JP2003292645A - Prepreg and whetstone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg which extremely reduces volatile components, simultaneously neither loses flexibility nor adhere in producing the prepreg with the use of a resol resin to be used. <P>SOLUTION: The prepreg is obtained by impregnating a fibrous base material with (A) a solution containing (II) a resol resin to be obtained by reacting (I) a novolak resin obtained by reacting an aldehyde with a phenol at a ratio (molar ratio) of the aldehyde to the phenol of 0.3-0.6 with an aldehyde or coating the solution (A) on the fibrous material, and then drying the resulting product, and a whetstone is reinforced with a prepreg obtained by subjecting this prepreg to heat molding. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg suitable for reinforcing a grinding wheel, and relates to a prepreg in which a free monomer of a phenol resin to be impregnated or applied is reduced and a volatile content (VC) is reduced. It also relates to a grinding wheel manufactured using this prepreg.

[0002]

2. Description of the Related Art Grinding wheel reinforcing glass cloth, glass roving and the like are usually used as a prepreg obtained by impregnating or coating a phenol resin, which is a component similar to the binder used in the grinding wheel, and drying. The phenol resin used for this purpose is impregnated with a resol resin, or a mixture of the resole resin and the novolac resin in an appropriate ratio and dissolved in a solvent (methanol). The impregnated prepreg is punched by a punching machine according to the shape of the grinding wheel, and then stored in a stacked state before being used for actual use. The phenolic resin used for this purpose is usually used by adjusting the molecular weight or changing the ratio of the resole resin and the novolac resin in order to prevent the adhesion of the prepreg and maintain appropriate flexibility. .

[0003]

However, in recent years, from the viewpoint of environmental protection, it has been required to reduce the volatile content of the phenol resin used as much as possible. Furthermore, it is required to prevent adhesion between prepregs during storage while maintaining flexibility.

An object of the present invention is to provide a prepreg which uses the resole resin to be used, in which volatile components are greatly reduced during the production of the prepreg, the flexibility is not lost, and the prepreg does not adhere.

[0005]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems, and as a result, in producing a resole resin, a free phenol content as a raw material and a specific novolac resin having a controlled molecular weight were used as phenols. By combining the unreacted monomer and the resole resin in which the methylol group has been added to the mononuclear body of phenol by using it instead of the monomer and by reacting it with aldehydes, and the novolak resin from which the free monomer has been removed The inventors have found that it is possible to achieve the problems required for prepregs, and have completed the present invention.

Further, in the present invention, aldehydes and phenol are [aldehydes] / [phenols] = 0.3-
A solution (A) containing a resole resin (II) obtained by reacting a novolak resin (I) obtained by reacting with a ratio of 0.6 [molar ratio] is used as a fibrous base material. Provided is a prepreg characterized by being dried after being impregnated or applied, and a whetstone obtained by molding and curing the prepreg.

Further, the present invention further comprises mixing the novolak resin (III) and impregnating or coating the fibrous base material,
A prepreg formed by drying is also molded and cured to provide a whetstone.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The prepreg of the present invention is obtained by reacting an aldehyde and a phenol at a ratio of [aldehydes] / [phenols] = 0.3 to 0.6 [molar ratio]. It is obtained by impregnating or coating a fibrous base material with a resol resin (II) obtained by reacting a novolak resin (I) with an aldehyde and then drying it.

The method for producing the resole resin (II) is as follows:
In this method, the novolak resin (I) is reacted with an aldehyde in the presence of a catalyst. The novolak resin (I) is obtained by reacting phenols with aldehydes. At the time of the reaction, it is essential to react the aldehydes and the phenol within the above range, and a preferable molecular weight range is a number average molecular weight of 300 to 1000 (GPC).
Conversion).

