Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1995-01-17
2004-01-13
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S395000, C428S364000, C442S059000
Reexamination Certificate
active
06677039
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to polyolefins containing one or more organic phosphites or phosphonites, or mixtures thereof, or HALS (Hindered Amine Light Stabilizer), or mixtures of the phosphites or phosphonites and HALS and optionally small quantities of one or more phenolic antioxidants, and thermoweldable fibers of the above mentioned stabilized resins that can be obtained through extrusion.
Within the definition of fibers as used herein are included also the manufactured products similar to fibers, such as fibrils, monofilaments, and raffia.
Polyolefin fibers are used widely in manufacturing thermally welded products, in particular of nonwoven textiles, through various technologies, the most important of which, like calendering and spun bonding, require that the fibers have the capability of thermowelding at temperatures lower than the melting point of the polyolefins from which they are made.
Moreover said fibers and manufactured articles obtained from them must be resistant to aging, yellowing, and to the color variations induced by gas fading and oxidizing phenomena in general.
Fibers obtained from polyolefins containing the most commonly used stabilizers, such as phenolic stabilizers, have little welding capability when they are submitted to a thermomechanical treatment carried out at a temperature lower than the melting point of the polyolefins.
Therefore, the mechanical properties of a nonwoven textile obtained by calendering the above mentioned fibers are poor.
In order to increase substantially the strength of thermowelding among the fibers, it has been suggested that bicomponent olefin fibers, i.e., constituted by two different polyolefins, such as polypropylene and polyethylene, are used, and the one with the lowest melting temperature is the one covering the surface of the fiber.
The results obtained this way are usually poor because of incompatibility between polyolefins of different chemical natures.
Italian patent application n. 22783 A/82 shows that the thermoweldability of polyolefins fibers can be improved by adding to the polyolefins of a 3,3′,4,4′-benzophenone tetracarboxylic acid di-anhydride or one of its alkyl derivative. However, fibers obtained this way have a reduced resistance to yellowing and aging.
SUMMARY OF THE INVENTION
Unexpectedly, Applicants have found that polyolefin fibers with high thermoweldability, resistant to aging, yellowing, and color variations due to “gas fading” and oxidizing processes, can be obtained by starting with crystalline olefin polymers containing one or more of the following stabilizers:
a) from 0.01 to 0.5%, preferably from 0.05 to 0.15%, by weight of one or more organic phosphites or phosphonites or mixtures thereof; or
b) from 0.005 to 0.5%, preferably from 0.01 to 0.025%, by weight of one or more HALS; or
c) mixtures of (a) and (b);
and optionally one or more phenolic anti-oxidants at a concentration not exceeding 0.02% by weight.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Said olefin polymers can be in granular or nonextruded particle form, having geometrically regular form, such as flakes or spheroidal particles.
The stabilizers are incorporated during the extrusion and granulation phase of the particles, or the nonextruded particles are coated or impregnated with the stabilizers at least on the surface, preferably after the polymerization stage.
The coating or impregnation of the nonextruded particles, particularly the spheroidal particles having diameters preferably between 0.5 and 4.5 mm, can be done in a variety of ways, such as, for example, the treatment with solution or suspension of the stabilizers and an optional subsequent evaporation of the solvent or suspension medium.
Alternately, in the processes for extrusion spinning described below, the particles of polymer mixed with the above-mentioned stabilizers can be introduced directly into the extruder.
In general the additivated polyolefins used to prepare the fibers according to the present invention have a melt flow index, determined according to ASTM D 1238-L, between 0.5 and 100 g/10 minutes, more preferably between 1.5 and 35 g/10 minutes, obtained directly in polymerization or through controlled free-radical degradation or visbreaking.
In order to obtain the controlled free-radical degradation, organic peroxides are added during the granulation phase or directly in the extrusion of the fibers.
The organic phosphites that can be used as additives for polyolefins according to the present invention are preferably selected from compounds with the following general formulas:
where R
1
, R
2
, R
3
, same or different, are alkyl, aryl, or arylalkyl radicals having 1-18 carbon atoms:
where R
1
and R
2
have the same meaning as above;
Q is a tetravalent alkyl radical;
where R
1
, R
2
, R
3
, R
4
, same or different, have the same meaning as indicated above for radicals R
1
, R
2
and R
3
, X is a bivalent alkyl, aryl, or arylalkyl radical.
Examples or organic phosphites included in the general formula I are described in U.S. Pat. Nos. 4,187,212 and 4,290,941, which are incorporated herein by reference.
Specific examples of compounds included in general formulas I, II, III are: tris(2,4-di-ter-butylphenyl)phosphite sold by CIBA GEIGY under the Irgafos 168 trademark; distearyl pentaerythritol diphosphite sold by BORG-WARNER CHEMICAL under the Weston 618 trademark; 4,4′-butylidene-bis(3-methyl-6-ter-butylphenyl-di-tridecyl)phosphite sold by ADEKA ARGUS CHEMICAL under the Mark P trademark; tris(monononylphenyl)phosphite; bis(2,4-di-ter-butyl)pentaerythritol diphosphite, sold by BORG-WARNER CHEMICAL under the Ultranox 626 trademark.
The organic phosphonites that can be used as additives according to the present invention are preferably selected from the compounds of general formula:
where R
1
, R
2
, R
3
, same or different, are alkyl, aryl, or arylalkyl radicals having 1-18 carbon atoms, or R
3
is the radical having the formula:
where R
4
and R
5
, same or different, have the same meaning as indicated for the R
1
and R
2
radicals, and X is a bivalent alkyl, aryl, or arylalkyl radical.
Examples of organic phosphonites included in general formula IV, which can conveniently be used according to the present invention, are described in GB patent No. 1,372,528. which is incorporated herein for reference.
A preferred example of compounds comprised in general formula IV is the stabilizer compositions, the main compound of which is tetrakis(2,4-di-ter-butylphenyl)4,4′-diphenylene diphosphonate sold by Sandoz under the Sandostab P-EPQ trademark.
The organic phosphites and phosphonites are generally used to inhibit degradation and oxidation of polyolefins in the molten state (process stabilizers), and therefore, according to known state of the art, require the addition of high quantities of phenolic stabilizers to obtain a complete stabilization.
The HALS, which according to the present invention are also used as polyolefin stabilizers, are amine compounds with steric hindrance of the amine function, which are generally used as stabilizers for polyolefins in the solid state against oxidation induced by light.
In this case as well, according to known state of the art, the addition of a high quantity of phenolic stabilizers is necessary for a satisfactory stabilization of polyolefin manufactured articles.
The HALS used according to the present invention are monomeric or oligomeric compounds containing, in the molecule, one or more substituted piperidyl groups having the following general formula:
where the R
1
radicals, same or different, are C
1
-C
4
alkyl radicals, or tetramethylpiperidine radicals, or the alkyl radicals form, together with the piperidyl carbon atom to which they are bonded a C
5
-C
9
cycloalkyl radical; R
2
radicals, same or different, are hydrogen, C
1
-C
18
alkyl radicals, C
7
-C
18
arylalkyl radicals, or the alkyl radical form, together with the piperidyl carbon atoms to which they are bonded a C
5
-C
10
cycloalkyl radical; R
3
radicals, same or different, are hydrogen,
Branchesi Millo
Clementini Luciano
Spagnoli Leonardo
Gray J. M.
Kelly Cynthia H.
Montell North America Inc.
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