JPH09295101A - Resin coated sand and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide resin coated sand which improves the mechanical strength of a product in a significant level, displays excellent releasing property and contributes to the superior performance of the product, the lowering of defective ratio, the improvement of workability and the reducing of cost without damaging the placticality, and the manufacture thereof. SOLUTION: This resin coated sand is coated with phenol resin base binder blending 1-20wt.% one or more kinds of plasticizer selected among paratoluene sulfonamide, dicyclo hexylphthalate and triphenyl phosphate and 1-20wt.% thermoplastic resin having <100 poise melting viscosity at 150 deg.C and <=20% compatibility with the phenol resin at 150 deg.C in the phenol resin on the sand. Then, the resin coated sand is manufactured by melt-coating the phenol resin base binder blended with 1-10 wt. parts phenol resin, 0.02-1 parts wt. one ore more kinds of the above plasticizer and 0.02-1 parts wt. the above thermoplastic resin to 100 parts wt. sand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to pressure molding with a heating die,
The present invention relates to a resin-coated sand used for casting, blow molding and the like and a method for producing the same.

[0002]

2. Description of the Related Art Sand coated with a phenolic resin binder is used for producing molds and cores for shell molds, and for producing composite building materials as resin concrete (including mortar) materials. In these productions, attempts have been made to improve mechanical strength and releasability from the viewpoints of high performance of molded products, reduction of defective rate, and cost reduction.

As a method for improving the mechanical strength, a method of lowering the molecular weight of a phenol resin to improve the flow, a method of adding an additive such as a silane coupling agent, an amide wax, etc. are widely used. However, the method of lowering the molecular weight of the phenol resin to improve the flow is
There is a limit to lowering the molecular weight due to practical problems such as caking. Further, although the method of adding an additive such as a silane coupling agent or an amide wax has a strength improving effect to some extent, it is not directly proportional to the addition amount, and the effect is saturated from a certain point. There is also a method of using both in combination, but this is not sufficient for dramatically improving the strength.

In addition to the above-mentioned method, attempts have been made to blend various plasticizers with a phenol resin to improve the strength of a molded product (Japanese Patent Laid-Open Nos. 50-98847 and 50-98847). 63-117058, JP-A-59-1
56535, etc.). These methods are mainly characterized by improving the fluidity of the phenol resin at the time of melting by blending a liquid plasticizer. However, when used as resin-coated sand, it causes solidification or curing inhibition. There is a limit to the amount of compounding due to practical problems. Further, it cannot be said to be sufficient to improve the mechanical strength when molding the resin-coated sand to a significant level.

On the other hand, as a method for improving the releasability, a method of coating or spraying a mold releasing agent such as a silicone type or a fluorine type on a mold, and a method of adding a lubricant such as a fatty acid or its metal salt to a resin ( JP-A-62-127140) and the like are known, but the former requires frequent application or spraying of a release agent in order to ensure releasability, which causes a problem of mold stains. In the latter case, not only the blending amount is limited due to practical problems, but also the releasing effect is not sufficiently obtained. There is also a method of using both in combination, but it is hard to say that this also has a sufficient effect. Furthermore, no technology has been found that makes both improvement of strength and improvement of releasability compatible.

[0006]

Therefore, the object of the present invention is to improve the mechanical strength of a molded product at a significant level without impairing the practicality, and to obtain an excellent releasability during molding. It is an object of the present invention to provide a resin-coated sand which is exhibited and contributes to high performance of molded products, reduction of defective rate, improvement of workability and cost reduction, and a method for producing the same.

[0007]

That is, the present invention relates to a phenol resin containing 1 to 20% by weight of one or more plasticizers selected from paratoluene sulfonamide, dicyclohexyl phthalate and triphenyl phosphate.
And a melt viscosity at 150 ° C of less than 100 poise is 1
A resin-coated sand, characterized in that the sand is coated with a phenol resin-based binder prepared by blending 1 to 20% by weight of a thermoplastic resin having a compatibility with a phenol resin at 50 ° C. of 20% or less.

The present invention also relates to 100 parts by weight of sand,
Phenol resin 1 to 10 parts by weight and one or more plasticizers selected from paratoluene sulfonamide, dicyclohexyl phthalate and triphenyl phosphate in an amount of 0.02 to 1 part by weight and a melt viscosity at 150 ° C. of less than 100 poises. Of resin-coated sand, which is obtained by melt-coating with a phenolic resin-based binder obtained by mixing 0.02 to 1 part by weight of a thermoplastic resin having a compatibility with a phenolic resin at 150 ° C. of 20% or less. Is the way.

