JPH0810896A - Resin coated sand - Google Patents

Abstract

PURPOSE:To obtain resin coated sand which imparts an excellent parting property to molded goods at the time of molding without degrading their strength by coating the sand by using a compsn. consisting of a phenolic resin and a thermoplastic resin specified in melt viscosity and compatibility with a phenolic resin. CONSTITUTION:The sand is coated by using 1 to 10 pts.wt. phenolic resin, 0.1 to 4 pts. wt. thermoplastic resin having a melt viscosity of <100 poises at 150 deg.C and <=20% compatibility with the phenolic resin per 100 pts. wt. sand. The phenolic resin includes novolak type phenolic resins and resol type phenolic resins. The thermoplastic resin includes low-molecular polystyrene, petroleum resins, cumaron-indene resins, etc., the workability at the time of taking out the molded goods obtd. in such a manner is improved by using such resin coated sand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-coated sand used for pressure molding, casting, blow molding and the like with a heating mold.

[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. . When manufacturing these, a molding method using a heating mold is widely used. In these productions, attempts have been made to improve the releasability from the mold from the viewpoints of reduction of defective rate and workability. For example, Japanese Patent Application Laid-Open No. 62-127140 proposes to add 0.5 to 5 parts by weight of ethylene bisstearic acid amide, polyethylene wax, etc. as a lubricant to 100 parts by weight of a phenol resin. In addition, a method of applying a release agent to the mold is also used. However, the method of incorporating a lubricant causes other problems such as a decrease in strength, so that the amount thereof is limited. The method of applying the release agent to the mold needs to do this frequently, which is problematic in terms of work efficiency.

To reduce thermal expansion and improve strength,
It is also possible to blend various resins such as a ketone resin and an epoxy resin with the phenol resin for the purpose of improving the heat disintegration property. JP-A-56-163055 and JP-A-58-589
No. 54, etc., these are not intended to improve releasability. Also, JP-A-57-15
No. 3044 discloses a polyisocyanate-based resin concrete, but it is not a phenol resin-based one.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resin-coated sand that gives excellent releasability during molding without deteriorating the strength properties of the molded product.

[0005]

SUMMARY OF THE INVENTION The present invention contains 1 to 50% by weight of a thermoplastic resin having a melt viscosity at 150 ° C. of less than 100 poise and a compatibility with a phenol resin at 150 ° C. of 20% or less. The resin-coated sand is obtained by coating the above-mentioned phenol resin composition with sand, and 1 to 10 parts by weight of the phenol resin and 150 ° C. per 100 parts by weight of the sand.
The resin-coated sand has a melt viscosity of less than 100 poise and a compatibility with the phenol resin at 150 ° C. of 0.1 to 4 parts by weight of a thermoplastic resin having a compatibility of 20% or less.

The sand used in the present invention is silica sand (for example,
No.3, No.4, No.6, No.7), river sand, sea sand, crushed stone (2-5)
mm), various sands such as pumice, and these can be used alone or as a mixture. Quartz sand is preferred.

The phenolic resin used in the present invention is obtained by reacting phenols such as phenol, cresol and xylenol with formaldehyde in the presence of a catalyst. Examples thereof include novolac type phenolic resins, resole type phenolic resins, phenolic resins obtained by modifying these, and mixtures of these resins. These phenolic resins are used as a solid in the presence or absence of a curing agent.

As the thermoplastic resin used in the present invention having a melt viscosity at 150 ° C. of less than 100 poise and a compatibility with the phenol resin at 150 ° C. of 20% or less, any resin can be used as long as this condition is satisfied. Can be used
Examples thereof include hydrocarbon oligomers such as low molecular weight polystyrene, petroleum resin, coumarone-indene resin, and copolymers thereof. Preferred is a thermoplastic resin which is incompatible or partially compatible (compatibility 5% or less) with the phenol resin at 150 ° C., and is a hydrocarbon-based resin oligomer having no functional group with large polarity.

The melt viscosity can be measured with a cone plate viscometer. Further, the compatibility with the phenol resin is as follows. An equal amount mixture of the phenol resin and the wax is put in a glass container and melt-mixed at 150 ° C.
After standing for 20 minutes, it can be measured by observing the phase state. That is, when one phase is transparent and one is completely compatible (100%), when three phases are partially compatible, and the volume of the intermediate phase / total volume x 100 is% compatible, and two phases are It is incompatible (0%) when it is left as it is or when it is suspended in one phase.

