EP2540445B1 - Method of manufacturing a tool made from bound abrasive agents - Google Patents
Method of manufacturing a tool made from bound abrasive agents Download PDFInfo
- Publication number
- EP2540445B1 EP2540445B1 EP12167847.8A EP12167847A EP2540445B1 EP 2540445 B1 EP2540445 B1 EP 2540445B1 EP 12167847 A EP12167847 A EP 12167847A EP 2540445 B1 EP2540445 B1 EP 2540445B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- green body
- pore former
- oxalic acid
- pore
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000004519 manufacturing process Methods 0.000 title claims description 14
- 239000003082 abrasive agent Substances 0.000 title claims description 10
- MUBZPKHOEPUJKR-UHFFFAOYSA-N oxalic acid group Chemical group C(C(=O)O)(=O)O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 118
- 238000000034 method Methods 0.000 claims description 38
- 235000006408 oxalic acid Nutrition 0.000 claims description 37
- 239000011148 porous material Substances 0.000 claims description 37
- 238000000354 decomposition reaction Methods 0.000 claims description 27
- 239000000203 mixture Substances 0.000 claims description 25
- 239000011230 binding agent Substances 0.000 claims description 24
- 239000001993 wax Substances 0.000 claims description 23
- 238000010438 heat treatment Methods 0.000 claims description 20
- 238000010304 firing Methods 0.000 claims description 12
- 238000003825 pressing Methods 0.000 claims description 9
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 8
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 8
- 150000001991 dicarboxylic acids Chemical group 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 7
- 238000005469 granulation Methods 0.000 claims description 5
- 230000003179 granulation Effects 0.000 claims description 5
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 239000000470 constituent Substances 0.000 claims description 4
- 150000004677 hydrates Chemical class 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 3
- 229920000151 polyglycol Polymers 0.000 claims description 3
- 239000010695 polyglycol Substances 0.000 claims description 3
- 150000007513 acids Chemical class 0.000 claims description 2
- 238000005056 compaction Methods 0.000 claims 2
- 238000011084 recovery Methods 0.000 claims 1
- 239000003795 chemical substances by application Substances 0.000 description 28
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 25
- 238000000227 grinding Methods 0.000 description 20
- 230000008569 process Effects 0.000 description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 238000012360 testing method Methods 0.000 description 11
- 229910001868 water Inorganic materials 0.000 description 11
- GEVPUGOOGXGPIO-UHFFFAOYSA-N oxalic acid;dihydrate Chemical compound O.O.OC(=O)C(O)=O GEVPUGOOGXGPIO-UHFFFAOYSA-N 0.000 description 10
- 239000000126 substance Substances 0.000 description 8
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N activated carbon Substances [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 5
- 238000000465 moulding Methods 0.000 description 5
- 238000000859 sublimation Methods 0.000 description 5
- 230000008022 sublimation Effects 0.000 description 5
- 150000001875 compounds Chemical class 0.000 description 4
- 230000008020 evaporation Effects 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 4
- 238000009472 formulation Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000008187 granular material Substances 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 239000012071 phase Substances 0.000 description 4
- 229920001568 phenolic resin Polymers 0.000 description 4
- 239000005011 phenolic resin Substances 0.000 description 4
- 229920003023 plastic Polymers 0.000 description 4
- 239000004033 plastic Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 239000001569 carbon dioxide Substances 0.000 description 3
- 229910002091 carbon monoxide Inorganic materials 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000002360 explosive Substances 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000007493 shaping process Methods 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 231100000331 toxic Toxicity 0.000 description 3
- 230000002588 toxic effect Effects 0.000 description 3
- 206010006784 Burning sensation Diseases 0.000 description 2
- 239000004375 Dextrin Substances 0.000 description 2
- 229920001353 Dextrin Polymers 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000010431 corundum Substances 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 235000019425 dextrin Nutrition 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- 231100001261 hazardous Toxicity 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 235000011837 pasties Nutrition 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 230000004580 weight loss Effects 0.000 description 2
- OCJBOOLMMGQPQU-UHFFFAOYSA-N 1,4-dichlorobenzene Chemical compound ClC1=CC=C(Cl)C=C1 OCJBOOLMMGQPQU-UHFFFAOYSA-N 0.000 description 1
- UJBORAMHOAWXLF-UHFFFAOYSA-N 1-(aziridin-1-yl)octadecan-1-one Chemical compound CCCCCCCCCCCCCCCCCC(=O)N1CC1 UJBORAMHOAWXLF-UHFFFAOYSA-N 0.000 description 1
- 101000993093 Arabidopsis thaliana Heat stress transcription factor B-2a Proteins 0.000 description 1
- 229920001342 Bakelite® Polymers 0.000 description 1
- 241001522319 Chloris chloris Species 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 206010013786 Dry skin Diseases 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 208000035904 Exposure to mould Diseases 0.000 description 1
- 239000008118 PEG 6000 Substances 0.000 description 1
- 229920002584 Polyethylene Glycol 6000 Polymers 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 235000009470 Theobroma cacao Nutrition 0.000 description 1
- 206010053615 Thermal burn Diseases 0.000 description 1
- 239000006061 abrasive grain Substances 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000004637 bakelite Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 244000240602 cacao Species 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 1
- 238000004455 differential thermal analysis Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 239000008240 homogeneous mixture Substances 0.000 description 1
- 239000003906 humectant Substances 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000000622 irritating effect Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000010327 methods by industry Methods 0.000 description 1
- 210000004400 mucous membrane Anatomy 0.000 description 1
- 125000000740 n-pentyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 239000013618 particulate matter Substances 0.000 description 1
- 239000002006 petroleum coke Substances 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229940068886 polyethylene glycol 300 Drugs 0.000 description 1
- 229940093429 polyethylene glycol 6000 Drugs 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 230000003313 weakening effect Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
- B24D3/005—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used during pre- or after-treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
- B24D18/0009—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for using moulds or presses
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
- B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
- B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
- B24D3/34—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties
- B24D3/348—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties utilised as impregnating agent for porous abrasive bodies
Definitions
- the invention relates to a method for producing a bonded abrasive tool.
- Bound abrasive tools are widely used in the art for surface finishing. Such tools are, for example, grinding wheels, abrasive segments, grinding rods or honing stones.
- an abrasive for example corundum, silicon carbide, diamond or CBN of a desired grain size
- a binder in particular a ceramic binder
- This is pressed into a green body of the desired shape.
- the green body is then dried at suitable temperatures, optionally freed from pore formers and finally fired by a ceramic.
- such a tool should have a certain porosity, usually also a certain pore shape and size. It is therefore known to add to the mixture a pore-forming agent (usually naphthalene) which occupies corresponding proportions of space in the green body.
- a pore-forming agent usually naphthalene
- the pore-forming agent is removed by evaporation, sublimation or by burning. This can be done during the sintering process or in a temporally upstream process step at lower temperatures.
- naphthalene can be removed even at relatively low temperatures, namely by Sublimation at about 80 ° C.
- Other important advantages of naphthalene are the good miscibility with other formulation components and the very low springback after pressing, which prevents cracks in the green body. Finally, the removal is made possible at a relatively low temperature, in which the abrasive article is dried anyway and other components of the grinding wheel mixture, such. B. binding components, not yet activated.
- naphthalene as pore formers are its toxic and environmentally hazardous properties. Through an intense and typical odor, it pollutes the production facilities and the exhaust air and the surrounding area. Expenditures for occupational health and environmental protection dominate the corresponding manufacturing steps in the manufacturing process. Furthermore, naphthalene together with air can form explosive mixtures. Accordingly, costly and expensive safety precautions are required.
- the core of the invention lies in the use of the pore-forming agent defined according to the invention, which allows the production of a defined porosity without impairing the structural integrity of the green body.
- the dicarboxylic acids used according to the invention decompose on heating in decomposition products (in particular water and / or carbon monoxide / carbon dioxide), the decomposition process is preferably endothermic and can therefore be performed controlled without it by exothermic reactions to a local overheating of the green body with a possible impairment of the structural integrity can come.
- the pore-forming agent is preferably selected from the group consisting of oxalic acid, malonic acid and mixtures and hydrates of these acids. Particularly preferred is oxalic acid.
- the decomposition temperature of the pore-forming agent is preferably between 70 and 400 ° C.
- the decomposition of the pore-forming agent as well as the removal of the preferably complete or substantially gaseous decomposition products can therefore take place before the actual sintering temperature of the green body is reached.
- pores in the tool should be distributed as homogeneously as possible.
- the density of the pore-forming agent is similar to the density of the remaining constituents of the green body.
- the density of the pore-forming agent may preferably be between 1.5 and 2 g / cm 3 .
- the fraction of the pore-forming agent in the total weight of the green body may preferably be between 2 and 35% by weight, more preferably 2 and 25% by weight, more preferably 10 and 25% by weight, according to the invention.
- the heating In the endothermic decomposition of dicarboxylic acids, significant volumes of gas may be released. In order to release them in a controlled manner and without impairing the green body, it may be preferable to carry out the heating to or above the decomposition temperature of the pore-forming agent with a defined temperature control. Preference is given here to a heating rate of 2 to 40 ° C / h, more preferably 15 to 25 ° C / h. A heating rate in the lower region may be preferred if high pore fractions, such as> 55% by volume, are to be present.
- the pore-forming agent before heating to or above the decomposition temperature of the pore-forming agent additionally heating to a temperature below the decomposition temperature of the pore-forming agent, preferably 30 to 50 ° C, takes place and the green body is held at this temperature for a period of time in particular the evaporation of volatile components such as water or solvent allowed. Preferably, this period is between 24 and 48 h.
