JPH03122155A - Stamp material - Google Patents

Abstract

PURPOSE:To obtain a readily carved stamp material, composed of a methyl methacrylate polymer composition containing a specific amount of aluminum hydroxide, capable of providing a sharp carved stamp and excellent in spread of a vermilion inkpad without breakage and abrasion even in use or a long period. CONSTITUTION:A stamp material composed of a methyl methacrylate polymer composition, obtained by a method for mixing (A) a polymerizable syrup, containing methyl methacrylate monomer and optionally a low-molecular weight methyl methacrylate prepolymer, as necessary, other copolymerizable monomers (e.g. vinyl acetate or styrene) and/or a pigment and having preferably 20-100 cP viscosity (at 25 deg.C) with (B) aluminum hydroxide having preferably <=0.05 wt.% Fe2O3 content with a high whiteness degree and 30-80mu average particle diameter in an amount of 40-85 wt.% based on the total weight of the composition, carrying out polymerization, etc., and containing 40-85 wt.% aluminum hydroxide.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a stamp material formed from a synthetic resin composition.

In particular, it relates to a stamp material formed from a methyl methacrylate polymer composition.

[Conventional technology] Since ancient times, stamp materials have been made of natural materials such as wood such as psyllium; metals such as gold, silver, and platinum; stones such as crystal, agate, and jade; and animal materials such as ivory and buffalo horn. has been widely used. However, these natural materials are not easy to obtain and are expensive due to their small production volumes, so in recent years various printing materials have been developed to replace these natural materials.
It has been put into practical use.

Among the natural materials mentioned above, ivory has various excellent properties as a seal, but from the perspective of protecting the endangered African elephant, import bans from the country of origin have been internationally decided. (obtainable under the current situation); is becoming increasingly difficult.

Various plastic stamp materials have been developed and put into practical use as artificial stamp materials to replace the above-mentioned natural materials such as ivory, and thermoplastic resins are often used as the plastic in such cases. However, such conventional plastic stamp materials are generally soft and wear out with long-term use, causing the stamp to become unclear, and are still not fully satisfactory in terms of weight, feel, color, gloss, etc. Furthermore, when engraving a plastic stamp material, especially a stamp material made of thermoplastic resin, by machine, it has various drawbacks such as plasticization and softening due to the frictional heat generated when the chisel rotates at high speed, making engraving impossible. . Therefore, in order to improve such defects during engraving, 0.5 to 25% of an inorganic substance consisting of calcium hydroxide, shirasu, mica, and calcium carbonate was mixed into the thermoplastic resin stamp material for mechanical engraving. It has been proposed to prevent resin from softening due to frictional heat during mechanical engraving (Utility Model Application No. 52-27317,
Utility Model Application No. 52-27318, Utility Model Application No. 52-49373 and Utility Model Application No. 52-49374). However, in the case of these stamp materials, there are cases where a complete stamp is not formed due to chipping during engraving, and they are still unsatisfactory in terms of weight, feel, color, gloss, etc. It cannot be made into a certain color.

[Contents of the Invention] From this point of view, the present inventors have continued various studies with the aim of artificially obtaining a stamp material comparable to natural materials such as ivory, which does not have the above-mentioned defects. As a result, among the many thermoplastic resins, methyl methacrylate polymer meets the above purpose, and in particular, a material in which methyl methacrylate polymer contains a certain amount of aluminum hydroxide is easy to engrave and does not chip. The engravings obtained are clear and will not become blurred or disappear due to wear even after long-term use.In addition, the vermilion paste has good adhesion, and the weight, feel, color, gloss, etc. It has been found that the material is excellent and extremely suitable as a printing material.

Accordingly, the present invention provides methyl methacrylate polymer compositions containing 40-85% aluminum hydroxide, where the amount of aluminum hydroxide is based on the total weight of the composition.
This is a stamp material made from.

