JPS59161270A - Production method for polyurethane grindstone - Google Patents

Abstract

PURPOSE:To obtain a polyurethane grindstone easy to be finished with little abrasion by mixing and stirring grinding particles with the urethane composing materials including urethane prepolymer blocked in free isocyanate base for forming and hardening by heat. CONSTITUTION:For instance, 100pts.wt. of white alundum of a fineness 40 meshes are mixed with 50pts.wt. of urethane composing materials including blocked urethane prepolymer to be stirred for an hour. And there, 20pts.wt. of 5% resolution of carboxymethyl-cellulose is mixed and stirred for another one hour. The raw material thereby obtained to form a grindstone is poured into a grindstone mold, and then heated and hardened by a hot blast circulating heater for hardening the resin. After heating it at 70 deg.C for 12hr, it is removed from the mold and further heated at 180 deg.C for 18hr for obtaining a polyurethane grindstone.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a polyurethane grinding wheel having an extremely homogeneous grinding wheel structure and appropriate elasticity.

In general, grinding wheels use a binder such as phenol resin, epoxy resin, polyester resin, NBRn, rubber resin such as chloroprene rubber, polyvinyl alcohol resin, etc., and add abrasive grains and, if necessary, filler, foamed M1, and thickener. It is manufactured by mixing, stirring, molding, and curing colored pigments, etc.

The structure of a grinding wheel consists of abrasive grains, a binder, and pores, and its performance is greatly influenced by the binder used.

That is, the holding power of the abrasive grains changes depending on the properties of the resin that is the binder, which has a great effect on the speed of wear of the grindstone and the surface roughness of the workpiece by grinding. When phenol resin, polyester resin, or epoxy resin among the above resins is used as a binder, these resins firmly hold the abrasive grains, so the particle size of the abrasive grains can be reduced to the surface of the workpiece! It has a direct effect on fl. In addition, when polyvinyl alcohol resin is used as a binder, these resins hold the abrasive grains in a soft manner, so the degree of softness of the resin that is the binder depends on the particle size of the abrasive grains. It has a large effect on the surface roughness of the workpiece.

Conventionally, with a grindstone using a resin as a binder, problems have arisen in all of the above cases, especially when performing precision grinding.

That is, in the former case, although the abrasive grains are strongly held, it is poor in elasticity, and therefore, when attempting to reduce the surface roughness, there are disadvantages in that many processing steps are required and the processing time is significantly lengthened. In addition, the latter has drawbacks such as waviness due to excessive elasticity9, abrasive grains often falling off abnormally during high-grinding processing with weak abrasive retention power, increased wear, and low grinding power. be.

As mentioned above, conventional grinding wheels have various drawbacks, especially when used for precision grinding, and the current situation is that a grinding wheel that can satisfy both grinding performance and processing cost has not been obtained. .

In view of the above-mentioned current situation, the present inventor conducted extensive research in order to obtain a grindstone that has excellent performance even in precision grinding, and found that if polyurethane resin is used as a binder for the grindstone, since the incyanate group is highly reactive, the resin will It is thought that it not only shapes the abrasive grains, but also forms an adhesive bond with the abrasive grains, which holds the abrasive grains strongly and eliminates abnormal drop-off of the abrasive grains).It also has a moderate amount of elasticity9 and has a small surface roughness. Considering this, we tried using polyurethane resin as a binder, but ordinary polyurethane resin raw materials consisting of urethane prepolymer (or diisocyanate compound and polyhydroxy compound) and curing agent have a pot life of several tens of minutes. Because it is short and
The polymerization reaction started during stirring and mixing, and the abrasive grains, filler, etc. could not be sufficiently stirred and mixed until they were uniformly dispersed in the polyurethane resin, and the resulting grindstone was as shown in the comparative example below. It could not be put to practical use because it lacked the homogeneity of its structure, which is the most important characteristic for a grindstone. The polyurethane resin raw material, which is a urethane composition containing such a limmer, is heat-curable, so no curing agent is required, and the pot life is extremely long, so it must be thoroughly stirred until the abrasive grains, filler, etc. are uniformly dispersed. The resulting grinding wheel has an extremely homogeneous grinding wheel structure and moderate elasticity due to the polyurethane resin, and because of this, the surface roughness of the grinding surface is small, especially when used for precision grinding. After discovering that the surface accuracy is extremely excellent, that the precision finishing of the ground surface is easy and the machining time can be significantly shortened, that abnormal drop-off of abrasive grains can be prevented and that there is little wear on the grinding wheel, we have completed the present invention. It's arrived.