- the individual components are preferably combined in the order of abrasive grain, optional deformation aid, binder and pore former and combined to form a homogeneous mixture.
- Decisive for the homogeneity of the distribution of the pore-forming agent and thus of the pores in the final product are not exclusively the type and duration of the mixing process. Rather, it has been found that the density of the pore-forming agent in relation to the density of the other mixture components has a significant influence on the homogeneity of the mixture.
- oxalic acid dihydrate in contrast to naphthalene (1.14 g / cm 3) or wax (0.9 g / cm 3) to 1.65 g / cm 3, a density of the order of substantially mix constituents. Accordingly, a very uniform pore distribution was found in the abrasive bodies of the invention prepared with oxalic acid.
- the density of pure oxalic acid is 1.90 g / cm 3 .
- the weight loss distilled water of crystallization
- the surface of the abrasive article obtained according to Example 1 was divided into 6 different circle segments of 60 ° each. Within these segments, an area of 7 ⁇ 7 mm was selected in each of an inner and an outer area of the circle segment and the number of pores in these areas was counted. A deviation of ⁇ 10% was determined for all 12 surfaces, based on the highest or lowest number of pores determined.
- Oxalic acid dihydrate is plastically deformable in the solid state.
- the plastic deformability largely prevents springback after the shaping of the green body by pressing.
- Conventional compression pressures in this deformation can be in the range of about 30 to 220 bar (preferably based on the side surface of the green body or abrasive body to be produced).
- Strong springback which also affects the density of the fired abrasive article, can lead, for example, to cracks in the green body weakening the strength after removal from the press or after firing
- Decomposition means that the pore-forming agent undergoes a chemical reaction under the action of temperature, whereby at least two different reaction products are formed and these predominantly escape from the green body in a gaseous state.
- a disadvantage of the decomposition of oxalic acid for example compared to the sublimation of naphthalene, is the release of considerable volumes of gas. These can mechanically damage the green body, for example by microcracks, but also by large-scale cracking or structural distortions. As a result, such previously damaged grinding wheels do not have the required strength after firing and can not be used.
- the decomposition products formed in the course of the process behave inertly with respect to all customary formulation components such as abrasives and ceramic binders.
- the proportion of the pore-forming agent in the total weight of the green body is preferably between the two according to the invention 2 and 35 wt .-%, more preferably 2 and 25 wt .-%, more preferably 2 and 20 wt .-%.
- the pore volume of the abrasive article can be adjusted in the range of 30% to 80% total porosity, with the average pore size varying between 0.1 mm and 2.0 mm.
- Oxalic acid dihydrate may cause problems in industrial use. During processing, abrasion and dusts may occur which, on the one hand due to the acid content, are highly corrosive to production plants such as As mixers or molds can act and on the other hand can exert an irritant effect on mucous membranes as inhaled particulate matter. Also problematic when using oxalic acid dihydrate is the fact that when heated at a temperature of 100 ° C, crystal water is released (this temperature is well below the decomposition temperature of oxalic acid of 150 ° C). This release of water of crystallization carries the risk of volume change or cracking of the green body. The use of dried and thus free of crystallized oxalic acid in turn is problematic because on the one hand dried oxalic acid is hygroscopic and on the other hand, the problem of occupational safety (inhalation of dusts) is reinforced.
- a suitable binder can help ensure that the granules have sufficient resistance to crushing by pressure and shear stress. Further, when the granules are dried and water of crystallization of the oxalic acid is expelled, such a binder contributes to preventing or reducing the re-uptake of water.
- Suitable binders for solidifying the oxalic acid may be, for example, polyethylene glycols, polyvinylpyrrolidone or else waxes.
- examples include PEG6000 as a 40% aqueous solution or an aqueous solution of PVP (polyvinylpyrrolidone), for example, used as a 15 to 25% PVP solution.
- the oxalic acid as a whole with such a binder and solidify.
- binders can be used in the production of the green body, which make the abrasive body mass manageable and deformable as a temporary binder (also referred to as deformation aid) and give the green body sufficient strength after drying until the tool is made by burning the green body.
- PF0436SW13 from the company Momentive (temporary binder based on phenolic resin).
- waxes As non-polar substances, waxes have the advantage that they show no changes in their properties due to contact with water. Their properties thus remain unaffected by the processes of mixing, pressing and drying.
- wax is used in the context of the invention as defined in Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, volume A39, page 135 et seq. Particularly suitable within the scope of the invention are waxes which are also oxidized at the decomposition temperature of oxalic acid (about 150.degree C) (the so-called debindering) still effect a sufficient solidification of the green body, so that it retains the intended shape and form during the so-called debindering.
- waxes are, for example, Zusoplast WE52 (Zschimmer & Schwarz, 56108 Lahnstein), various waxes from DEUREX GmbH, 06729 Elsteraue (for example WX9820 (polyolefin wax emulsion), MP2120 (polypropylene wax), MA7020 (ethylene stearamide wax)).
- suitable agents are the polyglycols already described above. They can be used not only for binding or inerting the oxalic acid, but also as a temporary binder in the context of the method according to the invention.
- the pasty mass was placed on sieves of mesh-size 500 microns and 1000 microns and pressed through the mesh with a brush and a soft plastic scraper.
- the mass was previously heated to 100 ° C over 4 h, in order to achieve the desired pasty consistency of the mixture with the then liquid wax.
- the green body is heated at 4 ° C./h to 90 ° C. and further from 90 ° C. to 165 ° C. at 2.5 ° C./h.
- the holding time at 165 ° C is 4 h.
- test abrasives correspond to Examples 3 and 4, Example 3 being an abrasive article of the invention and Example 4 being a prior art abrasive article EP 2 251143 A1 is.
- the modulus of elasticity and the density differ only slightly. The differences are within the usual manufacturing tolerances.
- the grinding wheels were subjected to a grinding test with the following test parameters: grinding machine Blohm HSF 6 with integrated force measuring unit Workpiece surface (width x length)] mm] 10x100 Workpiece material 100Cr6 Workpiece hardness [HRC] 60 +/- 1 Grinding speed [m / s] 33 Workpiece speed [m / min] 20 Delivery per stroke [ ⁇ m] 20 coolant Unimet AS 220 R5% dressing tool CVD Blattabrichter Measurement of tangential and normal forces continuous
Description
Die Erfindung betrifft ein Verfahren zur Herstellung eines porösen Werkzeugs aus gebundenem Schleifmittel.The invention relates to a method for producing a bonded abrasive tool.
Werkzeuge aus gebundenem Schleifmittel finden in der Technik umfangreich Verwendung zur Oberflächenbearbeitung. Solche Werkzeuge sind beispielsweise Schleifscheiben, Schleifsegmente, Schleifstäbe oder Honsteine.Bound abrasive tools are widely used in the art for surface finishing. Such tools are, for example, grinding wheels, abrasive segments, grinding rods or honing stones.
Zur Herstellung eines solchen Werkzeugs wird ein Schleifmittel (beispielsweise Korund, Siliciumcarbid, Diamant oder CBN einer gewünschten Körnung) mit einem Bindemittel (insbesondere einem keramischen Bindemittel), ggf. Additiven und temporären Klebstoffen zu einer Mischung verarbeitet. Diese wird zu einem Grünkörper der gewünschten Form verpresst. Der Grünkörper wird anschließend bei geeigneten Temperaturen getrocknet, ggf. von Porenbildnern befreit und schließlich keramisch gebrannt.To produce such a tool, an abrasive (for example corundum, silicon carbide, diamond or CBN of a desired grain size) is processed into a mixture with a binder (in particular a ceramic binder), if appropriate additives and temporary adhesives. This is pressed into a green body of the desired shape. The green body is then dried at suitable temperatures, optionally freed from pore formers and finally fired by a ceramic.
Abhängig vom Einsatzzweck soll ein solches Werkzeug eine bestimmte Porosität, meist auch eine bestimmte Porenform und - größe aufweisen. Es ist daher bekannt, der Mischung einen Porenbildner (meist Naphthalin) zuzusetzen, der im Grünkörper entsprechende Raumanteile einnimmt. Der Porenbildner wird durch Verdampfen, Sublimieren oder auch durch Verbrennen entfernt. Dies kann während des Sintervorgangs oder in einem zeitlich vorgelagerten Verfahrensschritt bei niedrigeren Temperaturen erfolgen. Insbesondere Naphthalin kann bereits bei verhältnismäßig niedrigen Temperaturen entfernt werden, nämlich durch Sublimation bei ca. 80°C. Weitere wichtige Vorteile des Naphthalins sind die gute Mischbarkeit mit anderen Rezepturkomponenten sowie die sehr geringe Rückfederung nach dem Pressen, wodurch Risse im Grünkörper vermieden werden. Schließlich wird das Entfernen bei einer relativ niedrigen Temperatur ermöglicht, bei der ohnehin der Schleifkörper getrocknet wird und andere Bestandteile der Schleifscheibenmischung, wie z. B. Bindungskomponenten, noch nicht aktiviert werden.Depending on the intended use, such a tool should have a certain porosity, usually also a certain pore shape and size. It is therefore known to add to the mixture a pore-forming agent (usually naphthalene) which occupies corresponding proportions of space in the green body. The pore-forming agent is removed by evaporation, sublimation or by burning. This can be done during the sintering process or in a temporally upstream process step at lower temperatures. In particular, naphthalene can be removed even at relatively low temperatures, namely by Sublimation at about 80 ° C. Other important advantages of naphthalene are the good miscibility with other formulation components and the very low springback after pressing, which prevents cracks in the green body. Finally, the removal is made possible at a relatively low temperature, in which the abrasive article is dried anyway and other components of the grinding wheel mixture, such. B. binding components, not yet activated.
