DE1962803A1 - Organic resin bond for abrasives - Google Patents

Description

PATENTANWÄLTE FW H EM MER ICH GERDM Ü LLE R - D. G ROSSE 21 653

DÜSSELDORF 1 0 H OM BE R G E R STR ASSE 5 October 22, 1969

bh.'bi "

AVCO CORPORATION, '~

Organic resin bond for abrasives

This invention is concerned with an organic resin bond for abrasives. An epoxy system is described, which contains the constituents that promote grinding in its molecular structure, with resins halogenated bisiaenol based are preferred. For patent protection is claimed for this system

In the abrasives sector, reference to hardness and weakness can often lead to misunderstandings. To the To reduce and hopefully also to dispel these misunderstandings, reference is made to the physical one Hardness or softness and the grinding hardness or grinding softness. The physical hardness relates the physical properties of the grinding, by means of and depends on the material used, the density of the body, the porosity, etc.

The grinding hardness is a measure of resistance or willingness to enter a bond with v / elcher Emits abrasive grain. The grinding hardness is an operational variable related to the grinding process. In general there is a qualitative assignment between the physical hardness and the grinding hardness. There is a direct or proportional ratio.

The degree of physical hardness and the grinding hardness of grinding wheels and abrasives is combined into one wide range due to the ratio of the sole grain,

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the bond and the porosity are determined and regulated. the softest grinding wheels have the largest share of Abrasives and porosity, but the smallest amount of bond. The hardest grinding wheels, however have the lowest percentage of abrasives and porosity, but the largest bond percentage.

The two most uncertain and yet most necessary properties, The mechanical strength and the Uniformity. It is immediately clear that mechanical strength is very important with a grinding wheel Poor strength will not only wear out very quickly, but will also pose a great danger in use represent.

Uniformity is important in three ways: once there should be an abrasive, but especially one Grinding wheel to be uniform in itself. Then the one belonging to the same production batch! Grinding wheels all be equal to each other. Finally, grinding wheels should be from different production quantities, which have been manufactured according to the same recipe and process and in compliance with the same standards, the essence be identical one after the other or only vary within prescribed tolerances.

In achieving a bond strength, the greatest difficulties arose in the manufacture of soft grinding wheels.

Many bond systems have turned out to be hard grinding wheels proved to be quite satisfactory. There is plenty of binding agent in the raw mix, and

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it is relatively easy to make a homogeneous mixture. The large proportion of binding secures and guarantees the finished grinding wheel also has a high level of strength.

When making soft grinding wheels, however, the selection of a bond system is critical. The in The small amount of binder present in the mixture makes the manufacture of a homogeneous abrasive very good difficult. Achieving uniformity therefore requires great care during processing. About that In addition, with such a low bond content, soft grinding wheels can only have sufficient strength very difficult to reach

Much advances have been made over the years with respect to organic grinding systems for grinding wheels. In the production of soft ships ... ^ n with a mechanical strength, which there, Γ ^; 53 ^:.,. ^: ^ '/ is approximated to the hard grinding wheels, aex ¹ large · breakthrough has not yet been achieved. Any grinding wheel which had sufficient mechanical strength was inevitably too hard in structure for the desired soft grinding operation, which is absolutely necessary in many grinding-related cases. Another problem that exists in the grinding wheel sector is due to the fact that organic resin bonding systems are or can be subject to degradation due to the action of coolant saturation. At we * r; Grinding wheels where the bond strengths are necessarily too small or in the limit range _% ti.ldet such degradation is a serious problem, because even a slight degradation can weaken the grinding wheel so much,

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that it becomes useless and insecure. Because of the coolant attack the grinding hardness becomes noticeably softer during operation, which in turn leads to numerous operational difficulties caused.

In addition, a number of substances have been developed in the industry, which act as means that Promote grinding, for example the halogens and the gravity. These fabrics tend to affect the grinding performance to increase, but also to make grinding easier in many applications.

In the case of soft grinding wheels with an organic resin bond, the use of agents that promote grinding, not widely used because this grinding-promoting agent has been added to the binding as a filler up to now have been. These fillers strengthen the resin, which in turn leads to greater grinding hardness. One Compensation for this increase in hardness by reducing the resin content would be the grinding wheels in the construction make insecure. These fillers are therefore used for the purpose to be achieved here, namely production against a soft grinding wheel.