The novolac resin (I) can be produced, for example, by the following steps.
Phenols, formaldehydes, and an acid as a catalyst are charged and reacted at 100 ° C. for 1 to 5 hours. After that, through a normal pressure dehydration step and a reduced pressure dehydration step, unreacted phenol remaining in the novolac resin is removed at a temperature of 180 to 230 ° C. to obtain the novolac resin (I). At that time, the content of the above-mentioned residual unreacted phenol monomer in the novolak resin is preferably as low as possible, and most preferably not present at all, but practically, it is preferably 1.0% by weight or less, and 0.1% by weight or less. % Or less is more preferable. Further, in order to control the above molecular weight, the reaction ratio of phenols and formaldehydes needs to be [formaldehyde] / [phenols] = 0.3 to 0.6 [molar ratio]. It is possible to manufacture even if the molar ratio is less than 0.3,
As the molar ratio decreases, the yield becomes poor and it becomes uneconomical. Further, if the molar ratio exceeds 0.6, it becomes difficult to control the molecular weight to an appropriate value for use in the prepreg application of the present invention, which is not preferable.

The method for producing the novolak resin (I) will be described in more detail. For example, the following method may be mentioned. That is, oxalic acid was added as a reaction catalyst to a mixture of phenol and a 37% by weight aqueous solution of formaldehyde, the temperature in the reaction system was set to 100 ° C., the reaction was carried out for 1 to 5 hours, and then distilled at 200 ° C. under normal pressure. The novolac resin (I) is obtained by further performing vacuum distillation until the amount of residual phenol in the novolak resin becomes 1.0% by weight or less, preferably 0.1% by weight or less.

The phenols used as the raw material are not particularly limited, and include, for example, phenol, alkylphenols such as cresol, xylenol, ethylphenol, butylphenol and octylphenol, polyhydric phenols such as resorcinol and catechol, halogens. Phenol, phenylphenol, aminophenol and the like. In addition, these phenols are not limited to one kind in use, and two or more kinds can be used in combination. Phenol is preferable in consideration of price.

As the aldehydes, formaldehyde, which is commonly used in the production of phenolic resins,
Paraformaldehyde, formaldehyde such as trioxane, acetaldehyde and the like are effective, and urotropin can also be used.

As the acids and the like used in the above reaction, various ones can be used. For example, acids such as oxalic acid, hydrochloric acid, phosphoric acid, sulfuric acid, paratoluenesulfonic acid and phenolsulfonic acid, or high ortho novolac resin can be used. Examples of the catalyst include zinc acetate and zinc octylate.

As the novolak resin (I) used in the present invention, a so-called modified novolak resin obtained by reacting phenol with, for example, an epoxy resin or a triazine in an arbitrary ratio in the process of synthesizing the novolac resin can be used. When the novolac resin modified with these is used as a raw material in the production of the resole resin, it is possible to impart water resistance and heat resistance to the resole resin produced by the method of the present invention.

The method for producing the resole resin (II) using the novolak resin (I) obtained by the above synthesis as a raw material includes, for example, the following methods.

It can be obtained by reacting the novolac resin (I) with an aldehyde using a catalyst such as an alkali metal catalyst, an oxide of an alkaline earth metal, amines, ammonia or zinc acetate. . These catalysts may be reacted in one kind or in combination of two kinds. Further, for the purpose of neutralizing the catalyst, sulfuric acid, hydrochloric acid, phosphoric acid,
You may use paratoluene sulfonic acid etc. The resol resin (II) thus obtained is preferably one which does not substantially contain a mononuclear component having 1 to 3 phenol monomers or methylol groups bonded to the phenol nucleus.

The method for producing the resole resin (II) will be described in more detail. For example, the following method may be mentioned. For example, a mixture of a novolak resin (I) and an aqueous formaldehyde solution (for example, 37% by weight) is used as a catalyst for hydroxylation. Add an aqueous solution of sodium (eg 48% by weight) and add 5
After reacting at a temperature of 0 to 80 ° C. for 1 to 5 hours, water in the reaction system is removed by vacuum dehydration and diluted with methanol, and the amount of residual phenol in the obtained resole resin is 1.0% by weight or less,
Preferably, a resol resin (II) solution of 0.1% by weight or less is obtained.

