The present invention relates to high strength ultrahigh molecular weight polyolefin fibers having improved UV stability and the use thereof in, for instance, ropes and fishing nets.
Although ultrahigh molecular weight polyolefin fibers such as high performance polyethylene (HPPE) fibers are generally considered to be relatively stable when exposed to UV, under certain circumstances such fibers may show a loss in tenacity as a result of weathering, which in turn may lead to a reduced life time. These circumstances can in particular occur when such fibers are used in ropes or in fishing lines or fishing nets.
In
A further method to improve the UV stability of a polymeric yarn is to use fibers containing a filler having UV stabilisation properties instead of using fibers coated with a coating containing a UV stabilizer. Such a method is for example described in
The present invention provides an ultrahigh molecular weight polyolefin fiber coated with a coating composition, wherein the coating composition contains a UV stabilizer, characterized in that the amount of UV stabilizer is between 2 wt% and 80 wt.% compared to the total weight of the coating composition based on solids and wherein the coating composition comprises a cross-linked silicone polymer as a carrier for the UV stabilizer. Preferably, said amount of UV stabilizer is at least 5 wt%, more preferably at least 10 wt %, even more preferably at least 20 wt%, most preferably at least 30 wt%. Preferably, said amount of UV stabilizer is at most 75 wt%, more preferably at most 70 wt %, even more preferably at most 65 wt%, most preferably at most 60 wt.%. The weight of the fibers before and after coating followed by drying if necessary is measured to calculate the amount or the weight of the preferably dried coating composition. Preferably, the amount of the coating composition compared to the total weight of the ultrahigh molecular weight polyolefin fiber and based on solids is at least 1 wt %, more preferably at least 4 wt%, most preferably at least 8 wt%. Preferably, said amount of the coating composition is at most 20 wt%, more preferably at most 17 wt%, most preferably at most 15 wt %. In a preferred embodiment, a rope is provided comprising ultrahigh molecular weight polyolefin fibers, wherein the amount of the coating composition compared to the total weight of the rope and based on solids is at between 1 wt % and 30 wt%, more preferably between 2 wt% and 15 wt%. In a further preferred embodiment, a rope is provided, said rope comprising the coated ultrahigh molecular weight polyolefin fibers of the invention, wherein the amount of the coating composition compared to the total weight of the rope and based on solids is at between 1 wt % and 30 wt%, more preferably between 2 wt% and 15 wt%.
The advantage of applying the UV absorber in the coating of the fiber is that the stabiliser protects the fiber against the influence of UV light without having an effect on the mechanical properties of the fiber. Most importantly it was observed that the fibers of the invention may show an improved retention of their mechanical properties and in particular of their tenacity. Moreover, the use of such an absorber does not affect the manufacturing process of the fiber in any way. For the present invention the terms "UV stabilizer" and "UV absorber" are interchangeably used.
In the embodiments of the invention, the UV stabiliser is preferably present in an amount of from 2 wt% to 80 wt.% compared to the total weight of the coating composition, based on solids, i.e. the dry coating composition. Preferably the amount is from 5 wt% to 60 wt.% of stabiliser.
Preferred UV absorbers used in accordance with the invention are compounds that absorb UV radiation such that the UV radiation interacts less with the polymer used to manufacture the fibers. Preferred stabilisers absorb UV in the range of 290 to 400 nm. The stabilisers according to the invention can be organic or inorganic absorbers.
Examples of inorganic stabilisers are carbon black, titanium dioxide (TiO2), ZnO and CeO2.
Examples of organic stabilisers are those falling in the classes of hydroxybenzophenones, hydroxyphenylbenzotriazoles, oxalanilides, phenyl esters, benzooxazinones, cyanoacrylates, formamidine, benzylidene malonates and hydroxyphenyl triazines.
