DIE RELEASE AGENT COMPOSITION

TECHNICAL FIELD

The present disclosure relates to a die release agent composition. More particularly, the present invention relates to a die release agent composition which is used by being applied to a die used for the squeeze casting, low-pressure casting, or the like of an aluminum alloy or the like, or a die used for the die forging of an aluminum alloy, an aluminum steel, or the like.

BACKGROUND ART

As metal forming methods using dies, there are a casting method and a die forging method. Examples of the casting method include a low-pressure casting method, a die casting method, and the like. In such a casting method, prior to filling a die with a molten metal, a die release agent is used for the purpose of suppressing a reaction (welding) between the die and the molten metal and also assisting the die releasing of a formed product. In the low-pressure casting method, a squeeze die casting method as a type of the die casting method, or the like, due to the low speed at which a cavity is filled with a molten metal such as an aluminum alloy, the die temperature and the molten metal temperature are held higher than in a typical high-speed die casting method with the view to ensuring the fluidity of the molten metal during the filling. As a die release agent appropriate for such high-temperature forming, a die release agent containing a powder is used in most cases to provide a heat insulating effect. In the low-pressure casting, a die wash including an inorganic powder and water glass may be used.

In general, die release agents include water-based types and oil-based types. For example, in a casting method, before pouring, a die release agent is applied to a casting die by spray coating to form a coating so that the casting die is used. As a water-type die release agent, a composition in which water is used as a dispersion medium and an inorganic powder of talc or the like, a binder component such as a hydrosoluble polymer, a dispersant for dispersing the inorganic powder in water, and an organic compound intended to provide lubrication and prevent seizing such as wax or silicone are blended or the like is used. As an oil-based die release agent, a composition in which silicone oil is diluted with a solvent or the like is used.

However, in each of the low-pressure casting method and the squeeze casting method, the filling speed is low and the die temperature and the molten metal temperature are held high so that a large number of problems occur in association with a die release agent. For example, with a water-type die release agent, it is difficult to form a coating due to a Leidenfrost phenomenon. To obtain a sufficient film thickness, a spraying time needs to be increased to result in a reduction in die temperature. On the other hand, an oil-type die release agent has a coating formability superior to that of the water-type die release agent, but requires a spray control technique for limiting excessive ejection of the die release agent. In addition, excessive coating formation causes the contamination of the die due to the deposition of the components of the die release agent to consequently affect size precision. When the die temperature is particularly high, the die release agent components are gasified to be included in a product (such as a cast product) to result in such a problem as the occurrence of an internal defect. Consequently, to suppress the occurrence of such a problem, a method which reduces the amount of ejection may be used.

More specifically, as a die release agent containing a powder and using water as a dispersion medium, an aqueous die release agent has been known which contains an inorganic lubricant, spherical resin particles, and an organic metal carboxylate (see, e.g., Patent Document 1). Also, as die release agents each containing a powder and using an organic solvent as a dispersion medium, a lubricant die release agent has been known which contains a powdery solid lubricant, an adhesion improver, and a volatile solvent (see, e.g., Patent Document 2) and a metal casting die release agent has been known which contains a solvent having a specified dynamic viscosity, an inorganic powder having a specified color tone, and an inorganic powder of graphite, carbon black, or the like (see Patent Document 3).

PRIOR ART LITERATURES
Patent Literature

[Patent Literature 1]

JP-A-2001-259788

[Patent Literature 2]

JP-A-2000-33457

[Patent Literature 3]

JP-A-2008-93722

SUMMARY OF THE INVENTION
Problems to Be Solved By the Invention

However, a water-type die release agent is deposited on a die as a result of being continuously used to adversely affect the size precision and the outer appearance of a product. This necessitates a regular cleaning operation and causes a reduction in production efficiency. On the other hand, a method intended to reduce the amount of deposition leads to the degradation of the adherability (coating formability) of a die release agent. Thus, it is not easy to simultaneously suppress deposition and provide a coating formability. In addition, reducing the amount of ejection to suppress excessive formation of a coating results in most cases in the clogging of a spray nozzle especially when the die release agent contains a powder. Accordingly, there is a demand for a die release agent which has a coating formability that allows a sufficient heat retainability and a sufficient releasability to be obtained even at a high die temperature over 300° C. and which is less likely to be deposited on a die and clog a spray nozzle.

In a low-pressure casting method, a die wash may be used, but leads to such problems as a non-uniform coating thickness and the high surface roughness of a cast product resulting from a rough coating surface. In addition, since the coating becomes thinner with time, there is also a problem of a reduction in the size precision of a product.

The present invention has been achieved in view of the conventional situation described above and an object thereof is to provide a die release agent which is used by being applied to a die used for the squeeze casting, low-pressure casting, or the like of an aluminum alloy or the like or a die used for the die forging of an aluminum alloy, an aluminum steel, or the like.

