RU2233742C1 - Method of manufacture of shaped articles by extrusion - Google Patents

Abstract

FIELD: polymers reprocessing.

SUBSTANCE: the invention presents a method of polymers reprocessing and manufacture of shaped articles of by extrusion. The method provides, that first an extrusion material is produced from polymers melt by extrusion. Then it is fed into a calibrating device and sized for shaping of the given geometrical sizes of the article with following crystallization of the polymer. At that they use the calibrating device, the housing of which has the upper and lower cooling plates, the sealing slats and cooling grooves. The forming surfaces of the calibrating device are placed on the molding inserts. The upper and lower cooling plates and the forming inserts are out of aluminum or its alloys. Ridges of the cooling grooves are previously rounded off. The width of the cooling grooves is chosen proceeding from the visco-elastic features of the polymers. The invention allows to receive necessary rate of crystallization of polymers at a smaller difference of temperatures of a melt and the used refrigerant, to expand a range of refrigerants used at calibration and to increase efficiency of the process.

EFFECT: the invention allows to get the necessary rate of crystallization of polymers, to expand a range of refrigerants used at calibration, to increase efficiency of the process.

11 cl, 4 dwg

Description

FIELD OF THE INVENTION

The invention relates to methods for processing polymers, in particular to the manufacture of shaped products by extrusion. Such products are widely used as packaging material, as it compares favorably with its counterparts in its greater strength, resistance to moisture and aggressive environments, as well as the possibility of repeated use. Profiled products obtained by extrusion are also widely used in electronic, instrument-making and other industries.

State of the art

The prior art method for the manufacture of hollow core products from thermoplastic polymers by extrusion, disclosed in the copyright certificate SU 806446 A (V.M. Listkov et al.), 02.23.81, B 29 C 47/00. The specified method includes sequential operations of extrusion of a hollow profile billet, blowing it, calibrating it using pneumatic or vacuum pressing of the billet to the working cavity of the calibrator (see also G. Shnekel. Screw presses for plastics. L .: Goskhimizdat, 1962, p. 380- 390), cooling the calibrated workpiece in a cooling bath and winding the resulting product on a winding unit. The disadvantages of this manufacturing method are the insufficient surface strength of the product required for the packaging material.

There is also known a method and a comprehensive extrusion line for the production of sheet shaped products from polymer materials by extrusion, disclosed in the application DE 2618358 A1 (COVEMA S. 1.), 11.11.76, 29 F 3/00 (IPPC), and COVEMA method and complex extrusion line for extruding the production of packaging material from polymeric materials in the form of profiled sheet products, disclosed in the article PROFILE LINE PRODUCES CORRUGATED PACKAGING from the journal "PLASTICS TECNOLOGY", 1978, No. 1, p.21, 23. This method lies in the fact that sequentially produce e extrusion of molten polymer material through a slotted extrusion die to form an extrudate in the form of a sheet profile with two flat surfaces and longitudinal channels (cavities), with up to 300 channels on a 205 cm (80 inch) wide sheet. Then, the obtained extruded sheet is calibrated by means of a two-stage calibration device equipped with a cooling device in the form of a cooling jacket to form the geometric dimensions of the extruded sheet and crystallize the polymer, while the cooling device has eight upper and eight lower cooling zones. The waste resulting from the calibration is fed into an integrated granulator for recycling in an extruder. After calibration, the extruded sheet is surface-heated in a heat chamber and cooled in a cooling device provided with a fan. This device is designed to relax and smooth the surface of the sheet before printing in the device for applying two-color printing with an integrated device for processing the sheet with a corona electrode. At the last stage, a transverse cutting of the extruded sheet is carried out in an automatic cutting device, after which the extruded sheet pieces are stacked using an automatic self-stacker (receiving device).

There is also a known method of manufacturing sheet shaped products from polymer materials by extrusion (see RU 2138395 C1, 29 C 47/00, 09/27/1999). This method consists in the fact that the melt of the polymeric material is successively extruded through a slit extrusion head to obtain an extruded sheet in the form of a profile structure with longitudinal cavities and flat outer surfaces. The resulting extruded sheet is then calibrated by means of a calibration device provided with at least one cooling jacket to form the geometric dimensions of the extruded sheet and crystallize the polymer. Extrusion of the extruded sheet is carried out using the first pulling machine. The extruded sheet is then subjected to surface heating in a heat chamber, the heated sheet is cooled in a cooling device, the extruded sheet is transversely cut in a cutting device, and the extruded sheet is stacked using a receiving device. Moreover, according to the invention, after cooling the extruded sheet in a cooling device, protective films are applied to the upper and / or lower surfaces of the extruded sheet using a second pulling machine comprising a protective film applying device. The protective film is fed into the pulling rolls of the second pulling machine together with the extruded sheet and is rolled by the rolls to the corresponding surface of the extruded sheet, while in the second pulling machine the tension of the extruded sheet is created, which is required for the optimal course of the above heat treatment processes. The specified method is the closest analogue (prototype) of the present invention for the combination of essential features.

