KR100349453B1 - Method for forming engineering plastics by profile extrusion process - Google Patents

Abstract

The present invention relates to a method for molding engineering plastics by a release extrusion method, and more particularly, in a method for molding circular and polygonal engineering plastics by a release extrusion method, a sol discharged through a final molding die of an extruder. The resin in the state is passed through a three-stage vacuum tank in which the vacuum gauge pressure at each stage is maintained in the range of -500 to -700 mmHg, and the tank of the first stage (within the glass transition temperature of the resin + 20 ° C) Supply and circulate the oil heated in the temperature range, and supply and circulate the oil heated in the temperature range of the tank of the second stage (within the tank set temperature of the first stage -20 ℃), and the tank of the third stage It is manufactured by supplying and circulating oil heated in the temperature range of the tank of the second stage (-20 ° C within the second stage), and the engineering by the release extrusion method of 15 to 50mm thickness of the molded resin It relates to a molding method of plastics. Through the method of the present invention, the reduction of production cost and production process by shortening the unit manufacturing process by air cooling method and blocking the generation of bubbles such as pore formation in the product, and producing and supplying a beautiful product that does not require secondary reprocessing It is effective to shorten and improve high added value.

Description

Method for forming engineering plastics by profile extrusion process

The present invention relates to a molding method of engineering plastics by the release extrusion method, and more specifically to a high-thickness product through the release extrusion method using a material that requires transparency, such as polycarbonate and polymethyl methacrylate resin. In production, by shortening the production process by improving the cooling process and inducing the cooling process by constant temperature and slow cooling to secure the optimal conditions of cooling, not only forming and processing of stable products, but also blocking the formation of a large amount of pores by quenching The present invention relates to a molding method of engineering plastics by a release extrusion method that can minimize a defect rate of a product and produce a high quality product.

Prior arts related to engineering plastics include Korean Patent No. 119769 (name: engineering plastic composition and molded article thereof), Korean Patent No. 222240 (name: manufacturing method of engineering plastic sheet with excellent weather resistance), and Korean patent application 90-015255 (name: engineering plastic composition and molded article using the same), and Korean Patent Application No. 92-018570 (name: manufacturing method of reinforced crystalline engineering plastic composition), etc., these are provided with the provision of functionality by the composition component It is mainly characterized by. In addition, Korean Patent Application No. 92-004104 (name: molding method of engineering plastic with a protective paper) describes that it is possible to prevent the scratches of the molded article using a protective paper, but the release extrusion method such as the present invention is applied It is not.

Currently, the molding process of engineering plastics such as polycarbonate and polymethyl methacrylate resins is used to form primary molded resin through a T-die in the production of sheet (sheet) up to 15 mm thick through an extruder. Final molding is carried out through a roll (polishing roll), and at this time, cooling is performed by a temperature gradient of each forming roll. By cooling this in the air through the guide rolls, the production process is lengthened and furthermore, due to the limitations of the cooling process, it is very difficult to control the molding conditions not only 15 mm or more but also 15 mm or less in thickness. In addition, there is a disadvantage in that the productability is deteriorated due to the generation of the micro-bubbles (pores) generated in the product or the phenomena.

On the other hand, in the case of casting acrylic produced in a plate shape using a liquid acrylic monomer, it is possible to produce a product having a thick thickness, but there is a problem that the continuous operation is impossible and the cooling time takes a long time, productivity is reduced.

In particular, the resin having a morphologically amorphous structure (the glass transition temperature at which the movement of the molecular chain is active, the flowability is poor compared to the crystalline polymer, and the processing is not easy to be processed) by the extrusion extrusion method In the production of mold release products, the existing profile production method produces products with thickness less than 5mm by indirect cooling, and produces products by indirect contact method of cooling water or heating oil and the formation of the source by vacuum. And the pipe production method by using a forming roll to cool in the air, that is to produce a acrylic pipe using a slow cooling method through a hot air fan by extending the cooling line of the production line.

