CA1235249A

CA1235249A - Aluminum silicate filled abrasion-resistant polyamide monofilament

Info

Publication number: CA1235249A
Application number: CA000407400A
Authority: CA
Inventors: William B. Bond; Ronald L. Saxton; Walter G. Gall
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1981-07-17
Filing date: 1982-07-15
Publication date: 1988-04-12
Also published as: EP0070709A3; NO157667B; EP0070709A2; NO157667C; JPS5818415A; EP0070709B1; NO822472L; DE3273567D1

Abstract

TITLE
ALUMINUM SILICATE FILLED
ABRASION-RESISTANT POLYAMIDE MONOFILAMENT
ABSTRACT OF THE DISCLSOURE
Polyamide monofilament with excellent transverse abrasion resistance obtained by incorporation of aluminum silicate, particularly useful in paper clothing.

Description

i2352~9 TITLE
ALUMINUM SILICATE FILLED
ABRASION-RESISTANT ~OLYAMIDE MONOFILAMENT
BACKGROUND OF THE INVENTION
In the preparation of paper, woven support belts are used for the initial casting and subsequent treatment of the paper. These belts are known as paper clothing. A variety of materials has been used in the manufacture of such belts, including metals, and, more recently, thermoplastic monofilaments.
Thermoplastic materials which have been used in the weaving of these belts include nylon as well as polyester monofilaments.
A particularly satisfactory combination of materials for paper clothing is a polyester monofilament, woven in the machine direction of the belt, with transverse monofilaments composed either partly or entirely of a polyamide monofilament.
Particularly in such applications, a need exists for a polyamide monofilament haviny improved resistance to abrasion when the abrasive force is applied transversely to the longitudinal dimension of the monofilament.
SUMMARY OF THE INVENTION
The present invention provides a polyamide monofilament which exhibits outstanding resistance to abrasive forces applied transversely to the longitudinal dimension of the monofilament.
Specifically, the instant invention provides an oriented polyamdie monofilament comprising fiber or filament-forming polyamide and about from 2 to 20 weight percent, based on the total weight of the monofilament, of aluminum silicate having an average particle size of about from 1 to 8 microns.
The instant invention further provides, a woven, heat set, papermaking belt of machine and ~r~

1~35~ ~

transverse direction thermoplastic filaments, the improvement wherein at least about 25% of the transverse direction filaments are monofilaments comprising filament forming polyamide and about from 5 2-20 weight percent, based on ~he total weight of the filament, of aluminum silic:ate having an average particle size of about from 1 ~o 8 microns.
DETAILED D SC~IPTION OF THE I VENT}ON
The polyamides used for preparation of ~he 10 oriented monofilaments of the present invention are non-cyclic polyamides of fiber-forming molecular weight having relative viscosity generally between 25 and 150 as determined by ASTM D 789-62T. These polyamides include, for example~ polycaprolactam (6 nylon), polyhexamethylene adipamide (6~ nylon), polyhexamethylene decanoamide (610 nylon), and polyhexamethylene dodecanoamide (612 nylon).
Polyamide copolymers and polymer blends can also be used, such as those prepared from 6 nylon and 66 nylon. Of these, polyhexamethylene adipamide ~66.
nylon) and polyhexamethylene dodecanoamide (612 nylon) have been found to be par~icularly sa~isfactory for use in paper clothing.
In accordance with the present invention, about from 2 to 20 weight percent, and preferably about from 4 to 10 weight percent, of aluminum silicate is blended with the polyamide used for the preparation of the monofilaments. Less than about 2 weight percent of the aluminum silicate does not provide the markedly improved transverse direction abrasion resistance of the present invention, while quantities of aluminum silicate in excess of 20 weight percent of the monofilament unnecessarily weaken the filament with no further beneficial - 35 effects.