Examples of UV stabilisers suitable for the invention are for instance described in
Further examples of hydroxybenzophenones are 2-Hydroxy-4-n-octoxybenzophenone; 2-Hydroxy-4-methoxybenzophenone; 2-Hydroxy-4-n-dodecyloxy-benzophenone; 2,4-Dihydroxybenzophenone;2-Propenoic acid, 2-(4-benzoyl-3-hydroxyphenoxy)ethyl ester; Methanone, [2-hydroxy-4-(phenylmethoxy)phenyl]phenyl-; 2,2'-Dihydroxy-4-methoxybenzophenone; 2,2',4,4'-Tetrahydroxy benzophenone; 2,2'-Dihydroxy-4,4'-dimethoxybenzophenone; Poly-4-(2-acryloyloxyethoxy)-2-hydroxybenzophenone; Bis-(2-methoxy-4-hydroxy-5-benzoylphenyl)-methane; Methanone, [3-(2,4-dihydroxybenzoyl)phenyl][2-hydroxy-4-(2-propenyloxy)phenyl]-; 2,2-Dihydroxy-4,4'-dimethoxy-benzophenone-5,5'-bis-(sodiumsulphonate); 2-Hydroxy-4-methoxy-benzophenone-5-sulfonic acid; Methanone, [2-hydroxy-4-(2-hydroxyethoxy)phenyl]phenyl-; Mixture of 2,2',4,4'-tetrahydroxybenzophenone and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone ; 1,4-bis(4-benzoyl-3-hydroxyphenoxy)-butane; 2-Butenoic acid, 2-(4-benzoyl-3-hydroxyphenoxy)-1-[(4-benzoyl-3-hydroxyphenoxy)methyl]ethyl ester.
Further examples of hydroxyphenylbenzotriazoles are 2-(2'-Hydroxy-3',5'-di-t-butyl-phenyl)-benzotriazole; 2-(2'-Hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole; Phenol, 2-(5-chloro-2H-benzotriazol-2-yl)-4,6-bis-(1,1-dimethylethyl)-; 2-(2'-Hydroxy-3,5'-di-t-amylphenyl) benzotriazole; Phenol, 2-(2H-benzotriazol-2-yl)-4-methyl- ; Phenol, 2-(2H-benzotriazol-2-yl)-4-(1,1-dimethylethyl)-; Phenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)-; Benzene propanoic acid, 3-(2H-benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-1,6-hexanediylester; Bis[2-hydroxy-5-t-octyl-3-(benzotriazol-2-yl)phenyl]methane; 2-[2-Hydroxy-3,5-di(1,1-dimethylbenzyl)phenyl]2H-benzotriazole; 2-[2-Hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole; Bis[2-hydroxy-5-methyl-3-(benzotriazol-2-yl)phenyl]methane; 2(2'-Hydroxy-5-metacrylyloxyethylphenyl)2H-benzotriazole; Phenol, 2-(2H-benzotriazol-2-yl)-4-(1,1-dimethylethyl)-6-(2-methylpropyl)-; Isomer mixture from the alkylation of 2-(2H-benzotriazole-2-yl)-p-cresol with dodecane; a-[3-[3-(2H-Benzotriazole-2-yl)-5-(1,1-dimethylethel_-4-hydroxyphenyl]-1-oxopropyl]-ω-hydrxypoly(oxox-1,2-etahediyl); α-[3-[3-(2H-Benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropyl]-ω-[3-[3-(2H-Benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]]poly(oxy-1,2-etanediyl); Benzenepropanoic acid, 3-(2H-benzotriazol-2-yl)-5-(1,1- dimethylethyl)-4-hydroxy- C7-9-branched and linear alkyl esters;2-(2H-Benzotriazol-2-yl)-6-(1-methyl-1- phenylethyl)4-(1,1,3,3-tetramethylbutyl)phenol; 2-(2'-Hydroxy-5'-(2-hydroxyethyl))-benzotriazole; 2-(2-hydroxy-4-octyloxyphenyl)- 2H-benzotriazole; Sodium Benzotriazolyl Butylphenol Sulfonate; Octyl-3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazole-2-yl)fenyl]propionaat ;2-Ethylhexyl-3-[3-tertbutyl-4-hydroxy-5-(5-chloro-2H-benzotriazole-2yl) phenyl]propionaat; Phenol, 2-(2H-benzotriazol-2-yl)-6-[[3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]methyl]-4-(1,1,3,3-tetramethylbutyl)-.
