RU2002861C1 - Method for preparing plexofilament film-fibrillar polyolefin threads and solution for their immediately formation - Google Patents

Abstract

SUMMARY OF THE INVENTION: A mixture of 18 to 32% polyolefin (polyethylene or polypropylene), 10 to 17.5% carbon dioxide and 58 to 67% methylene chloride is heated to 150-210 ° C. The resulting solution is subjected to instant molding from a zone with a pressure higher than autogenous to a zone with lower temperatures and pressure. 2 sec and 4zp. f-py, 4 tab.

Description

FIELD OF THE INVENTION This invention relates to the instantaneous formation of polymer film-fibrillar bundles (strands) by flash evaporation. More specifically, the invention relates to an improvement in such a method that allows the formation of beams (strands) from liquids by rapid evaporation which, when released into the atmosphere, do not adversely affect the ozone layer of the earth.

There is a known flash vaporization method for producing plexonized (tangled fiber) film fibril strands from fiber-forming polymers. A solution of the polymer in a liquid that is non-solvent for the polymer at or below its normal boiling point is extruded at a temperature above the normal boiling point of the liquid and under autogenous or elevated pressure in a medium with a reduced temperature and substantially reduced pressure. This rapid evaporation molding causes the liquid to evaporate and thereby cool the extrudate, which forms a plexonized fibril film strand from a polymer, preferred polymers include crystalline polycarbon hydrocarbons such as polyethylene and polypropylene.

According to this method, a suitable flash evaporation molding liquid (a) has a boiling point that is at least 25 ° C below the polymer melting point: (c) practically does not react with the polymer at the extrusion temperature; (c) should be a solvent for the polymer at temperature and pressure, respectively, in the range from 140 to 200 ° C, 38.15 atm to 104.3 atm; (d) should dissolve less than 1% of the polymer at a temperature below its normal boiling point; and should form a solution that will experience rapid phase separation upon extrusion to form a polymer phase that contains insufficient solvent to plasticize the polymer. Depending on the particular polymer used, the following liquids are useful in a flash evaporation process; aromatic hydrocarbons such as toluene and cyclohexane, hexane, pentane, 3-methyl-pentane. chlorobenzene or methylene chloride and others.

The flash evaporation molding solution may further comprise dissolved gas such as nitrogen.

carbon dioxide, helium, hydrogen, methane, propane, butane, ethylene, propylene, and so on. Preferred for improving plexonated fiber formation

are less soluble gases, i.e. gases that dissolve in less than 7% of the concentration in the polymer solution under molding conditions. Additives can usually be added to the solution before extrusion, such as antioxidants, UV stabilizers, dyes, pigments. However, the use of these solvents does not provide yarns of the desired quality,

5 The invention provides an improvement in the known method for producing plexonated film-fibril strands from fiber-forming polyolefins from a halocarbon molding liquid, which contains 10-20 wt.% Fiber-forming polyolefin. A fiber-forming polyolefin, for example linear polyethylene, is dissolved in a molding fluid that includes

5 halocarbons, with the formation of a molding solution, and then subjected to molding with rapid evaporation at a temperature in the range of 140-200 ° C and a pressure that is greater than the autogenous pressure of the molding fluid, with the flow in a region with significantly reduced temperature and pressure.

The basis of the improvement of the invention is halocarbon, which is selected from the group consisting of:

1,1-dichloro-2,2,2-trifluoroethane (HC-123)

1,2-dichloro-1,2,2-trifluoroethane (HC-123a)

0 1,1-dichloro-2,2-difluoroethane (HC-132a)

1, 1 dichloro-1,1-difluoroethane (HC-132b)

1,1-dichloro-1-fluoroethane (HC-141b).

5 The designation in parentheses is used. here for the abbreviation of the chemical formula of halocarbon. Tab. 1 contains known normal atmospheric boiling points (Tb), critical temperatures (Tb) and critical pressures (Pc) for selected halocarbons and for some solvents of the prototype. In the column labeled solubility in table. 1, data showing whether a 10% solution of polyethylene in halocarbon can be formed at a temperature of 130–225 ° С under autogenous pressure.

The first five suitable halocarbons listed above are a very specific and small group of halocarbons that are suitable for use in the invention.