The disadvantage of this method, as well as other methods mentioned above, is the low productivity of the processing process in view of the fact that the shaping surfaces of the calibrating devices used in the above methods are made of corrosion-resistant or so-called "black" steels, which are known to have low thermal conductivity, in connection with which during the processing of polymers it is necessary to use additional time and additional devices to maintain the appropriate temperature of the forming surfaces of the caliber, which ultimately affects the productivity of the polymer processing process.

Disclosure of invention

The problem to which the claimed invention is directed is to create a new method for manufacturing shaped products by extrusion by using an improved calibrating device in a new design in order to increase the productivity of the polymer processing process, as well as eliminate the above-mentioned disadvantages.

The technical result achieved during the implementation of the invention is to increase the productivity of the process of manufacturing shaped products from polymer materials by extrusion, to achieve the necessary crystallization rate of polymers at a lower temperature difference between the melt and the refrigerant used, and also to expand the range of refrigerants used in calibration.

A method of manufacturing shaped products by extrusion, which ensures in accordance with the present invention the achievement of the above technical result in all cases to which the requested amount of legal protection applies, can be characterized by the following set of essential features.

A method of manufacturing shaped products by extrusion, in which an extrudable material is obtained by extrusion of a polymer melt, then it is fed to a calibration device and calibrated to form the geometric dimensions of the product and crystallized polymer, and then the resulting product is further processed, according to the claimed invention, the extrudable material is fed into a calibration device, the housing of which contains upper and lower cooling plates, sealing strips and cooling channels, and its forming surfaces are placed on forming inserts, the upper and lower cooling plates, as well as forming inserts are made of aluminum or its alloys, while the edges of the cooling channels are pre-rounded and, based on the viscoelastic properties of the polymers, the width of the cooling channels is selected.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, the upper and lower cooling plates, as well as the forming inserts of which, in order to increase their wear resistance and corrosion resistance, are subjected to electrochemical treatment to obtain an anode oxide coating known on their surface as hard anodizing.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, the upper and lower cooling plates of which are made in the form of two half-matrices, providing a tight fit of the forming inserts.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, in the cooling plates of which cooling channels in the form of coils are placed.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, the upper and lower cooling plates of which are connected by coupling bolts.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, the forming inserts of which are made interchangeable to obtain products of various shapes in one calibration device.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, the forming inserts of which are made in the form of cylindrical elements with forming channels.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, the forming inserts of which are fixed with a key.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, which contains fittings for supplying and discharging water and vacuum.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, the width of the cooling channels of which is from 0.5 to 1.5 mm.

In addition, in special cases of the method, the extrudable material can be fed into a calibration device, the radius of curvature of the edges of the cooling channels of which is from 0.1 to 0.3 of the width of the cooling channels.

Due to the high heat-conducting properties of aluminum and its alloys, from which it is proposed to shape the surfaces of the calibrating device used in the manufacturing process of profiled products, the required crystallization rate of the polymer is achieved at a lower temperature difference between the melt and the refrigerant, because aluminum has high heat-conducting properties (0.25 ... 0.52 cal / cm · s · ° C versus 0.032 ... 0.07 cal / cm · s · ° C in stainless steels) improves heat removal, increases the cooling rate polymer melt, which, in turn, allows you to:

- increase the productivity of the molding process up to 2 times,

- increase the temperature of the refrigerant (for example, up to 40 ° C for hard PVC).

- reduce the length of the calibrating device,

- eliminate the need for additional cooling zones,

- use air (natural or forced) cooling,

- expand the range of choice of refrigerants used in calibration.

Brief Description of the Drawings

The possibility of carrying out the invention, characterized by the above set of essential features, as well as the possibility of implementing the purpose of the invention can be confirmed by graphic materials (figure 1, figure 2, figure 3 and figure 4), not limiting all possible options for its implementation.

As can be seen from the graphic materials, according to the claimed invention, the caliber used in the method consists of upper (1) and lower (2) cooling plates connected by coupling bolts (5), sealing bars (3) and (4) of water and vacuum channels, supports ( 7), fittings (6) for supplying and discharging water and vacuum, dowels (9), and replaceable forming inserts (8).

In the cooling plates of the calibrating device, water channels (10) for the refrigerant in the form of coils and a vacuum manifold (11) are provided, which allows air to be taken from the internal cavity of the plates at the junctions of the forming inserts (8).