Nachteilig an Naphthalin als Porenbildner sind dessen toxische und umweltgefährdende Eigenschaften. Durch einen intensiven und typischen Eigengeruch belastet es die Fertigungsstätten sowie über die Abluft auch die nähere Umgebung. Die Aufwändungen für Arbeits- Gesundheits- und Umweltschutz dominieren die entsprechenden Fertigungsschritte im Herstellungsprozess. Weiterhin vermag Naphthalin zusammen mit Luft explosionsfähige Gemische zu bilden. Dementsprechend sind aufwändige und kostenintensive Sicherheitsvorkehrungen erforderlich.A disadvantage of naphthalene as pore formers are its toxic and environmentally hazardous properties. Through an intense and typical odor, it pollutes the production facilities and the exhaust air and the surrounding area. Expenditures for occupational health and environmental protection dominate the corresponding manufacturing steps in the manufacturing process. Furthermore, naphthalene together with air can form explosive mixtures. Accordingly, costly and expensive safety precautions are required.
Im Sinne einer Nachhaltigkeit und Ressourceneinsparung wäre es prinzipiell möglich, Naphthalin durch Resublimation aufzubereiten und erneut zu verwenden. Dieses Verfahren ist jedoch unwirtschaftlich, so dass es üblicherweise einer Nachverbrennung zugeführt wird.In terms of sustainability and resource savings, it would be possible in principle to prepare naphthalene by resublimation and reuse it. However, this method is uneconomical, so that it is usually fed to an afterburner.
Aufgrund der gravierenden Nachteile des Naphthalins wurden zahlreiche Versuche unternommen, dieses durch alternative Porenbildner zu ersetzen. Zum Einsatz kamen dabei beispielsweise Granulate von Nussschalen oder von Kunststoffen, Dextrin, Zellulose, Kohle (Petrolkoks oder Aktivkohle), Kakaopulver oder auch Wachse. Abgesehen vom Para-Dichlorbenzol, welches ähnliche - positive wie negative - Eigenschaften wie Naphthalin aufweist, weisen diese Alternativen, bezogen auf die unterschiedlichen Fertigungsschritte, erhebliche, zum Teil mehrere der nachfolgend aufgeführten Nachteile auf:
- Stoffe lassen sich nicht homogen mit der restlichen Schleifkörpermasse vermischen
- Poröse Porenbildner, z.B. Aktivkohle, entziehen der Masse Feuchtigkeit, so dass sich selbst bei einer kurzen Lagerzeit der Mischungen deren Beschaffenheit verändert
- Stoffe enthalten Eisenpartikel, die rotbraune, harte Flecken im gebrannten Schleifkörper hinterlassen
- Stoffe wirken als Trennmittel mit der Folge, dass die hiermit gefertigten Grünlinge keine ausreichende Rohbruchfestigkeit besitzen
- Stoffe bewirken eine Rückfederung nach der Formgebung. Die Grünlinge zeigen unmittelbar nach dem Ausstoßen aus dem Formwerkzeug oder nach kurzer Zeit Risse
- Schmelzfähige Stoffe können zwar durch Verdampfung der flüssigen Phase (also nicht durch Sublimation) entfernt werden, jedoch sind hierzu deutlich höhere Temperaturen als 80°C erforderlich. Ähnlich wie beim Naphthalin können sich dadurch explosionsfähige Gemische bilden
- Die Möglichkeit des Verdampfens von Stoffen im Brennofen erfordert meist eine verlängerte Haltezeit, welche die Produktivität der Brennanlage deutlich senken kann. Weiterhin können sich bei diesem Verfahren explosionsfähige Gemische bilden sowie Mischungskomponenten vorzeitig aktiviert werden.
- Das Verbrennen oder Zersetzen von Porenbildnern im Brennofen kann zu einer derart intensiven Gasentwicklung führen, dass der noch nicht ausreichend feste Grünling während des Brandes gesprengt wird.
- Das Verbrennen von Porenbildnern bewirkt eine zusätzliche Wärmeentwicklung, welche eine lokale Abweichung von der Soll-Temperatur verursachen kann.
- Insbesondere bei voluminösen Schleifkörpern kann lokal ein Mangel an Sauerstoff bestehen mit dem Ergebnis einer unvollständigen Verbrennung. Dadurch verbleiben im Schleifkörper schwarze, kohlenstoffhaltige Reste, welche u. a. die Reinheit und die Schleifleistungen des Schleifkörpers beeinträchtigen.
- Unabhängig von den Bedingungen des Trocknens und Brennens kann die Verwendung von unterschiedlichen Porenbildnern zu veränderten Eigenschaften des Endproduktes führen. So wiesen mit Naphthalin-Ersatzstoffen hergestellte Schleifkörper zum Teil mangelhafte Schleifleistungen und herabgesetzte mechanische Festigkeiten auf.
- Substances can not be homogeneously mixed with the remaining abrasive mass
- Porous pore formers, eg activated carbon, deprive the mass of moisture, so that even with a short storage time of the mixtures changed their nature
- Substances contain iron particles that leave reddish brown, hard spots in the burned abrasive
- Substances act as release agents, with the result that the green compacts produced herewith do not have sufficient raw breaking strength
- Fabrics cause springback after shaping. The green compacts show cracks immediately after ejection from the mold or after a short time
- Although meltable substances can be removed by evaporation of the liquid phase (ie not by sublimation), significantly higher temperatures than 80 ° C. are required for this purpose. As with naphthalene, explosive mixtures can form as a result
- The possibility of vaporizing substances in the kiln usually requires a prolonged dwell time, which can significantly reduce the productivity of the kiln. Furthermore, explosive mixtures can form in this process and mixture components can be activated prematurely.
- The burning or decomposition of pore formers in the kiln can lead to such an intense evolution of gas that the still not sufficiently solid green compact is blasted during the fire.
- The burning of pore formers causes additional heat generation, which can cause a local deviation from the target temperature.
- Particularly with voluminous abrasives may be local lack of oxygen with the result of incomplete combustion. As a result, black, carbonaceous residues remain in the grinding wheel, which, among other things, impair the cleanliness and grinding performance of the grinding wheel.
- Regardless of the conditions of drying and firing, the use of different pore formers can lead to altered properties of the final product. For example, abrasives made with naphthalene substitutes sometimes had poor grinding performance and reduced mechanical strength.
In
Der Erfindung liegt die Aufgabe zugrunde, eine bestimmte Porosität von Schleifkörpern durch ein Verfahren zu erzeugen, das die oben genannten Nachteile überwindet. Maßgeblich ist dabei die weitgehende Vermeidung von toxischen und umweltgefährdenden Risiken ebenso wie teure und komplexe verfahrenstechnische Lösungen. Zugleich soll das Verfahren für ein breites Spektrum an Schleifkörpern einsetzbar sein, ohne dass ein Verlust an schleiftechnischer Leistung ebenso wie an mechanischer Festigkeit in Kauf genommen werden muss.The invention has for its object to produce a certain porosity of abrasive articles by a method which overcomes the disadvantages mentioned above. Decisive here is the avoidance of toxic and environmentally hazardous risks as well as expensive and complex process engineering solutions. At the same time, the process should be usable for a broad spectrum of grinding wheels, without having to accept a loss of grinding performance as well as of mechanical strength.
Gegenstand der Erfindung ist ein Verfahren zur Herstellung eines Werkzeugs aus gebundenem Schleifmittel, mit den Schritten:
- a) Herstellen eines Grünkörpers enthaltend Schleifmittel, Bindemittel und einen organischen Porenbildner;
- b) Erwärmen des Grünkörpers auf eine Temperatur bei oder über der Zersetzungstemperatur des Porenbildners;
- c) Brennen des Grünkörpers zu einem Werkzeug aus gebundenem Schleifmittel.
- a) producing a green body containing abrasives, binders and an organic pore-forming agent;
- b) heating the green body to a temperature at or above the decomposition temperature of the pore-forming agent;
- c) firing the green body to a tool of bonded abrasive.
Erfindungsgemäß ist vorgesehen, dass der organische Porenbildner ausgewählt ist aus der Gruppe bestehend aus Dicarbonsäuren sowie Mischungen und Hydraten der Dicarbonsäuren.According to the invention, it is provided that the organic pore-forming agent is selected from the group consisting of dicarboxylic acids and mixtures and hydrates of the dicarboxylic acids.
Die hier verwendeten Begriffe "Werkzeug aus gebundenem Schleifmittel", "Schleifmittel", "Bindemittel" sowie "Grünkörper" werden in der vorliegenden Anmeldung so verwendet, wie sie dem Fachmann aus dem Stand der Technik geläufig sind.The terms "bonded abrasive tool," "abrasive," "binder," and "green body" as used herein are used in the present application as well known to those skilled in the art.
Der Kern der Erfindung liegt in der Verwendung des erfindungsgemäß definierten Porenbildners, der ohne Beeinträchtigung der strukturellen Integrität des Grünkörpers die Herstellung einer definierten Porosität erlaubt. Die erfindungsgemäß eingesetzten Dicarbonsäuren zersetzen sich beim Erwärmen in Zerfallsprodukte (insbesondere Wasser und/oder Kohlenmonoxid/Kohlendioxid), der Zersetzungsprozess ist vorzugsweise endotherm und kann daher kontrolliert geführt werden, ohne dass es durch exotherme Reaktionen zu einer lokalen Überwärmung des Grünkörpers mit einer möglichen Beeinträchtigung dessen struktureller Integrität kommen kann.The core of the invention lies in the use of the pore-forming agent defined according to the invention, which allows the production of a defined porosity without impairing the structural integrity of the green body. The dicarboxylic acids used according to the invention decompose on heating in decomposition products (in particular water and / or carbon monoxide / carbon dioxide), the decomposition process is preferably endothermic and can therefore be performed controlled without it by exothermic reactions to a local overheating of the green body with a possible impairment of the structural integrity can come.