Means for Solving the Problems

When a thermosetting resin having excellent heat resistance is used as a binder component in a die release agent, a solid coating is formed and the releasability of the coating is also improved by the behavior of being thermally decomposed of the thermosetting resin. That is, by blending a predetermined amount of the thermosetting resin, in the process of forming the coating, the solid coating is formed and, after contact with a high-temperature molten metal, the coating becomes brittle and is easily removed. By also providing an oil-type die release agent containing a mineral oil as a dispersion medium and using a solid lubricant as a die releasing component, the decomposition of the die release agent is suppressed and a coating having a sufficient thickness is formed to ensure a heat retainability and allow a predetermined die temperature to be retained.

In addition, by blending a polymer compound such as waxes depending on the die temperature, a die release agent having more excellent performance can be obtained. That is, when the solid lubricant and the thermosetting resin are dispersed in the mineral oil or the like and waxes or the like are added thereto, it is possible to form a coating even on a die at a particularly high temperature over 400° C. with a short period of spraying and improve the production efficiency. On the other hand, when the die release agent tends to excessively adhere to a die at a temperature of not more than 400° C. and the peelability of the coating tends to deteriorate, other waxes, another polymer compound other than waxes, e.g., polybutene or the like is used to provide a similarly high coating formability without impairing the peelability of the coating.

As described above, by choosing and selectively using the polymer compound type to be used in accordance with the die temperature and further adjusting the blending amount of the polymer compound, it is possible to simultaneously provide primary performance such as releasability or heat retainability and secondary performance such as peelability. In addition, the solid lubricant can be sufficiently dispersed by performing treatment such as high-speed agitation in the process of preparing the die release agent. This can prevent the clogging of a spray nozzle.

The thermosetting resin has a viscosity when thermally melted, a setting speed, and the like which differ depending on its average molecular weight and can provide an adhesion strength in accordance with its molecular weight. Accordingly, by using a thermosetting resin having a predetermined average molecular weight in accordance with a forming method and forming conditions such as the temperature of a die, it is possible to form a solid coating during forming and allow easy die releasing using the subsequent thermal decomposition of the thermosetting resin. It is also easy to remove the residues of the die release agent from the surface of the die. In addition, by using the thermosetting resin having a predetermined average molecular weight, it is also possible to provide a die release agent composition having a tendency of being less likely to be deposited on a forming die and cause the clogging of the spray nozzle.

The present invention has been achieved on the basis of such findings.

The present invention is as follows.

1. A die release agent composition including a mineral oil or a synthetic oil, a solid lubricant, a thermosetting resin, and a polymer compound and used by being applied to an inner surface of a die for casting or forging.

2. A die release agent composition according to No. 1 described above, wherein the solid lubricant is at least one of talc, boron nitride, graphite, mica, molybdenum disulfide, and fullerene.

3. A die release agent composition according to No. 1 or No. 2 described above, wherein an average particle diameter of the solid lubricant is 0.5 to 30 μm and a content of the solid lubricant is 1 to 10 mass % when a total content of the mineral oil or the synthetic oil, the solid lubricant, the thermosetting resin, and the polymer compound is 100 mass %.

4. A die release agent composition according to any one of No. 1 to No. 3 described above, wherein the thermosetting resin is at least one of a phenol resin, an epoxy resin, a urea resin, a melamine resin, an alkyd resin, and an unsaturated polyester resin.

5. A die release agent composition according to any one of claims No. 1 to No. 4 described above, wherein the thermosetting resin serves as a binder upon application of the die release agent composition to the die and is decomposed at a temperature during forming.

6. A die release agent composition according to any one of claims No. 1 to No. 5 described above, wherein, when a number average molecular weight of the thermosetting resin is 5,000 to 500,000 and a forming temperature is 300 to 550° C., an adhesion strength is 0.1 to 5.0 MPa.

7. A die release agent composition according to any one of No. 1 to No. 6 described above, wherein the polymer compound is at least one of a synthetic wax and a natural wax.

8. A die release agent composition according to any one of No. 1 to No. 6 described above, wherein the polymer compound is at least one of the synthetic wax and polybutene.

9. A die release agent composition according to No. 8 described above, wherein, when a temperature of the die during the application of the die release agent composition thereto is not less than 250° C. and less than 400° C., the polybutene is used and, when the temperature of the die during the application of the die release agent composition thereto is not less than 400° C. and not more than 550° C., the synthetic wax is used.

Note that the average molecular weight in the present invention is a polystyrene equivalent number average molecular weight measured by gel permeation chromatography.

Effects of the Invention

The die release agent composition according to the present invention contains the mineral oil or the synthetic oil, the solid lubricant, the thermosetting resin, and the polymer compound. Accordingly, even on a die at a thigh temperature, a coating is promptly formed from the components of the die release agent and a reduction in the temperature of the die is suppressed. In addition, the coating is easily decomposed by heat from the die and a molten metal during forming to become brittle, which significantly reduces the deposition of the die release agent components. As a result, it is possible to provide a product having excellent size precision and an excellent outer appearance. Moreover, since the die release agent has high heat resistance, it is also possible to provide a high-quality product having reduced internal defects such as blow holes due to a gas resulting from the decomposition of the die release agent components.

