JP2007154304A - Composition for precious metal clay - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extremely easily treatable pollution-free composition for precious metal clay which barely sticks to hand, has a moderate water-retention and stickiness, a strong adhesive strength, excellent moldability and a high dry strength, is hard to be cracked and can be re-kneaded. <P>SOLUTION: As a noble metal powder used for the composition for precious metal clay, the one subjected to surface treatment with higher fatty acid and/or a higher fatty acid salt is used, and, as a binder to be kneaded therewith, a glue-containing organic binder aqueous liquid or a curdlan-containing organic binder aqueous liquid is used. Into the organic binder aqueous solution, glue is incorporated preferably in the ratio of 0.1 to 5.0 wt.% by a solid content, and curdlan is incorporated preferably in the ratio of ≥1 wt.% by a solid content. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a precious metal clay composition useful as a shape material for producing a precious metal shaped article having a large craft element such as precious metal jewelry, arts and crafts, precious metal fixtures and the like.

When making precious metal shaped objects in the craft field, use a clay composition consisting of precious metal powder and a small amount of organic binder as a basic component, shape this into a desired shape, dry it, and then heat-sinter The binder composition is removed in the course of evaporation, decomposition, and combustion, and the particles of the noble metal powder are sintered together to produce the desired noble metal shaped article.

Generally used clay compositions for precious metal modeling are surface active agents as a mixing accelerator in a binder, and cellulose fibers and anti-adhesive agents for preventing the precious metal clay composition from adhering to the hands and becoming dirty. The fact is that several percent of phthalate-n-dibutyl, fats and oils and the like are blended (see Patent Documents 1 to 3).

However, even when cellulose fibers or the like are blended in the binder, when the hands are actually taken and kneaded, the precious metal clay composition adheres to the hands and cannot prevent the hands from becoming dirty.

At the same time, when such a precious metal clay composition is formed into a desired shape and fired, phthalate-n-dibutyl, which is a kind of environmental hormone and is said to be an endocrine disrupting substance, is formed, dried, and sintered. Because it diffuses into the atmosphere and pollutes the interior of the room, many people who enjoy cultural culture will be unable to avoid being eroded by inhaling the atmosphere.

Therefore, the present inventor has made it possible to provide a clay composition for precious metal modeling that is relatively easy to handle by combining a noble metal powder surface-treated with an organic acid salt of a higher aliphatic amine and an organic binder aqueous liquid. (See Patent Document 4). However, although this clay composition is easier to handle than the products described in Patent Documents 1 to 3, it does not completely prevent soiling of hands, and cracks after drying and re-kneading. There was a problem that it was difficult and sufficient strength could not be obtained.
JP-A-4-66605 JP-A-4-218603 Japanese Patent Laid-Open No. 10-212506 JP 2004-211163 A

The present invention eliminates such disadvantages of the prior art, is non-polluting, has almost no adhesion to the hand, has moderate water retention, stickiness, strong adhesive force, excellent formability, and has a dry strength. It is an object of the present invention to provide a noble metal clay composition that is strong, hardly cracked, and can be easily reworked.

In the present invention, noble metal powder fine particles used in a noble metal modeling clay composition obtained by kneading silver, gold, platinum, or other noble metal powder and an organic binder aqueous liquid, are surfaced with higher fatty acids and / or higher fatty acid salts. In addition, Nika is added to and mixed with an organic binder aqueous liquid at a ratio of 0.5 to 5.0% by weight in solid content to prevent agglomeration between fine particles and at the same time friction between fine particles. Improve the pure content of noble metal in the noble metal clay composition by reducing the coefficient and reducing the water content in the binder by reducing the amount of binder by maintaining a slight water repellency on the fine particle surface. At the same time, it is possible to reduce the shrinkage rate of the desired shaped object.