Further examples of oxalanilides are 2-Ethoxy-5-t-butyl-2'-ethyl-oxalanilide; 2-Ethyl, 2'-ethoxy-oxalanilide; N-(2-ethoxy-phenyl)-N'-(4-iso-dodecylphenyl)-ethanediamin.
Further examples of phenyl esters are 4-t-Butyl-phenyl-salicylate; 2,4-Di-t-butylphenyl 3,5-di-t-butyl-4-hydroxybenzoate; Benzoic acid, 2-hydroxy-, phenyl ester.
Further examples of Benzooxazinones are 2.2'-(1,4-Phenylene)bis[4H-3,1-benzoxazin-4-one.
Examples of cyanoacrylates are Ethyl 2-cyano-3,3-diphenylacrylate; 2-Ethylhexyl 2-cyano-3,3-diphenylacrylate; 1,3-bis-[2'-cyano-3',3-diphenylacryloyl)oxy]-2,2-bis-{[2-cyano- 3',3'-diphenylacryloyl)oxy]methyl}propane.
Further examples include N-(p-Ethoxy-carbonylphenyl)-N'-methyl-N'-phenylformamidine; N-(p-Ethoxy-carbonylphenyl)-N'-ethyl-N'-phenylformamidine, and 2-Propenoic acid, 3-(4-methoxyphenyl)-, 2-ethylhexyl ester; Propanedioic acid, [(4-methoxyphenyl)-methylene]-dimethyl ester; Tetra-ethyl-2,2'-(1,4-phenylene-dimethylidene)-bismalonate.
Examples of hydroxyphenyl triazines are 2-[4,6-Diphenyl-1,3,5-triazin-2-yl]-5-(hexyl)oxy-phenol; Propanoic acid, 2-[4-[4,6-bis([1,1'-biphenyl]-4-yl)-1,3,5-triazin-2-yl]-3-hydroxyphenoxy]-, isooctyl ester; Phenol, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)- ; 2-[4-[(2-Hydroxy-3-(2'-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6- bis(2,4-dimethylphenyl)-1,3,5-triazine;: 2-[4-[(2-Hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4- dimethylphenyl)-1,3,5-triazine; 2-[4-[(2-Hydroxy-3-tridecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4- dimethylphenyl)-1,3,5-triazine; 2,4-Bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine; 5,5'-Bis(2-ethylhexyloxy)-2,2'-[6-(4-methoxyphenyl)-1,3,5-triazine-2,4-diyl]diphenol; Propanoic acid, 2,2',2"-[1,3,5-triazine-2,4,6-triyltris[(3-hydroxy-4,1-phenylene)oxy]]tris-, 1,1',1"-trioctyl ester;
Most preferred compounds are those with the structures as shown below:
According to a preferred aspect of the invention the coating composition containing the UV absorber further comprises a carrier.
The carrier can be any known coating for ultrahigh molecular weight polyolefin fibers or high strength fibers such as a wax, a polyacrylate coating, a polyurethane coating or silicone coating.
The coating composition used in accordance with the invention comprises a cross-linked silicone polymer as a carrier for the UV stabilizer.
In particular, the invention provides an ultrahigh molecular weight polyolefin fiber or a high strength fiber as described above wherein the coating comprises a cross-linked silicone polymer as a carrier for the UV stabiliser.
Such a coating is for instance described in unpublished patent application
In the present invention, the coating on the ultrahigh molecular weight polyolefin fiber is preferably obtained by applying a coating composition comprising a cross-linkable silicone polymer. After the application of the coating composition to the fibers, the coating composition may be cured, e.g. by heating to cause cross-linking of the cross-linkable silicone polymer. The cross-linking may also be induced by any other suitable methods known to the skilled person. The temperature for curing the coating composition is from 20 to 200 °C, preferably from 50 to 170 °C, more preferably 120 to 150 °C. The curing temperature should not be too low, for the curing to be effective. Should the curing temperature become too high, there is a risk that the ultrahigh molecular weight polyolefin fiber or the high strength fiber deteriorates and loses its strength.