Moreover, with NS-123 and NS-Sha, such solutions of polyethylene can be formed in a halocarbon liquid only at pressures of more than 210 atm with NS-132 b. such solutions of polyethylene can be formed in halocarbon liquids only at pressures above 126 atm. and with HC-141b, such solutions of polyethylene can be formed in a halocarbon liquid only at pressures above 140 atm. Such polypropylene solutions can be formed in the halocarbon molding fluids of the invention only at pressures greater than 126 atm.

Even among the five halocarbons suitable for use in the proposed process, care must be taken with these halocarbons in order to avoid some of the degrading characteristics that may be present. For example, excessive heating time with HC-123a is avoided. NS-132a. HC-132b and HC-141b in order to minimize decomposition that may occur due to dehydrohalogenation or hydrolysis of halocarbon. Caution should also be taken with HC-132b, as there are some definitions that this substance may be a reproductive toxin in male animals. Due to the relative freedom from these problems of stability and toxicity. HC-1231 is the preferred halocarbon for use in the method of the invention.

In the process of forming a solution of a fiber-forming polyolefin in halocarbon fluids of the invention, a mixture of a fiber-forming polyolefin and halocarbon is heated to a temperature in the range of 140-180 ° C. If the polyolefin is polyethylene, then the mixture is pressurized to more than 140 atm, if the halocarbon is HC-141b, more than 210 atm, if the halocarbon is HC-123, or HC-123a. and more than 126 atm, if the halocarbon is HC-132a or HC-132b. If polypropylene is used, the mixture is pressurized to more than 125 atm, regardless of the selected carbon monoxide.

The mixtures described above are at the required pressure until then. until a fiber-forming polyolefin solution is formed in the liquid. After the fiber-forming polymer has dissolved, the pressure can be reduced to some extent, and then the mixture is formed by flash evaporation to form the desired structure of a high-quality strained & strand.

The concentration of fiber-forming polyolefin in the molding fluid is usually

is in the range of 10-20 wt.%.

The molding solution mainly consists of a halocarbon liquid and a fiber-forming polyolefin. but if it is desirable to prepare low-pressure molding solutions, the molding solution may contain a second liquid or cosolvent for the wave-forming polyolefin. If co-soluble, is hydrocarbon

5 solvent such as cyclohexane. toluene, chlorobenzene, hexac. pentane, 3-methane pentane and the like, the concentration of the co-solvent in the mixture of halocarbon and the co-solvent is usually 5-20

wt.% and preferably less than 15 wt.% to reduce potential ignition problems. However, if methylene chloride is used as a co-solvent, then the concentration of methylene chloride in the mixture

5 halocarbon (cosolvent). that is, free of an aol-forming polymer, typically comprises 5-50% by weight.

Standard molding aids can be added to the moldable mixture.

0 by flash evaporation using known techniques. These additives can function as UV stabilizers, antioxidants. fillers, dyes and the like.

5 The various characteristics and properties indicated in the previous discussion and in the examples given were determined using the following methods. Test methods.

0 The solubility of polyethylene and polypropylene under autogenous conditions was measured using a standard test in a tightly sealed Woodell tube. The quality of the plexonated film-5 lobed strands obtained in the examples was evaluated using a five-point system. A score of 5 indicates that the strand had an improved fiber compared to what is usually achieved in the industrial production of molded sheets of polyethylene strands obtained by such a flash evaporation. A rating of 4 indicates that the product is as good as industrial

5 strands obtained by flash evaporation molding.

A rating of 3 indicates that the strands are not of very good quality compared to industrially molded by rapid evaporation. Score 2 shows that

strand has very poor inadequate fiber. A score of 1 does not indicate strand formation. A rating of 3 is the minimum rating that can be considered satisfactory for use in the method of the invention.

The surface area of a plexonated fiberglass product is another measure of the degree and quality of fiber product obtained by flash evaporation. Surface area is measured by the BET method by nitrogen adsorption.

The tensile strength obtained by forming during rapid evaporation is determined using a tensile testing machine (Instron type instruments). The bundles were conditioned and tested at 21.1 (70 ° C) and 65% relative humidity,

Denier strands (fiber titer) were determined by the mass of strands with a length of 15 cm. Then the sample was twisted at a frequency of 10 revolutions per inch (4 revolutions per cm) and mounted in the grips of the Instron device. A 1 inch (2.54 cm) gauge length and an elongation rate of 60% per minute were used. Tear strength was recorded in grams (denier).