A breakthrough in the development of a soft grinding wheel would be to have a soft grinding process with a To achieve structural strength that is greater than before. In addition, it would be a significant advance if Active grinding aids in soft grinding wheels could be used without affecting the hardness of the original soft grinding wheel is enlarged.

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The present invention, therefore, aims to provide a resin bond for abrasives which the The mechanical strength of the grinding wheels is increased and a smooth grinding process is guaranteed.

Another object of this invention is to provide a resin bond for abrasives which permits the use of grinding aids or the abrasive agent in the abrasives without using these additives as fillers. ' ä

Yet another object of this invention is to provide a resin bond for abrasives which use manufacture soft grinding wheels that are uniform in hardness and strength.

Another object of this invention is to provide a resin bond for abrasives that enhances uniformity softer grinding wheels improved from lot to lot.

Another object of this invention is to provide a resin bond for abrasives which allows the incorporation of (

Grinding aids - i.e. agents that promote grinding - into the molecular structure of the grinding wheel resins as constituents of, for example, epoxies, hardeners of epoxies and additives or fillers of Epoxies.

Yet another object of this invention is to provide a resin bond for abrasives which is a brominated Glycidyl ether epoxy is used as the base of a soft grinding wheel, the mechanical strength of which is greater than for a comparable grinding hardness in the industry too

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finding conventional grinding wheel strength.

In the context of this invention, an organic resin bond for abrasives consists of an epoxy-based system, which the often used grinding aids in the molecular structure of the resin system (as components) contains.

Furthermore, within the scope of this invention, an organic bond for abrasives consists of a tetrabromo-epoxy resin bisphenol-A-based, which reacts with brominated bisphenol-A-based epoxy with a Hardening agent is formed from amines or anhydrides.

The novel properties characteristic of this invention are recited in the claims. the However, the invention itself, as regards its structure and mode of operation, are its further aims and advantages best understood with the help of the description below.

An important thought of this invention is the use of grinding aids - i.e., means which the Support and promote the grinding process - with soft grinding wheels, in such a way that the soft grinding effect can be maintained and improved. From the conceptual point of view, this is done by the fact that they are used as a grinding aid Substances are made part of the molecular structure of the resin bonding system. But that means the grinding aids or components, for example sulfur or the halogens, bromine, chlorine, iodine and fluorine become part of the inner groups of the epoxies or become components of the hardening agents, for example the Amines or the anhydrides. It is also possible to use fillers

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and to provide additives, for example reaction liquids which have also been halogenated or sulphurised. Examples of epoxies which have halogens and sulfur in their molecular structure are abundantly contained in the Handbook of Epoxy Resins by Lee and Neville, published by McGraw-Hill Publishing Company in 1967. The same applies to hardeners and epoxy modifiers and fillers which contain halogens and sulfur in their molecular structure. Examples of epoxies which would correspond to this concept would be the glycidyl ethers, for example the chlorobisphenols and the bromobisphenols. Alpha-based epoxies are discussed on pages 2-17 and throughout the referenced text.

If it is also not required, halogenated or Using sulphurized hardening agents is a must halogenated anhydrides as well as suitable hardeners, for example Tetrabromo-Phthalic-Anhydride, Chlorndic-Anhydride, Dichloro-Maleic-Hydride and Tetrachloro Phthalic anhydrides.

Other hardeners that fall within the scope of the invention to incorporate the grinding aids into the molecular structure of the resin system are methylene bis 2,6 dichloro dianiline ( commonly known as MOCA). Hardeners derived from alkyl halides, carbon tetrahalides, carbon disulfide, hydrogen sulfide contain grinding aids as components. Thiokol Corporation has marketed polysulfides for blending with epoxies in proportions that tend to contain a large amount of sulfur.

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In the sector of epoxy modifiers and fillers, for example compounds such as hexofluoropropylene oxide, the chloroprenes are useful. A chlorinated phenolic diluent is found on page 13-2 of the reference discussed. There are others.

