RO121275B1 - Process and composition for producing ribbons and yarns made of thermoplastic materials - Google Patents

Abstract

The invention relates to a process and a composition for producing ribbons and yarns made of thermoplastic materials employed for making fabrics used for manufacturing bags or flexible containers. According to the invention, the process consists in that, in order to increase the resistance to stretching, the foil resulting after the extrusion process, made up of thermoplastic materials, being in elastic solid state, is drawn onto a system of drawing drums, cut into ribbons or yarns of preset size, elongating the so formed ribbons or yarns on an elongating drum, followed by stretching while heating up to a temperature of 180A C simultaneously the elongating on the elongating drum systems, and fixing on reels, the temperature being the same or different. The elongating and fixing drum system is provided with a rollers group of which the ribbons or the yarns pass with a speed and a temperature lower by 10% than the one of the stretching group.

Description

The invention relates to a process for obtaining tapes and yarns from thermoplastic materials, intended mainly to produce fabrics used for making flexible bags or containers, but also used as such for binding operations. Thus, in order to obtain small or large bags, a flexible container type, polypropylene strips, white or colored, fibrilized yarn, white or colored yarn, resistant bands can be obtained, in particular strap type, mesh type fabric, lace or sealing cord, tubular or flat fabric, whether or not loose.

It is known that from polyethylene and polypropylene, films are obtained from which later tapes or yarns can be obtained, necessary for the fabrication of some fabrics.

Thus, according to standards, such as STAS 6023-86, which refers to “Bags made of Liberian, mixed and polypropylene fabrics, it is specified that fabrics made of Liberian, mixed or polypropylene yarn are used in the manufacture of bags.

It should be noted that, for the purpose of obtaining polypropylene yarns, there are no technological conditions imposed by the standards in force, but there are standards that impose certain determinations of the technical characteristics. Thus, STAS 7271-65 refers to the determination of the fineness (linear mass), STAS 7272 -88 regarding the determination of the breaking load and the elongation at break.

According to the Engineer's Manual - HUNTE (p. D 26, D27), thermoplastic materials are polymerized, amorphous or partially crystalline materials, as in the case of polypropylene or polyethylene, with chain-shaped macromolecules, which are either linear or branched and are bound (termolable) only by physical forces of attraction (secondary valence forces). Below the so-called vitrifying temperature, the thermoplasts are solid, above this temperature, the secondary valence forces, which determine the cohesion of the solid, are less active, and the molecules can deform. In the case of partially crystalline thermoplasts, of which polypropylene and polyethylene are part, the amorphous mass is also deformable, but the crystalline mass represents an obstacle which determines by their high cohesion a resistance, accompanied by a constant of the stability of the form. Above the so-called melting temperature of the crystals and the crystalline mass passes into an amorphous state, and the material becomes deformable. After the melting temperature is exceeded, all the thermoplastics pass into the liquid phase (viscous flow) and when the decomposition temperature is exceeded, the molecular chains are destroyed. Maximum operating temperatures are material dependent and range in the range from about 70 to 130 ° C.

In this sense, a solution described in patent RO 114010, which treats a polypropylene tape, a process for obtaining it and a loose polypropylene fabric is known.

The composition is made of a mixture of 85 ... 98% polypropylene, 1 ... 3% premix, UV stabilizer with polyethylene or polypropylene, which has 20% active substance, 1 ... 5% premix of CaCo ₃ with polyethylene. or polypropylene with 70% active substance and maximum 7% low density polyethylene.

The process consists of introducing the mixture into an extruder, provided inside with 5 heating zones, whose temperature reaches 255'0, after which the melt is filtered through a sieve with automatic change, determined by the pressure, which must be between 110 and 170 at, the film is cooled to water at 32 ... 40 ° C, is passed through two rollers, after which the water from the film is scraped and absorbed, cut into strips, tensioned, stretched with warm air between two groups of buckets.

The disadvantage of this chosen solution is that of the polypropylene yarns thus obtained, a loose fabric is made, from which a narrow range of flexible containers will be made.

