JPS59137147A - Water soluble molding sand binder and application thereof - Google Patents

Abstract

PURPOSE:To obtain a molding sand binder for a casting mold having a good collapsing property by mixing a water soluble glue and a water soluble thermosetting resin in a specific amt. CONSTITUTION:A water soluble molding sand binder obtd. by mixing 100pts.wt. water soluble glue A and 5-80pts.wt. water soluble thermosetting resin B is compounded with molding sand in a range of 1-10pts.wt. to 100pts.wt. sand and both are kneaded and are made into a water collapsible casting mold. Shaking out of sand after charging of a molten metal is thus made easy in the stage of casting a light alloy in particular. The glue A refers to various kinds of PVA, soluble starch or polysaccharide such as soluble dextrin, and the resin B refers to a water soluble type resin among a phenolic resin, urea resin, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-soluble foundry sand binder and its uses, and more particularly to a mold from which sand can be easily removed after pouring, particularly when casting light alloys, and a mold thereof from which sand can be easily removed after pouring. This invention relates to a sand packing agent for molding molds.

After pouring, in order to remove the mold, that is, the core, which is encapsulated in the mold, the core needs to collapse.

If the material of the casting is cast iron, the pouring temperature is 1300~1
Due to the high temperature of 600℃, the foundry sand binder
For example, even with relatively heat-resistant organic materials such as phenolic resin, thermal decomposition causes the resin itself to lose its sand-packing ability, resulting in the core collapsing after pouring. In the case of castings whose temperature is relatively low, such as around 700 degrees Celsius, thermal decomposition will no longer occur in molds using phenolic resin as a binder as described above, and therefore, after pouring, The core remains in the casting without being disintegrated.

Traditionally, shell mold cores using phenolic resin as a binder have been most commonly used in the casting of aluminum alloys, and therefore the castings have been heat treated to remove sand after pouring.

On the other hand, recently, the disintegrability of the mold (core) has become important, and for this reason, so-called urethane polyol-type binders, which use a polyol component and an isocyanate component, are also used. However, when using such a method, the pot life after the sand is mixed with a binder is limited, and it takes a considerable amount of time to harden during mold molding, so the mold It also has the disadvantage of extremely poor productivity.

However, as a result of intensive study, the present inventors found that a mold (core) was molded using a binder obtained by mixing a water-soluble glue and a water-soluble thermosetting resin, and water treatment was required after pouring. 1: The productivity of this type of mold is comparable to that of a shell mold, and the pot life of the mixed sand is almost infinite, and the mold is easily collapsed after pouring. The present invention was completed after discovering that no thermal energy was required for sand removal.

That is, the present invention provides a water-soluble foundry sand binder made by mixing (A) a water-soluble sizing agent and (B) a water-soluble thermosetting resin as essential components; The present invention also provides a method for applying the binder to a water-disintegratable mold, that is, a water-disintegratable core, as a binder component.

Here, the above water-soluble sizing agent (A) is a natural or synthetic polymer typified by various polyvinyl alcohols, polysaccharides such as soluble starch or soluble dextrin, or saccharide derivatives such as carboxymethyl cellulose or hydroxyethyl cellulose. Refers to a single compound or a mixture of water-soluble compounds.

By the way, when using a water-insoluble polymeric substance such as wheat flour, if it is mixed with the other water-soluble thermosetting resin (B), precipitation will occur, and as a result, each time the mixture is used, Furthermore, molds made using such a mixture may not be sufficiently wetted by the binder, resulting in non-uniform mixing of the sand and binder. , high mold strength cannot be obtained.

On the other hand, the above-mentioned water-soluble thermosetting resin (B) refers to water-soluble types of phenol resins, urea resins, melamine resins, furan resins, etc. that are commonly used as this type of foundry sand binder. .

Of the water-soluble sizing agents (A) and water-soluble thermosetting resins (B) listed above, particularly preferred ones are listed below.The former sizing agent (A) is compatible with the latter resin (B). Suitable materials are those that are soluble, do not increase viscosity too much when mixed, and harden (gelatize) by releasing water when heated; in this sense, dextrin or starch are suitable; The resin (B) is a resol type water-soluble phenol resin or the like.

The mixing ratio of these water-soluble sizing agent (A) and water-soluble thermosetting resin (B) is the solid content ratio, and the former sizing agent (
5 to 80 parts by weight of the latter resin (B) per 100 parts by weight of A)
Parts by weight range, optimally from 15 to 25 parts by weight.

- If the amount of thermosetting resin (B) exceeds the above range, the disintegrability of the mold will be poor, and on the other hand, if the amount of glue (A) is too much, the normal strength of the mold will become weak.

In extreme cases, when this glue (A) is used alone, the strength decrease due to moisture absorption of the mold is much greater than when both components (A) and (B) are used in combination, and the strength is There's a problem.

When the binder of the present invention thus obtained is actually used, it is appropriate to form it into an aqueous solution of 40 to 50% by weight.

Next, the binder of the present invention can be mixed with sand and kneaded to form a water-disintegratable mold, and forming such a mold is also one use of the binder of the present invention.