However, all of them have long production processes, and are not good in quality and poor in transparency due to the occurrence of fine scratches or scratches on the surface of the product due to mold (singing). There was a limit.

Due to these problems, it is impossible to produce products with a thickness of 15mm or more. Therefore, the application is avoided by the continuous extrusion method or by the selection of alternative materials and the secondary processing by imported goods. The price is very high.

Accordingly, the present inventors first formed and cooled in producing products having a thick thickness such as round bars and square bars, that is, products ranging from 15 mm to 50 mm, using a release plasticizer using polymethyl methacrylate and polycarbonate resins, which are transparent plastic materials. It solves the above problems by supplying oil heated to a constant temperature instead of cooling water to the vacuum tank, which blocks the rapid cooling while blocking the air bubbles in the product by using the slow cooling method by the temperature gradient of each tank. It has been found that the present invention has been completed based on this.

Accordingly, an object of the present invention is to provide a method for molding an engineering plastic by a release extrusion method that can produce a thick-thick product in the production of release extrusion products using polycarbonate and polymethyl methacrylate resin, which is difficult to mold. have.

In order to achieve the above object, the molding method of the present invention is a molding method of an engineering plastic having a circular or polygonal profile by a release extrusion method, wherein each step of the resin of the sol state discharged through the final molding die of the extruder The vacuum gauge pressure is passed through a three-stage vacuum tank maintained in the range of -500 to -700mmHg, and the tank of the first stage is filled with oil heated to a temperature range of (within the glass transition temperature of the resin +20 ℃). The oil is heated and circulated to the tank of the second stage (within the tank set temperature of -20 ° C of the first stage), and the oil heated and circulated to the tank of the third stage (to the tank of the second stage Supplying and circulating the oil heated in the temperature range of the tank set temperature (within 20 ℃) to ensure cooling by slow cooling and roundness (shape molding) through vacuum near the glass transition temperature point of each resin. Cooling in shorter process and product molding are prevented while blocking the movement of resin due to uncooling of the center of product generated by cotton cooling and the problem of large pore generation and growth caused by moisture and decomposable gas particles remaining inside the resin. Securing step.

1 is a process for manufacturing a release extrusion using polycarbonate and polymethyl methacrylate resin according to the present invention.

2 is an apparatus diagram schematically showing an oil cooling method used in a cooling process according to the method of the present invention.

Explanation of symbols on the main parts of the drawings

1: manometer 2: thermometer

4: vacuum pump 10, 12, 14: heater

20, 22 and 23: Oil cooler 30: Main oil tank

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The present invention introduces the molten melt through the extruder into the vacuum tank in the molding and processing of a resin that requires high transparency, such as polycarbonate or polymethyl methacrylate resin, into the vacuum state using a vacuum pump. By making it possible, the round shape can be secured in the desired shape, and the oil maintained at a constant temperature is circulated and supplied inside the tanks of each stage to make direct contact with the surface of the product. The present invention relates to a molding method for releasing and extruding by removing pore formation and moisture and decomposable gas particles from the surface due to the movement of polymer inside due to the cooling of the outside of the product generated in a rapid cooling process with only simple functional facilities.

Conventionally, the resin before the extrusion or in the storage tank removes water and decomposable gaseous particles remaining in the molten resin through a vacuum pump or a vent in the initial stage, the melt section, the front end of the cylinder (neck), etc. of the cylinder in the extruder. Was prepared in a plate shape of 15mm or less through a pretreatment step of drying for a long time. At this time, the melt formed by primary molding through a T-die (final die) was finally molded in a forming roll maintained at an appropriate temperature by a heat medium, and then a plate was manufactured by a cooling process in an atmospheric phase through a guide roll. Therefore, due to the structure of the device, the production line is long, and there is a drawback of not being able to form a thick product and there is a limit to producing a desired product, and the product has to go through additional secondary processing such as cutting, bonding, and processing. Could not produce high or high quality products.

