JP7703335B2 - Powder release agent - Google Patents

Description

The present invention relates to a powder release agent for die casting.

Die casting is a casting method in which molten metal (molten alloy) is injected into a complex-shaped mold at high speed and pressure, allowing for efficient and economical mass production of high-precision metal parts. During die casting, a die casting release agent is applied to the inner surface of the mold to cool the overheated mold, prevent adhesion (burn-in) between the injected metal and the mold, and reduce resistance (mold release resistance) when removing the casting from the mold.

Die casting release agents are broadly divided into solvent-based types, in which the active ingredient is dissolved or dispersed in a solvent, and solventless types, which do not use a solvent. The solvent-based types are further divided into water-based types, which use water as the solvent, and oil-based types, which use a hydrocarbon liquid as the solvent.

The active ingredients in die casting release agents include not only lubricating mineral oils, greases, and silicone oils that are liquid at room temperature, but also powdered substances that are solid at room temperature, such as inorganic powders, graphite, and wax. Since die casting involves a wide variety of manufacturing equipment, metal types, and other conditions, die casting release agents are formulated as needed with active ingredients that have properties suited to the diverse casting conditions at the manufacturing site.

Solvent-based release agents, which aim to efficiently coat the active ingredient on the inner surface of the mold by dissolving or dispersing the active ingredient in a solvent, are currently mainstream. In particular, water-based release agents, which use water as the solvent, are flame-retardant and have a significant effect of cooling the mold that overheats during the manufacturing process, and are therefore widely used as the mainstream die-casting release agents. Note that oil-based release agents use solvents other than water (mainly hydrocarbon solvents), but they have not become widespread due to significant issues in terms of equipment and safety due to the flammability and other properties of the solvent itself.

Meanwhile, in tandem with the development of manufacturing equipment technology, including internal mold cooling technology, there has also been progress in the development of solvent-free die-casting release agents that do not use solvents for mold cooling or efficient application of the release agent. In particular, powder-type die-casting release agents, which are sprayed in powder form, are expected to be an effective method for improving the environment and product quality from the perspective of release agents.

Japanese Patent Application Publication No. 03-243242 Patent No. 6613683 JP 2010-264466 A

The currently mainstream solvent-based water-based die-casting release agents contain water as the solvent, as the name suggests. Therefore, when a water-based release agent is applied to the inner surface of a mold, moisture often remains on the inner surface of the mold. In such cases, the residual moisture on the inner surface of the mold may be taken into the molten metal poured into the cavity of the mold and vaporize, which may cause the formation of casting cavities in the casting. In addition, if the Leidenfrost phenomenon occurs when the water-based release agent comes into contact with a high-temperature mold, the active ingredient may not adhere to the inner surface of the mold, and the release agent may not be able to function as intended. In addition, when using a water-based release agent, wastewater treatment equipment is required to avoid environmental risks derived from the used water-based release agent, and not only the temporary installation costs for the equipment but also the ongoing operating costs are unavoidable. Thus, even when using the currently mainstream solvent-based water-based release agents, many issues have still been pointed out.

On the other hand, when a powder type release agent is used, the problems mentioned above that arise from using a solvent-based water-based release agent do not occur. However, there are various problems with powder type release agents, and they have not necessarily become widespread.

As for powder type release agents, Patent Document 1 discloses a powder type release agent in which an organic substance that imparts adhesiveness to a powder or granular inorganic compound is mixed. The agent is an inorganic powder such as boron nitride or mica that exhibits release properties, mixed with an organic substance such as metal soap or a polymer compound as a binder component. However, the release agent according to this embodiment forms a fragile layer on the inner surface of the mold, so that when the molten metal injection speed is increased, the layer may break and peel off, resulting in reduced productivity due to poor demolding or seizure. In addition, since the main active ingredient is a colored and opaque inorganic powder, it is extremely difficult to maintain a good working environment.