The weight of the fibers before and after coating followed by curing is measured to calculate the weight of the cross-linked coating. For a fiber, the weight of the cross-linked coating is 1 to 20 wt.%, based on the total weight of the fiber, preferably 1 to 10 wt.%. For a rope, preferably, the weight of the cross-linked coating is 1 to 30 wt.% based on the total weight of rope and coating, preferably 2 to 15 wt.%.
The degree of the cross-linking may be controlled. The degree of the cross-linking may be controlled by e.g. the temperature or the time period of the heating. The degree of the cross-linking, if performed in other ways, may be controlled in methods known to the skilled person. The measurement of the degree of the cross-linking may be performed as follows:
- The fibers provided with the (at least partially) cross-linked coating is dipped in a solvent. The solvent is chosen with which the extractables (mainly monomers)groups in the polymer would dissolve which are not cross-linked and the cross-linked network would not dissolve. A preferred solvent is hexane. By weighing the rope or the fibers after the dipping in such a solvent, the weight of the non-cross-linked portion can be determined and the ratio of the cross-linked silicone to the extractables can be calculated.
The preferred degree of cross-linking is at least 30%, i.e. at least 30 wt%, based on the total weight of the coating, of the coating remains on the fibers or rope after extraction with the solvent. More preferably the degree of cross-linking is at least 50%. The maximum degree of cross-linking is about 100%.
Preferably, the cross-linkable silicone polymer comprises a silicone polymer having a reactive end-group. It was found that a cross-linking in the endgroups of the silicone polymer results in a good bending resistance. A silicone polymer which is cross-linked at the end groups rather than at the branches in the repeating unit results in a less rigid coating. Without being limited thereto, the inventors attribute the improved properties of the rope to the less rigid structure of the coating.
Preferably, the cross-linkable end-group is an alkylene end group, more preferably a C2-C6 alkylene end group. In particular the end group is a vinyl group or a hexenyl group. In general, a vinyl group is preferred.
Preferably, the cross-linkable silicone polymer has the formula:
CH2=CH-(Si(CH3)2-O)n-CH=CH2 (1)
wherein n is a number from 2 to 200, preferably from 10 to 100, more preferably from 20 to 50.
Preferably, the coating composition further contains a cross-linker. The cross-linker preferably has the formula:
Si(CH3)3-O-(SiCH3H-O)m-Si(CH3)3 (2)
wherein m is a number n is a number from 2 to 200, preferably from 10 to 100, more preferably from 20 to 50.
Preferably, the coating composition further comprises a metal catalyst for cross-linking the cross-linkable silicone polymer, the metal catalyst preferably being a platinum, palladium or rhodium, more preferably platinum metal complex catalyst. Such catalysts are know to the skilled person.
Preferably, the coating composition is a multi-component silicone system comprising a first emulsion comprising the cross-linkable silicone polymer and the cross-linker and a second emulsion comprising the cross-linkable silicone polymer and the metal catalyst.
Preferably, the weight ratio between the first emulsion and the second emulsion is from about 100:1 to about 100:30, preferably 100:5 to 100:20, more preferably 100:7 to 100:15.
The coating compositions as described above are known in the art. They are often referred to as addition-curing silicone coatings or coating emulsions. The cross-linking or curing takes place when the vinyl end groups react with the SiH group of the cross-linker.
Examples of such coatings are Dehesive® 430 (cross-linker) and Dehesive® 440 (catalyst) from Wacker Silicones; Silcolease® Emulsion 912 and Silcolease® catalyst 913 from Bluestar Silicones; and Syl-off ® 7950 Emulsion Coating and Syl-off ® 7922 Catalyst Emulsion from Dow Corning.