Further, in the present invention, in the noble metal molding clay composition obtained by kneading silver, gold, platinum or the like noble metal powder and an organic binder aqueous liquid, the noble metal powder fine particles used are higher fatty acid and / or higher fatty acid salt. In addition, an organic binder aqueous solution containing curdlan in a solid content of 1% by weight or more, preferably 5 to 95% by weight, particularly preferably 10 to 90% by weight is used. Therefore, it is possible to produce a molded article with excellent operability, excellent strength and quality after drying, and excellent precious metal luster.

The higher fatty acid (or higher fatty acid salt) used for the surface treatment of the noble metal powder fine particles in the present invention may be a fatty acid having 12 to 22 carbon atoms, and particularly preferably a fatty acid having 16 to 18 carbon atoms.

In the present invention, by adding a binder containing glue to a surface treated only with a higher fatty acid (or higher fatty acid salt) to obtain clay, an unprecedented product can be obtained. By performing the treatment in combination with a higher fatty acid (or higher fatty acid salt) and gum arabic, it is possible to provide a precious metal clay composition that is very easy to handle with little hand dirt during the molding operation. .

When the noble metal powder surface is combined with gum arabic and a higher fatty acid (or higher fatty acid salt), the gum arabic obtains a desired effect by adding about 500 ppm to 2000 ppm with respect to the higher fatty acid (or higher fatty acid salt). be able to.

In the present invention, it is possible to increase the strength of the product by adding Nika in the organic binder aqueous solution at a solid content of 0.1 to 5.0% by weight. In order to effectively prevent both stains, the amount of glue added to the organic binder aqueous liquid is preferably about 0.2 to 3% in terms of solid content.

As the binder in the present invention, any of the commonly used binders can be used. (A) Polyvinyl alcohol and cellulose binders (for example, hydroxymethylcellulose, sodium carboxymethylcellulose, ammonium carboxymethylcellulose, hydroxyethylcellulose, carboxymethylhydroxyethylcellulose, (B) a polycarboxylic acid (polyacrylic acid etc.), a polycarboxylic acid salt having a molecular weight of 1000 to 130,000, at least one of methylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxypropylcellulose, crystalline cellulose, etc. Blending at least one selected from the group consisting of polyoxycarboxylate and polyaminocarboxylate to produce a reaction Preferred to use a jelly-like thickening material having a three-dimensional structure.
When curdlan is used, only one type is useful as a binder. However, curdlan and agglomerates composed of components (A) and (B) are used in combination, particularly curdlan and cellulosic binder are used in combination. To achieve a very good effect

In such a binder, it is preferable that glue be added to and mixed with the component (A) in advance. In general, (A) a mixture of glue and at least one of polyvinyl alcohol and cellulose-based binder, and (B) a polycarboxylic acid, polycarboxylate, polyoxycarboxylate having an average molecular weight of 1000 to 130,000 And at least one selected from the group consisting of polyaminocarboxylates, and is preferably a jelly-like thickened product obtained by agglomeration, and in particular, the use of polyvinyl alcohol or hydroxypropyl cellulose as the component (A) Preferably, polycarboxylic acid or polycarboxylate is used as component (B).

The blending ratio of the component (A) and the component (B) in the binder is preferably about 1: 0.4 to 1:20, particularly about 1: 0.45 to 1:16 in terms of the effective component ratio. In addition, in the active ingredient in the binder aqueous liquid, the component (A) is preferably 5% by weight or more and 5 to 50% by weight, particularly about 10 to 30% by weight, and the component (B) is 10% by weight. As mentioned above, 10 to 100 weight% is preferable, and it is good especially about 15 to 80 weight%.

Furthermore, in the present invention, by adding glue to the binder, not only can the performance of the binder be improved, the clay can be made more stable and easy to handle, but also the strength of the clay can be increased. Nika is preferably blended with the component (A) in a solid content of about 0.2 to 6% by weight and mixed with the component (B) to form a binder aqueous liquid composed of a jelly-like thickening substance.

Moreover, in this invention, it becomes possible to improve the intensity | strength at the time of silver clay drying by mix | blending paper pulp in a binder. The blending ratio of the paper pulp to the binder is preferably about 0.01 to 5.0%, and particularly preferably about 0.5 to 3%. The blend of paper pulp does not adversely affect other properties and performance of the clay composition.