Patent Document 2 discloses a powder release agent that includes main component particles that contain modified silicone oil as a lubricating liquid and have a main body that is formed into solid particles at room temperature, the main body being composed of an organic substance such as wax or resin. However, the powder release agent according to this embodiment has a complicated manufacturing process, and there is a concern that the organic substance that composes the main body itself will gasify when it comes into contact with the molten metal, causing blowholes, which are one of the causes of poor quality in castings.

As a powder release agent containing a lubricating liquid, a release agent containing silicone oil in ceramic particles having a hollow spherical shape has been reported (Patent Document 3). In producing the powder release agent of this type, high-temperature sintering is required to produce the ceramic particles, and a structure that can hold/release the required amount of silicone oil must be precisely molded, which makes the production process of the release agent itself extremely complicated.

The present invention aims to provide a powder release agent that has high releasability and easy handling, is expected to suppress contamination of the mold and its surroundings, generates less gas that causes blowholes, which are one of the causes of poor quality castings, and is easy to manufacture.

The powder release agent of the present invention is a powder release agent that is applied to the inner surface of a die-casting mold, and is characterized in that it is composed of a lubricating liquid and spherical porous silica, and contains, as an active ingredient, powder particles in which the lubricating liquid is impregnated and held in the spherical porous silica.

The lubricating liquid is preferably one or more selected from silicone oil, mineral oil, and synthetic oil.
The spherical porous silica is preferably composed of amorphous silica.

The powder release agent of the present invention preferably contains a spreading aid in addition to the spherical porous silica and the lubricating liquid.
The powder release agent preferably has an angle of repose of less than 70°.

According to the present invention, by using a specific spherical porous silica as a substance for impregnating the lubricating liquid, it is possible to suppress the generation of decomposition gases that cause poor quality of cast products, and to provide a powder release agent that can be easily manufactured by simple operations, which is easy to handle at room temperature and achieves excellent mold adhesion and cast product releasability during die casting.

Schematic diagram for explaining the procedure of the releasability test

The powder release agent and the method for producing the same of the present invention will be described in detail below.
The powder release agent of the present invention is characterized in that it is composed of spherical porous silica and a lubricating liquid, and contains, as an active ingredient, powder particles in which the spherical porous silica is impregnated with the lubricating liquid.
The spherical porous silica can exhibit high fluidity as a powder in the normal temperature range while retaining the lubricating liquid inside. Therefore, by incorporating the powder particles impregnated with the lubricating liquid into the spherical porous silica as an active ingredient of the powder mold release agent, clogging of the pipelines leading to the mold release agent storage tank and the injection of the mold release agent can be avoided to a high degree.
On the other hand, when the powder release agent of the present invention reaches the inner surface of the die, the lubricating liquid contained in the powder particles expands and erupts out of the powder due to a sudden temperature rise caused by contact with a high-temperature die or the introduction of molten metal, and the lubricating liquid is supplied uniformly and quickly to the inner surface of the die, thereby exhibiting excellent releasability. The inner surface of the die is also called the cavity wall surface of the die.

The average particle size of the spherical porous silica is usually 0.5 to 100 μm. If the average particle size of the spherical porous silica is less than 0.5 μm, not only is the handling property reduced, but the working environment of the workers is also difficult to maintain. On the other hand, if the average particle size exceeds 1000 μm, the smoothness of the inner surface of the mold is reduced due to the adhesion of the powder mold release agent, which has a negative effect on the surface quality of the casting. Therefore, the average particle size of the spherical porous silica used is preferably 1 to 100 μm. Examples of the spherical porous silica include Sunsphere (manufactured by AGC Si-Tech Co., Ltd.), Godball (manufactured by Suzuki Oil Industries Co., Ltd.), and Microid (ultrafine powdered silica, manufactured by Tokai Chemical Industry Co., Ltd.). Of these, Sunsphere is a spherical amorphous silica that does not contain crystalline silica, and is preferable because it has excellent fluidity and oil absorption properties, as well as being easy to handle in terms of ensuring the working environment.