That is, the present invention relates to a method for producing a polyurethane grindstone, which comprises mixing and stirring abrasive grains into a urethane composition containing a urethane prepolymer in which free incyanate groups are blocked, followed by molding and then heat curing. .

The urethane composition containing a urethane prepolymer in which free incyanate groups are blocked, which is used as a polyurethane resin raw material in the present invention, is known, for example, Japanese Patent Publication No. 53-29198, Japanese Patent Publication No. 55-39.
No. 254, Japanese Patent Publication No. 56-49950, etc.

That is, the resin raw material is tolylene diisocyanate, 4
．． Polyisocyanate compounds such as 4'-diphenyl methane diisocyanate and hexamethylene diisocyanate are used in excess, and polyethers such as single or copolymers of alkylene oxides having 2 to 6 carbon atoms, and succinic acid are used in excess. At least one polyol compound of polyester or polyester ether, which is a linear or branched condensate obtained from polyhydric carboxylic acid (or its anhydride) such as , adipic acid, or fluoric acid, and various glycol compounds. If necessary, the terminal free isocyanate groups of the urethane prepolymer obtained by reacting with a chain extender such as 1,4-fringiol, trimethylolpropane, or ethylenediamine by a known method are blocked using a blocking agent in a conventional manner. This is a urethane composition obtained by using a urethane composition.Blocking agents include i+ sulfates such as sodium bisulfite, potassium bisulfite, ammonium bisulfite, globyl alcohol, isopropyl almal, imbutanol, ter
t ~ Alco-/l' such as butanol, oximes such as benzophenone oxime, methyl ethyl ketone oxime, cyclohexanone oxime, formald oxime, imines such as ethyleneimine, lactams such as ε-caprolactam, malonic dimethyl, acetylacetone ,
Examples include active methylene compounds such as methyl acetoacetate, phenols, etc., and at least one of these may be used, but in some cases aminosulfonic acids such as sulfanilic acid and N-phenylaminomethanesulfonic acid, glycine, and alanine may be used. , aminocarboxylic acids such as aminobenzoic acid, and hydroxy acids such as glycolic acid, lactic acid, malic acid, and salicylic acid? May be used together.

The urethane composition used in the present invention is entirely aqueous, and is a solution, emulsion, or dispersion using water and a hydrophilic solvent as a medium. However, since the blocked urethane prepolymer itself can act as an emulsifier, it is also possible to use a hydrophobic solvent in combination.

Furthermore, all urethane prepolymer derivatives (Japanese Patent Publication No. 56-49950) may be used as emulsifiers in urethane compositions. Examples of media other than water include ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, and N.

Examples include amides such as N-dimethylformamide, nitriles such as acetonitrile, esters such as ethyl acetate, hydrocarbons such as toluene, and logenated hydrocarbons such as methylene chloride. Use seeds or a mixture of two or more.

The 1/methanocompound used in the present invention usually has a molecular weight of 80 to 180.
By heating to about ℃, the blocking agent dissociates and the incyanate group is regenerated, followed by polymerization and curing, but the above-mentioned dissociation temperature is relatively low in the case of using bisulfuric acid atM as the blocking agent. preferable.

The solid content q of the urethane composition is usually about 10 to 60% by weight. The amount of the urethane composition to be used is not particularly limited, but is usually about 5 to 30 parts as a resin component per 100 parts of abrasive grains.

The abrasive grains used in the present invention include white alundum (W
A), alumina-based abrasive grains such as Alundum (A), silicon carbide-based abrasive grains such as Green Carborundum (GC), Carborundum (0), diamond, cubic boron nitride (CB
Examples include abrasives such as superabrasives such as N), abrasives such as chromium oxide, tin oxide, cerium oxide, iron oxide, and zirconium oxide, and one or more of these may be used.

The grain size of the abrasive grains used is a large mesh size depending on the purpose of the whetstone.

In addition, in the production method of the present invention, inorganic fillers such as calcium carbonate, cryolite, calcium fluoride, and magnesium fluoride, polyester fibers,
One or more of synthetic fibers such as polyamide fibers, natural fibers such as sheep and animal fibers, etc. may be blended. Among the above, the particle size of the inorganic filler is usually 0.1 to 30 μm.
In the case of fibers, it is preferable that the length is usually about 0.1 to 5 mm and the diameter is about 0.5 mm or less. When adding a filler, the amount used is 1 abrasive grain.
Usually about 0.5 to 20 parts by weight is suitable for 00 weight sliding part.

