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Publication numberUS3143584 A
Publication typeGrant
Publication dateAug 4, 1964
Filing dateMar 15, 1962
Priority dateMay 12, 1959
Publication numberUS 3143584 A, US 3143584A, US-A-3143584, US3143584 A, US3143584A
InventorsRoberts John Francis Lloyd, Walker Eric, Scott Gerald
Original AssigneeIci Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Spinning polypropylenes which have been subjected to thermal degradation promoted bythe presence of sulfur compounds
US 3143584 A
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Description  (OCR text may contain errors)

Au8 4, 1964 J. F. l.. ROBERTS Erm. 3,143,584 SPINNING POLYPROPYLENES WHICH HAVE BEEN SUBJECTED TO THERMAL DEGRADATION PROMOTED BY THE PRESENCE OF SULFUR COMPOUNDS Filed March l5, 1962 United States Patent O 3,143,534 SPNNING POLYPROPYLENES WHICH HAVE BEEN SUBEECTED T THERMAL DEGRA- DATEON PRMOTED BY THE PRESENCE OF SULFUR CGMPSUNDS John Francis Lloyd Roberts and Eric Walker, Harrogate, and Gerald Scott, Manchester, England, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Filed Mar. 15, 1962, Ser. No. 180,019 Claims priority, application Great Britain Mar. 28, 1961 4 Claims. (Cl. 264-210) The present invention relates to the spinning of polypropylene, in particular to the melt spinning of crystalline polypropylene having a stereoregular structure.

lt is known from British Patent No. 810,023 to prepare fibres and filaments from crystalline propylene polymers which are linear and essentially unbranched in character and which are substantially composed of macromolecules wherein the asymmetric carbon atoms have, at least for long stretches, the same steric configuration. Crystalline polyolefines of this type are now widely known as isotactic polyolenes.

Filaments spun from isotactic polypropylene may be oriented by drawing, preferably at elevated temperatures, and subsequently possess useful tensile characteristics such as high tenacity. This property, together with the comparatively low density of the polymer, makes these polypropylene filaments particularly useful in the formation of ropes and cordage. It will be appreciated therefore that the definition of spinning and processing conditions which will yield the highest possible tenacity in filaments of isotactic polypropylene is of great importance.

It is known from our copending application (Serial No. 25,247), now abandoned, that filaments of isotactic polypropylene havirny Itenacities up to about l0 grams per denier may be produced if isotactic propylene polymer having an intrinsic viscosity (measured in tetralin at 135 C.) of greater than about 2.5 is subjected to a drastic thermal treatment prior to extrusion in order to reduce the intrinsic viscosity by degradation to a value in the range 0.5 to 1.5. It is further shown in the same specification that for attainment of the highest tenacities the thermal treatment prior to extrusion must be associated with control of the conditions of spinning so as to produce va spun yarn having an intrinsic viscosity greater than 0.5, preferably 1.25 to 150, and a birefringence of less than X10-3, preferably less than 3 l03 and then drawing the spun yarn at an elevated temperature to a draw ratio of at least 2 to l, preferably at least 4.5 to l. It is further stated that substances may be added to assist the process of degradation during the drastic thermal treatment. We have now discovered that certain compounds of sulphur greatly assist the degradative process allowing less drastic thermal conditions to be employed for the same effect.

According to the present invention we provide a process for the production of fibres or filaments of polypropylene having greatly improved tenacity from isotactic propylene polymer having an intrinsic viscosity greater than 2 by melt spinning yielding filaments having an intrinsic viscosity greater than 0.5 and a birefringence of less than 10X103 which filaments are then drawn at a ratio of at least 2 to 1 wherein prior to melt spinning the polypropylene is subjected to thermal degradation in the presence of a sulphur compound which gives rise to thiyl radicals.

Intrinsic viscosity which is proportioned to number average molecular weight as defined on page 309 of the 1953 edition of Principles of Polymer Chemistry,

ice

by P. Flory, is conveniently measured in tetralin at C.