The lubricating fluid used may be silicone oil, mineral oil, synthetic oil, or the like.
The silicone oil may be a straight silicone oil such as polydimethylsiloxane or polymethylphenylsiloxane, or a modified silicone oil. The modified silicone oil may be an organopolysiloxane at least partially modified with an alkyl group, an aralkyl group, a carboxylalkyl group, a carboxylate alkyl group, a hydroxyalkyl group, an aminoalkyl group, or the like.

The mineral oil used is a mineral oil that is generally used as a base oil for lubricating fluids. Examples include paraffin-based mineral oil and naphthene-based mineral oil. The kinetic viscosity (100° C.) of these mineral oils is usually 5 to 600 mm ² /s.

Synthetic oils include fatty acids obtained from fats and oils such as beef tallow, lard, rapeseed oil, coconut oil, palm oil, rice bran oil, and hydrogenated versions of these oils; esters of fatty acids and alcohols; poly-α-olefins such as polybutene; polyols such as polyethylene glycol or polyester polyol; other polyethers; polyesters; higher alcohols; polybutadienes, etc.

The above lubricants may be used alone or in combination of two or more.

Of these, it is preferable to use silicone oil because it exhibits excellent release properties.

In the powder particles of the present invention, the weight ratio of the spherical porous silica and the lubricating liquid (spherical porous silica/lubricating liquid) is preferably 30/70 to 95/1, and more preferably 45/55 to 90/10.

If the ratio of the spherical porous silica to the lubricating liquid in the powder particles exceeds 30/70 and the lubricating liquid ratio increases, the flowability of the powder particles when mixed with a powder release agent is significantly reduced, resulting in problems such as blockages in the piping and unevenness in the release agent film.
On the other hand, if the ratio of spherical porous silica to lubricating liquid falls below 95/1 and the lubricating liquid ratio decreases, sufficient releasability cannot be obtained.

The powder release agent preferably contains a spreading aid in addition to the powder particles made of spherical porous silica impregnated with a lubricating liquid, in order to ensure adhesion that can withstand a wide range of mold temperatures, including the cooling molds that have been developed in recent years. The spreading aid is an organic substance that is solid at room temperature and melts or softens due to the heat of the mold.

Examples of the spreading aid include synthetic waxes such as paraffin wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, N,N'-ethylene bisoleic acid amide, and N,N'-ethylene bisstearic acid amide; natural waxes such as beeswax, carnauba wax, and montan wax; and thermoplastic resins such as polytetrafluoroethylene, acrylic resins, methacrylic resins, polyvinyl acetate, polyurethane, polystyrene, polyvinylidene fluoride, polycarbonate, and acrylonitrile styrene resins.
The spreading aid can be added in a range that does not affect the quality of the casting, but the weight ratio of the powder particles to the spreading aid is preferably 50/50 to 99/1, and more preferably 70/30 to 90/10.

The repose angle of the powder release agent, which is an index showing the fluidity of the powder, is preferably less than 70°, and more preferably 40° or less. In this specification, the repose angle is a value measured by the injection method using a funnel conforming to JIS standard K6911.5.2 and a drop height of 90 mm for a powder release agent that has been vacuum dried at 50°C for 8 hours or more.

Methods for producing powder particles in which spherical porous silica is impregnated with a lubricating liquid include diluting the lubricating liquid with a solvent, permeating the porous silica with the diluted liquid, and gradually drying the liquid to volatilize the solvent, thereby impregnating the interior of the porous silica with the lubricant, or immersing the porous silica in the lubricant and drawing a vacuum to forcibly permeate the interior of the porous silica with the lubricant.

In addition to the powder particles consisting of spherical porous silica and lubricating liquid, the powder release agent may contain an appropriate amount of the spreading aid described above, as well as release components, dispersant components, and other additive components contained in general lubricating liquids within a range that does not impair the effects of the present invention.

