CA2014092A1

CA2014092A1 - Coated polyamide fiber

Info

Publication number: CA2014092A1
Application number: CA002014092A
Authority: CA
Inventors: Serge Rebouillat; Jurgen Wichelhaus; Johannes Andres; Werner Gruber
Original assignee: Individual
Current assignee: Henkel AG and Co KGaA; EIDP Inc
Priority date: 1989-04-14
Filing date: 1990-04-06
Publication date: 1990-10-14
Also published as: KR900016541A; EP0392477A2; EP0392477B1; EP0392477A3; DE3912521A1; DE59004180D1; ATE100156T1; BR9001724A; JP2979483B2; JPH02293475A

Abstract

COATED POLYAMIDE FIBER

Abstract of the Disclosure The invention relates to a polyamide fiber coated with a specific reaction product from a polyfunctional epoxide component and a polyamide resin. The invention further relates to a process for coating polyamide fibers with such agents.

Description

X03: ~92 COATED POLYAMIDE FIBER
, ., The invention relates to a polyamide fiber coated with a specific reaction product from a polyfunctional epoxide component and a polyamide resin. The invention further relates to a process for coating polyamide fibers with such agents.

Fibers for the purpose of the invention are under-~ stood to be both continuous filaments and staple fibers, :::J fiber tows, yarns, cords, flat textile fabrics or also `~ pulps. Preferred polyamide fibers are aromatic poly-;~ amide fibers.
. ~
Reinforcement of synthetic materials with organic or inorganic fibers is known to produce better material properties. The tensile strength at break of such composite materials or other mechanical properties is increased as a function of the quantity of incorporated fiber. Nevertheless, it has been shown that the full performance capability of the fibers cannot be used in many instances, because fracture occurs in connection with the breaking process at the interface of the fiber with the matrix and the fibers, so to speak, are pulled out of the matrix. Such phenomena are seen particularly with very high tensile strength fibers, for example, aramid fibers.

~ KB-2948 ~, .
,~, 2~

To prevent these, fibers are coated in practice with surface treatment agents, for example, epoxide resin preparations or with other resins. Thus, in the u.s. Patent Specification No. 4,652,448 it has been proposed to coat aromatic polyamide fibers with a reaction product of polyfunctional epoxides and poly-functional amines. Here, the U.S. Patent proposes to start from a specified cord and to coat same with di-functional epoxide such as, for example, the diglycidyl ether of glycerol and a difunctional amine, for example piperazine. It is the goal of said proposal to obtain coating with a relatively low residual epoxide content.
However, such epoxide coatings are rather brittle and, thus, lead to that the treated fibers, yarns etc. can break or splay in subsequent textile processing steps, such as knitting or weaving so that deposits may form in the textile machines.
~,, `';'!'~ Moreover, fibers thus coated exhibit a relatively high water absorption. This property is undesirable for numerous subsequent processing steps.

~jIn the Canadian Patent Specification No. 651,745 there has been described a process for the production of polyaminoamides by condensation of fatty acids with alkylene polyamines. Although such polyaminoamides have been known as curing agents for epoxide resins, no , ,~, reference is found in the technical literature to that they can be successfully used for the surface treatment `~of fibers, and especially aramid fibers.
i~
,Thus, it is the object of the invention to produce ~`!a polyamide fiber, and espec~ally an aramid fiber, which has been provided with a specific epoxide coating based " ,.

- 3 - 2~40~

on polyaminoamides and, thereby, exibits improved - processabilities such as lower coefficients of friction and lower water absorption, but also a good adhesive-ness.
. .
Therefore, the subject matter of the invention is a .,, polyamide fiber coated with the reaction products from a polyfunctional epoxide compound and a polyamine, characterized in that a polyamide resin containing amine groups, and especially terminal amino groups, is employ-ed as the polyamine.

A further subject matter of the invention is a coating imparting bond strength and slip on a polyamide fiber and comprising a product from polyfunctional -, epoxides and polyamide resins, said coating being characterized in that it has been prepared by simultaneously or subsequently applying the polyamide resin and the polyfunctional epoxide compound as a solution, dispersion or melt to the fiber and then, if so desired, curing same at an elevated temperature.

~ Hence, as a general embodiment of the teaching '1 according to the invention it is proposed to use a 3 polyfunctional amine concomitantly containing also amide ~`~ groups as the reactive component for the reaction with the polyfunctional epoxide component. Quite generally suitable for this purpose are polyamide resins having terminal amino groups. However, among these, those polyamide resins are preferred wherein one or all acid component(s) represent branched dicarboxylic acids and, more particularly, dimer fatty acids, or wherein at least one of the difunctional amino components is the corresponding dimer fatty acid diamine.
,, `:
:~. ~' .

