U.S. patent application number 14/398319 was filed with the patent office on 2015-03-26 for thermoplastic fibres with reduced surface tension.
The applicant listed for this patent is LANXESS Deutschland GmbH. Invention is credited to Matthias Bienmueller, Jochen Endtner, Wolfram Littek, Wolfgang Wambach.
Application Number | 20150084231 14/398319 |
Document ID | / |
Family ID | 48407487 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150084231 |
Kind Code |
A1 |
Endtner; Jochen ; et
al. |
March 26, 2015 |
THERMOPLASTIC FIBRES WITH REDUCED SURFACE TENSION
Abstract
The present invention relates to a process for producing
thermoplastic fibres having reduced surface tension and also to
products obtainable by the melt-spinning process from these
thermoplastic fibres having reduced surface tension, wherein the
thermoplastic to be used is admixed with a copolymer of at least
one .alpha.-olefin and at least one acrylic or methacrylic ester of
an aliphatic alcohol.
Inventors: |
Endtner; Jochen; (Cologne,
DE) ; Littek; Wolfram; (Solingen, DE) ;
Bienmueller; Matthias; (Krefeld, DE) ; Wambach;
Wolfgang; (Cologne, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LANXESS Deutschland GmbH |
Cologne |
|
DE |
|
|
Family ID: |
48407487 |
Appl. No.: |
14/398319 |
Filed: |
May 3, 2013 |
PCT Filed: |
May 3, 2013 |
PCT NO: |
PCT/EP2013/059259 |
371 Date: |
October 31, 2014 |
Current U.S.
Class: |
264/211.1 ;
525/176; 525/183 |
Current CPC
Class: |
D01F 6/90 20130101; D01F
6/62 20130101; D01F 6/84 20130101; D01F 6/92 20130101; D01F 1/10
20130101; D10B 2331/04 20130101; D01D 5/08 20130101; D10B 2331/02
20130101; D01F 6/10 20130101; D10B 2401/021 20130101; D01F 6/60
20130101 |
Class at
Publication: |
264/211.1 ;
525/176; 525/183 |
International
Class: |
D01F 6/84 20060101
D01F006/84; D01F 6/60 20060101 D01F006/60; D01D 5/08 20060101
D01D005/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 4, 2012 |
EP |
12166834.7 |
Claims
1. Process for reducing the surface tension of thermoplastic-based
fibres or filaments, the process comprising: introducing into the
thermoplastic at least one E/X copolymer of an .alpha.-olefin and
an acrylic or methacrylic ester of an unsubstituted aliphatic
alcohol having 6 to 30 carbon atoms to produce a
thermoplastic-copolymer mixture, wherein the thermoplastic is
polyamide or polyester; and melt-spinning the
thermoplastic-copolymer mixture into fibres or filaments.
2. Process according to claim 1, wherein the polyesters are
polyalkylene terephthalates.
3. Process according to claim 1, wherein the polyamides are
aliphatic polyamides.
4. Process according to claim 1, wherein mixtures are used for
spinning which are based on 99.9 to 10 parts by weight of at least
one thermoplastic and 0.1 to 20 parts by weight of copolymer.
5. Process according to claim 1, wherein the .alpha.-olefins have
between 2 and 10 carbon atoms and may be unsubstituted or
substituted with one or more aliphatic, cycloaliphatic or aromatic
groups.
6. Process according to claim 5, wherein the .alpha.-olefins are
selected from the group consisting of ethane, propene, 1-butene,
1-pentene, 1-hexene, 1-octene, 3-methyl-1-pentene, and mixtures of
these .alpha.-olefins.
7. Process according to claim 5, wherein the .alpha.-olefin content
of the copolymer is between 50 and 90 wt %.
8. Process according to claim 1, further comprising adding at least
one of: dyes, further hydrophobicizing agents, delustrants,
stabilizers, antistats, lubricants, and branching agents, to the
thermoplastic-copolymer mixture in amounts of 0.001 to 5.0 wt
%.
9. Process according to claim 1, wherein the the E/X copolymer is
an E/X copolymer of ethylene and an acrylic ester of an
unsubstituted aliphatic alcohol having 6 to 30 carbon atoms.
10. Reducing the surface tension of thermoplastic fibres or
thermoplastic filaments by mixing into the thermoplastic at least
one E/X copolymer of an .alpha.-olefin and an acrylic or
methacrylic ester.
11. Process according to claim 2, wherein the polyesters are
selected from the group consisting of polyethylene terephthalates,
polytrimethylene terephthalates, polybutylene terephthalates, or
mixtures of these terephthalates.
12. Process according to claim 5, wherein the .alpha.-olefin
content of the copolymer is between 55 and 75 wt %.
13. Process according to claim 1, wherein the E/X copolymer is an
E/X copolymer of ethylene and an acrylic ester of an unsubstituted
aliphatic alcohol having 6 to 20 carbon atoms.
14. Process according to claim 1, wherein the E/X copolymer is an
E/X copolymer of, ethylene and 2-ethylhexyl acrylate.
Description
[0001] The present invention relates to a process for producing
thermoplastic fibres having reduced surface tension and also to
products obtainable by the melt-spinning process from these
thermoplastic fibres having reduced surface tension, wherein the
thermoplastic to be used is admixed with a copolymer of at least
one .alpha.-olefin and at least one acrylic or methacrylic ester of
an aliphatic alcohol, preferably of a 2-ethylhexanol.
[0002] Products obtained from thermoplastic fibres from the group
of polyamides or polyesters within the meaning of the present
invention are fibrous nonwoven webs, nonwovens, wovens, threads,
yarns, ropes, felts, drawn-loop knits, non-crimp fabrics or
formed-loop knits. Fibrous nonwoven webs or nonwovens are preferred
products within the meaning of the present invention. A fibrous
nonwoven web consists of loosely aggregated fibres yet to be bonded
together. The strength of a fibrous nonwoven web is only based on
the fibre-inherent adherence. The latter, however, can be
influenced by working up. In order that the fibrous nonwoven web
may be processed and used, it needs to be consolidated, for which
various methods can be employed. Only a fibrous nonwoven web which
has been consolidated should be referred to as a nonwoven. This
distinction is not made in colloquial language.
