JPH05187B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to polyvinyl alcohol (PVA)
This invention relates to improvements in porous grinding wheels bonded by a binder mainly composed of acetalized resin. [Prior Art and Problems to be Solved by the Invention] A porous grindstone using a PVA acetalized resin as a binder is highly elastic and has good lapping properties.
However, the machinability is poor, and depending on the conditions, the grindstone may wear out considerably. Another drawback was that water-soluble cutting fluids could not be used because mechanical strength was significantly reduced by water. As a method to compensate for this drawback, it is known to mix an initial condensate of a water-soluble thermosetting resin with PVA in advance and carry out the acetalization reaction. Although this method improves the water resistance of the grinding wheel, it still has poor cutting performance on highly hard work materials, and increasing the mixing ratio of thermosetting resin causes welding (clogging) of metal work materials during grinding. ) occurs, making it impossible to improve machinability. Therefore, in order to satisfy both lapping and cutting properties, it is common to use a grinding wheel that uses as a binder a resin obtained by thermosetting a mixture of PVA resin and an initial condensate of a water-soluble thermosetting resin, and then a water-soluble thermosetting resin. The method was to impregnate the binder with a urea resin or melamine resin, heat cure it, and cover the surface layer of the binder with the urea resin or melamine resin. However, the biggest drawback of this method is that it is practically impossible to impregnate urea resin, melamine resin, or phenolic resin uniformly and evenly into the porous grinding wheel, which not only causes variations in the degree of bonding, but also causes partial impregnation during heat treatment. The hardening phenomenon progressed over time, and cracks or cracks often occurred. An object of the present invention is to solve these problems and provide a high-strength resin-impregnated porous grindstone that has increased cutting performance while maintaining lapping performance. [Means for Solving the Problems] That is, the present invention is characterized in that an impregnating solution consisting of (a) a melamine resin liquid and/or a urea resin liquid, (b) a liquid phenol resin, and (c) a condensation catalyst is formed into a molded solid. The above object is achieved by a resin-impregnated porous flexible grindstone, which is obtained by impregnating a porous base grindstone with high elasticity and reacting it by heating after drying. That is, the resin-impregnated porous flexible whetstone of the present invention provides an excellent finishing whetstone that has both lapping properties (i.e., based on flexibility) and cutting properties, which were conventionally considered difficult to match. do. [Preferred Embodiments and Effects] The components of the impregnating solution used in the present invention are individually known substances, but impregnation with a single system of melamine resin, urea resin, or phenolic resin, which has been attempted in the past, cannot solve the problem. If problems such as uneven adhesion, uneven curing, or cracking occur when using melamine resin/phenolic resin, urea resin/phenolic resin, or a combination of the three, uniform impregnation can be achieved without separation of liquid components. The impregnating solution has excellent flexibility after drying, and has the remarkable effect of solving cracking during heat treatment. The melamine resin of the present invention is an initial condensate of melamine and aldehydes or a derivative thereof, and includes various methylolmelamines, condensates thereof, and alkylated products thereof. Urea resins are initial condensates of urea and aldehydes and their derivatives, such as monomethylol urea, dimethylol urea, methylol ethylene urea, methylol triamine,
Includes dimethylol dihydroxyethylene urea, tetramethylol acetylene diurea, dimethylol uron, dimethylol propylene urea, and alkylated compounds thereof. Liquid phenolic resins include various phenols such as phenol, xylenol, cresol, and resorcinol, as well as formaldehyde, acetaldehyde,
It refers to low-molecular condensates with various aldehydes such as crotonaldehyde, benzaldehyde, and furfural, and derivatives thereof, which are liquid at normal impregnation treatment temperatures. The derivatives include, for example, alkyd-modified resins esterified with phthalic anhydride, hydrocarbon-modified resins, epoxy-modified resins, phenol ether-modified resins, and the like. All of these resins are preferably low molecular weight and liquid, but emulsion (resin content approximately 80% by weight)
(preferably). Also, powdered material is made into a solution of alcohol etc. (resin content: approx. 40%
~60% by weight is preferred) may be used. The weight ratio of each synthetic resin liquid is (a)/(b) from 10/1 to
