JPH04370182A - Method for stabilizing substrate with phenolic resin applied thereto and production of resinoid grindstone - Google Patents

Abstract

PURPOSE:To obtain the subject substrate excellent in blocking resistance even under conditions of high temperatures and humidities by applying a liquid resol type phenolic resin and hexamethylenetetramine, etc., to a substrate and further applying a polyisocyanate to the resultant substrate. CONSTITUTION:The objective substrate is obtained by applying (A) a liquid resol type phenolic resin, (B) a powdery novolak type phenolic resin and (C) hexamethylenetetramine to a substrate and further applying (D) a polyisocyanate to the resultant substrate. The component (A) is applied in an amount of 0.5-50 pts.wt. (preferably 20-40 pts.wt.) based on 100 pts.wt. total amount of the components (B) and (C) and the component (C) is applied in an amount of 5-25 pts.wt. based on 100 pts.wt. solid content of the component (B). Furthermore, the component (D) is applied in an amount of 1-50 pts.wt. (preferably 2-30 pts.wt.) based on 100 pts.wt. component (A).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stabilizing a phenolic resin-adhered substrate and a method for producing a resinoid grindstone.

0002

[Prior Art] A method for manufacturing a resinoid grindstone is to attach a liquid resol-type phenolic resin to abrasive grains such as aluminum oxide or silicon carbide, and then to attach a powdered novolac-type phenolic resin, hexamethylenetetramine, and a filler. The molding and firing methods are well known.

0003

[Problems to be Solved by the Invention] However, abrasive grains in which a mixture of a liquid resol type phenol resin, a powdered novolac type phenol resin, and hexamethylenetetramine are attached in this order have the disadvantage that they are extremely susceptible to blocking. Ta.

0004

[Means for Solving the Problems] Therefore, the present inventors conducted intensive studies in view of the above-mentioned actual situation, and unexpectedly found that blocking could be prevented by further adhering polyisocyanate after the phenol resin treatment. From the beginning, we have now completed the present invention.

That is, the present invention further comprises applying polyisocyanate (D) to a base material on which liquid resol type phenolic resin (A), powder novolac type phenolic resin (B) and hexamethylenetetramine (C) are adhered in this order. A method for stabilizing phenolic resin characterized by adhering liquid resol type phenol resin (A), powder novolac type phenol resin (B) and hexamethylenetetramine (C
) and polyisocyanate (D) are attached to abrasive grains in this order, followed by shaping and firing.

The liquid resol type phenolic resin (A) according to the present invention is one whose solid content is liquid at room temperature, and any known and commonly used resin can be used. Examples of the resol type phenolic resin (A) include those reacted using an alkali catalyst (hereinafter referred to as unneutralized type),
The former is neutralized with acid (hereinafter referred to as neutralized type),
Examples include benzyl ether type phenol resins that contain a large number of benzyl ether groups in their molecules that are reacted using metal salt catalysts, but benzyl ether type phenol resins and the neutralized type mentioned above have a slow reaction rate. It is preferable in that it allows slow and good resin flow, and among the neutralization types, one in which barium hydroxide is used as a catalyst and neutralized with sulfuric acid is preferable.

[0007] Two or more different types of resol type phenolic resins may be used in combination. The liquid resol type phenolic resin (A) is prepared by, for example, reacting phenols and a formaldehyde supplying substance in a ratio such that the molar ratio of formaldehyde supplying substance to phenol is 1 to 2.5, optionally in the presence of a catalyst. Examples include things that have been done.

[0008] The above reaction may be carried out in the presence of an organic solvent, or an organic solvent may be added to the obtained reaction product. However, it is preferable to use an aqueous solution because it has an excellent ability to adsorb powdered novolak type phenol resin (B) and hexamethylenetetramine (C), which will be described later.

[0009] As the above-mentioned phenols, any known and commonly used ones can be used, and examples include phenol, bisphenol F, bisphenol A, and bisphenol AF.
bisphenols such as cresol, alkyl substituted phenols such as P-tert-butylphenol,
Halogenophenols such as bromophenol, aromatic hydrocarbons containing two or more phenolic hydroxyl groups such as resorcinol, naphthols such as 1-naphthol, 2-naphthol, 1,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, etc. etc. These phenols may be used not only alone, but also as a mixture of two or more of these compounds.