In one embodiment of the method for producing powder particles in the present invention, 1.0 to 10 times by weight of a low-polarity organic solvent and 0.05 to 3.0 times by weight of a lubricating liquid are added to spherical porous silica, and the mixture is mixed and stirred until it becomes uniform to obtain a dispersion liquid. Next, the low-polarity organic solvent is removed from the dispersion liquid under reduced pressure using an evaporator, and powder particles in which the lubricating liquid is uniformly absorbed into the spherical porous silica can be obtained almost quantitatively. The obtained powder particles do not generate agglomerates, and no difference in appearance is observed between the spherical porous silica before oil absorption and the powder particles when observed with a scanning electron microscope (SEM). In other words, the powder particles in the present invention can be said to be smooth and easy to handle.

The low-polarity organic solvent used in the production of the powder particles can be selected from hexane, petroleum ether, diethyl ether, toluene, tetrahydrofuran, etc. By using these low-polarity organic solvents, a highly uniform solvent dispersion of the lubricating liquid can be obtained, making it possible to produce homogeneous powder particles that are less likely to form agglomerates.

The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to these examples.
[Preparation of Powder Release Agent]
Powder release agents were prepared according to Examples 1 to 12 and Comparative Examples 1 to 4.
[Evaluation of Powder Release Agents]

(1) Mold releasability The presence or absence of aluminum seizing onto steel plates (material: SKD61) heated to 250° C. and 300° C. was evaluated. The test conditions are shown in Table 1 below.

The test procedure was as shown in Figure 1. The test procedure was as shown in Figure 1. That is, (1) an aqueous release agent was applied by using a spray, (2) a cylindrical jig was installed and molten aluminum was poured into it, and (3) a load was applied and the jig was pulled in the horizontal direction, and the superiority or inferiority of the release property was judged depending on whether the jig could be pulled without sticking and the maximum load required for pulling.
(Releasability evaluation standard: 250°C condition)
A: The release resistance was less than 4.5 kg.
Δ: The release resistance was 4.5 kg or more and less than 6.0 kg.
×: The release resistance was 6.0 kg or more.
(Releasability evaluation standard: 300°C condition)
◯: The release resistance was less than 12 kg.
Δ: The release resistance was 12 kg or more and less than 22 kg.
x: The demolding resistance was 22 kg or more, which was above the upper limit of the demolding resistance.

(2) Adhesion To a steel plate (100 mm × 100 mm) heated to 250° C., 0.5 g of the powder release agent was applied from a position 20 cm away using a spray gun for powder application, and the amount of the powder release agent adhered to the steel plate was measured.

(3) Stain The appearance of the steel plate used in the above (2) adhesion test was evaluated visually.
◯: Colorless or light white △: Dark white ×: Opaque color other than white

(4) Angle of repose: Measured by the injection method using a funnel conforming to JIS K6911.5.2 and a drop height of 90 mm.
The powder release agent was dropped from a funnel of a certain height onto a horizontal substrate through a 710 μm sieve, and the angle between the generating line of the powder release agent deposited in a cone shape on the substrate and the substrate surface was measured as the angle of repose.
Measuring device: Angle of repose measuring device ASK-01 (manufactured by AS ONE Co., Ltd.)
(Repose angle evaluation criteria)
A: The angle of repose was 30° or more and less than 50°.
Δ: The angle of repose was 50° or more and less than 70°.
×: The angle of repose was 70° or more.

[Example 1]
48 parts by weight of Sunsphere H-52 (AGC Si-Tech Co., Ltd.) was mixed and stirred with 100 parts by weight of diethyl ether and 32 parts by weight of BY16-799 (dimethyl silicone oil (80 ^mm2 /s), DuPont Toray Specialty Materials Co., Ltd.), and the diethyl ether was then removed under reduced pressure to obtain powder particles. Furthermore, 20 parts by weight of A-C-392 (oxidized polyethylene wax, Honeywell International Co., Ltd.) was added to prepare a powder release agent.
The evaluation results of the powder release agent of Example 1 are shown in Table 2.

