JPS5915991B2 - Method for manufacturing seamless hollow bodies by electroforming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a seamless hollow body by electroforming, and in particular, a seamless hollow body is produced by using an elastic urethane oligomer hollow body as a matrix for electroforming. This relates to a method of manufacturing by electroforming.

Conventionally, in order to manufacture, for example, a hollow cylindrical solid by electroforming, a split mold is combined as a mother mold for electroforming, the inner surface is made conductive, and then electroforming is performed, or the outer surface of the cylinder is made conductive. However, in the former method it is unavoidable that seams will occur, while in the latter method It is not possible to obtain a clear surface pattern, which is undesirable in terms of aesthetics and dimensions, and the method is laborious, limiting the range of use. The present invention provides a method for manufacturing a seamless hollow body by electroforming, which eliminates various drawbacks of the hollow body manufacturing method by electroforming, and in which a mother mold for electroforming can be repeatedly used for a long period of time.

The present inventor has developed an elastic polymer material, for example, by using a hollow cylindrical body as a matrix, imparting conductivity to the inner wall surface, electroforming it to a predetermined thickness, and then heating or mechanically forming it. It was confirmed that the electroformed product could be easily pulled out from the cylindrical matrix, and as a result of various research into polymeric materials, the present invention was completed.

5 The gist of the present invention is to mold a hollow cylindrical body, a hollow polygonal column, or a hollow electroforming matrix having a similar shape from an elastic urethane oligomer with a medium degree of polymerization, and After electroconductivity is imparted to the hollow inner or outer surface of the mold by a conventional method and electroforming is performed to a predetermined thickness, the electroformed metal body is pulled out from the hollow electroforming mother mold.

That is, a hollow cylindrical body or the like is molded from an elastic urethane oligomer with a medium degree of polymerization by a casting method using a prototype of an electroformed product, and the hollow inner surface 5 or outer surface of the molded body is made of a known conductive material. Conductivity is imparted by silver mirror treatment using a spray method, electroforming is performed to a predetermined thickness, and the electroformed product is pulled out using the elasticity of the urethane oligomer matrix.

The elastic urethane oligomer is preferably a medium-polymerized synthetic leather (degree of polymerization 2000 to 3000), such as butylene diisocyanate or tolylene diisocyanate, 1,4-butanediol, 116-
Add equimolar amounts of 15 types of polyols selected from hexanediol, propylene glycol, etc., and add amines such as toluylene diamine and triethanolamine.
Adding 0.1 to 0.3 parts as a catalyst to the mixture,
Cure and solidify at relatively low to - temperature, but in order to have plasticity, vegetable oil (preferably vegetable oil having a hydroxyl group in the fatty acid group) or (.) is a higher alcohol with a relatively large number of carbon atoms in the alkyl group, such as cetanol. The following are added in place of some of the above-mentioned polyols.

In this case, it is necessary to reduce the amount of polyol depending on the amount of hydroxyl groups in the vegetable oil and higher alcohol. By leaving the above mixture at room temperature for 4 to 5 hours, the desired elastic urethane oligomer with a medium degree of polymerization can be obtained. In addition to vegetable oil and higher alcohol, polyethylene glycol and polypropylene glycol also have similar effects. Hereinafter, embodiments of the present invention will be described based on the drawings (・
To explain this, FIG. 1 is a vertical cross-sectional view and a cross-sectional view of a master mold made of metal or an appropriate material, and a fine pattern 2 is engraved on the surface of the cylindrical master mold 1.

Figures 2A and 2B are longitudinal and cross-sectional views after casting and curing the above-mentioned urethane polymer mixture using mold 1 as a core material, and Figure 3 shows the mold being pulled out from urethane oligomer 3. In later longitudinal and cross-sectional views, on the inner surface of the hollow matrix 3 made of urethane oligomer 1, a pattern 2', which is the pattern of the original pattern with the convexes and convexes reversed, is imprinted.
Figure 4 A and the opening are longitudinal and cross sectional views of the state in which electroforming has been performed after forming a conductive thin layer on the inner surface of the matrix 3, and Figure 5 A and the opening are the matrix. The figure shows a vertical cross-sectional view and a cross-sectional view of the electroformed metal body 4 after being drawn out from the electroformed metal body 4, and the pattern 2 of the prototype 1 is accurately reproduced on the surface of the electroformed metal body 4. The above explanation was given for the case of electroforming on the inner wall surface of a hollow cylindrical electroforming mother mold. The outer surface is made conductive and electroformed, and after humidifying the mother mold, a plug is attached to one side of the hollow open end of the mother mold, and pressurized air is sent from the end of the mother mold on the plugged side, and the elasticity of the mother mold The pressurized air that has entered between the electroformed surface of the mold and the electroformed metal body causes the electroformed metal body to peel off from the mother mold.
A centripetally compressed master mold is extruded from the electroformed metal body.

