JP2010095555A - Novolak type phenolic resin composition for resinoid grinding wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novolak type phenolic resin and composition, useful especially for precision grinding wheel use, and capable of obtaining a resinoid grinding wheel that retains a modulus of elasticity low without lowering strength of the grinding wheel and has excellent grinding performance. <P>SOLUTION: The novolak type phenolic resin composition for a resinoid grinding wheel contains a novolak type phenolic resin and an acrylic polymer, wherein the content of the acrylic polymer is 1-25% based on the total novolak type phenolic resin composition, and preferably the resin composition further contains hexamethylenetetramine. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a novolac type phenolic resin composition used as a binder for resinoid grinding wheels.

Resinoid grindstone is a mixture of abrasive grains, a solvent called wetter and a liquid resol type phenol resin, a filler that becomes a grinding aid such as cryolite and iron sulfide, and a powdery phenol resin composition To produce a coated grain, which is molded by a press molding apparatus such as a cold press, semi-hot press, hot press or the like, and the resulting molded product is fired by a drying apparatus having a maximum temperature of 130 to 230 ° C. Manufactured. Here, the phenol resin composition is used as a binder for a resinoid grindstone together with a wetter (see, for example, Patent Document 1).

As said powdery phenol resin composition, what mixed the novolak-type phenol resin and the hexamethylenetetramine as a hardening | curing agent is used normally. As a novolak type phenol resin, the weight average molecular weight is 1000 to 15000, the dispersion degree is 3 to 10, the content of unreacted phenol is 0.1 to 10% by weight, and the content of the binuclear component is 7 to 20%. % Is often used.

Efforts to improve the grinding performance by improving the strength of resinoid grinding wheels have been made since the past.
For example, it is generally known that the strength of the grindstone is improved by lowering the molecular weight of the phenol resin used to increase the flowability.
An example of increasing the ratio of formaldehyde to phenols, that is, the molar ratio is known. For example, a phenolic resin with a low monomer or dimer content by reacting a phenolic compound with a dibenzylic ether type phenolic resin obtained by reacting at a molar ratio of 1.5 or more is also applicable to such applications. it can.

Among the resinoid grindstones, for grinding wheels for precision grinding, vibration of the grindstone becomes a problem at the time of rotational polishing, and in order to improve grindability, it is necessary to reduce the elasticity of the binder resin. However, if the strength of the grindstone is increased as described above, the elastic modulus increases, so that there is a problem that the grindstone bounces and scratches due to abrasive grains occur on the surface to be ground, or the grinding efficiency deteriorates. Low elasticity has been difficult to achieve.

Japanese Patent Laid-Open No. 08-081531

The present invention has been made as a result of studies to solve various problems that have been a problem with conventional powdered novolak type phenolic resins for grindstones, and is particularly useful in precision grindstone applications and reduces the strength of the grindstone. Therefore, the present invention provides a novolac type phenolic resin and a composition capable of obtaining a resinoid grindstone having a low elastic modulus and excellent grinding performance.

Such an object is achieved by the following present inventions (1) to (3).
(1) A novolac type phenolic resin composition for a resinoid grindstone, comprising a novolac type phenolic resin and an acrylic polymer.
(2) The novolak-type phenol resin composition for a resinoid grindstone according to (1), wherein the content of the acrylic polymer is 1 to 25% with respect to the entire novolak-type phenol resin composition.
(3) The novolak-type phenolic resin composition for a resinoid grindstone according to (1) or (2) above, wherein the resin composition further contains hexamethylenetetramine.

The present invention provides a novolac-type phenolic resin and a composition that can obtain a resinoid grindstone that maintains a low elastic modulus and has excellent grinding performance without reducing the strength of the grindstone.

Below, the novolak-type phenol resin and composition for resinoid grindstones of this invention are demonstrated.
The novolac type phenolic resin for resinoid grinding wheels of the present invention (hereinafter sometimes simply referred to as “phenolic resin”) has an unreacted phenol content of 1 wt% or less and a dinuclear component content of 5 wt% or less. It is characterized by being.
Moreover, the composition of this invention contains the said novolak-type phenol resin and hexamethylenetetramine, It is characterized by the above-mentioned.
First, the phenol resin of the present invention will be described.

The phenols used in the phenolic resin of the present invention are not particularly limited. For example, phenol, orthocresol, metacresol, paracresol, xylenol, paratertiary butylphenol, paraoctylphenol, paraphenylphenol, bisphenol A, bisphenol F, resorcin, etc. And at least one phenol selected from these phenols, and phenol and cresol are usually used in many cases.