Birefringence, which indicates the degree of orientation of the spun filaments, may be measured by means of a polarising microscope fitted with a suitable compensator.

It is an inherent feature of our invention that both the intrinsic viscosity and birefringence of the spun yarn are carefully controlled within specified ranges. By limiting the birefringence of the spun filaments to the specified extent higher draw ratios may be applied subsequently and the combination of low birefringence and high draw ratio yields yarns having higher tenacity. The spun yarn birefringence can be controlled effectively through the spinning temperature and in particular the wind-up speed which are in general varied within the limits 24U-320 C. and 50G-4,000 feet per minute respectively. By starting with polypropylene of higher intrinsic viscosity and degrading it by the thermal treatment preferably in the presence of appropriate sulphur compounds before or during spinning to a lower intrinsic viscosity a further advantage in tenacity of the yarns obtained after drawing may be attained.

The thiyl radical, R--S--, where R is an organic residue, is formed on heating a wide range of sulphur compounds. For instance, the following substances give rise to the radical, generally by oxidation or dissociation:

Thiols (particularly those of an aromatic character) such as thiophenols, e.g. thio -naphthol, pentachlorothiophenol and dodecylmercaptan; compounds which can give rise to thiols by tautomeric change such as thioureas, including mercaptobenzimidazole; thioacids such as dinonyldithiophosphoric acid and their salts; disulphides and polysulphides such as niercaptobenzthazole disulphide, di-isopropyldithiophosphoryl disulphide, diphenyl disulphide, di-o-benzamidodiphenyl-disulphide, diaroyldisulphides, diaroylpolysulphides and amine polysulphides, e.g. 4:4 dthiomorpholine.

Other suitable substances include compounds containing Weak bonds between sulphur and another atom, such as dialkyl monosulphides, diaryl monosulphides, diaralkyl monosulphides, diacyl monosulphides, thiophosphoryl monosulphides, dithiocarbamoyl monosulphides, benzthiazole sulphenamides, dithiophosphoryl sulphenamides, tetramethylthiurammonosulphide and alkylthioamines.

Many sulphur compounds which are suitable for our purpose can act as stabilizers for polyoleiines under normal conditions and such compounds are particularly valuable in that they assist in bringing about reduction in molecular weight when the polyolelin is heated to very high temperatures either before or during spinning and thereafter protect the filaments against oxidation, degradation by light and heat up to about C. As indicated in our copending application Serial No. 25,247, now abandoned, temperatures considerably above the polymer melting point are applied to bring about the desired degradation and for isotactic polypropylene temperatures above about 240 C. are preferred. It has been particularly observed that many substituted diphenyl `rnonosulphides, which otherwise stabilise polypropylene,

assist degradation under our preferred thermal conditions. It is also possible to use the sulphur-containing compounds in association with other, sulphur-free substances which either are themselves stalilizers for polyoleiines or form synergistic stabilizing compositions. For instance the sulphur compounds may be added to the olefin polymer together with sulphur-free ultraviolet light absorbers (eg. carbon black), antioxidants, free-radical inhibitors and metal-ion inhibitors. In our improved process quite small amounts of the sulphur compounds are required and less than 2 percent (by weight of the polyolefin) is generally adequate.

Polypropylene filaments produced in accordance with our invention which is essentially concerned with high tenacity lamentary yarns, lind widespread use in industry, for example in ropes, cordages and nets. The filaments may also be used in known manner as a reinforcement in articles such as conveyor belts, hose pipes and tyres made of other materials, particularly rubber and in the form of monofilaments, as bristles for brushes. Fabrics of polypropylene may be used in accumulatore as separators or as retainers for tubular type plates.