[0010] As the formaldehyde supplying substance, any known material can be used, and for example, formaldehyde aqueous solution and paraformaldehyde can be used. Examples of catalysts include sodium hydroxide, potassium hydroxide,
Examples include alkali catalysts such as barium hydroxide and amine catalysts, and metal salt catalysts such as zinc acetate and manganese borate.

[0011] Examples of acids used in producing the neutralized resol type phenolic resin include inorganic acids such as sulfuric acid, hydrochloric acid, and oxalic acid, formic acid, acetic acid, phenolsulfonic acid,
Examples include toluenesulfonic acid.

In producing the resol type phenolic resin (B), furfural, urea, melamine, acetoguanamine, benzoguanamine, etc. may be used in combination with the phenol, if necessary.

[0013] The above reaction may be carried out in a batch reactor, but
It may also be carried out in a tubular reactor with static mixing elements. As the novolak type phenolic resin (B) according to the present invention, any known and commonly used ones can be used. Furthermore, novolac type phenolic resins having modified parts such as rubber-modified, epoxy-modified, and polyvinyl butyral-modified parts can also be used.

[0014] The novolak type phenolic resin (B) may be used in combination of two or more different types. The novolak type phenolic resin (B) is prepared by combining the same formaldehyde supplying substance and phenols as explained in the resol type phenolic resin (A), for example, in the presence of a catalyst as necessary, at a molar ratio of 0.7 to 0.7. It can be easily obtained by reacting in such a way that the value of 1.0 is obtained.

Examples of the catalyst include acid catalysts such as oxalic acid, hydrochloric acid, and sulfuric acid, and metal salt catalysts such as zinc acetate and manganese borate. When the metal salt catalyst is used, a high orthophenol novolac type phenol resin can be obtained.

[0016] In producing the novolac type phenolic resin, furfural, urea, melamine, acetoguanamine, benzoguanamine, etc. may be used in combination with the phenol, if necessary.

The above reaction may be carried out in the presence of an organic solvent, or an organic solvent may be added to the obtained reaction product. The reaction may be carried out in a batch kettle or in a tubular reactor with static mixing elements.

In the present invention, novolac type phenolic resin (B
) is usually used in powder form. When the novolac type phenol resin (B) is in the form of an aqueous solution, an aqueous dispersion, or an organic solvent solution, it is preferable to remove the solvent, dry, and pulverize before use. For removing the solvent and drying, for example, a thin film evaporator or a spray dryer can be used.

The ratio of hexamethylenetetramine (C) and novolak type phenol resin (B) to be used is not particularly limited, but usually 5 to 5 parts of hexamethylenetetramine per 100 parts by weight of solid content of novolak type phenol resin (B).
It is 25 parts by weight.

[0020] The weight ratio of the resol type phenolic resin (A) to the total of the novolak type phenolic resin (B) and hexamethylenetetramine (C) is usually the same as that of the novolac type phenolic resin (B) and hexamethylenetetramine (C).
0 resol type phenolic resin per 100 parts by weight of total
．． 5 to 50 parts by weight, preferably 20 to 40 parts by weight.

[0021] In the present invention, polyisocyanate (D) is the most important component in improving the stability of the phenol resin-attached substrate. Polyisocyanate (D
), any known and commonly used ones can be used, but
For example, aromatic diisocyanates such as diphenylmethane-4,4'-diisocyanate, tolylene diisocyanate, xylylene diisocyanate, ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate. , aliphatic or alicyclic diisocyanate such as dicyclohexyldimethylmethane-4,4'-diisocyanate, carbodiimide-modified polyisocyanate, crude diphenylmethane diisocyanate, adduct of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate, 1 mol of pentaerythritol and adduct of 3 moles of tolylene diisocyanate,
Examples include products in which a polyol and a polyisocyanate are reacted so as to have an excess of isocyanate groups, such as an adduct of 1 mole of trimethylolpropane and 3 moles of hexamethylene diisocyanate, and an adduct of 1 mole of pentaerythritol and 3 moles of hexamethylene diisocyanate. . The polyisocyanates may be used alone or in combination of two or more.

[0022] As the polyisocyanate (D), one having a low viscosity as an active ingredient is preferred because it can be easily applied to a substrate. In order to improve workability, an organic solvent may be used in combination with the polyisocyanate (D), if necessary.