[0003] Nonwovens differ fundamentally from wovens, drawn-loop
knits, non-crimp fabrics and formed-loop knits, which are
characterized by the laying of the individual fibres or threads in
a manner which is determined by the production process. Nonwovens,
by contrast, consist of fibres whose positioning can only be
described by statistical methods.
[0004] The fibres in a nonwoven are disposed randomly to each
other. Nonwovens are classified inter alia according to the fibre
material (the polymer in the case of manufactured fibres, for
example), the bonding process, the fibre type (staple fibre or
continuous-filament fibre), the fibre fineness and the fibre
orientation. The fibres may be deposited in a defined manner in one
preferential direction, or they may be in a state of wholly
stochastic orientation as in the case of the random-laid
nonwoven.
[0005] When the fibres have no preferential direction in their
alignment (orientation), an isotropic nonwoven is concerned. When
the fibres are more frequently disposed in one direction than in
other directions, this is called anisotropy.
[0006] Nonwovens are thus textile fabrics where fabric formation is
effected not by weaving, formed-loop knitting, drawn-loop knitting
or defined laying, but by depositing the fibres with subsequent
fixation. Owing to their versatility in use and their comparatively
low manufacturing costs, compared with woven and loop-drawingly
knitted fabrics, nonwovens continue to enjoy annual growth
rates.
[0007] The advantages of nonwovens reside in a high specific
surface area, the production processes allow huge scope for
variation in density, fibre size, pore size or thickness and lead
to a substantial degree of isotropy in the piece. These
advantageous properties allow numerous possible uses in medicine
for hygiene products, in particular surgical drapes, sheets, wound
coverings, gauze, etc, in the home as wipes of any kind and as
decorative cloths, in particular table cloths, serviettes, in the
clothing industry as interlinings, for technical applications, in
particular insulating mats, covering mats or as filter media in the
engine/motor vehicle sector (e.g. oil filters) or as separators in
batteries (WO 2009/103537 A1).
[0008] The surface tension plays a determinative part for many of
these applications in that a reduced surface tension may lead, for
example, to an increasingly water-repelling behaviour, and this may
play an important part for applications in the clothing industry,
but also in filter media in the motor vehicle sector.
[0009] The production of spunbonded nonwovens constitutes a direct
combination between the process of spinning and the process of web
formation. Not only melt- and dry-spinning processes but also
wet-spinning processes are suitable for web formation on the basis
of continuous-filament fibres. A multiplicity of fibre-forming
polymers are known as a starting material for nonwovens. The
continuous-based nonwovens of the present invention are made from
thermoplastic polymers from the group of polyamides or polyesters,
for example by melt-spinning as so-called meltblown nonwovens. The
process of melt spinning is described in EP 0 880 988 A1 or EP 1
473 070 A1 for polyester for example. Polyester nonwovens are
described in EP 2 090 682 A1 or EP 2 092 921 A1. The use as a
filter medium of polyester nonwovens produced by the meltblown
process forms part of the subject-matter of EP 0 466 381 B1.
[0010] While thermoplastic fibres formed from polyolefins, for
example polypropylene or polyethylene fibres, have a relatively low
surface tension due to the intrinsically hydrophobic character of
polyolefins even without auxiliaries, higher surface tensions are
concerned with comparatively more polar thermoplastics, preferably
polyamides and polyesters. There are numerous applications where
this leads to problems because, although low surface tensions are
needed, comparatively high-value polymers such as polyamides or
polyesters have to be used, for instance because of insufficient
thermal or chemical resistance on the part of polyolefins. This
frequently crystallizes into a wish that even comparatively more
polar thermoplastics, for example polyamides and polyesters, may be
modified to the effect that lower surface tensions are achieved
while retaining the familiar advantages such as, for example, heat
resistance, mechanical robustness and chemical resistance to oils
and motor fuels.
[0011] Influencing the properties of thermoplastic fibres to be
spun by additizing the thermoplastic to be used therefore is
described in DE 19 937 729 A1 with regard to breaking strength
using polyesters as an example. The additive there is a copolyester
containing inter alia acrylic esters or methacrylic esters as
monomer units. WO2005/040257 A1 pursues a similar purpose in using
ethylene-alkyl acrylate copolymers in polyester films, tapes and
melt-spun fibres to improve their mechanical properties such as the
tensile strength for example. Copolymer additions above 5% are
recited therein as preferable.
[0012] FR-OS 239 746 and U.S. Pat. No. 3,378,609 describe oleo- and
hydrophobizing polyester-based wovens by applying an aqueous
emulsion of a fluorinated polymer to the ready-produced woven. EP 0
196 759 A1 describes hydrophobizing individual polyester fibre by
endowing the polyester fibres subsequently with a polyoxyalkylene
glycol and a fluorine-based water and oil repellent, which have no
substantial reactivity with the polyester.
[0013] WO 2009/152349 A1 describes inter alia hygiene cloths
finished with fluorochemicals based on perfluorinated alkyl groups
having up to four carbon atoms as repellent additive. Copolymers of
such perfluorinated substances with acrylate esters or methacrylate
esters are recited by way of example. JP 2003 193331 A describes
rubber reinforcement polyester monofilaments finished inter alia
with copolymers of ethylene with glycidyl methacrylate.
[0014] WO 2005/087868 A1 discloses ethylene copolymer modified
polyamide products which may be fibres obtained by the
melt-spinning process and finished with E/X/Y copolymers where E
represents ethylene, X represents inter alia alkyl acrylate and Y
represents inter alia glycidyl acrylate, glycidyl methacrylate or
glycidyl vinyl ether.
[0015] WO 2008/083820 A1 finally discloses soft yarns based on
polyamide or polyesters which may be finished with softener
polymers of ethylene alkyl acrylates. Methyl acrylate, ethyl
acrylate and butyl acrylate are listed.
