JPH0529817Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an abrasive paper disc, more specifically, it has high bending strength and flexibility, does not sag,
This is a new product that can prevent the risk of the abrasive grains and part of the substrate to which the abrasive grains are bound coming off and scattering during use, and also enables high-speed grinding work, greatly improving workability. This paper relates to a ground paper disk having a similar structure.

[Problems to be solved by conventional techniques and inventions] At shipyards, before the hull is painted, rust removal work is performed on the hull. For this work, a grinding paper disc with abrasive grains bonded with resin to the surface of a substrate made of a circular vulcanized fiber board is used. For example, this paper disc is attached to a portable sander and rotated at high speed. This is carried out by pressing the abrasive grain surface of the disc against the part of the workpiece to be ground.

Conventionally used abrasive paper discs have abrasive grains directly bonded to the surface of a circular substrate with a resin, and such abrasive paper discs are generally manufactured as follows.

First, as a substrate, a vulcanized fiber board specified by JIS C 2315 is commonly used.
This paper is made by layering multiple sheets of thin fiber paper that have been soaked in a concentrated zinc chloride solution to harden the surface, washed with water, pressed together while still wet, and dried. The thickness of the grinding paper disk used is usually about 0.8 to 1.2 mm.

A resin liquid, which is a mixture of a thermosetting resin such as a resol-type phenolic resin and an extender such as charcoal, is applied to the surface of this substrate. Then, an appropriate amount of abrasive grains are sprinkled on top of this resin liquid. SiC abrasive grains have traditionally been widely used as abrasive grains, but recently, harder grains such as Al ₂ O ₃ abrasive grains and ZrO ₂ abrasive grains have begun to be used. In addition, the grain size of the abrasive grains is selected depending on the object to be ground and the purpose of grinding, and is usually No. 12 or more as specified in JIS R6111.
It is about No.24.

Next, the above-mentioned thermosetting resin is further applied onto the dispersed abrasive grains, and finally the whole is heated at a temperature of about 60 to 180°C to completely cure the thermosetting resin.
Binds the abrasive grains.

Conventional abrasive paper disks manufactured in this manner have the following problems. The first problem is that the grinding paper disc has low bending strength, so when an operator presses the grinding paper disc against the area to be ground.
The bent disk does not restore its original shape and becomes so-called flattened, and the peripheral edge of the disk peels off and falls off together with the abrasive grains. The resulting grinding disk is
Since the peripheral edge of the disk cannot be used effectively, it is extremely difficult or impossible to grind small recesses, corners, etc. of the object to be ground.

The second problem is that as abrasive grains tend to have higher hardness, part of the paper layer at the periphery of the vulcanized fiber plate of the substrate of the grinding paper disc peels off. In the case of SiC abrasive grains, the abrasive grains themselves are relatively fragile, so during work, the abrasive grains themselves are destroyed, and the torque generated during high-speed rotational grinding is absorbed by the grinding paper disk. was. However, if the abrasive grains are made of Al ₂ O ₃ or ZrO ₂ with higher hardness, the abrasive grains themselves will not be destroyed, so the torque generated during grinding will be transferred directly to the grinding paper disk. It will be accumulated. As a result, two to three paper layers on the surface layer of the peripheral edge of the substrate are partially peeled off and scattered as blocks. This tendency becomes greater as the abrasive grains of high hardness are more firmly bound, and as the rotational speed of the grinding paper disc is increased (grinding efficiency is increased). Such a situation not only reduces work efficiency during grinding, but also poses a great danger to the operator.

The object of the present invention is to provide a ground paper disc that solves the above-mentioned problems.

[Means for solving the problem] The ground paper disk of the present invention has a glass fiber mesh with a mesh size of 1.5 mm x 1.5 mm to 5 mm x 5 mm on the surface of a substrate made of circular vulcanized fibers. This is an abrasive paper disc which is bonded with a thermosetting resin and further has abrasive grains bonded thereon with the thermosetting resin via a glass fiber mesh to form a thin abrasive grain layer.