The process of our invention may also be applied in making staple fibres of polypropylene having a high initial modulus. The staple fibres are particularly useful in the form of blends with cotton and may be used either alone or in blends with other fibres in outlets where hard wearing properties are important, for instance in pile fabrics and as coverings for tennis balls. Isotactic polypropylene has a density of about 0.9 and therefore floats in water so that the filaments and libres are of special interest in marine applications, for example in mooring lines and as a filling for life jackets.

The process of our invention, as described herein, relates primarily to spinning of isotactic polypropylene. It will, however, be understood that mixtures of isotactic and atactic polypropylene can be used and that the improvement in tenacity obtained by using a low birefringence/ high draw ratio procedure together with preliminary degradation from a higher to a lower intrinsic viscosity is also possible in filaments of stereoregular polyolefins in general including copolymers of alpha-olefines such as propylene/ethylene copolymers. The technique of using degraded polyalphaolenes and of imparting only a W degree of molecular orientation at extrusion are applicable to films and any other shaped articles in which high tensile strength is important.

For the production of high tenacity yarns by the process of our invention suitable values of spun yarn intrinsic viscosity are in the range from about 1.0 vto about 1.6 Below this range control ofY spun yarn quality becomes difiicult and above this range the high tenacities cannot be attained. For staple fibre production such close control of spun yarn intrinsic viscosity is not so important and satisfactory bres may be produced from spun yarns having an intrinsic viscosity in the range about 0.7-2.6.

The following examples illustrate but in no way limit -the scope of our invention.

Example 1 Isotactic polypropylene having an intrinsic viscosity (in Vdecalin at 135 C.) of 2.9 to which 0 to 1.5 percent by weight of 4,4 thio-bis `(3-methyl--tert-butyl-phenol) had been added was fed into a screw melter from which the molten polymer was supplied to a metering pump and thence through a filter consisting of 10-20 B S. mesh sand to a five-hole spinneret (hole diameter 0.015 inch). The screw melter, metering pump and .filter were enclosed in an electrically heated jacket which Was maintained at the required spinning temperature. In all cases conditions were adjusted so that the molten polymer was subjected to the required spinning temperature for ten minutes.

TheY table which vfollows. shows the effect of the concentration of the sulphur compound and the temperature on process of degradation as measured by intrinsic visfcosity (LV.)

280 C. 290 C. 300 C.

l Example 2 Isotactic polypropylene having an intrinsic viscosity of 3.5 to which one percent by Weight of a sulphur compound had been added was fed into a screw melter and -then spun as described in Example l. In all cases the molten polymer was subjected to the required spinning temperature for ten minutes.

The table which follows the effect of four different sulphur compounds and spinning temperature required to bring the spun yarn intrinsic viscosity (I V.) into the range 1.0 to 1.6. Also shown in this table is the effectiveness of these sulphur compounds as stabilizers at lower temperatures.

Spinning Spun Spun Yarn, Sulphur Compound Tempera- Yarn, LV. LV., alter ture C.) 100 hours at 140 C.

290 2. 6 280 2. 9 Less than 0.1 250 3. 3 290 1. 3 1. 3 280 1. 3 1. 3 250 1. 1 1. 0 Compound D 290 l. 3 1. 3

The sulphur compounds used were: Compound A, 4,4 thiobis 3- methyl--tert-butylphenol); Compound B, 2,2 thio-bis(3tertbutyl5- methylphenol); Compound 2,2l bis(N-phenylbenzamido)-phenyl disulphide; Compound D, 4,4 thio-bis(2-methyl-5-tert-butylphenol).

