COATED ABRASIVE DISKAND PREPARATION THEREOF

FIELD OF THE INVENTION

The present invention relates to a glass fiber paper layer- containing coated abrasive disk which has improved flexibility, dimensional stability, and rotation failure resistance, and a method for preparing said coated abrasive disk.

BACKGROUND OF THE INVENTION

Conventional coated abrasive disks comprising a vulcanized fiber substrate shown in FIG. 1 are prepared by coating an adhesive resin on the vulcanized fiber substrate to form a first adhesive layer, spreading a layer of an abrasive material thereon, pre-drying, coating the abrasive layer with a second layer of an adhesive resin and drying the coated layer.

However, the coated abrasive disk thus obtained has problems in that its shape may become distorted by heat during the drying process, and its impact strength is poor. Therefore, the above conventional method requires post-treatment steps, i.e., humidification and aging steps, to impart dimensional stability and impact resistance to the final abrasive disk.

Accordingly, in order to prepare a coated abrasive disk without a humidification-treatment, Korean Patent No. 10-046922 discloses a method for preparing a coated abrasive disk by coating an adhesive on a back pad disk comprised of a non-woven fabric and a layer of textile (a layer of carbon fiber textile, a layer of glass fiber textile, or a stack thereof), and bonding the back pad to a coated abrasive layer comprising a backsheet and a layer of an abrasive material, followed by heat-pressing.

The coated abrasive disk prepared by such a method, shown in FIG. 2, exhibits relatively good properties in terms of dimensional stability and rotation failure resistance. However, it suffers from poor flexibility and a high manufacturing cost.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide a coated abrasive disk which has improved flexibility, dimensional stability, and rotation failure resistance, and a method for preparing said coated abrasive disk.

In accordance with one aspect of the present invention, there is provided a coated abrasive disk which comprises:

(1) a non-woven fabric; (2) at least one impregnation-treated glass fiber paper layer obtained by impregnation treating a glass fiber paper made of a mixture of glass fibers and wood fibers with a resin; and

(3) a coated abrasive layer having a backsheet to be bonded to the impregnation-treated glass fiber paper layer and a layer of an abrasive material coated on the surface opposite to the backsheet, wherein the non- woven fabric, the glass fiber paper layer and the coated abrasive layer are sequentially stacked and tightly bonded together.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of the invention, when taken in conjunction with the accompanying drawings, which respectively show:

FIGs. 1 and 2: schematic diagrams of conventional coated abrasive disks;

FIG. 3 : a schematic diagram of a glass fiber paper layer-containing coated abrasive disk in accordance with the present invention;

FIG. 4: a schematic diagram of a coater which is used in impregnation-treatment of a substrate with a resin; and FIG. 5: a schematic diagram of a steel holder which is used in the preparation of the inventive coated abrasive disk.

100 : non-woven layer

110 : glass fiber paper layer

120 : coated abrasive layer

122 : backsheet 124 : first adhesive layer

126 : abrasive material 128 : second adhesive layer 130 : carbon fiber textile layer 140 : third adhesive layer

150 : vulcanized fiber substrate 160 : glass fiber textile layer 170 : drier

DETAILED DESCRIPTION OFTHE INVENTION

The coated abrasive disk of the present invention has a structure comprising one non-woven fabric; at least one glass fiber paper layer impregnation-treated with a resin; and one coated abrasive layer which are sequentially stacked and combined tightly together. Such an inventive coated abrasive disk is illustrated in FIG. 3.

The non-woven fabric which is used in the present invention may have a specific weight of 20 to 30 g/m ² , a thickness of 0.1 to 0.3 mm, and a flat or embossed shape. The glass fiber paper which is employed in the present invention is made of a mixture of 70 to 90% by weight, preferably 70 to 80% by weight of glass fibers and 10 to 30% by weight, preferably 20 to 30% by weight of wood fibers, and it may be prepared by a conventional sheet manufacturing process using 5 to 10 mm-long glass fiber fragments having a thickness of 5 to 20 μm together with a wood fiber powder.