In this way, a seamless hollow electroformed body having a pattern or the like on the inner surface can be obtained. As a method for imparting conductivity to the matrix, known methods such as chemical plating, silver mirror reaction, and metal powder smearing methods can be applied.In the case of silver mirror reaction, the surface of the hollow body can be easily made to a silver mirror surface by spraying. It is also economical when large quantities are processed.

According to the present invention, the master mold or electroformed product can be held in the matrix due to the appropriate hardness, tensile strength, and elasticity of the urethane oligomer with a medium degree of polymerization. In addition, it has almost no shrinkage, has good dimensional stability, and can be easily pulled out from the mother mold by heating or mechanically, resulting in a seamless, beautiful replica electroformed product of the original model. In addition, the mother mold made of urethane oligomer has excellent corrosion resistance against electroforming baths and can withstand repeated use over a long period of time. By the method of the present invention, hollow cylinders, polygonal prisms, or similar shapes, such as polygons or ellipses with irregular cross sections, tapered cylinders, and cap-shaped bodies with one end of the cylinder closed. It can be widely applied to objects with removable shapes such as hollow cylindrical bodies, such as lighters, cosmetic containers, fountain pens, etc.
It can be used for manufacturing prongs, industrial pipes, etc.

The present invention will be further explained below with reference to Examples and Comparative Examples. Example 0.3 mol (36.6 t) of 1.4-hexanediol was added to 0.3 mol (51.5 f) of butylene diisocyanate, 0.3 t of triethanolamine was added, and 15 V of vegetable oil was added and mixed. The mixture was cast using a cylindrical prototype having a fine pattern on its surface as a core, cured at room temperature for 5 hours, and after curing, the prototype was pulled out to obtain a hollow cylindrical master mold.

After cleaning the mother mold, a silver nitrate solution (10% by weight solution) was precipitated with an ammonia aqueous solution, and the dissolved solution and formalin were simultaneously sprayed to form a silver mirror on the inner surface of the mother mold. The above electroforming mother mold was electroformed to a predetermined thickness using an electroforming bath of nickel, copper, silver, gold, etc.

When pulling out the electroformed product from the mother mold, the mother mold was heated and the product could be easily pulled out. The products had a beautiful appearance, and each replicated electroformed product with a clear surface pattern was obtained. In order to test the corrosion resistance of the electroforming mother mold, it was immersed in an electroforming bath for 96 hours. During this period, the temperature of the electroforming solution was 70 to 80°C, and no signs of attack by strong acidic or strong alkaline chemicals were observed. It also withstood repeated use for two months as an electroforming mother mold. Comparative Example A silicone resin matrix using the same prototype as in the example, and an epoxy resin matrix in which dibutyl phthalate, ethylene glycol, and glycidyl ether of butylene glycol were added to a pisphenol type epoxy resin (trade name: Epicote 828). were each molded and immersed in the same electroforming bath and conditions as in the example.

The silicone resin matrix deteriorated significantly after 72 hours, and the epoxy resin matrix deteriorated significantly and lost its elasticity after 92 hours.

The temperature of these electroforming operations is relatively high at 70 to 80°C (・
This is thought to be because the solution is strongly acidic or alkaline.

[Brief explanation of drawings]

Figure 1 A, opening to Figure 5 A, opening respectively represent the master mold, the master mold after urethane oligomer casting, the master mold after drawing out the master mold, the electroformed state of the master mold, and the vertical cross-sectional view of the electroformed metal body. A cross-sectional view is shown. 1...Prototype, 2,2'...Surface pattern,
3... Urethane oligomer single matrix, 4...
・Electroformed metal body.

Claims (1)

[Claims] 1. Hollow electroforming into hollow cylinders, hollow polygonal columns, or similar shapes using elastic urethane oligomers with a degree of polymerization of 2,000 to 3,000 obtained by reacting diisocyanates, polyols, and vegetable oils or higher alcohols with relatively long alkyl groups. After molding a mother mold for hollow electroforming, imparting conductivity to the hollow inner surface or outer surface of the mother mold by a conventional method and performing electroforming to a predetermined thickness, the electroformed metal body is molded into the hollow electroforming mold. A seamless hollow body that can be pulled out from a mold.
A method of manufacturing by electroforming.