The binder composed of the components (A) and (B) used in the present invention alone has sufficient performance characteristics without adding a surface active agent, an oil and fat anti-tacking agent, etc. like conventional binders. In addition, the adhesive strength is strong, the moisture retention is good, and the creation time of the precious metal shaped article by the clay composition can be extended. It also has excellent long-term stability. Furthermore, even when kneaded with the surface-treated noble metal powder, there is almost no adhesion to the hand and the kneading condition is good.

In the present invention, by using a binder containing glue and a precious metal powder surface-treated with a higher fatty acid (or higher fatty acid salt), or by using a binder containing curdlan and the surface-treated precious metal powder, The following effects can be obtained in the noble metal clay composition.
1) Water in the clay can be reduced, the kneading condition can be improved, and natural drying during modeling can be delayed.
2) The strength of the clay after drying can be increased.
3) The degree of deformation after firing can be reduced.
4) Excellent long-term storage and stability.
5) Can prevent cracks and wrinkles during modeling work.
This effect is further enhanced by using a noble metal powder whose surface is combined with higher fatty acid (or higher fatty acid salt) and gum arabic. In this case, the gum arabic may be attached to at least a part of the surface of the noble metal powder treated with the higher fatty acid (or higher fatty acid salt).

Noble metal powder having an apparent density of 2.5 g / cm ³ or more, a specific surface area of 0.1 to 2.0 m ² / g, a 50% average particle size of 0.7 to 3 μm, 50 to 80% by weight, Further, by including 20 to 50% by weight of 50% average particle diameter of 3 to 8 μm, the shrinkage ratio after firing becomes very small.

The precious metal clay composition of the present invention has the following effects: (1) modeling is soft and easy to handle, (2) cracking is difficult, (3) re-kneading, (4) elongate even when elongated into a string shape, etc. In particular, when making silver clay texture (patterning on the clay surface), put the work gloves on your hands and hold the silver clay plate-like surface, and the texture of the work gloves is silver clay When it is attached to the surface, other commercial clays stick to the work gloves and cannot copy the pattern well, but with the product of the present invention, the work gloves can be separated smoothly and beautiful stitch patterns can be copied. In this way, the texture of the stamping mold is beautiful, the pattern remains clean, and the finish is clean. Further, for example, when a ring is made of silver clay and resized after firing, it extends from No. 8 to No. 15 and can be easily resized with good workability. Moreover, the shrinkage rate is very small.

Next, examples of the present invention will be described. In the examples, “%” means “% by weight” unless otherwise specified. In the examples, unless otherwise specified, the term “solution” refers to a liquid (aqueous liquid) containing water as a medium, such as an aqueous solution or an aqueous dispersion.
Example 1
Prepare 4 ml of 20% solution of hydroxypropylcellulose, and then add 4 kinds of solution of Nika in different amounts of 0%, 2%, 4% and 6% in solid content ratio. 500 ml of a 20% solution (average molecular weight 10,000) was added and stirred to cause agglomeration reaction to produce a jelly-like thickened product.
A silver clay composition was prepared by kneading 700 g of silver fine particles surface-treated with oleic acid with 40 g of the obtained four kinds of jelly-like thickening substances.
The silver clay composition obtained in this way is all harder to dry and hard to crack while maintaining the optimum kneading condition as compared with conventional products, and the binding strength after drying is improved and stronger. It has been found.
Each silver clay composition was molded into a plate shape of 80 mm × 15 mm × 2 mm, dried at 80 ° C. for 40 minutes, and then subjected to a strength test by the following method.
<Bending strength test>
One end 20mm of a plate-shaped molded product of 80mm x 15mm x 2mm is fixed to the base, the remaining 60mm is projected outward, a weight is placed on the center (position 30mm from the projected tip), and the plate-shaped molded product is folded Until then, the weight of the weight is increased, and the weight of the weight when the plate-shaped molded product is broken is expressed as strength.
As a test result, the average value tested three times is shown.
Test No. Nika content in binder (% solids) Strength (g)
(1) 0 102.3
(2) 1 117.4
(3) 2 143.1
(4) 3 181.8
It can be seen that the strength of the product is significantly improved by adding glue to the binder. However, when the amount of glue added was 3% of the solid content in the binder (when 6% was added to the hydroxypropylcellulose solution), the stains on the hands increased somewhat. In addition, when these clay compositions were baked in an electric furnace at 850 ° C. for 30 minutes and then the appearance and shrinkage rate of the silver product were measured, none of the ones with Nika (Test No. 2-4) were Nikawa. Compared with the additive (Test No. 1), the gloss of the appearance was not changed, the beautiful silver color was exhibited, the shrinkage rate was small, and the strength after firing was satisfactory.

