JPS585109B2 - Casting surface processing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for surface processing a casting.

More specifically, the present invention relates to a surface processing method for castings that forms a plastic coating without pinholes or irregularities.

Conventionally, the aesthetic finishing of various types of castings has been achieved through a number of painting processes.

By the way, castings have many irregularities, pores, pinholes, etc. on the casting surface compared to ordinary steel materials, so when performing various aesthetic finishes, it is necessary to use a buffing process, putty process, primer coating, surfacer coating, and top coating. It requires various processes such as painting, and therefore, a beautiful finish is achieved through at least three or four painting processes.

To explain the conventional beauty finishing method for castings using a specific example, for castings that have been buffed or for castings that are not very uneven, first a degreasing process is performed without buffing to remove oil, dirt, etc. Afterwards, a wash primer or chemical conversion coating treatment was applied, followed by a putty process to fill in cracks, holes, pinholes, etc.

However, since the putty used is required to have good filling properties and good abrasiveness, the resulting coating was relatively porous and had low strength.

Furthermore, since the putty application process is often performed partially, the polished surface tends to be somewhat uneven.

However, in order to correct such unevenness and at the same time prevent suction of the top coat, after the SAFACER painting process, the resulting SAFACER coating film is wet-sanded, and if necessary, the SAFACER paint film is wet-sanded again. The usual process is to complete the finishing process by applying an intermediate coat and a top coat, and therefore, as mentioned above, it was inevitable that a large number of processes were required.

Furthermore, when using conventional solvent-based paints, not only is it not possible to apply thick coats in one coat, but even if you apply thick coats, the painted surface will sag,
Because coating film defects such as pinholes are likely to occur, it was necessary to apply the coating in several batches.

As a method to omit these numerous work steps, a method has also been adopted in which a powdered plastic that can be coated thickly in one step is applied and heat-fused to obtain a plastic layer.

However, the finished appearance was not satisfactory.

That is, as mentioned above, the surface of the casting has many significant irregularities, large diameter pinholes, and pores, and it is impossible to completely eliminate these in the casting manufacturing process. be.

Therefore, if powdered plastic is directly applied to the surface of the casting in this condition and heated and melted, the plastic that is commonly used has poor fluidity due to its high viscosity when melted, and there are sufficient holes and pinholes. It does not penetrate into the
As a result, the air remaining in the burrow foams during the formation of the plastic layer, creating pinholes that penetrate the surface of the plastic layer and causing unevenness on the surface. Therefore, it caused poor finished appearance and decreased corrosion resistance, which was not preferable.

The present invention aims to provide a surface processing method for castings that improves or improves the defects found in known techniques and has excellent finished appearance.

That is, the present invention provides: (a) a composition consisting of the following composition on the surface of the casting, namely (a) 100 parts by weight of a mixture consisting of 100 to 30% by weight of cement and 0 to 70% by weight of aggregate; (b) polyvinyl Acetal resin and/or polyvinyl alcohol resin 2-1
5 parts by weight and (c) applying an appropriate amount of water and solidifying it to obtain a primer coat layer, and (b) applying powdered plastic to the surface of the obtained primer coat layer and heat-melting it to form a plastic. The present invention relates to a method for surface processing a casting, which comprises the steps of: obtaining a layer;

The "cement" used in the primer coat composition of the present invention may be a commonly used hydraulic cement.

Typical examples include Portland cement, white Portland cement, alumina cement, pozzolan cement, truss cement, pozzolan Portland cement, silica cement, blast furnace cement, and fly ash cement.

Furthermore, the "aggregate" used in the primer coating composition of the present invention includes sand, gravel, sand stone, silica sand, emery,
In addition to metal powder, etc., talc, calcium carbonate, magnesium sulfate, iron oxide, red lead, zinc chromate, zinc powder, etc.
Known and generally easily available inorganic fine powders can be suitably used.

In the present invention, the mixing ratio of cement and aggregate is 100 to 30% by weight of cement, 0 to 70% by weight of aggregate, preferably 100 to 50% by weight of cement, and 0 to 50% by weight of aggregate. It is.

In the above, if the amount of cement is less than 30% by weight, the primer coat layer will lack toughness and is not preferred as a primer coat layer for a plastic layer.

The "polyvinyl acecool resin" used in the primer coating composition of the present invention includes water-soluble and water-insoluble resins, such as polyvinyl formal resin, polyvinyl acetoacetal resin, polyvinyl butyral resin, etc. .

