JPS5853949B2 - Manufacturing method for plastic coated castings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing pinhole-free plastic coated castings.

Conventionally, various metal castings have been given an aesthetic finish through a considerable number of painting processes.

Compared to regular steel materials, cast products have many irregularities, pores, pinholes, etc. on the casting surface, so if you want to give it a beautiful finish, you need to use puffing, puttying, primer painting, surfacer painting, topcoating, etc. This process requires at least three or four painting processes to achieve a beautiful finish.

For example, to explain the conventional aesthetic finishing method for cast products, for cast products that have been puffed or those that are not very uneven, a degreasing process is performed without puffing, and after removing oil, dirt, etc., a wash primer or chemical treatment is applied. After applying a coating, cracks, holes, pinholes, etc. were filled in using a putty process.

Since the putty is required to have good filling properties and good polishing properties, the resulting coating is relatively porous and has low strength.

The puttying process is often carried out partially, so after the SAFACER application process, the resulting SAFACER coating film is wet-sanded to compensate for some irregularities on the polished surface and at the same time to prevent suction of the top coat. If necessary, perform Safer Painting and Wet Sanding again.

The usual process is to then apply an intermediate coat and a top coat to complete the process, which requires a large number of steps as described above.

This is because conventional solvent-based paints not only cannot be applied thickly in one coat, but even when applied thickly, coating defects such as sagging and pinholes are likely to occur on the painted surface, so the coating must be applied in several coats. This was because it was necessary.

The above process is possible when the shape of the casting is not very large, but the larger the casting becomes, such as a cast iron pipe or a cast iron pile, the more impractical the process becomes.

As a method to omit these many work steps, a method has been adopted in which a plastic layer is obtained by applying powdered plastic that can be applied thickly in one step and melting it with heat, but this method is insufficient in terms of finished appearance. Ta.

That is, as mentioned above, the surface of the cast product has many pores and pinholes, and it is impossible to eliminate them due to the manufacturing process of the cast product.

If powdered plastic is directly applied to a metal surface with such a surface condition and heated and melted, the plastic will not penetrate sufficiently into the pores and pinholes due to its high viscosity when melted, resulting in the formation of pores and pinholes. Air remaining in the pores foams during film formation, creating pinholes that penetrate through the plastic layer, significantly reducing the finished appearance and corrosion resistance of the film.

The present invention aims to improve such defects in cast products coated with plastic and to provide a method for manufacturing plastic coated cast products with excellent finished appearance.

That is, the present invention comprises (a) a step of applying a resin liquid consisting of 90 to 70% by weight of a thermosetting resin and 10 to 30% by weight of a thermoplastic resin to the surface of a cast product to obtain a primer coat layer, and ( (b) A method for manufacturing a plastic-coated cast product comprising the steps of: applying powdered plastic to the surface of the primer coat layer and then heat-melting the plastic to obtain a plastic layer.

In the present invention, the thermosetting resin used in the primer coat layer is one or two types containing in the molecule groups necessary to react with each other and form a crosslinked structure by heating or accelerated heating. For example, combinations of groups that react with each other include carboxyl groups (including acid anhydride groups) to epoxy groups, carboxyl groups (
(including acid anhydride groups) to hydroxyl groups, hydroxyl groups to epoxy groups, hydroxyl groups to hydroxyl groups, hydroxyl groups to isocyanate groups (including blocked isocyanate groups), epoxy groups to amino groups, hydroxyl groups to methylol groups, hydroxyl groups to etherified methylol groups, etc. Can be mentioned.

Specific examples of these include melamine-alkyd resin, acrylic-alkyd resin, acrylic-melamine resin, self-curing acrylic resin, epoxy-phenol resin, epoxy-polyamide resin, polynisteryl isocyanate resin, epoxy-acid anhydride. etc. are listed as typical combinations.