Sanding performance depends in part on the ability of a bond to deal with a worn or dull abrasive grain give in and sell off at the right time. A hard grinding wheel with a bond that is very tight If the abrasive grain adheres, the abrasive grain only repels with great resistance. On the other hand, it has a soft Grinding wheel is a bond that repels an abrasive grain in a relatively short time.

In both cases, however, the same triggering process or triggering mechanism is effective. The temperature in the vicinity of an abrasive grain reaches several hundred to over 1000 ^° F. If the abrasive grain is dull, it has to work harder for this reason in order to be able to carry out the cutting process or the machining process, then the temperature caused in the grain approaches the higher temperatures of the work area. There is a thermal breakdown of the resin bond. In some places it becomes sufficiently soft to be able to repel the abrasive grain.

When thermal degradation occurs, the structure of the resin collapses. It comes with a halogenated one or sulfonietten epoxy resin system to a breakdown, then in addition to the elementary halogen and sulfur also Hydrogen halides or hydrogen sulphides emitted. This degradation takes place in the intermediate zone between the abrasive grain and the workpiece, precisely where the Grinding aids work most effectively.

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The time consuming problem of making a soft grinding wheel with a strength which is greater than the previous one, has been solved through the use of an epoxy system based on tetrabromobisphenol A. Degree of hardness by degree of hardness, structure by structure, are compared with such epoxy compositions, which of the photoresin bond have 50% more bond, used to produce abrasive grades that match those of the The same as grinding wheels with a photoresin bond. It was previously pointed out that the physical hardness with the Resin content in the composition increases. It was also suggested that greater uniformity can be achieved from production volume to production volume if the resin content is increased.

Compared with the conventional phenol systems, an equivalent grinding hardness can be found in the bisphenol A epoxy system achieve with 50% more resin. But that is a very significant contribution in terms of the way it is Manufacture grinding wheels.

The examples given below are intended to illustrate the various Types are shown in which a tetrabromo-bisphenol-A system has been used for the manufacture of soft grinding wheels.

Example No. 1

As for grinding with soft grinding wheels, a new performance is with a grinding wheel has been achieved, which is composed of 52 percent by volume of abrasives, 12 percent by volume of brominated bisphenol A bond and 36 percent by volume of pores. These Binding was made from a dry fraction of

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80 - 85% of the total resin mass and the rest as Liquid part.

The ratio of powder-form resin to hardener of 90/10 range up to 60/40.

The dry portion belonging to the resin system is obtained by mixing 80 to 8 5 parts by weight of solid tetrabromo-bisphenol-A, which is sold as EPO-TUF 9 0-16 5, with 20 to 15 parts by weight of diamino diphenyl sulphone, which is sold as EPORAL. The liquid part is made up of 65 parts by weight of a lower molecular weight Tetrabromo-bisphenol-A, which is sold as Epi-Rez 516 3 and is mixed at 25 parts by weight a low-molecular epoxy derivative of bisphenol-A, which is sold as Epi Rez 510 and with 10 parts by weight of tetra-hydro-furfural alcohol. The alcohol serves to reduce the viscosity of the mass. It is also a weak solvent, which when wetting the abrasive grain helps.

The abrasive is first wetted with the liquid component, then the dry resin component is added and mixed until the dry resin adheres all over the abrasive.

The mixture obtained in this way is placed in a mold and with

pressed at a pressure of two tons / inch, namely cold pressed. Then the grinding wheel is removed from the mold and oven dried and cured. The drying process or Hartung starts at 150 F, the temperature is increased within nine hours 39O ⁰ F and then again held for twenty four hours at 39O ° F ".

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The grinding wheels withstand a tolerance in the drying temperature or in the hardening temperature. For best results, the final drying temperature or final curing temperature should be between 375 ° F and t50 ° F. The resin will not fully cure if the temperature is less than 375 ° F. At a temperature of more than 150 ^° F, the resin begins to degrade. In the past, a grinding wheel with a phenolic resin bond was used for the same application, which was composed as follows in the abrasive: 56% abrasive, 8% binding agent and 36% pores. Despite the 50% higher resin content, the grinding hardnesses were essentially identical, and the chip removal was roughly the same. However, this clearly demonstrates that the larger bond enables greater product uniformity and an increase in mechanical strength. As for the epoxy, the metal removal ratio per pair of grinding wheels was 22U.3 Lbs. compared to only 179.6 Lbs for a pair of phenolic bonded grinding wheels.