The implementation of the invention

The following is one way of implementing the claimed technical solution, not limiting all possible options for its implementation.

The extrudable polymer melt enters the forming channel of the caliber, where, due to the vacuum created in the vacuum channels, it is pressed against the forming surfaces of the forming inserts.

Cooling and crystallization of the melt is carried out by heat transfer:

- from the surface of the melt to the forming surfaces of the forming inserts;

- from forming inserts to cooling plates with cooling channels for the refrigerant.

As it moves along the gauge, the melt acquires the necessary degree of crystallization and, accordingly, rigidity, ensuring both the preservation of the sectional shape given to it and the longitudinal strength necessary to overcome the pulling forces through the gauge.

For the normal process of calibrating the polymer melt, the edges of the cooling channels are pre-rounded and the channel width is selected based on the viscoelastic properties of the polymer being processed. So, for example, for extruded polycarbonate grades, the channel width is from 0.6 to 0.8 mm, while for rigid polyvinyl chloride 1, -1.2 mm. The radius of the rounding of the channel edges is from 0.1 to 0.3 of the channel width.

After processing in a calibrating device, the resulting product is sent for further processing depending on the technological need. This can be, for example, surface heating of a product, its cooling, cutting, etc.

The implementation of this method was carried out, for example, when calibrating products made of rigid polyvinyl chloride (rigid PVC) at a coolant temperature of 30-40 ° C, while similar products calibrated using steel gauges when the temperature exceeds 12-15 ° C of coolant, not having a sufficient crystallization rate, they "float", i.e. receive longitudinal elongation in caliber, which, in turn, affects the decrease in productivity of the molding process and entails the need to use additional cooling devices (along with the formation of additional cooling zones), as well as a rather limited choice used in the molding process of refrigerants having a narrow Operating temperature range. The width of the cooling channels during processing of rigid polyvinyl chloride was 1.1 mm, and the radius of the rounding of the channel edges was 0.22 mm.

The implementation of the proposed method has been achieved by increasing the productivity of the molding process up to 2 times, increasing the range of "working" temperatures of the refrigerant (for example, up to 40 ° C for hard PVC), reducing the length of the calibrating device. In carrying out the invention, the need for additional cooling zones and the use of appropriate equipment for this were eliminated. Now you can use air (natural or forced) cooling.

Claims (11)

1. A method of manufacturing shaped products by extrusion, in which an extrudable material is obtained by extrusion of a polymer melt, then it is fed to a calibration device and calibrated to form the geometric dimensions of the product and crystallize the polymer, and then further processing of the obtained product is carried out, characterized in that the extrudable material served in a calibration device, the housing of which contains the upper and lower cooling plates, sealing strips and cooling channels, its shaping surface placed on the forming inserts, the upper and lower cooling plates as well as forming the insert is made of aluminum or its alloys, wherein the edge cooling channels and pre-rounded proceeding from visco-elastic properties of polymers selected width of the cooling channels. 2. The method according to claim 1, characterized in that the extrudable material is fed into a calibration device, the upper and lower cooling plates, as well as the forming inserts of which, in order to increase their wear resistance and corrosion resistance, are subjected to electrochemical treatment to obtain an oxide anode on their surface coatings known as “hard anodizing”. 3. The method according to any one of claims 1 and 2, characterized in that the extrudable material is fed into a calibration device, the upper and lower cooling plates of which are made in the form of two half-matrices, providing a tight fit of the forming inserts. 4. The method according to any one of claims 1 to 3, characterized in that the extrudable material is fed into a calibration device, in the cooling plates of which there are cooling channels in the form of coils. 5. The method according to any one of claims 1 to 4, characterized in that the extrudable material is fed into a calibration device, the upper and lower cooling plates of which are connected by tie bolts. 6. The method according to any one of claims 1 to 5, characterized in that the extrudable material is fed into a calibration device, the forming inserts of which are made replaceable to obtain products of various shapes in one calibration device. 7. The method according to any one of claims 1 to 6, characterized in that the extrudable material is fed into a calibration device, the forming inserts of which are made in the form of cylindrical elements with forming channels. 8. The method according to any one of claims 1 to 7, characterized in that the extrudable material is fed into a calibration device, the forming inserts of which are fixed with a key. 9. The method according to any one of claims 1 to 8, characterized in that the extrudable material is fed into a calibration device, which contains fittings for supplying and discharging water and vacuum. 10. The method according to any one of claims 1 to 9, characterized in that the extrudable material is fed into a calibration device, the width of the cooling channels of which is from 0.5 to 1.5 mm. 11. The method according to any one of claims 1 to 10, characterized in that the extrudable material is fed into a calibration device, the radius of rounding of the edges of the cooling channels of which is from 0.1 to 0.3 of the width of the cooling channels.

Images