Particularly, in the production of mold (profile) extrudates, in the production of low thickness (less than 5mm) by the extrusion extrusion method by the indirect cooling method by forming a channel in the mold and passing the cooling water to contact the surface of the melt. While cooling, air was drawn in between the molds formed in multiple stages to form a vacuum state, thereby securing a desired shape and origin.

Therefore, there is a problem that the capacity of the take-off machine should be increased due to the strong contact between the mold (singing) and the resin surface, and the resin crushing phenomenon and excessive scratch marks are generated on the surface of the finished product. The shortcomings of producing high-thickness products in a short time and generating bubbles of pores when the thickness exceeds a certain thickness are accepted as a general phenomenon in the extrusion method.

In addition, in the pipe release extrusion method, a molten material is introduced into a mold inside a vacuum tank, but a pipe and a thin mold-formed product are manufactured by a direct cooling method of contacting a resin surface through circulation of cooling water while maintaining a vacuum state through a vacuum pump. Although a method is used, this also is impossible due to the generation of pores in the product in the production of high thickness products.

Therefore, in producing products of simple shapes such as round and square, a certain high thickness is produced by a slow cooling method such as hot air while maintaining cooling and molding through the same guide roll as the product shape. This also can not expect the high quality of the product by the guide roll, there is a disadvantage in that the cooling process is prolonged and the excessive energy loss caused by the hot air.

Thus, referring to Figure 1, in the present invention, the polycarbonate and polymethyl methacrylate resin is molded in an extruder, and the product is drawn and cut through the cooling process and the natural cooling and transfer process in the guide roll. The cooling process has three sets of vacuum tanks, and the residence time of each melt may vary depending on the desired product thickness, but the length of the tank so as to stay in the first stage of the tank within about 1 to 2 minutes. The two-stage vacuum tank is increased by 1/3 to 2 times the length of the first stage, and the three-stage vacuum tank is increased by 1/3 to 2 times the length of the second stage. .

The variation in length in the tank is a prerequisite for the stability of the cooling to remove the water and decomposable gas particles remaining in the resin from the surface, and to achieve a constant and slow cooling time in the product. . If the degree of retention is the same, the possibility of the formation of pores according to the thickness cannot be excluded, and the difficulty of setting the conditions resulted in the failure.

Referring to Figure 2, under the above conditions, the vacuum of -500mmHg to -700mmHg (gauge pressure) was applied to the tank at each stage through the vacuum pump and oil maintained at a constant temperature was introduced into the vacuum tank. At this time, if the vacuum condition is less than the gauge pressure of -500mmHg can not control the shape of the product to be produced may cause a failure, and if the gauge pressure of -700mmHg exceeds the capacity of the take-off machine with excessive vacuum pressure In addition to the increased cost, forcible pulling can cause scratches on the surface.

At this time, on the basis of the glass transition temperature of the resin to be molded, the oil heated in the temperature range (within the glass transition temperature of the resin to be molded + 20 ° C.) is supplied and circulated, and the tank of the second stage is The oil heated in the temperature range (within the temperature of -20 ° C set in the tank of the first stage) is supplied and circulated, and the tank of the third stage (within the temperature of -20 ° C set in the tank of the second stage). Supply and circulate the oil heated to the temperature range. At this time, if the temperature of the oil supplied to the tank of the first stage is less than the glass transition temperature of the resin to be molded, a large number of bubbles cannot be prevented in the resin, and if it exceeds 20 ° C above the glass transition temperature of the resin to be molded, There is a disadvantage in that the cooling line is lengthened due to the cooling. In addition, if the temperature of the oil supplied to the tank of the second stage and the third stage exceeds 20 ° C than the temperature of the oil of the first stage and the second stage, respectively, this also generates a large number of bubbles in the resin.