The technical problem solved by the invention is that by applying a process of stretching the yarns, after cooling the film, on a drum system, yarns with high tear resistance are obtained, which can be used in several types of fabrics, without requires their fall.

RO 121275 Β1

The process of obtaining tapes and yarns from thermoplastic materials, according to 1 invention, removes the disadvantages presented above, in that, in order to increase the tensile strength of the traction, the foil, resulting after extrusion from the thermoplastic materials, 3 is in a solid elastic state. , is drawn on a system of firing drums, divided into strips or wires of predetermined size, followed by a stretching of them on 5 stretching drums, followed by stretching, with heating up to a temperature of 180 "C, together with the stretching on another stretching and fixing drum system, which also includes a group of 7 rollers, the temperature on which they are the same or different, after which the strips or wires are cooled to 15 ° C. 9

The speed of displacement of the thermoplastic composition through the heating zones of the extruder is determined as a product between the number of belts, the speed of the tread drum system and the desired fineness.

In order to avoid the dimensional instability of the belts in time, in the stretching process, the stretching and fixing drum system is provided with a group of rollers, which the belts or wires travel at a speed and a temperature lower than 10% compared to the one of the stretching group 15.

For obtaining yarns and belts used in small bags up to 50 kg, a 17 stretching ratio determined as the ratio of the speed of the final stretch drum and the initial drum and which determines an elongation of 25 ... 35% is chosen. and for bags larger than 50 kg, 19 a stretching ratio is chosen which determines an elongation of 20 ... 25%.

By applying the invention, the following advantages are obtained: 21

- high yield, high yields;

- Belts and wires have a wide range of uses, 23

- reduced banding time;

- high tensile strength, 25

- do not contain toxic substances;

- the technical characteristics are controllable.27

Following are examples of the production of polypropylene or polyethylene webbing and yarns, according to the invention, which are not limiting.29

The strips are yarns whose width and thickness is much smaller than their length, their fineness ranges from 400 to 10,000 den.31

The fibrilized thread or thread is obtained by performing multiple longitudinal cuts at a small angle of -Γ, discontinuous, along the entire length of the belt. The fibrillation is done on a fibrillating device that has fixed bars with special needles on a cylinder.

depending on the technical characteristics of the belt or thread, the composition 35 of their obtaining is established, respectively the materials that will enter the composition.

Thus, in a first step of the process, the materials for the 37 composition of obtaining the tapes and wires from thermoplastic materials are established, as follows.

In order to obtain a material with properties and characteristics that make it resistant to tensile and deformation demands, the materials are chosen with certain material properties and characteristics. 41

The basic raw material is polypropylene or polyethylene in the form of granules and which represents between 85 to 90% of the total mass of the composition. Both polypropylene and 43 and polyethylene can be chosen when making the composition of the same type of material, respectively with the same characteristics or as a mixture of the same material, but of several types, 45 respectively with different characteristics.

RO 121275 Β1

Polypropylene is chosen with the following characteristics: flow rate at 1.2 to 3.5 g / 10 min, density at 23 ° C from 0.90 to 0.917g / cm ³ , modulus of elasticity 0.4 to at 0.9 kN / sqm, the tensile strength N / sqm between 20 and 30; softening point minimum 150 ° C, melting flow rate of minimum 1.2 g / 10 min and maximum 2 g / 10 min, elongation at break 500% minimum.

Polyethylene is chosen with the following characteristics: density, at 23 ° C, from 0.91 to 0.97 g / cm ³ , modulus of elasticity 0.2 kN / sqm, tensile strength N / sqm between 25 and 30.

Another important component of the composition is the filling materials, of which calcium carbonate is the most important, this being an additive with the role of improving the mechanical characteristics, processing, and also realizing a certain opacity of the strip.

Calcium carbonate CaCO ₃ (also known as "filler") is added in polypropylene or polyethylene in granular form, in the proportion of 1 to 5% of the total mass of the composition. In the production of belts used in small bags, it is preferable to use 2 to 3% calcium carbonate (CaCO ₃ ), to obtain a better elongation, which favors a better resistance to the sewing areas of the fabric.