Here the term "dimer fatty acid" is understood tomean the dimerization products of unsaturated fatty acids. These are mixtures of substances having a high ~1 content of branched dicarboxylic acids having a chain ;; length of C36 fatty acids, while in addition they also contain monofunctional fatty acids as well as trimers.
!
Among the conceivable polyamide resins having ; terminal amino groups, the reaction products of such ` dimer fatty acids with an excess of at least difunction-: al primary or secondary amines which also may still ; contain tertiary amine groups are suitable. Especially suitable are polyamide resins based on dimer fatty acids as dicarboxylic acid and alkylene diamines, dialkylene triamines and/or the higher homologues thereof as the amino component.
'.'''''' Further suitable are polyaminoamide resins formed upon the reaction of fatty acids and/or dimer fatty acid, preferably unsaturated fatty acids, with ethylene diamine and/or diethylene triamine at elevated tempera-tures and/or in the presence of catalysts and contain-ing, as molecular moieties, nitrogen-containing hetero-cycles (generally imidazoline rings). Among such poly-aminoamides, those products are preferred wherein the number of the nitrogen atoms positioned in rings is from 20 to 90%, and preferably from 20 to 60%, based on the total number of nitrogen atoms.
. .
Further, in the polyamide resins employed according to the invention, a portlon of the dimer fatty acids, i.e. up to about 50% by weight, may have been replaced by dicarboxylic acids comprising 3 to 20 carbon atoms.
Furthermore, it is possible to subject the polyamino-;'`.1 :

~ ~, ` 1 .

~ - 5 -, amides to chain extension by way of a reaction with, e.g., lactams. Suitable lactams are caprolactam and/or lauryllactam.

The polyaminoamides employed according to the invention may be employed also in admixture with other mono- or polyfunctional amines. If so, the amount of the monofunctional amines should be limited to about 10%
by mole, based on amino groups. The amount of the other polyfunctional amines should not be higher than 80% by mole of the total amount of amines. However, it is pre-ferred to use such amines in only minor amounts. Here, suitable amines are di- and trifunctional amines such as those conventionally used as curing agents for epoxides, for example, ethylene diamine, diethylene triamine, aliphatic or cycloaliphatic diprimary amines and the like.
., . ~
The artisan, when selecting suitable polyamide resins, should pay attention to the amine number. It should be more than 20, preferably more than 70, with the upper limit defined by the molecular weight and being about 700, and preferably 100.

A variety of polyfunctional epoxide compounds can be combined with said polyamide resins. The functional-ity of the epoxide component should be from 2 to 4.
Here, poorly volatile polyfunctional epoxide compounds, especially those containing ring structures, e.g.
aromatic ring structures, as the basic moieties, are preferred. Preferred epoxide compounds are N-glycidyl compounds and/or 0-glycidyl compounds, more specifically N-glycidyl compounds having a functionality of 3 to 4.

::~' '``

; - 6 - 2~1~092 .;
A particularly well suitable polyfunctional epoxide compound is tetraglycidyl diaminodiphenylmethane.
,.:
The artisan, when selecting the ratios of amounts, should pay attention to that in the cured state the .:
~ reaction products of the epoxide compound with the poly-,:'"! aminoamide comprise an excess of reactive terminal groups. With polyamide resins having a functionality of at least 2 and an amine value of between 80 and 90 in combination with 4 functional epoxide compounds, it has proven useful to adjust the ratio by weight of epoxide to amine to from 1:5 to 1:1, preferably from 1:3 to 1:1,2 and particularly from 2:3.
~' Quite generally, it is preferred to select the , ratio of amine hydrogen atoms to epoxide rings of ~ between 2:1 and 1:2, while especially an excess is u employed of either the aminic component or the epoxide ~I component. Higher amine amounts may be employed as r~y well, such as, for example, between 2 and 4 amine hydro-;~ gen atoms per epoxide group. Then, on the average, ~j terminal amino groups will be present, while the other way around terminal epoxide groups will be present.
~t A further subject matter of the invention is a process for modifying polyamide fibers with the reaction products from polyfunctional epoxides and polyamide ~; resins, in which process the polyamide resin and the ;~ polyfunctional epoxide compound simultaneously or sub-sequently are applied as a solution, dispersion or melt to the fiber and then, if so desired, curing the pro-ducad coating at an elevated temperature.
~ ~ .
In carrying out said process, it may be preferable to separately dissolve or disperse the epoxide compounds s . 1 ~ .