The invention is illustrated by examples that are carried out in a batch process in equipment of a relatively small size. Such batch processes can be scaled to large sizes and turned into continuous processes of rapid evaporation.

The term half-olefin. as used herein, means any polymer from a series of highly saturated open-chain polymer hydrocarbons composed solely of carbon and hydrogen. Typically, polyethylene and polypropylene are preferred.

by olefins for use in the method of the present invention.

The term polyethylene encompasses not only ethylene homopolymers, but also copolymers, where at least 85% of the repeating units are ethylene units. A preferred polyethylene is homopolymer linear polyethylene, which has an upper melting point of 130-135 ° C, a density in the range of 0.94-0.98 g / cm3 and a melt index (as defined by ASTM D-1238-S7T. Condition E) from 0.1 to 6.0.

The term polypropylene means not only propylene homopolymers, but also copolymers where at least 85% of the repeating units are propylene units.

The term “plexonized film-fibril strands” as used herein means a strand that is characterized as a three-dimensional integrated network of a plurality of thin, ribbon-like, film-fibrous elements of random length and an average thickness of less than 4 microns, usually uniformly elongated in space along the axis di. The film-fibril elements are entangled and separated at irregular intervals in various places along the length, width and thickness of the strand, with the formation of a three-dimensional grid.

Examples. For each of Examples 1-25 and Comparisons A and B, a linear high density polyethylene with a melt index of 0.76 was formed by flash evaporation into satisfactory fibrous, plexonized strands in accordance with the invention (with the exception of Example 7, which used linear low-density polyethylene density with melt index 26).

Two types of apparatus were used to prepare a mixture of halocarbons and a film-forming polyolefin and to carry out rapid evaporation molding. The apparatus indicated by I was used in Examples 1,5 and 16. The apparatus indicated by II was used for all other examples and for comparisons.

Apparatus I is a high pressure apparatus comprising a 50 cm cylindrical vessel, provided at one end with a cylindrical piston, which is intended to apply pressure to the contents of the vessel. The other end of the vessel is equipped with a die design having a capillary (0.03 inch) 0.076 cm in diameter and 0.15 cm (0.060 inch) long and a quick-acting device for opening and closing the capillary. There were also sensors for measuring pressure and temperature inside the vessel. During operation, a fiber-forming polyolefin and halocarbon were loaded into the vessel. High pressure was applied to the charged mixture (for example, 315 atm (4500 psi). The contents were heated to the desired temperature (for example 140 ° C) for 1 hour to form a solution, which was then stirred ten times with cyclic pressure. the pressure was reduced to the required level for molding and the valve of the spinneret capillary was opened, and then the resulting product formed by flash evaporation was taken

The apparatus I includes two cylindrical pressure vessels, each of which is equipped with a pressure piston. Each of the vessels is similar to a cylindrical vessel of apparatus t, but without a spinneret design in each vessel, and two vessels are connected to each other by a transport line. The transport pin (tube) contains finely porous sieves introduced to mix the contents of the apparatus by forcing the contents through the transport pipe from one cylinder to another.

A die structure having a capillary with a diameter of 0.076 cm (0.03 inches) is connected to the transport lines through a quick-acting device for opening and closing the hole. Devices are also available for measuring temperature and pressure within the vessel. During operation, the apparatus is loaded with a fiber-forming polyolefin and halocarbon and high pressure is applied to the charge. The contents are then heated to the desired temperature for one and a half hours, during which a pressure difference of 3.5 atm (50 psi) is alternately set between the two cylinders to force the contents through the transfer line from one cylinder to another to allow mixing and forming a solution. Then, the pressure required for the foaming is applied and the capillary of the die is opened. Next, the product obtained by molding by rapid evaporation, is selected.

All examples and comparisons were carried out in a similar way and, depending on the equipment used, under specific conditions and with certain ingredients, are presented in the table. 2 and 3. In the table. 2 and 3 also show the characteristics of the strands obtained by forming by flash evaporation.