[0016] These prior art solutions all have the disadvantage that the
surface tension change resulting in the oil- and water-repellent
behaviour is in each case only realized subsequently in an
additional process step by application of auxiliaries to the woven.
The subsequent application to the surface entails not only a
heightened level of process complexity but also a heightened risk
of the auxiliary desorbing or being washed off, which not only
weakens the surface effect desired but may also be associated with
a problematic contamination of the environment, for example an
impurification of the filtrate in the ease of aftertreated filter
media. It is also frequently necessary to resort to fluorinated
chemicals, which in addition to being very costly also need special
consideration with regard to their toxic potential in relation to
recovery by incineration for example.
[0017] The problem addressed by the present invention was therefore
that of modifying the polyamide/polyester in advance such that a
reduction in surface tension is possible even without
aftertreatment of the products produced from the thermoplastic
fibre in question and shall be achieved with very low usage of
material. The modification should further eschew fluorinated
chemicals, be colour neutral and be such that fibre formation
itself is not unacceptably impaired. The modification for reducing
the surface tension should further be such that auxiliaries added
can be limited by virtue of their effectiveness to a use level
without decisive, if any, effect on the melt-spinning process. The
fibre thus obtained should be variously further processable in that
state into products, particularly into fibrous nonwoven webs,
nonwovens, wovens, drawn-loop knits, non-crimp fabrics or
formed-loop knits having reduced surface tension.
[0018] The solution to the problem and subject-matter of the
present invention is a process for reducing the surface tension of
thermoplastic-based fibres or filaments, characterized in that the
thermoplastic is additized with at least one E/X copolymer of an
.alpha.-olefin and a methacrylic or acrylic ester of an
unsubstituted aliphatic alcohol, preferably an unsubstituted
aliphatic alcohol having 6-30 carbon atoms, more preferably of a
2-ethylhexanol, and the mixture is subsequently spun, preferably by
the melt-spinning process.
[0019] It was found that, surprisingly, additizing the
thermoplastics polyamide or polyester with the E/X copolymer to be
used according to the present invention is very effective in
reducing the surface tension of the corresponding thermoplastic
fibres and their descendant products and thus leads, for example,
to a water-repellent finish for the thermoplastic-based fibres,
preferably the polyamide/polyester fibres, and their descendant
products. The copolymer to be used according to the present
invention is so effective that a substantial reduction in surface
tension is achieved even at very low concentrations, so there is no
decisive if any effect on the melt spinning.
[0020] The process preferably utilizes mixtures for spinning which
are based on 99.9 to 10 parts by weight, preferably 99.5 to 40
parts by weight and more preferably 99.0 to 55 parts by weight of
at least one thermoplastic and 0.1 to 20 parts by weight,
preferably 0.25 to 15 parts by weight, more preferably 0.5 to 10
parts by weight, yet more preferably 0.75 to 6 parts by weight, in
particular most preferably 1.0 to 2.0 wt % of the above-defined E/X
copolymer.
[0021] Preference for use as thermoplastic-based fibres is given to
fibres based on thermoplastic polymers from the group of polyamides
or of polyesters.
[0022] Particular preference for use as thermoplastic-based fibres
from the group of polyamides is given to fibres based on aliphatic
polyamides.
[0023] Particular preference for use as thermoplastic-based fibres
from the group of polyesters is given to fibres based on
polyalkylene terephthalates.
[0024] The thermoplastic polyamides to be spun according to the
present invention may be obtained in various ways and synthesized
from very different building blocks. In the specific application
scenario, they are used alone or in combination with processing
aids, stabilizers, polymeric alloying partners, especially
elastomers. Also suitable are blends with proportions of other
polymers, preferably blends with polyethylene, polypropylene or
ABS, in which case one or more compatibilizers may optionally be
used. The properties of polyamides can be improved by admixture of
elastomers, for example with regard to the breaking strength of,
for example, particularly low-viscosity polyamides. The
multiplicity of possible combinations provides a very large number
of products having a very wide variety of properties.
[0025] Polyamides are obtainable via a multiplicity of existing
procedures involving the use, depending on the desired end product,
of different monomeric building blocks, various chain transfer
agents to achieve a target molecular weight or else monomers having
reactive groups for subsequently intended aftertreatments.
[0026] Industrially relevant processes for producing polyamides
usually proceed via polycondensation in the melt. In this context,
polycondensation also comprehends the hydrolytic polymerization of
lactams.
[0027] Preferred polyamides (PA) are partly crystalline polyamides
obtainable from diamines and dicarboxylic acids and/or lactams
having at least 5 ring members or corresponding amino acids.
[0028] Possible starting materials include aliphatic and/or
aromatic dicarboxylic acids such as adipic acid,
2,2,4-trimethyladipic acid, 2,4,4-trimethyladipic acid, azelaic
acid, sebacic acid, isophthalic acid, terephthalic acid, aliphatic
and/or aromatic diamines such as, for example,
tetramethylenediamine, hexamethylenediamine, 1,9-nonanediamine,
2,2,4-trimethylhexamethylenediamine,
2,4,4-trimethylhexamethylenediamine, the isomeric
diaminodicyclohexylmethanes, diaminodicyclohexylpropanes,
bisaminomethylcyclohexane, phenylenediamines, xylylenediamines,
aminocarboxylic acids such as, for example, aminocaproic acid, and
the corresponding lactams. Copolyamides of two or more of the
monomers mentioned are included.
[0029] The use of caprolactams is particularly preferred and of
.epsilon.-caprolactam is very particularly preferred.
[0030] Particular suitability further extends to most moulding
compounds based on nylon-6, nylon-6,6 and other aliphatic and/or
aromatic polyamides/copolyamides and having 3 to 11 methylene
groups in the polymer chain per polyamide group.
[0031] The polyamides obtained according to the present invention
can also be used in admixture with other polyamides and/or further
polymers.
[0032] The polyamides may include admixtures of customary additives
such as, for example, demoulding agents, stabilizers and/or flow
assistants.