Examples of thermoplastic resins used in the primer coat layer in the present invention include polyvinyl alcohol, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer, vinylidene chloride resin, cellulose acetate, polyvinyl chloride, polyacrylate, polymethacrylate, and acrylic resin. −
Tormethacrylate copolymer, saturated polyester, polyethylene, polypropylene, nylon, atactic polypropylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, vinyl acetate resin,
Styrene-isoprene block copolymer, styrene-butadiene copolymer, polyamide resin, rosin, rosin glycerin ester, hydrogenated rosin glycerin ester,
History of petroleum resins, coumaron resins, terpene resins, styrene-olefin copolymers, styrene copolymers, hydrogenated hydrocarbon resins, aliphatic hydrocarbon resins, and their derivatives, as well as various solid plasticizers, pitch asphalt, etc. A typical example is blue.

Among these, the molecular weight is 2000 or less, the softening point is 13, and it has a molecular weight of 2000 or less and a softening point of 13.
Thermoplastic resins having a temperature of 0° C. or lower are most preferred.

The resin liquid of the present invention is made by dissolving one or more of the above thermosetting resins and thermoplastic resins in a solvent such as an organic solvent or water.

A feature of the present invention is that the thermosetting resin and thermoplastic resin are mixed in a specific ratio.

Conventionally, a method has been commonly used in which a thermosetting resin paint is applied as a primer coat layer in a pre-process of applying a powdered plastic onto an ordinary metal surface and thermally melting it to obtain a plastic layer.

When this type of paint is applied as a primer coat layer to the surface of a cast article as in the present invention, it penetrates into the pores and pinholes, and is somewhat effective in preventing pinholes after the plastic layer is formed.

However, during the setting process of the primer coat layer, the viscosity of the primer coat layer increases with the scattering of the solvent and loses fluidity, making it impossible to completely fill pinholes and pores.

Forming a plastic layer in an incompletely filled state may cause pinholes to occur.

The present invention solves these drawbacks and uses a resin liquid that combines a thermosetting resin and a thermoplastic resin as a primer coat layer, thereby making it possible to fill holes and pinholes on the surface of a cast product that cannot be sufficiently filled by coating the resin liquid alone. This will completely fill the tank.

In other words, the heat of the process of thermosetting the primer coat layer or the process of forming the plastic layer causes the thermoplastic resin in the primer coat layer to flow, completely filling the pores and pinholes, and the heat generated in the process of forming the plastic layer. Thermosetting resins are extremely effective in preventing the formation of pinholes in plastic layers by forming a strong film.

In the present invention, the mixing ratio of the thermosetting resin and the thermoplastic resin is 10 to 30% by weight of the thermoplastic resin to 90 to 70% by weight of the thermosetting resin.

If the amount of the thermoplastic resin is less than the range of the present invention, there will be no pore-filling effect at all during heating (on the contrary, if the amount is more than the range of the present invention, the coating workability will be difficult if the molecular weight of the thermoplastic resin is large). If the molecular weight is small, the fluidity of the resin liquid is low, and it is not effective in filling pores and pinholes immediately after application.On the other hand, if the molecular weight is small, the degree of thermoplasticity is too large when heated, causing the plastic layer to shift. This is not preferable because it causes poor adhesion with the plastic layer.

The powdered plastic of the present invention may be any thermosetting resin or thermoplastic resin that requires a primer coating, as long as it is in a solid state at room temperature and can be processed into powder form by a chemical or physical method. is also available.

The resin liquid and powdered plastic required for primer coating of the present invention have the above-mentioned contents as basic components, but of course coloring pigments such as iron oxide, titanium oxide, carbon black, synchromate, red lead, strontium chromate,
Rust-preventing pigments such as talc, precipitated barium sulfate, extender pigments such as calcium carbonate, surface conditioners, anti-blocking agents, plasticizers, stabilizers, suspending agents, anti-sagging agents, etc. Commonly known paints and powder coating compositions There is no problem in mixing and using raw materials used in products.

In particular, from the viewpoint of increasing the thickness of the primer coat layer and coloring the plastic layer, it is preferable to use it in combination with extender pigments, antirust pigments, coloring pigments, and the like.