In the case where the solid lubricant is at least one of talc, boron nitride, graphite, mica, molybdenum disulfide, and fullerene, the decomposition of the die release agent components is sufficiently suppressed. This allows a coating having a predetermined thickness to be formed and also ensures a heat retainability. As a result, it is possible to maintain a predetermined die temperature.

In the case where the average particle diameter of the solid lubricant is 0.5 to 30 μm and the content of the solid lubricant is 1 to 10 mass % when a total content of the mineral oil or the synthetic oil, the solid lubricant, the thermosetting resin, and the polymer compound is 100 mass %, powder particles are not aggregated. As a result, the clogging of a spray nozzle is suppressed and the unevenness of the surface of the coating due to coarse particles is also reduced.

In the case where the thermosetting resin is at least one of the phenol resin, the epoxy resin, the urea resin, the melamine resin, the alkyd resin, and the unsaturated polyester resin, a sufficiently solid coating is formed and the peelability of the coating is further improved by the behavior of being thermally decomposed of the thermosetting resin.

In the case where the thermosetting resin serves as the binder upon application of the die release agent composition to the die and is decomposed at the temperature during forming, a solid coating can be formed during forming and is thermally decomposed thereafter. This allows easy die releasing as well as easy removal of the residues of the die release agent from the surface of the die.

In the case where, when the number average molecular weight of the thermosetting resin is 5,000 to 500,000 and the forming temperature is 300 to 550° C., the adhesion strength is 0.1 to 5.0 MPa, by using the thermosetting resin having a predetermined average molecular weight in accordance with a forming method, forming conditions, or the like, it is possible to provide a die release agent composition having a sufficient adhesion strength.

In the case where the polymer compound is at least one of the synthetic wax and the natural wax, it is possible to form a coating even on a die at a particularly high temperature over 400° C. with a short period of spraying and improve the production efficiency.

In the case where the polymer compound is at least one of the synthetic wax and polybutene, by selectively using these polymer compounds in accordance with the temperature of the die, a coating can be formed in a wider range of die temperatures.

In the case where, when the temperature of the die during the application of the die release agent composition thereto is not less than 250° C. and less than 400° C., polybutene is used and, when the temperature of the die during the application of the die release agent composition thereto is not less than 400° C. and not more than 550° C., a coating can be easily formed with a shorter period of spraying irrespective of the temperature of the die.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an illustrative view showing the outline of a device used for air blowing for ejecting a die release agent composition for forming a coating and removing the formed coating.

FIG. 2(
a) is an illustrative view showing the state where a die release agent is applied toward a steel plate by spray coating to form a coating, and FIG. 2(b) is an illustrative view showing the state where a metallic cylinder simulating a die is placed on the coating and a molten aluminum is applied into the cylinder.

FIG. 3(
a) is an illustrative view showing the state where a die release agent composition is applied toward a steel plate by spray coating to form a coating, FIG. 3(b) is an illustrative view showing the state where a metallic cylinder simulating a die is placed on the coating and a molten aluminum is supplied into the cylinder, FIG. 3(c) is an illustrative view showing the state where the metallic cylinder and a disc-shaped formed body have been removed from over the coating, and FIG. 3(d) is an illustrative view showing the state where the coating is being removed by air blowing.

FIGS. 4(
a) to 4(c) are illustrative views of a specimen for measuring a failure shear stress, of which FIG. 4(a) is a schematic diagram of the cross sections and surfaces of iron plates before being joined, FIG. 4(b) is a schematic diagram of the cross section and surfaces of the joined iron plates, and FIG. 4(c) is a schematic diagram showing the direction in which the two joined iron plates are pulled.

FIG. 5 is a graph showing the correlation between the number average molecular weight of a phenol resin and a failure shear strength which differs depending on a bonding temperature.

FIG. 6 is a graph related to the correlation between the number average molecular weight of a phenol resin and an adhesion area ratio.

EMBODIMENTS FOR CARRYING OUT INVENTION

The present invention will be described below in detail.

A die release agent composition of the present invention contains a mineral oil or a synthetic oil, a solid lubricant, a thermosetting resin, and a polymer compound. The die release agent composition is used by being applied to the inner surface of a die for casting or forging.

The mineral oil or the synthetic oil used as a dispersion medium is not particularly limited. As the mineral oil, various oils of mineral substances can be used. Examples of the mineral oil include the turbine oil described in JIS K 2213, the gear oil described in JIS K 2219, the machine oil described in JIS K 2238, and the like. As the synthetic oil, various oils of a polyalphaolefin type, a polyester type, a polyglycol type, and the like can be used. In particular, for a coating formability and for suppressing the precipitation of the solid lubricant, a mineral oil or a synthetic oil having a dynamic viscosity measured at 40° C. in accordance with JIS K 2283 which is preferably 10 to 400 mm²/s, more preferably 10 to 250 mm²/s, or most preferably 10 to 100 mm²/s is used. The blending amount of the mineral oil or the synthetic resin is preferably 75 to 90 mass % or more preferably 80 to 85 mass % when the total amount of the mineral oil or the synthetic oil, the solid lubricant, the thermosetting resin, and the polymer compound is 100 mass %.