The UV stabiliser of the invention can be included in the carrier composition prior to cross-linking.
Within the context of the present invention, fibers are understood to mean elongated bodies of indefinite length and with length dimension much greater than width and thickness. In one embodiment, the term fiber includes a body chosen from the group consisting of a monofilament, a multifilament yarn, a ribbon, a strip or tape. The fiber can have a regular or an irregular cross-section. The term fibers also includes a plurality of any one or combination of the above.
Thus, the coating according to the invention can be applied to a single fiber or filament, but also to a bundle of more than one fiber, also referred to as a yarn.
Fibers having the form of monofilaments or tape-like fibers can be of varying titer, but typically have a titer in the range of 10 to several thousand dtex, preferably in the range of 100 to 2500 dtex, more preferably 200-2000 dtex. Multi-filament yarns contain a plurality of filaments having a titer typically in the 0.2 - 25 dtex range, preferably about 0.5-20 dtex. The titer of a multifilament yarn may also vary widely, for example from 50 to several thousand dtex, but is preferably in the range of about 200-4000 dtex, more preferably 300-3000 dtex.
With high strength fibers for use in the invention are meant having a tenacity of at least 1.5 N/tex, more preferably at least 2.0 N/tex, even more preferably at least 2.5 N/tex, most preferably at least 3.0 N/tex. In case of ultrahigh molecular weight polyolefin fibers, said fibers preferably have a tenacity of at least 2.0 N/tex, more preferably at least 2.5 N/tex, most preferably at least 3.0 N/tex. Tensile strength, also simply referred to as strength, or tenacity of filaments are determined by known methods, as based on ASTM D2256-97. Generally such high-strength polymeric filaments or ultrahigh molecular weight polyolefin fibers also have a high tensile modulus, e.g. at least 50 N/tex, preferably at least 75, 100 or even at least 125 N/tex.
Examples of high strength fibers are fibers manufactured from polyaramides, e.g. poly(p-phenylene terephthalamide) (known as Kevlar®); poly(tetrafluoroethylene) (PTFE); aromatic copolyamid (co-poly-(paraphenylene/3,4'-oxydiphenylene terephthalamide)) (known as Technora®); poly{2,6-diimidazo-[4,5b-4',5'e]pyridinylene-1,4(2,5-dihydroxy)phenylene} (known as M5); poly(p-phenylene-2, 6-benzobisoxazole) (PBO) (known as Zylon®); thermotropic liquid crystal polymers (LCP) as known from e.g.
A preferred example of ultrahigh molecular weight polyolefin fibers is ultrahigh molecular weight polyethylene fibers.
Most preferred fibers are high performance polyethylene (HPPE) fibers. HPPE fibers are herein understood to be fibers made from ultra-high molar mass polyethylene (also called ultra-high molecular weight polyethylene; UHMWPE), and having a tenacity of at least 1.5 N/tex, preferably at least 2.0 N/tex, more preferably at least 2.5 N/tex or even at least 3.0 N/tex. There is no reason for an upper limit of tenacity of HPPE fibers as HPPE fibers having a tenacity of about 5 or 6 N/tex are also available. The HPPE fibers also have a high tensile modulus, e.g. of at least 75 N/tex, preferably at least 100 N/tex or at least 125 N/tex. HPPE fibers are also referred to as high-modulus polyethylene fibers.
In a preferred embodiment, the HPPE fibers in the invention are one or more multi-filament yarns.