The method for obtaining the plastic coated casting of the present invention is as follows:
Rust, oil, and other adhesion-resistant materials are removed by degreasing, blasting, etc., and the resin solution required for primer coating of the present invention is applied to the surface of the cast product, which has been cleaned in advance, using a brush, roller, spray, flow coater, centrifugal coating, or other known method. A primer coat layer is obtained by applying the primer to a desired thickness, preferably about 30 to 60 microns.

After the primer coat layer is left under the necessary setting conditions, the primer coat layer is completely fixed by heating at the temperature and time necessary for heat curing, and then powdered plastic is applied to the surface of the primer coat layer by a conventional method. Apply the primer coat and maintain the conditions necessary to form a plastic layer, or preheat the object coated with the primer coat layer set above to 120 to 200°C, and apply powder on the primer coat layer. After applying the plastic and raising the temperature to the temperature required to form the plastic layer, solidifying the primer coat layer and forming the plastic layer at the same time, the primer coat layer to the plastic layer are cooled naturally or rapidly. It is possible to obtain a beautiful plastic-coated casting product with no pinholes.

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 Epoxy resin (epoxy equivalent: 1,750-2,100; melting point: 120-131°C) 3 as a silk combination of thermosetting resin
2 parts, phenolic resin solution [manufactured by Hitachi Chemical ■ Part name;
Hytanol 4020: 9 parts of xylene/n-butanol mixed solution with solid content 50%, cyclopentadiene synthetic resin as thermoplastic resin (softening point 100°C; saponification value 15
5-175) 11 parts, talc 10 parts, xylene 12 parts,
A composition consisting of 13 parts of methyl isobutyl ketone and 13 parts of isobutyl alcohol was thoroughly mixed and stirred using a mixer, and then passed through a roll mill to obtain a primer coat resin liquid composition A-1.

Next, the composition A-1 was applied to the surface of a 300 x 300 x 30 mm shaped cast piece that had been degreased and cleaned using a mixed solvent of butyl cellosolve and isobutyl alcohol to have a viscosity of 35 seconds (viscosity measured by Ford Cup #4). It was coated to a dry film thickness of 50 microns and set at room temperature for 60 minutes to obtain a primer coat layer.

Next, epoxy resin (epoxy equivalent: 900 to 1.00
A composition consisting of 70 parts of 0; melting point 96-104°C), 4 parts of dicyandiamide, 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 having an average particle size that passes through 100 meshes after being crushed
-1 was obtained.

The cast iron piece coated with the primer coat layer was preheated to 130°C, and the composition B-1 was applied onto the primer coat layer to an average film thickness of 500 microns.
The powdered plastic was held at 0° C. for 30 minutes to heat melt and obtain a plastic layer.

After taking out and cooling, the surface of the plastic layer was observed with the naked eye, and as a result, there were no pinholes per 300 x 300 mm.

Example 2 As a combination of thermosetting resins, 25 parts of epoxy resin (epoxy equivalent: 184 to 194), 7 parts of 4-methylhexahydrophthalic anhydride, and as a thermoplastic resin, carboxylated ethylene vinyl acetate copolymer (density 0.96) A composition consisting of 7 parts of melt index 9) and 61 parts of toluene was uniformly mixed and dissolved using a high-speed mixer to obtain primer coat resin liquid composition A-2.

Next, the composition A-2 was applied to the surface of a 300 x 300 x 30 mm cast iron piece that had been degreased and cleaned using xylene to a viscosity of 2.
The coating time was adjusted to 5 seconds (viscosity measured by Ford cup #4) and coated to give an average dry film thickness of 35 microns, and set at room temperature for 60 minutes to obtain a primer coat layer.

Next, low density polyethylene (density 0.945; average molecular weight 40,000; melt index 6; melting point 125
℃) A composition consisting of 19 parts of SO, 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 ℃, taken out, cooled, and pulverized to 100%
A powdered plastic composition B-2 having an average particle size that passed through the mesh was obtained.

