JPH09183129A - Die for molding resin and manufacture of die for molding polyurethane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily release a molded item and improve hardness of surface and abrasion resistance by applying dispersion plating in which eutectoid of fluorocarbon resin is formed on a plating matrix of nickel and phosphorus at least to a surface of a die to be brought into contact with a molded item. SOLUTION: A dispersion plating in which eutectoid of a fluorocarbon resin is formed on plating matrix of nickel and phosphorus is applied at least to a surface of a die, which is brought into contact with a molded item. The base metal of the die is a cast alloy corresponding to JIS-AC4C and before plating treatment, the surface of the metal is ground. As a pretreatment of plating, alkali etching, mixed acid treatment, zinc substitution, nitric acid treatment, and zinc substitution are usually effected to achieve dispersion plating in which eutectoid of tetrafluoroethylene resin is formed on plating matrix of nickel and phosphorus. As plating liquid, liquid containing nickel supply material, reducing agent, surface-active agent, and PTFE supply agent is used and the base metal is plated by electroless plating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for molding a resin and a method for manufacturing the same, and more particularly to surface treatment of a surface in contact with a molded product.

[0002]

2. Description of the Related Art When molding a resin, it is common to mass-produce a resin using a mold in order to make the surface roughness constant and to facilitate the die cutting. Particularly, in the case of molding polyurethane, heat is applied to carry out urethane reaction injection molding, so that molding is performed by a mold.

In the molding of resin, since a molded product easily adheres to the surface of the mold, a wax-based mold release agent is sprayed onto the surface of the mold before molding. In particular, polyurethane has a rough surface and low strength. Therefore, when molding is performed without using a mold release material, the surface of the molded product is torn off at the time of mold release and adheres to the surface of the mold. Then, the outer shape of the molded product will be chipped as much as it adheres to the mold,
The appearance is remarkably inferior. Therefore, it is necessary to apply a wax-based release agent to the mold when molding the resin, particularly when molding the polyurethane. However, in this case, not only the material cost of the release agent and the coating equipment but also the time and labor cost for the steps required for coating and wiping are involved, and the molding cannot be performed at low cost.

Japanese Utility Model Application Laid-Open No. 57-183137 proposes a mold having a male mold surface coated with tetrafluoroethylene resin (trade name: Teflon). In this mold, since it is not necessary to apply a mold release agent before molding, reduction in time and cost required for molding can be expected. However, since the coating film of tetrafluoroethylene resin is soft, it may be worn by a metal tool when the mold is attached or detached, or may be peeled off when cleaning. Also, when storing the mold, extreme care must be taken not to damage the coating.

[0005]

According to the present invention, a molded article can be easily released from the mold without using a wax-based mold release agent at the time of resin molding, and the surface is hard and has excellent abrasion resistance and easy to handle. Provided is a resin molding die.

[0006]

In order to achieve the above-mentioned object, in the present invention, a dispersion plating in which a fluororesin is co-deposited in a plating matrix of nickel and phosphorus on at least the surface of the mold that contacts the molded product. It has a structure.
In particular, for a polyurethane molding die, a plating solution containing nickel and phosphorus and a tetrafluoroethylene resin (hereinafter abbreviated as PTFE) having a suspension amount of more than 3 g / l and less than 24 g / l is used. A manufacturing method was adopted in which a metal mold was plated, or after the metal mold was plated, a heat treatment of 250 ° C. to 300 ° C. was performed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The base material of the mold is an aluminum casting alloy corresponding to JIS AC4C, and the surface is polished before the plating treatment. In general, an aluminum die has a material formed by casting, and therefore, a base material of the die may have cavities. In this case, even if plating is performed, fine irregularities remain on the surface and the releasability is poor, so surface polishing is necessary. Surface polishing is performed by blasting, resin impregnation, or sand paper to the extent that the surface roughness is made uniform. If a wrought material is used as the base material of the mold, the cavities disappear during wrought, so that the surface polishing treatment can be omitted. FIG. 1 shows a pretreatment procedure for performing the plating treatment of the present invention. The surface-polished base material is subjected to the steps of alkaline etching, mixed acid treatment, zinc substitution, nitric acid treatment, and zinc substitution as in the pretreatment for plating as follows, and it is treated with nickel and phosphorus. Dispersion plating (Ni-P-PTFE plating) in which a tetrafluoroethylene resin was co-deposited on the plating matrix was performed.