The solid lubricant is also not particularly limited. Examples of the solid lubricant include talc, boron nitride, graphite, mica, molybdenum disulfide, and fullerene. In terms of preventing the clogging of a nozzle during spray coating, the average molecular weight of the solid lubricant is preferably not more than 30 μm, or more preferably 0.5 to 30 μm. When the total amount of the mineral oil or the synthetic oil, the solid lubricant, the thermosetting resin, and the polymer compound is 100 mass %, the blending amount of the solid lubricant is preferably 1 to 10 mass %, or more preferably 3 to 7 mass %. The aggregated particles of the solid lubricant may cause the clogging of the nozzle during spray coating. When the aggregated particles are applied as they are, coarse particles are consequently present in the coating to cause such a problem of the occurrence of unevenness in the surface of a formed product. To prevent the problem, during the preparation of the die release agent composition, it is preferable to sufficiently disperse the solid lubricant by mechanical treatment using a high-speed agitator, a colloid mill, or the like.

The thermosetting resin is also not particularly limited. Examples of the thermosetting resin include a phenol resin, an epoxy resin, a urea resin, a melamine resin, an alkyd resin, an unsaturated polyester resin, and the like. The thermosetting resin allows a solid coating to be formed by being contained in the die release agent composition. The thermosetting resin has high performance as a binder and also improves the peelability of the coating by being thermally decomposed after forming. The average molecular weight of the thermosetting resin is preferably 6,000 to 1,000,000. When a particularly large adhesion strength is to be obtained, the average molecular weight thereof is preferably 6,000 to 100,000. To allow easy peeling upon die releasing, the average molecular weight thereof is preferably over 100,000 and not more than 1,000,000. Thus, the average molecular weight of the thermosetting resin is preferably set in consideration of both the adhesion strength and the peelability. Also, in terms of improving the peelability, the blending amount of the thermosetting resin is preferably 1 to 15 mass %, more preferably 2 to 12 mass %, or most preferably 3 to 7 mass % when the total amount of the mineral oil or the synthetic oil, the solid lubricant, the thermosetting resin, and the polymer compound is 100 mass %.

Examples of the polymer compound include synthetic waxes such as paraffin wax, polyethylene wax, polypropylene wax, polyethylene oxide wax, and polypropylene oxide wax, natural waxes such as bees wax, carnauba wax, and montan wax, polybutene, polyalkylene glycol, and the like. Note that, since the polymer compound is decomposed by heat to generate a gas, excessive blending of the polymer compound may affect the qualities of the coating and a formed product. Accordingly, the blending amount of the polymer compound is preferably 2 to 15 mass %, more preferably 2 to 10 mass %, or most preferably 4 to 8 mass % when the total amount of the mineral oil or the synthetic oil, the solid lubricant, the thermosetting resin, and the polymer compound is 100 mass %.

As the polymer compound, the synthetic wax, polybutene, or the like is preferred. As the synthetic wax, the paraffin wax, the polyethylene oxide wax, or the polypropylene oxide wax is preferred and, in particular, the paraffin wax or the polyethylene wax is preferred. Preferably, the polymer compound is selectively used in accordance with the temperature of the die. It is particularly preferable that, as the polymer compound, the synthetic wax such as the paraffin wax or polybutene is used and, when the temperature of the die during the application of the die release agent thereto is not less than 250° C. and less than 400° C., polybutene is used and, when the temperature of the die during the application of the die release agent thereto is not less than 400° C. and not more than 550° C., the synthetic wax such as the paraffin wax is used. In this manner, a coating having a predetermined thickness can easily be formed with a short period of spraying.

It is also possible to cause the die release agent composition to contain, as a lubricant component, another lubricant other than the solid lubricant described above. The other lubricant is not particularly limited. Examples of the other lubricant include a silicone compound, waxes, another synthetic oil other than the synthetic oil used as the dispersion medium mentioned above, an inorganic powder, and the like. As the silicone compound, besides silicone oil or silicone wax, organopolysiloxane or the like can be used which has been partly or wholly modified with an alkyl group, an aralkyl group, a carboxyl alkyl group or a carboxylic alkyl group, a hydroxy-alkyl group, an aminoalkyl group, or the like.

As the other lubricant, besides the various lubricants mentioned above, fats and oils such as animal/plant fats and oils, a polyester-based synthetic lubricant oil, ZnDTP, MoDTP, ZnDTC, MoDTC, a phosphorus-based or sulfur-based extreme-pressure additive, calcium sulfonate, or the like can be used. Besides these lubricants, any lubricant typically used for a die release agent for die casting can be used without being particularly limited. The blending amount of the other lubricant is preferably 1 to 10 parts by mass when the total amount of the mineral oil or the synthetic oil, the solid lubricant, the thermosetting resin, and the polymer compound is 100 parts by mass.