The glass fiber paper is also impregnation-treated with an adhesive resin and is pre-dried. The adhesive resin may be incorporated into the textile in an amount ranging from 90 to 200 g/m ² . The pre-drying of the impregnation-treated glass fiber paper may be performed at a temperature ranging from 80 to 100 ^° C for 1 to 3 min. The glass fiber paper before impregnation-treatment with the resin may have a specific weight of 45 to 80 g/m ² and a thickness of 0.25 to 0.65 mm, and it is preferably of a flat shape. Representative examples of the adhesive resin employed in the

impregnation-treatment of the glass fiber paper include a phenol resin, epoxy resin, urea melamine, polyester resin, polyvinyl butyral, acrylonitrile- butadiene-rubber latex, degenerated heat-curable resin, and a mixture thereof. A suitable phenol resin is of a resole-type having a solid content of 40 to 60 % by weight and a viscosity of 400 to 700 cps at 25 ^° C . A schematic diagram of a coater which is used in impregnation-treating the glass fiber paper with a resin is shown in FIG. 4.

The glass fiber paper confers on the final coated abrasive disk improvements in flexibility, dimensional stability, and rotation failure resistance, and it also makes it possible to reduce the manufacturing cost.

The coated abrasive layer which is employed in the present invention may be a conventional one comprising a backsheet and a layer of an abrasive material stacked thereon. Suitable for use as the backsheet are cotton textiles, polyester textiles, rayon textiles, polyester/cotton mixed textiles and polyester film (PET film), while particles of alumina (Al ₂ O ₃ ), silicon carbide (SiC), alumina zirconia (AZ), ceramics (sol-gel), CBN (cubic boron nitride), diamond and a mixture thereof are preferred as the abrasive material.

The coated abrasive disk of the present invention is manufactured by sequentially placing a non-woven fabric, at least one glass fiber paper impregnation-treated with a resin, and a coated abrasive layer in the steel holder shown in FIG. 5, applying a pressure of 5 to 7 kgf/cm ² to the resulting stack of layers, and heating the pressed stack in an oven at 120 to 150 ^° C for 5 to 8 hrs to allow the resin impregnated in the glass fiber paper to melt, resulting in the fusion of the component layers. In the above procedure, the backsheet of the coated abrasive layer is brought into contact with the glass fiber paper. The non-woven fabric, glass fiber paper layer and coated abrasive layer are each pre-cut in the form of a disk.

The inventive glass fiber paper layer-containing coated abrasive disk shows improved flexibility, dimensional stability, and rotation failure resistance. In addition, the inventive disk is sufficiently light to provide enhanced handling characteristics. The manufacturing cost of the inventive disk is much lower as compared as conventional disks. Thus, the inventive disk is useful for various

applications including removal of rust, removal of old car paint, and grinding of metal welding sites and cutting sites.

The following Examples and Comparative Examples are given for the purpose of illustration only, and are not intended to limit the scope of the invention.

Example 1

Cut into a disk form having an outer diameter of 180mm and an inner diameter of 23 mm were: a 25 g/m ² non-woven fabric (commercially available from Doraei Saehan Company) having a thickness of 0.15 mm; a processed glass fiber paper (commercially available from Korea Carbon Company); and a coated abrasive layer P628 #36 Ywt (commercially available from Sun Abrasives Co. Ltd.,). The processed glass fiber paper was prepared by impregnation-treating with a phenol resin an untreated glass fiber paper (thickness: 0.28mm, specific weight: 45 g/m ² ) made of a mixture of 80% by weight of 10 jum-thick glass fibers and 20% by weight of powdered wood fibers (commercially available from Kolon) and pre-drying the treated glass fiber paper at 90 ^° C for 1 min.

The non-woven fabric, glass fiber paper impregnation-treated with a phenol resin, and coated abrasive layer were sequentially stacked from the bottom in a steel holder (FIG. 5), pressed at a force of 6.0 kgf/cm ² , and the pressed stack was heated at 145±5 ^° C for 5 hrs to combine them tightly together, to obtain the coated abrasive disk in accordance with the present invention (see FIG. 3). In the above procedure, the abrasive material layer of the coated abrasive layer was placed on the top of the stack, facing upwards.

Example 2

The procedure of Example 1 was repeated except that one glass fiber paper prepared by impregnation-treating an untreated glass fiber paper (thickness: 0.35 mm, specific weight: 60 g/m ² )(commercially available from Korea Carbon Company) with a phenol resin and pre-drying at 90 ^° C for 1.5 min was used, to obtain another inventive coated abrasive disk. The amount of the phenol resin incorporated into the glass fiber paper was 120 g/m ² .

Example 3

The procedure of Example 1 was repeated except that one glass fiber paper prepared by impregnation-treating an untreated glass fiber paper (thickness: 0.6 mm, specific weight: 80 g/m ² )(commercially available from Korea Carbon Company) with a phenol resin and pre-drying at 90 ^° C for 2 min was used, to obtain another inventive coated abrasive disk. The amount of the phenol resin incorporated into the glass fiber paper was 200 g/m ² .