Further, in the present invention, the foaming agent may be omitted if necessary. Such blowing agents include azo compounds such as azobisisobutyronitrile, diazoaminobenzene, azohexahydrobenzonitrile, p,p'-oxy-bis(benzenesulfonylhydrazide), benzenesulfonylhydrazide, diphenylsulfone. Examples include organic blowing agents such as sulfonyl hydrazide compounds such as disulfonyl hydrazide, azide compounds such as terephthal azide%'P''-butylbenzazide, and inorganic blowing agents such as ammonium carbonate, sodium bicarbonate, and hydrogen peroxide. The amount used when blending a foaming agent using these Lm or two or more is usually 0.2 to 0.2 to 100% of abrasive grain
Approximately 10 overlapped parts are appropriate.

Further, in the present invention, a binder may be added as necessary. Examples of the binder include methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, etc., and one or more of these may be used. When a binder is added, the appropriate amount is usually about 08i to 5 times abrasive grains per 100 times abrasive grain.

In addition, in the manufacturing method of the present invention, phenol resin, epoxy resin, melamine resin, polyester resin, polyvinyl alcohol resin, polyethylene resin, polyamide resin, etc. may be used as an auxiliary agent for the binder, if necessary. It's okay. Furthermore, coloring pigments such as carbon black, red iron oxide, titanium dioxide, and chromium oxide may also be used.

In the manufacturing method 2 of the present invention, the above-mentioned components to be blended are stirred and mixed with the mud for about 6 hours until they are uniformly dispersed, and then poured or press-fitted into a grindstone mold. When mixing with zero agitation for molding, the above-mentioned solvents and water used in the urethane composition may be used as appropriate.

Next, the formed whetstone is polymerized and hardened by heating it using a hot air circulation type heater or the like. The heating conditions at this time vary depending on the urethane composition used, but a typical example is heating at a temperature of about 25 to 100°C for about 3 to 12 hours, and then heating at a temperature of about 100 to 100°C. It may be heated at a temperature of about 200° C. for about 3 to 12 hours. Also,
The temperature may be gradually raised from room temperature to about 200°C (at a heating rate of about 5 to 30°C per hour). The demolding may be performed immediately after injection or press-fitting, after the completion of heat curing, or during heat curing. The whetstone that has been heated and hardened is adjusted to a predetermined size (excess portions such as pars are removed and shaped), and the product is made into a product.

According to the polyurethane grindstone obtained by the manufacturing method of the present invention, the following remarkable effects can be obtained.Ofl) Since the grindstone has an extremely homogeneous structure and moderate elasticity, it has excellent grinding and sharpening ability.

(2) Especially when used for precision grinding, the surface accuracy is extremely excellent because the surface roughness of the ground surface is small.

Ru. ＼ (3) With (2) above, precision finishing of the ground surface becomes easy and the finishing time can be shortened.

(4) There is almost no abnormal falling off of abrasive grains, and there is little wear on the grindstone.

Because the polyurethane grindstone obtained by the manufacturing method of the present invention has the above-mentioned effects, it is suitable not only for normal grinding and polishing of glass, metals, plastics, non-metals, ceramics, stones, etc., but also particularly for precision grinding and polishing. .

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In addition, "parts" refer to parts by weight.

show.

Example 1 White alundum (particle size, 400 mesh) tooz
and 50 parts of a urethane composition containing a blocked urethane prepolymer (manufactured by Daiichi Kogyo Seiyaku ■ RL (-38'', solid weight: 22 times) and stirred for 1 hour.Here, 20 parts of a 5φ solution of carboxymethyl cellulose The components were mixed and further stirred for 1 hour to obtain a raw material for forming a grindstone. After pouring this raw material for forming a grindstone into a grindstone mold, the resin was heated and cured using a hot air circulating heater (C) to harden the resin. Heating is 70
After heating at 180°C for 12 hours, the mold was demolded and further heated at 180°C for 12 hours. A polyurethane grinding wheel according to the present invention was thus obtained.

Example 2 Green carborundum (particle size, 2000 mesh) 1
00 evil and cryolite (particle size, 5 μm) t.

Mix the parts and stir for 2 hours. After mixing 40 parts of a urethane composition containing a blocked urethane prepolymer (rE-37J, manufactured by Daiichi Kogyo Seiyaku ■, solid weight: 27 g), the mixture was further stirred for 3 hours to obtain a raw material for forming a grindstone. This molding raw material was poured into a grindstone mold and heated and hardened using a hot air circulation heater. Heating was performed at 60°C for 6 hours, then at 80°C.
Heating at 160°C for 6 hours After demolding, further heat at 160°C for 12 hours. A polyurethane grinding wheel according to the present invention was thus obtained.

Example 3 50 parts of chromium oxide (particle size, 0.3 μm) and 50 parts of tin oxide (particle size, 0.5 μm) were mixed and stirred for 0.5 hours.