Aldehydes used in the phenolic resin of the present invention are not particularly limited. For example, formaldehyde, acetaldehyde, butyraldehyde, acrolein, or the like, or a mixture thereof, a substance that generates these aldehydes, or a solution of these aldehydes It is also possible to use at least one aldehyde selected from these aldehydes, but usually formaldehyde is often used.

Formaldehyde is not particularly limited here, but is preferably an aqueous formaldehyde solution, paraformaldehyde or the like, or a mixture thereof, and it is also possible to use substances that generate these formaldehydes or solutions of these formaldehydes.
Next, as an acidic substance that serves as a catalyst for the novolak-type phenol resin, for example, organic acids such as oxalic acid, mineral acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, paratoluenesulfonic acid, paraphenolsulfonic acid, and the like can be used. it can. Moreover, these can be used individually or in combination of 2 or more types.

When synthesizing the phenol resin of the present invention, the charged molar ratio (F / P) of the phenols (P) and the aldehydes (F) is not particularly limited, but may be 0.3 to 3.0. Preferably, it is 0.5-2.0. If the molar ratio is smaller than the above lower limit value, the reaction may not be sufficiently performed and a large amount of unreacted phenols may remain, or the yield of phenol resin may decrease. Depending on the conditions, the reaction may proceed too much and gel may occur.

The method for reacting the phenols with the aldehydes is not particularly limited, but at the start of the reaction, the phenols and aldehydes may be charged all at once, and the catalyst may be reacted. In order to suppress this, the aldehydes may be sequentially added and reacted after mixing the phenols and the catalyst.

In the above reaction, it is possible to use an antifoaming agent, a surfactant or the like for stabilizing the reaction. Moreover, it is also possible to use organic solvents, such as methanol and acetone.
After completion of the above reaction, for catalyst removal, phase separation can be used to remove by stationary separation, a centrifugal separator or the like, or neutralization or washing with water. At that time, if necessary, water or an organic solvent can be added. Since water containing an organic phosphonic acid or an aqueous phosphoric acid solution is easily phase-separated, it can be removed relatively easily by stationary separation, a centrifugal separator or the like, and may be reused after removal. Neutralization can use organic and inorganic alkaline substances such as sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonia, triethylamine and the like. By these removal steps, it is desirable to set the pH of the reaction product to 2 to 12 so that the unreacted phenols are not removed or decomposed by heat during the removal of the unreacted phenols.

The content of unreacted phenols in the novolak type phenolic resin used in the present invention is preferably 5.0% by weight or less, more preferably 1.0% by weight or less, based on the entire novolak type phenolic resin. . By doing so, it is possible to reduce odor during resin processing due to unreacted phenol, to improve the working environment, and to maintain good physical properties.

The molecular weight of the phenolic resin of the present invention is not particularly limited. In consideration of workability when producing coated grains, and preservability and curability of the coated grains, the softening point is more important than the molecular weight of the resin in the present invention. The softening point of the resin is preferably 70 to 150 ° C, more preferably 90 to 140 ° C. When the softening point is lower than the lower limit, problems such as blocking of the powdered resin or coated grain may occur. If the softening point exceeds the above upper limit, it may be higher than the decomposition temperature of hexamethylenetetramine, which is a curing agent.

Next, the composition of the present invention will be described. The composition of the present invention contains the phenol resin, thermoplastic resin and hexamethylenetetramine described above.

The addition amount of the acrylic polymer used for this invention is 1-25 weight% with respect to the whole novolak-type phenol resin.
Although it does not specifically limit as a hardening | curing agent, Hexamethylenetetramine is preferable from the surface of sclerosis | hardenability or heat resistance. Although it does not specifically limit as content, It is preferable that it is 3-20 weight% with respect to the whole composition. Thereby, when it uses for the use of this invention, hardening is uniform and it can be set as a moderate crosslinking density.

In addition, the composition of the present invention includes thermoplastic resins such as polyamide and polyvinyl butyral, thermosetting resins such as epoxy resins, or acidic or alkaline organic or inorganic substances, organic fillers, inorganic fillers, etc. Can also be added as appropriate. When these additives are used, the timing of addition is not particularly limited, and may be any time during production of the composition or during production of the resinoid grindstone.

The method for producing the composition of the present invention is not particularly limited. It can obtain by grind | pulverizing using the grinder of this and making it into powder form. The particle size of the composition after pulverization is not particularly limited, but it is preferable that the average particle size is 5 to 50 μm.

