JPS58202945A - Resin composition for binding of casting sand particle - Google Patents

Abstract

PURPOSE:To assure the shelf life of resin-coated sand and to improve the yield of forming cores by adding a polymn. inhibitor in a titled compsn. of a crystallizable unsatd. polyester resin wherein org. peroxide is used as a catalyst for curing. CONSTITUTION:5-30pts.wt. polymn. inhibitor is added to 100pts.wt. org. peroxide of hydroperoxide system in resin-coated sand for castings consisting essentially of a crystallizable unsatd. polyester resin wherein org. peroxide is used as a catalyst for curing. The crystallizable unsatd. polyester is solid at an ordinary temp. at which gelling cannot easily arise, but in the case of using org. peroxide of hydroperoxide system, radicals are generated by redox reaction and gelling is caused as an entirely specific problem. The polymn. inhibitor is added to the compsn. of this resin compsn. of this invention in order to prevent the gelation during storage. The inhibitor is required to have the capacity to prevent gelation at an ordinary temp. and not to retard the reaction for curing at elevated temp. and is polyhydric phenols, quinones, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin composition for bonding foundry sand grains containing a crystalline unsaturated polyester resin as a main component. The present invention relates to a resin composition for bonding foundry sand grains for resin-coated sand used in casting molds, especially cores.

Conventionally, when molding molds and cores, coated sand doped with a resin composition for binding foundry sand grains containing phenolic resin as the main component is used, and the so-called shell molding method is generally used. . This shell molding method is widely used due to its features such as being able to mold and fire the mold and core in a short time, and the mold and core after molding and firing being strong and easy to handle. A pungent odor such as ammonia gas may be generated during molding and firing or casting using them, and when used as a core in the casting of metals with low casting temperatures such as aluminum, the heat of the molten metal may cause carbonization of the phenolic resin. In order to promote this process, the residual strength of the core is high and it cannot be easily discharged, and therefore it has disadvantages such as requiring a heating process for each casting called "l-sand firing". For this reason, research has been conducted to improve the drawbacks of the shell molding method described above from the standpoint of saving resources and energy in casting products such as aluminum. A resin composition for binding foundry sand grains as a main component has been proposed.

On the other hand, as a result of further study on such a resin composite acid for bonding foundry sand grains, the present applicant et al.
In No. 944, we proposed a radical polymerization catalyst that improves the strength (referred to as hot strength) immediately after firing and molding a mold, especially a core, using resin-coated sand mainly composed of crystalline unsaturated polyester resin. However, the practicality of foundry sand grain binding resin compositions containing crystalline unsaturated polyester resins as a main component has been improved. However, when resin-coated sand containing crystalline unsaturated polyester resin as the main component is used to mold an actual intake manifold water jacket core, the core molding yield decreases as time passes from the creation of the resin-coated sand. However, this created a new problem of poor productivity.

The present inventors conducted further research into the cause of this decrease in core molding yield, and found that when a hydroperoxide-based organic peroxide was used as a radical polymerization catalyst, the storage stability of Resin Cover-1 decreased. Unfortunately, it has been found that gelation of the surface resin composition gradually progresses in the bare tube, and this gelation causes a decrease in retention when molded into a core.

Hydroperoxide-based organic peroxides are generally R-
00H (where R indicates an organic radical), such as paramethane hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, tert-butyl hydroperoxide, paracymene hydroperoxide, 1 Examples include 1,3,3-tetramethyl-1-butyl hydroperoxide. The characteristics of these hydroperoxide-based organic peroxides are the redox reaction shown by the following formula.
RO generates radicals even at extremely low temperatures,
It is to cause gelation. In other words, for foundry sand grains...
l'1 Due to the presence of impurities (e.g. iron oxide) that cause this redox reaction, the present inventors experimentally found that after preparing resin-coated sand, the polymerization of the resin progressed and the gel fraction reached 10% in one week. I made sure that the money was reached.

As a result of various studies in order to solve the above-mentioned gelation problem, the inventors of the present invention discovered that resin-coated sand was produced by adding 5 to 30 parts by weight of a polymerization inhibitor to 100 parts by weight of hydroperoxide-based organic peroxide. The present invention was achieved by discovering that gelation during storage can be prevented and storage stability can be ensured.