The ratio of the novolak resin (I) to the aldehyde in the production of the resole resin (II) used in the present invention is [aldehyde] / [novolak resin] as the bond molar ratio of the resin measured by C-13 NMR. ], But since unreacted novolac resin component does not remain and physical properties such as curability are good, 0.5 or more is preferable, and unreacted formaldehyde does not remain and it is environmentally preferable. It is preferably 0 or less. Further, more preferably, [aldehyde] / [novolak resin] = 0.5 to 2.5.

The amount of the alkalis or alkali metals used as the catalyst is preferably 0.01 times or more the number of moles of the novolak resin used as the raw material, from the viewpoint that the reaction proceeds smoothly, and the reaction can be easily controlled. From the standpoint of not impairing the storage stability of the product or of not impairing the physical properties such as brittleness, the molar ratio is preferably 1.0 times or less.

The prepreg of the present invention has the above-mentioned resole resin (II) as a resin component to be impregnated or applied.
In addition to the above, a resin component to which a novolac resin (III) is further added may be used.

The novolak resin (III) can be produced, for example, in the same manner as the novolak resin (I), and the residual phenol amount in the novolak resin (III) is adjusted to 0. It is preferably 2% by weight or less. Further, the molar ratio of [aldehydes] / [phenols] is preferably in the range of 0.6 to 0.9.

The resole resin (II) for producing the prepreg of the present invention is used, or the resole resin (I) is used.
The resol resin (II) obtained above may be used alone in the preparation of the impregnating (or coating) solution consisting of the mixed solution of I) and the novolac resin (III), or the resol resin (II) and Separately manufactured novolak resin (III)
It is also possible to use a mixture prepared by mixing and adjusting the ratio of 10 to 90/90 to 10 (weight ratio). In this case, although the mixing ratio depends on the required performance of the prepreg, a resole resin / novolak resin = 40 to 60/60 to 40 (solid content weight ratio) shows more preferable physical properties.

The novolac resin (III) may be added when the resol resin (II) is produced.

The solid content concentration of the resol resin (II) solution and the novolac resin (III) solution used in the present invention is not particularly limited as long as it can be impregnated or coated.
30 to 70% by weight is preferable.

The solvent of the resol resin (II) solution is preferably water or an alcohol such as methanol, and the solvent of the novolac resin (III) solution is preferably an alcohol.

The prepreg of the present invention is an impregnating (or coating) solution consisting of the resole resin (II) obtained as described above or a mixed solution of the resole resin (II) and the novolac resin (III). In the case of impregnating or applying, the resin / fibrous base material is impregnated or applied to, for example, a fibrous base material (for example, glass cloth).
Then, it is dried at 50 to 100 ° C. for 5 to 30 minutes to obtain a prepreg.

At this time, the fibrous base material is preferably dried, and the ratio of the fibrous base material and the impregnating (or coating) solution is [fibrous base material and impregnating (or coating) solution]. Solution] / [Fibrous substrate] = 20 to 60 (solid content ratio)
Is preferred.

Next, as a method for producing a cutting grindstone using the prepreg obtained as described above, for example, the prepreg is sandwiched between resin coated grains (RGC) to which a resole resin and a phenol resin are adhered, and a desired size is obtained. After molding, it is heated and cured at 150 to 200 ° C. for 5 to 10 hours to obtain the grindstone of the present invention.

[0030]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. In the examples, “part” and “%” are parts by weight and% by weight, respectively. (However, humidity represents relative humidity.) Further, the number average molecular weight indicates a molecular weight converted into polystyrene having a known molecular weight by GPC (gel permeation chromatography). Free phenol was measured by GPC when the content of free phenol was 1% by weight or more, and by gas chromatography when the content was less than 1% by weight. However, the present invention is not limited to these examples.