Example 3 Isotactic polypropylene vhaving an intrinsic viscosity of 3.0 to which 0.1-0.3 by weight of 2,2thio-bis(6methyl- 3,5-tert-butylphenol) had been added was fed into a screw extruder electrically heated in such a way as to provide a temperature gradient along its length. The screw exvtruder supplied molten polymer ofthe desired intrinsic viscosity to a metering pump whence it passed through a filter consisting of 10-20 B.S. mesh sand to a 40-hole spinneret (hole diameter 0.015 inch). The metering pump, filter and spinneret were enclosed in a vapour jacket which maintained the required spinning temperature. The temperatures in the spinning equipment were adjusted for each concentration of sulphur compound to give spun yarn of substantially constant intrinsic viscosity and the birefringence ofthe spun yarn was also kept substantially constant by controlling the wind-up speed. In both cases the throughput was 6.5 to 7.0 lbs. per hour.

Screw Vapour Spun Yarn Properties Percent Sulphur Extruder Jacket Compound Tempera- Temperaatures ature Intrinsic Y Birefrin- C.) C.) Vixcosty gence Example 4 Percent of Spun Maximum LV. of polypropylene used Sulphur Yarn, Tenacityv .Compound LV. (gt/den.)

Adde

The invention is illustrated in the drawing in which FIG. 1 shows isotactic polypropylene being introduced into an extruder 1 in which it is heated to an elevated temperaure for degradation and is extruded in the form of filaments, The filaments are drawn by draw rolls 2, preferably after having passed through other rolls 3.

What we claim is:

1. A process for the production of bers and filaments of polypropylene having greatly improved tenacity which comprises subjecting isotactic polypropylene having an intrinsic viscosity greater than 2 to thermal degradation at a temperature above about 240 C. promoted by the presence of a sulfur compound which gives rise to thiyl radicals, melt spinning the resultant polymer to yield laments having an intrinsic viscosity greater than 0.5 and a birefrngence of less than 10 1()-3 and drawing the lilaments at a ratio of at least 2 to l.

2. A process according to claim 1 wherein the sulfur compound is selected from the group consisting of thiophenols, mercaptans, thioureas, thio acids and salts thereof, disuldes and polysuldes.

3. A process according to claim 1 wherein the birefringence of the spun filaments is not greater than 3X10-3.

4. A process according to claim 1 wherein less than 2% of the sulfur compound by weight of polypropylene is used.

References Cited in the le of this patent UNITED STATES PATENTS 2,727,879 Vincent Dec. 20, 1955 2,953,542 Stark et al Sept. 20, 1960 2,960,538 May et al. Nov. 15, 1960 2,967,845 Hawkins et al Jan. 10, 1961 2,967,847 Hawkins et al Jan. 10, 1961 2,967,848 Hawkins et al Jan. 10, 1961 2,967,849 Hawkins et al. Jan. 10, 1961 2,967,850 Hawkins et a1. Ian. 10, 1961 2,995,539 Barker et al Aug. 8, 1961 3,006,885 Dickson Oct. 31, 1961 3,010,937 Roos et al. Nov. 28, 1961 3,013,003 Maragliano et al Dec. 12, 1961