Here, the methyl methacrylate polymer in the present invention refers to a methyl methacrylate homopolymer made only of methyl methacrylate monomers and a methyl methacrylate copolymer obtained by copolymerizing methyl methacrylate monomers with other copolymerizable polymers. It could be any of them. In that case, copolymerizable monomers include α, β-ethylenically unsaturated compounds such as vinyl acetate, styrene, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, ethyl acrylate, butyl methacrylate, and cyclohexyl acrylate. One or more of these copolymerizable polymers may be copolymerized with a methyl methacrylate monomer. Such copolymerizable monomers are generally used in amounts less than about 10% based on the total weight of the polymerizable monomer.

The content of aluminum hydroxide is from 40% to 40% based on the total weight of the methyl methacrylate polymer composition as described above.
It is necessary that it be 85%.

If it is less than 40%, it will be inferior in terms of appearance such as color and gloss, weight, feel, etc. If it is more than 85%, the physical properties of the stamp material itself will lose its stickiness, and it will chip during engraving and have poor workability. In addition, mechanical strength such as impact resistance decreases, making it easier to break.

In addition, aluminum hydroxide has Fe, O, content of 0
．． A high whiteness of 0.05% by weight or less is preferable; if the iron content increases, the stamp material will take on a yellow or reddish tinge, making it difficult to color it to the desired color tone with other pigments.

In addition, aluminum hydroxide with an average particle size of about 30 to 80 microns is easy to handle because it is difficult for aluminum hydroxide particles to aggregate with each other, and it is easy to add a large amount to the methyl methacrylate monomer raw material. It has good dispersion stability (sedimentation prevention) in the raw material, and it becomes a printing material with a good translucent color tone. Furthermore, if aluminum hydroxide contains organic substances, the color tone may change during or after the printing material is manufactured.
This is not desirable as it may change the gloss etc.

In the present invention, the inorganic substance contained in the methyl methacrylate polymer must be aluminum hydroxide as described above, and when aluminum oxide (alumina) is used instead of aluminum hydroxide, Despite being a compound, it is completely opaque, flat white, and does not have a deep, translucent ivory-like tone, luster, or texture. Furthermore, when calcium carbonate is used as the inorganic substance, the color becomes completely opaque and has no depth, and the acid resistance and stain resistance are poor.

In addition, in the present invention, other pigments (for example, various metal oxides) can be contained in addition to aluminum hydroxide as necessary, as long as they do not adversely affect the properties of the stamp material. In addition to color, white, black, red,
It can be colored in any color such as yellow, blue, or green.

The printing material of the present invention is usually prepared by mixing 40 to 85% of the aluminum hydroxide in a polymerizable syrup made of methyl methacrylate monomer or a polymerizable syrup containing a low molecular weight methyl methacrylate prepolymer dissolved in methyl methacrylate monomer. , can be produced by polymerizing this. In this case, it is preferable to keep the viscosity of the polymerizable syrup at about 20 to 100 centipoise (25 DEG C.) from the viewpoint of preventing aluminum hydroxide from settling and uniformly dispersing it during polymerization.

When using a polymerizable syrup containing methyl methacrylate prepolymer dissolved in methyl methacrylate monomer, the methyl methacrylate monomer can be dissolved by dissolving the methyl methacrylate prepolymer prepared in advance in the methyl methacrylate monomer. The polymerizable syrup can be produced by polymerizing until the desired viscosity is reached and then immediately stopping the polymerization.

Any of the above polymerizable syrups should contain not only the methyl methacrylate monomer, methyl methacrylate prepolymer and aluminum hydroxide, but also the other copolymerizable monomers and/or other pigments mentioned above as necessary. It is also possible to use a precopolymer of methyl methacrylate and other polymerizable heptamers as the methyl methacrylate prepolymer.

Furthermore, if necessary, the polymerizable syrup may contain polyunsaturated polymerizable monomers (crosslinking agents) such as ethylene dimethacrylate, propylene dimethacrylate, divinylbenzene, triallyl cyanurate, diallyl phthalate, etc. In that case, a crosslinked stamp material with improved heat resistance and hardness due to the aluminum hydroxide contained in the methyl methacrylate polymer is obtained.

