JPS585110B2 - 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, puffing process, putty process, primer coating, surfacer coating, and top coating are necessary. It requires various processes such as painting, and therefore, a beautiful finish is achieved through at least three or four painting processes.

To further explain the conventional aesthetic finishing method for castings using a specific example, for castings that have been puffed or for castings that are not very uneven, a degreasing process is first performed without puffing 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, after performing SAFACER-painting-water-sanding 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 paint film gaps such as pinholes are likely to occur, it was necessary to apply the coating in several parts.

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; (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) 2 to 15 parts by weight of a resin composition comprising a polyvinyl acetal resin and/or a polyvinyl alcohol resin and a resin having a group that reacts with the hydroxyl group of the resin when heated, and (c) an appropriate amount of water. After applying the composition, the cement is solidified and then heated to obtain a primer coat layer, and (b) powdered plastic is applied to the surface of the obtained primer coat layer and heated to melt to form a plastic layer. The present invention relates to a method for surface treatment of castings, which comprises the following steps:

The "cement" used in the primer coat footwear 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 coat layer composition of the present invention includes sand, gravel, crushed stone, crushed 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.

If the amount of cement in 5 above is less than 30% by weight,
The primer coat layer lacks toughness and is not preferred as a primer coat layer for a plastic layer.

The "polyvinyl acetal 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, and the like.

More specifically, commercially available water-soluble polyvinyl acetal resins include Eslec W and Eslec W2O1.
[The above-mentioned Building Blocks Chemical Industry product name] etc., and the water-insoluble polyvinyl acetal resin has an average degree of polymerization of 2509 to 2,000, preferably from the viewpoint of water resistance, adhesion to metal surfaces, mixability of the composition, etc. is 250-1000
, butyralization degree 57-75 mol%, preferably 57-7
0 mol% 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 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 afcetal resin organic solvent solution.

The mixing ratio is water-soluble polyvinyl acecool resin 99~
1 to 60% by weight of non-water soluble polyvinyl acecool resin, preferably 90 to 70% by weight of water-soluble resin relative to 40% by weight
The water-insoluble resin is 10 to 30% by weight based on the weight% i.

The "polyvinyl alcohol resin" used in the primer coated footwear composition of the present invention has a degree of saponification of 86 mol% or more, is soluble in cold water or hot water, and has a working viscosity of ν. Average molecular weight from point 1,5
It is better if it is less than 00.

For example, Solsiden DF-107, DF-108, DF-
605N, DF-402, Denka Poval ni-20, ni-17, ni-05, B-17R, W-24, 13-24
, B-20, B-05, B-03, [Denki Kagaku Kogyo ■Cracked product name] Kuraray Bobal PVA-105, PVA1
O7゜PVA-110, PVA-204, PVA-21
5゜PVA-210, PVA-217, [Kuraray product names above], Hi-Selon H, Hi-Selon S, Gohsenol NH-20, NH-18, GH-17゜GH-05,
Commercially available resins such as [above Nippon Gosei Kagaku Kogyo ■ cleavage product name] 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, the groups that react with each other with the hydroxyl groups contained in the polyvinyl acetal resin and/or polyvinyl alcohol resin when heated include carboxyl groups (including acid anhydride groups), epoxy groups, hydroxyl groups, blocked isocyanate groups, Examples include a methylol group and an etherified methylol group.

Specific examples of resins having such groups include phenol resins, urea resins, melamine resins, blocked polyisocyanates, and epoxy resins.

The mixing ratio of the reactive resin (hereinafter referred to as reactive resin) and the polyvinyl acetal resin and/or polyvinyl alcohol resin is 1 to 50% by weight, preferably 10 to 30% by weight for the former, and 50 to 30% by weight for the latter. The proportion is 99% by weight, preferably 70-90% by weight.

If the mixing ratio of the reactive resin is less than 1% by weight, sufficient crosslinking during heating will not be achieved and the performance of the primer coat layer will not be fully demonstrated.On the other hand, if it exceeds 50% by weight, the polyvinyl acetal resin and/or Otherwise, the inherent flexibility of the polyvinyl alcohol resin is lost, and the primer coat layer may crack or become brittle, which is undesirable, especially when the plastic coating is used in cold regions or under environmental conditions that repeatedly heat and cool.