For example, in the case of polymethylmethacrylic resin, oil heated to 100 to 120 ° C. in the tank of the first stage, oil heated to 90 to 110 ° C. to the tank of the second stage, and to the tank of the third stage The oil heated to 80-100 ℃ was circulated and supplied at constant temperature, and when oil deviation of ± 3 ℃ occurred due to temperature sensing, the oil was automatically circulated to block the rise of oil temperature in the tank by the melt to maintain constant temperature. . In the case of polycarbonate resin molding, oil heated to 130 to 150 ° C. in the tank of the first stage, oil heated to 130 to 140 ° C. to the tank of the second stage, and 110 to 110 tanks in the third stage are used. The oil heated to 130 ℃ was supplied to the circulation, constant temperature, when the oil deviation of ± 3 ℃ was automatically circulated to block the oil temperature rise in the tank by the melt to maintain a constant temperature. For reference, the glass transition temperature of the polymethyl methacryl resin is 100 ° C, and the glass transition temperature of the polycarbonate resin is 130 ° C.

In FIG. 2, reference numeral 1 may identify a vacuum pressure inside the vacuum tank as a pressure gauge, and reference numeral 2 may identify a temperature inside the vacuum tank as a thermometer. In addition, reference numeral 30 serves as a main oil tank to replenish oil in the tank and to remove and store the oil in the tank at the end of the work. In addition, heaters 10, 12, and 14 are built in each vacuum tank to control the oil temperature inside the vacuum tank. Reference numeral 4 is a vacuum pump that maintains the vacuum pressure to control the inside of each vacuum tank.

On the other hand, when the oil is heated to an appropriate temperature condition by the heater (10, 12, 14), and the temperature of the oil rises by the movement of hot resin, the water tank using the oil cooler (20, 22, 23) by automatic control By circulating and cooling the oil inside, the oil temperature in the tank is always maintained at the proper temperature. The oil coolers 20, 22, and 23 are cooled by circulating the cooling water by a general cooling method. The oil cooled in this way is supplied to the main oil tank 30 and then re-supplied to each vacuum tank by using each circulation pump.After the end of the work, the oil cooled through the oil cooler is collected into the main oil tank 30. It is kept. In addition, when the air is discharged from each vacuum tank through the vacuum pump 4, the oil discharged together is resupplied to the main oil tank 30. Then, the cooling discharged through the vacuum tank of the final third stage and After the rounding is completed, the product is naturally cooled in the air through the guide roll, and the product is transferred using a take-off machine, and then cut to the desired length using a cutter.

The oil used in the present invention has a breaking point in the temperature range of 200 ~ 300 ℃, the specific gravity is less than or equal to three oils, and may be an edible oil, silicone oil, etc., but considering the reactivity considering the resin properties of the product The industrial silicone oil satisfying the above conditions is stable and effective in terms of durability, reactivity, constant temperature and price.

As a result of producing the product under the conditions and process development of this process, the annealing cooling prevents and removes the bubble porosity generated inside the product through pretreatment, so that an annular, triangle, square, or polygon of 15 mm or more and 50 mm or less. Could produce the product.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the following Examples.

Comparative Example 1

In a conventional method, the extrudate is introduced and drawn into a mold (singing) of the same vacuum tank through a pretreatment process such as extrusion of a melt which melts the polycarbonate resin using an extruder and is discharged from the final die. Was forced to cool by supplying, circulating, and discharging as it was maintained in a vacuum state, resulting in an irregular and large amount of bubbles. At this time, the withdrawal conditions are T ₁ (290 ° C.)-T ₂ (300 ° C.)-T ₃ (270 ° C.)-T ₄ (260 ° C.)-T ₅ (240 ° C.)-T ₆ (220 ° C.) and extrusion The water was circular in shape and diameters of 15 mm, 25 mm and 35 mm.

Comparative Example 2

The same pretreatment process as in Comparative Example 1 was carried out, but the cooling tank heated to 80 ° C. or higher was circulated to achieve slow cooling, and as a result of being discharged by maintaining the vacuum state, irregular and large amounts of bubbles were generated.

