JPS63230760A - Phenolic resin binder - Google Patents

Abstract

PURPOSE:To provide the title binder which allows curing time to be greatly shortened, scarcely causes lowering of its softening point and is suitable for use in bonding molds, felt, grinding stones, etc. to substrates, by blending a novolak phenolic resin with a specific org. acid and an amino compd. CONSTITUTION:A phenolic resin binder is obtd. by blending a novolak phenolic resin (A) obtd. by condensing one mol. of a phenol (e.g., phenol) with 0.50-0.95mol. of formaldehyde (e.g., formalin) in the presence of an acid catalyst (e.g., oxalic acid) with an org. acid (B) selected from among benzoic acid, salicyl ic acid, adipic acid, succinic acid and phthalic acid and an amino compd. (C) selected from among aminophenols, urea, nitroaniline and melamine. The binder allows curing time to be greatly shortened as compared with conventional agents. Further, the binder scarcely causes lowering of its softening point and does not cause blocking.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a fast-curing novolak type phenolic resin binder, and more specifically to silica sand, fibers, and abrasives in molds, felts, grindstones, friction materials, etc. The present invention relates to fast-curing novolak-type phenolic resin binders for bonding organic and inorganic substrates such as particles.

[Prior Art] Traditionally, formaldehyde sources such as hexamethylenetetramine, paraformaldehyde, and trioxane have been used as curing agents for novolak-type phenolic resins (hereinafter referred to as novolac resins), and generally hexamethylenetetramine (hereinafter referred to as novolac resins) has been used as a curing agent. Hexa) is widely used.

Although the curing time of the composition obtained by blending hexa into novolak resin is quite satisfactory, there is a strong desire in the industry to further shorten the curing time in order to further improve the workability. . Various attempts have been made in the past to shorten the curing time and obtain fast-curing novolak resin binders.

For example, in the reaction between novolak resin and hexa, a fast-curing novolac resin is used that takes advantage of the fast curing speed of so-called high-ortho novolak resin, which has many methylene bridges bonded to ortho-ortho positions with respect to phenolic hydroxyl groups. Method for obtaining a binder (Japanese Patent Publication No. 53-35596
No., JP-A-54-127997, JP-A-59-804
No. 18) is known.

Another method is to add aromatic carboxylic acids such as salicylic acid to novolac resin and hexa (Japanese Patent Publication No. 36
-20589, Japanese Patent Publication No. 60-31340), a method of adding 0.5 to 5% by weight of aliphatic saturated dicarboxylic acid to novolak resin (Japanese Patent Application Laid-open No. 124118-1982)
Also known is a method of adding a urea compound such as urea, ethylene urea, propylene urea, etc. in an amount of about 1 to about 5% by weight based on the novolac resin (Japanese Patent Publication No. 26562/1983).

[Problems to be Solved by the Invention] However, although the conventionally known methods of shortening the curing time can shorten the curing time of novolac resins, they cannot avoid other problems. Can not.

For example, in the case of pyortho-novolac resin, it is difficult to control the synthesis method, there is a risk of gelation, it is difficult to obtain a novolac resin of stable quality, and there are also problems in terms of cost due to poor yield.

On the other hand, when a carboxylic acid or urea compound is added, the effect of shortening the curing time is small, and generally it is necessary to add 2 to 3% by weight based on the novolac resin. As a result, the softening point of novolac resin decreases significantly, and in the case of powdered novolac resin used for felt, grindstones, friction materials, etc., this can cause resin blocks, resulting in product defects and even worse. The problem is that it becomes unusable. Furthermore, when used as sand grains for shell molding, problems arise in that not only the resin but also the resin coating and the sand grains cause blocking, and sand clogging in the mold occurs due to a decrease in the fluidity of the sand grains. Further, in the case of carboxylic acid, there is a problem in that it not only lowers the softening point of the resin, but also generates a pungent odor, which worsens the working environment.

[Means for Solving the Problems] The present inventor has developed a novolac resin binder which has a significantly shorter curing time than conventional fast-curing novolac resin binders and which does not suffer from the above-mentioned problems. I have been doing as much research as possible. As a result, the inventors discovered that the desired objective could be achieved by combining a specific organic acid and an amino compound with a novolak resin, leading to the completion of the present invention.

That is, the present invention uses a novolac type phenol resin obtained by condensing 0.50 to 0.95 mole of formaldehyde per mole of phenol under an acidic catalyst, and benzoic acid, satylylic acid, adipic acid, and succinic acid. and an organic acid selected from phthalic acid and an amino compound selected from aminophenol, urea, nitroaniline and melamine.

Phenols used as raw materials for the novolac type phenolic resin used in the present invention include phenol, cresol, xylenol, dioxybenzene, bisphenol A, etc., singly or in combination.

As formaldehydes, formalin, paraformaldehyde, etc. are used.

As the acidic catalyst, inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, or organic acids such as acetic acid, oxalic acid, and p-toluenesulfonic acid may be used alone or in mixtures.

Next, the phenolic resin binder of the present invention is produced, for example, as follows.

0.5% formalin per 1 mole of phenol
~0.95 mol is subjected to a condensation reaction under reflux for a predetermined time under an acidic catalyst (preferably hydrochloric acid or oxalic acid). After that, concentrate and dehydrate under reduced pressure to about 150-190℃,
Obtain novolac resin. An organic acid and an amino compound are dissolved in this novolac resin and processed into powder or granules as required to obtain a fast-curing phenolic resin binder.