The blending ratio of the above thermoplastic resin to the phenol resin is 1 to 50% by weight, preferably 3 to 30% by weight of the obtained resin composition. The compounding ratio with respect to 100 parts by weight of sand is 1 to 10 parts by weight of phenol resin, 0.1 to 4 parts by weight of thermoplastic resin, preferably 0.2 to 3 parts by weight, more preferably 0.3 to 2 parts.
It is preferably part by weight. The phenol resin and the thermoplastic resin may each be of one kind or two or more kinds, but in the case of two or more kinds, the total amount is calculated. Here, when the blending amount of the thermoplastic resin is small, the releasability is not sufficiently improved, and when the blending amount is too large, poor kneading occurs or the curability during molding becomes slow.

A hardener such as hexamethylenetetramine, a lubricant such as calcium carbonate, and other additives can be added to the resin-coated sand. This resin-coated sand can be manufactured by a hot-milling method or the like. For example, sand heated in advance to 120 to 180 ° C. is put into a kneading machine (such as a wall mixer), and a predetermined amount of a phenol resin and a thermoplastic resin is added thereto, and the mixture is melted and coated. next,
If necessary, water in which hexamethylenetetramine is dissolved is added, and further air is blown, and when a sand lump collapses, an appropriate amount of a lubricant such as calcium stearate is added and then discharged to obtain a resin-coated sand.

In order to produce a molded article such as a building material by molding the resin-coated sand of the present invention, pressure molding using a heating die, casting molding, blow molding, etc. can be applied. By using, the workability in taking out the obtained molded product is improved. Therefore, the time and effort required for spraying or applying the mold release agent to the mold is greatly reduced.

[0013]

EXAMPLES Examples and comparative examples of the present invention will be shown below. The evaluation of releasability, the evaluation of strength, and the fluidity test of the resin-coated sand were performed by the following methods. (1) Evaluation of mold release property A mold having flat surfaces was set on the upper and lower plates of a pressure molding machine heated to 250 ° C., and a predetermined amount of a fluorine-based mold release agent was sprayed onto the mold surface, 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 releasability from the upper and lower surfaces of the mold is observed. By repeating this, only by first spraying the release agent, the number of times of continuous molding can be obtained and evaluated. The measurement is limited to 30 times.

(2) Evaluation of strength 20 kg of resin-coated sand was poured into a heating mold of 250 ° C.
/ Cm ² , hold for 2 minutes, then immediately remove the mold, 1
Three test pieces of 50 × 20 × 22.5 mm are prepared. After cooling this to room temperature and measuring the density, the bending strength is measured at a load speed of 20 mm / min and a span of 100 mm.

(3) Fluidity test A powder tester manufactured by Hosokawa Micron Co., Ltd. is used to measure the angle of repose, the coarse packing bulk density, and the dense packing bulk density of the resin-coated sand.

Example 1 Quartz sand (Fratari Sand 6)
No.) 100 parts by weight is heated to 160 ° C. in advance and put in a Shinagawa tabletop mixer, and 2 parts by weight of a novolac type phenol resin (Sphenol NK8000 manufactured by Nippon Steel Chemical Co., Ltd.) having a softening point of 86 ° C. , A thermoplastic resin having a melt viscosity of 12 poises at 150 ° C. and a compatibility of 5% with a novolac type phenolic resin at 150 ° C. as a coumarone-indene resin (Nippon Steel Chemical Co., Ltd.
(N-100S) 0.5 part by weight is added and mixed with silica sand and melted for 60 seconds. Subsequently, hexa-methylenetetramine (0.3 parts by weight) was dissolved in water (1.5 parts by weight), and hexa-water was added. After 15 seconds, air was blown from the blower, and when the sand lump collapsed, the air blow was stopped. Then, 0.05 part by weight of calcium stearate is added as a lubricant. 30
After a second, the sand was discharged at a sand temperature of 70 to 80 ° C. to obtain resin-coated sand.

Example 2 As a thermoplastic resin, 150
C ₅ petroleum resin having a melt viscosity at 36 ° C. of 36 poise and a compatibility with the novolak type phenolic resin at 150 ° C. of 0% (Mitsui Petrochemical Co., Ltd.
(00) was added and the resin-coated sand was produced and evaluated in the same manner as in Example 1 except that 0.5 part by weight was added.