More specifically) Commercially available water-soluble polyvinyl acecool resins include Eslec W) Eslec W2O.
1 (Tanesui Kagaku Kogyo ■Cracked product name), and the water-insoluble polyvinyl acecool resin preferably has an average degree of polymerization of 250 to 20,001 from the viewpoint of water resistance, adhesion to metal surfaces, mixability of the composition, etc. is 250~100o1
Butyralization degree 57-75 molar ratio preferably 57-70
A molar polyvinyl butyral resin is preferably used.

In the present invention, when the polyvinyl acetal resin is a water-soluble resin, it may be dissolved in water and used alone as an aqueous solution of the polyvinyl acetal resin, but when it is a non-water-soluble resin, the polyvinyl acetal resin is mixed with an organic It is necessary to dissolve it in a solvent and use it as a mixture of a polyvinyl acetal resin aqueous solution and a polyvinyl acecool resin organic solvent solution.

The mixing ratio is water-soluble polyvinyl acecool resin 99~
100 parts by weight of water-insoluble polyvinyl acetal resin, preferably 90 to 700 parts by weight of water-insoluble polyvinyl acetal resin per 40 weight Mogami
~70 parts by weight Water-insoluble resin 10-300-30 parts by weight The "polyvinyl alcohol resin" used in the composition required for primer coating of the present invention has a degree of saponification of 86 molar or higher, and can be washed with cold or hot water. Among them, from the viewpoint of working viscosity, the average molecular weight is 1500.
The following is desirable.

For example Solsiden DF-107, DF-108, DF
-605N, DF-402, 120 to Denka Poval,
Ni-17, Ni-05, B-17R, W-24, B-24
, B-20, B-05, B-03C and above manufactured by Denki Kagaku Kogyo ■, Kuraray Bobber/L/PVA-105, P
VA-107.

PVA-110, PVA-204, PVA-215, P
VA-210, PVA-217 [Kuraray dehiscence product name above], Hi-Selon H, Hi-Selon S, Gohsenol NH
Commercially available resins such as -20, NH-18, GH-17, GH-05 [the above names of split products of Nippon Gosei Chemical Industry Co., Ltd.] can be suitably used.

In the present invention, the characteristics of each resin can be brought out by using a water-soluble polyvinyl acetal resin or a water-soluble polyvinyl alcohol resin alone or in combination of two or more, or by mixing both in an arbitrary ratio. It becomes possible.

In the present invention, rather than using water-soluble polyvinyl alcohol resin or polyvinyl acetal resin alone or in combination as described above, water-soluble polyvinyl acetal resin and water-insoluble polyvinyl acetal resin are used from the viewpoint of water resistance of the primer coat layer. It is most preferable to use an appropriate mixing ratio.

In the present invention, cement or cement, aggregate mixture 1
The amount of the polyvinyl acetal resin or polyvinyl alcohol resin added to 00 parts by weight is 2 to 15 parts by weight, preferably 4 to 8 parts by weight.

In the above, if the amount of resin added is less than 2 parts by weight, pinholes are likely to occur in the primer coat layer, and furthermore, after forming the plastic layer, the plastic coated casting may be rapidly cooled or the coated casting may be placed in a cold region. However, it is not preferable to expose the primer coat to cold and repeated environmental conditions, as this will cause cracks and embrittlement of the primer coat layer.

On the other hand, when the amount of the resin added is more than 15 parts by weight,
The viscosity during application of the primer coat layer is extremely high, which poses operational problems, and the surface of the primer coat layer becomes too dense, which tends to cause blistering during the process of thermally melting the powdered plastic.

of cement or cement and aggregate, as in the present invention.

By using a composition in which the mixture and the above amount of resin are combined in the primer coat layer, the effect of completely filling the irregularities, pinholes, and pores peculiar to castings is imparted, and the resin in the primer coat layer is After the plastic layer is formed, the layer is made fine and the plastic becomes fluid and floats to the surface of the primer coat layer during setting or in powder form. , a smooth, pinhole-free plastic-coated casting can be obtained.

Furthermore, due to the plasticity imparting effect of the resin, the primer coat layer does not generate cracks or peel off despite thermal changes such as rapid cooling, and is suitable as a primer coat layer for various uses such as the present invention.

The composition required for primer coating of the present invention contains an appropriate amount of water as an essential component, but the water is added to solidify the cement, dissolve the resin, and obtain an appropriate viscosity during coating work, and the amount of water is particularly important. There is no intention to limit the ratio.