The thickness of the coating formed using the die release agent composition can be controlled to 2 to 20 μm. The thickness of the coating is preferably 3 to 15, or preferably 5 to 10 μm. When the thickness of the coating is less than 2 μm, the lubricatability, the heat retainability, or the releasability may present a problem so that the die release agent does not provide sufficient performance. On the other hand, when the thickness of the coating exceeds 20 μm, the releasability deteriorates and the residues of the die release agent components are likely to be deposited on the surface of the die, which may result in undesirable mixing of the die release agent components, the decomposed products thereof, or the like in a formed product. To keep the thickness of the coating within the range shown above, the die release agent composition is normally applied in a quantity of 0.07 to 0.17 cm³, or especially about 0.10 to 0.14 cm³relative to the area of the inner surface of the forming die which is 0.004 m², depending on the shape of the die or the like.

A method for forming the coating on the surface of the forming die, the production of a formed body, and a method for removing the coating after forming are not particularly limited. For example, using such a device as in FIG. 1, the formation of the coating, the production of the formed body, and the removal of the coating can be performed by such a method as schematically shown in FIGS. 2 and 3.

The spray nozzle used during the formation of the coating is not particularly limited. An external-mix dual fluid mixing nozzle such as a dual fluid mixing nozzle with needle valve 1 in FIG. 1 can be used. In FIG. 1, a pipe b is connected to a compressor and a pressurized air from the compressor is transmitted into three pipes through a connector 6. A pipe 63 is provided with a pressure control valve 34 and a pressure tank 4 containing therein the die release agent composition. On the other hand, a pipe 61 is provided with a pressure control valve 32 and a port solenoid valve (electromagnetic valve) 22. Also, a pipe 62 is provided with a pressure control valve 33 and a port solenoid valve 23.

In the device of FIG. 1 described above, into the dual fluid mixing nozzle with needle valve 1, the die release agent under a pressure adjusted to a predetermined value in the pressure tank 4 is supplied from the pipe 63, while an air (air to be sprayed) under a predetermined pressure and at a predetermined flow rate is fed from the pipe 61. In addition, the port solenoid valve 23 is operated through the operation of an electromagnetic valve control timer 5 only for a preset period of time, and an air (control air) is supplied from the pipe 62. By the air (control air), a needle valve is operated and, only during the operation of the foregoing needle valve, the die release agent supplied from the pipe 63 and the air supplied from the pipe 61 are ejected and mixed in the tip portion of the nozzle. At the same time, the die release agent components and the air that have been mixed adhere to the die to form a coating. Then, into the die, a molten metal such as a molten aluminum alloy is supplied, cooled, and then released from the die to produce a formed product.

Also in FIG. 1, a pipe a is connected to the compressor and the pressurized air from the compressor is subjected to pressure adjustment in the pressure control valve 31 and to flow rate adjustment in the port solenoid valve 21. The pressurized air subjected to the pressure adjustment and the flow rate adjustment is blown from an air blow nozzle 40 [see FIG. 3(d)] connected to a pipe c at the coating to remove the die release agent components and the decomposed products thereof which remain on the surface of the die. Thereafter, these steps are repeated.

EXAMPLES

Hereinbelow, the present invention will be described specifically using Examples and also using FIGS. 2 and 3.

In Examples shown below, a steel plate 7 and a cylindrical jig 20 were used to simulate a die. For air blowing for ejecting a die release agent composition for forming a coating and removing the coating after forming, a device as shown in FIG. 1 described above was used.

Examples 1 to 10

[1] Preparation of Die Release Agent Compositions

Into a mineral oil (having a dynamic viscosity of 20 mm²/s at 40° C. measured in accordance with MS K 2283), a paraffin wax (referred to as “wax” in each of Examples 1 to 4, 6, 7, 9, and 10 and Tables 1 and 2) or polybutene (Examples 5 and 8) was mixed at each of the mass ratios shown in Tables 1 and 2 using a typical agitator (Number of Revolutions; 300 rpm) as a device to be dissolved therein. Note that, when the wax is to be contained, the wax was dissolved in the mineral oil by heating and then subjected to the foregoing process. Then, the solid lubricants and thermosetting resins each shown in Tables 1 and 2 were blended at the mass ratios shown in Tables 1 and 2 and agitated using a high-speed agitator (Number of Revolutions; 7000 rpm) to be mixed. Thus, die release agent compositions were prepared.

TABLE 1

Examples

Components(wt %)
1
2
3
4
5

Mineral Oil
85
85
80
85
85

Solid
Type
Talc
Boron
Boron
MoS₂
Boron

Lubricant

Nitride
Nitride

Nitride

wt %
5
5
5
5
5

Thermosetting Resin (Phenol
5
5
10
5
5

Resin)

Polymer
Wax
5
5
5
5
0

Compound
Polybutene
0
0
0
0
5

Total
100
100
100
100
100

TABLE 2

Examples

Components(wt %)
6
7
8
9
10

Mineral Oil
85
85
85
80
80

Solid
Type
Graphite
Graphite
Graphite
MoS₂
Mica

Lubricant
wt %
5
5
5
5
5

Thermosetting
Type
Phenol Resin
Urea Resin
Melamine Resin
Phenol Resin
Phenol Resin

Resin
wt %
5
5
5
10
10

Polymer
Wax
5
5
0
5
5

Compound
Polybutene
0
0
5
0
0

Total
100
100
100
100
100

[2] Performance Evaluation

The performance of each of the die release agent compositions prepared in [1] described above was evaluated for the following items.

