Silicon carbide water resistant sandpaper in the production of details should be paid attention to

Zhao Zhongjin

Silicon carbide water resistant sandpaper in the production of the most critical is to maintain the stability of the quality, and stable

Qualitative is precisely the most difficult problem to control in the production process. Mainly manifested in: sandpaper water resistance, wear resistance, softness and sandpaper formation. Its production grain number, span is its characteristics. Whether the viscosity of glue or abrasive particle size is very large, especially 120# with thick size and 800# with fine size of the production process control requirements are very high, often we are prone to some details in the production of improper control, will affect the quality of the product, Lead to users in the use of sand, wear resistance, water resistance, uneven edge warping curling sandpaper, polishing objects fade phenomenon.

A, base paper processing process production of silicon carbide water resistant sandpaper is the use of 100% kraft coniferous wood pulp made of kraft paper, this kraft paper due to its water resistance and poor permeability, we use it to produce silicon carbide water resistant sandpaper, the need for water resistance and penetration prevention treatment. The base paper is mainly coated and immersed in two ways, generally using a simple way to deal with oil. We usually use physical methods: the base paper is soaked in alkyd resin or epoxy resin, so that it is fully soaked, the pores in the base paper are blocked, the paper fiber is absorbed and the excess resin is extruded by the roller, and then dried and rolled by the step temperature, and the natural cooling is reserved for use. This process is called base paper processing.

The first is the viscosity of the blended primer: usually applied at 25℃ for 4 cups with the viscosity adjusted in the range of 17-25 seconds. If the two dipping process is used, the first viscosity is higher than the second viscosity. Due to the tightness of the base paper and pulp fiber, as well as the natural temperature of the workshop will affect the absorption effect of the base paper, so the amount of oil to adjust the amount of oil through several inspection tests in the production, oil absorption more processing paper brittle, but also increase the cost; Less water resistance has an impact. The second is temperature control. Usually a high temperature in the middle, low ends of the ladder form. If the epoxy treatment agent is used, the intermediate high temperature zone should be between 105-120℃, because the general paper treatment production line is not long enough, the paper stays in the oven for a short time, easy to cause the resin is difficult to cure. Another is to deal with paper storage cycle. It usually takes more than 15 days to recure the resin and stretch the paper fibers. The natural storage time is longer, the flatness of the paper will be better, the glue will be more uniform on the production line, and the sand amount will also achieve a better effect.

2. Preparation and inspection of materials before production

One is the water resistance test of the treatment paper. According to the date of processing paper, the length of time to sample test water resistance, and to compare the amount of oil and the gram weight fluctuation of different base paper. The second is the quality state of sand. Check whether the ratio of coarse sand is uniform, not wet sand, not clear sand. 360 mesh with fine sand, especially micro powder is easy to delix into groups, not easy to disperse, which is its characteristic, plus in the storage and transportation process is easy to return to moisture. It should be dried twice a week before using special drying equipment, and then bagged and stored in a dry place after cooling. The third is the detection of binder. No matter what resin is used before opening the cover unpacking test, especially to test the viscosity, clarity, leveling and so on. Through testing whether the resin and solvent to be used meet the glue requirements of the production process. Comply with the principle of "minimum amount first, then increase the amount" when mixing glue each time.

Three, the preparation of binder requirements

The viscosity standard of the glue used in the production of silicon carbide is usually the best viscosity measured at 25℃, because most manufacturers of the production workshop can not be constant temperature and humidity, resulting in production is subject to the natural environment temperature, in order to deal with the temperature change, our production experience tell themselves, based on the viscosity standard, And according to the workshop room temperature adjustment up and down 5-15 seconds to deal with the temperature difference in the morning, middle and evening, summer and winter when the viscosity of the glue standard.

The key of glue preparation is two points: first, the amount of curing agent directly affects the softness and wear resistance of sandpaper; Second, the amount of glue: from the production experience of the industry and foreign manufacturers, the amount of glue on the base is more, the sand paper is not easy to drop sand, especially the fine size products can meet the requirements of sand planting. The adhesive viscosity should be controlled well. The coarse sand surface should be shiny and bright. The glue quantity of fine products should not be thick and the sand surface should not be bright.

Four, equipment adjustment and requirements

The common problem in the production of silicon carbide products is that the coarse product sand appears sand hole or weight is heavy; The amount of fine sand can not go up. This problem is caused by a combination of multiple factors: first, whether the adjustment of the electrode plate height matches the relationship between the thickness of sand layer; The second is whether the sand conveying speed and electrostatic voltage adjustment reach the best value. Third, the sand volume and uniformity of the sand bucket. When we produce micro-powder grade products, the lower sand of the sand bucket directly tests the precision performance, controllability and convenient operation of our sand bucket equipment. Fourth, the stable temperature and humidity of the sand room play a key role in the quality of the sand room. The airtightness of the sand room and the appropriate space are particularly important.

Secondly, the temperature control of the drying room ladder: both bottom rubber drying room or compound rubber drying room should meet the temperature requirements required by the drying process, especially when the temperature curve of the drying room is not stable in the range of set values, it is necessary to extend the time through the drying room to ensure that the sand surface is fully dry. Otherwise, the large volume can not be fully cured will lead to sandpaper wear-resistant, sand lodging, sand surface is not sharp and other quality problems.

V. Verification and optimization of process standards

It is very important to optimize the process formula and verify its correctness. Due to the changes in materials provided by the industry, the material ratio in our production process needs to be verified and fine-tuned, especially for homemade glue, such as: whether the viscosity standard of epoxy compound glue and treatment glue matches the abrasive particle number of products in the same industry needs to be verified. Sometimes the viscosity of the same material ratio can not be lifted, it should be that our material ratio has not been adjusted accordingly with the change of raw and auxiliary materials. We often overlook new problems arising from the use of old formulas and fail to optimize old process standards. The ratio of chemical materials cannot be constant for many years, you do not change, others are changing, and we have no testing equipment for some materials, the testing data comes from suppliers, most of which can only be analyzed and judged from the phenomenon in the production process.

Vi. Treatment of subsequent processes

First of all, the large roll of sandpaper should be immediately flexible and humidified water. Through high temperature baking sandpaper matrix will be seriously dehydrated resulting in "collapse" phenomenon. In the state of residual temperature, paper fiber is easy to absorb water and restore fiber elasticity. Can reduce the brittleness of sandpaper, increase toughness. In winter, when humidifying and replenishing water is carried out in production, warm water is more ideal. Secondly, the storage of the large volume of 3-7 days is conducive to the full recovery of the paper base of the sandpaper, sand surface smooth, prevent warping, internal roll phenomenon. It is also a process of the resin reaction to slow down the secondary curing. And then the large volume after the inspection of the box into storage. Storage time is also very key, sandpaper from the theory: 30 days after the line to achieve an ideal use effect. Generally, manufacturers will use three batches of products in stock and send the first batch, so as to arrange the production cycle.