The amount of polyisocyanate (D) used is not particularly limited, but is usually 1 to 50 parts by weight per 100 parts by weight of the liquid resol type phenolic resin (A), which has a particularly high blocking effect and is suitable for phenolic resins. The amount is preferably from 2 to 30 parts by weight because it does not impede the fluidity (flow) during curing and causes less deterioration in strength.

[0024] The present invention is characterized in that component (D) is further adhered to the base material to which the above-mentioned components (A) to (C) have been adhered. As the base material used here, any known and commonly used base material can be used, including abrasive grains such as aluminum oxide, silicon carbide, diamond, boron nitride, and zirconium oxide, foundry sand such as silica sand and silica, glass fiber, and carbon fiber. ,
Examples include inorganic base materials such as fibers such as silicon carbide fibers, plastic particles such as styrene beads and acrylic beads, and organic base materials such as fibers such as polyester fibers, nylon fibers, cotton fibers, and hemp fibers.

[0025] The method for attaching the above components (A) to (C) to the base material is not particularly limited, but for example, a method of kneading the base material and the components (A) to (C) using a mixer or the like. is common.

[0026] As a method for attaching component (D) to a base material to which components (A) to (C) have been attached (hereinafter referred to as a resin-attached base material), for example, the above-mentioned resin-attached base material and component (D) may be attached. Examples include a method of kneading with a mixer or the like, a method of spray coating the resin-attached substrate with component (D), a method of dip-coating the resin-attached substrate with component (D), and the like.

The total amount of components (A) to (D) deposited on the substrate is usually 5 to 200 parts by weight per 100 parts by weight of the substrate. Next, the stabilization method of the present invention will be explained using a resinoid grindstone as an example.

[0028] When manufacturing a resinoid grindstone, the order in which components (A) to (C) are attached to the abrasive grains is usually prepared in advance after attaching component (A) to the abrasive grains. Preferably, a mixture of component (B) and component (C) is further deposited.

[0029] As a method for manufacturing a resinoid grindstone, the following method may be mentioned. First, liquid resol-type phenolic resin (A) is mixed with abrasive grains and kneaded well to obtain abrasive grains whose surfaces are wet, and then powdered novolak-type phenolic resin (B) and hexamethylenetetramine (C) are separately mixed. To,
Alternatively, resin coated grains (hereinafter referred to as RCG) are prepared by adding fillers and additives to the premixed mixture as required.

Examples of fillers and additives that can be used as necessary include cryolite, iron oxide, barium sulfate, iron fluoride, sodium aluminum fluoride, carbon black, and the like. When these components are used, they are preferably used in an amount of 1 to 20 parts by weight per 100 parts by weight of abrasive grains.

Next, polyisocyanate (D
) is attached. It is preferable to attach the polyisocyanate (D) to the RCG immediately after the preparation of the RCG, since blocking is less likely to occur.

The polyisocyanate-attached RCG thus obtained is used after removing the organic solvent and water as required. This polyisocyanate attached RCG,
A grindstone can be obtained by molding into a desired shape using a mold heated to room temperature or 40 to 80°C, and heating and firing this molded product for 15 to 50 hours. The conditions for heating and firing are not particularly limited, but for example, the temperature may be raised from room temperature to 200° C. over 10 to 24 hours, maintained at the peak temperature for 3 to 10 hours, and then slowly cooled.

[0033] The climate in Japan is hot and humid, especially in the summer, and there are always cases where the fabricated RCG causes blocking. Once blocked, RCG is almost impossible to mold. Furthermore, even if the RCG has a low degree of blocking, the molded whetstone will be unbalanced and have low strength.

Furthermore, in winter, although the produced RCG does not cause blocking, a phenomenon often occurs in which the powdered phenolic resin or filler once coated peels off from the abrasive grains and separates. In this case, unevenness occurs during filling, causing the grindstone to become unbalanced, resulting in reduced strength and poor grinding performance.

The stabilization method of the present invention solves these phenomena and provides RC without blocking or peeling of resin or filler.
G, greatly improves workability, and contributes to keeping the performance of the whetstone constant throughout each season.

[0036] In the above explanation, a whetstone was used as an example, but
It goes without saying that the stabilization method of the present invention can also be applied to the fields of foundry sand and molding materials, and is not limited to stabilizing RCG of grindstones.