(1) Adhering Performance

Each of the die release agent compositions shown in Tables 1 and 2 was loaded into the pressure tank 4 of FIG. 1 and the internal pressure of the tank was adjusted to 0.1 MPa using the pressurized air. Then, the steel plate 7 (made of SKD61 steel and measuring 100×100 mm in length and width and 10 mm in thickness) was placed on a heater. The temperature of the steel plate 7 was measured using a thermocouple 8 inserted therein to a position located 2 mm below the surface of the middle portion of the steel plate 7 in a planar direction and adjusted to the set temperatures of 300° C., 350° C., and 400° C. Then, at each of the set temperatures, 0.3 cm³of the die release agent composition was ejected from the dual fluid mixing nozzle with needle valve 1 at the steel plate 7 to be applied thereto (the distance between the nozzle and the steel plate was 75 mm, a spraying time was 1.8 seconds, and the pressure of an air for spraying was 0.3 MPa) [see FIGS. 2(a) and 3(a)]. Subsequently, the steel plate 7 was naturally cooled to 30° C. The thickness of a coating formed from the die release agent composition and adherent to the steel plate 7 was measured using an electromagnetic film thickness measurement device and the adherability thereof was evaluated. The result of the measurement is shown in Table 3.

Note that each of the film thicknesses in Table 3 is an average value when each of the die release agent compositions was applied three times at each of the set temperatures.

TABLE 3

Die Release Agent
Temperature of Steel Plate (° C.)

Composition
300
350
400

Example 1
8.1
15.1
12.3

Example 2
7.9
13.7
11.8

Example 3
9.4
15.3
12.7

Example 4
2.8
3.1
3.0

Example 5
8.7
15.0
12.2

Example 6
3.3
4.2
5.0

Example 7
4.0
5.2
4.7

Example 8
6.6
8.6
7.3

Example 9
5.3
6.8
6.1

Example 10
7.2
10.1
8.8

Numerical values represent film thicknesses (Unit; μm)

From Table 3, it can be seen that the thickness of the coating considerably widely varies depending on the types of the solid lubricant, the thermosetting resin, and the polymer compound and the blending amounts thereof. Therefore, by considering the type of a molten metal, forming conditions such as a temperature, the peelability of the coating after forming, and the like and adjusting the thickness of the coating to a predetermined value, forming can be performed.

(2) Heat Retaining Performance

In the same manner as at the time of evaluation of the adhering performance in (1) described above, when the steel plate 7 reached the set temperature of 300° C., each of the die release agent compositions was applied onto the steel plate 7 by spray coating to form a coating. Then, as the molten metal, 25 g of a molten aluminum alloy (“ADC12” described in JIS K 2219) at 680° C. was supplied [see FIGS. 2(b) and 3(b)]. Then, the measurement of the temperature of the steel plate 7 was continued and the maximum temperature of the steel plate was checked. In this case, it can be said that, as the maximum temperature of the steel plate 7 is lower, heat is less likely to be transferred from the molten metal to the steel plate 7, i.e., the heat retainability of the coating made of each of the die release agent compositions is higher or, in other words, the heat retaining performance is more excellent. The result of the measurement is shown in Table 4.

TABLE 4

Die Release
Maximum Temperature

Agent Composition
of Steel Plate(° C.)

Example 1
430

Example 2
440

Example 3
435

Example 4
475

Example 5
440

Example 6
465

Example 7
460

Example 8
455

Example 9
435

Example 10
430

From Table 4, it can be seen that the maximum temperature of the steel plate ranging from 430° C. in Examples 1 and 10 to 475° C. in Example 4 has the difference of 45° C. between the lowest and highest temperatures and the heat retaining performance considerably differs depending on the composition of the die release agent composition. Therefore, by considering the heat retainability in conjunction with the other performances such as the adherability, peelability, and the like, the composition of the die release agent composition can be set.

(3) Peeling Performance of Coating

In the same manner as at the time of evaluation of the adhering performance in (1) described above, when the steel plate 7 reached the set temperatures of 300° C., 350° C., 400° C., 450° C., and 500° C., each of the die release agent compositions was applied onto the steel plate 7 by spray coating. Then, the steel plate 7 was held as it was for 30 seconds and then a molten aluminum alloy was supplied thereto in the same manner as for the heat retaining property in (2) described above. Then, the steel plate 7 was allowed to stand still for one minute and the cylindrical jig 20 and a solidified disc-shaped aluminum formed product 30 were removed [see FIG. 3(c)]. Then, from the air blowing nozzle 40 [see FIG. 3(d)] connected to the pipe c of FIG. 1, an air was blown at the coating 10 (see the blown air 40a and the removed coating 10a in FIG. 3(d)). As the result of evaluating the peelability, the coating the entire surface which could be easily removed was rated at A. The coating having the portion that had been in contact with the molten metal and could be easily removed and the portion that had not been in contact with the molten metal and took a longer time to be removed than that taken by the A-rated coating was rated at B. The coating having the portion that had been in contact with the molten metal and the portion that had not been in contact with the molten metal each of which took a longer time to be removed than that taken by the B-rated coating was rated at C. The result of the evaluation is shown in Table 5

TABLE 5

Die Release Agent
Temperature of Steel Plate (° C.)