20~0~

and the polyamide resin, and then to coat the fiber either in a mixture of the obtained solutions/dispers-ions or in sequence in the individual solutions~dispers-ions. The usually applicable concentrations of the coating solutions are between 1 and 20% by weight.
Thus, for example, the polyfunctional epoxide component may be used in solutions having solids contents of from 2 to 10% by weight, and the polyamide resin component may be used in solutions havinq solids contents of from 10 to 20% by weight or in dispersions as well and then applied. Moreover, an application may also be effected from the melt.

The resin solutions employed according to the - invention are not in any case true physical solutions.
~j Portions of the polymers mixed with each other may be present also in the dispersed swollen or unswollen state without disadvantage for the properties. In such case settling is to be prevented during application. The usable solvents include the conventional solvents for polyamides based on dimer fatty acid such as, e.g., mixtures comprising Cl- to C12-alcohols, especially C1-to C4-alcohols, preferably in admixture with hydro-carbons. A particularly favourable solvent system consists of isopropanol and toluene, for example in a ~i ratio by weight of 9:1.
,~
`~ In addition, the coating agents according to the invention may contain further additives. Thus, for ~j example, dyes, anti-ageing agents and the like may be present. Also catalysts for the reaction of amines with epcxide groups may be employed. Rnown catalysts for this purpose are, e.g., tertiary amines.

: `
`":`j - 2014(~9~

.
According to the invention, coated polymer fibers of the most various types can be produced. Thus, more particularly, coated fibers of organic polymers, that is of polymerizates as well as of polycondensates, can be prepared. Especially important coated fibers are fibers from polyamides, polyesters, polyimides and/or poly-ethers, namely based on aromatic and/or aliphatic units.
Coated fibers from aromatic polyamides are especially important.

Within the scope of the invention, special signi-ficance is attributed to coated aromatic polyamide fibers. Among aromatic polyamide fibers, fibers (con-tinuous filaments, short staple fibers, pulps, tows, yarnsor flat textile fabrics) from aromatic polyamides with fiber type structure are generally considered.
Aromatic polyamides are understood to be such polymers that are partially, preponderantly or exclusively com-posed of aromatic rings, which are connected through carbonamide bridges and optionally, in addition, also through other bridging structures. The structures of such aromatic polyamides can be elucidated in part by the following general formula: (-CO-NH Al-NH-CO-A2)n, wherein Al and A2 signify aromatic and/or heterocyclic ~i rings, that can also be substituted. An important class of surface-treated fibers of the invention is derived from wholly aromatic copolyamides.
. . ~. .
,,.j ,~ Examples of such aromatic polyamides are poly-m-~ phenylene isophthalamide with the trademark Nomex(R) (US
`2 3,287,324); poly-p-phenylene terephthalamide with the t trademark Kevlar(R) (DE 22 19 703). Further suitable polyamides are those having structures in which at least ~"~ one of the phenyl radicals bears one or more substi-,~, tuents, f~r exa~ple, lower alkyl groups, alkoxy groups ~ ~ .

3 ~

20~4092 - - 9 _ or halogen atoms. Further aromatic polyamides contain, to some extent at least, repeating units that are derived from 3- or 4-aminobenzoic acid, respectively.
.
Additionally suited for finishing with the surface treatment agent of the invention are such wholly aromatic polyamide fibers that have been stretched in a nitrogen atmosphere at a temperature above 150 C
according to DE 22 19 646.

Further suitable are also aromatic polyamides con-taining diaminodiphenylene groups in which two phenyl radicals each bearing an amino or carboxylic acid group are connected together through a bridging structure, for example, a heteroatom (0, S, S02, NR, N2 or a CR2 group, with R = H or alkyl groups) or a CO group. Finally, also suitable are aromatic polyamides in which the aro-matic rings are partially replaced by heterocycles or the heterocycles participate as substituents or chain members, as well as fibers from US 4,07~,172 marketed under the trademark Technora(R).

The surface treatment agents according to the invention may be employed in various stages of the fiber production. Thus, the surface treatment agents may be applied onto the never dried moist fiber (on line), or they may be applied onto the dried fiber (off line). It is preferred that the surface treatment agents are applied after drying and, if desired, after drawing.
This is in particular applicable to aramid fibers.
"~
;~ For the application onto the fiber the conventional application means can be employed. These include, for example, metering coating systems, roller-coating `~ systems, serpentine-coating systems or baths.