The amount of the organic acid and amino compound added is not absolutely limited depending on the conditions of use, but is usually 0.1 to 3.0 parts by weight, preferably 0.2 parts by weight, per 100 parts by weight of the phenol resin.
~1.5 parts by weight is optimal.

The most preferable method for adding organic acids and amino compounds is to uniformly dissolve or disperse them in the novolac resin during resin synthesis, as described above, but the method is not limited to this, and they may be added during pulverization or use. You can also do that.

In addition to the above, the phenolic resin binder of the present invention may optionally include lubricants such as stearic acid, stearate, paraffin, polyethylene wax, and ethylene bisstearamide, and silane coupling agents such as aminosilane and epoxysilane. can be contained.

[Function] The phenolic resin binder of the present invention contains an organic acid and an amino compound uniformly dissolved or dispersed in a novolak resin. Organic acids such as benzoic acid and salicylic acid promote the decomposition of hexa, which is a curing agent for novolak resin, and amino compounds such as aminophenol increase the number of crosslinking reactive groups during curing of novolac resin. It works effectively and greatly shortens the curing time of novolak resin with a small amount added.

[Examples] Examples of the present invention will be shown below, but the present invention is not limited thereto.

[Examples 1 to 7 and Comparative Examples 1 to 7] Phenonicol 10
0 parts by weight, 59 parts by weight of 37% formalin were placed in a reaction vessel equipped with a thermometer and condenser, and 0.5 parts by weight of oxalic acid was added.
Parts by weight are added and the condensation reaction is carried out under reflux for 90 minutes. Then, dehydration and concentration were performed at 170°C under a reduced pressure of -60 to -70 cmHH.
98 parts by weight of novolak resin was obtained. The organic acids and amino compounds shown in Table 1 were dissolved in 100 parts by weight of this novolac resin to obtain a phenol resin binder.

These phenolic resin binders were pulverized and their gel time and softening point were measured.

The results are also shown in Table 1. Gel time is made by mixing 15 parts by weight of Hexa with 100 parts by weight of phenolic resin.
It was measured on a hot plate at 150°C in accordance with JIS K-6910. The softening point was measured according to JIS K-6910.

Next, an application example of the present invention will be shown.

[Application Example 1] Using the phenolic resin binders of Example 2.5.7 and Comparative Example 2.7, resin-coated sand grains for shell molding (hereinafter referred to as RCS) were obtained by the following method, and their properties were measured. The results are shown in Table 2.

RC5 is a speed mixer (manufactured by Enshu Tekko, N5C-2
8 kg of Fuca sand heated to 160°C was put into a mold), the above phenolic resin binder was added at 160°C and kneaded for 30 seconds, then an aqueous solution of 24 g of hexa dissolved in 120 g of water was added and stirred until the sand grains collapsed. After that, 8 g of calcium stearate was added, and the mixture was further stirred for 20 seconds, and the sand was removed to obtain RC3.

(Left below) (Application example 2) 100 parts of the phenolic resin binder of Example 1.4.6 and Comparative example 4.5 is mixed with 15 parts of hexane and 0.5 part of calcium stearate while coarsely pulverizing. This was further finely pulverized to obtain a felt binder as a fine powder with an average particle size of 8 μm.

25 parts of felt binder and 100 parts of cotton fiber obtained above
260x240x80 (mm)
, make a piece of fleece weighing 45-50g and roll it to a thickness of 10g.
Heat pressed at 200℃ for 5 minutes to a density of 0.06 mm.
~0.07 g/cm3 felt was molded. Immediately from the obtained felt, 50 x 150 x 10 (
Three test pieces of mm) were cut out, each test piece was placed on a beam with a distance between supporting points of 10 cn+, a load of 100 g was applied to the center, and the amount of deflection was measured after 10 seconds. The smaller the amount of deflection, the better the curability. Further, after cooling the same test piece as above to room temperature, the tensile strength was measured using a Tensilon type tensile tester. The results are shown in Table 3.

To determine the blocking property of the felt binder, 25 g of the felt binder is placed in a cylindrical container with a diameter of 50 mm and a load of 1 kg is applied. This was placed in a 40 ton oven, and after 72 hours it was taken out on a 24 mesh sieve, the weight of the felt binder remaining on the sieve was measured, and the block rate was expressed as a percentage. The results are shown in Table 3.

Table 3 [Effects of the Invention] As seen in the examples, the phenolic resin binder of the present invention has a short gel time and a fast curing speed. Furthermore, the phenol resin binder has a low softening point and is less likely to cause blocking.

Furthermore, as is clear from the results of the application examples, when the phenolic resin binder of the present invention is applied to RC8, it is difficult to cause blocking or sand clogging defects when the welding point is high < RC3, and it also has a high warm bending strength. It has the advantage of improving the productivity of mold making because of its high value.

Furthermore, when applied to felt, the block rate is small and the amount of deflection is small, indicating that the curing property is good.

As described above, the phenolic resin binder of the present invention is excellent in that the curing time is significantly shortened compared to conventional binders, and furthermore, the softening point does not significantly decrease and there are no blocks.

Patent applicant: Aisin Kako Co., Ltd. Representative: Haruo Miyaji

Claims (1)

[Claims] 0.0% of formaldehyde per mole of phenols.
A novolac type phenol resin obtained by condensing 50 to 0.95 mol under an acidic catalyst, an organic acid selected from benzoic acid, salicylic acid, adipic acid, succinic acid, and phthalic acid, and aminophenol, urea, and nitroaniline. and an amino compound selected from melamine.