[0033] The thermoplastic polyesters to be spun according to the
present invention are partly aromatic polyesters with particular
preference.
[0034] Polyesters to be spun with particular preference are
selected from the group of derivatives of polyalkylene
terephthalates. Polyesters to be spun with very particular
preference are selected from the group of polyethylene
terephthalates, polytrimethylene terephthalates and polybutylene
terephthalates, yet more preferably polybutylene terephthalate and
polyethylene terephthalate, most preferably polybutylene
terephthalate, or mixtures of these terephthalates.
[0035] Partly aromatic polyesters are materials comprising
aliphatic moieties as well as aromatic moieties.
[0036] Polyalkylene terephthalates for the purposes of the
invention are reaction products of aromatic dicarboxylic acids or
of their reactive derivatives, especially dimethyl esters or
anhydrides, and aliphatic, cycloaliphatic or araliphatic diols and
mixtures of these reactants.
[0037] Preferred polyalkylene terephthalates are obtainable from
terephthalic acid (or its reactive derivatives) and aliphatic or
cycloaliphatic diol of 2 to 10 carbon atoms by known methods
(Kunststoff-Handbuch, vol. VIII, p. 695 FF, Karl-Hanser-Verlag,
Munich 1973).
[0038] Preferred polyalkylene terephthalates contain at least 80
mol % preferably 90 mol %, based on the dicarboxylic acid, of
terephthalic acid radicals and at least 80 mol %, preferably at
least 90 mol %, based on the diol component, of ethylene glycol
and/or 1,3-propanediol and/or 1,4-butanediol radicals.
[0039] Preferred polyalkylene terephthalates may besides
terephthalic acid radicals contain up to 20 mol % of radicals of
other aromatic dicarboxylic acids having 8 to 14 carbon atoms or
radicals of aliphatic dicarboxylic acids having 4 to 12 carbon
atoms, in particular radicals of phthalic acid, isophthalic acid,
naphthalene-2,6-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid,
succinic acid, adipic acid, sebacic acid, azelaic acid,
cyclohexanediacetic acid, cyclohexanedicarboxylic acid.
[0040] Preferred polyalkylene terephthalates may besides
ethylene/1,3-propanediol/1,4-butanediol glycol radicals contain up
to 20 mol % of other aliphatic diols havinig 3 to 12 carbon atoms
or cycloaliphatic diols having 6 to 21 carbon atoms, in particular
radicals of 1,3-propanediol, 2-ethyl-1,3-propanediol,
neopentylglycol, 1,5-pentanediol, 1,6-hexanediol,
1,4-cyclohexanedimethanol, 3-methyl-2,4-pentanediol,
2-methyl-2,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol,
2,2,4-trimethyl-1,6-pentanediol 2-ethyl-1,3-hexanediol,
2,2-diethyl-1,3-propanediol, 2,5-hexanediol,
1,4-di(.beta.-hydroxyethoxy)benzene,
2,2-bis(4-hydroxycyclohexyl)propane,
2,4-dihydroxy-1,1,3,3-tetramethylcyclobutane,
2,2-bis(3-.beta.-hydroxyethoxyphenyl)propane
2,2-bis(4-hydroxypropoxyphenyl)propane (DE-A 25 07 674 (=U.S. Pat.
No. 4,086,212), DE-A 25 07 776, DE-A 27 15 932 (=U.S. Pat. No.
4,176,224)).
[0041] Polyalkylene terephthalates may be branched by incorporation
of relatively small amounts of 3- or 4-hydric alcohols or 3- or
4-basic carboxylic acids as described for example in DE-A 19 00 270
(=U.S. Pat. No. 3,692,744). Examples of preferred branching agents
are trimesic acid, trimellitic acid, trimethylolethane,
trimethylolpropane and pentaerythritol.
[0042] It is not advisable to use more than 1 mol % of the
branching agent, based on the acid component.
[0043] Particular preference is given to polyalkylene
terephthalates formed solely from terephthalic acid and its
reactive derivatives, in particular its dialkyl esters, and
ethylene glycol and/or 1,3-propanediol and/or 1,4-butanediol, in
particular to polyethylene terephthalate and polybutylene
terephthalate, and mixtures of these polyalkylene
terephthalates.
[0044] Preferred polyalkylene terephthalates further include
copolyesters formed from at least two of the abovementioned acid
components and/or from at least two of the abovementioned alcohol
components, particularly preferred copolyesters being poly(ethylene
glycol/1,4-butanediol)terephthalates.
[0045] Polyalkylene terephthalates generally have an intrinsic
viscosity of about 0.3 dl/g to 1.5 cm.sup.3/g, preferably 0.4 dl/g
to 1.3 dl/g, more preferably 0.5 dl/g to 1.0 dl/g, all measured in
1:1 (w/w) phenol/o-dichlorobenzene at 25.degree. C.
[0046] The thermoplastic polyesters which are preferably spun
according to the present invention can also be used in admixture
with other polyesters and/or further polymers. Very particular
preference is given to using polyethylene terephthalate (PET),
polypropylene terephthalate or polybutylene terephthalate (PBT) or
mixtures thereof, in particular polybutylene terephthalate.
[0047] Recycled polyesters from post- or pre-consumer recyclates
may further also be used alone or mixed, in which case polyester
recyclates from bottles, so-called PET copolyesters, are preferred.
One example thereof appears to be PET Plus80.RTM. from PET
Kunststoffrecycling GmbH, Beselich-Obertiefenbach, Germany.
[0048] Particular preference for use as polyesters in melt spinning
is given to poly(C.sub.2-talkylene)terephthalates containing up to
15 mol % of other dicarboxylic acids and/or diols, in particular
isophthalic acid, adipic acid, diethylene glycol, polyethylene
glycol, 1,4-cyclohexanedimethanol, or whichever are the other
C.sub.2-talkylene glycols. Preference is given to polyethylene
terephthalate having an intrinsic viscosity (I.V.) in the range
from 0.5 to 1.4 dl/g, polypropylene terephthalate having an I.V. of
0.7 to 1.6 dl/g or polybutylene terephthalate having an I.V. of 0.5
to 1.8 dl/g, while polyethylene terephthalate having an intrinsic
viscosity (I.V.) in the range from 0.6 to 1.0 dl/g or polybutylene
terephthalate having an I.V. of 0.6 to 0.9 dl/g is particularly
preferable.