In addition to the above-mentioned essential components, the present invention further includes, if necessary, those conventionally used in concrete compositions, such as setting accelerators such as sodium silicate and aluminum chloride, and surfactants such as nonionic or anionic surfactants. agent,
Reinforcing materials such as asbestos, glass flakes, and glass fibers,
A surface conditioner, antifoaming agent, etc. may be added.

As the "powdered plastic" for obtaining the plastic layer of the present invention, a thermosetting or thermoplastic resin that is solid at room temperature and can be processed into powder by chemical or physical methods is used.

The above-mentioned thermosetting plastics are those that contain in their molecules the groups necessary to react with each other and form a crosslinked structure when heated, and may contain one type or a combination of two or more types. good.

For example, combinations of groups that react with each other include carboxyl group (including acid anhydride group) - epoxy group, carboxyl group (including acid anhydride group) - hydroxyl group, hydroxyl group, epoxy group, hydroxyl group - hydroxyl group, hydroxyl group - blocked isocyanate. Typical examples include a group, an epoxy group to an amino group, a hydroxyl group to a methylol group, and a hydroxyl group to an etherified methylol group.

More specifically, melamine resin to alkyd resin, acrylic resin to alkyd resin, acrylic resin to melamine resin, self-curing acrylic resin, epoxy resin to phenol resin, epoxy resin to polyamide resin, polyester resin to block isocyanate resin, epoxy resin - Acid anhydrides etc. are mentioned as a typical combination.

On the other hand, the thermoplastic plastics include polyvinyl butyral, cellulose acetate, polyvinyl chloride, poly(meth)acrylate, acryladol methacrylate copolymer, saturated polyester, polyethylene, polypropylene, nylon, ethylene acrylic copolymer, Typical examples include ethylene-vinyl acetate copolymer, vinyl acetate resin, styrene-butadiene copolymer, and derivatives thereof.

The powdered plastic of the present invention has the above-mentioned composition as a basic component, but of course, coloring pigments such as iron oxide, titanium oxide, and carbon black, anticorrosive pigments such as zinc chromate, red lead, and strontium chromate, talc, A mixture of various materials commonly used in paints and powder coating compositions, such as extender pigments such as barium sulfate and calcium carbonate, surface conditioners, anti-blocking agents, plasticizers, stabilizers, anti-sagging agents, etc. Good too.

The surface processing method for castings of the present invention applies to the surfaces of castings from which dirt, oil, rust, etc. have been removed by chemical or physical methods.
The composition required for primer coating is applied to a desired film thickness, e.g., about 100 to 1000 microns, by a known method such as brushing, roller, spraying, spatula, or rotary coating, and is subjected to conditions necessary for the cement to harden, e.g., left to stand naturally. , leave to stand by steam curing etc. to first obtain a primer coat layer.

Next, if necessary, powdered plastic is applied to the surface of the primer coat layer, which has been previously heated to about 120 to 300°C, maintained at the temperature conditions necessary to form a plastic layer, and then cooled naturally or rapidly. Obtain a plastic coating for the casting.

In the method for obtaining a plastic layer according to the invention, the application of the powdered plastic is not necessarily limited to one time.

For example, it is also possible to apply a thermoplastic powdered plastic and heat melt it, and then apply a thermosetting powdered plastic to form a plastic layer.

Hereinafter, specific effects of the present invention will be explained using examples.

In addition, "part" or "%" in Examples and Comparative Examples indicates "part by weight" or "% by weight."

Example 1 A composition consisting of 100 parts of ordinary Portland cement, 25 parts of a water-soluble polyvinyl acetal resin aqueous solution [Tanezu Kagaku Kogyo, product name: ESLETSUKU W, nonvolatile content 25%], and 25 parts of tap water was thoroughly mixed to prepare a primer. A composition requiring coating A-1 was obtained.

Next, the composition A-1 described above was applied to the surface of a 300 x 300 x 30 mm cast iron piece that had been degreased and cleaned using a solvent and had significant unevenness and pinholes to an average thickness of 500 microns, and was left at room temperature for 24 hours to form a primer. A coat layer was obtained.

Next, epoxy resin (epoxy equivalent: 900-1000,
A composition consisting of 70 parts (melting point: 96-104°C), 4 parts of dicyanthiamint, 25 parts of titanium oxide, and 1 part of a surface conditioner was uniformly mixed and dispersed using a plastic extruder at a temperature of 120°C, and then taken out and cooled. Powdered plastic composition B-1 having an average particle size that passes through 100 meshes after being crushed
I got it.