Further, 4 parts of wool (length 7-5 mm, diameter Q, 1 mm or less) is mixed and stirred for 2 hours. Here, “E-37J
After mixing 20 parts of the mixture, 20 parts of rm-as"tf) and 20 parts of water, the mixture was further stirred for 3 hours to obtain a grindstone forming raw material. This grindstone forming raw material was poured into a grindstone mold and hardened by heating with a hot air circulating heater. After heating at 70°C for 12 hours, the mold was demolded and further heated at 170°C for 12 hours. In this way, a polyurethane grindstone according to the fourth invention was obtained.

Example 4 70 parts of white alundum (particle size, 3000 mesh) and 30 parts of iron oxide (particle size, 1 μm) were mixed and stirred for 1 hour. Here, 40 parts of rLI-38J and phenol resin (
Sumitomo Bakelite ■ [“PR.

51404J) and 20 parts of water, further,
The mixture was stirred for 4 hours to obtain a raw material for forming a grindstone. This molding raw material was poured into a grindstone mold and heated and hardened using a hot air circulation heater.

Heating was carried out at 50°C-70°C for 12 hours and then further heated at 70°C.
The molding was performed at -160°C for 12 hours and then demolded. A polyurethane grinding wheel according to the present invention was thus obtained.

Example 5 Green carborundum (particle size, 3000 mesh)
Mix 10 parts of calcium carbonate (particle size, 5 μm) and stir for 1 hour. Here, a urethane composition containing a blocked urethane prepolymer (Dai-Kogyo Seiyaku ('! (1)
40 parts of RLJX-1023J (solid content: approximately 42 weight φ) were mixed and further stirred for 3 hours to obtain a grindstone forming raw material.

This molding raw material was press-fitted into a grindstone mold, and then heated and hardened using a hot air circulating heater to harden the resin. Heating was done by raising the temperature from room temperature to 170'C in increments of about 6% C for 1 hour.
The mold was removed after 4 hours. Thus, an inventive polyurethane grindstone was obtained.

Example 6 Cerium oxide (particle size, 0.7 μl 1 liter) 100 mm, polyamide di fiber (length 0.5 mm 1 diameter 0.03 ml 1 liter)
l) Mix 5 ingredients and stir for 1 hour. rDX-1 here
023J, 5 parts of phenol resin (f'R-51404J' manufactured by Sumitomo Bakelite (1), and 40% of water were added and stirred for further 3 hours).Next, 30 parts by weight of hydrogen peroxide aqueous solution 3 of the grindstone was added and stirred for 10 minutes to obtain a raw material for forming a grindstone. After injecting this raw material for forming a grindstone into a grindstone mold, the resin was cured. After heating at room temperature for 6 hours, the mold was removed and The temperature was increased by about 8°C per hour to 18°C for 18 hours. Thus, a polyurethane grinding wheel having numerous pores according to the present invention was obtained.

Example 7 Two parts of chromium oxide (particle size, 3 μm) and sheep rainbow (
(Length 7-5 mm, Diameter Q, 1 mm or less) are mixed and stirred for 1 hour. 50 parts of rDX-1023J and LO part of dioxane were mixed therein, and the mixture was stirred for 1 hour.

Rough, phenolic resin (rPR made by Sumitomo Bakelite)
-940J) 5th part? Add p- and stir for 2 hours.
p'-oxy-bis(benzenesulfonylhydrazide)
2 parts were added and further stirred for 1 hour to obtain a grindstone forming raw material. The raw material for molding was poured into a grindstone mold and heated and hardened using a hot air circulation heater. Heating from room temperature to 200℃1
The temperature was increased by about 7.5°C per hour for 24 hours, and the mold was removed. In this way, a polyurethane grindstone having numerous pores according to the present invention was obtained.

Comparative Example 1 A polyether-based urethane prepolymer (manufactured by Nippon Polyurethane Industry ■ [c!-4090J) was preheated at 85°C, and then melted at 120°C to give fc4.4'-#f.
The renubi-2-chloroaniline was mixed and stirred for 1-2 minutes. Next, white alundum (particle size, 400 mesh) preheated at 120° C. was mixed and stirred for 10 minutes to obtain a grindstone and a forming raw material. This molding raw material was press-fitted into a grindstone mold, and heated and hardened using a hot air circulation type heater. Heating was performed at 120°C for 1 hour, then demolded, and further heated at 120°C.
I did it for 5 hours. A comparison polyurethane whetstone was obtained by sniffing. In addition, since polymerization and hardening of this whetstone started from the time of stirring, agitation and shaping were not performed well, and this grindstone could not be used for grinding tests.