(Example 2)
Prepare 4 ml of 20% hydroxypropyl cellulose solution, 4% Nika (based on the amount of hydroxypropyl cellulose), 0% paper pulp, 1%, 2%, 4% (both to the amount of hydroxypropyl cellulose) Each was mixed and sufficiently kneaded, and each was added with 500 ml of a 20% ammonium polyacrylate solution, stirred and agglomerated to produce a jelly-like thickened product.
A silver clay composition was prepared by kneading 700 g of silver fine particles surface-treated with oleic acid with 40 g of the obtained four kinds of jelly-like thickening substances.
The silver clay compositions obtained in this way all have an optimum kneading condition as compared with conventional products, are slow to dry, hardly crack, and improve the binding strength after drying. The addition of paper pulp to the paper improved the strength of the silver clay after drying, enabling stable and good modeling without sagging over the details of the modeling work.
The strength test was carried out using each silver clay composition as a plate-like molded product similar to Example 1. The results were as follows.
Test No. Additive content in binder (solid content%) Strength (g)
Paper pulp Nika
(1) 0 2 143.1
(2) 0.5 2 192.5
(3) 1 2 247.2
(4) 2 2 338.7
When paper pulp was added to the binder together with glue, a higher strength clay was obtained than when glue was added. However, when the addition of paper pulp was 2% (4% with respect to hydroxypropyl cellulose), kneading became difficult and workability of clay production was deteriorated.

(Example 3)
Five 1000 ml of an aqueous solution containing 2000 ppm of ammonium oleate is prepared, and each gum arabic is added and dissolved in 0%, 5%, 10%, 20%, and 30% with respect to the ammonium oleate concentration. Into these, 500 g of silver fine particles not subjected to surface treatment were added and stirred, and after a few minutes, a small amount of acetic acid was added, further stirred, filtered, washed with water, and dried with a dryer.
In this manner, 70 g of each silver fine particle whose surface was combined with ammonium oleate and gum arabic was added to 500 ml of hydroxypropylcellulose 20% solution in Example 1, and 4% of Nikawa was added to 500 ml of 20% ammonium polyacrylate solution. And kneaded with 4 g of a jelly-like thickened material produced by mixing with a silver clay composition.
As a result, the silver clay composition without the addition of gum arabic had the disadvantage that during the modeling work, the clay was dried by natural drying, the soiling of the hands became severe, and the generation of wrinkles on the surface became strong, By adding gum arabic and treating the surface, the familiarity between the silver fine particles and the binder increases when grinded, it is easy to knead, there is very little dirt on the hands during molding, and there is flexibility and handling. It becomes easy. Moreover, it is hard to crack and the state of elongation is very good.
In addition, the dried state of the silver clay composition had no problem, and even after firing, it exhibited a very beautiful appearance shining beautifully in silver.
However, when 30% of gum arabic was added, there was a drawback that it became slightly brittle when the silver clay composition was dried.