Synthesis Example 1 A 2-liter four-necked flask was equipped with a stirrer and a thermometer, and 941 g of phenol and 37.2% formalin 40.3
g, oxalic acid dihydrate 4.705 g was added, 100
After heating to ℃, 37.2% formalin 282.2g 1
It dripped over time. After reacting at reflux temperature for 3 hours, distillation was started and the temperature was raised to 180 ° C. Then the temperature is 220 ℃
Vacuum distillation at 50 torr (6.65 kPa) for 1 hour, softening point 62 ° C measured by B & R method, free phenol amount 0.1% measured by gas chromatography, GP
A novolac resin (I having a number average molecular weight of 540 by C) (I
got a). The novolak resin was diluted with methanol so that the solid content was 80%, and a methanol solution of the novolak resin (Ia) was tested as follows. Then, 131 g of the methanol solution (Ia) of the novolak resin obtained above and 92%
18 g of paraform was mixed well, 2.0 g of 48% sodium hydroxide was added thereto, and the temperature was raised to 80 ° C. 80
After reacting for 3 hours at 0 ° C, distillation was carried out at 50 torr (6.65 kPa) until the temperature in the system reached 90 ° C. Thereafter, 24 g of methanol was gradually added and cooled to obtain a methanol solution of resin. The nonvolatile content of this resin measured at 135 ° C. was 60%, and the viscosity measured at 25 ° C. with a B type viscometer was 120 mPa · s. The amount of free phenol measured by gas chromatography of this resin is 0.01%
Met.

Synthesis Example 2 Methanol solution 10 of the resole resin obtained in Synthesis Example 1
Novolak resin solid content 6 prepared by the following method to 0 g
0 g and 40 g of methanol were added, the nonvolatile content measured at 135 ° C was 60%, and the viscosity was 1 measured at 25 ° C with a B-type viscometer
A resin of 35 mPa · s was obtained. The fluphenol content of the resin measured by gas chromatography was 0.1%. Next, a 2-liter four-necked flask was charged with 941 g of phenol and 40.3 g of 37.2% formalin,
4.705 g of oxalic acid dihydrate was added, the temperature was raised to 100 ° C., and 621.0 g of 37.2% formalin was added dropwise over 1 hour. After reacting at reflux temperature for 3 hours, start distillation and
The temperature was raised to 80 ° C. Then raise the temperature to 220 ℃
Perform vacuum distillation at torr (6.65 kPa) for 1 hour, and perform B & R
Novolak resin (IIIa) having a softening point of 112 ° C. measured by a gas method, a free phenol amount of 0.1% measured by gas chromatography, and a number average molecular weight of 850 by GPC.
Got

Synthesis Example 3 A solution of the novolak resin obtained above in methanol (I
a) 131 g and 18% of 92% paraform were mixed well, 0.52 g of zinc acetate was added thereto, and the temperature was raised to 100 ° C.
After reacting at 100 ° C for 1 hour, 50 torr (6.65 kP
Distillation was carried out in a) until the temperature in the system reached 90 ° C. Thereafter, 24 g of methanol was gradually added and cooled to obtain a methanol solution of resin. The nonvolatile content of this resin measured at 135 ° C. was 60%, and the viscosity measured at 25 ° C. with a B type viscometer was 112 mPa · s. The amount of free phenol measured by gas chromatography of this resin is 0.
It was 01%. 60 g of the novolak resin (IIIa) obtained in Example 2 and 40 g of methanol were added to 67 g of this resin, and the nonvolatile content measured at 135 ° C. was 60%.
Viscosity 110 mPa · s measured at 25 ° C with B-type viscometer
Was obtained. The amount of free phenol measured by gas chromatography of this resin was 0.1%.

