DE2730665A1 - Grindstones for wet grinding - contg. curable hydrophilic satd. polyester or epoxy! resin binder - Google Patents

Abstract

Grindstones comprise abrasive grains embedded in a currable plastic binder consisting of a satd. polyester resin and/or an epoxy resin having in the cured state at normal temp. a water absorption of >=0.5%, a Shroe D hardness of 50-95 and an elongation at break of >=2%. Suitable hydrophilic binders are polyesters contg. >=30 mol.% adipic acid and/or diethylene glycol, the hardness and elongation at break being controlled by the addn of plasticisers. Suitable epoxy resin binders are e.g. a bisphenol-A-diglycidylether with an epoxide value of is approx. 0.53 with 10-30% of a reactive diluent such as 1,4-butanediol-diglycidyl ether as hydrophilising agent; or a mixt. of bisphenol-A-epoxide resins with polyglycol diglyciyl ethers, with an epoxide value of 0.35-0.50. The grindstones have high strength, resistance to fracture, freedom from overheating and 'bluing' of the metal being ground, and reduced hardness is comparison with ceramic wheels. The prods. are esp. useful in the pron. of honing and polishing stones.

Description

description

The invention relates to a grinding wheel for wet grinding Made of curable plastic as a binder with embedded abrasive grains, in particular also fine and very fine grains.

The oldest and best known artificial grinding wheel bond is the ceramic, which has high temperature resistance with edge stability and water resistance connects. Also due to the open structure in the coarse to medium grain range Take enough cooling water with you during wet grinding. In the fine and finest grain area however, the ceramic bond is not suitable in many cases. Furthermore the ceramic bond is also unsuitable for various grinding tasks, for which purpose Among other things, the flat cut with a large contact surface for heat-sensitive Steels, whereby these disks grind too hot, as well as centerless cylindrical grinding, especially with pipes, whereby there are vibrations in the Machine and comes to a "hammered" appearance of the micrograph.

Next up with regard to its importance as a grinding wheel binder follow the phenolic resins, which are suitable from coarse to precision grinding, but because of their sensitivity to Alkalis for wet sanding are unsuitable. In addition, the panes with phenolic resin bond are for the Flat grinding with a large contact area and for centerless cylindrical grinding Tubing also unsuitable for the same reasons as the ceramic bonds.

Furthermore, one knows magnesite and silicate bonds for grinding tools, which is gentle and cool grinding and therefore species) for flat grinding with large Contact surface on heat-sensitive steels are suitable. One disadvantage of this However, bonds are their brittleness and the resulting susceptibility to breakage. Abrasives of this type of bond are therefore not required for work igabilities of over 20 m / sec. authorized.

In addition, they have the disadvantage that they harden over time and in terms of their grinding performance strongly dependent on the prevailing Humidity are.

There has therefore been no lack of attempts to create grinding wheel binders to develop taking advantage of the aforementioned abrasive grit binders without have their disadvantages. Based on experience, it was assumed that such new binders must have high heat resistance, at least one such the Phenolic resins. Furthermore, these binders should have a high hardness have good impact resistance to hold the individual abrasive grain firmly in its Able to hold. In addition, it was best to use such new binders as possible to make waterproof, which inevitably led to a certain hydrophobicity Has.

So are slip rings for working knife blades, scissors etc., which are made with specially selected unsaturated polyester resins are bound. Due to their dense structure and hydrophobicity, these can be compared with corresponding slip rings in magnesite bond, however, only in narrow widths up to approx. 15 mm can be used. When using wider slip rings occurs a hydroplaning effect, which occurs in the middle of the respective contact surface overheating. Here either the resin bond is softened or to a blue tarnishing of the steel to be processed.

Honing wheels for fine machining have also become known of gears in epoxy resin bond. However, only a low relative speed occurs here between the abrasive grain and the workpiece surface, and this honing process made under oil lubrication. Furthermore are known become, Phenolic resins that increase their impact resistance with a small percentage proportion of epoxy resins have been modified. Discs with such binders However, they are only used for dry sanding.

Surprisingly, it has now been found that resin combinations ideally suited for certain grinding tasks, which according to the current state of knowledge appeared unsuitable. The invention, contemporary grinding wheel for wet grinding made of hardenable Plastic as a binding agent with embedded abrasive grains, especially also and fine grains, is now characterized by the use or co-use of such saturated polyester resins and / or such xthoxylin resins as binders, which in the hardened state at normal temperature has a water absorption capacity of at least 0.5 * a Shore hardness of D 50 - 95 and an elongation at break of at least 2 * have.

In particular, the hydrophilic binder can be at least 30 moles, condensed from adipic acid and / or diethylene glycol and its hardness and Elongation at break can be regulated via the degree of crosslinking and the addition of plasticizers. The use of bisphenol A diglycidyl ether with an epoxy value can also be used from about 0.53 and 10-30% of a reactive diluent such as 1,4-butanediol diglycidyl ether take place as a hydrophilizing element and the binder also a mixture of Contains bisphenol A epoxy resins with polyglycol diglycidyl ethers.

Finally, the use of aliphatic polyamines, such as amidoamines take place in the binder as a hardener and when using hydroxylated aliphatic Polyamines in the binder act as hardeners, and at the same time act as a means of increasing the water absorption capacity to serve. duch is the use of one with hydrophilic substances such as swelling clay or Cellulose powder mixed with a hydrophobic synthetic resin mixture can be used as a binder.