Next, the cast iron piece coated with the primer coat layer was coated with 20
After heating to 0°C, the composition B-1 was applied onto the primer coat layer to an average film thickness of 500 microns, and the adherend was held at 200°C for 20 minutes to heat melt the powdered plastic and form a plastic. A layer was formed, taken out, and quenched in water to obtain a test specimen of Example 1.

Visual observation of the surface of the plastic layer revealed that it was smooth and had a good finish, with no pinholes or cracks.

Example 2 A composition consisting of 50 parts of ordinary Portland cement, 50 parts of river sand with an average particle size of 100 microns, 18 parts of a water-soluble polyvinyl acetal resin aqueous solution (same as in Example 1), and 15 parts of tap water was thoroughly mixed and coated with a primer. Required composition A
-2 was obtained.

Next, the above-mentioned composition A-2 was applied to the surface of a cast iron piece having a shape of 300 x 300 x 30 mm, which had been degreased and cleaned using a solvent and had significant unevenness and pinholes, to an average thickness of 500 microns.
A primer coat layer was obtained by leaving it at room temperature for 4 hours.

Next, low density polyethylene (density 0.945, average molecular weight 40000, melt index 6, melting point 125°C)
A composition consisting of 80 parts of titanium oxide, 19 parts of titanium oxide, and 1 part of a surface conditioner was uniformly mixed and dispersed using a plastic extruder at a temperature of 180°C, taken out, cooled, and pulverized to obtain a powder having an average particle size that passes through 100 meshes. plastic composition B
-2 and carboxylated ethylene vinyl acetate copolymer (
Density 0.960, melt index 9) is crushed into 6
A powdered plastic composition B-3 having an average particle diameter of 0 mesh was obtained.

After heating the cast iron piece coated with the primer coat layer to 250°C, the composition B-3 was coated on the primer coat layer to an average thickness of 200 microns and melted, and then the composition B-2 was applied. was applied to an average film thickness of 300 microns, held at 200° C. for 15 minutes to form a plastic layer, and then taken out and quenched in water to obtain a test specimen of Example 2.

Visual observation of the surface of the plastic layer revealed that it was smooth and well-finished with no pinholes or cracks.

Example 3 60 parts of ordinary Portland cement, 40 parts of river sand with an average particle size of 100 microns, 15 parts of water-soluble polyvinyl acetal resin aqueous solution (same as in Example 1), 10 parts of water, and water-insoluble polyvinyl butyral resin (average degree of polymerization 250) ~5
Primer-coated footwear composition A-3 was obtained by thoroughly mixing 10 parts of a solution consisting of 10% butyralization degree (60% by mole) and 90% isopropyl alcohol.

Next, the above-mentioned composition A-3 was applied to the surface of a cast iron piece having a shape of 300 x 300 x 30 mm, which had been degreased and cleaned with a solvent and had significant unevenness and pinholes, to an average thickness of 500 microns.
A primer coat layer was obtained by leaving it at room temperature for 24 hours.

Next, thermoplastic acrylic resin (molecular weight 10,000 to 15
000. Softening point: 170°C) 90 parts, diphenyl chloride 10
18 parts of titanium oxide, 40 parts of titanium oxide, and 1 part of surface conditioner.
Powdered plastic composition B having an average particle size that passes through 100 meshes by uniformly mixing and dispersing using a plastic extruder at a temperature of 0 to 200°C, taking it out, cooling it, and pulverizing it.
-4 was obtained.

After heating the cast iron piece coated with the primer coat layer to 200°C, the composition B-4 was applied onto the primer coat layer to an average film thickness of 500 μm, and heated at 200°C.
The powdered plastic was held for 15 minutes to heat melt and form a plastic layer, which was then taken out and quenched by submersion in water to obtain a test specimen of Example 3.

Visual observation of the surface of the plastic layer revealed that it was smooth and well-finished with no pinholes or cracks.

Example 4 Water-soluble polyvinyl alcohol resin (saponification degree 88) was added to 50 parts of ordinary Portland cement and 50 parts of talc.
30 parts of a polyvinyl alcohol resin aqueous solution in which 20% (mol%, PVA content 94%) is mixed with 80% water;
10 parts of water and 0.1 part of a nonionic surfactant were thoroughly mixed to obtain a primer coated footwear composition A-4.