Composition
300
350
400
450
500

Example 1
C
B
A
A
A

Example 2
C
B
A
A
A

Example 3
C
C
B
A
A

Example 4
C
C
B
A
A

Example 5
A
A
B
C
C

Example 6
B
B
B
A
A

Example 7
B
B
B
A
A

Example 8
A
A
B
C
C

Example 9
C
B
A
A
A

Example 10
C
B
A
A
A

From Table 5, it can be seen that, in each of Examples 1 to 4, 6, 7, 9, and 10 in which the synthetic wax was used as the polymer compound, as the temperature of the steel plate was higher, the peeling performance was improved. It can also be seen that, in each of Examples 5 and 8 in which polybutene was used as the polymer compound, as the temperature of the steel plate was lower, the peeling performance was more excellent. Thus, it is obvious that the peeling performance differs depending on a combination of the polymer compound type and the temperature of the steel plate. On the other hand, each of Example 6 in which the synthetic wax, graphite, and a phenol resin were used respectively as the polymer compound, the solid lubricant, and the thermosetting resin and Example 7 in which the synthetic wax and graphite were used and a urea resin was also used as the thermosetting resin had excellent peeling performance irrespective of the temperature of the steel plate and it can be seen that these die release agent compositions can be used without considering the temperature of the steel plate.

(4) About Types of Thermosetting Resins

Examples 11 to 18

Using the mineral oil used in Example 1 as the mineral oil, the wax used in Example 1 as the polymer compound, the boron nitride used in Example 5 as the solid lubricant, and four types of phenol resins having different average molecular weights as the thermosetting resins, and using two types of melamine resins having different average molecular weights, a diallyl phthalate resin, and a urea resin, die release agent compositions were prepared in the same manner as in Example 1. Also, in the evaluation of the adhering performance described above, the upper-limit temperature of the die temperature at which the film thickness was not less than 10 μm was evaluated as the upper-limit temperature which allows adhesion. In addition, in the evaluation of the peeling performance of each of the coatings, the lower-limit value of the die temperature at which the A rating or the B rating was obtained was evaluated as the lower-limit temperature which allows peeling. The results of the evaluations are shown in Table 6.

TABLE 6

Thermosetting Resin

Average
Upper-Limit
Lower-Limit
Usable Die

Molecular
Temperature Which
Temperature Which
Temperature

Type
Weight
Allows Adhesion(° C.)
Allows Peeling (° C.)
Range (° C.)

Examples
11
Phenol Resin
6000
500
300
250-500

12
Phenol Resin
10,000
550
400
350-550

13
Phenol Resin
45,000
600
500
450-600

14
Phenol Resin
300,000
600
500
450-600

15
Melamine Resin
—
500
400
350-500

16
Melamine Resin
—
500
500
450-500

17
Diallyl Phthalate
—
500
400
350-500

Resin

18
Urea Resin
—
450
300
250-450

From Table 6, it can be seen that the usable die temperature range differs depending on the type of the thermosetting resin. Accordingly, it will understood that the different types of the thermosetting resins are preferably selectively used in accordance with the die temperatures at which the die release agents are used. For example, when a product has a large thickness and accordingly the die temperature is inevitably high, it is preferable to use the phenol resin in Example 13 or 14 having a large average molecular weight. On the other hand, when the die temperature is low in such a case where enhanced cooling is performed to reduce the cycle time of forming, it is preferable to use the urea resin in Example 18 or the like. Thus, it can be seen that the adhering performance and the peeling performance each in accordance with the die temperature can simultaneously be obtained.

(5) About Average Molecular Weights of Phenol Resins as Thermosetting Resins

Examples 19 to 26

Using the mineral oil used in Example 1 as the mineral oil, the wax used in Example 1 as the polymer compound, the boron nitride used in Example 5 as the solid lubricant, and a phenol resin as the thermosetting resin, the die release agent compositions were prepared in the same manner as in Example 1. As the phenol resin, the four types of resins having different average molecular weights and used in Examples 11 to 14 were used. Specifically, using the phenol resins having number average molecular weights of 6000 (Examples 19 and 23), 10,000 (Examples 20 and 24), 45,000 (Examples 21 and 25), and 300,000 (Examples 22 and 26), specimens each as shown in FIG. 4 were produced and two heated iron plates were bonded thereto. Using a tensile tester, the failure shear stress of each of the specimens serving as the index of adherability was measured at 350° C. (Examples 19 to 22) or 500° C. (Examples 23 to 26). The result of the measurement is shown in Table 7 and FIG. 5.