Hereinafter, the present invention will be described in detail with reference to examples. “Parts” and “%” described here all indicate “parts by weight” and “% by weight”.

Example 1
While adding 1000 parts of phenol and 10 parts of oxalic acid to a 3 L three-necked flask, the temperature was raised to 100 ° C., 690 parts of a 37% formaldehyde aqueous solution was sequentially added over 30 minutes, and then refluxed at 100 ° C. for 1 hour. Reacted. Thereafter, atmospheric distillation was carried out, the temperature was raised to 130 ° C., vacuum distillation was performed under a reduced pressure of 5000 Pa, the temperature was raised to 190 ° C., and then the temperature was increased to 170 ° C. Acrylic polymer UP-1000 (manufactured by Toa Gosei Co., Ltd.) And 1415 parts of a novolac type phenol resin obtained by adding and mixing 315 parts. To the obtained resin, 157 parts of hexamethylenetetramine was added and pulverized using an impact pulverizer to obtain 1572 parts of a powdery phenol resin composition A.

(Example 2)
Grinding was carried out in the same manner as described above except that acrylic polymer UME-1001 (manufactured by Soken Chemical Co., Ltd.) was used instead of acrylic polymer UP-1000 of Example 1, to obtain 1572 parts of powdered phenol resin B.
(Example 3)
Grinding was carried out in the same manner as described above except that acrylic polymer UMB-1003 (manufactured by Soken Chemical Co., Ltd.) was used instead of acrylic polymer UP-1000 of Example 1, to obtain 1572 parts of powdered phenol resin C.
(Comparative Example 1)
122 parts of hexamethylenetetramine was added to 1100 parts of the novolak-type phenol resin obtained without adding the acrylic polymer UP-1000 of Example 1, and the powdered phenol resin composition D was pulverized using an impact pulverizer. 1222 parts were obtained.

Table 1 shows the characteristics of the powdery phenol resins A, B, C, and D obtained in Examples 1, 2, and 3 and Comparative Example 1.
(Measuring method)
Melting point, gelation time, flow: determined in accordance with JIS K6910.

(Whetstone test piece production example)
Alumina abrasive, 1000 parts of Sacradund A # 60 (Nippon Carlit Co., Ltd.) and 10 parts of wet phenolic phenol resin PR-940 (Sumitomo Bakelite Co., Ltd.) using a Shinagawa kneader for 5 minutes Kneading was performed, 150 parts of the powdered phenol resin composition was added, and kneading was further performed for 5 minutes to produce a coated grain. The condition of the coated grains was confirmed immediately after kneading and after storage for 12 hours under the conditions of 25 ° C. and 60% relative humidity. Thereafter, the coated grains were put into a mold so as to have a size of 100 mm × 25 mm × 15 mm and a bulk specific gravity of 2.0, followed by press molding, and the molded product was placed on a stainless steel plate. This is put in a hot-air circulating dryer with a program function, held at room temperature to 100 ° C. for 5 hours, held at 100 ° C. for 5 hours, held at 100 ° C. to 180 ° C. for 10 hours, held at 180 ° C. for 10 hours, then 10 Curing was carried out using a program for cooling to room temperature over time to produce a grindstone specimen.

Using the powdery phenol resin compositions A, B, C, and D obtained in Examples 1, 2, and 3 and Comparative Example 1, a grindstone test piece was prepared according to the grindstone test piece production example. The grindstone piece was subjected to a three-point bending strength test at temperatures of 25 ° C. and 250 ° C. in accordance with JIS K 6910. The results are shown in Table 2.

Compared to Comparative Example 1, the phenolic resins obtained in Examples 1 and 2 were superior in bending strength to the grindstone test pieces formed with coated grains.

The grindstone formed using the phenolic resin for resinoid grindstones of the present invention has good workability when producing the grindstone. Moreover, since the strength of the grindstone is high, it has excellent grinding performance and can be suitably used for a resinoid grindstone.

Claims (3)

A novolac type phenol resin composition for a resinoid grindstone, comprising a novolac type phenol resin and an acrylic polymer. The novolak-type phenol resin composition for a resinoid grindstone according to claim 1, wherein the content of the acrylic polymer is 1 to 25% by weight with respect to the entire novolak-type phenol resin composition. The novolak-type phenol resin composition for resinoid grinding wheels according to claim 1 or 2, wherein the resin composition further contains hexamethylenetetramine.