CaCO ₃ calcium carbonate is chosen with the following characteristics: CaCO ₃ concentration between 72 and 83%; flow rate (190 ° C / 2.16 kg) less than or equal to 10, humidity up to a maximum of 5%, preferably not containing cadmium, lead, diarylides, without other heavy materials, temperature resistant to 300 ° C.

Another component of the composition is the UV UV stabilizer, designed to increase the resistance to UV radiation, which represents 0.5 to 2%.

Select a UV with pigment / additive concentration of 19 to 22%, humidity of maximum 0.5%, flow rate between 20 and 50 g / 10 min.

Depending on the desired stabilization, various stabilizer concentrations are introduced, as an example for a Q-Panel irradiation (UVB 313 lamps, which provides 8 hours irradiation at 60 ° C, 4 hours condensation at 50 ° C) of:

- 60 h, a stabilization with approximately 0.5% stabilizer is required, which may also contain up to 20% active substance;

- 120 h, a stabilization with approximately 1% stabilizer is required, which can optionally contain up to 20% active substance;

-180 h, a stabilization with approximately 1.5% stabilizer is required, which can optionally contain up to 20% active substance.

Another component is a dye, which is optional, and is added to obtain polypropylene or polyethylene strips or yarns in colors.

Also optional, they can be used in the composition, without altering the mechanical and processing characteristics of polypropylene or polyethylene belts or yarns, maximum 10% granules obtained from the wastes of polypropylene or polyethylene or polyethylene yarn recovered from the technological flow, called "regulated" ".

After establishing these recipes, in a system of feeding - homogenization of the components or in an installation containing such a system, the materials are mixed, for 1 to 2 minutes.

The resulting mixture is first maintained in an area where the temperature is maximum 45 ° C, in this area being prepared to enter some heating zones.

The composition thus prepared, in another important step, is subjected to a heating treatment carried out in several stages of temperature, followed by a stage in which the mixture is cooled and filtered, followed by a proper extrusion step. Extrusion is a process of processing, in itself known, whereby the plastic materials are forced to pass through a nozzle that gives them the desired shape.

EN 121275 Β1 for this purpose, an extruder-type installation may be used, which may also contain 1 feed installation, mixing the materials intended for the composition, and which shall be provided mainly with 1 to 5 heating zones, a filtering zone of of the mixture, pump 3 which ensures its movement to a nozzle through which the mixture passes directly into a cooling zone, all programmed from a control panel. 5

Prior to the first step of increasing the temperature of the mixture, there is, as we have specified, an inlet zone thereof, in which it is maintained at a normal temperature of 7 maximum 45 ° C, in order not to create an adhesion between the compounds of the mixture. at the entrance to the heating zones. 9

From this area, the mixture passes into the first heating zone of the extruder type plant, where the temperature is 220 to 225 ° C, depending on the flow rate of polypropylene or polyethylene, the temperature in the first step can be changed by 5 ° C.

The particles of the mixture are gradually transformed to the state of viscosity, but without 13 the molecular mass being destroyed.

starting from zones 2 to 5, several heating stages take place, when the temperature will gradually increase by 5 ° C on average, up to a temperature between 240 and 250'C, depending on the flow rate of polypropylene or polyethylene. 17

The speed of movement of the mixture through the heating zones is determined by the speed of the pump, which is determined according to the type of belt or wire that is to be obtained. 19

After these successive increases in temperature, the actual extrusion takes place, whereby the plastic material is first filtered by any impurities, on an area of 21 cooling which has a temperature of 70 to 190 ° C.

Another stage of heating of the material follows up to a temperature corresponding to the flow temperature 23, respectively 240 ° C, maximum 250 ° C, from where the viscous material is driven by the pump, which ensures a constant flow rate on a tubular portion. , 25 necessary to maintain a constant pressure, both at the inlet and in the section of a nozzle, pressure necessary to ensure a uniform thickness of the liquid film in the form of a film, 27 resulting from the mixture.

The film passes through a water-cooling bath at 30 ° C, maximum 45 ° C, 29 where the material returns to the elastic solid state in the form of a foil.