As shown in a partial cross-sectional view in FIG. 1, the abrasive paper disc of the present invention has a three-layer structure comprising a circular substrate 1, a glass fiber mesh 2 existing on the surface of the substrate, and a thin abrasive grain layer thereon. These are bound together with a thermosetting resin 4.

First, the circular substrate 1 is made of a vulcanized fiber plate, and its shape and thickness are appropriately determined depending on the intended use of the manufactured ground paper disk.

A layer of glass fiber mesh 2 is formed on the surface of this substrate 1. The mesh increases bending strength and flexibility, and particularly serves to reinforce against peeling of the substrate. Further, the resin 4 impregnated into the voids of the mesh firmly binds the mesh 2 and the abrasive grains 3 to the substrate. If the adhesiveness of the resin used is poor and the glass fiber mesh is not firmly bonded, it will lose its useful function as a reinforcing material against peeling, and if there are parts of the mesh that are not bonded, it may be used. Sometimes it becomes a breaking point based on the generated torque.

Glass fiber mesh 2 has a fiber diameter of 0.1 to 1.5 mm and a mesh size of 1.5 mm.
Those with a size of 1.5 mm to 5 mm x 5 mm have a large reinforcing effect and are effective. In particular, the size of the mesh is selected appropriately in relation to the particle size of the abrasive grains used, but as mentioned above, for abrasive grains No. 12 to No. 24, the mesh size described above is suitable.

An abrasive grain layer containing abrasive grains 3 is formed on the glass fiber mesh 2. As abrasive grain 3,
High hardness is best, specifically the aforementioned SiC,
In addition to Al ₂ O ₃ and ZrO ₂ , quartz, diamond, or a mixture thereof may be used. These abrasive grains are
A thermosetting resin is bonded to the substrate in the void on the glass fiber mesh.

The ground paper disk of the present invention having the above structure can be manufactured as follows.

First, a vulcanized fiber plate 1 having a predetermined shape and thickness is prepared. A glass fiber mesh 2 of approximately the same size is placed on the surface of this fiber plate, and four liquid thermosetting resins of a predetermined viscosity are applied thereto to a thickness that covers the surface of the glass fiber mesh. The thermosetting resin 4 used is as follows:
Any resin may be used as long as it has high mechanical strength when completely cured and can firmly bind the glass fiber mesh and the abrasive grains described below, such as resol type phenolic resin, epoxy resin, etc. , urea resins, each alone, or a mixture of two or more of these resins can be mentioned. If the viscosity of the resin liquid is too high, the uniformity of wetting with the substrate and glass fiber mesh will decrease.
In addition, when the abrasive grains described later are sprinkled on top of the glass fiber mesh, the formation of a mixed state with the glass fiber mesh does not proceed smoothly, and conversely, if the viscosity is too low, the amount of resin applied will be small, so the abrasive grains will not be mixed with the glass fiber mesh. This causes a problem of rapid shedding. Usually 10.0~13.0 poise (25
°C) is preferred. Incidentally, at this time, charcoal may be added as an extender in an amount of 20 to 50% by weight based on the resin.

Next, the resin 4 is left in this state or, if necessary, heated slightly at a temperature of about 60° C. to harden the resin 4 a little, and then the abrasive grains 3 are sprinkled thereon. If the resin is still soft, some of these abrasive grains will sink into the resin under their own weight and form the glass fiber mesh 4.
It becomes mixed with Thus, the substrate 1, the glass fiber mesh 2 and the abrasive grains 3 are brought into close contact with each other. In this state, if necessary, heat the resin slightly at a temperature of about 60 to 100°C to harden the resin a little.

Thereafter, a liquid thermosetting resin 4 is poured over the abrasive grains to coat the abrasive grains 3 deposited on the surface with the resin.