Next, a grinding test was conducted using the grindstones obtained in Examples 1 to 7 and a conventional product (a grindstone using a phenolic resin as a binder). The results are shown in Table 1 below: 0: Fair 31!1: Good Note) The grinding conditions are as follows.

Grinding machine: Bunkata grinding machine Grinding fluid: water.

Grinding wheel peripheral speed near 00m/min.

Next, in order to investigate the microscopic homogeneity of the structures of the polyurethane grinding wheels obtained in Example 1 and Comparative Example 1, a scanning electron microscope (model: M8M-9) manufactured by Akashi Seisakusho ■ was used to examine the fracture surface. Electron micrographs (200x magnification) were compared. FIG. 1 is a photograph of a fractured surface of a polyurethane grindstone of Example 1, and FIG. 2 is a photograph of a fractured surface of a polyurethane grinding wheel of Comparative Example 1. Note that the length of the white line on the upper right side of the photograph is 111 μm. 1 and 2, in Example 1, the polyurethane resin and abrasive grains were uniformly dispersed, and the coated grinding wheel structure was extremely homogeneous, whereas in Comparative Example 1
Many areas where the polyurethane resin and abrasive grains were separated were observed, indicating that the grindstone structure was not homogeneous.

Next, the degree of balance (mass of weight) was measured for the grindstones obtained in Examples 1, 2.4, and 5 according to the balance test specified in 3.4 of JIS R6240. The results are shown in Table 2 below.

Table 2 Note) *According to each example, outer diameter 205 mm, hole diameter 25
．． A grindstone with a diameter of 4 mm and a thickness of 25 mm was manufactured.

”JIS 16212(7)3-4 Table 8 mb
≦5m'B (mb is the quality of the weight jn (g), m is the i of the grindstone
Jl (Kg)), the quality of the weight jfk (g
) is shown as an integer rounded off.

In the balance test, the weight It j! (actual measured value) is the equilibrium degree (J
However, as shown in Table 2, the grindstone according to the present invention has a value much smaller than the JIS specification value, indicating that it is a substantially homogeneous grindstone.

Next, the surface roughness curve of the workpiece was measured when a grinding test was conducted using the grindstone of the example and the conventional grindstone. The results are shown in Figure 3. In FIG. 3, (5) shows the surface roughness curve when using the grindstone of Example 1, and (B) and (q) show the surface roughness curve when using the conventional grindstone. As a conventional product, a grindstone manufactured by using phenol resin as a binder and the same abrasive grains as in Example 1 was used.In addition, as a measuring instrument for the surface roughness curve, a grindstone manufactured by Tokyo Seimitsu ■ was used. "Surfcom 60B" was used.The grinding conditions are as follows.

Processed product Nigarasu.

Grinding machine: Bunkata surface grinding machine.

Grinding fluid: Water.

Grinding wheel peripheral speed: 700 m/”in□ Cutoff value: 0.8mm0 Grinding time 24 and (Bl is 1 minute, (0) is 2 minutes.

As is clear from FIG. 3, 4 and (B), the polyurethane grinding wheel according to the present invention does not cause uneven grinding on the surface of the workpiece, and the center line average The roughness also became smaller.

Also, as is clear from (0), when the grinding time is doubled using the conventional grinding wheel, the grinding unevenness on the surface of the workpiece decreases, but the center line average roughness is larger than that of the polyurethane grinding wheel of the present invention. showed that.

These results show that the polyurethane grindstone according to the present invention takes a significantly shorter time to grind a workpiece and also significantly reduces the roughness of the workpiece surface, compared to conventional grindstones.

[Brief explanation of drawings]

Fig. 2 shows scanning electron micrographs (200 times magnification) of fractured surfaces of polyurethane grindstones obtained in Example 1 and Fig. 2 in Comparative Example 1, respectively. In Figure 1 and Figure 2 of the coffin, the length of the white line on the upper right side of the photograph is 111 μm. Moreover, FIG. 3 shows the surface roughness curve of the workpiece. In Fig. 3, (A) shows the use of the grinding wheel of Example 1 and the glass
The curve i, t8) when grinding for 1 minute is the curve when glass is ground for 1 minute using a conventional grindstone, and 10) is the curve when the glass is ground for 2 minutes under the same conditions as (13).
Each is shown below. (that's all)

Claims (1)

[Claims] (2) A method for producing a polyurethane grindstone, which comprises adding abrasive grains to a urethane composition containing a urethane prepolymer in which free isocyanate groups are blocked, stirring the composition, shaping the composition, and heating and curing the composition.