1/10, and sufficiently uniform impregnation cannot be obtained at blending ratios other than the above (a)/(b). As long as the blending ratio is within the above range, it can be changed according to the requirements of the intended product. For example, when grinding with a relatively hard bonded grindstone is required, a large amount of melamine resin or urea resin is used, and on the other hand, when elasticity and wrapping properties are particularly important, a large amount of phenolic resin is used. The blending ratio (a)/(b) is preferably 1 to 10/1. Water resistance is greatly improved in both cases by uniform impregnation. An impregnating solution of melamine resin blended with phenolic resin has increased flexibility and significantly reduces cracking during ripening compared to the case of melamine resin alone. The same thing can be said when using a urea resin. For impregnation purposes, the viscosity of the impregnation solution is kept as low as possible for impregnation, and if necessary the viscosity is adjusted by dilution or the like. The concentration of this impregnating solution depends on the concentration of each solution (a) (melamine resin solution, urea resin solution, or a mixture thereof) or solution (b) (liquid phenolic resin) itself, or depending on the concentration of solutions (a) and (b). The amount can be adjusted by appropriately diluting the mixture after mixing. The diluent or solution suitable as a solvent for resin (a) (melamine resin, urea resin, or a mixture thereof) or resin (b) (liquid phenolic resin) is one that can dissolve the resin and is decreases the viscosity of
It is preferable to use a material that can be evaporated at a temperature of 40 to 100° C. and does not react with the components of the base grindstone. The amount of impregnation is determined depending on the purpose, but generally corresponds to 1 to 5 times (by weight) the resin binder of the porous base grinding wheel, but is preferably in the range of 1 to 2 times. The condensation catalyst is a known one, and acids, alkalis, or inorganic salts thereof are used. For example, hydrochloric acid, sulfuric acid, phosphoric acid, para-toluenesulfonic acid, sodium hydroxide, ammonium chloride, magnesium chloride, etc. are used. The solidified grindstone is held immersed in this impregnating solution, and then heated to a predetermined temperature and subjected to a heat reaction treatment. The whetstone taken out from the impregnating liquid is usually heated to 40℃~
Drying at a temperature of 100°C, the impregnating liquid gels and becomes fixed to the porous binder surface layer of the grindstone. Heat curing is performed at 40°C to 200°C. The temperature for this heating reaction treatment is selected depending on the type and size of the grinding wheel used as the material, and the type and component ratio of the resin used. Generally, at high temperatures of 150 to 180℃, approximately 5 to
10 hours, at a relatively low temperature of 100 to 130℃, approximately 12 to
Heat treatment is possible in 15 hours. These treatments can also be carried out under pressure. The resin-impregnated solution of the present invention is suitable for porous grindstones having elasticity, but for example, an initial condensate of a water-soluble thermosetting resin is mixed with PVA, and an acetalization reaction, particularly preferably a formalization reaction, is carried out. It is particularly well suited for grinding wheels obtained by It can also be applied to porous whetstones using a binder mainly made of PVA acetalized resin and general porous resinoid whetstones. Depending on the requirements of the target product, the abrasive grains of the above-mentioned base material whetstones are adjusted to #320 to #400.
Wrapping properties are maximized when the following fine particles are used. [Effects of the Invention] The elastic grindstone impregnated with the resin impregnation solution of the present invention does not break during heat treatment, and the final product has significantly improved strength and water resistance, and has excellent grindability and
Abrasion resistance is also improved. Moreover, the wrapping property still maintains a considerable level. By impregnating an elastic porous grindstone with the resin-impregnated solution of the present invention, a grindstone with special lapping properties and a predetermined grinding property can be obtained, which can be used not only for general grinding work but also for lapping machines using the grindstone. This has the advantage that a grindstone that can be used in a wide range of variations, such as work in Examples are shown below. Example 1 Abrasive material GC#1000 10Kg and PVA resin (polymerization degree 500)
Using a mixture of 1500g and 1200g of water-soluble thermosetting resin, a formalization reaction is performed according to the conventional method and hardened to create an elastic porous base grindstone (outer diameter 305 x thickness 20 x hole diameter 152.4 mm) ) was obtained in a predetermined number. As an impregnation solution, 30% by weight of melamine resin (resin content: 80% by weight) and water-soluble phenolic resin (resin content: 60% by weight) were used.