Der Porenbildner ist bevorzugt ausgewählt aus der Gruppe bestehend aus Oxalsäure, Malonsäure sowie Mischungen und Hydraten dieser Säuren. Besonders bevorzugt ist Oxalsäure.The pore-forming agent is preferably selected from the group consisting of oxalic acid, malonic acid and mixtures and hydrates of these acids. Particularly preferred is oxalic acid.
Die Zersetzungstemperatur des Porenbildners liegt bevorzugt zwischen 70 und 400 °C. Das Zersetzen des Porenbildners sowie das Entfernen der bevorzugt vollständigen oder im Wesentlichen gasförmigen Zersetzungsprodukte können daher vor Erreichen der eigentlichen Sintertemperatur des Grünkörpers erfolgen.The decomposition temperature of the pore-forming agent is preferably between 70 and 400 ° C. The decomposition of the pore-forming agent as well as the removal of the preferably complete or substantially gaseous decomposition products can therefore take place before the actual sintering temperature of the green body is reached.
Der Porenbildner ist im festen Zustand bevorzugt plastisch verformbar und weist keine oder nur eine geringe Rückfederung auf. Auf diese Art und Weise wird vermieden, dass durch eine Rückfederung und damit verbundene Volumenvergrößerung des Porenbildners der Grünkörper beschädigt wird.The pore former is preferably plastically deformable in the solid state and has little or no springback. In this way it is avoided that the green body is damaged by springback and the associated increase in volume of the pore former.
In der Regel sollen Poren in dem Werkzeug möglichst homogen verteilt sein. Zu diesem Zweck ist es erforderlich, den Porenbildner gleichfalls homogen mit den übrigen Mischungsbestandteilen des Grünkörpers zu vermischen. Um hier eine unerwünschte Endmischung weitgehend zu vermeiden, ist es bevorzugt, dass die Dichte des Porenbildners ähnlich der Dichte der übrigen Bestandteile des Grünkörpers ist. Bevorzugt kann die Dichte des Porenbildners zwischen 1,5 und 2 g/cm3 liegen.As a rule, pores in the tool should be distributed as homogeneously as possible. For this purpose, it is necessary to also homogeneously mix the pore former with the remaining mixture components of the green body. In order to avoid an unwanted final mixture to a large extent, it is preferred that the density of the pore-forming agent is similar to the density of the remaining constituents of the green body. The density of the pore-forming agent may preferably be between 1.5 and 2 g / cm 3 .
Der Anteil des Porenbildners am Gesamtgewicht des Grünkörpers kann erfindungsgemäß bevorzugt zwischen 2 und 35 Gew.-%, weiter vorzugsweise 2 und 25 Gew.-%, weiter vorzugsweise 10 und 25 Gew.-% liegen.The fraction of the pore-forming agent in the total weight of the green body may preferably be between 2 and 35% by weight, more preferably 2 and 25% by weight, more preferably 10 and 25% by weight, according to the invention.
Bei der endothermen Zersetzung von Dicarbonsäuren können signifikante Gasvolumina frei werden. Um diese kontrolliert und ohne Beeinträchtigung des Grünkörpers freizusetzen, kann es bevorzugt sein, das Erwärmen auf oder über die Zersetzungstemperatur des Porenbildners mit einer definierten Temperaturführung vorzunehmen. Bevorzugt ist hier eine Aufheizrate von 2 bis 40°C/h, weiter vorzugsweise 15 bis 25°C/h. Eine Aufheizrate im unteren Bereich kann bevorzugt sein, wenn hohe Porenanteile wie beispielsweise > 55 Vol.-% vorliegen sollen.In the endothermic decomposition of dicarboxylic acids, significant volumes of gas may be released. In order to release them in a controlled manner and without impairing the green body, it may be preferable to carry out the heating to or above the decomposition temperature of the pore-forming agent with a defined temperature control. Preference is given here to a heating rate of 2 to 40 ° C / h, more preferably 15 to 25 ° C / h. A heating rate in the lower region may be preferred if high pore fractions, such as> 55% by volume, are to be present.
Erfindungsgemäß kann es vorgesehen sein, dass vor dem Erwärmen auf oder über die Zersetzungstemperatur des Porenbildners zusätzlich ein Erwärmen auf eine Temperatur unterhalb der Zersetzungstemperatur des Porenbildners, vorzugsweise 30 bis 50°C, erfolgt und der Grünkörper bei dieser Temperatur für einen Zeitraum gehalten wird, der insbesondere das Verdunsten flüchtiger Bestandteile wie Wasser oder Lösungsmittel erlaubt. Bevorzugt liegt dieser Zeitraum zwischen 24 und 48 h.According to the invention it can be provided that before heating to or above the decomposition temperature of the pore-forming agent additionally heating to a temperature below the decomposition temperature of the pore-forming agent, preferably 30 to 50 ° C, takes place and the green body is held at this temperature for a period of time in particular the evaporation of volatile components such as water or solvent allowed. Preferably, this period is between 24 and 48 h.
Eine weitere Erläuterung der Erfindung erfolgt nachfolgend an Ausführungsbeispielen, bei denen Oxalsäure als Porenbildner verwendet wird.A further explanation of the invention is given below in exemplary embodiments, in which oxalic acid is used as pore-forming agent.
Die Einzelkomponenten werden vorzugsweise in der Reihenfolge Schleifkorn, fakultativer Verformungshilfsstoff, Bindemittel und Porenbildner zusammengeführt und zu einer homogenen Mischung vereinigt. Maßgeblich für die Homogenität der Verteilung des Porenbildners und damit der Poren im Endprodukt sind jedoch nicht ausschließlich die Art und die Dauer des Mischvorgangs. Vielmehr hat sich herausgestellt, dass auch die Dichte des Porenbildners im Verhältnis zur Dichte der übrigen Mischungskomponenten maßgeblichen Einfluss auf die Homogenität der Mischung hat.The individual components are preferably combined in the order of abrasive grain, optional deformation aid, binder and pore former and combined to form a homogeneous mixture. Decisive for the homogeneity of the distribution of the pore-forming agent and thus of the pores in the final product are not exclusively the type and duration of the mixing process. Rather, it has been found that the density of the pore-forming agent in relation to the density of the other mixture components has a significant influence on the homogeneity of the mixture.
So weist Oxalsäure-Dihydrat im Gegensatz zu Naphthalin (1,14 g/cm3) oder zu Wachs (0,9 g/cm3) mit 1,65 g/cm3 eine Dichte in der Größenordnung von wesentlichen Mischungsbestandteilen auf. Entsprechend wurde bei den mit Oxalsäure hergestellten erfindungsgemäßen Schleifkörpern eine sehr gleichmäßige Porenverteilung festgestellt. Wird die Oxalsäure vor der Verwendung dehydratisiert, beträgt die Dichte reiner Oxalsäure 1,90 g/cm3. Beim Trocknen von Oxalsäuredihydrat zu Oxalsäure beträgt der Gewichtsverlust (entferntes Kristallwasser) 28,6 %.Thus, oxalic acid dihydrate in contrast to naphthalene (1.14 g / cm 3) or wax (0.9 g / cm 3) to 1.65 g / cm 3, a density of the order of substantially mix constituents. Accordingly, a very uniform pore distribution was found in the abrasive bodies of the invention prepared with oxalic acid. When the oxalic acid is dehydrated before use, the density of pure oxalic acid is 1.90 g / cm 3 . When drying oxalic acid dihydrate to oxalic acid, the weight loss (distilled water of crystallization) is 28.6%.
Die Oberfläche des entsprechend Beispiel 1 erhaltenen Schleifkörpers wurde in 6 unterschiedliche Kreissegmente von jeweils 60° aufgeteilt. Innerhalb dieser Segmente wurde jeweils eine Fläche von 7 x 7 mm in einem inneren und einem äußeren Bereich des Kreissegments ausgewählt und Anzahl der Poren in diesen Flächen ausgezählt. Dabei wurde bei allen 12 Flächen eine Abweichung von < 10% festgestellt bezogen auf die jeweils höchste bzw. niedrigste festgestellt Porenanzahl.The surface of the abrasive article obtained according to Example 1 was divided into 6 different circle segments of 60 ° each. Within these segments, an area of 7 × 7 mm was selected in each of an inner and an outer area of the circle segment and the number of pores in these areas was counted. A deviation of <10% was determined for all 12 surfaces, based on the highest or lowest number of pores determined.