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2727879 *Dec 11, 1951Dec 20, 1955Du PontStabilized ethylene polymer compositions
US2953542 *Dec 11, 1956Sep 20, 1960Hoechst AgStabilized polymer compositions
US2960538 *Mar 30, 1959Nov 15, 1960American Oil CoNew alkyl dithiol and alkenyl thiol
US2967845 *Nov 29, 1956Jan 10, 1961Bell Telephone Labor IncAlpha olefin hydrocarbons stabilized with carbon black and a carbocyclic thioether
US2967847 *Nov 29, 1956Jan 10, 1961Bell Telephone Labor IncAlpha olefin hydrocarbons stabilized with carbon black and a compound having r-s-s-rstructure
US2967848 *Nov 29, 1956Jan 10, 1961Bell Telephone Labor IncAlpha-olefin hydrocarbons stabilized with carbon black and a compound having r(sh)x structure
US2967849 *Nov 29, 1956Jan 10, 1961Bell Telephone Labor IncStabilized straight chain hydrocarbons
US2967850 *Nov 29, 1956Jan 10, 1961Bell Telephone Labor IncCompositions of stabilized straight chain hydrocarbons containing carbon black and a compound having r-s-s-r structure
US2995539 *Apr 24, 1958Aug 8, 1961Du PontEthylene polymer composition containing alkanol sulfide polymer
US3006885 *Aug 24, 1959Oct 31, 1961Hercules Powder Co LtdStabilized polyolefin compositions
US3010937 *Dec 15, 1959Nov 28, 1961Bayer AgProcess for stabilizing polymers of monoolefins
US3013003 *Dec 6, 1956Dec 12, 1961Montedison SpaLinear polymers of improved mechanical and processing properties and methods for their production
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3297808 *Jan 24, 1964Jan 10, 1967Basf AgProcess for the continuous production of rods or other sections from thermoplastics
US3374296 *Jan 22, 1964Mar 19, 1968TnoThermoplastic extrusion process
US3485906 *Aug 31, 1967Dec 23, 1969Hercules IncMelt spinning elastic polypropylene monofilaments
US3542724 *Jun 3, 1968Nov 24, 1970Stauffer Chemical CoPolymers stabilized with combinations of a sulfur-containing compound and a phosphite
US3759917 *Apr 8, 1971Sep 18, 1973Du PontUse of an open-barrel screw press dryer for chain-branching an epdm copolymer
US3849241 *Feb 22, 1972Nov 19, 1974Exxon Research Engineering CoNon-woven mats by melt blowing
US3882058 *Sep 14, 1973May 6, 1975Ethylene Plastique SaPhotodegradable polymeric compositions containing a mixture of an iron salt and sulfur or a dialkyl polysulfide
US3904730 *Jan 26, 1970Sep 9, 1975Mitsui Petrochemical IndProcess for the preparation of polypropylene crimped fibers
US3972759 *Jun 11, 1973Aug 3, 1976Exxon Research And Engineering CompanyCompacted thermoplastic fibers
US3978185 *May 8, 1974Aug 31, 1976Exxon Research And Engineering CompanyMelt blowing process
US4451589 *Mar 7, 1983May 29, 1984Kimberly-Clark CorporationDecreasing molecular weight with free radical prodegradants
US5554668 *Aug 31, 1994Sep 10, 1996Montell North America Inc.High melt strength, propylene polymer, process for making it, and use thereof
US6077914 *Feb 19, 1998Jun 20, 2000Fmc CorporationMolecular weight of a polyolefin is reduced by treatment with an inorganic peroxygen selected from metal persulfates, ammonium persulfates, and any mixtures thereof.
US6987149Apr 22, 2002Jan 17, 2006Said BouhelalIsostatic polypropylene crosslinking in the presence of peroxide
US7241844Jul 29, 2005Jul 10, 2007Said BouhelalHigh speed shearing the isotactic polymer with a peroxide, sulfur and a tetramethylthiuram mono- or disulfide accelerator; initiating crosslinking at 140 degrees Celsius using the accelerator to partially inhibit peroxide crosslinking; and simultaneously forming macromolecular chains with sulfur bridges
US7309744Jul 29, 2005Dec 18, 2007Said BouhelalArticle formed from cross-linking isotactic polymers in the presence of peroxide
US8153745Apr 16, 2007Apr 10, 2012Borealis Technology OyMulti-branched polypropylene
CN1043148C *Jun 10, 1989Apr 28, 1999希蒙特股份有限公司Polypropylene composition and application thereof
EP0190889A2 *Jan 30, 1986Aug 13, 1986Montell North America Inc.Polypropylene with free-end long chain branching, process for making it, and use thereof
Classifications
U.S. Classification264/210.6, 525/343, 525/349, 525/350, 525/333.9, 264/211, 525/352, 528/487, 264/290.5
International ClassificationD01F6/04, C08F8/50
Cooperative ClassificationD01F1/10, D01F6/06, C08F8/50
European ClassificationD01F6/04, C08F8/50