[Examples 2 to 4]
The powder release agents were prepared in the same manner as in Example 1, except that in Example 1, BY16-799 (dimethyl silicone oil (80 mm ² /s)) was replaced with SH-550 (methyl phenyl silicone oil (125 mm ² /s), manufactured by DuPont Toray Specialty Materials Co., Ltd.) (Example 2), TN (organo polysiloxane (1200 mm ² /s), manufactured by Wacker Asahi Kasei Silicone Co. ^, Ltd.) (Example 3), or X42-C5615 (organo polysiloxane (5400 mm 2 /s), manufactured by Momentive Performance Japan, LLC) (Example 4).
The evaluation results of the powder release agents of Examples 2 to 4 are shown in Table 2.

[Example 5]
A powder release agent was prepared in the same manner as in Example 3, except that the amount of Sunsphere H-52 (manufactured by AGC Si-Tech Co., Ltd.) was changed from 40 parts by weight to 26 parts by weight, and the amount of TN (organopolysiloxane (1200 ^mm2 /s), manufactured by Wacker Asahi Kasei Silicones Co., Ltd.) was changed from 32 parts by weight to 54 parts by weight.
The evaluation results of the powder release agent of Example 5 are shown in Table 2.

[Example 6]
A powder release agent was prepared in the same manner as in Example 5, except that the amount of Sunsphere H-52 (manufactured by AGC Si-Tech Co., Ltd.) was changed from 26 parts by weight to 40 parts by weight, and the amount of TN (organopolysiloxane (1200 ^mm2 /s), manufactured by Wacker Asahi Kasei Silicones Co., Ltd.) was changed from 54 parts by weight to 40 parts by weight.
The evaluation results of the powder release agent of Example 6 are shown in Table 2.

[Example 7]
A powder release agent was prepared in the same manner as in Example 6, except that the amount of Sunsphere H-52 (manufactured by AGC Si-Tech Co., Ltd.) was changed from 40 parts by weight to 72 parts by weight, and the amount of TN (organopolysiloxane (1200 ^mm2 /s), manufactured by Wacker Asahi Kasei Silicones Co., Ltd.) was changed from 40 parts by weight to 8 parts by weight.
The evaluation results of the powder release agent of Example 7 are shown in Table 2.

[Example 8]
A powder release agent was prepared in the same manner as in Example 7, except that the amount of Sunsphere H-52 (manufactured by AGC Si-Tech Co., Ltd.) was changed from 72 parts by weight to 76 parts by weight, and the amount of TN (organopolysiloxane (1200 ^mm2 /s), manufactured by Wacker Asahi Kasei Silicones Co., Ltd.) was changed from 8 parts by weight to 4 parts by weight.
The evaluation results of the powder release agent of Example 8 are shown in Table 2.

[Example 9]
A powder release agent was prepared in the same manner as in Example 8, except that the amount of Sunsphere H-52 (manufactured by AGC Si-Tech Co., Ltd.) was changed from 76 parts by weight to 40 parts by weight, the amount of TN (organopolysiloxane (1200 mm2/s), manufactured by Wacker Asahi Kasei Silicones Co., Ltd.) was changed from 4 parts by weight to 10 parts by weight, and the amount of A-C-392 (oxidized polyethylene wax, manufactured by Honeywell International Co., Ltd.) was changed from 20 parts by weight to 50 parts by weight.
The evaluation results of the powder release agent of Example 9 are shown in Table 2.

[Example 10]
A powder release agent was prepared in the same manner as in Example 7, except that the amount of TN (organopolysiloxane (1200 ^mm2 /s), manufactured by Wacker Asahi Kasei Silicones Co., Ltd.) was changed from 8 parts by weight to 18 parts by weight, and that A-C-392 (oxidized polyethylene wax, manufactured by Honeywell International Co., Ltd.) was changed from 20 parts by weight to 10 parts by weight.
The evaluation results of the powder release agent of Example 10 are shown in Table 3.