''~
~ !

o -,.
Prior to, during or after the application an ultra-sonic treatment, an electrostatic treatment or a plasma treatment of the fiber or of the yarn may be carried out. In some cases this will be preferred to improve the penetration of the treatment agent. At all events the suitable equipment as common for the use with solvent-containing formulations may be employed here.
The add-on amount to the fiber is from 0.01 to 12% by weight, based on the fiber weight.
'' The fiber may be dried before or after coating and may optionally also be coated with several layers, i.e.
be dried after a first coating step and then once more be coated in a further bath. Preferably, the first coating step is carried out to apply the epoxide resin solution, and the second coating step is carried out to apply the polyaminoamide solution. The drying process may be carried out by employing convection (for example hot air), heat conduction (e.g. contact drying), radiation (e.g. infrared) or the like. The heat treatment of the fiber is usually conducted within a range of from 80 C to 220 C, while the higher temperatures within said range can be employed only with thermally stable fibers, for example with aramid fibers.
The time of drying may vary from a few seconds to several minutes, dependent on the degree of drying to be attained and on the further intended use of the fiber.
The running speed of the fiber or yarns in the coating apparatus may be selected between a few meters per minute and some hundreds of meters per minute, dependent on the desired amount of product uptake. A lower limit of the drving is about 5 seconds, an upper limit of the running speed is about 750 m/min.

~ ~ .
'`'.~
:"```

.~ ~
?`

ZQ~

The fibers surface-modified according to the invention are useful for a variety of applications. The fibers exhibit a reduced water absorption and reduced coefficients of friction, which properties are important for the further processing steps. For example, in cold-setting adhesion procedures they exhibit an improved substrate adhesion; however, they may also be embedded in synthetic materials (plastics) or included by vulcanization in rubber, whereupon the fibers exhibit an improved binding power to polar as well as apolar rubber types. Furthermore, the polyamide fibers thus coated exhibit a reduced friction to one another.
''"' ,, E X A M P L E S
, ....
EXA~PLE 1 Coating of the Fibers :.~I
An epoxide resin based on tetraglycidyl diamino-diphenylmethane, epoxide value of 33 + 2, was dissolved in toluene/isopropanol (1:1) with moderate heating to , form a 5% by weight solution.
. ,1 3! A polyaminoamide having an amine value of between j 80 and 95 based on fatty acid and diethylenetriamine was `~ dissolved in isopropanol with moderate heating on the ~ analogy of Example 2 of CA 651,745. The solids content ;` of the solution was 12% by weight. Then, the epoxide resin solution and the amine resin solution were diluted to obtain a ratio of the solids contents of epoxide to amine of 2:3. Then, in a first operation, an aromatic polyamide fiber (Kevlar(R)) was beforehand passed :
~`

20~4~2 through the epoxide resin solution, dried with hot air at 200 "c and, in a second operation, passed through the polyamide resin solution, followed by a second step of t drying at 200 oc in a countercurrent of air.
:;~

".,~
The bonding characteristics before and after fatigue were measured by pulling the yarns from the rubber block.

i For the preparation of the test specimens, aramid yarns treated after the first drying ~Kevlar(R), 1670 dtex, 80 T/M} were incorporated in various rubber mixes and cured by 160 C for a period of 20 minutes.
i To this end, the rubber mixes with the yarns were pressed between two platens of an electrically heatable hydraulic press (18 t).

To determine the bond strength of the yarns, the yarns were pulled out of the rubber blocks at a tensile rate of 125 mm/min. The following adhesion values were measured (each in comparison to those of fibers coated with a conventional epoxide resin coating):
Rubber Nix ACM 173 N (173 N) Rubber Mix CR 169 N (141 N) i~ Rubber Mix EPDM 132 N (115 N) . --'~ Example 3 .
A continuous filament aramid fiber of the p-phenyl-enediamine terephthalamide type in the dried (off line) ,l condition was passed through a bath containing the s above-described surface treatment agent of the invention ., .~ .
`'`
`.i 21~