The foil is stretched by pulling on a firing drum system, in order to cut it 31 into strips or wires of dimensions determined according to their use.

After the film is cut into strips or yarns, their stretching takes place on a first system 33 stretching drum, followed by a stretching process, which consists of heating the material up to a maximum of 180 ° C, corresponding to the softening interval, in an area of Heating 35 in which concurrent takes place and the stretching that is done on several stretch drum systems, the temperature on these drum systems may be different. After stretching, the strips 37 or strands are cooled gradually.

The stretching produces an orientation of the macromolecular chains in the direction of action of the elongation force, which causes the tensile strength of the straps or wires to increase.

The macromolecular orientation creates internal stresses, which have the effect of 41-dimensional instability of the bands over time.

To avoid this instability, a group of rollers or a system of 43 fastening drum is provided, which the belts or wires travel at a speed and a temperature lower than the stretching group, by approximately 10%. 45

For belts used in the small bag of 25 to 50 kg, a small stretch ratio of 1: 4 to 1: 5.5 is preferred, which produces a large elongation of 25 to 35%, and for 47 belts used in large bag, with a stretch ratio of 1: 5.8 to 1: 6.3, which results in an elongation of less than 20 to 25%. 49

RO 121275 Β1

In large bags, from 500 to 2000 kg, a smaller elongation is preferred, in order to keep the final dimensions of the bags after loading. The stretch ratio is determined as the ratio of the velocity of the final stretch drum and the initial stretch drum.

The strips or wires are gently cooled in stages to a minimum temperature of 15'C, after which they are sucked and wound on coils by various winding installations.

Throughout the technological process of making the belts and wires, the waste is adsorbed, ground and can be re-introduced in the manufacturing process, in the percentages specified above.

Example 1. It is desired to make a webbing with a width of 2.5 mm, a fineness of 650 den for the bag fabric and the materials that will form the composition are chosen.

- 90 kg polypropylene with the following characteristics: as a result, the granules are uniform in color, the melt flow rate is 3.14 g / 10 min, density at 23 ° C of 0.9143 g / cm ³ , tensile strength at break of 26.7 N / sqm, elongation at break 590%, shock resistance 41.09 j / m, softening point 150.2 ° C;

- 6 kg regranulate based on polypropylene with close characteristics;

- 3.5 kg of calcium carbonate CaCO ₃ , with the following characteristics: 75% CaCO ₃ concentration, 75% inorganic matter concentration, 0.5% humidity, no cadmium, lead, diarylides, other heavy materials, flow rate 10, set at 190 ° C / 2.16 kg;

- 0.5 kg white dye.

After establishing these recipes, through a system of feeding and homogenizing the components, they are mixed, for 1 to 2 minutes.

The resulting mixture is first maintained in an area where the temperature is about 30 ° C, in this area being prepared to enter the heating zones of an extruder-type installation.

From this area, the mixture passes into the first heating zone of the extruder type plant, where the temperature is 225'C, increases in the second zone to 230 ° C, in the third zone to 235'C, and in the fourth zone and fifth, maintain the temperature of 240 ° C.

The particles of the mixture are gradually transformed to the state of viscosity, but without the destruction of the molecular mass.

The speed of movement of the mixture through the heating zones is determined by the speed of the pump, which is established as a product between the number of belts, the speed of the stretch drum system and the fineness established.

After these successive increases in temperature, the extrusion itself takes place, whereby the plastic material is first filtered by any impurities, on a cooling zone which has a temperature of 225 ° C before the filter and 165 ° C after the filter. .

Another stage of heating of the material follows to a temperature corresponding to the flow temperature, respectively 240 ° C, from where the viscous material is driven by the pump, which ensures a constant flow on a tubular portion, necessary to maintain at a constant pressure, both at the inlet and in the section of a nozzle, pressure necessary to ensure a uniform thickness of the liquid film in the form of film, resulting from the mixture.

The film passes through a water-cooling bath at 33 ° C, where the material returns to the elastic solid state in the form of a foil.