The amount of the binder of the present invention added to the sand is generally approximately the same as the amount commonly used as a binder for molds of this type, and is 1 to 10 parts by weight relative to 100 parts by weight of the sand. The range of 3 to 5 parts by weight is most preferable, especially considering the strength performance and the amount of gas generated by the mold.

The mold is formed by adding the binder obtained as described above to silica sand and kneading it, and then blowing the wet kneaded sand into a heated mold. A better method is to mold it.

In addition, as for the firing method in the mold, since the wet strength of the kneaded sand is high, it is molded in a wooden model, etc., and then the mold is cut out and then passed through a drying oven, or it is irradiated with microwaves such as a microwave oven. A better method is to let it burn.

The firing temperature in the mold at this time is 200 to 220°C, and the firing time is 45 to 90 seconds.

In addition, the pressure for blowing the mixed sand into the mold is 3 to 5.
kg/cIA is appropriate.

In order to disintegrate the mold by water treatment after pouring the metal into the mold, the casting after pouring the metal can be immersed in water as it is, or it can be sprayed with water in the form of a mist. good.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. In the following, all parts and percentages are based on weight unless otherwise specified.

Example 1 [Monoboule 10IJ (dextrin manufactured by Shishi Starch Industries) and [Priophen TD-617J (resol type phenolic resin manufactured by Dainippon Ink Chemical Industry @) were mixed at a weight ratio of 8:2 in terms of solid content. A binder having a solids content of 50% was obtained by mixing with a stirrer.

Example 2 "Monoboule 101" and [Priorfen TD-61]
A binder was obtained in the same manner as in Example 1, except that the weight ratio of one form to 7J was changed to 7:3.

Example 3 A binder was obtained in the same manner as in Example 1, except that the same amount of Best 300J (starch manufactured by Shishi Starch Industries) was used. A binder was obtained in the same manner as in Example 1, except that the same amount of urea resin manufactured by Kagaku Kogyo (solid content = 50%) was used.

Example 5 3000 parts of flattery silica sand was placed in a small multi-arm mixer (90 rpm), and 150 parts of the binder obtained in Example 1 was added.
The mixed sand was prepared by adding 50% of the mixture and kneading it for 1 minute, and it was decided to use it for a performance test when applied as a mold.

Example 6 Kneaded sand for molds was obtained in the same manner as in Example 5, except that the same amount of the binder obtained in Example 2 was used.

Example 7 Kneaded sand for molds was obtained in the same manner as in Example 5, except that the same amount of the binder obtained in Example 3 was used.

Example 8 Kneaded sand for molds was obtained in the same manner as in Example 5, except that the same amount of the binder obtained in Example 4 was used.

Comparative Example 1 50% aqueous solution 15 of "Monoboule 101" as a binder
A control kneaded sand was obtained in the same manner as in Example 5 except that only 0 part was used.

Comparative Example 2 As a binder [TS of Pryophen TO-617J]
A control kneading sand was obtained by straining G in the same manner as in Example 5, except that only o mixed with p was used.

Table 1 G shows where comparative tests of various performances were conducted for each of the kneaded sands obtained in Examples 5 to 8 and Comparative Example 1.2.
These are shown below.

Test conditions Kneaded sand for transverse rupture strength test was heated to 210°C in a mold (20 x 20
A test piece was prepared by blowing into X12 (1 m), and the transverse rupture strength was measured, and the average value of 4 measurements is shown.

Testing machine: Honto box blowing machine for testing room Blow pressure: 4 kg/cat Mold temperature = 210°C Firing time: 90 seconds The transverse rupture strength over time after molding was measured at 20°C x 70
It was stored in a desiccator adjusted to %IlH, and the value was measured every number of days.

Mixed sand for disintegration test at 45°C was heated to 210°C.
A test piece was prepared by hand molding in a wmh mold and firing for 90 seconds.

Next, this was wrapped twice in aluminum foil and left in an electric furnace at 450°C for 20 seconds, and after that, the rotary sieve was removed using a machine to remove sand on a 10-mesh sieve, so that no test pieces remained on the sieve. The time (seconds) and the ratio (%) of the amount of sand 2 minutes after starting sand removal to the amount before sand removal are taken as the collapsibility value.

In addition, the measured value was shown as the average value of 4 times.

A test piece immediately after molding prepared for collapsing transverse rupture strength when immersed in water is immersed in water, and the state of collapse of the test piece is observed while it is left for 30 minutes.

Here, the term "collapsed" refers to a state in which the specimen loses its shape and completely collapses.

As is clear from the results in Table 1, molds using the binder of the present invention have good disintegration properties even without water treatment, but the disintegration properties become even better with water treatment. I know this.

Claims (1)

[Claims] 1. A water-soluble foundry sand binder prepared by mixing 100 parts by weight of a water-soluble sizing agent (A) and 5 to 80 parts by weight of a water-soluble thermosetting resin (B). 2. A water-soluble foundry sand binder obtained by mixing 100 parts by weight of a water-soluble sizing agent (A) and 5 to 80 parts by weight of a water-soluble thermosetting resin (B) is added to 100 parts by weight of sand. 1 to
Application to a mold that can be easily disintegrated by water treatment after pouring, characterized in that the mixture is mixed in a range of 10 parts by weight to form a water-disintegratable mold.