In the present invention, the polyvinyl acecool resin and/or
Or a resin composition consisting of a polyvinyl alcohol resin and a reactive resin can be used as a cement or cement aggregate mixture.
It is mixed at a ratio of 2 to 15 parts by weight, preferably 4 to 8 parts by weight.

If the mixing ratio of the resin composition 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, the coated casting may be placed in a cold region, or the coating may be heated repeatedly. If it is left under environmental conditions, the primer coat layer will crack and become brittle, which is not preferable.

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 tends to become too dense, resulting in blistering during the process of thermally melting the powdered plastic.

As in the present invention, by using a composition in which cement or a mixture of cement and aggregate and the above amount of resin is used in the primer coat layer, unevenness and pinholes peculiar to castings can be eliminated.
In addition to giving the effect of completely filling the burrows, the resin in the primer coat layer makes the layer fine and becomes fluid during setting or when heated when melting the powdered plastic and floats to the surface of the primer coat layer. Therefore, in order to form a primer coat layer with fewer pinholes,
After forming the plastic layer, a smooth, pinhole-free plastic-coated casting is obtained.

Further, due to the flexibility imparting effect of the resin, the primer coat layer does not cause cracks or peeling 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, coagulation accelerators such as sodium silicate and aluminum chloride, and surfactants such as nonionic or anionic surfactants that have been conventionally used in concrete compositions. 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, there is used a thermosetting or thermoplastic resin that is solid at room temperature and can be processed into powder by chemical or physical methods.

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. For example, combinations of mutually reactive groups 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 Typical combinations include resins and acid anhydrides.

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 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, Various materials commonly used in paint 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., can be mixed and used. good.

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, for example, about 100 to 1.000 microns, by a known method such as brush, roller, spray, spatula, or rotary coating, and the conditions necessary for the cement to solidify are met, such as The cement is left to harden by natural steam curing, etc.

Next, the resin composition in the primer coat layer is heated to a temperature necessary for curing to obtain a primer coat layer.

The heating is usually performed at a temperature of 120° C. or higher for 10 minutes or more.

Furthermore, if necessary, powdered plastic is applied to the surface of the primer coat layer, which has been preheated to about 120 to 300°C, and after maintaining the temperature condition necessary to form a plastic layer, natural cooling or rapid cooling, etc. A plastic covering of the casting is obtained.

In the above method, when the primer coat layer is preheated before application of the powdered plastic, the preheating can be used for thermosetting the resin composition in the primer coat layer.

In that case, the temperature may be maintained at a temperature higher than either the thermosetting temperature or the preheating temperature, whichever is higher.

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, "parts" or "%" in Examples and Comparative Examples are "parts by weight"
Or "% by weight".

Example 1 100 parts of ordinary Portland cement, 20 parts of water-soluble polyvinyl acetal resin aqueous solution [Kikusui Kagaku Kogyo Co., Ltd., product name; Esletsuk W: non-volatile content 25%], 20 parts of phenolic resin liquid [Dainippon Ink and Chemical Co., Ltd. product name: NIBRAIO] -Phen P-398: 40% non-volatile content aqueous solution] 3 parts, tap water 2
A composition A-1 requiring primer coating was obtained by thoroughly mixing the composition consisting of 5 parts.

Next, the above composition A-1 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 irregularities, pinholes, etc., to an average thickness of 500 microns, and was left at room temperature for 24 hours. The cement in the primer coat layer was solidified.

Next, epoxy resin (epoxy equivalent: 900 to 1.000
, melting point 96-104°C), 4 parts of dicyandiamide, 25 parts of titanium oxide, and 1 part of a surface conditioner were uniformly mixed and dispersed using a plastic extruder at a temperature of 120°C, taken out, cooled, and pulverized. Powdered plastic composition 13- having an average particle size passing through 100 meshes
After heating the cast iron piece coated with the primer coat layer 1 to 200°C, the composition B-1 was coated on the primer coat layer to an average film thickness of 500 microns, and the adherend was coated with the composition B-1. The powdered plastic was held at 200° C. for 20 minutes to thermally melt and form a plastic layer, which was then 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 well-finished, with no pinholes or cracks.