Hereinafter, the present invention will be described in detail. The sand used in the present invention is silica sand (for example, No. 3, No. 4, No. 5, and No. 5).
No. 6, No. 7), river sand, sea sand, crushed stone (2-5 mm),
Pumice stone and the like can be used, and these can be used alone or as a mixture. Of these, silica sand is particularly preferable.

Further, the phenol resin used in the present invention is not limited as long as it is solid, and phenol,
Cresol, xylenol and other phenols may be obtained by reacting formaldehyde in the presence of a catalyst, for example, novolac type phenol resin,
Resole type phenolic resins and modified phenolic resins thereof or resin mixtures thereof may be mentioned. These phenolic resins are used as solids in the presence or absence of hardeners.

The phenolic resin binder of the present invention is
The above-mentioned phenol resin is blended with a plasticizer and a thermoplastic resin. As this plasticizer, one or more plasticizers selected from paratoluene sulfonamide, dicyclohexyl phthalate and triphenyl phosphate are blended. With other plasticizers, the effect of the present invention does not sufficiently occur.

The phenolic resin binder of the present invention has a melt viscosity at 150 ° C. of less than 100 poise,
It is preferably less than 50 poise and has a compatibility with the phenol resin at 150 ° C. of 20% or less, preferably 5%.
The following thermoplastic resins are blended. As a thermoplastic resin,
Hydrocarbon-based resin oligomers that do not have a highly polar functional group are preferred. Examples of such a thermoplastic resin include low molecular weight polystyrene, petroleum resin, hydrocarbon oligomers such as coumarone-indene resin, and copolymers thereof. These are preferably solids at room temperature.

The melt viscosity of the thermoplastic resin can be measured by a cone plate viscometer. Regarding compatibility with phenol resin, 5 g of phenol resin and 5 g of thermoplastic resin are put in a glass container of 20 cc, melt-mixed at 150 ° C., and allowed to stand at this temperature for 120 minutes, and then the state of phase is observed. To measure. When the phase becomes one and is transparent, it is completely compatible (100%), when there are three phases, it is partially compatible, and the value of the formula [(intermediate phase volume / total volume) × 100] Percentage (%), a value that is quantitatively evaluated as incompatibility (0%) when two phases are still present or when one phase is suspended can be used.

In the present invention, the thermoplastic resin may be used alone or in combination of two or more kinds, but in the case of two or more kinds, it is the total amount. The blending ratio of the plasticizer and the thermoplastic resin is such that the content in the obtained phenol resin-based binder is 1 to
It may be 20% by weight, preferably 2 to 15% by weight, and the thermoplastic resin may be 1 to 20% by weight, preferably 2 to 15% by weight.

When the resin-coated sand is produced by directly blending these with sand without preparing a binder in advance, the blending ratio with respect to 100 parts by weight of the sand is 1 to 10 parts by weight of the phenol resin. The agent is 0.02 to 1 part by weight, preferably 0.03 to 0.9 part by weight, and the thermoplastic resin is 0.02 to 1 part by weight, preferably 0.03 to 0.9 part by weight.

If the compounding ratio of the plasticizer is small, the effect of improving the strength is not significant at a significant level, and if it is too large, only the effect as a bulking agent can be expected, and the curability during molding becomes slow. If the blending ratio of the thermoplastic resin is small, the effect of improving the releasability is not sufficient, and if it is too large, poor kneading occurs or the curability during molding becomes slow. When the blending ratio of the phenolic resin to the sand is low, the blending ratio of the plasticizer and the thermoplastic resin to the phenolic resin may sometimes exceed the above range.

The method of mixing the phenolic resin with the plasticizer and the thermoplastic resin is arbitrary, but each is made into a powder and mixed with powder, a method of pulverizing and mixing with the phenolic resin, a method of melt mixing, and a phenolic resin. There is a method of adding a plasticizer and a thermoplastic resin in the reaction or dehydration step, but the method is not limited to these. In order to bring out the effect with a small blending ratio, it is preferable to mix them as uniformly as possible, and from this point, the method of melt mixing them is more effective. Further, a method in which a phenol resin and a plasticizer are melt-mixed and a thermoplastic resin is pulverized and mixed is also effective. In addition, when the resin-coated sand is manufactured without being mixed in advance, each may be added and mixed.

In addition to the plasticizer and the thermoplastic resin, various additives such as a curing accelerator and a silane coupling agent can be added to the phenol resin binder of the present invention, if necessary. In addition, a hardening agent such as hexamethylenetetramine, a lubricant such as calcium carbonate and calcium stearate, and other additives can be added to this binder. These may be blended in the binder in advance, but may be blended simultaneously or separately when the resin-coated sand is produced.