52'~

The aluminum silicate used in the present invention should be of the type generally commercially available in a uniform particulate configuration. The aluminum silicate should have a particle size such that 90% by weight or more of the particles are less than 15 microns and the average particle size is about from 1 to 8 microns. Particularly satisfactory aluminum silicate clays are those in which 98% of the particles are less than 10 microns and have an average particle size of about from 1 to 6 microns. Aluminum silicates of this type are described in detail in United States Patent 3,419,517, and are commercially available as Satintone* from Engelhard Minerals and Chemicals Corp.
of Edison, New Jersey.
The products of the present invention are preferably prepared by combining the nylon polymer with a coupling agent prior to the incorporation of the aluminum silicate. The incorporation of the coupling agent provides improved adhesion of the aluminum silicate to the nylon. Coupling agents which can be used include those organosilane and phos-phorus coupling agents described in Miller U.S.
Patents 3,344,107, 3,471,435 and 3,488,319.
In a preferred embodiment of the present invention, the monofilaments further comprise about from 1 to 10 weight percent of an ethylene copolymer having a Melt Index of about from 0.3 to 30. At least about 50% of the ethylene copolymer should be a graft copolymer prepared from (a) a backbone of polymer selected from the group consisting of thermoplastic polymers of ethylene and copolymers derived from ethylene and C3-C8 alpha-olefins and (b) a graft monomer selected from the group *denotes trade mark ., , ~35'~

consisting of unsaturated carboxylic acids, anhydrides and dianhydrides. Less than 1.0 weight percent of this ethylene copolymer addi~ive provides little or no appreciable improvement in abrasion resistance for the finished monofilament, while quantities in excess of 10 weight percent result in a drop in tensile strength for the monofilament.
Particularly outstanding improvement in monofilament characteristics is realized through the use of about from 1.2 to 5 weight percen~ of the graf~ copolymer.
The graft copolymer, when used, should have a ~elt Index of about from 0.3 to 30. E~hylene polymers having a Melt Index outside of thi~ range can result in processing difficulties. Particularly 15 satisfactory are those graft copolymers having a Melt ~ndex of about from O.S to 20.
Melt Index is measured according to ASTM
D-1238-79, condition E. In that test, the rate of extrusion in grams per 10 minutes (throuyh an orifice 0.0825 inch ~0.210 cm] in diame~er and 0.315 inch 10.800 cml in length~ is determined for the material under test at 190C and under the force of a piston having a diameter of 0.373 inch (0.947 cm) and a total weight of 2,160 grams.
Polymeric materials which can be used as a backbone polymer in ~he gràft copolymers are generally selected from thermoplastic polymers of ethylene and copolymers derived from ethylene and C3-C8 alpha-olefins. Backbone polymers which are 30 substantially saturated include polymers of ethylene and copolymers derived from ethylene and alpha-olefins. Backbone polymers which exhibit unsaturation include ~hose having a substantially saturated backbone chain with unsaturated side 35 chains, including copolymers derived from ethylene 1 ~ 3 ~ 9 and alpha olefins~ The term alpha~olefin includes monoolefins and diolefins and does not include ethylene.
Graft monomers which can be used for the preparation of the graft ~opolymer additives of the present invention include unsaturated carboxylic acids, anhydrides and dianhydrides thermally s~able at ~he tempera~ure o~ ~he grafting reac~ion. Graft monomers which can be used for the preparation of these addi~ives include methacrylic acid; acrylic acid; glycidyl methacrylate; 2-hydroxy ethylacrylate;

2-hydroxy ethyl methacrylate; diethyl maleate, monoethyl malea~; di-n-butyl maleate; maleic anhydride; maleic acid; fumari~ acid; itaconic acid;
15 dodecenyl succinic anhydride; 5-norbornene-2,3-anhydride; and nadic anhydride ~3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride)~
The graft copolymers can be prepared by a variety of reaction techniques. However, 20 particularly preferred is that process described in Flexman, Jr. et al. U.S. Paten~ 4,026,967, wherein the reaction of the components is conduc~ed in baffled tubular reactors which exhibit dispersed plug flow character and which provide rapid heating and 25 coolinq of re~c~ants, short reaction ~ime with uniform material residence time, and radial uniformity of temperature. In general, the graft comonomers can comprise about from 0~15 to 2.0 weight percent of the graft copolymer. A graft copolymer 30 found to be particularly satisfactory in the invention is that prepared from polyethylene having a density of about from 0.94 to 0.97 g/cc and grafted with about from 0.15 t:o 0.75 weight percent graft monomer, and especially fumaric acid or maleic 35 anhydride monomers.

