TWI696690B - Lost foam coating composition - Google Patents

Abstract

A lost foam coating composition is provided, including a refractory aggregate and an organic high molecular polymer, wherein a content of the organic high molecular polymer is from 5 parts by weight to 10 parts by weight relative to 100 parts by weight of the refractory aggregate.

Description

Lost foam coating composition

The present invention relates to a lost foam coating composition, and in particular to a lost foam coating composition which has high safety, fast drying, high strength and can further suppress residue defects.

The lost foam casting method is a casting method that uses a synthetic resin foam model (generally called Styrofoam) of the same shape as the product and a molten metal (also called a molten metal or molten soup). This casting method does not require The frequent operation procedures such as core or mold clamping have many advantages such as easier design, more customized, and short delivery time.

In the lost foam casting method, the cast resin melt is used to thermally decompose the synthetic resin foam. Therefore, there is a disadvantage that a large amount of gas and residue generated by the thermal decomposition cause casting defects. In the lost foam casting method, in order to prevent the residue defects caused by the thermal decomposition of the synthetic resin foam, as well as the sticky sand defects that leak into the sand mold due to the destruction of the paint film layer by the molten metal, a mold coating agent for lost foam is used . The residue defect is a phenomenon in which when the synthetic resin foam model is replaced with molten metal, when the discharge of thermal decomposition gas is insufficient, it becomes thermal decomposition residue and is caught in the upper part of the casting product. In order to prevent the phenomenon of residue defects, the pyrolysis gas of the synthetic resin foam model must be efficiently discharged to the mold side. Regarding the problem of residue defects, it is also necessary to continue to maintain a strong coating film layer during the period before the solidification of the molten metal ends.

In the conventional coating agent for lost foam, organic substances, cellulose and the like are mostly added, and the effect is that the organic substances and cellulose burn and disappear due to heat during casting. Therefore, the portions where the organic substances and cellulose once existed become voids. Since the voids become pores, the gas generated by the thermal decomposition of the synthetic resin foam can be efficiently discharged, and therefore, residue defects can be reduced. However, if cellulose is added to prevent residue defects, it may cause problems such as long drying time of the coating film layer or insufficient strength of the coating film layer.

Based on the above, the development of a lost foam coating composition with high safety, fast drying, high strength and capable of further suppressing residue defects is an important subject of current research.

The present invention provides a lost foam coating composition, by adding an organic polymer to replace cellulose, to improve the problems such as the drying time of the paint film layer of the conventional lost foam coating composition is too long or the strength of the paint film layer is insufficient, therefore, it can be Improve safety and strength, speed up drying time and suppress residue defects.

The lost foam coating composition of the present invention includes a refractory bone material and an organic polymer, wherein the content of the organic polymer is 5 to 10 parts by weight relative to 100 parts by weight of the refractory bone material.

In an embodiment of the invention, the organic high molecular polymer includes acrylic resin, polyvinylpyrrolidone, or a combination thereof.

In an embodiment of the present invention, the content of the refractory aggregate is 40 to 60 parts by weight relative to 100 parts by weight of the lost foam coating composition.

In an embodiment of the invention, the lost foam coating composition further includes a suspending agent, wherein the content of the suspending agent is 0.5 parts by weight to 1 part by weight relative to 100 parts by weight of the lost foam coating composition.

In an embodiment of the invention, the lost foam coating composition further includes a binder, wherein the content of the binder is 1 to 5 parts by weight relative to 100 parts by weight of the lost foam coating composition.

In an embodiment of the present invention, the lost foam coating composition further includes additives, and the additives include surfactants, antibacterial agents, preservatives, thickeners, suspension aids, leveling agents, dispersants, or thixotropic agents, wherein The content of the additive is 1 part by weight to 4 parts by weight relative to 100 parts by weight of the lost foam coating composition.

Based on the above, the lost foam coating composition of the present invention replaces cellulose by adding an organic polymer, therefore, it does not affect the thermal decomposition gas discharge of the synthetic resin foam, and can greatly increase the strength of the coating film and greatly reduce the coating Film drying time. Adding organic polymer to the lost foam coating composition has good compatibility, does not change the properties and performance of the lost foam coating composition, and can effectively improve the early strength of the coating film layer. After loading the sand mold, the coating film is not easy to fall off and crack. In addition to the high-efficiency exhaust performance, the lost foam coating composition of the present invention will not form sticky sand due to the high porosity of the coating itself. In addition, the organic high molecular polymer itself has a strong bonding ability, therefore, it can make the lost foam coating composition not easy to crack due to the overlapping of the bonding force, and more effectively prevent the cracking phenomenon during molding.