[0049] To reduce their surface tension, the thermoplastics to be
spun according to the present invention contain E/X copolymers of E
at least one .alpha.-olefin with X a methacrylic or acrylic ester
of an unsubstituted aliphatic alcohol. Preferred .alpha.-olefins
for use as constituent E of the copolymers preferably have between
2 and 10 carbon atoms and may be unsubstituted or substituted with
one or more aliphatic, cycloaliphatic or aromatic groups. Preferred
.alpha.-olefins are selected from the group comprising ethene,
propene, 1-butene, 1-pentene, 1-hexene, 1-octene,
3-methyl-1-pentene. Particularly preferred .alpha.-olefins are
ethene and propene, ethene is very particularly preferable.
Mixtures of the described .alpha.-olefins are also suitable.
[0050] The .alpha.-olefin content of the E/X copolymer is between
50 and 90 wt %, preferably between 55 and 75 wt %.
[0051] The E/X copolymer is further defined by the second
constituent in addition to the .alpha.-olefin. Suitable for use as
the second constituent are alkyl or arylalkyl esters of acrylic
acid or of methacrylic acid whose alkyl or arylalkyl group is
formed from 5-30 carbon atoms and which contains only a minimal if
any concentration of reactive functions selected from the group
comprising epoxides, oxetanes, anhydrides, imides, aziridines,
furans, acids, amines. The alkyl or arylalkyl group may be linear
or branched and also contain cycloaliphatic or aromatic groups
while also being substituted by one or more ether or thioether
functions. Suitable methacrylic or acrylic esters in this context
also include those which were synthesized from an alcohol component
based on oligoethylene glycol or oligopropylene glycol having only
one hydroxyl group and not more than 30 carbon atoms.
[0052] The alkyl or arylalkyl group of the methacrylic or acrylic
ester is preferably selected from the group comprising 1-hexyl,
2-hexyl, 3-hexyl, 1-heptyl, 3-heptyl, 1-octyl, 1-(2-ethyl)hexyl,
1-nonyl, 1-decyl, 1-dodecyl, 1-lauryl or 1-octadecyl. Particular
preference is given to unsubstituted alkyl or arylalkyl groups of
6-20 carbon atoms, more preferably 8-20 carbon atoms. Preference is
given in particular also to branched alkyl groups which, compared
with linear alkyl groups of the same number of carbon atoms, lead
to a lower glass transition temperature T.sub.G.
[0053] Of particular preference for the purposes of the present
invention are copolymers where the .alpha.-olefin is copolymerized
with 2-ethylhexyl acrylate.
[0054] Mixtures of the acrylic or methacrylic esters described are
likewise suitable.
[0055] The acrylic or methacrylic ester content of the copolymer is
in the range from 10 to 50 wt %, preferably in the range from 25
and 45 wt %.
[0056] Especially suitable copolymers are selected from the group
of materials which are available from Arkema under the brand name
Lotryl.RTM. EH, some of which are also used as hot-melt
adhesives.
[0057] The particular preference of the present invention is
accordingly for a process for reducing the surface tension of
polyester-based fibres or polyamide-based fibres that is
characterized in that an E/X copolymer of ethylene and an acrylic
ester of an unsubstituted aliphatic alcohol having 6 to 30 carbon
atoms, preferably of E ethylene and X an acrylic ester having 6 to
20 carbon atoms, more preferably of E ethylene and X 2ethylhexyl
acrylate, is added to the thermoplastic and the mixture is
subsequently spun by the melt-spinning process.
[0058] The particular preference of the present invention is
accordingly for a process for reducing the surface tension of
polyester-based fibres that is characterized in that an E/X
copolymer of ethylene and an acrylic ester of an unsubstituted
aliphatic alcohol having 6 to 30 carbon atoms, preferably of E
ethylene and X an acrylic ester having 6 to 20 carbon atoms, more
preferably of E ethylene and X 2-ethylhexyl acrylate, is added to
the thermoplastic and the mixture is subsequently spun by the
melt-spinning process.
[0059] The particular preference of the present invention is
accordingly for a process for reducing the surface tension of
polyamide-based fibres that is characterized in that an E/X
copolymer of ethylene and an acrylic ester of an unsubstituted
aliphatic alcohol having 6 to 30 carbon atoms, preferably of E
ethylene and X an acrylic ester having 6 to 20 carbon atoms, more
preferably of E ethylene and X 2-ethylhexyl acrylate, is added to
the thermoplastic and the mixture is subsequently spun by the
melt-spinning process. The copolymer quantity to be added to the
polyamide/polyester mixture to be processed by spinning, for
example, was specified above and will be found sufficient in most
cases if it is .gtoreq.6 wt %. The concentration of the copolymer
is preferably chosen from within the range from 0.75 to 6.0 wt %
according to the desired take-off speed (>700-1500 m/min) such
that the birefringence of the fibre is <3.510-3. Fibre
birefringences of this type allow draw ratios of 5:1 and ensure the
desired high thread tenacities at wind-up speeds of distinctly
above 3800 m/min irrespective of the spinning take-off speed of up
to 1500 m/min.
[0060] Customary added substances, preferably dyes, further
hydrophobicizing agents, delustrants, stabilizers, antistats,
lubricants, branching agents, may safely be added to the
thermoplastic-copolymer mixtures of the present invention in
amounts of 0.001 to 5.0 wt %.
[0061] Dyes which may be used with preference are disperse dyes, in
particular those based on azo dyes or those based on very finely
divided carbon blacks.
[0062] Delustrants which may be used with preference are
microcrystalline anatases having an average particle size [d50] of
0.25 to 0.35 .mu.m, which may also have an organic or inorganic
surface treatment.