Next, the cast iron piece coated with the primer coat layer was coated with
After heating to 00°C, the composition B-2 is applied onto the primer coat layer to an average thickness of 500 microns, and the adherend is held at 200°C for 10 minutes to heat melt the powdered plastic and form a plastic layer. I got it.

After taking it out and cooling it, the surface of the plastic layer was observed with the naked eye. As a result, there were no pinholes per 300 x 300 m4.

Example 3 Self-curing acrylic resin liquid as thermosetting resin [Product name manufactured by Mitsubishi Rayon ■; Duracron 5E5661: solid content 5
0% Tsurupetz #100/xylene/n-butanol, = 50/25/25 mixed solution) 40 parts, acrylic resin liquid as thermoplastic resin [Mitsubishi Rayon Part name: Dianal LR-510: Solid content 30% Tsurupets #1
00 solution, 115 parts, talc 15 parts, Tsurpets #10
010 parts, xylene 10 parts, isobutyl alcohol 10 parts
After thoroughly mixing and stirring the composition, the mixture was passed through a roll mill to obtain a primer coat resin liquid composition A-3.

Next, after solvent degreasing and cleaning, 300X300X30m
The composition A-3 was applied to the surface of an m-shaped cast iron piece.
A mixed solvent of 0 parts and 10 parts of butyl cellosolve has a viscosity of 40.
After applying the film to an average dry film thickness of 40 microns (viscosity measured by Ford Cup #4),
After setting for a minute, a primer coat layer was obtained.

Next, thermoplastic acrylic resin (molecular weight 10.000-15,000; melting point 170'C) 90
10 parts of diphenyl chloride, 40 parts of titanium oxide, and 1 part of a surface conditioner are uniformly mixed and dispersed using a plastic extruder at a temperature of 180 to 200°C, taken out, cooled, and pulverized to form 100 mesh pieces. A powdered plastic composition B-3 having an average particle size of 100% was obtained.

Next, the cast iron piece coated with the primer coat layer was coated with
After heating to 00'C and coating the composition B-3 on the primer coat layer to an average thickness of 500 microns, the adherend was held at 200C for 15 minutes to heat melt the powdered plastic. A plastic layer was obtained.

After taking out and cooling, the surface of the plastic layer was observed with the naked eye, and as a result, there were no pinholes per 300 x 300 m4.

Example 4 As a combination of thermosetting resins, acrylic resin liquid [trade name manufactured by Hitachi Chemical Co., Ltd.; Hitaloid 2405: solid content 50%
xylene/n-butanol mixed solution] 30 parts, melamine resin liquid [Hitachi Chemical Part name; Melan 22: xylene/n-butanol mixed solution with solid content of 60%] 10 parts, aliphatic resin as thermoplastic resin Hydrocarbon resin (softening point 9
After thoroughly mixing and dissolving a composition consisting of 8 parts (3°C), 10 parts talc, 6 parts isobutyl alcohol, 16 parts methyl isobutyl ketone, and 20 parts xylene using a mixer, the mixture was passed through a roll mill to form Primer Coat Resin Liquid Composition A. -4 was obtained.

Next, on the surface of a 300 x 300 x 30 mm cast iron piece that had been degreased and cleaned with a solvent, the composition A-4 was adjusted to a viscosity of 30 seconds with isobutyl alcohol and applied to an average dry film thickness of 50 microns, and allowed to set at room temperature for 60 minutes. A primer coat layer was obtained.

Next, thermoplastic polyester resin (number average molecular weight 15
,000-20,000; softening point: 1636C), 50 parts of titanium oxide, and 1 part of a surface conditioner.
The mixture was uniformly mixed and dispersed using a plastic extruder at ~200° C., taken out, cooled, and pulverized to obtain a powdered plastic composition B-4 having an average particle size passing through 100 meshes.