Some exemplary embodiments of the invention are included below with the following substances: Resin A liquid epoxy resin viscosity: 950 - 1,050 cP 250 epoxy equivalent 186 - 189, epoxy value 0.50 - 0.54 density at 200 Cel. 1.16 refractive index nD25 1.5520 This is on the one hand a dian base resin from cP 10,000-13,000 which by adding?, 4-butanediol diglycidyl ether has been brought to the above viscosity.

Hars B, liquid eposidhars, mixed condensate from Dian A and polyglycol Viscosity: 550 - 650 cP 250 epoxy equivalent 259 - 266 epoxy value 0.38 - 0.39 Density 200 oil. 1.15 refractive index nD25 1.5145 RSn redirection product from 100 g resin B with 9 parts of triethylenetetramine as hardener has the following properties, for example: Flexural strength: no break Limit bending stress: 54 kp / centimeter² Impact strength: over 40 cm x kp / cx2 modulus of elasticity: approx. 600 kp / cm² water absorption: 30 days, 25 ° Cel. 0.82% 24 hours, 100 ° Cel. 3.24% Hardener C, faster hardening, physiologically harmless imin-hardened viscosity: 350 - 450 cP 250 amine equivalent: 51 seals 200, 1.10 refractive index: nD25 1.497 hardener D, polyaminoamine hardener, physiologically harmless viscosity: cP 250 15,000 - 20,000 amine equivalent: 100 Seals 200 1.00 Refractive Index: nD25 1.510.

The following mixing ratios are given as examples: Example 1s Resin A 720 parts Resin B 80 parts Hardener C 200 parts Krund 2,200 parts Shore D 90 (based on binder resin) water absorption, 30 days 250 0.58 * elongation at break 3% Example 2: Resin A 294 parts Resin B 393 parts Hardener D 313 Parts corundum 2,200 parts hardness Shore D 75 water absorption 30 days 250 0.65% elongation at break 8 * Example 3: Resin B 720 parts of hardener D 280 parts of corundum 2,200 parts Shore hardness D 50 water absorption 30 days 250 0.78 * elongation at break 12% grinding results: off The formulas given in Examples 1 - 3 were used to produce slice discs, A corundum of the grain size according to FEPA P 150 was used. The grinding wheels had the dimensions 350 mm diameter, 150 mm width, 50 mm bore.

Each one of these grinding wheels was subjected to a blast test, the break occurring at speeds in excess of 120 liters per second.

In each case one disc was on a grinding machine for centerless Round grinding with a working peripheral speed of 30 m per second in wet grinding used. An abrasive emulsion consisting of 98% water and 2% additive was used duration.

Longitudinally welded pipes made of St 45 were used as workpieces. The feed rate was 4 m per minute. The results achieved are compiled in the following table: Example 1 2 3 Removal per meter of pipe in grams 1.9 2.38 1.16 Removal on the pipe diameter in mm 0.004 0.0058 0.0028 Roughness depth Rt (- R max) in micrometers 6.0 7.0 5.0 Decrease in the diameter of the discs in mm after 5 m pipe 11 30 7.5 The grinding performance of the wheel according to example 2 corresponds approximately to the performance of a grinding mass of grain 60, that of the wheel according to example 3 corresponds to the performance of a grinding belt of grain 100, but the roughness depths are then twice as high as those of the shelf disks according to the invention.

Example 4s A grinding wheel was produced according to Example 3, Dimensions: outer diameter 450 mm, inner diameter 200 mm, height of the disc 25 mm, grain size white corundum, grain size P 320.

This disk was made as a cup washer on a precision surface grinder Used in wet grinding against valve plates, material Ck 45, for fine grinding. The valve plates, pre-ground with ceramic grinding wheels, had an initial surface roughness from R-max. 1 3 micrometers. After grinding with the grinding wheel according to the invention the peak-to-valley height was R-max. 1 0.5 micrometers. Such a low roughness value was previously not achievable with other grinding wheels.

Claims (8)

"Grinding wheel for wet grinding" claims: .4); Grinding wheel for wet grinding made of hardenable plastic as a binder with embedded abrasive grains, especially fine and very fine grains, characterized by the use or Concomitant use of such saturated polyester resins and / or such xthoxylin resins as a binder, which in the hardened state at normal temperature has a water absorption capacity of at least 0.5%, a Shore hardness of D 50 - 95 and an elongation at break of at least Have 2%. 2. Grinding wheel with binder made of polyester resin according to claim 1, characterized in that the hydrophilic binder is at least 30 mol * condensed from adipic acid and / or diethylene glycol and its hardness and elongation at break is regulated via the degree of crosslinking and the addition of plasticizers. 3. Grinding wheel with binder made of xthoxylin resin according to claim 1, characterized by the use of bisphenol A diglycidyl ether with a Epoxy value of about 0.53 and 10 - 30% of a reactive diluent such as 1,4-butanediol diglycidyl ether as a hydrophilizing element. 4. Grinding wheel according to claim 3, characterized in that the Binder a mixture of bisphenol A epoxy resin with polyglycol diglycidyl ethers and the epoxy value is 0.35 to 0.50. 5. Grinding wheel according to claim 2 or 3, characterized by the Use of aliphatic polyamines or amidoamines in the binder as hardeners. 6. Grinding wheel according to claim 2 or 3, characterized by the Use of hydroxylated aliphatic polyamines in the binder as hardeners and at the same time as a means to increase the water absorption capacity. Grinding wheel according to Claim 1, characterized by the use a hydrophobic one mixed with hydrophilic fillers such as swelling clay or cellulose powder Synthetic resin mixture as a binder. 8. Binder for the production of a grinding wheel according to one of the preceding claims, characterized by the use of the aforementioned compositions.