Oxalsäure-Dihydrat ist im festen Zustand plastisch verformbar. Die plastische Verformbarkeit verhindert weitgehend eine Rückfederung nach der Formgebung des Grünkörpers durch Verpressen. Übliche Pressdrücke bei dieser Verformung können im Bereich von etwa 30 bis 220 bar (bevorzugt bezogen auf die Seitenfläche des herzustellenden Grünkörpers bzw. Schleifkörper) liegen. Eine starke Rückfederung, die auch die Dichte des gebrannten Schleifkörpers beeinflusst, kann beispielsweise durch Risse im Grünkörper zu einer Schwächung der Festigkeit nach der Entnahme aus der Presse oder nach dem Brand führenOxalic acid dihydrate is plastically deformable in the solid state. The plastic deformability largely prevents springback after the shaping of the green body by pressing. Conventional compression pressures in this deformation can be in the range of about 30 to 220 bar (preferably based on the side surface of the green body or abrasive body to be produced). Strong springback, which also affects the density of the fired abrasive article, can lead, for example, to cracks in the green body weakening the strength after removal from the press or after firing
Oxalsäure spaltet Hydratwasser ab ca. 80°C ab und zersetzt sich bei Temperaturen ab ca. 150°C. Entsprechend erfolgt die Entfernung aus dem Grünkörper in einen Temperaturbereich zwischen 80°C und 230°C. Zersetzung bedeutet, dass der Porenbildner unter Temperatureinwirkung eine chemische Reaktion vollzieht, wobei mindestens zwei unterschiedliche Reaktionsprodukte entstehen und diese überwiegend in gasförmigem Zustand aus dem Grünkörper entweichen.Oxalic acid splits off water of hydration from approx. 80 ° C and decomposes at temperatures above approx. 150 ° C. Accordingly, the removal takes place from the green body in a temperature range between 80 ° C and 230 ° C. Decomposition means that the pore-forming agent undergoes a chemical reaction under the action of temperature, whereby at least two different reaction products are formed and these predominantly escape from the green body in a gaseous state.
Abweichend von den Porenbildnern nach dem Stand der Technik zersetzt sich die Oxalsäure im Verlauf einer endothermen Reaktion. Tabelle 2 verdeutlicht des mit den Messwerten der Thermowaage bzw. der Differenzialthermoanalyse.Unlike the pore formers of the prior art, the oxalic acid decomposes in the course of an endothermic reaction. Table 2 illustrates that with the measurements of the thermobalance or the differential thermal analysis.
Während bei den teilweise oder in Gänze oxidierten Porenbildnern wie z. B. Wachs Energie in Form von Wärme frei wird und damit insbesondere in Teilbereichen des Schleifkörpers die prozessoptimierte Temperaturführung beeinträchtigt, erfolgt die Zersetzung der Oxalsäure als endothermer Prozess. Entsprechend ist die Homogenität der Temperaturverteilung im Brennprozess in allen Phasen gewährleistet.While with the partially or completely oxidized pore-forming agents such as B. wax energy is released in the form of heat and thus impaired in particular areas of the abrasive body, the process-optimized temperature control, the decomposition of oxalic acid takes place as an endothermic process. Accordingly, the homogeneity of the temperature distribution in the firing process is ensured in all phases.
Nachteilig bei der Zersetzung der Oxalsäure, beispielsweise im Vergleich zur Sublimation des Naphthalins, ist das Freiwerden erheblicher Gasvolumina. Diese können den Grünkörper mechanisch schädigen, beispielsweise durch Mikrorisse, aber auch durch großflächige Rissbildung oder strukturelle Aufwerfungen. In der Folge weisen derart vorgeschädigte Schleifkörper nach dem Brennen nicht die geforderte Festigkeit auf und sind nicht verwendungsfähig.A disadvantage of the decomposition of oxalic acid, for example compared to the sublimation of naphthalene, is the release of considerable volumes of gas. These can mechanically damage the green body, for example by microcracks, but also by large-scale cracking or structural distortions. As a result, such previously damaged grinding wheels do not have the required strength after firing and can not be used.
Dieser Nachteil der Oxalsäure als Porenbildner kann durch eine angepasste Temperaturführung, vorzugsweise in einem mehrstufigen Prozess, überwunden werden. Dabei werden die verpressten Grünkörper zunächst über einen Zeitraum von vorzugsweise 24 - 48 h einer Temperatur zwischen ca. 30 und 50° C ausgesetzt. Diese beispielhaft genannte Temperaturführung kann Verwendung finden beim Einsatz eines temporären Binders basierend auf Phenolharz wie beispielsweise dem im nachfolgenden Beispiel 1 genannten temporären Binder (Verformungshilfsstoff) PF0436SW13 der Firma Momentive. Dabei erfährt der Grünkörper bereits einen Gewichtsverlust zwischen 2% und 10% durch das Verdunsten von flüchtigen Bestandteilen wie Wasser oder Lösungsmittel.This disadvantage of oxalic acid as pore-forming agent can be overcome by an adapted temperature control, preferably in a multi-stage process. The pressed green bodies are first exposed to a temperature between about 30 and 50 ° C over a period of preferably 24-48 h. This exemplified temperature control can be used when using a temporary binder based on phenolic resin such as the example mentioned in Example 1 temporary binder (deformation aid) PF0436SW13 company Momentive. In the process, the green body already experiences a weight loss between 2% and 10% due to the evaporation of volatile constituents such as water or solvent.
In einem nachfolgenden Prozessschritt mit höheren Temperaturen erfolgt die Zersetzung der Oxalsäure. Dieser kann separat oder als Teil des Brennvorganges erfolgen. Dabei wird der Grünkörper bis zu einer Temperatur von 400° C mit einer Aufheizrate von 2° C/h bis 40° C/h, vorzugsweise von 20° C/h erhitzt. Das sogenannte Entbindern kann sowohl in einem separaten Trockenofen als auch direkt im Brennofen vor dem Brand erfolgen. Im Rahmen der Erfindung kann es weiter bevorzugt sein, wenn die Aufheizraten während des Entbinderns im kritischen Temperaturbereich 140-160° C (Zersetzungsbereich der Oxalsäure) ≤ 10° C/h, weiter vorzugsweise ≤ 2° C/h betragen.In a subsequent process step with higher temperatures, the decomposition of the oxalic acid takes place. This can be done separately or as part of the burning process. In this case, the green body is heated up to a temperature of 400 ° C at a heating rate of 2 ° C / h to 40 ° C / h, preferably from 20 ° C / h. The so-called debinding can be done both in a separate drying oven as well done directly in the kiln before the fire. In the context of the invention, it may be further preferred if the heating rates during debindering in the critical temperature range 140-160 ° C (decomposition range of oxalic acid) ≤ 10 ° C / h, more preferably ≤ 2 ° C / h.
Eine Aufheizrate von < 20°C ist vorzugsweise bei Schleifkörpern mit Porenvolumen > 55% zu wählen. Als Reaktionsprodukte werden hauptsächlich Wasser, Kohlendioxid und Kohlenmonoxid frei. Das toxische Kohlenmonoxid wird wie alle freiwerdenden Gase beim Trocknungs- und Brennprozess einer Nachverbrennung zugeleitet und in Kohlendioxid übergeführt. Gleiches gilt für weitere Zersetzungsprodukte, die unter veränderten Bedingungen entstehen können.A heating rate of <20 ° C should preferably be selected for abrasive particles with a pore volume> 55%. The reaction products are mainly water, carbon dioxide and carbon monoxide free. The toxic carbon monoxide, like all released gases during the drying and combustion process of an afterburning supplied and converted into carbon dioxide. The same applies to other decomposition products that may arise under changed conditions.
Die Zersetzung erfolgt zu etwa 98% Gew.-%. Die verbleibenden Anteile sind auf Verunreinigungen der technischen Oxalsäure zurückzuführen, sind aber unerheblich für die Eigenschaften des Endproduktes. Wird eine Oxalsäure sehr hoher Reinheit verwendet, so erfolgt eine praktisch vollständige, rückstandsfreie Zersetzung.The decomposition takes place to about 98% by weight. The remaining shares are due to impurities of technical oxalic acid, but are irrelevant to the properties of the final product. If an oxalic acid of very high purity is used, a virtually complete, residue-free decomposition takes place.
Die im Verlauf des Verfahrens entstehenden Zersetzungsprodukte verhalten sich inert gegenüber allen üblichen Rezepturkomponenten wie Schleifmittel und keramischen Bindemitteln.The decomposition products formed in the course of the process behave inertly with respect to all customary formulation components such as abrasives and ceramic binders.
Das im Verfahrenschritt c) genannte Brennen des Grünkörpers zu einem Schleifkörper erfolgt wie im Stand der Technik üblich. Etwaige Restmengen von Porenbildner in dem Grünkörper werden bei diesem Brennvorgang in der Regel verflüchtigt oder zersetzt.The firing of the green body in process step c) to form an abrasive article is carried out as usual in the prior art. Any residual amounts of pore-forming agent in the green body are usually volatilized or decomposed during this firing process.
Der Anteil des Porenbildners am Gesamtgewicht des Grünkörpers (nach dem Verpressen und vor dem Entfernen des Porenbildners aus dem Grünkörper) liegt erfindungsgemäß vorzugsweise zwischen 2 und 35 Gew.-%, weiter vorzugsweise 2 und 25 Gew.-%, weiter vorzugsweise 2 und 20 Gew.-%.The proportion of the pore-forming agent in the total weight of the green body (after pressing and before removal of the pore-forming agent from the green body) is preferably between the two according to the invention 2 and 35 wt .-%, more preferably 2 and 25 wt .-%, more preferably 2 and 20 wt .-%.
Das Porenvolumen des Schleifkörpers kann eingestellt werden in einem Bereich von 30% bis 80% Gesamtporosität, wobei die mittlere Porengröße variieren kann zwischen 0,1 mm und 2,0 mm.The pore volume of the abrasive article can be adjusted in the range of 30% to 80% total porosity, with the average pore size varying between 0.1 mm and 2.0 mm.