[Example 3] As a thermoplastic resin, 150
Low molecular weight polystyrene having a melt viscosity at 24 ° C of 24 poise and a compatibility with novolac type phenolic resin at 150 ° C of 0% (Haimer ST9 manufactured by Sanyo Kasei Co., Ltd.
Resin-coated sand was produced and evaluated in the same manner as in Example 1 except that 0.5 part by weight of 5) was added.

[Example 4] The addition amount of phenol resin was 2.375 parts by weight, hexamine was 0.356 parts by weight, and a coumarone-indene resin (Nippon Steel Chemical Co., Ltd. Escron N-100S) was used as a thermoplastic resin. A resin-coated sand was produced and evaluated in the same manner as in Example 1 except that the addition amount of was 0.125 parts by weight.

[Example 5] 1.5 parts by weight of a phenol resin, 0.225 parts by weight of hexamine, and a coumarone-indene resin (Nippon Steel Escron N-100S) as a thermoplastic resin. The addition amount of 1.
Resin-coated sand was produced and evaluated in the same manner as in Example 1 except that the amount was 0 part by weight.

Comparative Example 1 A resin-coated sand was produced in the same manner as in Example 1 except that the amount of the phenol resin added was 2.5 parts by weight, the hexamine was 0.375 parts by weight, and no thermoplastic resin was added. And evaluated.

[Comparative Example 2] A resin was prepared in the same manner as in Example 1 except that a coumarone-indene resin (ESCLON N-100S manufactured by Nippon Steel Chemical Co., Ltd.) was added as the thermoplastic resin in an amount of 6 parts by weight. Although coated sand was produced, the lump of sand was difficult to collapse, and lumps were observed, so that physical properties could not be measured.

[Comparative Example 3] As a thermoplastic resin, 150
0.5 parts by weight of a polystyrene resin (Esstyrene G-15L manufactured by Nippon Steel Chemical Co., Ltd.) having a melt viscosity at 1000 ° C. or higher (unmelted state) and a compatibility with novolac type phenolic resin at 150 ° C. of 0%. A resin-coated sand was produced and evaluated in the same manner as in Example 1 except that it was attached.

[Comparative Example 4] As a thermoplastic resin, 150
Petroleum resin having a melt viscosity at 26 ° C of 26 poise and a compatibility with the novolac type phenolic resin at 150 ° C is 100% (Nippon Zeon Co., Ltd., Quinton QTN-15).
(00) was added and the resin-coated sand was produced and evaluated in the same manner as in Example 1 except that 0.5 part by weight was added.

[Comparative Example 5] The amount of phenolic resin added was 2.375 parts by weight and hexamine was 0.356 parts by weight. Carnauba wax (a conventional release agent was used instead of the thermoplastic resin). A resin-coated sand was produced in the same manner as in Example 1 except that 0.125 parts by weight of a melt viscosity at 150 ° C. of 0.1 poise or less and a compatibility with a novolak type phenolic resin at 150 ° C. of 0%) was added and evaluated. did.

Table 1 shows the results of evaluation of releasability, strength and fluidity of Examples 1-5 and Comparative Examples 1-5. In Table 1, ∘ indicates that the upper and lower surfaces have sufficient releasability, Δ indicates that one surface has a slight releasability, and x indicates that the releasability is poor. The number of mold releasability (times) is the number of times of molding from the beginning, and indicates the final number of times of molding when the evaluation of ◯, Δ or × was obtained. Usually, the order changes in the order of ○, △, ×. The measurement is terminated when x continues twice.

[0027]

[Table 1]

[0028]

According to the present invention, the mold releasability of a molded article is remarkably improved without spraying or coating the mold with a mold releasing agent.
Moreover, since the effect is continued, workability is improved. In addition, since the stain on the mold is extremely reduced, the number of steps for polishing the mold is reduced, and the mold maintenance is facilitated. Furthermore,
There is an effect that the appearance of the molded product is good and the occurrence of defective rate is significantly reduced without lowering the strength and physical properties of the molded product.

Claims (2)

[Claims] 1. A phenolic resin composition containing a thermoplastic resin having a melt viscosity at 150 ° C. of less than 100 poise and a compatibility with the phenolic resin at 150 ° C. of 20% or less. Resin coated sand made by coating sand with. 2. 100 parts by weight of sand, 1 to 10 parts by weight of a phenolic resin, and a melt viscosity at 150 ° C. of 100.
Resin-coated sand obtained by melt-coating 0.1 to 4 parts by weight of a thermoplastic resin having a compatibility with a phenolic resin at 150 ° C of 20% or less at a poise.