In the table. 2, examples 1-7 illustrate the use of various hydrocarbons suitable for the method and solutions of the invention. Comparisons A and B show the use of some of the same halocarbons, but under conditions that do not allow a satisfactory strand to be obtained.

In the table. 3 examples 8-25 illustrate the use of various halogenated carbon disinfectants.

In the table. 3, Example 26 shows that good lexonated fibrous products can be obtained from other types of polyolefins using the present invention. The equipment and methodologies used in this example. were the same as in the examples of the table. 3. with the exception that polyethylene was replaced with isotactic polypropylene with a melt flow rate of 0.4, industrially permissible under the trademark Profax 6823 of Hercules Inc., Wi-Mington De.

In addition, higher mixing temperatures were used to compensate for the increased melting temperature of the polymer. Used conditions and properties of the obtained fiber are presented in table. 3, The polymer mixture contained 3.6 wt.% Based on the Iranox 1010 polymer (trademark of Tsiba-Geigy Corp. for high molecular weight hindered polyphenol) as an antioxidant;

(56) U.S. Patent

Me, cl. 57-140, published. 1957.

U.S. Patent No. 3,655,498. 428-251, published. 1970.

S. Brunauer Stolh.-J.Am. Chem. Soc1938, v. 60. p. 309-319.

45

Table 1

table 2

Continuation of table 2

Continuation of table 2

No - means that Neis does not form directly - means that no CeHi2 measurements have been taken - means cyclohexane.

Characteristic

Equipment

Polypropylene

oncentration, wt.%

solvent: NS

Mixing

temperature, ° С

pressure, atm

Molding

temperature, ° С

pressure, atm

Received

denier

strength, g / denier quality

The claims

1. A method for producing plexofilament film-fibrillar polyolefin filaments. By preparing a 10 20% solution of the polymer in a halocarbon solvent at 140 -, instant molding at 140 - 200 C, evaporation upon transition from the high pressure zone to the zone low pressure, characterized in that 1, 1-dichloro-2,2.2-trifluorosethane is used as the gzlohydrocarbon solvent;

Continuation of table 2

Table 3

Index

II

sixteen

123

180 126

180 126

483

1.23

4

1,2-dichloro-1,2,2-trifluoroethane, t. 1-dichloro-2.2-difluoroethane, 1,2-dichloro-1,1-difluoroethane, 1,1-dichloro-1-fluoroethane or a mixture of one of these halocarbons with 5-50 wt.% Methylene chloride or 5-20

wt.% 3-methylpentane, cyclohexane, toluene, pentane. hexane or chlorobenzene, and molding is carried out at a pressure of 126-329 atm.

2. The method according to claim 1. characterized in that

that polyethylene or polypropylene is used as the polyolefin.

19200286120

3. The method according to claim 1. characterized in that 1,2-dichloro-1.2.2-trifluoroethane, 1,1-dichloro-that molding at a pressure above 2102,2-difluoroethane, 1,2-dichloro-1,1-difluoro-atm is carried out from a solution of polyethylene in TaHi 1 , 1-dichloro-1-fluoroethane or a mixture of 1. 1-dichloro-2,2,2-trifluoroethane or 1,2-dich-one of these hydrogen halides with 5 - lor-1.2.2-trifluoroethane. 5 50 wt.% methylene chloride or from 5 to 20

4. The method according to claim 1, characterized in that the mass% of 3-methylpentane, cyclohexane is formed by molding at a pressure of more than 140ol, pentane, hexane or chlorobenzene, atm from a solution of polyethylene-6. A solution according to claim 5, characterized in that in 1.1-dichloro-1-fluoroethane. That it contains as a polyolefin

5. Solution for instant molded polyethylene or polypropylene, nor plexofilament film-fibrillar polyolefin filaments, Priority on the grounds of:

containing 10-20 wt.% polyolefin and 18.07.89 according to available examples

80 - 90 wt.% Halogen-hydrocarbon expansion of the temperature range of the mixer, characterized in that, for the purpose of neither COMPONENTS of the mixture, it is possible to diaparameterize the molding process, in the quality zone o-.

Halogenated hydrocarbon solvent i 08.30.88 - covers the signs concerning it contains 1,1-dichloro-2,2,2-trifluoroethane, with only polyethylene.

twenty