In order to make the above-mentioned features and advantages of the present invention more obvious and understandable, the following embodiments are specifically described as follows.

In this document, the range represented by "one value to another value" is a schematic representation to avoid listing all the values in the range one by one in the specification. Therefore, the description of a specific numerical range covers any numerical value within the numerical range and the smaller numerical range defined by any numerical value within the numerical range, just as the arbitrary numerical value and the smaller numerical value are clearly written in the specification The scope is the same.

The invention provides a lost foam coating composition, which can improve safety and strength, accelerate drying time and suppress residue defects. In the following, specific embodiments are cited as examples by which the present invention can indeed be implemented.

The lost foam coating composition of the present invention mainly includes refractory aggregates and organic high molecular polymers. By adding organic high molecular polymers to replace cellulose, the various shortcomings of the conventional lost foam coating composition are improved. Hereinafter, various components in the lost foam coating composition will be described in detail. ＜ Refractory bone materials ＞

In this embodiment, the refractory aggregate may include quartz, gibbsite, talc, pyrophyllite, forsterite, kaolin, zirconia, magnesia, kyanite, mullite, squamous graphite, microcrystalline graphite or The combination, but the invention is not limited to this, can also use other refractory bone materials can be used for casting purposes. The content of the refractory aggregate relative to 100 parts by weight of the lost foam coating composition is, for example, 40 parts by weight to 60 parts by weight. When the content of the refractory aggregate is 40 parts by weight or more, the coating film layer defects such as drying property and crack prevention can be improved; when the content of the refractory aggregate is 60 parts by weight or less, the coating workability can be improved. < Organic polymer polymer >

In this embodiment, the organic high molecular polymer may include acrylic resin (molecular weight 30,000 to 40,000, Tg point 20 to 22°C, solid matter: 56±1%, viscosity 1500 cps to 3500 cps, Minimum film-forming temperature: 20~22℃), polyvinylpyrrolidone (molecular weight: 200,000 to 360,000, Tg point: 25℃ to 30℃, solids ≤95%, ash residue ≥0.2%, minimum film-forming temperature 30 ℃~35℃) or a combination thereof. Considering the molecular weight and the TG point, the content of the organic polymer is, for example, 5 parts by weight to 10 parts by weight relative to 100 parts by weight of the refractory aggregate. The organic macromolecular polymer used in the present invention has the following characteristics: 1) The residual amount of ash is low (less than 0.25%); 2) The drying time is short, and it can be completely dried within 4 hours; 3) The drying rate is stable and it is not easy to make Paint cracking; 4) Decomposition temperature is between 120 ~ 150 ℃; 5) Add to the paint, the strength of the paint after drying is 100 gf ~ 120 gf.

Acrylic resin has the advantages of fast reaction rate, good drying process safety, no solvent pollution and low price. The drying time is shorter, and it can be completely dried within 4 hours at a drying temperature of 50℃~60℃. The residual ash (carbon residue) after combustion is less than 0.25%, so it will not affect the yield of castings. When the acrylic resin is changed from the emulsion state to the transparent film state, the shrinkage rate is not more than 1%, so it will not cause cracks in the paint. Acrylic resin has water resistance after hardening and drying, and will not absorb moisture in the air. Therefore, it can prevent the paint from regaining moisture and becoming soft. The effective component content of the acrylic resin is, for example, 50% to 65%, so as to have the above advantages. Too little active ingredient means that the water content is too much, and the drying time will be elongated accordingly; too much active ingredient will cause the resin to be difficult to disperse, the drying area and speed are uneven, and the drying is too violent, which is easy to form cracks. When the active ingredient is 55%, the acrylic resin can be evenly dispersed in the paint.

Polyvinylpyrrolidone has excellent solubility, low toxicity, film formation, chemical stability and adhesion. At the same time, polyvinylpyrrolidone has significant binding capacity and can form complexes with many different compounds. Polyvinylpyrrolidone has a solubilizing effect and a dispersing effect, which can make the suspension agent and acrylic resin in the coating uniformly dispersed and stable, and also has an adsorption effect to reduce the interfacial surface tension to a certain extent. Therefore, it can help the coating stabilize Attached to Styrofoam. In this embodiment, the K value of polyvinylpyrrolidone is preferably K90, in addition to having good adhesion, an appropriate K value can make the coating film drying speed moderate. If the K value is too low, the film formation of the coating is too slow; if the K value is too high, the phenomenon of cracking on the surface of the coating will occur due to the characteristics of polymer drying shrinkage. ＜ suspending agent ＞

