JPH02120397A - Lubricating and releasing agent - Google Patents

Abstract

PURPOSE:To obtain a lubricating and releasing agent capable of forming a uniform coating film excellent in both lubricity and mold release properties even when continuously applied to a material surface at temperatures in a wide range, by dispersing a specified BN powder, a water-soluble phosphoric acid salt, a colloidal silica, and an anti-settling agent of clay base in water containing a dispersant. CONSTITUTION:1-35wt.% BN powder (a) wherein the mean particle diameter of the primary particle is 0.5-20mum, a water-soluble phosphoric acid salt (b) (e.g., sodium phosphate) in an amount sufficient to provide a weight ratio of (a) to (b) of 2 to 100, 0.1-20wt.% (on an SiO2 basis) colloidal silica (c) having a particle diameter of 1-1000nm, and 0.5-5wt.% anti-settling agent (d) of clay base are homogeneously mixed and dispersed in water containing 1wt.% or less dispersant (e.g., sodium lignosulfonate) using, e.g., a ball mill.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention provides a heat-resistant high-temperature solid lubricant using hexagonal boron nitride (hereinafter referred to as BN) powder or an aqueous dispersion for use as a mold release agent. The present invention relates to a composition.

<Prior Art> The lubricating mold release agent of the present invention is mainly used as a high-temperature solid lubricant during extrusion molding of aluminum or aluminum alloy, or as a mold release agent for high-temperature molds such as aluminum die casting. Conventionally, as this type of lubricating mold release agent, an oil-based or water-based emulsion type agent in which graphite powder is dispersed has been used. Such conventional lubricating mold release agents based on graphite powder and organic binder have many drawbacks as follows.

In other words, (1) Graphite easily reacts with aluminum or its alloys, and when used as a lubricant or mold release agent, it is hot on the surface of aluminum or its alloys.
It forms compounds such as Cs and leads to defects in extruded and cast aluminum products.

(2) When the organic binder is heated to 200°C or higher, it decomposes and generates a large amount of gas, causing porous defects on the surface of the aluminum die-cast product.

(3) As mentioned in (2), the large amount of gas and black graphite powder generated greatly deteriorates the working environment.

In order to solve the above-mentioned problems, a high-temperature mold release agent mainly containing BN powder has been proposed, as disclosed in Japanese Patent Application Laid-Open No. 55-29506. With such a lubricating mold release agent mainly composed of BN powder, the above-mentioned (]) to (3) can be achieved.
The problems shown can be solved to a large extent.

However, when the surface to be coated is heated to a high temperature of 150'c or more, a uniform and good coating film is not necessarily formed.

Further, even if a coating film is formed at 150°C or lower, it often peels off when heated to 300°C or higher.

The present inventors solved the above problems and developed a lubricating mold release agent that forms a uniform coating film even when applied to the material surface at any temperature from room temperature to high temperature, and the patent application was filed in 1988. 104
It has been filed as No. 348.

This is a water-based lubricating mold release agent that can form a coating film with good lubricating mold release function even at 300° C. or higher by adding water-soluble phosphate and colloidal silica to BN powder.

However, if the above-mentioned lubricating mold release agent is left standing, the BN powder will settle, so it must be stirred from time to time, and if it is applied continuously for a long time by spraying, etc., the spray gun may become clogged. However, there was a problem in that the film thickness varied between the initial and final stages of spraying. Furthermore, during coating, especially when the amount of BN powder is small, the low viscosity may cause dripping, which may cause fluctuations in the lubricating and releasing properties of the coating film, which may adversely affect productivity.

<Problems to be Solved by the Invention> The purpose of the present invention is to solve the above-mentioned problems in conventional graphite powder-organic binder-based lubricating mold release agents or mold release agents containing BN powder instead of graphite powder, and to Even when applied continuously for long periods of time to material surfaces at any temperature up to high temperatures,
To provide a water-based lubricating mold release agent that can be applied without dripping, forms a uniform coating film, and does not contaminate the working environment.

Means for Solving the Problems> The present inventors prepared a composition consisting of BN powder and various inorganic binder clay-based anti-settling agents, and sprayed it on surfaces to be coated at various temperatures. As a result of investigating the properties, lubricity, etc. of the coating film formed, it was found that the water dispersion composition containing BN powder, water-soluble phosphate, colloidal silica, and clay-based antisettling agent had good coating properties without dripping. The present inventors have discovered that it has excellent properties, can form the most uniform coating film, and has excellent lubricity and mold release properties, leading to the present invention.