Therefore, in the foundry resin-coated sand mainly composed of a crystalline dissonant polyester resin using an organic peroxide as a curing catalyst, which is the resin composition for bonding foundry sand grains of the present invention, 100% by weight of hydroperoxide-based organic peroxide is used. 5 to 3 for part
It is characterized by the addition of a polymerization inhibitor of 0%.

The term "crystalline unsaturated polyester" as used in the present invention refers to unsaturated polyester that is solid at room temperature and has no tackiness, and has crystallinity in which a diffraction intensity peak is observed in which the crystalline portion can be clearly determined by X-ray diffraction. , is well known and has been described in many documents, such as the above-mentioned Japanese Unexamined Patent Publication No. 54-80234.

Next, polymerization inhibitors are generally used in unsaturated polyester resins, which are usually liquid resins at room temperature composed of unsaturated alkyds and vinyl monomers, but are extremely reactive. Because it is rich,
Since gelation occurs and storage is difficult, polymerization inhibitors are added to prevent this. Therefore, the polymerization inhibitor is required to have two points: a binding ability to prevent gelation at room temperature, and no inhibiting reaction during the curing reaction at high temperatures.

In the non-invention, as mentioned above, since crystalline unsaturated polyester resin is an unsaturated polyester resin that is solid at room temperature, gelation can easily occur, and the use of a polymerization inhibitor was completely unthinkable. However, when using hydroperoxide-based organic peroxides, a completely specific problem is that the redox reaction generates radicals and causes gelation, and it is necessary to prevent gelation due to the progress of polymerization during storage. A specific amount of inhibitor is used to prevent this from occurring. Polyhydric phenols, quinones, phenols, etc. are generally used as polymerization inhibitors, such as hydroquinone, pt-butylcatechol, 2. s-ji-t
-Butylhydroquinone, mono-t-butylhydroquinone, methylhydroquinone, tert-butylhydroquinone, rosebenzoquinone, naphthoquinone, rosexyquinone, phenanthraquinone, 2,5-diacetoxyrosenzoquinone, ditert-butylvalacresol hydroquinone monomethyl ether , alphanaphthol and the like. In the present invention, the polymerization inhibitor is hydroperoxide-based organic peroxide 1 (
5 to 30 parts by weight are used per 10 parts by weight.The reason for this is that if the amount is less than 5 parts by weight, the addition of the polymerization inhibitor has no effect;
This is because if the amount exceeds 30,000 parts by weight, the polymerization reaction will not proceed when the entire mold or core is formed using coated sand, and the strength will not be maintained, which is undesirable.

As described above, the resin composition for bonding casting sand of the present invention is
By blending a specific amount of a crystalline unsaturated polyvarnish inhibitor containing a hydroperoxide-based organic peroxide as a radical polymerization catalyst, the storage stability of coated sand coated with this type of resin composition is improved, and molds, This has achieved prevention of a decrease in the molding yield of the core.

The present invention will be illustrated by the following examples and reference examples.

Example 1 Nikko silica sand No. 6 heated to 180'O 4 to 4! was put into a speed mixer manufactured by Enshu Tekko Co., Ltd., and then crystalline unsaturated polyester resin [manufactured by Mitsui Toatsu Chemical Co., Ltd.,
Product name Nistar N2000. 5 parts by weight of diallyl phthalate monomer per 100 parts by weight of resin as a crosslinking agent;
100 g of rosebenzoquinone was added as a polymerization inhibitor in an amount of 0.01 part by weight per 100 parts by weight of the resin, and the mixture was stirred and mixed to be fused to the surface of the sand grains. Continue stirring, and when the temperature reaches approximately 110°C, mix the hardening liquid [cumene hydroperoxide ((, HP) 1,'og, dicumyl peroxide (DGP)] in advance. ,,Og.

・Rabbenzoquinone o, ol gk ethyl alcohol 2
After adding about 229 (dissolved in 0.9) and dispersing and mixing it on the surface of the sand grains, 4 g of calcium stearate was added to a sand 70"C machine, and when the sand grains were loosened, it was taken out of the speed mixer and resin-coated sand was prepared. (a) K was obtained. Using the same method, 10 types of resin-coated sand were prepared as shown in Table 1, but in all cases (b) to (j), the amount of polymerization inhibitor parabenzoquinone added was changed. It is something.

