JPS63230761A - 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 a dihydric phenol. CONSTITUTION:A phenolic resin binder is obtd. by blending a novolak phenolic resin (A) obtd. by condensing 1mol. 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, salicylic acid, adipic acid, succinic acid and phthalic acid and a dihydric phenol (C) selected from among catechol, resorcinol and hydroquinone. The binder allows curing time to be greatly shortened as compared with conventional agents. Further, the agent scarcely causes lowering of its softening point and does not causes 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 novolak resins), and -M is hexamethylenetetramine (hereinafter referred to as novolac resin). (Hexa) is widely used.

Although the composition obtained by blending hexa into a novolac resin has a short curing time and is sufficiently satisfactory, there is a strong desire in the art to further shorten the curing time in order to further improve 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 novolac resin and hexa, a fast-curing novolac resin is used that takes advantage of the fast curing speed of so-called pio-ortho-novolac 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 wt. A method of adding about 1 to about 10% by weight of resorcinol (Japanese Patent Publication No. 53-13)
No. 1229) is known.

[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 do not avoid the occurrence of other problems. Can not.

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

On the other hand, when carboxylic acid is added, the effect of shortening the curing time is small, and generally it is necessary to add 2 to 3% by weight of the novolak resin.

For this reason, the softening point of novolak resin has decreased significantly,
In the case of powdered novolac resins used in felts, grindstones, friction materials, etc., there is a problem in that the resin blocks, resulting in product defects or even unusability. Furthermore, when used as sand grains for shell molding, problems arise in that not only the resin but also the resin-coated sand grains cause blocking and sand clogging defects in the mold due to decreased fluidity of the sand grains. Further, there arises the problem that not only does it lower the softening point of the resin, but it also generates an irritating odor and worsens the working environment.

Further, in the case of resorcinol, it is necessary to add 3 to 7% by weight, and although the curing speed is improved, there are problems in that the working environment is deteriorated due to bad odor and costs are increased.

[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, they discovered that the desired objective could be achieved by combining a specific organic acid and a dihydric phenol 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 a dihydric phenol selected from catechol, resorcinol, and hydroquinone. Phenols used as raw materials for the novolac type phenolic resin used in the present invention include phenol, cresol, xylenol, 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 novolak resin. An organic acid and a dihydric phenol are dissolved in this novolac resin, and if necessary, the resultant is processed into powder or granules to obtain a fast-curing phenol resin binder.

The amount of organic acid and dihydric phenol added is not necessarily limited depending on the conditions of use, but usually phenol resin 10
0.1 to 3.0 parts by weight, preferably 0 parts by weight
．． 2 to 1.5 parts by weight is optimal. Also organic acids and 2
The most preferable method for adding the phenol is to uniformly dissolve or disperse it in the novolac resin during resin synthesis as described above, but the method is not limited to this, and it can also be added at the time of crushing or use. .

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 a dihydric phenol that are uniformly dissolved or dispersed in a novolac resin. Organic acids such as benzoic acid and salicylic acid promote the decomposition of hexa, a curing agent for novolac resins, and divalent phenols such as catechol increase the number of crosslinking reactive groups during curing of novolac resins. It acts synergistically and greatly shortens the curing time of novolak resin with a small amount added.

[Example] 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.
0.5 parts by weight of oxalic acid and 9 parts by weight under reflux.
Allow the condensation reaction to occur for 0 minutes. Then -60 to -70craH
Dehydration and concentration were performed under reduced pressure of 98 g to 170°C. Obtain the novolac resin in the section. Organic acids and divalent phenols 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.
Measurement was performed 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] Resin-coated sand grains for shell molding (hereinafter referred to as RCS) were obtained by the following method using the phenolic resin binders of Example 1.4.6 and Comparative Example 2.7, and their properties were measured. The results are shown in Table 2.

RC3 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 2.3.7 and Comparative Example 4.6 is mixed with 15 parts of hexane and 0.5 part of calcium stearate while being coarsely pulverized. 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.
It was heated and pressed at 200° C. for 5 minutes up to fflI11 to form a felt having a density of 0.06 to 0.07 g/cm 3 .

Immediately from the obtained felt 50x 150 x 10
(mm), each test piece was placed on a beam with a distance between supporting points of 10 cm, 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.

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 an oven at 40°C, 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] The phenolic resin binder of the present invention has a short gel time and a fast curing speed, as seen in the Examples. 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 RCS, it has a high melting point, is less likely to cause blocking or sand clogging defects in RCS, and has further 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% formaldehyde per mole of phenol.
A novolac type phenol resin obtained by condensation reaction of 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 catechol, resorcinol, and hydroquinone. A phenolic resin binder characterized by comprising a divalent phenol.