KR810000934B1 - Process for the preparation of cuprous oxide-containing resin bonded abrasive article - Google Patents

Abstract

Grinding wheels with improved centrifugal burst speed were prepd. by blending 0.2-5.0 % Cu2O with the abrasive and the bonding resin before shaping and curing the wheels. Thus, 50g of a uniform 70:30 mixt. of Cu2O and SiC ws preblended with 465g powd. phenolic resin and 650g fluorspar, and the preblend was added to a mix. contg. 3700g 24-grit Al2O3 abrasive, 5ml wetting agent, and 185g liq. phenolic resin.

Description

[Name of invention]

Method for producing a copper oxide-containing resin-bonded abrasive

Detailed description of the invention

The present invention relates to a method for producing a resin bonded abrasive, more specifically a resin bonded abrasive wheel.

Resin-bonded abrasives, in particular resin-bonded abrasive grinding wheels, are used in a variety of ways, including grinding, polishing and cutting. In engraving, the abrasive wheel is rotated at high speed, so that sufficient physical strength and flexibility are required to withstand the high seam forces generated during rotation and to withstand the external forces applied to the wheel during grinding, polishing or cutting.

Conventionally, ultrafast wheels, that is, wheels made for use at speeds in excess of 3000 rpm, are often destroyed in use, and fragments of abrasive wheels often fly out of this wheel due to centrifugal forces. It is therefore evident that it is extremely desirable to increase the physical strength of the abrasive wheel in order to further reduce the fracture or breakage of the wheel.

Several attempts have been made to increase the strength of the polishing wheels, with limited success. This approach uses modified and modulated resins and modulated abrasive grains to increase strength as described in US Pat. Nos. 3, 481, 723 and 3, 528,790.

It has also been found to increase the strength of the wheels by using fillers in combination with resins. Incidentally, such fillers are described in US Pat. Nos. 3, 371, 700, for example IV, V, VI of the fourth period of the periodic table. And metals and metal compounds of Groups VIII and VIII. Chromium oxide can be mentioned as an example of such a compound. As further described in US Pat. No. 2,070,734, ferric oxide is known as a suitable filler. Other suitable fillers are described in US Pat. No. 3, 087, 803, examples being chromium oxide, zirconia and titania. Iron sulfide is described as a suitable filler in US Pat. Nos. 3, 63, 20, and trimanganese tetraoxide and ferric oxide are described as a suitable filler in US Pat. No. 3, 960, 517.

It has conventionally been known that other metal compounds act as suitable fillers. For example, US Pat. Nos. 3, 820, 290 describe potassium boroborate, sodium fluoride aluminium, barium sulfate, iron sulfide, and calcium oxide as satisfactory fillers. In addition to the other fillers described above, US Pat. No. 3,632,320 describes cryolites, fluorspar, zinc mixtures, lead chloride and lead sulfide as suitable fillers. U.S. Patent No. 23, 087, 803 describes this silicon oxide and aluminum oxide as suitable fillers. US Patent Nos. 2, 294, 239 and 3, 208, 836 have suggested magnesium oxide as a suitable filler. Although many fillers have been tested and used in the past, such compositions do not impart the desired strength to bonded abrasives, such as abrasive wheels, even at the level of use of commonly used heavy powders.

According to the present invention, there is provided an improved method for producing a resin-bonded abrasive prepared by mixing a cured liquid resin with an abrasive, molding the resulting mixture, and curing the resin to produce a resin-bonded abrasive. This method was improved to mix about 0.2 to 5 weight percent cuprous oxide particles into the mixture before molding the mixture. The present invention also includes a resin bonded abrasive prepared by a method in which the resin bonded abrasive contains about 0.2 to 5% by weight of cuprous oxide.

The resin-bonded abrasive prepared by the present invention is an abrasive grinding wheel that can be used in any of stock removal, polish or barrier wheels. However, the resin-bonded abrasive is an abrasive in which the abrasive is bonded together with the resin. Others of such resin-bonded abrasives are grindstones, mounted points and segments.

The abrasive used in the abrasive is abrasive grits or abrasives known to those skilled in the art, and examples thereof include alumina, silica, zirconia, diamond, garnet, or many melting and sintering mixtures of alumina, zirconia and silica, silicon carbide, and the like. . The abrasive in the resin-bonded abrasive is generally about 79.8 to about 95.8% by weight. The average particle size of the abrasive is about 90 to about 2500 microns, typically about 700 to about 1000 microns. The abrasive binds with the resin, which is cured after mixing with the abrasive. The resin may be a cured liquid or solid resin or a mixture of liquid and solid resin.

Curable resins are resins that can be cured to form a solid resin having strength and adhesion sufficient to safely bond with abrasive particles. Examples of such resins include phenol resins and polyester resins. The best resins are phenolic resins including thermosetting resol resins and novolac resins using a curing agent such as hexamethylenetetramine or paraformaldehyde. Suitable resins are mixtures with thermosetting liquid resols and solid noblock resins.