Next, the cast iron piece coated with the primer coat layer is
After heating to 00°C, the composition B-4 was applied onto the primer coat layer to an average thickness of 500 microns, and the adherend was held at 200°C for 10 minutes to heat melt the powdered plastic. A plastic layer was obtained.

After taking out and cooling, the surface of the plastic layer was observed with the naked eye, and as a result, there were no pinholes per 300 x 300 m4.

Example 5 As a combination of thermosetting resins, 30 parts of epoxy resin (same as in Example 1) and phenol resin solution (same as in Example 1) were used.
) 16 parts (same as above), 46 parts of cyclopentadiene synthetic resin as thermoplastic resin (same as in Example 1), 1 talc
A composition consisting of 0 parts, xylene 12 parts, methyl isobutyl ketone 13 parts, and isobutyl alcohol 13 parts was thoroughly mixed and stirred using a mixer, and then passed through a roll mill to obtain a resin liquid composition A-5 requiring primer coating.

Next, the composition A was adjusted to a viscosity of 35 seconds (viscosity measured by Ford Cup #4) with a mixed solvent consisting of a mixture of butyl cellosolve and isobutyl alcohol on the surface of a 300 x 300 x 30 cast iron piece that had been degreased and cleaned using a solvent. Apply to a dry film thickness of 50 microns and apply at room temperature.
After setting for 0 minutes, a primer coat layer was obtained.

The cast iron piece coated with the primer coat layer was preheated to 130°C, and the composition B-1 obtained in Example 1 was coated on the primer coat layer to an average film thickness of 500 microns. The powdered plastic was heated and held at 200° C. for 30 minutes to obtain a plastic layer.

After taking out and cooling, the surface of the plastic layer was observed with the naked eye, and as a result, there were no pinholes per 300×300r7.

Comparative Example 1 Epoxy resin as thermosetting resin (same as Example 1) 4
0 parts, 13 parts of phenolic resin solution (same as Example 1),
A composition consisting of 10 parts of talc, 12 parts of xylene, 13 parts of methyl isobutyl ketone, and 13 parts of inbutyl alcohol was thoroughly mixed and dissolved using a mixer, and then passed through a roll mill to obtain a resin liquid composition A-5 requiring primer coating. Ta.

Next, the composition A-5 was applied to the surface of a 300x300x30 cast iron piece that had been degreased and cleaned using the same procedure as in Example 1 to obtain a primer coat layer.

Next, powdered plastic composition B-1 having the same composition as in Example 1 was applied onto the primer coat layer in the same manner as in Example 1 to obtain a plastic layer.

After taking it out and cooling it, the surface of the plastic layer was observed with the naked eye, and the diameter was about 0.5 to 1 m per 300 x 300 mm.
There were 13 rn dog pinholes.

Comparative Example 2 Epoxy resin as thermosetting resin (same as Example 2) 6
0 parts, 4-methylhexahydrophthalic anhydride (Example 2
(same as above) and 20 parts of toluene were uniformly mixed using a mixer to obtain a primer coated footwear composition A-5.

Next, the composition A-5 was applied to the surface of a 300 x 300 x 30 mm cast iron piece that had been degreased and cleaned using the same procedure as in Example 2 to obtain a primer coat layer.

Next, powdered plastic composition B-2 having the same composition as in Example 2 was applied onto the primer coat layer in the same manner as in Example 2 to obtain a plastic layer.

After taking it out and cooling it, the surface of the plastic layer was observed with the naked eye, and the diameter was about 0.5 to 1 mm per 300 x 300 m4.
There were eight dog pinholes.

Comparative Example 3 A cast iron piece in the shape of 300 x 300 x 307nrIL that had been degreased and cleaned using a solvent was heated to 200'C, and then powdered plastic composition B4 having the same composition as in Example 4 was applied to the surface to give an average dry film thickness of 500 microns. , the powdered plastic was heated and held at 200° C. for 10 minutes to obtain a plastic layer.

After taking it out and cooling it, the surface of the plastic layer was observed with the naked eye, and it was found that the diameter was about 0.5 to 17 mm per 300 x 300 m4.
There were 38 pinholes with a size of nπ.