1~352'~

The blending of ~he components of the monofilament can be carried out in any sequence convenient to the particular manufac~uring operation involved. However, in general, it has been found S convPnient to prepare concentrates of each additive in nylon prior to final blending ~o aid in the accurate measurement of each of ~he components.
After blending of ~he componen~s, the ~onofilaments are prepared according to customary techniques. The molten nylon, blended with the aluminum silicat and any other additives, is extruded through a die into a quench medium, after which it is orien~ed~ The monofilaments should be oriented about from 3.4 to 6.0 times their original lS length, and preferably about from 3.5 to 4.7 times the~r original length. In general~ the diameter of ~he final monofilament should be abou~ from 5 ~o 30 mils, and preferably about from 10 ~o 20 mils.
The monofilaments of the present invention can be woven into papermaking belts according ~o conventional weaving techniques. The type and density of the weave will, of course, depend on the type of paper and papermaking operation for which the belt is to be used. The present monofilaments are 25 particularly satisfactory when used in combination wi~h polyester monofilaments in a woven belt in which the polyester monofilaments make up the machine direction strands and the monofilaments of the present invention comprise at least about 25%, and 30 preferably about from 25% to 50% of the transverse direction ~trands.
After weaving, the papermaking belts are heat set according to conventional techniques to stabilize ~he weave. Typical heat setting conditions will vary with the polymer, filaments, di~meter and .~35;~9 weave, but will typically involve heating under tension in a hot air oven for about from 15 minutes ~o 1 hour at a temperature o~ abou~ from 300 to 400F.
The improved monofilamen~s o~ ~he present invention, when used as transverse direction strands in papermaking bel~s, exhibi~ excellent resistance to the transverse direction abrasion enoountered in belts of this type. This abrasion resistance permits ~mproved operation for apparatus using such belts, in that the period between belt replacements is increased significantly.
Tbe present invention is further illustrated in the following examples, in which par~s and percentages are by weight unless otherwise indica~ed.
EXAMPLES 1-9 AND_COMPARATIVE EXAMPLES A-D
A concentrate of aluminum ~ilicate and nylon 612 was prepared by tumbling 12 pounds of nylon 612 for 30 minutes with 50 grams of gamma-aminopropyl triethoxy silane coupling agent.
Eight pouncls of aluminum silicate of 1.3 microns particle size was added and tumbled for an additional 30 minutes. The blend was then extruded in a 53 mm twin-screw extruder at 150 pph, with a screw speed of 200 rpm and a barrel temperature of from 250 to 26~C
under full vacuum at the vent port~ The resulting strands were water quenched and cut into flake.
Next, concentrates were prepared of nylon 612 with three ethylene copolymers, designated Addit$ves A, B and C. Additive A was a graft 30 copolymer having a Melt Index of 11.4 and an average anhydride graft level of 0.4%. Additive B was also a graft copolymer having a Melt Index of 0.59 and an average anhydride graft level of 1.75%. Additive C
was an ungrafted ethylene-~-olefin copolymer having a 35 melt flow of 1.0 g in 10 minutes at 280C with a 5000 g load and the same orifice dimensions used in the Melt Index method.
Nylon 612 having an inher*nt viscosity of 1.10 to 1. 25 in metacresol was f irst dried overnight 5 in a vacuum oven at 120C. The additives were dried at 60 t: under vacuum overnight ., Concentrates were prepared by first cooling the nylon 612 to 60C and then tumbling ~he nylon with additives for 30 minutes end over end. TWQ concentrates were prepared. The f irst concentrate contained 90 pounds of nylon 612 and 10 E)ounds of Additive A. The second concentrate contained 81 pounds of nylon 612, 10 po~nds of Additive B and 9 pounds of Additive C. Each blend was extruded in a 53 mm twin-screw extruder at 27 pph, with a screw speed of 100 rpm, and a barrel temperature o~ from 215 to 250C. The resul~ing strands were water quenched and cut to flake.
Nylon concentrates o~ the additives prepared above were blended with additional nylon 612 in ~he ratios indicated in Table I and then dried overnight at 120C in a vacuum oven. They were extruded as monofilamen~ through a 1 1/2-inch single-screw e~truder wi~h a scre~ speed adjusted to maintain constant pressure to a two-capacity Zenith gear pump. The polymer was filtered through five 50-mesh screens and extruded through a .OS9" single-hole die, quenched in water after passage through 8 inches of air. The extruder barrel temperature ranged from 240 to 280C. The filament was immediately drawn 4X
while passing through a steam tube, conditioned for 4 seconds at 180C, allowed to relax 6% as it came out of the conditioner and then wound on 2 spool at 860 feet/minute. The tensile properties of the blends were tested, and the results are summarized in Tab~e I.