The lost foam coating composition of the present invention may further include a suspending agent, and the suspending agent may include attapulgite, lithium bentonite, sepiolite, bentonite, montmorillonite, or a combination thereof. The content of the suspending agent is, for example, 0.5 parts by weight to 1 part by weight relative to 100 parts by weight of the lost foam coating composition. When the content of the suspending agent is within this range, it can have good suspending performance and viscosity. < Binder >

The lost foam coating composition of the present invention may further include a binder, and the binder may include industrial starch, gum arabic, xanthan gum, methyl cellulose, or a combination thereof. The content of the binder is, for example, 1 part by weight to 5 parts by weight relative to 100 parts by weight of the lost foam coating composition. When the content of the binder is within this range, the drying time required for the coating film layer and the bonding strength of the coating film layer can be simultaneously guaranteed. < Additives >

The lost foam coating composition of the present invention may further include additives, and the additives may include surfactants, antibacterial agents, preservatives, thickeners, suspension aids, leveling agents, dispersants, or thixotropic agents. The content of the additive is, for example, 1 part by weight to 4 parts by weight with respect to 100 parts by weight of the lost foam coating composition. Since the lost foam coating composition of the present invention is water-based, the dispersant may include distilled water.

The operation method of the lost foam coating composition of the present invention is as follows. Add 10% distilled water and bentonite to the mixing tank and stir at 800 rpm for 15 minutes. After the stirring is completed, add the organic polymer, binder and additives into the mixing tank and stir at 800 rpm. The stirring time is After 10 minutes, after the stirring is completed, the mixture is taken out and added to the kneader. After adding 5~10% distilled water and refractory bone material, cover the upper cover of the kneader and evacuate the kneader to make the kneading process under a vacuum environment. Stir in a vacuum environment, the kneading time is 15 minutes, and the finished product can only be taken out after the kneading is completed.

In summary, the present invention provides a lost foam coating composition with high safety, fast drying, high strength and capable of further suppressing residue defects. By adding organic polymer to replace cellulose, the conventional lost foam coating composition is improved The drying time of the paint film layer of the product is too long or the strength of the paint film layer is insufficient. Adding organic polymer to the lost foam coating composition has good compatibility, does not change the properties and performance of the lost foam coating composition, and can effectively improve the early strength of the coating film layer. After loading into the sand mold, the coating film is not easy to fall off and crack. In addition to the high-efficiency exhaust performance, the lost foam coating composition of the present invention will not form sticky sand due to the high porosity of the coating itself. In addition, the organic high molecular polymer itself has a strong bonding ability, therefore, the lost foam coating composition can not easily crack due to the overlapping of the bonding force, and the cracking phenomenon during molding is more effectively prevented.

Although the present invention has been disclosed as above by the embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be subject to the scope defined in the appended patent application.

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Claims (7)

A lost foam coating composition, comprising: refractory aggregate, wherein the content of the refractory aggregate is 40 to 60 parts by weight relative to 100 parts by weight of the lost foam coating composition; an organic polymer, Wherein the content of the organic high molecular polymer is 5 parts by weight to 10 parts by weight relative to 100 parts by weight of the refractory bone material; the suspending agent, wherein, relative to 100 parts by weight of the lost foam coating composition, The content of the suspending agent is 0.5 parts by weight to 1 part by weight; and a binder, wherein the content of the binder is 1 part by weight to 5 parts by weight relative to 100 parts by weight of the lost foam coating composition. The lost foam coating composition as described in item 1 of the patent application range, wherein the organic high molecular polymer includes acrylic resin, polyvinylpyrrolidone, or a combination thereof. The lost foam coating composition as described in item 2 of the patent application range, wherein the molecular weight of the acrylic resin is 30,000 to 40,000, the glass transition temperature is 20°C to 22°C, and the solid content is 56±1%. The viscosity is 1500cps to 3500cps, and the minimum film forming temperature is 20 to 22°C. The lost foam coating composition as described in item 2 of the patent application range, wherein the molecular weight of the polyvinylpyrrolidone is 200,000 to 360,000, the glass transition temperature is 25°C to 30°C, the solid content is 95% or less, and the lowest The film forming temperature is 30°C to 35°C. The lost foam coating composition as described in item 2 of the patent application range, wherein the effective component content of the acrylic resin is 50% to 65%. The lost foam coating composition according to item 2 of the patent application scope, wherein the K value of the polyvinylpyrrolidone is K90. The lost foam coating composition as described in item 1 of the patent application scope further includes additives including surfactants, antibacterial agents, preservatives, thickeners, suspension aids, leveling agents, dispersing agents or contact agents A modifier, wherein the content of the additive is 1 part by weight to 4 parts by weight relative to 100 parts by weight of the lost foam coating composition.