That is, the present invention provides boron nitride powder, water-soluble phosphate,
An aqueous dispersion composition containing colloidal silica and a clay-based antisettling agent, wherein the boron nitride powder has an average primary particle diameter of 0.5 to 2 h and a concentration of 1 to 2 h in the aqueous dispersion composition.
35% by weight, the mixing ratio of boron nitride powder and water-soluble phosphate is 2 to 100 expressed as a weight ratio of boron nitride powder/water-soluble phosphate (anhydride), in a water dispersion composition of colloidal silica. The concentration of the clay-based antisettling agent in the water dispersion composition is 0.1 to 20% by weight expressed as SiO2, and the concentration of the clay-based antisettling agent is 0.3 to 5% by weight.
The lubricating mold release agent is characterized in that the remainder consists of water and a dispersant.

<For production> The present invention will be explained in detail below.

The reason why the aqueous dispersion composition of the present invention has lubricity and mold release properties is due to the properties of the BN powder blended as a basic component. BN is a layered compound of graphite and 1s region, and has chemically stable properties against M and the like. The lubricity function is expressed by the sliding of the layered compound between the eyebrows. ++1
Type 1 property is mainly related to reactivity with metals such as AI (related to this, BN has lower reactivity with molten M than graphite,
Using BN powder has better mold releasability than using graphite powder.

In the present invention, the particle size of the BN powder to be blended is limited to 0.5 to 20 by taking the average particle size of the primary particles.

If the average particle size is smaller than 0.5n, it will be difficult for the BN powder to exhibit lubricity, and if it exceeds 20Fm, it will be difficult to uniformly disperse it in water even if a dispersant is added.

In the present invention, the concentration of the aqueous dispersion composition of BN powder is 1
-35% by weight. The concentration of BN powder is 1% by weight
Even if it is smaller or exceeds 35%, uniform coating becomes difficult and mold release properties become poor.

In the present invention, a water-soluble phosphate is used as a binder for the BN powder. The type of water-soluble phosphate is not particularly limited, but in addition to sodium phosphate, potassium phosphate, and ammonium phosphate, water-soluble magnesium phosphate monophosphate, aluminum phosphate, zinc phosphate, and the like are also preferably used. The water-soluble phosphate completely dissolves in the aqueous dispersion composition of BN powder, and when the aqueous dispersion composition dries on the surface to be coated, it becomes a binder and stabilizes the lubricating BN powder uniformly in the coating film. Holds and lubricates as a coating.

This is to impart a mold releasability function.

In the present invention, the blending ratio of BN powder and water-soluble phosphate is limited to 2 to 100 expressed as a weight ratio of BN powder/water-soluble phosphate (anhydride). If there is too much water-soluble phosphate as an inorganic binder, the function of the film of the water-soluble phosphate will outweigh the lubricating and mold-releasing functions of the BN powder, making it difficult to use as a lubricating mold-releasing agent for the purpose of the present invention. On the other hand, if the weight ratio is more than 100, the amount of inorganic binder is too small to hold the BN powder in the coating film, so it cannot function as a lubricating mold release agent.

In the present invention, in addition to the BN powder and water-soluble phosphate described above, colloidal silica is further blended.

In the present invention, colloidal silica has a particle size of 1 to IQ.
The purpose of blending such colloidal silica with particles in a dispersed state of OQnm Stow or its hydrate is to uniformly disperse the SiO□ component in the coating film, thereby improving the uniformity and homogeneity of the coating film. It is about improving sexuality. Furthermore, the heat resistance of the coating film can also be improved by solidly dissolving the SSO component in the water-soluble phosphate binder.
In the present invention, 0.1 to 20% by weight of colloidal silica is blended. If the blending amount is lower than 0.1% by weight, there is no effect of blending, and if the blending amount is higher than 20% by weight, only a hard 1R coating film containing a large amount of 5IOI will be formed, and a coating film with lubricity cannot be formed.

In the present invention, a clay-based antisettling agent is further added in an amount of 0.3 to sTi, but if it is less than 0.3% by weight, the clay-based antisettling agent has an anti-settling effect, a dripping prevention effect, and a coating when applied. This is because it cannot be expected to improve the uniformity of the film, and if it exceeds 5% by weight, it becomes too clayey and it becomes difficult to coat a uniform film, and it is not possible to form a coating film with lubricity at high temperatures. .