Next, the above composition A-4 was applied to an average thickness of 500 microns on the surface of a 300 x 300 x 30 mm cast iron piece that had been degreased and cleaned using a solvent and had significant unevenness and pinholes, and was left at room temperature for 24 hours to perform a primer coating. Got layers.

Next, thermoplastic polyester resin (number average molecular weight 150
00-20000, softening point 163°C), 50 parts titanium oxide, and 1 part surface conditioner.
The mixture was uniformly mixed and dispersed using a plastic extruder at 0.degree. C., taken out, cooled, and pulverized to obtain a powdery plastic composition B-5 having an average particle size that passed through 100 meshes.

After heating the cast iron piece coated with the primer coat layer to 200°C, the composition B-5 was applied onto the primer coat layer to an average film thickness of 500 μm.
The powdered plastic was held at 10° C. for 10 minutes to heat-melt it and form a plastic layer, which was then taken out and quenched by submersion in water to obtain a test specimen of Example 4.

Visual observation of the surface of the plastic layer revealed that it was smooth and well-finished with no pinholes or cracks.

Comparative Example 1 100 parts of ordinary Portland cement, 5 parts of water-soluble polyvinyl acetal resin aqueous solution (same as Example 1), 2 parts of water
The composition consisting of 5 parts was thoroughly mixed to obtain primer coated footwear composition A-5.

Next, the above-mentioned composition A-5 was applied to the surface of a cast iron piece having a shape of 300 x 300 x 30 mm, which had been degreased and cleaned with a solvent and had significant unevenness and pinholes, to an average thickness of 500 microns.
A primer coat layer was obtained by leaving it at room temperature for 24 hours.

Composition B- of Example 3 was then applied onto the primer coat layer.
A test specimen of Comparative Example 1 was obtained by processing in the same manner as in Example 3 using Comparative Example 4.

When the surface of the plastic layer was observed with the naked eye, there were many microscopic cracks thought to be caused by cracks in the primer coat layer and five pinholes with a diameter of about 0.5 mm, making it unusable for practical use. there were.

Comparative Example 2 A composition of 80 parts of ordinary Portland cement, 20 parts of river sand with an average particle size of 100 microns, and 60 parts of a water-soluble polyvinyl acetal resin aqueous solution (same as in Example 1) was thoroughly mixed to form a primer-coated footwear composition A-. I got 6.

Next, the above composition A-6 was applied to an average thickness of 500 microns on the surface of a cast iron piece having a shape of 300 x 300 x 30 mm, which had been degreased and cleaned using a solvent, and had significant unevenness and pinholes.
A primer coat layer was obtained by leaving it at room temperature for 4 hours.

Composition B- of Example 4 was then applied onto the primer coat layer.
A test specimen of Comparative Example 2 was obtained by processing in the same manner as in Example 4 using Comparative Example 5.

As a result of observing the surface of the plastic layer with the naked eye, the diameter was 0.
Numerous blisters of 5 to 2 mm were generated, and the product was in a state where it could not be put to practical use.

Comparative Example 3 A cast iron piece that was the same as Example 1 but without a primer coat layer was
After heating to 00°C and applying the same composition B-1 as in Example 1 to an average film thickness of 500 microns, the adherend was coated with 2.
The powdered plastic was heated at 00° C. for 30 minutes to melt and form a plastic layer, which was then taken out and quenched in water to obtain a test specimen of Comparative Example 3.

When the surface of the plastic layer was observed with the naked eye, the diameter was 0.5.
There were countless pinholes of ~1 mm, and the surface lacked smoothness.

Thus, as is clear from the results of Examples 1 to 4 and Comparative Examples 1 to 3, the plastic coating obtained by the method of the present invention has a plastic layer with a beautiful surface without pinholes or unevenness. Met.

Claims (1)

[Scope of Claims] 1 (1) On the surface of the casting, (a) 100 parts by weight of a mixture consisting of 100 to 30% by weight of cement and 0 to 70% by weight of aggregate;
(b) applying a composition consisting of 2 to 15 parts by weight of polyvinyl acetal resin and/or polyvinyl alcohol resin and (c) an appropriate amount of water and solidifying it to obtain a primer coat layer; (2) the primer coat; A surface processing method for castings that consists of the following steps: applying powdered plastic to the layer surface and heat-melting it to obtain a plastic layer.