JPH1110544A - Manufacture of abrasive material made of thermosetting resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture abrasive material which is hardened enough so that there is little odor and the grains are hard to separate at the time of shot blast with good efficiency and at a low cost by impregnating paper with liquid thermosetting resin, drying the same, stacking the impregnated paper, forming the paper to be plate-like at high temperature and with high pressure, and then grinding the same. SOLUTION: Formalin and melamine are prepared to attain a mol. ratio of 2.0 in a reactor oven, adjusted to have PH9-10 by caustic soda, and then made react by heating reflux to obtain liquid melamine resin which has 70 cPs/25 deg.C and about 50% nonvolatile matter. An aqueous solution of hydrochloric acid is added to the above resin to be adjusted to have PH4-5, kraft paper 100 g/cm<2> is dipped in the above material to which a small quantity of an internal surface lubricant is added, the adhesive resin quantity is adjusted, and the material is passed through a hot blast air support type drying drum to obtain melamine resin impregnated paper which has 52% resin adhesive quantity and 5.6% nonvolatile matter. The paper is formed to be plate-like and ground. Thus, it is possible to produce an abrasive material having the optimum hardness and strength for trimming a plastic molded article which is precisely molded and worked such as electronic parts or the like efficiently and at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to polishing for shot blasting for efficiently removing burrs generated during molding of a plastic molded product, particularly a thermosetting resin molded product such as an electric or electronic component having a resin-sealed element. The present invention relates to a method for manufacturing a material.

[0002]

2. Description of the Related Art As abrasives used in post-molding shot brass after molding, such as removal of burrs, for example, hard materials include powders of alumina, glass, metal, etc., which are used in electronic parts. It is too hard for a thermosetting resin molded product molded as. Conversely, soft materials such as nylon, polypropylene, and walnut hulls are too soft and inefficient. A polishing material made of a thermosetting resin is effective in removing burrs from a thermosetting resin molded product such as an electronic component, which has an intermediate characteristic between them. Since thermosetting resins are generally expensive, defective products during molding, sprue runners, etc.
Abrasives are produced from molding waste.

[0003] Among thermosetting resins, phenol resins are mainly used as abrasives. A large amount of phenolic resin molded products are produced, and there are also many injection moldings. Therefore, there are many processing waste materials such as sprue runners. However, most of the phenolic resin molded products are of a black type, and when shot by dry blasting, stains on products are conspicuous, and when using wet methods, stains on drainage are conspicuous. In addition, in injection molding, uncured products are produced before and after molding, and these are mixed into processing waste materials, which may cause odor problems when used as abrasives. Generally, various fillers are mixed in the phenolic resin molded product, the amount of ash is large, particles are fragile when used as a powder, and particles may be easily broken when shot blasted. On the other hand, a molded product of a melamine resin or a urea resin has a relatively small production amount and a large amount of compression molding, so that there is almost no processing waste such as a sprue runner.

[0004]

The object of the present invention is to provide an abrasive material which has a low ash content, is sufficiently hardened and has a low odor, has a high particle strength, hardly breaks particles during shot blasting, and has a low odor. It is an object of the present invention to provide a good and inexpensive manufacturing method.

[0005]

SUMMARY OF THE INVENTION According to the present invention, paper is impregnated with a liquid thermosetting resin, dried, and then the impregnated paper is laminated.
After forming into a plate at a high temperature and high pressure, a method for producing a thermosetting resin abrasive, characterized by pulverizing this plate-like molded product,
It is about. Examples of the liquid resin include a phenol resin, a melamine resin, and a urea resin. For molding a light-colored cured product, a melamine resin, a urea resin, or a urea-melamine resin can be preferably used. For example, melamine, urea or a mixture of melamine and urea and formalin are added to a reaction vessel in a molar ratio of 1.0 to 2.5, and an alkali catalyst is used. A body (hereinafter referred to as varnish) is obtained.

In order to impregnate the paper with the varnish, the varnish is stored in a varnish vat, the paper is immersed, and the amount of resin impregnated in the paper is adjusted with a squeeze roll or a stick stick. It is convenient to use a hot-air drying drum for drying while floating, and a coating and drying device having a cutting portion for cutting the dried impregnated paper into a predetermined length. When kraft paper used for a paper base phenolic resin-clad laminate or a melamine resin decorative board is used, impregnation and drying are easy. The impregnated paper thus obtained is inserted between a plurality of stacked metal plates and heated and pressed by a multi-stage press to form a plate. The plate-like molded product is taken out and pulverized by a pulverizer. For example, after a plate-like molded product is roughly pulverized by a crusher, then pulverized by a hammer mill or the like, and a vibrating sieve is used to extract particles having a required size as an abrasive, thereby producing a desired powdery abrasive. can do.