[Example 11]
100 parts by weight of diethyl ether and 26 parts by weight of TN (organopolysiloxane (1200 ^mm2 /s), manufactured by Wacker Asahi Kasei Silicones) were added to 54 parts by weight of Sunsphere H-52 (manufactured by AGC Si-Tech Co., Ltd.), mixed and stirred, and then the diethyl ether was removed under reduced pressure to obtain powder particles. Furthermore, 20 parts by weight of Aluminum Stearate 600 (polyethylene oxide, manufactured by NOF Corporation) was added to prepare a powder release agent.
The evaluation results of the powder release agent of Example 11 are shown in Table 3.

[Example 12]
A powder release agent was prepared in the same manner as in Example 11, except that calcium stearate (calcium stearate, manufactured by NOF Corporation) was used instead of aluminum stearate 600 (aluminum stearate, manufactured by NOF Corporation).
The evaluation results of the powder release agent of Example 12 are shown in Table 3.

[Comparative Examples 1 and 2]
A powder release agent of Comparative Example 1 was prepared by mixing 20 parts by weight of AC-392 (oxidized polyethylene wax, manufactured by Honeywell International) and 80 parts by weight of graphite.
A powder release agent of Comparative Example 2 was prepared by mixing 20 parts by weight of AC-392 (oxidized polyethylene wax, manufactured by Honeywell International) and 80 parts by weight of talc.
The evaluation results of the powder release agents of Comparative Examples 1 and 2 are shown in Table 3. Comparative Example 1, which used graphite as a lubricant, showed releasability and handling properties (angle of repose) comparable to those of the Examples of the present invention, but since graphite, which is a black powder, is used, the deterioration of the working environment due to scattering of the black powder is inevitable. In addition, Comparative Example 2, which used talc, which is an amorphous inorganic fine powder with high adhesion, as a solid lubricant, showed the same level of handling properties (angle of repose) as those of the Examples, but it was confirmed that the releasability was insufficient.

[Comparative Example 3]
A powder release agent of Comparative Example 3 was prepared by mixing 20 parts by weight of AC-392 (oxidized polyethylene wax, manufactured by Honeywell International) and 80 parts by weight of Sunsphere H-52 (manufactured by AGC Si-Tech Co., Ltd.).
The evaluation results of the powder release agent of Comparative Example 3 are shown in Table 3. It was confirmed that when spherical porous silica that was not impregnated with the lubricating liquid was blended as powder particles, sufficient release performance was not exhibited.

[Comparative Example 4]
100 parts by weight of diethyl ether and 10 parts by weight of TN (organopolysiloxane (1200 ^mm2 /s), manufactured by Wacker Asahi Kasei Silicones Co., Ltd.) were added to 80 parts by weight of diatomaceous earth (Radiolite #300, manufactured by Showa Chemical Industry Co., Ltd.), which is a natural amorphous porous silica mineral, and the mixture was mixed and stirred, after which the diethyl ether was removed under reduced pressure to obtain powder particles. Furthermore, 10 parts by weight of A-C-392 (oxidized polyethylene wax, manufactured by Honeywell International) was added to prepare the powder release agent of Comparative Example 4.
The evaluation results of the powder release agent of Comparative Example 4 are shown in Table 3. When powder particles were prepared by using diatomaceous earth instead of spherical porous silica, it was possible to prepare a powder release agent composition that satisfied the necessary handling properties (angle of repose), but it was confirmed that the powder release agent did not exhibit sufficient release performance.

Claims (4)

A powder release agent applied to a cavity wall surface of a casting mold, comprising:
Powder particles comprising a lubricating liquid and spherical porous silica, the spherical porous silica being impregnated with the lubricating liquid;
It consists of a spreading aid,
The lubricating liquid is silicone oil,
The spreading aid is a wax.
Powder release agent. The powder release agent according to claim 1, wherein the weight ratio of the spherical porous silica and the lubricating liquid (spherical porous silica/lubricating liquid) in the powder particles is 30/70 to 99/1. The powder release agent according to claim 1 or 2, wherein the spherical porous silica is amorphous silica. 3. The powder release agent according to claim 1, wherein the angle of repose is less than 70°.