The material of each of two iron plates Fa and Fb used for the production of the specimen in FIG. 4 is SUS304. The dimensions of each of the two iron plates Fa and Fb include a length of 35 mm, a width of 10 mm, and a thickness of 2 mm. A phenol resin layer P formed at one end portion of the iron plate Fa measures about 10 mm in length, about 10 mm in width, and about 0.2 mm in thickness (see FIG. 4(a)). The specimen was produced by placing one end portion of the iron plate Fb heated to 350° C. or 500° C. on top of the phenol resin layer P of the iron plate Fa at a room temperature (25 to 30° C.) and then naturally cooling the iron plates Fa and Fb to a room temperature. The failure shear stress was measured by pinching the other end portions of the iron plates Fa and Fb with the chucks of the tensile tester and pulling the iron plates Fa and Fb in the directions shown by the arrows in FIG. 4(c) at a tensile rate of 0.1 mm/second.

TABLE 7

Number Average
Adhesion Area
Failure Shear

Molecular Weight
Ratio (%)
Stress(Mpa)

of Phenol Resin
(500° C.)
350° C.
500° C.

Examples
19
6000
—
2.48
—

20
10,000

2.32

21
45,000

2.08

22
300,000

0.26

23
6000
73
—
2.27

24
10,000
65

2.12

25
45,000
33

0.23

26
300,000
33

0

From Table 7 and FIG. 5, it can be seen that, in each of Examples 19 to 26, irrespective of a bonding temperature, an adhesion strength decreased as the average molecular weight increased. From this, it will be understood that it is preferable to selectively use phenol resins having different average molecular weights in accordance with forming methods. That is, in a forming method in which the flow of a molten aluminum is weak, such as low-pressure casting, a thermosetting resin having a relatively large average molecular weight is used to allow a die release agent coating which has not peeled under the flow of the molten aluminum to be easily peeled by air blowing after die releasing. On the other hand, in a forming method which requires a high adhesion strength of a die release agent coating, such as die casting or hot forging, a thermosetting resin having a relatively small average molecule weight is used to allow a desired adhesion strength to be obtained.

In association with the consideration of the results of evaluation about the type of the thermosetting resin described above in (4) and the average molecular weight of the phenol resin described above in (5), it is considered that, in general, as the average molecular weight of a thermosetting resin is larger, the viscosity of the thermosetting resin when melted is higher and the thermosetting resin is less likely to be spread over the die surface. It is also considered that, as the average molecular weight is larger, the thermosetting resin sets in a shorter time and therefore the thermosetting resin is less likely to be spread over the die surface. Thus, as the average molecular weight is larger, the bonding area is smaller and the thermosetting resin sets in a shorter time. As a result, a sufficient adhesion strength is not provided and the failure shear stress serving as the index of the adhesion strength tends to decrease.

On the basis of the findings described above, phenol resin powders having different average molecular weights were each sprinkled on iron plates each at a high temperature of 500° C. and the adhesion area ratios of the adhesion surfaces were measured. The result of the measurement is shown in Table 7 and FIG. 6. In this test, the thermosetting resins were sprinkled alone. Accordingly, the result of the measurement may differ from that obtained when the thermosetting resins were sprinkled as die release agent compositions each containing other components. However, from Table 7 and FIG. 6, it can be seen that, as the average molecular weights of the phenol resins are larger, the adhesion area ratios are lower, and accordingly the failure shear stresses are smaller. Therefore, it will be understood that the phenol resins have generally the same tendencies.

Note that the adhesion area ratio (%) means [(Area over Which Phenol Resin is Actually Adherent to Iron Plate)/Area Sprinkled with Phenol Resin Powder)]×100. It can be assumed that, when the temperature is 350° C. and the average molecular weight is 45,000, setting slows down to reduce the viscosity, increase the adhesion area ratio, and increase the failure shear stress. On the other hand, it can be assumed that, when the average molecular weight is 300,000, setting slows down but, due to the originally high viscosity, the adhesion area ratio does not increase and the failure shear stress increases, but only to a slight degree.

Conceivably, it is common with a thermosetting resin that, as the average molecular weight is larger, the viscosity of the thermosetting resin when formed is higher and the time to setting is shorter. Therefore, it can be assumed that another thermosetting resin other than a phenol resin also has the same tendency. That is, it can be considered that not only the phenol resin but also another thermosetting resin such as a melamine resin or a urea resin has the same tendency. By selecting the type of the thermosetting resin in accordance with a forming method and forming conditions such as a die temperature and specifying the average molecular weight in accordance with the required adhesion strength, it is possible to provide an ideal die release agent composition.

INDUSTRIAL APPLICABILITY

The present invention can be used in a technical field in metal die forming, and can be used particularly in a technical field such as low-pressure casting of an aluminum alloy or the like or a squeeze casting method therefore, or die forging.

EXPLANATION OF LETTERS OR NUMERALS

1; Dual Fluid Mixing Nozzle with Needle Valve 21, 22, 23; Port Solenoid Valves (Electromagnetic Valves) 31, 32, 33, 34; Pressure Control Valves 4; Pressure Tank 5; Electromagnetic Valve Control Timer 6; Connector 7; Steel Plate 8; Thermocouple 9; Sprayed Die Release Agent 10; Coating of Die Release Agent 10a; Removed Coating 20; Cylindrical Jig 30; Formed body 40; Air Blowing Nozzle 40a; Blown Air Fa; One Iron Plate Fb; Another Iron Plate P; Phenol Resin Layer

DIE RELEASE AGENT COMPOSITION

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