[0063] Stabilizers which may be used with preference include, for
example, aromatic polycarbodiimides such as, for example, Stabaxol
P from Rheinchemie of Mannheim, Germany, but also thermal
stabilizers based on organic phosphite derivatives.
[0064] Antistats which may be used with preference are, in
particular, finely divided conductivity-grade carbon blacks or
carbon nanotubes.
[0065] Lubricants which may be used with preference are, in
particular, long-chain fatty acids, preferably stearic acid or
behenic acid, salts thereof, preferably calcium stearate or zinc
stearate, and also ester derivatives thereof, and also low
molecular weight polyethylene waxes and/or polypropylene waxes.
Montan waxes within the meaning of the present invention are
mixtures of straight-chain, saturated carboxylic acids having chain
lengths of 28 to 32 carbon atoms. Preferred lubricating and/or
demoulding agents are compounds from the group of low molecular
weight polyethylene waxes and also from the group of amides or
esters of saturated or unsaturated aliphatic carboxylic acids
having 8 to 40 carbon atoms with aliphatic saturated amines or
alcohols having 2 to 40 carbon atoms. Ethylenebisstearylamide and
pentaerythritol tetrastearate (PETS) are very particularly
preferable for the purposes of the present invention.
Pentaerythritol tetrastearate (PETS) in particular is very
particularly preferable.
[0066] Branching agents which may be used with preference are
meltable modified bisphenol A epichlorohydrin resins such as, for
example, Araldite GY764CH or Araldite GT7071 from Huntsman of
Everberg, Belgium.
[0067] The copolymer to be used according to the present invention
is mixed with the polyamide/polyester matrix polymer by
compounding, preferably via mixing elements in an extruder, by
using static mixer or via other suitable devices capable of mixing
two or more components with each or one another. The melt may
optionally also be strand extruded, cooled and pelletized.
[0068] Masterbatch techniques are also possible, in which case the
copolymer is mixed as a concentrate or as a pure substance with the
polyester pellets.
[0069] However, the individual components may also be mixed
directly in the spinning or meltblowing installation, in which case
the components may be imported as a physical premixture via one
feed port or else separately via two or more feed ports. Another
practicable possibility is for them to be added to a substream of
the matrix polymer which is then admixed to the main stream of the
matrix polymer. Advantageously, a defined distribution is
established there by the specific choice of mixer and the duration
of the mixing operation, before the melt mixture is forwarded
through product distribution lines to the individual spinning
stations and spinning dies. Mixers having a shear rate of 16 to 128
sec.sup.-1 will be found advantageous. In effect, the product
formed by multiplying the shear rate (sec.sup.-1) with the
0.8.sup.th power of the residence time (in sec) should preferably
be 250-2500, more preferably in the range from 350 to 1250. Values
above 2500 are generally avoided in order to limit the pressure
drop in the pipework lines. For the avoidance of doubt, it may be
noted the thermoplastic is herein also referred to using the term
polymer.
[0070] Shear rate herein is defined as the superficial shear rate
(sec.sup.-1) times the mixer factor, the mixer factor being a
characteristic parameter of the type of mixer. For Sulzer SMX
types, for example, this factor is about 7-8. The superficial shear
rate .gamma. computes as per
.gamma. = 4 10 3 F .pi. .delta. R 3 60 [ sec - 1 ] ##EQU00001##
[0071] and the residence time as per
t = V 2 .delta. 60 F ##EQU00002##
[0072] where
[0073] F=polymer pump rate (g/min)
[0074] V.sub.1=internal volume of empty tube (cm.sup.3)
[0075] R=empty tube diameter (mm)
[0076] .epsilon.=empty-volume fraction (from 0.84 to 0.85 for
Sulzer SMX types)
[0077] .delta.=nominal density of polymer mixture in melt (about
1.2 g/cm.sup.3).
[0078] Not only the mixing of the polymers but also the subsequent
spinning of the polymer mixture is generally carried out at
temperatures which, depending on the matrix polymer, are preferably
in the range from 5 to 85.degree. C. and more preferably from 30 to
70.degree. C., each above the melting temperature of the matrix
polymer. The preferred temperature settings are from 265 to
340.degree. C. for PET and from 225 to 300.degree. C. for nylon-6
and PBT.
[0079] Fibrous nonwoven webs produced from the thermoplastic to be
used according to the present invention are produced in, for
example, a meltblown plant. An extruder therein is used to heat the
components and bring them to a high pressure. Following optional
prefiltration by a suitable filter assembly, the melt is then
pressed by the spinning pumps at an accurately metered rate through
a spinneret. The polymer exits from the die plate as a fine
fibre--also called filament in textile terminology--while still in
the molten form. An air stream cools the filament and stretches it
while still in the melt. The air stream conveys the filament onto,
for example, a conveyor belt constructed as a sieve, or onto a
porous drum or onto an incoming substrate such as, for example,
paper. Aspiration underneath the sieve belt causes the threads to
become fixed. This random-laid sheet of fibre is a fibrous nonwoven
web which needs to be consolidated. Consolidation may be effected,
for example, by two heated rolls (calender) or by a vapour stream.
When a calender is used to effect consolidation, one of the two
rolls usually has an engraved pattern consisting of dots, short
rectangles or lozenge-shaped dots. The filaments fuse at the points
of contact and thus form the nonwoven fabric. Comparatively
lightweight nonwoven fabrics are obtainable by this technique
(thermobonding) only, while comparatively heavyweight nonwoven
fabrics are produced with a second incorporated low-melting polymer
by melting the hot-melt adhesive in the course of a pass through a
so-called fixing oven and the matrix fibres are usually adhered
together at their cross-over points to thereby ensure the
tenacities desired for the nonwoven. Consolidation is further
possible by the method of hydroentangling, in which jets of water
impinge on the still unconsolidated web at water pressures up to
400 bar.
[0080] The meltblown process is typically operated with the
following parameters:
[0081] fibre diameter 0.1 .mu.m to 20 .mu.m, preferably 1 to 10
.mu.m
[0082] web width up to 5000-6000 mm
[0083] air temperature 230 to 400.degree. C., preferably
290.degree. to 370.degree. C.