Comparative Example 4 In Example 1, 30.2 parts of epoxy resin, 8.6 parts of phenol resin solution as the thermosetting resin combination, and 2.5 parts of cyclopentadiene synthetic resin as the thermoplastic resin were used. Curable resin/thermoplastic resin-93
, 2/6.8: solid content weight ratio) A test piece was obtained in the same manner as above.

As a result of visually observing the surface of the plastic layer after cooling, it was found that 30
0x3001n7? Per L, diameter 0.5-17rL11
There were four L pinholes.

Comparative Example 5 In Example 1, 27.6 parts of epoxy resin, 7.8 parts of phenol resin solution were used as the thermosetting resin combination, and 15.5 parts of cyclopentadiene synthetic resin was used as the thermoplastic resin. Curable resin/thermoplastic resin-6
7/33: solid content weight ratio) A test piece was obtained in the same manner as above.

After cooling, the plastic surface was visually observed, and no pinholes were observed, but the adhesion of the plastic layer to the primer coat layer was extremely poor.

Comparative Example 6 In Example 2, the thermosetting resin combination was 28.4 parts of epoxy resin, 7.9 parts of 4-methylhexahydrophthalic anhydride, and the thermoplastic resin was carboxylated ethylene vinyl acetate copolymer 2. A test piece was obtained in the same manner except that 7 parts (thermosetting resin/thermoplastic resin 93.1/6.9: solid weight ratio).

As a result of visually observing the surface of the plastic layer after cooling, it was found that 30
0x300m1? There were 7 dog pinholes with diameters of 0.5 to 11 nm.

Comparative Example 7 In Example 2, the thermosetting resin combination was 20.4 parts of epoxy resin, 5.7 parts of 4-methylhexahydrophthalic anhydride, and the thermoplastic resin was carboxylated ethylene-vinyl acetate copolymer 12. .9 parts were used (
Thermosetting resin/thermoplastic resin-67/33: solid content weight ratio) A test piece was obtained in the same manner as above.

As a result of visually observing the surface of the plastic layer after cooling, it was found that 30
There were 11 dog pinholes with a diameter of 0.5 to 1 r/Lm per 0x300 m4.

Table 1 shows the number of pinholes on the surface of the plastic layer and the results of the adhesion test of the plastic layer in the test pieces obtained in Examples 1 to 5 and Comparative Examples 1 to 7.

It is clear from the comparative test results table that the plastic-coated castings obtained by the method of the present invention had excellent plastic adhesion and a beautiful finished appearance with no pinholes.

On the other hand, when a relatively low molecular weight thermoplastic resin is used in a smaller amount than the range of the present invention (Comparative Example 4), the effect of filling the pores decreases and pinholes occur, and the adhesiveness of the plastic layer also decreases. On the contrary, when the amount is larger than the range of the present invention (Comparative Example 5), the filling effect is improved, but the adhesiveness is significantly deteriorated.

Furthermore, when a relatively high molecular weight thermoplastic resin is used in an amount less than the range of the present invention (Comparative Example 6), the number of pinholes increases and adhesiveness decreases, and conversely, when the amount is greater than the range of the present invention (Comparative Example 7).
) Adhesion is improved, but the filling effect is reduced and the number of pinholes increases.

Furthermore, in both cases where no thermoplastic resin is used (Comparative Examples 1 and 2) and where no primer coat layer is provided (Comparative Example 3), the number of pinholes is large and the adhesiveness is low.

Claims (1)

[Scope of Claims] 1 (a) A step of applying a resin liquid consisting of 90 to 70% by weight of a thermosetting resin and 10 to 30% by weight of a thermoplastic resin to the surface of the cast product to obtain a primer coat layer, and ( (b) A method for producing a plastic-coated cast product, comprising the steps of: applying a powdered plastic to the surface of the primer coat layer and then heat-melting the plastic to obtain a plastic layer.