HPPE fibers, filaments and multi-filament yarn, can be prepared by spinning of a solution of UHMWPE in a suitable solvent into gel fibers and drawing the fibers before, during and/or after partial or complete removal of the solvent; that is via a so-called gel-spinning process. Gel spinning of a solution of UHMWPE is well known to the skilled person; and is described in numerous publications, including
HPPE fibers, filaments and multi-filament yarn can also be prepared by melt-spinning of UHMWPE, although the mechanical properties such as tenacity are more limited compared to HPPE fibers made by the gel-spinning process. The upper limit of the molecular weight of the UHMWPE which can be melt-spun is lower than the limit with the gel-spinning process. The melt-spinning process is widely known in the art, and involves heating a PE composition to form a PE melt, extruding the PE melt, cooling the extruded melt to obtain a solidified PE, and drawing the solidified PE at least once. The process is mentioned e.g. in
UHMWPE is understood to be polyethylene having an intrinsic viscosity (IV, as measured on solution in decalin at 135°C) of at least 5 dl/g, preferably of between about 8 and 40 dl/g. Intrinsic viscosity is a measure for molar mass (also called molecular weight) that can more easily be determined than actual molar mass parameters like Mn and Mw. There are several empirical relations between IV and Mw, but such relation is dependent on molar mass distribution. Based on the equation Mw = 5.37 * 104 [IV]1.37 (see
In one embodiment, the UHMWPE contains a small amount, preferably at least 0.2, or at least 0.3 per 1000 carbon atoms, of relatively small groups as pending side groups, preferably a C1-C4 alkyl group. Such a fiber shows an advantageous combination of high strength and creep resistance. Too large a side group, or too high an amount of side groups, however, negatively affects the process of making fibers. For this reason, the UHMWPE preferably contains methyl or ethyl side groups, more preferably methyl side groups. The amount of side groups is preferably at most 20, more preferably at most 10, 5 or at most 3 per 1000 carbon atoms.
The HPPE according to the invention may further contain small amounts, generally less than 5 mass%, preferably less than 3 mass% of customary additives, such as anti-oxidants, thermal stabilisers, colorants, flow promoters, etc. The UHMWPE can be a single polymer grade, but also a mixture of two or more different polyethylene grades, e.g. differing in IV or molar mass distribution, and/or type and number of comonomers or side groups.
The ultrahigh molecular weight polyolefin fibers or the high strength fibers of the invention can be used in any application where such fibers are normally applied. In particular the fibers of the invention can be used in ropes, fishing lines and nets.
Although the invention is here described as a fiber with a coating, according to another embodiment, the coating can also be applied to an article containing the fibers, such as a rope or fishing net. Thus, the invention also relates to an article, preferably a rope or fishing net, coated with a coating composition, wherein the coating composition contains a UV absorber. Preferred embodiments of UV absorber and of the coating composition are as described above.
Methods of making a rope or fishing net are known to the skilled person.
The invention is further illustrated by the Examples below.
The samples were UV-tested according to ISO 4982-2 against their untreated reference yarns over a maximum of 120 days. The time until tenacity decreased with 50% was determined.
Tensile properties were determined on a Zwick 1435, according to ASTM D 2256.
A coating composition was prepared from a first emulsion comprising a reactive silicone polymer preformulated with a cross-linker and a second emulsion comprising a silicone polymer and a metal catalyst. The first emulsion was an emulsion available from Dow Corning containing 30.0-60.0 wt% of dimethylvinyl-terminated dimethyl siloxane and 1.0-5.0 wt% of dimethyl, methylhydrogen siloxane (Syl-off ® 7950 Emulsion Coating). The second emulsion was an emulsion available from Dow Corning containing 30.0-60.0 wt% of dimethylvinyl-terminated dimethyl siloxane and a platinum catalyst (Syl-off ® 7922 Catalyst Emulsion). The first emulsion and the second emulsion were mixed at a weight ratio of 8.3:1.
A third solution is prepared of water and the UV stabiliser, or if the UV stabiliser is in itself a water based solution, this is used as is. The mixture of first emulsion and second emulsion is diluted with this third solution to a predetermined solid content (see Table 1). The amount of UV stabiliser can be determined by adjusting the amount of third solution added.
HPPE fibers, delivered by DSM in the Netherlands as Dyneema ® SK 75, 1760dtex, were dipped in the coating composition at room temperature. The fibers were heated in an oven at a temperature of 120°C so that cross linking takes place.
It can be seen from the examples above that the addition of stabiliser significantly improves the time until tenacity is reduced when the fiber is exposed to UV radiation.