In the standard mechanical endurance test, in which a drill is moved back and forth under load, was the depth of penetration into the pattern grinding wheel is only half of that similar to that of phenolic bond grinding wheels Degree of hardness usual penetration depth. The physical hardness, i.e. the mechanical strength, is the opposite of the penetration depth proportional.

In a second test, the proportion of abrasive in the phenolic bond and in the epoxy bond became constant 5 «»% held. The bond share was compared to the Phenolic bond increased by 1 "+% to 16% with epoxy bond. With epoxy bond, a much larger one became

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physical hardness reached, the abrasive effect was there nevertheless two thirds softer.

The epoxy resin system described is totally reactive. the Ingredients became parts of the finished bond with little or no evaporation takes place. Earlier phenolic resin systems were burdened with considerable evaporation of the plasticizers, which tended to affect the entire bonding structure of the resin system with the abrasives tear apart and change. This then resulted in a non-uniform bond between bond and abrasives, whenever the bond distribution in the mixture was below that which had to apply perfectly.

Example No. 2

In terms of quality, it has been found that the epoxy resin system described here is a significant improvement in the water resistance and in the coolant resistance. The problem of disintegration under water and The effect of coolant on grinding wheels was, however, eliminated with such grinding wheels, which are made up of: from the brominated bisphenol resin system in connection with vinyl polysiloxane-coated abrasives. This coated abrasive is described in US Patent 2,878,111. With this abrasive is a commercially available abrasive available from General Abrasives Corporation.

All of the above related to the application of a resin system to high porosity grinding wheels. In addition, a hardness range from G-N (26 to 40% porosity) hardened.

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The components of the grinding wheel only include the resin bond and the abrasive.

It is always desirable that a bond system be used over the entire range of grinding wheel hardnesses can be, and this tetrabromo-bisphenol system can easily be used for the manufacture of grinding wheels with a lower porosity, from »0 - to ZZ hardness (24 % to 0% porosity). The porosity is due to Adding fillers, for example aluminum leather-zrikon compositions, which are known as AZ 40 fines, iron pyrites, kyrolites, etc.

Over the entire hardening system, the abrasive effect of the epoxy resin bond system is softer than an equivalent Phenolic hardness.

Example No. 3

In order to obtain a completely self-contained grinding wheel of hardness ZZ, it was necessary to perform a hot pressing process provide and change the hardener. Two hardeners have been found to be satisfactory. These both hardeners are trimellitic anhydride and pyromellitic Anhydride.

A mixture of 25.5 parts by weight of tetrabromo-bisphenol A with 5.1 parts by weight of a hardening agent, for example tri-mellitic anhydride, and 69.4 parts by weight of fillers is subjected to the hot pressing process. Twenty to forty cubic centimeters of tetra-hydro-furfural alcohol are used as a wetting agent per pound of resin. This mixture is used in a mold. This mold is for 30 to 45 minutes at a temperature of 320 ⁰ F

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held under a pressure of about 2-3 tons per square inch until the resin is no longer in the liquid state, that is, until the resin is partially cured. In this operation, then the oven curing follows at 375 ° to 450 ⁰ F T for a period of twenty-four hours.

In summary it can be said that the discovery that constituents which contain grades or hardnesses Can be incorporated into the molecular structure of epoxy resin systems has made it possible for these Grinding aids or these materials that promote grinding can be provided for soft grinding wheels. the Previous attempts to use grinding aids as fillers in soft grinding wheels have been because of incompatibility the added fillers while maintaining the soft abrasive effect economically not successfully.

The specific brominated bisphenol A system has to be one Binding structure, which has a soft abrasive effect guaranteed, but at the same time offers a more uniform structure and greater strength than that of grinding wheels conventional type, which are used in soft grinding applications exhibited similar behavior that was the case.