(% by weight) and 70% by weight to obtain an aqueous solution with a total concentration of 50% by weight, to which was added a 0.5% by weight aqueous solution of para-toluenesulfonic acid (concentration 10%) as a condensation catalyst. The base material grindstone was immersed in this impregnating solution, and after being taken out and dried at 60℃,
C. for 7 hours to obtain an impregnated porous grindstone. A grinding test was conducted on this grindstone under the following grinding conditions, and the results are shown in Table 1. Compared to the one before treatment, the amount of wear on the grinding wheel is 0.7 times, and the amount of grinding is 3
4 times the grinding ratio.

[Table] (Note) However, the grinding ratio is the ratio of the amount of grinding to the volume of the worn wheel. Grinding conditions (1) Grinding method Cylindrical plunge (2) Grinding wheel dimensions Outer diameter 305 x thickness 40 x hole diameter 152.4 mm (3) Cover Cutting material S45 (raw material) 60φ×501mm (4) Grinding wheel width 20mm (5) Grinding fluid Water-soluble grinding fluid W ₂ (6) Peripheral speed of grinding wheel 2000m/min (7) Work rotation speed 250m/min (8) Cutting speed 1.2μm/rev (9) Spark-out time 20sec

[Table] Comparative Example 1 Using the same phenolic resin as in Example 1, the base grindstone obtained in Example 1 was impregnated as an impregnation solution with a total concentration of 50% by weight, and heat-cured at 180°C for 5 hours. , a whetstone of Comparative Example 1 was obtained. The results are shown in Tables 1 and 2. The impregnation was extremely uneven, with some parts being extremely hard and uneven, causing scratches during grinding. Comparative Example 2 Using the same melamine resin as Example 1, the total concentration
The impregnation solution was 50% by weight, and the heat treatment was carried out at 150℃ x 10
An impregnated whetstone of Comparative Example 2 was obtained in the same manner as in Comparative Example 1 except for the time. The results are shown in Table 2.
Many cracks occurred during the ripening process and the product was defective. Example 2 Consisting of 30% by weight of urea resin (urea-melamine-formalin initial condensate, active ingredient 25%, PH7.0-8.0), balance phenolic resin (same as Example 1),
An impregnating solution (total concentration: 40% by weight) containing the same condensation catalyst was prepared, and then a base grindstone was impregnated in the same manner as in Example 1, dried, and heated at 150° C. for 8 hours. This grindstone was tested and the results are shown in Table 2, and it was found to be good. Comparative Example 3 Single urea resin (same as Example 2, concentration 5%)
When the impregnating treatment was carried out in the same manner as in Example 2 using the impregnating solution described above, cracks occurred in all of the specimens during the aging treatment, and they could not be used as grindstones. (Second
(See table) Example 3 Using the melamine resin, urea resin, and phenol resin used in Examples 1 and 2, the impregnation solutions of Examples 1 and 2 were mixed at a ratio of 1:1 (weight ratio) to prepare an impregnation solution.
Other than that, impregnation treatment was carried out in the same manner as in Example 1, and the temperature was 170°C.
A grindstone was obtained by heat treatment for 6 hours. The results are shown in Table 2.

Claims (1)

[Scope of Claims] 1. An elastic porous base formed by molding and solidifying an impregnating solution consisting of (a) a melamine resin liquid and/or a urea resin liquid, (b) a liquid phenolic resin, and (c) a condensation catalyst. Impregnate the material whetstone,
A resin-impregnated porous flexible whetstone made by reacting by heating after drying. 2. The porous grindstone according to claim 1, wherein the porous base grindstone having elasticity is a porous grindstone bonded with a binder mainly composed of an acetalized resin of polyvinyl alcohol. 3. The porous grindstone according to claim 2, wherein the binder is made by mixing and condensing an initial condensate of a water-soluble thermosetting resin with a polyvinyl alcohol resin.