[0037]

EXAMPLES Next, the present invention will be explained in detail with reference to Examples, in which "parts" mean parts by weight and "%" mean % by weight unless otherwise specified. Example 1 A benzyl ether type resol resin aqueous solution (solid content 70%) obtained by reacting formaldehyde and phenol at a molar ratio of 1.3/1 at pH 4.5 using zinc acetate as a catalyst.
, viscosity 500 cps/25°C) 5 parts (solid content) and brown fused alumina abrasive grains (particle size 36; JIS R6001)
100 parts of the abrasive powder were added to a Shinagawa mixer and thoroughly mixed at room temperature until the resin was uniformly adhered, and the abrasive grains were wetted with the resin.

On the other hand, powdered novolak type phenolic resin (
A mixture of 91 parts (melting point: 90°C) and 9 parts of hexamethylenetetramine (fluidity: 25 mm, gelling time: 60 seconds), 15 parts of artificial cryolite, and 1 part of carbon black were mixed in advance in a separate Shinagawa mixer. Add the abrasive grains moistened with the resin obtained first, mix thoroughly at room temperature again until the resin and filler are evenly attached to the abrasive grains, and then add the resin coat. Tid Grain-1 (hereinafter referred to as RCG)
It is called -1. ) was obtained.

An ethyl acetate solution of polyisocyanate obtained by reacting tolylene diisocyanate, 1,3-butanediol, and trimethylolpropane with the above RCG1 (non-volatile content 75%, viscosity 500 cps/25°C)
) 0.5 part (solid content) to make R of polyisocyanate
Mix thoroughly at room temperature until the adhesion to CG-1 becomes uniform, and prepare Resin Coated Grain-2 (hereinafter referred to as RCG-2).
That's what it means. ) was obtained.

[0040] Brown fused alumina abrasive grains (particle size 36; JIS
Resin coated grain-2 except that brown fused alumina abrasive grains with a grain size of 80 were used instead of R6001).
Resin coated grain-3 (hereinafter referred to as RCG-3) was obtained by performing a series of operations exactly the same as those for obtaining.

[0041] The above kneading work was carried out at a temperature of 30°C.
The tests were conducted indoors with humidity adjusted to 80%. Both RCG-2 and RCG-3 were very smooth and easy to handle. (Evaluation test) RCG-2 was left in a room adjusted to a temperature of 30° C. and a humidity of 80% for 16 hours, and the presence or absence of blocking was examined.

[0042] Also, RCG-2 was filled into a mold and molded at room temperature, and the temperature was raised from room temperature to 180°C over 16 hours.
After being held at 0° C. for 5 hours, it was allowed to cool to obtain a test piece measuring 15 mm in width x 10 mm in thickness x 20 mm in length and having a bulk specific gravity of 2.2. Using this test piece, bending strength and water resistance strength were measured.

The normal bending strength was measured using the above test piece with an Autograph manufactured by Shimadzu Corporation, with a distance between fulcrums of 15
The test was carried out under the following conditions: 0 mm and head speed of 10 mm/min. The water resistance strength was measured by leaving the test piece in water at room temperature for 3 days, and then measuring it while still wet under the same conditions as the bending strength.

Furthermore, RCG-2 is sprinkled on the mold, a glass fiber cloth impregnated with a thermosetting phenolic resin is placed on top of the mold, RCG-2 is spread on top of the glass fiber cloth impregnated with a thermosetting phenolic resin, and a glass fiber cloth impregnated with a thermosetting phenolic resin is placed on top of the glass fiber cloth impregnated with a thermosetting phenolic resin. Place the fiber cloth and R on it.
Spread CG-3, press-mold at room temperature, raise the temperature from room temperature to 180°C over 16 hours, hold at 180°C for 5 hours, let it cool, and make a 180mm diameter x 6mm thickness x 22m hole diameter.
An offset grindstone having a weight of 350 g and a bulk specific gravity of 2.15 was obtained.

