SU1628860A3 - Process for preparation polyolefin fibrils - Google Patents

Abstract

1471097 Fibrils MONTEDISON SpA 17 Nov 1975 [19 Nov 1974] 47214/75 Heading B5B A solution emulsion or dispersion of a thermoplastic polymer especially from an olefine, acrylonitrile, acrylate, vinyl chloride, vinyl acetate or styrene, in a liquid medium is extruded through a nozzle or pipe 1 in the direction indicated by the arrow 6, where 1 comprises a convergent portion 2, a narrow portion 3 and a divergent portion 4 and is hit in portion 4 by a jet of fluid which has been expanded through jets 5 and is travelling in the direction indicated by the arrow 7. The fluid jet may comprise steam.

Description

This invention relates to the field of synthetic fibers, in particular polyolefin fibrils, and can be used to make synthetic paper.

The purpose of the invention is to increase the uniformity of the fibrils in length.

Example 1. Use a solution containing 100 g of high-density polyethylene (with a melt index of 4.5) in 1 l of solution. The solution temperature is 180 ° C, the pressure drop at the nozzles is 14 atm.

The vapor pressure at the inlet of the narrowing portion of the nozzle is 18 atm, its temperature is 205 ° C. Steam consumption 300 kg / h.

In the narrow part of the nozzle its profile is circular, and the diameter in the critical section is 6.5 mm. The diameter of the end section of the expanding nozzle section is 15.42 mm; the distance between the critical section and the end section of the nozzle is 31.8 mm.

Under these conditions, the vapor pressure near the end portion of the expanding part of the nozzle somewhat exceeds (i.e. by several mm Hg) the atmospheric pressure, and its maximum speed, determined by the conditions upstream in the nozzle’s critical section, is 900 m / s Steam expansion

OK

00 00 05

cm

corresponds to a fall in enthalpy of 115 kcal / mol.

The polymer solution is fed through 8 cylindrical nozzles arranged symmetrically on the final part of the sushivayusche - expanding nozzle. diameter of each nozzle is 2 mm. Consumption of olimeric solution 960 kg / h. Steam consumption 2.5 kg / kg fibrils.

The uniformity of the sample (1 g) along the length of the fibers:

Fibers,% Length of fibers, mm

± 0.1 mm

53

303.4

603.6

54.1

The average fiber length in this case is 3.53 mm.

After an hour of continuous operation, 120 kg of fibrils 3-4 mm long, with an apparent diameter of 40 microns, with a surface area of 7 m2 / g are obtained.

EXAMPLE 2 The same solution of polyethylene in n-hexane was used as in Example 1, at the same temperatures, pressures, and the same hourly flow rate. The vapor pressure of 2.6 kg / cm2, which was superheated to 200 ° С, the mass velocity of the vapor used as a liquid, 300 kg / h.

In addition, a device is used in which the nozzle is characterized by dimensions: the critical section diameter of 7.3 mm; the maximum diameter of the section in the expanding part is 8.7 mm; the distance between the minimum and maximum cross sections is 22.4 mm.

At the maximum cross section of the nozzle, the steam is in a superheated state at a pressure slightly above atmospheric, the maximum vapor velocity in this area of the nozzle is 607 m / s. The nozzles for extruding the polymer solution had a diameter of 2 mm.

After an hour of continuous operation, 120 kg of fibrils with a length of 4–5 mm, an apparent diameter of 40 microns and with a specific surface area of 8 m2 / g are obtained. Steam consumption 2.5 kg per 1 kg of fibrils Fibril uniformity along the length: Fibrils,% Length of fibrils, mm

± 0.1 mm

54

454.3

454.8

55

The average length of 4.54 mm. Example 3 "Concerning the preparation of fibrils from an emulsion of a solution of polypropylene in n-pentane in water. The melt index of the polypropylene used is 10. The concentration of polypropylene in the emulsion is 50 g per liter of emulsion. The weight ratio of water to 0 n-pentane in the emulsion is one.

Applicable device: nozzle for

fluid in the critical section has

diameter 11.5 mm at the end

with a maximum cross section, in the expansion of the noch of the nozzle, the diameter is

15.7 mm, the distance between the critical and maximum sections is approximately 21 mm.