Oxalsäure-Dihydrat kann in der industriellen Verwendung unter Umständen Probleme bereiten. Bei der Verarbeitung können Abrieb und Stäube entstehen, die einerseits auf Grund des Säuregehaltes stark korrosiv auf Fertigungsanlagen wie z. B. Mischer oder Pressformen wirken können und andererseits als eingeatmeter Feinstaub eine Reizwirkung auf Schleimhäute ausüben können. Ebenfalls problematisch kann bei der Verwendung von Oxalsäure-Dihydrat die Tatsache sein, dass bei erwärmen bei einer Temperatur von 100°C Kristallwasser frei wird (diese Temperatur liegt deutlich unter der Zersetzungstemperatur der Oxalsäure von 150°C). Diese Freisetzung von Kristallwasser birgt die Gefahr einer Volumenänderung oder Rissbildung des Grünkörpers. Der Einsatz von getrockneter und damit kristallwasserfreier Oxalsäure wiederum ist problematisch, da zum einen getrocknete Oxalsäure hygroskopisch ist und zum anderen die Problematik des Arbeitsschutzes (Einatmen von Stäuben) noch verstärkt wird.Oxalic acid dihydrate may cause problems in industrial use. During processing, abrasion and dusts may occur which, on the one hand due to the acid content, are highly corrosive to production plants such as As mixers or molds can act and on the other hand can exert an irritant effect on mucous membranes as inhaled particulate matter. Also problematic when using oxalic acid dihydrate is the fact that when heated at a temperature of 100 ° C, crystal water is released (this temperature is well below the decomposition temperature of oxalic acid of 150 ° C). This release of water of crystallization carries the risk of volume change or cracking of the green body. The use of dried and thus free of crystallized oxalic acid in turn is problematic because on the one hand dried oxalic acid is hygroscopic and on the other hand, the problem of occupational safety (inhalation of dusts) is reinforced.
Es kann daher erfindungsgemäß vorgesehen sein, dass die Oxalsäure verfestigt wird, damit bei der Handhabung, insbesondere beim Mischen, die Bildung von Feinstaub reduziert wird. Eine solche Verfestigung der Oxalsäure kann durch mechanische Einwirkung wie beispielsweise Verpressen oder Granulieren mittels eines Extruders erfolgen. Oxalsäure kann auf diese Art und Weise beispielsweise granuliert oder in geeignete definierte Form und Größe gebracht werden.It may therefore be provided according to the invention that the oxalic acid is solidified, so that during the handling, in particular during mixing, the formation of fine dust is reduced. Such solidification of the oxalic acid can be carried out by mechanical action such as pressing or granulation by means of an extruder. For example, oxalic acid can be granulated or made into suitably defined shape and size in this manner.
Es ist ferner möglich, die Verfestigung der Oxalsäure durch ein geeignetes Bindemittel zu unterstützen. Ein solches Bindemittel kann dazu beitragen, dass das Granulat eine hinreichende Festigkeit gegen Zerbrechen durch Druck und Scherbelastung aufweist. Wird das Granulat getrocknet und Kristallwasser der Oxalsäure ausgetrieben, trägt ein solches Bindemittel ferner dazu bei, eine erneute Wasseraufnahme zu vermeiden oder zu vermindern.It is also possible to promote the solidification of oxalic acid by a suitable binder. Such a binder can help ensure that the granules have sufficient resistance to crushing by pressure and shear stress. Further, when the granules are dried and water of crystallization of the oxalic acid is expelled, such a binder contributes to preventing or reducing the re-uptake of water.
Geeignete Bindemittel beim Verfestigen der Oxalsäure können beispielsweise Polyethylenglykole, Polyvinylpyrrolidon oder auch Wachse sein. Beispielhaft genannt seien PEG6000 als 40 %ige wässrige Lösung oder eine wässrige Lösung von PVP (Polyvinylpyrrolidon), beispielsweise eingesetzt als 15 bis 25 %ige PVP-Lösung.Suitable binders for solidifying the oxalic acid may be, for example, polyethylene glycols, polyvinylpyrrolidone or else waxes. Examples include PEG6000 as a 40% aqueous solution or an aqueous solution of PVP (polyvinylpyrrolidone), for example, used as a 15 to 25% PVP solution.
Erfindungsgemäß ist es möglich, die Oxalsäure insgesamt mit einem solchen Bindemittel zu mischen und zu verfestigen. Alternativ oder zusätzlich ist es möglich, die Oberfläche von hergestellten Formkörpern der Oxalsäure zu ummanteln und ihnen damit eine zusätzliche Festigkeit gegenüber Abrieb oder Wasserzutritt zu verleihen.According to the invention, it is possible to mix the oxalic acid as a whole with such a binder and solidify. Alternatively or additionally, it is possible to coat the surface of molded bodies of oxalic acid and thus to give them an additional resistance to abrasion or water ingress.
Erfindungsgemäß können bei der Herstellung des Grünkörpers Bindemittel eingesetzt werden, die als temporäre Bindemittel (auch als Verformungshilfstoff bezeichnet) die Schleifkörpermasse handhabbar und verformbar machen und den Grünkörper nach der Trocknung bis zur Herstellung des Werkzeugs durch brennen des Grünkörpers eine hinreichende Festigkeit verleihen.According to the invention, binders can be used in the production of the green body, which make the abrasive body mass manageable and deformable as a temporary binder (also referred to as deformation aid) and give the green body sufficient strength after drying until the tool is made by burning the green body.
Als solche temporäre Bindemittel sind im Stand der Technik insbesondere wasserlösliche Klebstoffe, Dextrinlösungen, flüssige Phenolharze oder Wasserglas in Verwendung.As such temporary binders are in the prior art in particular water-soluble adhesives, dextrin solutions, liquid phenolic resins or water glass in use.
Beispiel für einen solchen Formungshilfstoff ist PF0436SW13 der Firma Momentive (temporärer Binder auf Phenolharzbasis).An example of such a shaping assistant is PF0436SW13 from the company Momentive (temporary binder based on phenolic resin).
Beim Einsatz von dehydratisierter Oxalsäure als Porenbildner kann der Einsatz solcher Verformungshilfstoffe auf Grund der mikroskopischen Eigenschaften der Oxalsäure zu Problemen führen. Es kann dann vorteilhaft sein, Wachse als Verformungshilfstoffe einzusetzen. Wachse haben als unpolare Substanzen den Vorteil, dass sie keine Eigenschaftsveränderungen durch Kontakt mit Wasser zeigen. Ihre Eigenschaften bleiben somit unbeeinflusst durch die Vorgänge des Mischens, Pressens und der Trocknung.When using dehydrated oxalic acid as a pore former, the use of such deformation aids due to the microscopic properties of oxalic acid can lead to problems. It may then be advantageous to use waxes as deformation aids. As non-polar substances, waxes have the advantage that they show no changes in their properties due to contact with water. Their properties thus remain unaffected by the processes of mixing, pressing and drying.
Der Begriff Wachs wird im Rahmen der Erfindung so verwendet wie definiert in Ullmanns Encyclopedia of Industrial Chemistry, 6. Auflage, Band A39, Seite 135 ff. Besonders geeignet sind im Rahmen der Erfindung Wachse, die auch bei der Zersetzungstemperatur von Oxalsäure (etwa 150°C) (der sogenannten Entbinderung) noch eine hinreichende Verfestigung des Grünkörpers bewirken, so dass dieser während der sogenannten Entbinderung die vorgesehene Form und Gestalt beibehält.The term wax is used in the context of the invention as defined in Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, volume A39, page 135 et seq. Particularly suitable within the scope of the invention are waxes which are also oxidized at the decomposition temperature of oxalic acid (about 150.degree C) (the so-called debindering) still effect a sufficient solidification of the green body, so that it retains the intended shape and form during the so-called debindering.
Besonders geeignete Wachse sind beispielsweise Zusoplast WE52 (Zschimmer & Schwarz, 56108 Lahnstein), verschiedene Wachse der Firma DEUREX GmbH, 06729 Elsteraue (beispielsweise WX9820 (Polyolefin-Wachsemulsion), MP2120 (Polypropylenwachs), MA7020 (Ethylen-Stearamid-Wachs)).Particularly suitable waxes are, for example, Zusoplast WE52 (Zschimmer & Schwarz, 56108 Lahnstein), various waxes from DEUREX GmbH, 06729 Elsteraue (for example WX9820 (polyolefin wax emulsion), MP2120 (polypropylene wax), MA7020 (ethylene stearamide wax)).
Weiter geeignete Mittel sind die vorstehend bereits beschrieben Polyglykole. Sie können nicht nur zum Binden bzw. Inertisieren der Oxalsäure, sondern auch als temporärer Binder im Rahmen des erfindungsgemäßen Verfahrens verwendet werden.Further suitable agents are the polyglycols already described above. They can be used not only for binding or inerting the oxalic acid, but also as a temporary binder in the context of the method according to the invention.