For example, a thermosetting resin such as an epoxy resin is often used as a resin for sealing a semiconductor element. In this case, an abrasive made of a thermosetting resin such as a phenol resin is optimal in terms of hardness. However, an abrasive made of only a thermosetting resin is brittle and particles are easily broken during shot blasting. In order to improve the fragility, it is necessary to reinforce with a fibrous filler, but, for example, in the case of a novolak type phenol resin powder, in order to sufficiently impregnate the fibrous filler, it is necessary to sufficiently knead,
It takes man-hours. Also in the production of resin, solid resin such as novolak type phenol resin requires a dehydration step, and after cooling and solidifying, it needs to be pulverized into a powdery form, which takes a lot of man-hours and increases costs.

On the other hand, a liquid resin such as a resole type resin can be easily impregnated by immersing a sheet such as paper in the resin. In addition, a dehydration step is not required at the time of resin production, and since the resin can be taken out of the reaction vessel and then transferred to the sheet impregnation step by a simple operation such as adjusting specific gravity, production can be performed at low cost. In addition, as a sheet for reinforcing the resin, a sheet made of glass fiber or synthetic fiber can be used, but in consideration of low ash content, resin impregnation, strength, workability cost, etc. It is convenient to use bleached or unbleached kraft paper that has been made.

As the phenolic resin-based abrasives, defective products and processing waste materials such as sprue runners are often used, and in these processing waste materials, uncured products are mixed in for the purpose of cleaning the molding machine and cleaning. Often. The uncured product has a strong odor and has a problem in work, and the particle strength is small. In the case of the present invention,
Since the product formed by heating into a plate shape is pulverized, curing is sufficient and odor is very small. The color tone of the abrasive is also a light yellow to brown natural color because it does not contain a pigment or the like in the present invention. Of course, it is also possible to use a light-colored paper such as a white paper using a pigment-folded paper.

[0010]

【Example】

(Production of liquid melamine resin) Formalin and melamine were charged into a reaction vessel at a molar ratio of 2.0, adjusted to pH 9 to 10 with caustic soda, and then heated to reflux for a viscosity of 70.
A liquid melamine resin having a cps / 25 ° C. and a nonvolatile content of about 50% was obtained. (Impregnation / drying of paper) A 100 g / cm ² kraft paper is immersed in the liquid melamine resin by adding an aqueous hydrochloric acid solution to adjust the pH to 4 to 5 and adding a small amount of an internal release agent, and reducing the amount of the adhered resin with a squeeze roll. The melamine resin-impregnated paper having a resin adhesion amount of 52% and a volatile content of 5.6% was obtained by passing through a drying drum of a hot air air support type after adjustment.

(Formation of a plate-like molded product) The impregnated papers are piled up four times and sandwiched between stainless steel flat plates at a pressure of 10
It was heated and pressed by a press of 0 kg / cm ² and a hot plate temperature of 170 ° C. to obtain a melamine resin molded plate having a thickness of about 1 mm. (Characteristics of plate-like molded product) Specific gravity: 1.45 Rockwell hardness: 110 Charpy impact strength: ² kgf / cm ² Flexural strength: 10 kgf / mm ²

(Pulverization into Abrasive Material) This melamine resin molded plate was cut into a ribbon having a width of 15 mm, and pulverized by a hammer mill. The crushed product is sieved with a vibrating sieve (18 mesh pass 40).
(Mesh on) to obtain a powdery abrasive having an average particle size of about 500 μm. As a conventional abrasive, a powdery abrasive having an average particle diameter of about 500 μm, a nylon particle (average particle diameter of about 500 μm) obtained by pulverizing a molded product of an organic filler phenol resin molding material in the same manner as the melamine resin plate-shaped molded product, Glass beads (average particle size of about 500 μm) were prepared.

(Characteristics of Abrasives) With respect to these abrasives, the polishing power, the surface condition of the material to be polished, the odor and the amount of scattered fine powder were measured. The results are as follows. ──────────────────────────────── Polishing power Odor of the material to be polished Amount of scattered fine powder Surface condition ───── ─────────────────────────── Melamine resin abrasive ○ Good Fine Very fine Phenolic resin abrasive △ Poor * 1 Large Many (washed) ○ Poor * 1 Slight Slight Nylon particles × Defective Slight Ultra-small glass beads ○ Defective No Slight ──────────────────────────────── Polishing power ○: No problem, Δ: Some burrs left, ×: Many burrs left * 1: Black stains are generated.

(Measurement Method) A 30 kg of each abrasive was added to 100 kg of water, and a deburring test was performed on a light blue IC molded product sealed with an epoxy resin using a wet polishing machine.

[0015]

The abrasive for deburring a precision molded plastic article such as an electronic component needs to have a hardness strength close to that of the plastic used for the molding.
According to the method of the present invention, it is possible to efficiently and inexpensively produce an abrasive having optimum hardness and strength.

Claims (3)

[Claims] 1. After impregnating a paper with a liquid thermosetting resin and drying, laminating the impregnated paper, forming it into a plate at high temperature and high pressure, and pulverizing the plate-like molded product. A method for producing an abrasive made of thermosetting resin. 2. The method according to claim 1, wherein the thermosetting resin is a melamine resin, a urea resin, or a urea-melamine resin. 3. An abrasive having an average particle size of 200
The method for producing an abrasive according to claim 1 or 2, wherein the thickness is from 1000 to 1000 µm.