~S2~

The filament of Comparative Example B
contains 2 weight percent of Additive A, but no aluminum silicate~ Compara~ive Examples C and D are filamen~s of commercially available nylon 612 and polyethylene terephthalate, withou~ the additives of the present invention.
The fitaments were tested by ~ending four samples of each filament to be tested over a .016"
steel wire and loading ~o a tension of ~0 grams. The samples are forced against a stainless steel roller turning at 30-35 rpm at a load of 100 grams/sample.
The four samples are kept wet with a 10% slurry of Kaolin in water throughout the test, which lasts 6 hours. Break load and elongation of the four samples 15 are then measured in an Instron tes~er and the means divided by the u~abraded value to obtain percent retention for break load and elongation. The average of these two values is tabulated below:
Av. % Retention of ExamPleBreak Load & Elongation

3 68 ~ 60 g 70, 63 A 42, 40 If the test procedure i8 repeated, except 30 that the 10% ~aolin is omltted from the water used to wet the samples, the samples will retain at least about 90% of their break load and elongation.
EXAMPLES 10 TO 19 AND COMPARATrVE EXAMPLES E TO H
The general procedure of Examples 1 to 9 was 35 repeated, except tha~ blends were prepared from three i~35'~9 commerciallv available nylon 66 compositions. Nylon A is substantially unmodified nylon 66. Nylon B is a copolymer of nylon 6 and nylon 66 blended with about 36~ aluminum silicate. Nylon C is nylon 66 blended with 10~ of gra~ted ethylene alpha-olefin copolymer and 9%
of ungrafted copolymer of the types used as Additives B and C respectively in Examples 5 and 6 above.
~ylons A, B and C were tumbled and dried in the ratios indicated in ~able II. The resulting blends were then extruded as in Examples 1 to 9, except that the melt was filtered through a finer set of screens, the die was 0.95 inches in diameter, and the extruder temperature ranged from 235 to 305~C. The resulting filaments were drawn 2.5 or 3.0 times and conditioned at 220C. The physical properties of the resulting filaments were evaluated and the results are summarized in Table II.
Comparative Examples E and F were unmodified nylon 66, containing no aluminum silicate. Comparative Example G was unmodified polyethylene terephthalate monofilament. Comparative Example H was a commercially available nylon 66 monofilament containing about 2% of additive A used in Examples 3 and 4 above.
The resulting monofilaments were tested for transverse abrasion as in Examples 1 to 9 above, except that the roller was tool steel rather than stainless steel. Water without Kaolin was used to wet filaments, and the filaments were tested for 3 hours instead of 6 hours. The abrasive used was iron oxide, which accumulated on the roller surface as the test proceeded. It was removed with emery cloth before each new sample was installed. The average retention of break load and elonqation after three hours of abrasion is summarized in the followins 3- table:

~s;~

Av. % Retention of Poly- %
Exam~le Break Load & Elonqation R~ olef in Mineral _ ~33 72 ~5 36 11 30 2.6 20 12 12 90 2.4 10 13 22 72 5.5 20 14 6B 79 5.5 10 81 g5 1.2 18 16 91 112 1.3 10 17 5~ 122 ~.74 11 18 65 ~ 14~ 0.37 5.8 19 62 159 ~,12 1O8 ~ 61 66 65 2.0 --Monofilaments were prepared by direct blending of the components. A blend was prepared by tumblin~ ~2 pounds of nylon 612 fo. 30 minutes with 51 grams of gamma-aminopropyl triethoxy silane coupling agent. Seven and one-half pounds of aluminum silicate of 1.3 microns particle size was added and t~bled for an additional 30 minutes. The blend was then extruded without drying in an 33 mm twin-screw extruder at 141 pounds/hour with a screw speed of 130 rpm and a barrel temperature of 255 to 265C under 6 inches vacuum at the vent port. The molten polymer was fed to eight two-stream, five capacity ~enith gear pumps, filtered througn a stack of 33 screens, extruded through a .060" single-hole die, and quenched in water after passage through a

4-1/2" air gap. The filament was immediately drawn 3.5X in a radiant heater at 840~C, passed through a hot-air conditioning oven at 200C for 1.4 seconds, 24~

and removed from the oven at 40-50 grams tension to cooling rolls after which it was wound on spools at 2070 feet per minute. The monofilament had a caliper of 14.0 mils.
On testing according to the procedures of Examples 1-9, the filament exhibited a Break Load of 14 pounds, an Elongation to Break of 34~, an Initial Modulus of 420 Mpsi, and a Tensile Strength of 52 Mpsi. The Shrinkage was 6~ and the Inherent Viscosity 1.10. The average retention of Break Load and Elongation was 55~.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An oriented polyamide monofilament for use in fabricating woven papermaking belts, having a diameter of about 5-30 mils and comprising (i) fiber or filament-forming polyamide, (ii) about 2 20 weight percent, based on the total weight of the monofilament, of aluminum silicate having an average particle size of about 1-8 microns, and (iii) about 0.5 to 10 weight percent of an ethylene copolymer having a Melt Index of about 0.3 to 30, and having excellent resistance to transverse direction abrasion when used as a transverse direction filament in papermaking belts, at least about 50% of the ethylene copolymer being graft copolymer.

2. A monofilament of Claim 1 wherein the ethylene copolymer comprises at least about 50% of a graft copolymer prepared from (a) a backbone of polymers selected from the group consisting of thermoplastic polymers of ethylene and copolymers derived from ethylene and C3 to C8 alpha-olefins and (b) a graft monomer selected from the group consisting of unsaturated carboxylic acids, anhydrides and dihydrides.

3. A monofilament of Claim 1 having a diameter of about from 10 to 20 mils.

4. A monofilament of Claim 1 wherein the polyamide consists essentially of nylon 66.

5. A monofilament of Claim 1 wherein the polyamide consists essentially of nylon 612.

6. A monofilament of Claim 1 wherein the aluminum silicate comprises about from 4 to 10 weight percent.

7. A monofilament of Claim 1 wherein the aluminum silicate has a particle size such that at least about 90% by weight of the particles are less than 15 microns and the average particle size is about from 1 to 8 microns.

8. A monofilament of Claim 7 wherein the alumium silicate has a particle size such that 98% of the particles are less than 10 microns and exhibit an average particle size of about from 1 to 6 microns.

9. In a woven, heat set, papermaking belt of machine and transverse direction thermoplastic filaments, the improvement wherein at least about 25 of the filaments in the traverse direction are oriented polyamide monofilaments having a diameter of about 5-30 mils and comprising (i) filament forming polyamide, (ii) about from 2 to 20 weight percent, based on the total weight of the filament of an aluminum silicate having an average particle size of about from 1 to 8 microns and (iii) about 0.5 to 10 weight percent of an ethylene copolymer having a Melt Index of about 0.3 to 30, at least 50% of the ethylene copolymer being graft copolymer, the filaments in the machine direction and the balance of the filaments in the transverse direction being polyester.

10. A papermaking belt of Claim 9 wherein the polyamide monofilaments comprise about from 25 to 50% of the transverse direction strands.