The foil is stretched by pulling on a draw drum system in order to cut it into strips or wires of dimensions determined according to their use.

After the film is cut into strips or yarns, their extension takes place on a first stretch drum system, followed by a stretching process, which consists of heating the material up to a maximum of 160 ° C, in a heating zone where it occurs simultaneously. and stretching, which is done on several stretch drum systems.

RO 121275 Β1

After stretching, the belts or wires are gently cooled in stages on a drum system 1 fastening to a temperature of at least 15 ° C, after which they are sucked and wound on coils by various winding installations. 3

Example 2. It is desired to make a belt with a width of 2.5 mm, a thickness of 1800 den, for large bag fabric and choose the materials that will form the composition. 5

The composition is made of:

- 85.5 kg polypropylene with the following characteristics: in appearance, the granules are of 7 uniform color, the melt flow rate is 3.14 g / 10 min, density at 23'C of 0.9143 g / cm ³ , the resistance to tensile breakage of 26.7 N / sqm, elongation at breakage 590%, shock resistance 91.09 j / m, softening point 150.2'C;

- 8 kg regranulate based on polypropylene with close characteristics; 11

- 4 kg of calcium carbonate CaCO ₃ , with the following characteristics: 75% CaCO ₃ concentration, 75% inorganic matter concentration, 0.5% humidity, cadmium free, 13 lead, diarylides, other heavy materials, flow rate 10, set at 19O'C / 2.16 kg;

- 2 kg UV type PP 921 H with the following characteristics: pigment / additive concentration of 19.09%, humidity 0.19%, flow rate 26.6 g / 10 min;

- 0.5 kg white dye. 17

After establishing these recipes, by means of a system of feeding and homogenization of the components, they are mixed, for 2 min.19

The resulting mixture is first maintained in an area where the temperature is about 35 ° C, in this area being prepared to enter the heating zones of a 21 extruder type plant.

From this area, the mixture passes into the first heating zone of the extruder type plant, 23 where the temperature is 220'C, increases in the second zone to 225'C, in the third zone to 230'C, in the fourth zone to 235 'C, and in the fifth zone the temperature of 240'C.25 is maintained

The particles of the mixture are gradually transformed to the state of viscosity, but without the destruction of the molecular mass.27

The speed of movement of the mixture through the heating zones is determined by the speed of the pump, which is established as a product between the number of belts, the speed of the 29-stroke drum system and the fineness established.

After these successive increases in temperature, the extrusion itself takes place through 31, where the plastic material is first filtered by any impurities, on a cooling zone which has a temperature of 220'C before the filter and 160 ° C after the filter. . 33

Another stage of heating of the material follows to a temperature corresponding to the flow temperature, respectively 240'C, from where the viscous material is driven by the pump, which ensures a constant flow on a tubular portion, necessary to maintain at a constant pressure. , both at the inlet and in the section of a nozzle, pressure required to ensure a uniform thickness of the liquid film film, resulting from mixing.

The film passes through a water-cooling bath at 35 ° C, where the material 39 returns to the elastic solid state in the form of a foil.

The foil is stretched by pulling on a draw drum system for cutting it 41 into strips or wires of dimensions determined according to their use.

After the film is cut into strips or wires, it is stretched on a first system 43 stretch drum, followed by a stretching process, which consists of heating the material up to a maximum of 166'C, in a heating zone where it takes place concurrently with the stretching 45 which is made on several stretching drum systems.

After stretching, the belts or wires are gently cooled in stages on a drum system 47 fastening to a temperature of 20 ° C, after which they are sucked and wound on coils by various winding installations. 49

RO 121275 Β1

Example 3. It is desired to make a strip with a width of 13.3 mm, a thickness of 6000 den, for the webbing and choose the materials that will form the composition.