The emulsion is extruded at 155 ° C and under a pressure of 21.4 kg / cm2 through 8 cylindrical nozzles installed symmetrically around the final (maximum) section of the convergent-expanding nozzle. The diameter of each of the nozzles 5 is 2 mm. The emulsion is fed through 8 cylindrical nozzles with a total volume velocity of 2200 kg / h. The volumetric rate of steam 300 kg / h. The liquid used was dry saturated steam, whose pressure at the entrance to the tapering part of the nozzle was 6 kg / cm2, temperature 200 ° C.

Under these conditions, the vapor pressure in the final portion of the expanding aperture of the nozzle part is slightly higher than the atmospheric pressure, and in this portion the maximum vapor flow rate of 715 m / s is reached, which is determined by the conditions upstream in the critical section. 40 After an hour of continuous operation, approximately 150 kg of fibrils with a length of t, 5-2.5 MMj, an average (apparent) diameter of 20 microns and a surface area (specific) of 4.1 mg / g are obtained. Steam consumption 2 kg 45 per 1 kg of fibrils.

The uniformity of the fibrils in length: Fibrils,% Plina fibrils, mm

± 0.1 mm

31.5

50 402.0

452.2

112.4

12.5

The average length of 2.12 mm.

C h

Example 4: Illustrates the production of fibrils from a two-phase polymer composition in which one of the phases is formed by molten

polyethylene (with a melt index of 5) containing liquid n-hexane, and another phase is formed with liquid n-hexane containing polyethylene in a dissolved state, the first of these phases being homogeneously dispersed in the second phase. Such a biphasic composition is obtained by heating a plant. a polyethylene thief in n-hexane, containing 100 g of polymer in 1 liter of solution, at a temperature of 200 ° C and a pressure of 17 kg / cm2.

At the indicated temperatures and pressures, the two-phase composition was extruded through 8 nozzles of the device described in Example 1 with a total space velocity of 1200 kg / h.

Steam was used as a liquid. At the entrance to the narrowing part of the nozzle, the parameters were: temperature 205 ° C, pressure 18 kg / cm2, volume velocity 300 kg / h.

The vapor pressure in the final section of the expanding part of the nozzle, where it interacts with the extruded polymer composition, is slightly higher than atmospheric, and the maximum steam velocity in this area reached 900 m / s.

After an hour of continuous operation, T50 kg of fibrils with a length of 2-2.5 mm, an apparent diameter of 25 microns and a surface area of 8 m2 / g are obtained. Consumption pair 2 kg / kg fibrils. The uniformity of the fibrils along the length: Fibrils,% Galina fibrils, mm

± 0.1 mm

62

602.3

252, A

92.5

Average length 2.32 mm. PRI me R 5

By (comparative).

fibrils are produced according to Example 1 using the same polymer, concentration and process parameters. However, the convergent-divergent nozzle used in this case has the following characteristics: the diameter of the narrowed part is 5.9 mm; the distance between the constricted and terminal parts is 21 mm;

five

0

0

five

five

the divergence angle of the expanding portion is 40 °.

The polymer used is a high density polyethylene having M.1.4.5, and a solution of 100 g of polymer in 1 l of n-hexane is used at 180 ° C and an overpressure of 14 atm.

The vapor was used as a fluid jet, which has a pressure of 18 kg / cm2 and a temperature of 205 ° C at the inlet of the converging part of the nozzle at a flow rate of 300 kg / h.

The polymer solution was extruded under the specified conditions through 4 cylindrical nozzles arranged symmetrically around the end portion (i.e. at the end of the expanding part) of a convergent-divergent nozzle, each of these nozzles having a diameter of 2 mm with a total web speed of 480 kg / h about

The uniformity of the fibrils in length: Fibrils,% Length of fibrils, mm

± 0, 1 mm

100.3

201.1

252.3

303.6

54.7

5 6.0

5More than 9 mm

Estimated average length of 2.9 mm.

Claims (1)

Invention Formula 35 A method of producing polyolefin 40 fibrils by extruding a solution, emulsion or dispersion of a polymer in n-hexane or n-heptane through a nozzle into the space for a collision with a high-velocity jet of dry centrifugal vapor directed at an angle to the flow of the solution, emulsion or dispersion of the polymer, so that, in order to increase the uniformity of the fibrils in length, the solution, 50 emulsion or polymer dispersion is extruded into the expanding zone of the Laval nozzle, and a stream of dry saturated steam is passed through this zone in the form of laminar wow flow