Example 2 50 parts of ordinary Portland cement, 50 parts of river sand with an average particle size of 100 microns, 20 parts of a water-soluble polyvinyl acetal resin aqueous solution (same as in Example 1), melamine resin [manufactured by Mitsui Toatsu Chemicals, trade name: Newpan 20] 60% non-volatile content,
Kijirol, n-butanol mixed solvent] 3 parts, tap water 1
The composition consisting of 5 parts was thoroughly mixed to obtain Primer Cord Layer Composition A-2.

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.
The cement in the primer coat layer was left to stand at room temperature for 4 hours to solidify.

Next, low density polyethylene (density 0.945, average molecular weight 40,000, melt index 6, melting point 125°C
), 19 parts of titanium oxide, and 1 part of a surface conditioner were uniformly mixed and dispersed using a plastic extruder at a temperature of 180°C, taken out, cooled, and pulverized to obtain an average particle diameter of 100 meshes. Powdered plastic composition B-2 and carboxylated ethylene vinyl acetate copolymer (density 0.960, melt index 9) were pulverized to obtain powdered plastic composition B-3 having an average particle size that passed through 60 meshes. 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 a water-soluble polyvinyl acetal resin aqueous solution (same as in Example 1), urea resin solution [manufactured by Dainippon Ink & Chemicals, trade name: Betsukamine] P-138:
Non-volatile content 60%, Kijirol, butanol mixed solution] 1
10 parts of water and 5 parts of a solution consisting of 10 parts of water-insoluble polyvinyl butyral resin (average degree of polymerization 25.5 to 500, degree of butyralization 60 mol%) and 90 parts of isopropyl alcohol were thoroughly mixed to form a primer code. A layer composition A-3 was obtained.

Next, the above-mentioned composition A-3 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 perform a primer coating. The cement in the layer was allowed to solidify.

Next, a thermoplastic acrylic resin (molecular weight 10,000 to 1
5,000 softening point 170°C) 90 parts, diphenyl chloride 1
0 parts of titanium oxide, 40 parts of titanium oxide, and 1 part of surface conditioner.
The mixture was uniformly mixed and dispersed using a plastic extruder at a temperature of 80 to 200° C., taken out, cooled, and pulverized to obtain a powdery plastic composition B-4 having an average particle size passing through 100 meshes.

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 microns.
The powdered plastic was held at ℃ 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 prepared by mixing 20 parts (mol%, PVA content 94%) with 80 parts of water;
Melamine resin solution (manufactured by Dainippon Ink & Chemicals) Product name:
Watersol S-695: 66% non-volatile content aqueous solution]
1 part of water, 10 parts of water, and 0.01 part of nonionic surfactant were thoroughly mixed to obtain Primer Coat Layer Composition 1-4.

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 dragon-shaped cast iron piece that had been degreased and cleaned using a solvent and had significant unevenness and pinholes.
The cement in the primer coat layer was left to stand at room temperature for 4 hours to solidify.

Next, thermoplastic polyester resin (number average molecular weight 15,
000-20,000, softening point 163°C), 50 parts of titanium oxide, and 1 part of surface conditioner.
The mixture was uniformly mixed and dispersed using a plastic extruder at 00° 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 acecool resin aqueous solution (same as Example 1), 2 parts of water
The composition consisting of 5 parts was thoroughly mixed to obtain a composition requiring primer coating 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.

There were many fine cracks thought to be caused by cracks in the primer coat layer and five pinholes with a diameter of about 0.5 mm, and the product could not be put to practical use.

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 composition requiring primer coating 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 The same cast iron piece as in Example 1 without the 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) 2 to 15 parts by weight of a resin composition comprising a polyvinyl acetal resin and/or a polyvinyl alcohol resin and a resin having a group that reacts with the hydroxyl group of the resin when heated; and (c) an appropriate amount of the resin composition. After applying a composition consisting of water, cement is solidified and then heated to obtain a primer coat layer, and (2) a powdered plastic is applied to the surface of the primer coat layer and the plastic is melted by heat. A casting surface processing method consisting of the following steps: obtaining a layer;