Comparative Example 3

The same pretreatment process as in Comparative Example 1 was carried out, but the cooling tank heated to 80 ° C or higher was circulated to achieve slow cooling, and the vacuum pump was stopped and discharged in a normal state or discharged by varying the degree of vacuum in each tank. As a result, an irregular and large amount of bubbles still occurred.

Comparative Example 4

In the same pretreatment process as in Comparative Example 1, when the product was discharged by indirect cooling method, the thickness of the product became thick, resulting in poor surface cooling and irregularity due to poor cooling, and less distribution than Comparative Examples 1, 2, and 3. However, bubbles of some good size sporadically occurred.

Comparative Example 5

In the same pretreatment process as in Comparative Example 1, but using a silicone oil in the vacuum tank as shown in Figure 2 by supplying a heated oil of 110 ℃ less than 130 ℃, which is the glass transition temperature point to each stage, the temperature deviation of the second stage and third stage When the result was within 10 ° C., a large amount of microbubbles, more specifically, bubbles having a diameter of less than 5 mm, which were smaller in size than Comparative Examples 1 to 4, were produced over the entire surface of the resin center.

Comparative Example 6

Silicone oil heated at 110 to 130 ° C. in the tank of the first stage, oil heated at 120 to 140 ° C. in the tank of the second stage, and 130 to 150 ° C. to the tank in the third stage under the conditions of Comparative Example 5 As a result of supplying the heated oil to the circulation and constant temperature, bubbles were significantly reduced, but intermittently occurred, the defect rate was high, and it was tensioned by being sensitive to workability such as resin deformation in the third stage, more specifically, pulling conditions. Due to the difficulty in the formation of the circle, there was a difficulty in producing a stable product.

Example 1

The silicon oil heated to 130-150 degreeC in the tank of a 1st stage under the conditions of the comparative example 5, the oil heated to 120-140 degreeC to the tank of a 2nd stage, and 110-130 degreeC to the tank of a 3rd stage are As a result of supplying the heated oil with circulation and constant temperature, it was possible to produce high quality products with excellent round shape by stable product formation and beautiful appearance of products by slow cooling of cooling and removing the cause of defects such as bubbles.

Example 2

Instead of silicone oil, food products (soybean essential oils) were formed in the same manner as in Example 1, and the problems caused by examining the appearance and product condition were eliminated, but the viscosity of the edibles was slightly higher than that of silicone oil, and the transparency was inferior. Due to the disadvantages are not effective in use, there may be inconvenience in appearance and use depending on the degree of oil remaining on the product surface.

Comparative Example 7

After the production of the final product by using the silicone oil of Example 1 and the edible oil of Example 2 after cutting to a suitable size, to the cooling water (water) in order to induce a faster cooling of the product of the remaining heat remaining in the resin As a result of the immersion, the bubble generation resulted in a small adverse effect.

Example 3

Extrude and cool in the same manner as in Example 1 using polymethyl methacrylate resin, but in consideration of the glass transition temperature of the resin, the oil heated to 100 ~ 120 ℃ in the tank of the first stage, the tank of the second stage The oil heated to 90 to 110 ° C. and the oil heated to 80 to 100 ° C. in the third stage of the tank were circulated and supplied at a constant temperature. As a result, a continuous product of 50 mm or less could be produced.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Example 1 Example 2 Comparative Example 7 Example 3 Bubble generation Occur Occur Occur Occur Occur Occur Not Occurred Not Occurred Occur Not Occurred Product appearance usually usually usually Bad Good Good Good Good Good Good Oil removal piece - - - - usually usually usually Bad Bad usually Operational Castle Good Good Good Bad usually usually usually usually usually usually Cooling Great Great Great Great usually usually usually usually usually usually Cooling process Great Great Great usually usually usually usually usually Great usually And thickened acid Impossible Impossible Impossible Impossible Impossible Impossible Great Great Impossible Great Other resinous availability usually usually usually usually usually usually Great Great usually -

Note) (1) With / without bubble: Classified into occurrence and no occurrence.