Synthesis Example 4 Phenol 941 and 3 were placed in a 3-liter 4-necked flask.
After charging 1048 g of 7.2% formalin and adding 47 g of 25% ammonia water, the temperature was raised to 80 ° C and the temperature was raised to 3 ° C at 80 ° C.
After maintaining for a while, distillation was performed at 50 torr (6.65 kPa) until the temperature in the system reached 90 ° C. After this, methanol 6
Slowly add 60 g, cool and add 40 g of methanol to the resin, 60% of non-volatile content measured at 135 ℃,
Viscosity measured at 25 ° C with B-type viscometer 180 mPa · s
Was obtained. The amount of free phenol of this resin measured by GPC was 8.1%. To 100 g of this resin, 60 g of the novolak resin prepared in Example 2 and 40 g of methanol were added, and the nonvolatile content was 60% and the viscosity was 150 mPa.
s resin solution was prepared. The amount of free phenol measured by GPC of this resin was 4%.

Synthesis Example 5 Resol resin / novolak resin = 4 using exactly the same resole resin and novolak resin obtained in Synthesis Example 1
It was adjusted to be / 6 (solid content ratio), and a resin liquid having a nonvolatile content of 60% was prepared.

Examples 1 to 3 and Comparative Examples 1 and 2 Using the resin solutions of Synthesis Examples 1 to 5, glass cloth (manufactured by Nitto Boseki; WG-250) was mixed with (resin) / (glass cloth after drying). After impregnating so that the weight ratio became 3/7 (weight ratio), it was dried at 80 ° C. for 10 minutes to obtain a prepreg. This prepreg is treated at 180 ° C for 60 minutes, and volatile matter (VC
%) Was measured. Furthermore, this prepreg is 10 cm x 1
It was punched into 0 cm, 30 sheets were stacked, 100 g of weight was applied, and the sheets were stored in a thermostatic chamber at a temperature of 30 ° C. and a humidity of 80%, and changes in adhesiveness and flexibility over time were measured. The adhesiveness was measured by peeling the prepreg, and the flexibility was measured by a cantilever type flexibility measuring device. (The higher the value of the cantilever type flexibility meter, the more flexible it is.)

Diameter 355 mm × thickness 2.7 mm × hole diameter 2
A cutting grindstone of 5.4 mm and a density of 2.25 was prepared by a usual method. At that time, one prepreg impregnated with the resin obtained in each of Synthesis Examples 1 to 5 was sandwiched in the center of the cutting grindstone to prepare a cutting grindstone reinforced with the prepreg, and the rotational breaking strength of the grindstone was measured. The rotational strength represents the maximum number of revolutions required for the reinforced cutting grindstone to be attached to a sander and rotated at high speed to destroy the grindstone by centrifugal force or the like.
(The higher the rotation speed, the higher the rotation breaking strength.)

The measurement results are shown in Table 1.

[0039]

[Table 1]

[0040]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a prepreg having a low volatile content (VC), low adhesion,
In addition, it is possible to obtain a prepreg and a whetstone that can maintain flexibility over a long period of time.

Claims (6)

[Claims] 1. Aldehydes and phenols [aldehydes] / [phenols] = 0.3-0.6 [molar ratio]
Novolak resin (I) obtained by reacting at a ratio of
A prepreg obtained by impregnating or coating a fibrous base material with a solution (A) containing a resole resin (II) obtained by reacting an aldehyde with an aldehyde, and then drying. 2. A prepreg obtained by mixing the solution (A) according to claim 1 with a novolac resin (III), impregnating or coating the fibrous base material, and then drying. 3. The residual phenol amount of the novolak resin (I) is 1% by weight or less, and the novolak resin (I)
The prepreg according to claim 1 or 2, wherein the residual phenol amount of II) is 0.2% by weight or less. 4. The prepreg according to claim 1, wherein the mixing ratio of the resole resin (II) and the novolak resin (III) is 10 to 90/90 to 10 (weight ratio). 5. A fibrous base material made of glass.
The prepreg described in any one of 1. 6. A grindstone in which the prepreg according to any one of claims 1 to 5 is reinforced with a heat-molded prepreg.