.Individual polymerization is generally carried out by heating, but this is difficult because the possible monomers are limited and polymerization takes a relatively long time. More preferably, a polymerization initiator is used. Specific examples of such polymerization initiators include 2,2'-azoisobutyronitrile, acetylcyclohexylsulfonyl peroxide, di-
Isopropyl peroxydicarbonate, di-
2-ethylhexyl peroxydi-carbonate, 2,4-dicyclobenzoyl peroxide,
t-Butyl peroxy pivalate, 3.5.5-tri-methylhexanoyl peroxide, octanoyl peroxide, tecanoyl peroxide, lauroyl peroxide, propionoyl peroxide, succinic acid peroxide, acetyl peroxide, t -butylperoxy-2
-ethylhexanoate, benzoyl peroxide, t-butyl peroxyisobutyrate,
1.1'-bis-(t-butylperoxy)3.5.5-tri-methylcyclohexane, t-butylperoxymaleic acid, t-butylperoxylaurate, cyclohexanone peroxide, t-butylperoxyisopropyl carbonate, t -Butylperoxyacetate, di-t-butyldiperoxyphthalate, di-t-butylperoxy-di-isopropylbenzene, 2.5-dimethyl-
2.5-di(t-butylperoxy)hexane, di-t-butyl peroxide, di-iso-propylbenzene hydroperoxide, 2.5-di-
Methylhexane-2.5-dihydroperoxide, t-butyl peroxybenzoate, methyl ethyl ketone peroxide, dicumyl peroxide, t-butyl hydroperoxide,
Examples include 2.5-dimethyl-2.5-di(t-butylperoxy)hexane (3), p-menthane hydroperoxide, 1.1.3.3-tetramethylbutyl hydroperoxide, and these may be used alone or in appropriate combinations. . The amount of these polymerization initiators used is based on the polymerizable vinyl monomer.
0.1 to 10% by weight is preferable, and 0.1% by weight or less,
The polymerization reaction may become insufficient, and if it exceeds 10% by weight, foaming may occur and voids may be formed in the eraser, so neither is preferable. A plastic letter eraser can be obtained by uniformly mixing and stirring the above-mentioned materials at room temperature and then heating and molding. As the heat molding at this time, various methods such as casting, press molding, extrusion molding, and injection molding can be employed. The following description will be given with reference to Examples, where "parts" simply refer to parts by weight. Example 1 Formulation: PVC paste resin 100 parts Dioctyl phthalate 90〃 Dioctyl adipate 10〃 Trimethylolpropane trimethacrylate
30〃 Calcium carbonate 20〃 Calcium stabilizer 0.2〃 Pigment A little After stirring the homogeneous dispersion of the above composition at 130℃ for 3 hours,
An eraser was obtained by molding using an injection molding machine. The performance of this eraser was excellent as shown in Table 1. In addition, Comparative Example 1 is based on the formulation of Example 1,
This eraser was compounded and molded in exactly the same manner as in Example 1, except that 70 parts of 100 parts of the vinyl chloride paste resin was replaced with vinylidene chloride and the polymerizable monomer was omitted.

[Table] Example 2 Formulation: PVC paste resin 100 parts Dioctyl phthalate 80〃 Diaryl phthalate 20〃 Benzoyl peroxide (catalyst) 0.2〃 Calcium carbonate 30〃 Calcium stabilizer 0.2〃 Pigment A little A homogeneous dispersion of the above composition, An eraser was obtained by press molding at 120°C for 20 minutes. The performance of this eraser was excellent as shown in Table 2. Comparative Example 2 was conducted in the same manner as in Example 2, except that dioctyl phthalate was added instead of diallyl phthalate, the catalyst was removed, and 20 parts of the 30 parts of calcium carbonate were replaced with diamond sand. It is a molded eraser.

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Claims (1)

[Claims] 1. A polymerizable vinyl monomer containing two or more double bonds in one molecule is blended into a base material mainly composed of a resin and a plasticizer, and the polymerizable vinyl monomer is heated and gelled. A method for producing a plastic eraser, comprising polymerizing a vinyl monomer and forming the polymer into a network structure. 2. The method for producing a plastic eraser according to claim 1, which comprises heating and gelling it in the presence of a polymerization initiator.