The plating solution contains nickel supply material (trade name)
Enplate NI-428A) 60 ml / l, reducing agent (trade name Enplate NI-428B) 180 ml / l
l, surfactant (trade name: Enplate EN-987
7) A base material is plated by electroless plating using 10 ml / l and a PTFE supply agent (trade name: Enplate Dispersion).

The suspension amount of PTFE in the plating solution is 3
It is mixed so as to exceed g / l and less than 24 g / l. More preferably, the amount of PTFE suspended in the plating solution is 6 g /
1 to 12 g / l. According to experiments,
As shown in the table below, the amount of PTFE suspended was 6 to 12 g / l.
At the time of, good releasability was observed.

[0010]

[Table 1]

The amount of PTFE suspended in the plating solution is 3 g / l.
In the following cases, the amount of PTFE particles co-deposited in the plating film is small, so that the releasing effect is hardly seen. Further, when the amount of suspension is 24 g / l or more, the matrix of nickel and phosphorus is difficult to grow, and thus it is difficult to form a plating film.

The particles of PTFE suspended in the plating solution are
The diameter is preferably 1 μm or less, more preferably finer, that is, 0.2 μm or less. If the PTFE particles are large, the sedimentation speed in the plating solution is high, and it is difficult to uniformly suspend the particles in the plating solution. Further, since PTFE has poor wettability due to its properties, a surfactant such as Enplate EN-9877 is used.
Is dispersed in the plating solution in an appropriate amount, but when the particles are large, the amount of the surfactant adsorbed per volume is small and it is difficult to disperse in the plating solution. A sufficient amount of PT on the plating surface
Since it is necessary to increase the filling rate of PTFE in the plating solution in order to disperse FE, it is preferable that the particle size of PTFE is small.

FIG. 2 is an enlarged photograph of a cross section of the mold formed by the above method, and the lower light-colored part shows the aluminum alloy of the mold material. The band-like shape near the center of FIG. 2 is the plating film. Although fine black spots are visible on the plated coating, the black spots are PTFE particles that have been co-deposited. FIG. 3 is a further enlarged photograph of the surface of the plated coating, and it can be seen that a large number of circular PTFE particles are dispersed. In addition, each PTFE particle has a diameter of about 0.2 μm.

Since the plating adopted in the mold of the present invention uses a matrix of nickel and phosphorus, the hardness can be increased by heat treatment. The matrix of nickel and phosphorus has the highest hardness by heat treatment at 350 ° C, but the heat resistance temperature of PTFE is 30
Since the temperature is 0 ° C., when the heat treatment is performed in the temperature range of 250 ° C. to 300 ° C., the plating hardness of about Hmv200 can be obtained under the above various conditions without degrading the PTFE.

It is desirable to finish the surface roughness after plating to Ra 0.8 μm or less. When the surface roughness is large, the resin has a so-called anchor effect in which it digs into the unevenness of the plating surface during resin molding, and the releasability deteriorates. In particular, when molding polyurethane, the effect of surface roughness is significant. The following table shows the result of an experiment conducted by changing the plating surface roughness when molding polyurethane.

[0016]

[Table 2]

The releasability depends on the eutectoid amount of PTFE and the surface roughness after plating, but it is necessary to actually mold the resin in order to judge whether the releasability is good or bad. However, since a large amount of equipment is required to mold the resin, many experiments are limited. As a method for easily determining the releasability, it is possible to measure the contact angle. The following table is an experiment conducted on the contact angle between the resin molding die of the present invention and water, and whether the releasability is good or bad.

[0018]

[Table 3]

According to the results of this experiment, it can be seen that good releasability can be obtained when the contact angle is 106 ° or more. Therefore, it is possible to know the approximate releasability by measuring the contact angle at the stage of plating, without actually molding the polyurethane for each experiment.

In the above embodiment, the releasability of the polyurethane was improved by co-depositing PTFE on the nickel and phosphorus plating matrix. Instead of PTFE, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin was used. Various resins can be obtained by using (PFA) particles, tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP) particles, or by mixing two or more kinds of PTFE, PFA and FEP particles. The mold releasability can be exhibited.