(2) Product appearance quality: It only compares the marks and scratches on the surface of the product.

(3) Convenience for oil removal: The use of cooling water does not require separate oil removal, and it is difficult to remove due to the high viscosity when using edibles.

(4) Work safety: The process using cooling water ensures the safety of the work, but the safety of the work is reduced by using the relatively heated oil.

(5) Coolability: Compared only to the cooling rate, the cooling rate is very good when using the cooling water, but it is impossible to apply the product due to the bubbles

(6) Shortening of cooling process: It compares only the degree of shortening of the process according to the cooling rate. It is possible to shorten the process when using the cooling water, but it is impossible to apply the product due to the bubbles.

(7) High-thickness productivity: Compared to the processing and productivity of products with excellent appearance by eliminating bubbles in producing 15mm or more and 50mm or less.

(8) Other resin applicability: In case of using cooling water, the applicable items are limited according to the type of resin, but molding of applied resin by blocking pore formation by blocking polymer fluidity in high temperature state inside resin according to this development method Stable quality improvement by processing is possible.

As described above, the product produced by the molding method according to the present invention is beautiful in appearance, excellent in transparency and does not require secondary processing, and compared to the air cooling method, the rationalization of the factory and the overall manufacturing cost due to the reduction of the unit process It is possible to reduce the defect rate of products due to bubble generation, and above all, and to produce high thickness molded products of polycarbonate and polymethyl methacrylate resin by securing excellent moldability through stable cooling process and maintaining vacuum state. It works.

In particular, through the present invention to secure the effect of blocking the flow of polymer by the uncooling of the inner layer of the resin compared to the surface cooling by rapid cooling by the cooling water to secure the possibility of applying the cooling process of other resins, and has been dependent on imports Low-quality polycarbonate thick-thick products have a great effect on the plastic processing and application industries through the application of development facilities as well as the import substitution effect.

Claims (5)

In the method for molding an engineering plastic having a circular or polygonal profile by a release extrusion method, The sol resin discharged through the final molding die of the extruder is passed through a three-stage vacuum tank in which the vacuum gauge pressure at each stage is maintained in the range of -500 to -700 mmHg. The oil heated in the temperature range of the glass transition temperature of the resin within +20 ℃) is supplied and circulated, and the oil heated in the temperature range of (the tank setting temperature of the first stage-within 20 ℃) of the second stage is supplied. The tank of the third stage is supplied and circulated, and is manufactured by supplying and circulating the oil heated in the temperature range of the tank of the second stage (within the set temperature of -20 ° C of the second stage), and the thickness of the molded resin is 15 to 50 mm. Forming method of engineering plastics by the release extrusion method characterized in that. According to claim 1, wherein the resin is a polycarbonate resin, the oil heated to 130 ~ 150 ℃ in the vacuum tank of the first stage, the silicon oil heated to 120 ~ 140 ℃ in the vacuum tank of the second stage, Molding method of engineering plastics by the release extrusion method characterized by supplying the silicone oil heated to 110-130 degreeC to the 3rd stage vacuum tank. The method of claim 1, wherein when the resin is a polymethyl methacrylate resin, the silicone oil heated to 100 ~ 120 ℃ in the vacuum tank of the first stage, and heated to 90 ~ 110 ℃ in the vacuum tank of the second stage An oil is supplied to the vacuum tank of the third stage, and the oil heated to 80 to 100 ° C. is formed. The method of forming an engineering plastic according to any one of claims 1 to 3, wherein the oil is a silicone oil. The tank of claim 1, wherein the tank of the first stage has a length of the tank so that the sol resin can stay within 1 to 2 minutes, and the vacuum tank of the second stage is 1/3 of the length of the first stage. It has a large length of 2 to 2 times, the vacuum tank of the third stage has a length of 1/3 to 2 times larger than the length of the second stage, the molding method of engineering plastics by the release extrusion method.