- Bakelite PF0436SW13Bakelite PF0436SW13
- Momentive Specialty Chemical GmbH, IserlohnMomentive Specialty Chemical GmbH, Iserlohn
- Deurex MP2120Deurex MP2120
- Deurex Micro Technologies GmbH, ElsteraueDeurex Micro Technologies GmbH, Elsteraue
- Edelkorund-weiß F60, F80Corundum white F60, F80
- Treibacher Schleifmittel,Treibacher abrasive,
- Oxalsäuredihydratoxalic acid dihydrate
- Mudanjiang Fengda Chemicals Corp., HeilongjiangMudanjiang Fengda Chemicals Corp., Heilongjiang
- Polyethylenglycol 300Polyethylene glycol 300
- Merck Schuchardt OHG, HohenbrunnMerck Schuchardt OHG, Hohenbrunn
- Polyethylenglycol 6000Polyethylene glycol 6000
- AppliChem GmbH, DarmstadtAppliChem GmbH, Darmstadt
- Polyvinylpyrrolidonepolyvinylpyrrolidones
- Sigma-Aldrich Chemie GmbH, SteinheimSigma-Aldrich Chemie GmbH, Steinheim
- Siliciumcarbid-grün F240Silicon carbide green F240
- Elektroschmelzwerk, KemptenElectric smelting plant, Kempten
- Vedex KD85Vedex KD85
- SEPT amyl s.r.o, Ostrava-MuglinovSEPT amyl s.r.o, Ostrava-Muglinov
- Zusoplast WE52Zusoplast WE52
- Zschimmer & Schwarz, LahnsteinZschimmer & Schwarz, Lahnstein
Nachfolgend werden 3 Beispiele zur Granulierung von Oxalsäure mit einem Bindemittel beschrieben. Es wurden folgende Ansätze hergestellt:Three examples of granulation of oxalic acid with a binder will now be described. The following approaches were prepared:
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I. 100 g Oxalsäure-Dihydrat
28,4 g Sasolwachs- Entspricht 40 % Sasolwachs (Feststoff) bezogen auf wasserfreie Oxalsäure
28.4 g Sasol wax- Corresponds to 40% Sasol wax (solid) based on anhydrous oxalic acid
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II. 100 g Oxalsäure-Dihydrat
14,2 g Zusoplast WE52- Entspricht 10,0 % Zusoplast (Feststoff) bezogen auf wasserfreie Oxalsäure
14.2 g of Zusoplast WE52- Corresponds to 10.0% Zusoplast (solid) based on anhydrous oxalic acid
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III. 100 g Oxalsäure-Dihydrat
14,2 g Polyvinylpyrrolidone-Lösung (25 %ig)- Entspricht 5,0 % PVP (Feststoff) bezogen auf wasserfreie Oxalsäure
14.2 g polyvinylpyrrolidone solution (25%)- Equivalent to 5.0% PVP (solids) based on anhydrous oxalic acid
Die Ansätze wurden in einem verschlossenen Kunststoffbehälter ca. 1 h lang im Taumelmischer vermischt und anschließend noch einmal per Hand verrührt.The batches were mixed in a sealed plastic container for about 1 h in a tumble mixer and then stirred again by hand.
Danach wurde die pastöse Masse auf Siebe der maschenweiten 500 µm und 1000 µm gegeben und mit einer Bürste und einem weichen Kunststoffschaber durch die Maschen gedrückt.Thereafter, the pasty mass was placed on sieves of mesh-size 500 microns and 1000 microns and pressed through the mesh with a brush and a soft plastic scraper.
Die so erhaltenen Granulate wurden entsprechend der Trockenkurve aus Diagramm 1 (mind, 24 h bei 85 °C) getrocknet.The granules thus obtained were dried according to the dry curve from diagram 1 (at least, for 24 h at 85 ° C.).
Beim Einsatz von Sasolwachs wurde die Masse vorab über 4 h auf 100 °C erhitzt, um mit dem dann flüssigen Wachs die gewünschte pastöse Konsistenz der Mischung zu erreichen.When using Sasol wax, the mass was previously heated to 100 ° C over 4 h, in order to achieve the desired pasty consistency of the mixture with the then liquid wax.
Es zeigte sich, dass so verpresste Oxalsäure bei Einwirkung auf Pressformstahl sowie auf 100 Cr6 binnen 10 Tage bei Raumtemperatur keinerlei korrosive Wirkung auffiel. Hingegen zeigte ein entsprechender Formkörper lediglich aus Oxalsäure-Dihydrat bereits nach 48 h auf beide Stähle korrosive Eigenschaften. Die Figuren 1 und 2 zeigen die Ergebnisse der geschilderten Korrosionsversuche.It was found that such pressed oxalic acid had no corrosive effect on exposure to mold steel and to 100 Cr6 within 10 days at room temperature. On the other hand, a corresponding molding of oxalic acid dihydrate only after 48 h showed corrosive properties on both steels. Figures 1 and 2 show the results of the described corrosion tests.
Es wurden 9 Schleifkörper hergestellt. Die verwendeten Komponenten, die volumetrische Schleifkörperzusammensetzung und physikalische Prüfwerte sind in der Tabelle 1 angegeben. Die Probekörper 1 und 3 wurden folgendermaßen gefertigt:9 wheels were made. The components used, the volumetric abrasive composition and physical test values are given in Table 1. The test specimens 1 and 3 were manufactured as follows:
In einen Labormischer des Typs "Kenwood Major" werden die Rezepturkomponenten in der Reihenfolge Schleifmittel, Befeuchtungsmittel (flüssiges Phenolharz), Porenbildner und Bindemittel eingebracht. Nach Zugabe einer zusätzlichen Komponente wird jeweils die Masse 2 - 5 min vermischt, bis optisch die Homogenität der Masse wahrnehmbar wird.In a "Kenwood Major" type laboratory mixer, the formulation components are added in the order of abrasive, humectant (liquid phenolic resin), pore former, and binder. After addition of an additional component, the mass is mixed for 2 to 5 minutes until the homogeneity of the mass becomes visually perceptible.
Nach Zugabe aller Komponenten wird die Masse 15 min gemischt, durch ein Sieb Maschenweite 2000 µm gestrichen und in eine gehärtete Stahlform gegeben. Die Verpressung zum Grünkörper erfolgt mit einer hydraulischen Presse bis auf das gewünschte Breitenmaß formschlüssig. Dazu waren Drücke erforderlich von ca. 50 bar (Beispiel 2) bis ca. 80 bar (Beispiele 3).After addition of all components, the mass is mixed for 15 min, coated through a sieve mesh size 2000 microns and into a hardened Given steel mold. The pressing to the green body takes place with a hydraulic press up to the desired width dimension form-fitting. For this purpose, pressures were required from about 50 bar (Example 2) to about 80 bar (Examples 3).
Anschließend wurden die Schleifkörper getempert. Die Temperung erfolgte 24 h bei 30°C und weiteren 48 h bei 50°C. Unmittelbar danach (innerhalb von 12 h) wurden die Probekörper im Brennofen aufgebaut und bei einer Maximaltemperatur von 950°C (Probekörper 1) bzw. 1250°C (Probekörper 3) gebrannt. Zu Beginn des keramischen Brandes, also während der Phase des Austreibens der Oxalsäure wurde die Temperatur von Raumtemperatur bis 165 Grad C mit einer Aufheizrate von 3 K /h erhöht, Haltezeit 4 h. Anschließend Erhöhung auf 400°C mit einer Aufheizrate von ca. 20°C/h erhöht.Subsequently, the grinding wheels were annealed. The heat treatment was carried out at 30 ° C. for 24 h and at 50 ° C. for a further 48 h. Immediately thereafter (within 12 h), the specimens were built up in the kiln and fired at a maximum temperature of 950 ° C (specimen 1) and 1250 ° C (specimen 3). At the beginning of the ceramic firing, ie during the phase of expulsion of the oxalic acid, the temperature was increased from room temperature to 165 degrees C at a heating rate of 3 K / h, holding time 4 h. Subsequently increased to 400 ° C with a heating rate of about 20 ° C / h.
Die Probekörper 2 und 5 wurden folgendermaßen gefertigt:
In einen Labormischer des Typs "Kenwood Major" werden die Rezepturkomponenten in der Reihenfolge Schleifmittel, Befeuchtungsmittel (Wachsemulsion Zusoplast WE 58), Porenbildner und Bindemittel eingebracht. Nach Zugabe einer zusätzlichen Komponente wird jeweils die Masse 2 - 5 min vermischt, bis optisch die Homogenität der Masse wahrnehmbar wird.The test pieces 2 and 5 were manufactured as follows:
In a laboratory mixer of the type "Kenwood Major" the formulation components are introduced in the order of abrasives, humidifying agents (wax emulsion Zusoplast WE 58), pore formers and binders. After addition of an additional component, the mass is mixed for 2 to 5 minutes until the homogeneity of the mass becomes visually perceptible.
Nach Zugabe aller Komponenten wird die Masse 15 min gemischt, durch ein Sieb Maschenweite 2000 µm gestrichen. Danach wird die Pressmasse 24 h bei 80°C getempert. Die so getrocknete Pressmasse wird zum Grünkörper mit einer hydraulischen Presse bis auf das gewünschte Breitenmaß formschlüssig gepresst. Dazu waren Drücke erforderlich von ca. 50 bar. Anschließend wurden die Schleifkörper getempert. Die Temperung erfolgte in 2 Stufen. Zuerst wurde der Grünkörper in 2 h auf 80°C erhitzt und dann mit 3°C/h bis auf 165°C weiter erwärmt (Haltezeit 4 h). Bei dieser Temperung wird die Oxalsäure aus dem Grünling entfernt. Danach wurden die Probekörper im Brennofen aufgebaut und bei einer Maximaltemperatur von 950°C gebrannt.After addition of all components, the mass is mixed for 15 min, coated through a sieve mesh size 2000 microns. Thereafter, the molding compound is annealed at 80 ° C for 24 h. The thus dried molding compound is pressed to the green body with a hydraulic press to the desired width dimension form-fitting manner. For this, pressures of about 50 bar were required. Subsequently, the grinding wheels were annealed. The heat treatment took place in 2 stages. First, the green body was heated to 80 ° C in 2 h and then further heated at 3 ° C / h up to 165 ° C (holding time 4 h). at This tempering, the oxalic acid is removed from the green body. Thereafter, the specimens were built in the kiln and fired at a maximum temperature of 950 ° C.