The plating solution used for electroless plating is
In addition to the commercially available products as described above, nickel nitrate or nickel chloride 21 g / l as a nickel metal salt, lactic acid 28 g / l as a pH buffering agent, propionic acid 2.3 g / l as a complexing agent, and hypochlorous acid as a reducing agent. Sodium phosphate 21
It is also possible to use a mixture of g / l, PTFE and a surfactant in an appropriate amount. In this case, the temperature of the plating solution is 90
C is desirable. In addition to the above, as a plating solution for electroless plating, nickel nitrate or nickel chloride as a nickel metal salt 26 g / l, sodium acetate 26 g / l as a pH buffer, sodium citrate 15 g as a complexing agent
/ L, 16 g / l of sodium hypophosphite as a reducing agent, and a mixture of PTFE and a surfactant in an appropriate amount,
It is also possible to maintain the temperature at about 90 ° C. for plating.

Further, when plating is performed by the electroplating method, nickel nitrate is 200 to 300 g / l, nickel chloride is 40 to 50 g / l, boric acid is 30 to 50 g / l, and sodium hypophosphite is 1 to 5 g / l. Fluorine resin (PTF
E) and a suitable amount of surfactant mixed plating solution,
Keeping at 3.8 to 4.5 and plating at a temperature of 40 to 70 ° C, nickel chloride 5 to 15 g / l, boric acid 35 to 48
g / l, nickel sulfamate 550 to 650 g /
It is also possible to carry out plating at a temperature of 50 to 70 ° C. while maintaining a pH of 4.0 to 5.0 with a plating solution prepared by mixing 1 and 1 to 5 g / l of sodium hypophosphite with a fluororesin (PTFE) and a surfactant. it can. When a plated coating is produced by electroplating, a cationic surfactant is used. This is because neutral fluorine particles (PTFE particles) are positively charged and easily attracted to the negative electrode of the plating matrix. Further, in the electroplating method, since the nickel ion has a larger migration amount than the cationic complex of the fluororesin (PTFE), the eutectoid amount tends to be small. Therefore, the current density is set to 0.5 to 6 A / dm ^{2 which} is smaller than that in general electroplating so that the same amount of eutectoid as in electroless plating can be obtained.

From the viewpoint of wear resistance and scratch resistance, the thicker the plating is, the more advantageous it is. However, since the releasability can be maintained even if the plating film is thin, the time required for plating is taken into consideration. It is desirable that the thickness is 1 to 10 μm.

[0024]

According to the resin molding die of the present invention and the polyurethane production die produced by the production method of the present invention, since the fluororesin can be dispersed and arranged in the plating film, It is possible to realize a mold having both the releasability of the resin at the time of resin molding and the surface hardness of the plating. Therefore, the materials, equipment, time, and labor costs required for applying and wiping the mold release material are unnecessary, resin molding can be performed inexpensively, and even when the mold is attached and removed, there is no wear due to metal tools, and the mold surface is cleaned. Sometimes it does not get scratched or the surface peels off.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pretreatment procedure for performing a plating treatment of the present invention.

FIG. 2 is an enlarged photograph of a cross section of the surface of a mold to which the present invention is applied.

FIG. 3 is an enlarged photograph of the mold surface.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 23, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2 is a photograph showing a metallographic structure of a cross section of a mold surface to which the present invention is applied.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3 is a photograph showing the metallographic structure of the mold surface.

Claims (4)

[Claims] 1. A mold for resin molding, characterized in that at least a surface of the mold which comes into contact with a molded product is subjected to dispersion plating in which a fluororesin is co-deposited in a plating matrix of nickel and phosphorus. 2. The mold for resin molding according to claim 1, wherein the mold is for polyurethane molding. 3. Nickel, phosphorus, and a suspension amount of 3 g / l
A method for producing a resin molding die, which comprises plating the die with a plating liquid containing more than 24 g / l of a tetrafluoroethylene resin. 4. The method of claim 3, wherein after the die is plated, a heat treatment at 250 ° C. to 300 ° C. is applied.
A method for producing the polyurethane molding die described.