The cured liquid resin should not have a high molecular weight before curing in order to mix the abrasive particles with the resin. Therefore, before curing, the curable liquid resin should have a viscosity between about 0.8 and at most about 10,000 poise, suitably between about 10 and about 1000 poise.

Most suitable liquid phenolic resins are low cure low viscosity liquid phenolic resins having a viscosity of between about 325 and 450 centipoise at 25 ° C. and having a gel time of about 35 minutes at 121 ° C. Suitable liquid resins are commercially available from Georgia Pacific Corporation under the trade name of Reichhold Chemical Inc. under the trade name of Varcum 8121 and GP 5080 under the trade name of GP 5080.

Most suitable powdered phenolic resins are medium flow rate solid block resins containing about 2 to about 15 weight percent hexamethylenetetramine based on the weight of the novolak resin. This resin is a phenol genoblock resin containing phenol and crasol. Most suitable powdered resins have a flow rate between millimeters between about 26 and 34. The flow rate was heated on a glass plate for 3 minutes at 125 ° ± 1 ° C. to heat the pearlite of the resin to a diameter of 10 mm and a thickness of 6 mm, tilting the glass plate horizontally to 65 ° and continuing heating at 125 ° C. ± 1 ° C. for 20 minutes. After cooling the glass plate in the horizontal position, the flow rate is measured by measuring the flow distance in millimeters. Most suitable resins are also those having an apparent density of about 0.33 g per cc and containing about 7.2 to 7.7% of hexamethylenetetramine. The uncured resin has a melting point of about 90 to about 97 ° C. Suitable solid resins are the Carborandem Company (Company) under the name N ₂ , the Ashland Chemical Division under the Ashland Corporation under the trade name Arophene 875, the Baakum Chemical Div. It can be purchased from Borden Chemical Company.

It is advisable to mix the wetting or dispersing agent with the abrasive when or before mixing the abrasive with the liquid resin. Other valid reagents known to those skilled in the art may be used. Examples of effective wetting agents include liquid mixtures with about 75% by weight furfural and 25% by weight crasol, colloidal silica and silane. Wetting agents or dispersants may be used alone or in combination. Particularly effective dispersants include amine modulated organosilanes. It is preferable that these organosilanes have the following structural formula.

(Wherein R ', R2, R3 and R' are lower alkyl, lower alkoxy or amino lower alkyl groups, respectively, provided that at least one or more of the aforementioned reactors is lower alkoxy and at least one of these reactors is an amino lower alkyl group).

The lower alkyl mentioned above means an alkyl group containing 1-4 carbon atoms. Examples of such lower alkyl groups include methyl, methyl, propofyl, isopropyl, butyl, isobutyl and tert-butyl.

The foregoing alkoxy means an alkoxy group containing 1-4 carbon atoms. Examples of such lower alkoxy groups include methoxy, ethoxy, propoxy and butoxy groups.

The foregoing amino lower alkyl refers to amine groups containing 1-4 carbon atoms. Examples of such amino lower alkyl include aminopropyl, dimethylaminopropyl, aminoethyl and methylaminoethyl groups.

Particularly suitable silanes are lower alkylamine modulated triethoxysilanes. Suitable columns can be purchased from Union Carbide Silicon Divzones under the yarn name A1100 Silane and from General Electric Company Silicon Profits Divson under the trade name SC-3901.

It is preferred to mix about 0.05 to about 2% by weight of the amine modulated organosilane with the mixture even if other secondary dispersants or hydrating agents are present. It is suitable that about 0.05 to about 3 weight% of other reagents are present, such as about 0.05 to about 3 weight% of a colloidal silica dispersant (40% of colloidal silica dispersed in water).

In addition to the abrasive, it is preferred to add resins, wetting or dispersing agents, fillers (e.g. fluorspars) in an amount of from about 5% to about 25% by weight relative to the total compound weight.

The resin and other components of this composition are mixed with the abrasive using a suitable mixing device known to those skilled in the art. Examples of such mixing devices include Lancasti mixers, high speed propeller mixers and bowl mills with drums that rotate in opposite directions to the rotation of the mixing paddles. After mixing, dispersion of the abrasive grain cuprous resin (Cu₂O) and other components should be uniform.

At the same time, the abrasive particles are mixed with the other components of the composition and then the cuprous oxide particles are mixed and then mixed with the composition. Cuprous oxide is suitably 20 microns or less and preferably has an average particle size of 6 microns or less, and it is preferable to add about 0.2 to about 10 weight percent and about 0.5 to about 5 weight percent cuprous oxide based on the weight of the mixture.

Copper oxide may be added as pure copper oxide or may be mixed with other components. Premixing cuprous oxide and silicon carbide is particularly suitable for mixing 70% by weight of Cu 2 O with SiC having a particle size of 5 to 30 and an average particle size of 15.

It has been found that cuprous oxide, or a mixture of cuprous oxide and silicon carbide, as necessary, may be premixed with the filler prior to mixing with the abrasive index mixture to further disperse cuprous oxide in the composition.