Clay-based anti-settling agents are usually called rheological additives and are organic base complexes of clay minerals, which are produced by refining natural montmorillonite-based clay minerals and reacting them with organic compounds. When such an anti-settling agent is blended into a paint or the like, it has a remarkable thickening effect, and can provide an effect of preventing the settling of pigments and improving the uniformity of the coating film when applied.

In the case of the present invention, one of the purposes of adding water to the itm composition is to prevent sedimentation in the dispersion of BN powder, and the other purpose is to prevent settling of the BN powder in the dispersion liquid.
The first reason is to improve the uniformity of the coating film thickness when applied with a spray gun or the like.

Although a wide range of organic base complexes of clay minerals can be used as the clay-based antisettling agent used in the present invention, for example, a rheology additive (trademark "Bentone") manufactured by NL Chemicals is suitably used in the present invention.

In the present invention, the above-mentioned BN powder, water-soluble phosphate, colloidal silica, and clay-based antisettling agent are dispersed or melted in water to prepare a lubricating mold release coating agent for a water-dispersed composition. , a small amount of dispersant is added, 0 dispersant is B
It is added to uniformly disperse N powder in water.
In the present invention, dispersants IIIW are not particularly limited, but those that act as ordinary surfactants are used.
For example, sodium lignin sulfonate and carboxymethyl cellulose can be used, and the amount thereof is preferably 11% or less.

The lubricating mold release agent of the present invention is prepared by uniformly mixing various raw materials such as BN powder in a ball mill, etc. to form a slurry with a water phase, and can be applied by brushing or spraying. The thickness of the coating film after drying is preferably 100 mm or less, considering economic efficiency.

The lubricating mold release agent of the present invention can be used at low temperatures of around 100°C.
It can be applied to material surfaces at temperatures as high as 00°C or higher, and a uniform coating film with good adhesion is formed. In other words, the optimal B
Average particle size and amount of primary particles of N powder, type of water-soluble phosphate.

rfi amount ratio of BN powder/water-soluble phosphate (anhydrous).

Amount of addition of clay-based anti-settling agent 1 The type and amount of dispersant to be added and slurry thickening can be selected as appropriate.

<Example> Using BN powder with an average primary particle diameter of 4.5-
Aqueous dispersion compositions of various compositions of BN powder-water-soluble magnesium phosphate-colloidal silica-clay-based antisettling agent (“Bentone” trademark manufactured by NL Chemicals) shown in the table were prepared and sprayed with a spray gun. It was applied to the surface of the plate to a film thickness of about 10 On, and the appearance of the resulting coating film was examined. Furthermore, the lubricity was examined by a ring-on-ring test using a friction and wear tester, and then the stainless steel plate with the coating was immersed in molten M at 700°C, and the releasability was also evaluated by the reactivity between the coating and the molten M. did. The results are shown in Table 1 along with comparative examples.

As is clear from Table 1, the lubricating mold release agent made of the aqueous dispersion composition of the present invention is easy to use, forms a uniform coating film,
This coating film has a small coefficient of friction, so it has excellent lubricity, and since it has low reactivity with molten AI, it also has excellent mold releasability.

<Effects of the Invention> The lubricating mold release agent consisting of the BN powder-water-soluble phosphate-colloidal silica-clay-based antisettling agent water dispersion composition of the present invention can be used at any time from room temperature to high temperature. It is an industrially useful lubricating mold release agent that can form a coating film with excellent uniform lubricity and mold release properties even when applied to the surface of a material at a temperature of .

Claims (1)

[Claims] An aqueous dispersion composition containing boron nitride powder, water-soluble phosphate, colloidal silica, and a clay-based sedimentation inhibitor, wherein the boron nitride powder has an average primary particle size of 0.5 to 20 μm, and The concentration in the dispersion composition is 1 to 35% by weight, the mixing ratio of boron nitride powder and water-soluble phosphate is 2 to 100 expressed as a weight ratio of boron nitride powder/water-soluble phosphate (anhydride),
The concentration of colloidal silica in the aqueous dispersion composition is SiO_2
A lubricating release agent characterized in that the concentration of the clay-based antisettling agent in the water dispersion composition is 0.3 to 5% by weight, and the balance is water and a dispersant. molding agent.