The various features and advantages of this ER _(invention have been clearly outlined with the above description. Experts will be able to recognize several other features and advantages which are not expressly mentioned, and likewise many changes and modifications, all of which are realized can without departing from the spirit of the present invention.

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Claims (1)

Claims An organic resin bond for abrasives, characterized in that is formed by the reaction of an epoxy, which contains constituents in the molecular structure of the resin which are able to act as grinding aids and to support grinding Process can be released during thermal degradation of the bond. 009836/2047 21 653 10/22/1969 bh.bi U - A 2 - 2). An organic resin bond for abrasives according to Claim 1, characterized in that the component is a halogen and part of the Molecular structure of the epoxy forms. 3) An organic resin bond for abrasives according to claim 1, characterized in that the constituent is sulfur and part of the Molecular structure of the epoxy forms. Ό An organic resin bond for abrasives in accordance with Claim 1, dadu.rch characterized that the component is a halogen and part of the Forms the molecular structure of the hardener. 5) an organic resin bond for abrasives according to claim 1, characterized in that the constituent is sulfur and part of the Molecular structure of the hardener forms. 6) an organic resin bond for abrasives according to claim 1, characterized in that it continues to contain epoxy modifiers and fillers belong, which have grinding aid constituents in their molecular structure. 7) an organic resin bond for abrasives according to claim 1, characterized in that • that the epoxy is selected from the classes which 009836/2047 - A 3 - original ^VED 21 653 10/22/1969 bh.bi η - ^{A 3} - Glycidyls, cyclic and acyclic epoxies based on aliphatic. 8) An organic resin bond for abrasives according to claim 1, characterized in that the hardener is selected from the group of amines and Anhydride has been selected *. 9) an organic resin bond for abrasives according to claim 1, characterized in that the components already mentioned from one Material class have been selected which contains halogens and sulfur. 10) an organic resin bond for abrasives according to claim 1, characterized in that it consists of an epoxy-based resin system, which formed from a brominated bisphenol-A resin is, exists. ( 11) An organic resin bond for abrasives according to claim 10, characterized in that the epoxy is tetrabromo-bisphenol A. 12) an organic resin bond for abrasives according to claim 1, characterized in that it includes fillers which are the setting serve the grinding hardness. - A h - 009836/2047 ORIGINAL INSPECTED 21 10/22/1969 bh.bi - ^{A 4} ' 13) An organic resin bond for abrasives, characterized in that it consists of an epoxy resin, which by reaction of tetra-bisphenol A with a hardener emerged from the group of amines and anhydrides. 14) An organic resin bond for abrasives according to claim 13, characterized in that the amine is a diamino-diphenyl sulphone and the anhydride is a trimellitic anhydride. 15) An organic resin bond for abrasives, characterized in that that it consists of an epoxy resin, which by reaction of a solid resin content of tetrabromo-bisphenol A and a hardener with a liquid fraction of tetrabromo-bisphenol A, bisphenol A and Teta-hydro-furfural alcohol was created. 16) An organic resin bond for abrasives according to claim 15, characterized, that the dry portion consists of 85 percent by weight of the total resin composition, but the liquid phase about 15 percent by volume. 17) an organic resin bond for abrasives according to claim 15, characterized in that in the dry portion of the resin composition 90-60 proportions of solid tetrabromo-bisphenol A are included; the hardener 10 - 40 parts of the dry portion of the Resin mass is. 009836/2047 ORIGINAL INSPECTED 21 653 10/22/1969 bh.bi ff -AS- 1 9 E- 2 & 0 18) An organic resin bond for abrasives according to claim 15, characterized in that the dry portion is 80-85 parts epoxy and 20 parts the hardener contains; the liquid portion 65 parts brominated epoxy, 25 parts bisphenol and Contains 10 parts of tetra-furfural alcohol. 19) an organic resin bond for abrasives according to claim IS, characterized in that a hot pressed bond is made from 25.5 parts by weight of tetrabromo-bisphenol A, 5.1 parts by weight trimellextic anhydride and 69.4 parts of fillers. 20) An organic resin bond for abrasives according to claim 15, characterized in that the hardening agent is a diamino-diphenyl sulfone. - End - 009836/2047 ihärcCTED