The storage stability of the 10 types of resin-coated sand produced in this manner was investigated by looking at changes in tensile strength at elevated temperatures.

In other words, using a shell sand high-temperature tensile test sail made by Dietert, and keeping the firing conditions constant at 230'0170 seconds, the initial strength # of the resin-coated sand (i.e., the strength of the manufactured daily mill) was reduced by 5. %, the resin-coated sand did not change over time and was judged to have good storage stability.Measurements were made for a total of 6 days after the resin-coated sand production mill, 1 day, 3 days, 5 days, 7 days, and 10 days. times.

The measurement results are shown in Table 2.

Table 2 Change in strength with temperature (Icg/, L2) 'l'''''''''''''l1l- As is clear from Table 2, rosebenzoquinone is a hydroperoxide-based organic peroxide (HP 100
Addition of 5 to 30 parts by weight relative to parts by weight brought about a significantly good effect. It is thought that when the amount of rosebenzoquinone added is small, gelation progresses during storage and the relative amount of cured resin during the tensile test decreases, resulting in a decrease in strength. On the other hand, if the amount of rosebenzoquinone added is too high, the storage period of the resin-coated sand will be long, but even if the catalyst becomes radical to cause the curing reaction, it will not be able to act effectively due to the large amount of inhibitor, and therefore the initial It is thought that the strength will also decrease.

Reference Example 1 Using the same method as in Example 1, four types of resin-coated sand (A to A) shown in Table 3 below were produced.

Table 8 TBP = tert-butyl peroxybenzoate BP
O = benzoyl peroxide TBfi = tert-butyl hydroperoxide
There is no polymerization inhibitor in the alcoholic solution obtained by bath-dissolving the peroxide, that is, in the curing solution. The W fat-covered sand thus produced was subjected to the same tensile test as in Example 1, and the change in strong FIIL at temperature was measured, and the obtained M values are shown in Table 4 below.

Table 4 Forced Change at Temperature (kg/cIrL2) From Table 4, (1) If a hydroperoxide-based organic peroxide is not used, the resin-coated sand will not change over time;
(2) It is clear that when a hydroperoxide-based organic peroxide is used, it changes over time, but the initial performance (strong V) is high. In other words, because hydrocarbon-based organic peroxides have a greater resin gelation ability than other organic peroxides, they are effective in both improving the initial temperature strength and reducing the shelf life of resin-coated sand. It is thought that it is working.

Generally, unsaturated polyester resins are commercially available with a crosslinking agent, typically styrene monomer, added after synthesis, but in order to prevent polymerization during the addition of this crosslinking agent, the amount of the crosslinking agent ranges from several tens of ppm to zero. ．． A polymerization inhibitor of about 1% O is added. The reason for this is that commercially available unsaturated polyester resins are in a liquid state, so you only need to add a curing catalyst when necessary. Since it is used in the form of resin-coated sand, the storage stability in the state containing organic peroxides as curing catalysts became a problem. In the present invention, as shown in Example 1, this problem was completely solved by adding a very large amount of polymerization inhibitor to VC1, and useful resin-coated sand could be provided.

Example 21 Six types of resin-coated sand shown in Table 5 were exploded using the method shown in Example 1. In place of the parabenzoquinone in Example 1, the curing liquid contained GHP19 and DOPII in alcohol 2oI.
I was dissolved and a polymerization inhibitor as shown in Table 5 was further combined and dissolved in an amount of 10 parts by weight based on the amount of caplooz. In the same manner as in Example 1, the strong electric current change at temperature was measured on the day of production, 3 days later, and 10 days later, and the results are shown in Table 5.

From the above Examples and Reference Examples, in the resin composition for bonding sand grains in foundries mainly composed of crystalline unsaturated polyester using a hydroperoxide-based organic peroxide,
It is clear that addition of a polymerization inhibitor is extremely effective in preventing gelation degradation caused by hydroperoxide-based organic peroxides.

Patent applicant: Nissan Motor Co., Ltd. Same applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. In a resin composition for bonding foundry sand grains mainly composed of a crystalline unsaturated polyester resin using an organic peroxide as a curing catalyst, 100% of the hydroperoxide-based organic peroxide is used.
A resin composition for bonding foundry sand grains, characterized in that a polymerization inhibitor is added in an amount of 5 to 30 parts by weight.