[0084] air speed 0.5-0.8 times the speed of sound
[0085] basis weight 8 to 350 g/m.sup.2, typically 20 to 200
g/m.sup.2
[0086] holes in spinneret O100 to 500 .mu.m with 1 to 6
holes/mm
[0087] High-tenacity filaments are preferably produced from the
thermoplastic-based mixtures to be used according to the present
invention, preferably the polyamide/polyester mixtures, by spinning
at take-off speeds of >700 m/min, more preferably in the range
from 750 to 1000 m/min, and drawing, heat-setting and winding up at
a corresponding speed. This is accomplished using spinning means
known per se.
[0088] High-tenacity polyamide/polyester filaments are typically
produced by the melt-spinning process in large direct-melt spinning
installations in which the melt is distributed via heated product
lines to the individual spinlines and to the individual spinning
systems within the spinlines. A spinline is a string or one or more
rows of spinning systems, while a spinning system is the smallest
spinning unit with a spinhead, which contains at least one spinning
die pack including spinning die plates. The melt in such systems is
exposed to a high level of thermal stress in residence times up to
35 min. The effectiveness of the copolymer which, according to the
present invention, is to be used for reducing the surface tension
is not significantly affected as a consequence of the high thermal
stability of the copolymer, so even small quantities of the
additive, for example .ltoreq.2.0% and in many cases even
.ltoreq.1.5%, are sufficient depending on the desired reduction in
the surface tension--despite high thermal stress.
[0089] The die pack to be used according to the present invention
preferably has at least 20, more preferably from 150 to 1500 and
even more preferably from 500 to 1000 die holes per metre of die
width. Die hole diameters from 0.05 to 1 mm and particularly from
0.3 to 0.5 mm are preferable.
[0090] Die exit speed is preferably in the range from 1 to 20
m/min, but more preferably from 3 to 10 m/min. The blowing stream
of hot air causes the extruded threads to become drawn to
preferably from 50 to 800 times their length post die exit, leading
to spinning speeds of up to 10 000 m/min.
[0091] The present invention also relates to the use of at least
one copolymer of at least one .alpha.-olefin and at least one
acrylic or methacrylic ester for reducing the surface tension of
thermoplastic-based fibres or filaments, preferably polyester-based
fibres or filaments or polyamide-based fibres or filaments, more
preferably polyester-based fibres or filaments.
[0092] The present invention further relates to fibres or filaments
having reduced surface tension obtainable by melt spinning
thermoplastic-based fibres or filaments additized with at least one
copolymer of at least one .alpha.-olefin and at least one acrylic
or methacrylic ester of an aliphatic alcohol.
[0093] The present invention also relates to products, preferably
fibrous nonwoven webs, nonwovens, wovens, drawn-loop knits,
non-crimp fabrics or formed-loop knits, in particular fibrous
nonwoven webs or nonwovens, obtainable from reduced surface tension
thermoplastic-based fibres of the present invention, preferably
polyester-based fibres or filaments or polyamide-based fibres or
filaments, each of reduced surface tension, which were additized
with at least one copolymer of at least one .alpha.-olefin and at
least one acrylic or methacrylic ester.
[0094] It may be noted for clarity that all the definitions and
parameters recited hereinabove in general terms or in preferred
combinations are encompassed in any desired combinations in the
context of the present invention.
[0095] Generally, the surface tension of fibres can be determined
from their wettability with liquids that differ in polarity. A
further possible way to determine the surface tension on fibre
products obtained according to the present invention involves using
a suitable tensiometer to examine the absorption kinetics of a
liquid medium (e.g. water or cyclohexane) absorbed by the fibre
product.
EXAMPLES
[0096] The reduction in the surface tension of materials obtained
according to the present invention is demonstrated quantitatively
on injection-moulded plates, which serve as model system for exact
determination of surface tension, and qualitatively on fibrous
nonwoven webs obtained by the meltblown process.
[0097] Determination of Reduced Surface Tension on
Injection-Moulded Plates:
[0098] To exemplify the surface tension reduction described in the
present invention, corresponding moulding compounds were prepared
first. For this, the individual components were mixed in a
twin-screw extruder (ZSK 26 Mega Compounder from Coperion Werner
& Pfleiderer (Stuttgart, Germany)) at temperatures between 250
and 285.degree. C., strand extruded, cooled to the point of
pelletizability, and pelletized. After drying (generally 2-6 h at
80.degree. C. in a vacuum drying cabinet), the pellets were
processed into test specimens.
[0099] The test specimens (rectangular plates measuring 60*40*4 mm
or 150*105*1.0 mm) for the tests reported in tables 1 and 2 were
produced on an Arburg 320-210-500 type injection-moulding machine
at a melt temperature of about 260.degree. C. and a mould
temperature of about 80.degree. C.
[0100] The surface tension of the rectangular plates obtained from
the materials produced according to the present invention was
determined in accordance with DIN ISO 8296 using test inks in a
simple and reproducible manner.
[0101] The surface tensions to DIN ISO 8296 are generally not
comparable to the values obtained according to ASTM D 2587-84.
Surface tension values are reported in nN/m (=dyn/cm).
[0102] The test method is based on the assessment of the degree to
which the polymer surface of the test specimen is wetted by inks
having different surface tensions. The applicator attached to the
bottle closure is dipped into the test ink, brushed against the
bottle rim and used to apply the ink without delay to the in-test
surface. Stroke length should be at least 100 mm. The behaviour of
the stroke edge is assessed over a length of 90%, so minimal
inhomogeneities are not considered. If the ink stroke contracts
within less than two seconds, the measurement must be repeated with
an ink of lower surface tension until the edges persist for two
seconds. If the ink stroke remains unchanged for more than two
seconds, the measurement must be repeated with inks of higher
surface tension until the two seconds are achieved. The value
indicated on the bottle then corresponds to the surface energy of
the test plate. The test must be carried out under 23/50 standard
conditions, i.e. at an air temperature or 23.degree. C.+/-2.degree.