Then, the whole is introduced into a heating furnace at a predetermined temperature to completely cure the thermosetting resin 4. If the temperature at this time is too high, foaming of the resin will occur.
Also, if the temperature is too low, curing will not proceed, so usually
The temperature is preferably 60 to 180°C, and it is preferable to gradually increase the temperature.

[Example of the invention] A donut plate having an outer diameter of 180 mm and an inner diameter of 22 mm was cut out from a vulcanized fiber plate (manufactured by Toyo Fiber Co., Ltd.) specified in JIS C2315 and used as a substrate. The thickness was 0.8mm.

Next, non-volatile content is 68%, specific gravity (weight at 25°C per 1 g of water at 4°C) is 1.193, viscosity (25°C) is 12.0 voids, gelation time is 4.5 minutes/150°C, and water miscibility is 3.5.
A resin liquid consisting of 100 parts by weight of resol resin, 100 parts by weight of charcoal, and 30 parts by weight of water at 25°C and pH 9.2 was prepared.

A glass fiber mesh with a fiber diameter of 180 mm and a mesh size of 1.5 mm x 1.5 mm was placed on the substrate, and 16 g of the resin liquid was poured thereon.
55g of No. 16 IrO ₂ abrasive grains were sprinkled. Next, the whole
After leaving it in a drying oven at 100° C. for 90 minutes, 10 g of the resol resin alone was poured thereon. The entire resol resin was again introduced into a drying oven at 120° C. for 3 hours and left to completely heat cure.

For comparison, ground paper disks were made in a similar manner except that the glass fiber mesh was not used.

Attach each grinding paper disk to a portable sander, and grind the grinding surface with a diameter of 217 mm and a wall thickness of 5 mm.
was pressed against the circumferential surface of the steel pipe at a 25 degree angle.
The pressing pressure was 30 kg/cm.

No abnormality was observed in the ground paper disk of the present invention even at a rotation speed of 25,000 rpm. In contrast, the peripheral edge of the comparative example ground paper disk was damaged at 8000 rpm. When the damaged area was observed, shell-like peeling marks of approximately 5 to 10 mm were observed near the outer periphery. This mark is located at 2 on the surface of the board.
There were traces of ~3 paper layers peeling off along with the abrasive grains on top.

In addition, a strip-shaped test piece of 20 mm x 70 mm was cut out from each abrasive paper disk, and force was applied to each test piece by holding both ends in the longitudinal direction, and the force required to fold it was measured. In the case of the disk, it was about 3 Kg/cm ² , and in the case of the comparative example, it was about 0.5 Kg/cm ² .

[Effects of the invention] As is clear from the above explanation, the ground paper disc of the invention has extremely high bending strength and flexibility, and does not sag during use. It is suitable for grinding work effectively for long periods of time in narrow areas of the ship's hull, and even when using large-diameter, high-hardness abrasive grains, the abrasive grains are firmly bound to the substrate via the glass fiber mesh. This prevents part of the paper layer of the substrate from peeling off and breaking during work and scattering along with the abrasive grains, which helps prevent danger. Furthermore, since high-quality abrasive grains are used and high-speed rotation work is possible, work efficiency is improved. In addition, if high-quality abrasive grains are used, the grinding force will be large without strong pressure contact, there will be little wear, and it will be highly durable and effective from an economic standpoint.

[Brief explanation of the drawing]

FIG. 3 is a partial cross-sectional view of the abrasive paper disc of the present invention. 1... Base made of vulcanized fiber, 2... Glass fiber mesh, 3... Abrasive grain, 4... Thermosetting resin.

Claims (1)

[Scope of utility model registration request] The surface of the substrate made of circular vulcanized fibers has a mesh size of 1.5 mm x 1.5 mm to 5 mm x
Grinding paper in which a 5 mm glass fiber mesh is bonded with a thermosetting resin, and abrasive grains are further bonded with the thermosetting resin via the glass fiber mesh to form a thin layer of abrasive grains. disk.