Example 4

The procedure of Example 1 was repeated except that two glass fiber papers were used, to obtain another inventive coated abrasive disk.

Comparative Example 1 A 1.0 mm-thick vulcanized fiber substrate (commercially available from Toyo Fiber Company, Japan) was cut into a disk form having an outer diameter of 180 mm and an inner diameter of 23 mm.

On the cut vulcanized fiber substrate, a first adhesive of a mixture of phenol resin and CaCO ₃ (50:50 weight ratio) was coated in an amount of 245 g/m ² . An abrasive material (size #36) of a Al ₂ O ₃ /alumina zirconia 40/60 mixture was spread thereon in an amount of 860 g/m , and dried in an oven of 60 to 120 ^° C for 70 minutes. Then, a second adhesive of a mixture of phenol resin and CaCO ₃ (40:60 weight ratio) was coated on the abrasive material formed on the substrate in an amount of 450 g/m ² , and dried and cured in an oven of 60 to 110 ^° C for 240 min, to form the coated abrasive disk (see FIG. 1).

Then, water was spread on the exposed surface of the vulcanized fiber substrate with a brush and left for 7 days within an aging room kept at a temperature ranging from 30±2°C and a relative humidity ranging from 70 to 80%, to prepare a conventional humidification-treated coated abrasive disk.

Comparative Example 2

Cut into a disk form having an outer diameter of 180 mm and an inner diameter of 23 mm were: a 25 g/m ² non-woven fabric (commercially available from Doraei Saehan Company) having a thickness of 0.15 mm; a glass fiber textile (commercially available from Korea Fiber Company) composed of H45 1/4 X H45 1/4 (warp X fill) tex/yarn fibers (H means that average diameters of the fibers are in the ranges of 10.16 to 11.42 μm) and having a leno plain fabric pattern of 8 X 8 (warp X fill) count/inch; a carbon fiber textile (commercially available from Korea Fiber Company) composed of G75 1/0 X E225 1/0 (warp X fill) tex/yarn fibers (E and G mean that average diameters of the fibers are in the range of 6.35 to 7.61 μm and 8.89 to 10.15 μm, respectively) and having a satin fabric pattern of 58 X 30 (warp X fill) count/inch; and a coated abrasive layer P628 #36 Ywt (commercially available from Sun Abrasives Co. Ltd.,). The glass and carbon fiber textiles had been dried after the treatment with a phenol resin.

The non-woven fabric, glass fiber paper impregnation-treated with a phenol resin, and coated abrasive layer were sequentially stacked from the bottom in a steel holder (FIG. 5), pressed at a force of 6.0 kgf/cm ² , and the pressed stack was heated at 145±5 ^° C for 5 hrs to combine them tightly together, to obtain another conventional coated abrasive disk. In the above procedure, the abrasive material layer of the coated abrasive layer was placed on the top of the stack, facing upwards.

Characteristics Test The performance characteristics of the respective coated abrasive disks obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were measured to determine the tensile strength, rotation failure resistance, flexibility, dimensional stability and weight. The results are shown in Table 1 with the relative cost.

Table 1

Note:

* 1 : Tensile strength-measuring instrument - LLOYD Instruments type LR5R

*2 : The rotation number at which a coated abrasive disk is broken *3 : Pliableness <--- -—I -> Stiffness

1 5 10

*4 : The shape of a coated abrasive disk when kept at 30±2 °C and a relative humidity of 70 -80% for 1 week

As can be seen from Table 1, the inventive coated abrasive disks of

Examples 1 to 4 exhibit improved properties in terms of rotation failure resistance, flexibility and/or dimensional stability, as compared to the conventional abrasive disks of Comparative Examples 1 and 2. Further, the manufacturing cost of the inventive coated abrasive disks is lower by 15 to 20% than that of the conventional disks.

As described above, the inventive coated abrasive disk exhibits improved flexibility, elasticity, dimensional stability, and rotation failure resistance, and it is light and inexpensive to manufacture. Thus, the inventive disk is useful for various applications including removal of rust, removal of old car paint, and grinding of metal welding sites and cutting sites.

While the invention has been described with respect to the above

specific embodiments, it should be recognized that various modifications and changes may be made to the invention by those skilled in the art which also fall within the scope of the invention as defined by the appended claims.