[0045] Using this offset grindstone, rotational strength,
The grinding ratio was measured. The rotational strength was determined by measuring the number of rotations at which it broke using a rotational fracture testing machine manufactured by Tokimoto Koki Co., Ltd. (the higher the rotational strength, the better the strength), and the grinding ratio was determined using SS-4 as the work material.
Using a steel material No. 1, the amount of grinding for 10 minutes was measured using a hand grinder equipped with a resinoid grinding wheel, and this value was divided by the amount of wear of the grinding wheel (the higher the grinding ratio, the better the performance). show good things).

[0046] Above, RCG state after being left, normal bending strength,
The first results summarize the measurement results of water resistance strength, rotational strength, and grinding ratio.
Shown in the table. Example 2 Instead of benzyl ether type phenol resin, barium hydroxide (catalyst) was used to react formaldehyde and phenol at a molar ratio of 1.3/1, and then neutralized with sulfuric acid, and the nonvolatile content was reduced to 70%. Neutralized resol type phenol resin aqueous solution (viscosity 500 cps/2
The same operation as in Example 1 was performed except that the same amount (solid content) of 5°C) was used to obtain a test piece of the same size and a bulk specific gravity of 2.21, and a grindstone of the same size and a bulk specific gravity of 2.14. .

[0047] Using this, measurements were made on the same items as in Example 1. The measurement results are summarized in Table 1. Example 3 Instead of the benzyl ether type phenolic resin, sodium carbonate (catalyst) was used to react with formaldehyde and phenol at a molar ratio of 1.3/1 to obtain a dehydrated unneutralized resol type phenolic resin aqueous solution (solid content). 70%,
The same operation as in Example 1 was performed except that the same amount (solid content) of viscosity 500 cps/25°C was used, and a test piece of the same size and bulk specific gravity of 2.20 and a grindstone of the same size and bulk specific gravity of 2.15 were used. I got it.

Using this, measurements were carried out on the same items as in Example 1. The measurement results are summarized in Table 1. Comparative Example 1 The same operation as in Example 1 was carried out except that polyisocyanate was not used, and the bulk specific gravity was 2.20 with the same size.
A test piece, a grindstone of similar size and bulk specific gravity of 2.15 was obtained.

Using this, measurements were carried out on the same items as in Example 1. The measurement results are summarized in Table 1. Comparative Example 2 The same operation as in Example 3 was carried out except that polyisocyanate was not used, and the bulk specific gravity was 2.20 with the same size.
A test piece, a grindstone of similar size and bulk specific gravity of 2.15 was obtained.

Using this, measurements were carried out on the same items as in Example 1. The measurement results are summarized in Table 1.

[0051]

[Table 1]

[0052] As can be seen from Table 1, the base material to which polyisocyanate is attached is superior in terms of blocking properties and is also superior in terms of strength, compared to the base material to which polyisocyanate is not attached. is clear.

[0053]

[Effects of the Invention] In the present invention, since polyisocyanate is further attached to the conventional phenolic resin-attached base material, blocking can be made extremely difficult to occur compared to the conventional phenolic resin-attached base material. The obtained base material exhibits a particularly remarkable effect of exhibiting excellent handling properties.

[0054] In the method for manufacturing a grinding wheel of the present invention, resin-coated grains to which polyisocyanate is attached are used, so even under relatively harsh conditions, the resin coating itself does not block or the resin component peels off from the abrasive grains. It is possible to manufacture extremely stable and strong grindstones without any problems.

Claims (5)

[Claims] [Claim 1] Liquid resol type phenolic resin (A)
A method for stabilizing a phenolic resin-adhered substrate, which comprises further adhering a polyisocyanate (D) to the substrate to which the powdered novolac type phenolic resin (B) and hexamethylenetetramine (C) are attached. [Claim 2] Liquid resol type phenolic resin (A)
Claim 1 is an aqueous solution of a resol type phenolic resin.
Stabilization method described. [Claim 3] Liquid resol type phenolic resin (A)
The stabilizing method according to claim 1, wherein is an aqueous solution of a benzyl ether type phenol resin or a neutralized resol resin. 4. The stabilizing method according to claim 1, wherein the amount of polyisocyanate (D) used is 1 to 50 parts by weight per 100 parts by weight of the liquid resol type phenolic resin (A). [Claim 5] Liquid resol type phenolic resin (A)
, a mixture of powdered novolac type phenolic resin (B), hexamethylenetetramine (C), and polyisocyanate (C) are attached to abrasive grains in this order, and then shaped and fired.