As a method for producing the resin-coated sand of the present invention using the above binder, known techniques such as the hot marling method can be used. For example, 140 to 18 in advance
Put the sand heated to 0 ℃ into a kneader such as a whirl mixer,
A predetermined amount of the above binder may be added thereto, and the resin may be melted and coated with a resin. Further, the sand previously heated to 140 to 180 ° C. is put into a kneading machine such as a whirl mixer, and a predetermined amount of the phenol resin, the plasticizer and the thermoplastic resin, which are separately weighed, is added thereto, and melt coating is performed. Next, if necessary, water in which hexamethylenetetramine is dissolved is added, air is further blown, and when the sand lump collapses, an appropriate amount of a lubricant such as calcium stearate is added and discharged to obtain resin-coated sand.

To mold the resin-coated sand of the present invention to produce molded products such as shell molds, cores, and building materials, for example, pressure molding using a heating mold, casting molding, blow molding. Known molding techniques such as the above can be applied. By using the resin-coated sand of the present invention in the production of these, without impairing the practicality, the mechanical strength of the molded product is improved at a significant level, and excellent releasability during molding is obtained. To be

The term "improved mechanical strength" as used in the present invention means that the strength obtained when a plasticizer and a thermoplastic resin are not mixed with a phenol resin is a standard and the mechanical strength is improved at a significant level. Further, the term "improved releasability" as used in the present invention means that the releasability obtained when the plasticizer and the thermoplastic resin are not mixed with the phenol resin is taken as a standard and further improved.

[0022]

EXAMPLES The present invention will be described with reference to Examples and Comparative Examples. The strength, the releasability, and the practicality of the resin-coated sand were evaluated by the following methods.

Evaluation of Strength 20 kg of resin-coated sand was poured into a heating mold of 250 ° C.
/ Cm ² and hold for 2 minutes, then immediately remove the mold, 150
Six test pieces measuring 20 × 22.5 mm were prepared. After cooling this to room temperature and measuring the density, load speed 20 mm
The bending strength was measured at a speed of 100 mm / min and a span of 100 mm, and an average value and a standard deviation were obtained.

Evaluation of mold releasability: A mold having flat surfaces was set on the upper and lower plates of a pressure molding machine heated to 250 ° C., and a fixed amount of a fluorine-based mold release agent was sprayed on the mold surface only for the first time. 1 g of resin-coated sand
It is quickly placed so as to be 50 cm ² , a spacer of 4.5 mm thickness is sandwiched between the upper and lower molds, molded at 20 kg / cm ² , and held for 60 seconds. Next, the pressure is released and the mold releasability is observed from the upper and lower surfaces of the mold. The evaluation of releasability is
Molding was repeated 20 times. ◎: Releasability is sufficient on both upper and lower surfaces, ○: No releasability on both upper and lower surfaces, △: Some releasability is on one side, ×: Poor releasability. I went there. The number of mold releasability (times) is the number of times of molding from the beginning, and indicates the last molding times when the above evaluation was obtained.

Evaluation of Practicality The fusion point of the resin-coated sand was measured and evaluated for practicality.

Example 1 90 parts by weight of a novolac type phenol resin (S-phenol NK-8000 manufactured by Nippon Steel Chemical Co., Ltd.) having a softening point of 86 ° C., 5 parts by weight of paratoluenesulfonamide (melting point 135 ° C.), and coumaro 5 parts by weight of indene resin (melt viscosity: 12 poise, compatibility: 5%) were melt-mixed at 150 ° C. and then solidified to give 5% by weight of paratoluenesulfonamide.
A phenol resin binder containing 5% by weight of coumarone-indene resin was obtained. 100 parts by weight of silica sand (Fratary Sand No. 6) was previously heated to 160 ° C., put in a Shinagawa type tabletop mixer, 2.5 parts by weight of the above binder was added thereto and mixed with silica sand, and melted for 60 seconds. Cover. Subsequently, an aqueous solution prepared by dissolving 0.3 parts by weight of hexamethylenetetramine in 1.5 parts by weight of water was added, and after 15 seconds, air was blown from the blower. When the sand lumps collapsed, the air blow was stopped, and a steer was added as a lubricant. Calcium phosphate 0.05
Add parts by weight. After 30 seconds, the sand temperature was discharged at 70 to 80 ° C. to obtain resin-coated sand. This resin-coated sand was evaluated according to the evaluation method described above.

Example 2 Resin-coated sand was prepared in the same manner as in Example 1 except that the content of dicyclohexyl phthalate was 3% by weight and the content of coumarone-indene resin was 10% by weight instead of paratoluenesulfonamide. Was manufactured and evaluated.