Der Probekörper 4 (Vergleich nach dem Stand der Technik) wurde folgendermaßen gefertigt:The test piece 4 (comparison according to the prior art) was produced as follows:
Eingabe und Mischen der Schleifkörperkomponenten erfolgen wie oben beschrieben. Die dann erhaltene Masse wird durch ein Sieb der Maschenweite 2000 µm gestrichen. Die Masse wird in eine Pressform gegeben und auf das gewünschte Breitenmaß gepresst. Der Pressdruck liegt bei 15 bar.Input and mixing of the abrasive components are as described above. The mass then obtained is passed through a sieve of mesh size 2000 microns. The mass is placed in a mold and pressed to the desired Breitemaß. The pressing pressure is 15 bar.
Der Grünkörper wird auf eine Zelluloseunterlage aufgebracht und getempert bei 100 Grad C und über einen Zeitraum von 48 h. Dabei wird der das Wachs als Porenbildner zu etwa 70% entzogen. Nach dem Abkühlen wird der Grünkörper bei ca. 1250 Grad C gebrannt.The green body is applied to a cellulose pad and annealed at 100 degrees C and over a period of 48 hours. In this case, the wax is withdrawn as a pore-forming agent to about 70%. After cooling, the green body is fired at about 1250 degrees C.
Verfahren wie bei Beispielen 2 und 5, jedoch ohne eine Temperung der Pressmasse.Method as in Examples 2 and 5, but without a tempering of the molding compound.
Weiterhin wird abweichend der Grünkörper mit 4°C /h bis 90°C und weiter von 90°C bis 165°C bei 2,5°C /h erwärmt. Die Haltezeit bei 165°C beträgt 4 h.Furthermore, by way of derogation, the green body is heated at 4 ° C./h to 90 ° C. and further from 90 ° C. to 165 ° C. at 2.5 ° C./h. The holding time at 165 ° C is 4 h.
Verfahren wie bei Beispielen 2 und 5, jedoch ohne eine Temperung der Pressmasse.Method as in Examples 2 and 5, but without a tempering of the molding compound.
Weiterhin wird abweichend der Grünkörper mit 20°C /h bis 140°C und weiter von 140°C bis 165°C bei 2,5°C /h erwärmt. Die Haltezeit bei 165°C beträgt 4 h.Furthermore, deviating from the green body at 20 ° C / h to 140 ° C and further heated from 140 ° C to 165 ° C at 2.5 ° C / h. The holding time at 165 ° C is 4 h.
Unmittelbar danach wurden die Probekörper im Brennofen aufgebaut und bei einer Maximaltemperatur von 950°C gebrannt. Zu Beginn des keramischen Brandes, also während der Phase des Austreibens der Oxalsäure wurde die Temperatur von Raumtemperatur bis 400°C mit einer Aufheizrate von ca. 20°C/h erhöht.
Die Testschleifkörper entsprechen den Beispielen 3 und 4, wobei es sich bei Beispiel 3 um einen erfindungsgemäßen Schleifkörper und bei Beispiel 4 um einen Schleifkörper nach dem Stand der Technik entsprechend
Der E-Modul und die Dichte unterscheiden sich nur geringfügig. Die Unterschiede liegen aber innerhalb der üblichen Fertigungstoleranzen. Die Schleifkörper wurden einen Schleiftest mit folgenden Versuchsparametern unterzogen:
Diagramm 1 zeigt den Verlauf der Schleifnormalkräfte. Die erfindungsgemäß hergestellte Schleifscheibe zeichnet im Vergleich zur Scheibe nach dem Stand der Technik durch deutliche niedrigere Normalschleifkräfte aus. Diagram 1 shows the course of the grinding normal forces. The grinding wheel produced according to the invention is characterized by significantly lower normal grinding forces in comparison with the prior art disk.
Claims (15)
- A method for manufacturing a tool made from bound abrasive agent, having the steps:a) manufacturing a green body containing abrasive agent, binder and an organic pore former;b) heating the green body to a temperature at or above the decomposition temperature of the pore former;c) firing the green body into a tool of bound abrasive agent;characterised in that the organic pore former is selected from the group consisting of dicarboxylic acids and mixtures and hydrates of dicarboxylic acids.
- A method according to claim 1, characterised in that the pore former is selected from the group consisting of oxalic acid, malonic acid and mixtures and hydrates of these acids.
- A method according to claim 1 or claim 2, characterised in that decomposition of the pore former proceeds in an endothermic reaction.
- A method according to one of claims 1 to 3, characterised in that the pore former has a decomposition temperature of between 70 and 400°C.
- A method according to any one of claims 1 to 4, characterised in that the decomposition products of the pore former are completely or substantially gaseous.
- A method according to any one of claims 1 to 5, characterised in that the pore former is plastically deformable in the solid state and exhibits no or only slight recovery.
- A method according to any one of claims 1 to 6, characterised in that the density of the pore former is similar to the density of the other constituents of the green body, preferably lying between 1.5 and 2 g/cm3.
- A method according to any one of claims 1 to 7, characterised in that the proportion of the pore former in the total weight of the green body in step a) of claim 1 is between 2 and 35 wt.%, preferably 2 and 25 wt.%, more preferably 10 and 25 wt.%.
- A method according to any one of claims 1 to 8, characterised in that the heating in step b) of claim 1 proceeds at a heating rate of 2 to 40°C/h, preferably 15 to 25°C/h.
- A method according to any one of claims 1 to 9, characterised in that, prior to the heating in step b) of claim 1, heating additionally takes place to a temperature below the decomposition temperature of the pore former, preferably 30 to 50°C, and the green body is held at this temperature preferably for 24 to 48 h.
- A method according to any one of claims 1 to 10, characterised in that an additional deformation auxiliary is used when manufacturing the green body.
- A method according to claim 11, characterised in that the deformation auxiliary is selected from the group consisting of polyglycols and waxes.
- A method according to any one of claims 1 to 12, characterised in that the dicarboxylic acids are compacted in a step prior to step a) of claim 1.
- A method according to claim 13, characterised in that compaction proceeds by pressing or granulation, preferably using a binder, which is additionally preferably selected from the group consisting of polyglycols, polyvinylpyrrolidones and waxes.
- A method according to claim 14, characterised in that compaction proceeds by pressing or granulation, using a binder which is also used as an additional deformation auxiliary.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP12167847.8A EP2540445B1 (en) | 2011-06-29 | 2012-05-14 | Method of manufacturing a tool made from bound abrasive agents |
PL12167847T PL2540445T3 (en) | 2011-06-29 | 2012-05-14 | Method of manufacturing a tool made from bound abrasive agents |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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EP11171918 | 2011-06-29 | ||
EP12167847.8A EP2540445B1 (en) | 2011-06-29 | 2012-05-14 | Method of manufacturing a tool made from bound abrasive agents |
Publications (2)
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EP2540445A1 EP2540445A1 (en) | 2013-01-02 |
EP2540445B1 true EP2540445B1 (en) | 2013-09-18 |
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EP12167847.8A Active EP2540445B1 (en) | 2011-06-29 | 2012-05-14 | Method of manufacturing a tool made from bound abrasive agents |
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PL (1) | PL2540445T3 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3231558A1 (en) | 2016-04-11 | 2017-10-18 | 3M Innovative Properties Company | A green body, a grinding wheel and a method for manufacturing at least a green body |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CH710934A1 (en) | 2015-04-01 | 2016-10-14 | Reishauer Ag | Open-pored, ceramic-bonded grinding tool, process for its production and pore-forming mixtures used for its production. |
WO2017050755A1 (en) | 2015-09-22 | 2017-03-30 | Reishauer Ag | Method for the production of open-pore, ceramic-bound abrasive tools |
EP3205450A1 (en) * | 2016-02-09 | 2017-08-16 | Hermes Schleifkörper GmbH | Method for producing a ceramic moulded body |
EP3205449A1 (en) | 2016-02-09 | 2017-08-16 | Hermes Schleifkörper GmbH | Method for producing a ceramic moulded body |
CN106041767B (en) * | 2016-07-12 | 2018-07-27 | 广东工业大学 | A kind of resinoid bond super-hard abrasive tool and its manufacturing method and application with interior cooling micro-structure |
US20230083287A1 (en) * | 2020-01-31 | 2023-03-16 | 3M Innovative Properties Company | Bonded abrasive articles and methods of manufacture |
CN114180923B (en) * | 2021-12-29 | 2023-05-16 | 贺州学院 | Baking-free porous ceramsite with layered hierarchical pore structure and preparation method thereof |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AT389883B (en) * | 1986-08-21 | 1990-02-12 | Igel Schleifmittel | ABRASIVE COMPOSITION OR ABRASIVES AND METHOD FOR THE PRODUCTION THEREOF |
DE4133191A1 (en) * | 1991-10-07 | 1993-04-08 | Basf Ag | ABRASIVE |
EP2251143B1 (en) | 2009-05-15 | 2011-11-23 | Hermes Schleifkörper GmbH | Method of manufacturing a tool made from bound abrasive agents |
-
2012
- 2012-05-14 PL PL12167847T patent/PL2540445T3/en unknown
- 2012-05-14 EP EP12167847.8A patent/EP2540445B1/en active Active
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3231558A1 (en) | 2016-04-11 | 2017-10-18 | 3M Innovative Properties Company | A green body, a grinding wheel and a method for manufacturing at least a green body |
Also Published As
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EP2540445A1 (en) | 2013-01-02 |
PL2540445T3 (en) | 2014-02-28 |
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