Example 4
First, the following three types of solutions ac were prepared.
a. Hydroxypropylcellulose 20% solution 100ml
b. A solution prepared by adding 1.5% of Nika as a solid content to 100 ml of the solution of A. c. A solution obtained by adding 1.5% solids and 1.5% paper pulp to 100 ml of solution A and adding 150 ml of 20% sodium polyacrylate solution to each of these solutions, stirring and aggregating 3 types of binders A to C of jelly-like thickening substances were produced, and 100 ml of a 20% curdlan solution was used as binder D.
A. a mixture of a hydroxypropyl cellulose solution of a and a sodium polyacrylate solution; Mixture of solution of b containing glue and sodium polyacrylate solution C.I. A mixture of a solution of c containing glue and paper pulp and a sodium polyacrylate solution. Curdlan 20% solution Four kinds of binders AD prepared as described above were blended as shown in Table 1 to prepare 11 kinds of binders, and 5 g of these binders and surface-treated with oleic acid respectively. A silver clay composition no. 1-11.

Subsequently, the silver clay composition No. 1-11 was evaluated as follows. The results are shown in Table 2.
<Evaluation items>
B) Kneading condition (kneading property), hand dirt condition, storage stability b) Cracks, wrinkles, stickiness strength, elongation during modeling work) Moisture retention during modeling work (by natural drying)
2) Formation of clay surface film by rapid drying when using a dryer, dryer, etc. e) To strength after drying) For deformation, shrinkage, surface brightness after firing (850 ° C. × 20 minutes) The performance was evaluated on a four-point scale, and the best one was marked with 、, the one that could be used with ◯, the one with some problems △, and the one that could not be used with ×.

From this result, binder no. No. 1 is a binder No. 1 that uses a small amount of glue while the strength after drying is weak and the practicality is poor. No. 2 and 3 and binder No. using curdlan. No. 4 was strong and practical after drying.
In particular, binder No. using curdlan in combination with other binders. 5-11 exhibited an excellent effect on all the performances and became a silver clay composition that was very easy to handle.
The effect is as follows.
・ Small soiling of hands, good kneading condition, good storage stability ・ Clay during molding is strong and hard to crack ・ Moisture retention during molding is moderate ・ Surface when clay is dried rapidly Since the film cannot be coated and moisture evaporates uniformly from the clay surface, it does not swell or deform during drying, and is very excellent.Strength after drying is strong, and there is no need to use a reinforcing agent. It is easy to manufacture small shaped objects and is excellent in workability. ・ Because the shrinkage rate after firing is small, it is possible to manufacture things such as wirework without being damaged. ・ Gloss and brightness of precious metals after firing are beautiful.

Claims (6)

A noble metal powder surface-treated with a higher fatty acid and / or higher fatty acid salt and an aqueous organic binder solution are kneaded, and the organic binder aqueous solution has a solid content of 0.1 to 5.0. A precious metal clay composition comprising a weight percentage. Noble metal powder surface-treated with a higher fatty acid and / or higher fatty acid salt and an organic binder aqueous liquid are kneaded, and the organic binder aqueous liquid contains curdlan in a solid content of 1% by weight or more. A noble metal clay composition comprising: The clay composition according to claim 1 or 2, wherein the noble metal powder is a surface treated with a higher fatty acid and / or higher fatty acid salt and gum arabic. The higher fatty acid is a fatty acid having 12 to 22 carbon atoms, and the organic binder aqueous liquid includes (A) a mixture obtained by adding glue to at least one of polyvinyl alcohol and cellulose binder, and (B) an average molecular weight. It is a jelly-like thickened product obtained by blending at least one selected from the group consisting of polycarboxylic acid, polycarboxylate, polyoxycarboxylate and polyaminocarboxylate, which is 1000 to 130,000 The clay composition according to any one of claims 1 to 3, wherein: The precious metal powder has an apparent density of 2.5 g / cm ³ or more, a specific surface area of 0.1 to 2.0 m ² / g, and a 50% average particle size of 0.7 to 3 μm 5 and 20 to 50% by weight of a 50% average particle diameter of 3 to 8 μm are contained together. 5. The clay composition according to claim 1. The clay composition according to any one of claims 1 to 5, wherein paper binder is blended in the binder at a solid content of 0.01 to 5.0 wt%.