Example 3 The content of triphenyl phosphate in place of paratoluene sulfonamide was 3% by weight, and the petroleum resin in place of coumarone-indene resin (melt viscosity 36 poise, compatibility 0%).
A resin-coated sand was produced and evaluated in the same manner as in Example 1 except that the content of was 3% by weight.

Example 4 100 parts by weight of silica sand (Fratary Sand No. 6) was previously added to 1 part.
Heat to 60 ° C, put in a Shinagawa tabletop mixer, and add 2 parts by weight of novolac type phenol resin (NK-8000, Nippon Steel Chemical Co., Ltd.) with a softening point of 86 ° C and 0.3 parts by weight of paratoluene sulfonamide. And 0.2 part by weight of coumarone-indene resin (melt viscosity 12 poise, compatibility 5%) are added, mixed with silica sand, and melt-coated for 60 seconds.
Subsequently, an aqueous solution prepared by dissolving 0.3 parts by weight of hexamethylenetetramine in 1.5 parts by weight of water was added, and after 15 seconds, air was blown from the blower. When the sand lumps collapsed, the air blow was stopped, and a steer was added as a lubricant. Add 0.05 parts by weight of calcium phosphate. After 30 seconds, the sand temperature was discharged at 70 to 80 ° C. to obtain resin-coated sand. This resin-coated sand was evaluated according to the evaluation method described above.

Example 5 2.3 parts by weight of the novolac type phenol resin was added,
0.1 parts by weight of dicyclohexyl phthalate is added,
Petroleum resin (melt viscosity 36 poise, compatibility 0%) 0.1
Resin-coated sand was produced and evaluated in the same manner as in Example 4 except that the parts by weight were used.

Comparative Example 1 A resin-coated sand was produced in the same manner as in Example 1 except that the content of paratoluenesulfonamide was 0% by weight and the content of coumarone-indene resin was 0% by weight. evaluated.

Comparative Example 2 A silane coupling agent (Nippon Unicar Co., Ltd.) was added to 100 parts by weight of a novolac type phenol resin (Sphenol NK-8000 manufactured by Nippon Steel Chemical Co., Ltd.) having a softening point of 86 ° C.
(A-1100 manufactured by Kao Corporation) and 3 parts by weight of ethylenebis stearamide (EBS powder manufactured by Kao Corporation)
It was solidified after being melt mixed at 50 ° C. A resin-coated sand was produced and evaluated in the same manner as in Example 1 except that p-toluenesulfonamide and coumarone-indene resin were not blended.

Comparative Example 3 A resin-coated sand was produced and evaluated in the same manner as in Example 1 except that the content of paratoluenesulfonamide was 30% by weight and the content of coumarone-indene resin was 30% by weight. did.

Comparative Example 4 Instead of paratoluenesulfonamide, tricresyl phosphate (liquid at room temperature) was added to make tricresyl phosphate content 5% by weight, and petroleum resin (melt viscosity 36 poise,
The resin-coated sand was evaluated in the same manner as in Example 1 except that the content of compatibility 0%) was 5% by weight.

Comparative Example 5 The procedure of Example 1 was repeated except that the content of paratoluenesulfonamide was 10% by weight and the content of petroleum resin (melt viscosity 26 poise, compatibility 100%) was 5% by weight. , Resin-coated sand was manufactured and evaluated.

Table 1 shows the evaluation results of Examples 1 to 5 and Comparative Examples 1 to 5.

[0037]

[Table 1]

[0038]

By using the resin-coated sand of the present invention, the mechanical strength of the molded product can be significantly improved at a significant level, and at the time of molding, excellent releasability is exhibited.
It can contribute to high performance of molded products, reduction of defective rate, and cost reduction.

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Claims (2)

[Claims] 1. A phenol resin containing 1 to 20% by weight of one or more plasticizers selected from paratoluene sulfonamide, dicyclohexyl phthalate and triphenyl phosphate, and a melt viscosity at 150 ° C. of 10%.
A resin characterized by coating sand with a phenolic resin-based binder prepared by blending 1 to 20% by weight of a thermoplastic resin having a compatibility with a phenolic resin at 150 ° C. of less than 0 poise and 20% or less. Coated sand. 2. 0.02 to 1 to 10 parts by weight of a phenol resin and 100 to 1 part by weight of sand, and one to two or more plasticizers selected from paratoluenesulfonamide, dicyclohexyl phthalate and triphenyl phosphate.
When the melt viscosity at 150 parts by weight and the weight part is less than 100 poise, the compatibility with the phenol resin at 150 ° C. is 20.
% Of a thermoplastic resin is blended with 0.02 to 1 part by weight of a thermoplastic resin, and the resin-coated sand is melt-coated with a phenol resin-based binder.