The polymerization may be carried out using any method and catalyst system commonly employed in the polymerization of methyl methacrylate-based polymerizable syrups, for example, either heated polymerization or non-heated polymerization may be carried out. Examples of polymerization catalyst systems include heated catalyst systems that combine organic peroxides such as benzoyl peroxide and chain transfer agents such as mercaptan compounds and azoin butyronitrile; esters) and basic compounds (metal oxides,
hydroxide, carbonate, organic acid salt, etc.); organic peroxides such as methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, and cycloisane peroxide, and quaternary ammonium salts. Examples include a low-temperature polymerizable catalyst system consisting of:

Furthermore, the order of addition of aluminum hydroxide, catalyst system, etc. to the polymerizable syrup can be carried out in any manner.

Then, a methyl methacrylate polymer stamp material containing aluminum hydroxide is produced by placing the liquid polymerizable material containing polymerizable syrup and aluminum hydroxide into a mold and molding it simultaneously with polymerization. polymerization·
The molding can be carried out in such a way that a large block such as a plate is produced, and in that case, individual stamp materials are cut out from the obtained block to produce a stamp. Another method is to use a mold having mold cavities having the final dimensions and shape of the desired seal, and to perform polymerization by injecting a liquid polymerizable material into each of the mold cavities in one step. Seals may also be manufactured. In this case, if the inner surface of the mold cavity is mirror-finished, the obtained seal can be engraved and used as is without surface polishing or the like.

The stamp material of the present invention may be engraved by hand or by machine, and any conventional engraving method, instrument, or device may be used.

The present invention will be specifically explained below with reference to examples.
The invention is not limited thereby.

EXAMPLE Methyl methacrylate monomer polymerizable syrup containing dissolved 63% by weight of aluminum hydroxide (average particle size approximately 40 microns) and methyl methacrylate prepolymer (viscosity 45 centivoise: methyl methacrylate pre@polymer content 20% by weight) A mixture consisting of 37% by weight was heated to 30°C.
Mixed evenly. Add to this 2.0 pph of tertiary butyl peroxymaleic acid, then 0.6 pph of calcium hydroxide.
, 0.2I)l)h of water and 0.2pph of glycol dimercaptoacetate were added and mixed well, and the resulting mixture was injected into a mold cavity with an opening size of 300mm x 300mm and a depth of approximately 20mm, and was poured from the outside. A molded plate-shaped stamp material was produced by polymerizing the mixture as it was without heating.

The specific gravity of each plate obtained above was 1.75.

From this plate, an unengraved cylindrical seal (about 27 g) with a diameter of 18 mm and a length of 60 mm, and a cylindrical seal with a diameter of 15 mm and a length of 60 mm.
unengraved cylindrical seal (approx. 19g) and diameter 12mm
.

Each unengraved cylindrical seal (approximately 12 g) with a length of 60 mm was cut out.

Seals were manufactured by engraving the face of each seal obtained above using a common seal knife, and in all cases, the engraving could be carried out smoothly without any chipping. Moreover, the resulting engraved seal has a weight, color, luster, and feel comparable to that of a special eyeless ivory seal, and also has excellent vermilion paste.

[Effects of the Invention] The stamp material of the present invention is easy to engrave and does not chip.
The resulting markings are clear and will not become unclear or disappear due to wear even after long-term use. In addition, it has good mechanical properties such as impact resistance, so it is not easily damaged even if it is dropped or hit against other objects. Furthermore, the vermilion paste adheres well, and the weight, feel, color, and luster are excellent, making it comparable to high-quality ivory. In addition, by adding various pigments, it is possible to obtain a beautiful stamp colored in a desired color.

Claims (1)

[Claims] A stamp material formed from a methyl methacrylate polymer composition containing aluminum hydroxide, wherein the amount of aluminum hydroxide is from 40 to 85% based on the total weight of the composition.