C. and relative humidity of 50%+/-10%.
[0103] The present tests were carried out with test inks from
Softal Electronic GmbH, (see Softal Report No. 108), Hamburg,
Germany.
[0104] Determination of Surface Tension on Fibrous Nonwoven
Webs:
[0105] To reduce the surface tension on thermoplastic fibres in the
manner of the present invention, a meltblown apparatus was used to
produce fibrous nonwoven webs having a basis weight of about 55
g/m.sup.2. The tests were carried out with the melt temperature at
about 275.degree. C. and the hot-air stream at about 360.degree. C.
The ratio between melt throughput and air volume flow was chosen so
as to obtain an average fibre thickness of about 1 .mu.m from a die
diameter of 300 .mu.m. The fibrous nonwoven webs described in the
inventive and comparative examples differ only in the particular
polymer compositions used, all other parameters and hence nonwoven
parameters such as basis weight, pore size, fibre orientation and
fibre thickness being kept the same for each pair of inventive and
comparative examples.
[0106] For a qualitative assessment of surface tension, a droplet
of water was applied to the fibrous nonwoven web. Rapid wetting of
the web with the droplet of water indicates a high level of surface
tension (hydrophilic behaviour), while a retained droplet shape on
the surface suggests a low level of surface tension. To achieve
further differentiation, an air stream was applied to the droplet.
If the droplet leaves behind a trail in the form of a film of
water, it can be qualitatively summarized that the surface tension
is comparatively high; if the droplet moves across the fibrous
nonwoven web without leaving behind a visible trail of water, a
comparatively low level of surface tension can be summarized (see
table 3).
[0107] The following were used in the tests:
[0108] component A1: linear polybutylene terephthalate (Pocan.RTM.
B600 from Lanxess Deutschland GmbH, Leverkusen, Germany) having an
intrinsic viscosity of about 69 cm.sup.3/g (measured in 1:1
phenol:1,2-dichlorobenzene at 25.degree. C.)
[0109] component A2: linear polybutylene terephthalate (Pecan.RTM.
B1300 from Lanxess Deutschland GmbH, Leverkusen, Germany) having an
intrinsic viscosity of about 94 cm.sup.3/g (measured in 1:1
phenol:1,2-dichlorobenzene at 25.degree. C.)
[0110] component A3: PET copolymer having an intrinsic viscosity of
about 80 cm.sup.3/g (PETplus 80 from PET Kunststoffrecycling GmbH,
Beselich-Obertiefenbach, Germany)
[0111] component A4: nylon-6 (Durethan.RTM. B40F from Lanxess
Deutschland GmbH, Leverkusen, Germany)
[0112] component B1: copolymer of ethene and 2-ethylhexyl acrylate
having an ethene fraction of 63 wt % and an MFI of 550 (Lotryl.RTM.
37 EH 550 from Arkema, Puteaux, France) [CAS No. 26984-27-0]
[0113] component B2: Lotryl.RTM. 35 BA 320: copolymer of ethene and
n-butyl acrylate having an ethene fraction of 65 wt % and an MFI of
320 (Lotryl.RTM. 35 BA 320 from Arkema, Puteaux, France) [CAS No.
25750-84-9]
TABLE-US-00001 TABLE 1 Surface tension reduction in polyester
fibres as modelled with injection-moulded plate [60 .times. 40
.times. 4 mm] Example Comp. 1 Inv. 1 Inv. 2 Comp. 2 Inv. 3 Inv. 4
Comp. 6 Comp. 5 Comp. 3 Inv. 6 Comp. 4 Inv. 7 Inv. 8 component A1
[%] 100 99 96 component A2 [%] 100 97 94 97 94 50 48.5 47 component
A3 [%] 100 97 50 48.5 47 component B1 [%] 1 4 3 6 3 3 6 component
B2 [%] 3 6 surface tension [mN/m] 38 36 30 40 30 30 34 30 36 30 36
30 30
TABLE-US-00002 TABLE 2 Surface tension reduction in polyamide
fibres as modelled with injection- moulded plate [150 .times. 105
.times. 1 mm] Example Comp. 5 Inv. 9 Inv. 10 component A4 [%] 100
99 95 component B1 [%] 1 5 surface tension [mN/m] 54 36 <34
[0114] A high value indicates a high level of surface tension and
hence indicates hydrophilic behaviour, whereas the material becomes
increasingly hydrophobic with decreasing surface tension value. The
examples show that the surface tension can only be reduced down to
a limit of 30 mN/m in that the value of 30 mN/m represents a point
of saturation. In the prior art (component B2 in Comparative
Example 5) this limit is only achieved with 6 wt % of copolymer of
ethylene and butyl acrylate. When only 3 wt % are used, the surface
tension can only be reduced down to 34 mN/m. A comparison between
the surface tensions of component B1 and component B2 shows that
component B1, a copolymer of ethylene and 2-ethylhexyl acrylate,
delivers a very low surface tension of just 30 mN/m even if used at
a very low dosage level of, for example, 3 wt %.
TABLE-US-00003 TABLE 3 Surface tension reduction on nonwoven
polyester webs Example Comp. 1 Inv. 1 Inv. 2 component A1 [%] 100
99 98 component B1 [%] 1 4 behaviour of water droplet wets the
droplet scarcely wets droplet scarcely wets droplet on web surface
and spreads the surface and persists the surface and persists as an
almost spherical shape as an almost spherical shape behaviour of
water droplet wets the surface droplet can be blown droplet can be
blown droplet on web after so severely that it is virtually away,
but leaves a readily away without leaving behind a visible
application of air stream impossible to blow away visible trail of
water water residue on the web surface
[0115] The fact that the adherence of the water droplet decreases
severely with increasing concentration of component B1 is
indicative of the severely decreasing wettability of the web with
water and thus indicates the surface tension reduction in the
polyester films used for the web. Just one 1 wt % of component B1
is sufficient for it to achieve a decisive increase in
hydrophobicity.
* * * * *