After mixing, the mixed composition is molded. This molding typically involves injecting the mixture into the mould and applying a pressure of about 3 to about 300 kg per square centimeter for about 5 seconds to about 10 minutes at a temperature of about 25 ° C., preferably about 10 to about 100 ° C. The mixture in the old is pressurized.

After molding the abrasive containing about 5 to about 20% of the cured liquid resin, about 79.8 to about 94.8 wt% of the abrasive and about 0.2 to about 10 wt% of cuprous oxide are cured. Curing is typically carried out at a temperature between about 100 and about 225 ° C. for 1 to about 24 hours.

After the passage of time, it was found that the resulting resin-bonded abrasives had superior strength compared to conventional products.

The following examples are intended to illustrate the method and abrasive of the present invention and do not limit the present invention.

Example I

3700 g of a 24 grit aluminum oxide abrasive was injected into a Lincaster-type mixer having a paddle rotating in a direction opposite to the rotation direction of the rotary tub and the tub. The mixer was then operated and the aluminum abrasive had an average particle size of 5cc wetting agent containing 75furfural and 25% cresol, 185g Baakum 8121liquid phenolic resin, 465g V7608 powdered phenolic resin with medium flow rate and 200 mesh. 650 g of fluorspar having was added little by little.

The above components are mixed in a mixer until the mixture is uniform, and about 500 g of the resulting mixture is a two-layer glass fiber reinforced cloth having a mold inner dimension of 6 ＂X1 / 4＂ (thickness) and a center diameter of 1 ＂ I bought in Mould. The material in the mold was then treated at 3000 psig for 10 seconds. The resulting wheel was then sprayed with zinc stearate powder and cured for 38 hours by the following procedure:

This wheel was then separated in the curing oven when the temperature was about 52 ° C. or lower. The resulting abrasive wheel is an abrasive bond wheel made by a conventional method.

Example II

The method of Example I was repeated, with the exception of 5 cc of furfural-crasol solution and 5 cc of 40% colloidal silica suspension was added. The resulting wheels were found to have higher bursting resistance under a higher bursting rate, ie centrifugal force, than the grinding wheels prepared in Example I.

Example III

The method of Example I was repeated, with the exception of 5 cc of A1100 amino functional organosilane with the mixture. The resulting polishing wheels were found to have higher bursting speeds than the wheels prepared in Example I.

Example IV

The method of Example II was repeated, with the exception of 5 cc of A1100 amino substituted organic silane was mixed with the mixture. The resulting abrasive wheel was found to have a higher bursting rate than the wheels prepared in Examples I, II and III.

Example V

The method of Example I was repeated, but 50 g of a homogeneous mixture of 70% cuprous oxide (Cu₂O) and 30% silicon carbide (SIC) having an average particle size of 15 µP was previously prepared with a powdery phenolic resin and fluorspar. It mixed, and this premix was then added to aluminum oxide. The resulting mixture was not found to have a bursting rate improved over that of the wheels prepared in Example I.

Example VI

Although the method of Example III was repeated, 50 g of Cu2O-SiC mixture was premixed with the powdered phenolic resin and the fluorine wave. The resulting premix was then mixed with an aluminum oxide mixture. The resulting wheels were found to have a burst speed superior to that of the wheels produced by the examples.

EXAMPLE VII

Although Example VI was repeated, with the exception, 50 g of Cu2O-SiC mixture was premixed with the powdered phenolic resin and the fluorospa, and then the preliminary mixture was mixed with the aluminum oxide mixture. The resulting polishing wheel was found to be larger than the bursting speed of any of the wheels prepared in Examples I-IV and to have the same bursting speed as the wheels produced in Example IV.

EXAMPLE VII

Example VII was repeated, with the exception that 50 g of pure cuprous oxide was used in place of the Cu2O-SiC mixture. The resulting wheels have a burst rate that is about the same as the wheels prepared in Example VII.

Example XI

Six wheels were prepared by Examples I, II, IV and VIII. Twelve samples having dimensions of a cross-sectional area of about 1 × X 1/4 were cut out of the three wheels prepared in each example. This sample was then tested for tensile strength using an Instron apparatus. For each of the remaining three wheels manufactured by each example, the burst speed was tested by gradually increasing the rotational speed of each wheel until a portion of the wheel dissipated freely from the balance of the wheel. Table I shows the tensile strength in kilograms and the bursting rate in surface emitters per minute (SMPM).

TABLE I

Table I shows that the addition of cuprous oxide to the mixture used in the preparation of the abrasive, especially when used in connection with colloidal silica and organosilane, increases both the tensile strength and the rupture rate of the resulting wheel.

Claims (1)

A method of mixing a cured resin and an abrasive to shape a resulting mixture, and curing the resin to form a resin-bonded abrasive, wherein the resin is mixed with the mixture before molding about 0.2 to about 5 weight percent cuprous oxide particles. A method of making a bonded abrasive.