The composition is made of:

- 92 kg polypropylene type F 401 with the following characteristics: in appearance, the granules are of uniform color, the melt flow rate is 3.14 g / 10 min, density at 23 ° C of 0.9143 g / cm ³ , the resistance to tensile rupture of 26.7 N / sqm, elongation at break 590%, shock resistance 41.09 j / m, softening point 150.2 ° C;

- 3 kg of calcium carbonate CaCO ₃ , with the following characteristics: 75% CaCO ₃ concentration, 75% inorganic matter concentration, 0.5% humidity, no cadmium, lead, diarylides, other heavy materials, flow rate 10 set at 190 ° C / 2.16 kg;

- 2 kg UV type PP 921 H with the following characteristics: pigment / additive concentration of 19.09%, humidity 0.19%, flow rate 26.6 g / 10 min;

- 3 kg blue dye.

After establishing these recipes, by means of a system of feeding and homogenization of the components, they are mixed, for 2 minutes.

The resulting mixture is first maintained in an area where the temperature is about 30 ° C, in this area being prepared to enter the heating zones of an extruder-type installation.

From this zone, the mixture passes into the first heating zone of the extruder type plant, where the temperature is 225 ° C, increases in the second zone to 230 ° C, in the third zone to 235'C, in the fourth zone to 240 ° C, and in the fifth zone the temperature of 240 ”C is maintained.

The particles of the mixture are gradually transformed to the state of viscosity, but without the destruction of the molecular mass.

The speed of movement of the mixture through the heating zones is determined by the speed of the pump, which is established as a product between the number of belts, the speed of the stretch drum system and the fineness established.

After these successive increases in temperature, the extrusion itself takes place, whereby the plastic material is first filtered by any impurities, on a cooling zone that has a temperature of 226 ° C before the filter and 166 ° C after the filter. .

Another stage of heating of the material follows to a temperature corresponding to the flow temperature, respectively 240 ° C, from where the viscous material is driven by the pump, which ensures a constant flow on a tubular portion, necessary to maintain at a constant pressure, both at the inlet and in the section of a nozzle, pressure necessary to ensure a uniform thickness of the liquid film in the form of film, resulting from the mixture. The film passes through a water-cooling bath at 33 ° C, where the material returns to the elastic solid state in the form of a foil.

The foil is stretched by pulling on a draw drum system in order to cut it into strips or wires of dimensions determined according to their use.

After the film is cut into strips or yarns, their extension takes place on a first stretch drum system, followed by a stretching process, which consists in heating the material up to a maximum of 160'C, in a heating zone where it occurs simultaneously. and the stretch which is made on several stretch drum systems where the temperature is 105 ° C, followed by a fastening drum system where the temperature is 95 ° C.

After stretching, the strips or wires cool slightly in stages to a temperature of 20'C, after which they are sucked and wrapped on coils by various winding installations.

Claims (4)

1. Process for obtaining tapes and yarns from thermoplastic materials, by heating a mixture of polypropylene in an extruder, up to 255 ° C, extruding, cooling the film, cutting into strips and stretching, characterized in that, In order to increase the breaking resistance 5 of the film, resulting after extrusion of the thermoplastic materials, in an elastic solid state, it is drawn on a system of firing drums, sectioned into strips or wires of 1 predetermined size, after which a stretching follows. on stretching drums, followed by stretching, with heating up to 180 ° C, concurrently with the stretching on 9 another stretching and fixing drum system, which also includes a group of rollers, the temperature on these being the same or different, depending on which takes place the cooling of the strips or wires up to the temperature of 15 ”C. 2. Process according to claim 1, characterized in that the speed of movement 13 of the thermoplastic composition through the heating zones of the extruder is determined as a product between the number of belts, the speed of the stretch drum system and the desired fineness. 15 3. Process according to claim 1, characterized in that, in order to avoid the dimensional instability of the belts in time, in the stretching process, the drum system of stretching and fixing is provided with a group of rollers, on which the belts or wires travel with a speed. and a lower temperature by up to 10% compared to that of the stretching group. 19 4. Process according to claims 1 and 4, characterized in that, for obtaining yarns and belts used in small bags up to 50 kg, a ratio of 21 pulls is chosen, determined as a ratio between the speed of the final stretch drum and the drum initially and which leads to an extension of 25 ... 35% and for bags larger than 50 kg, a stretching ratio of 23 is chosen which results in an elongation of 20 ... 25%.