and then dried at about 120 C. The yarn had an initial tension of 0.6 daN; it involved a zero twist 1670 dtex yarn. A dried polyamide fiber ~Kevlar(R) 29), in a first operation, was first passed through the epoxide resin solution (2% by weight of solids content) and then dried with hot air at 200 C and, in a second operation, was passed through the polyamide resin solution (3% by weight), each in polyol/isopropanol, and then dried at 200 ~C in an air countercurrent.
;,' The moisture uptake under Standard Conditions was measured of the yarns thus treated. It was found to be 7.5% by weight for an untreated aramid yarn ~Kevlar(R) 29), 2.4% by weight for the yarn treated according to the invention, and 5% by weight for an equal yarn having a conventional epoxide coating.
~, Rnitting Trials with Treated Yarns In introductory tests the coefficient of friction of treated yarns was determined for comparison to that of untreated yarns. The measurement was carried out in a friction measuring apparatus (Rothschild) according to Standard Conditions. The coefficient of friction yarn-to-metal was 0.40 for the treated yarn and 0.54 for the untreated yarn. The coefficient of friction fiber-to-fiber was 0.055 for the treated yarn, compared to 0.11 for the Standard Product ~Kevlar(R) 29).

Aramid yarns (Kevlar(R)) were knitted on an ELHA(R) circular knitting machine (Model RR~). The test lasted 4 hours. The machine speed was 670 min 1 and the knit-ting speed was 15 m/min. In contrast to untreated fibers, no wear was observed. The structure of the ~;
`~' ' :

Z0~41~9 , knitted goods was uniform. Furthermore, no deposits j were formed on the knitting machine. This means that , the surface treatment agent of the invention clearly improved the knittability of aramid yarns.

., .'~
';

., ~ .

`~`
~:, `!

`~

Claims

1. A polyamide fiber coated with the reaction products from a polyfunctional epoxide compound and a polyamine, characterized in that a polyamide resin containing amino groups is employed as the polyamine.

2. The polyamide fiber according to claim 1, characterized in that the polyamide resin has an amine value of from 20 to 700, and preferably from 70 to 100.

3. The polyamide fiber according to claims 1 or 2, characterized in that a reaction product of a dimer fatty acid with an excess of at least difunctional primary and/or secondary amines which may also contain tertiary amino groups is employed as the polyamide resin containing amino groups.

4. The polyamide fiber according to any one of claims 1 to 3, characterized in that a reaction product of a dimer fatty acid with an excess of primary and/or secondary amines which may also contain tertiary amino groups is employed as the polyamide resin containing amino groups, which contains from 20 to 90%, and prefer-ably from 20 to 60%, of the nitrogen atoms, based on the total number of nitrogen atoms, as ring members of imid-azoline rings.

5. The polyamide fiber according to any one of the preceding claims, characterized in that a reaction product of fatty acids and/or a dimer fatty acid with alkylene diamines, dialkylene triamines and/or the higher homologues thereof is employed as the polyamide resin.

6. The polyamide fiber according to any one of the preceding claims, characterized in that the poly-functional epoxide compound has a functionality between 2 and 4.

7. The polyamide fiber according to any one of the preceding claims, characterized in that the poly-functional epoxide compound has 3 or 4 N-glycidyl groups and/or O-gycidyl groups.

8. The polyamide fiber according to any one of the preceding claims, characterized in that the poly-functional epoxide compound is tetraglycidyl diamino-diphenylmethane.

9. The polyamide fiber according to any one of the preceding claims, characterized in that the cured products of the reaction of the polyfunctional epoxide resin compound with the polyamide resin on the average has terminal amino groups or terminal epoxide groups.

10. The polyamide fiber according to any one of the preceding claims, characterized in that it comprises continuous filaments, staple fibers, fiber tows, yarns, cords or flat textile fabrics at least predominantly derived from aromatic polyamides.

11. A coating imparting bond strength and slip on a polyamide fiber and consisting of a reaction product from polyfunctional epoxides and polyamide resins according to the preceding claims, characterized in that said coating has been prepared by simultaneously or subsequently applying the polyamide resin and the poly-functional epoxide compound as a solution, dispersion or melt to the fiber and then, if so desired, curing same at an elevated temperature.

12. A process for modifying polyamide fibers with the reaction products from polyfunctional epoxides and polyamide resins, in which process the polyamide resin and the polyfunctional epoxide compound simultaneously or subsequently are applied as a solution, dispersion or melt to the fiber and then, if so desired, curing the produced coating at an elevated temperature.

13. The process according to claim 12, characterized in that the fiber is first moved through a solution or slurry of the epoxide resin component and then, option-ally after an intermediate drying step, is moved through a solution or slurry of the polyamide resin and there-after is optionally dried and cured.

14. The process according to claims 12 or 13, characterized in that a reaction product is applied onto the fiber before or after the first drying step.