U.S. patent application number 17/414631 was filed with the patent office on 2022-03-03 for stretched fluoropolymers.
This patent application is currently assigned to Evonik Operations GmbH. The applicant listed for this patent is Evonik Operations GmbH. Invention is credited to Dirk Heinrich BUECKER, Lan DE GANS LI, Markus HARTMANN, Martin WIELPUETZ.
Application Number | 20220064821 17/414631 |
Document ID | / |
Family ID | 1000006013773 |
Filed Date | 2022-03-03 |
United States Patent
Application |
20220064821 |
Kind Code |
A1 |
DE GANS LI; Lan ; et
al. |
March 3, 2022 |
STRETCHED FLUOROPOLYMERS
Abstract
The present invention is directed to stretched filaments based
on fluoropolymers, where the filaments were stretched at a
temperature between 70.degree. C. and the Vicat temperature and
where the filaments are cooled under full tensile load to room
temperature.
Inventors: |
DE GANS LI; Lan; (Muelheim
an der Ruhr, DE) ; WIELPUETZ; Martin; (Senden,
DE) ; HARTMANN; Markus; (Sendenhorst, DE) ;
BUECKER; Dirk Heinrich; (Ratingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Evonik Operations GmbH |
Essen |
|
DE |
|
|
Assignee: |
Evonik Operations GmbH
Essen
DE
|
Family ID: |
1000006013773 |
Appl. No.: |
17/414631 |
Filed: |
December 17, 2019 |
PCT Filed: |
December 17, 2019 |
PCT NO: |
PCT/EP2019/085717 |
371 Date: |
June 16, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D01F 6/12 20130101; D02J
1/224 20130101 |
International
Class: |
D01F 6/12 20060101
D01F006/12; D02J 1/22 20060101 D02J001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2018 |
EP |
18212857.9 |
Claims
1. A process for producing stretched filaments comprising at least
80% by weight of at least one fluoropolymer, the process
comprising: stretching raw filaments with a stretching factor
greater than or equal to 3 at a temperature between 70.degree. C.
and a Vicat temperature of the at least one fluoropolymer, which is
determined in accordance with DIN EN ISO 306:2004-10 B50, and
cooling the raw filaments after stretching under full tensile load
to below 50.degree. C., wherein the stretched filaments have a
rectangular cross section where a thickness thereof is less than a
width thereof, wherein the stretched filaments are made of
non-perfluorinated polymers.
2. The process according to claim 1, where the at least one
fluoropolymer is selected from the group consisting of
polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene
copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer
(E-CTFE), polychlorotrifluoroethylene (PCTFE), ETFE modified by a
tercomponent or modified by vinylidene fluoride, and copolymers
based on vinylidene fluoride which comprise up to 40% by weight of
other monomers.
3. The process according to claim 1, where the Vicat temperature of
the at least one fluoropolymer is at least 80.degree. C.
4. Stretched filaments produced by the process according to claim
1, having a width to thickness ratio of at least 25.
5. A composite comprising the stretched filaments according to
claim 4.
6. A winding layer comprising the stretched filaments according to
claim 4.
Description
[0001] The present invention is directed to stretched filaments
based on non-perfluorinated fluoropolymers, where the filaments
were stretched at a temperature between 70.degree. C. and the Vicat
temperature and where the filaments are cooled under full tensile
load to room temperature.
[0002] Fibre-reinforced materials are usually based on the use of
glass fibres or carbon fibres in polymers. This raises the
fundamental problem of compatibility of the fibres with the matrix
material and resultant problems in achieving binding between
reinforcing material and matrix. This is often a particular problem
when thermoplastics are used as matrix. These materials are
moreover not recyclable, because it is very difficult to remove the
fibres.
[0003] The main disclosures in the prior art relate to two
processes for the stretching of polyolefins, for example
polyethylene or polypropylene: the melt spinning process (WO
2004/028803 A1) and the gel spinning process (WO 2010/057982 A1).
Polyolefins can easily be stretched at room temperature; the
stretching speed selected here must be relatively low because of
the exothermicity of stretching. The stretched polyolefins have the
disadvantage that they exhibit very high shrinkage after stretching
when processed at elevated temperatures and therefore first have to
be equilibrated at the desired operating temperature. Stretched
polyolefins moreover have very restricted mechanical properties
which limit their usefulness as reinforcing fibres. Particular
disadvantages are lack of thermal stability and lack of compressive
strength (cold formability).
[0004] Omar (Master's degree thesis: "Processing, morphology and
product parameters of PVDF filaments for biomedical applications",
August 2008, Institut fur Textiltechnik RWTH Aachen, Prof. Dr.
Thomas Gries) discloses stretching procedures applied to PVDF
fibres for the production of yarns and textiles; these were
stretched by a factor of at most 2.5.
[0005] DE 60024882 T2 discloses a two-stage stretching process for
PVDF fibres for the production of fishing lines. In order to
achieve ideal mechanical properties, the fibres are subjected to
controlled shrinkage at a temperature of at least 220.degree. C.
for a few seconds.
[0006] WO 2013/190149 A1 discloses ductile fibres of various
thermoplastics, preferably polypropylene and polyethylene, as a
constituent of what are known as prepregs. These are understood to
be weaves of thermoplastic fibres with brittle fibres, in
particular carbon fibres. These materials are then preferably
pressed or thermoformed in a matrix made of the material of the
ductile fibres. This melts the ductile fibre and improves binding
between matrix and brittle fibre.
[0007] Production of entirely aromatic polyamide fibres, for
example poly(p-phenylene terephthalamide) (PPTA, aramid) with
trademarks: Kevlar.RTM. (trademark of DuPont, USA), Twaron.RTM.
(trademark of Teijin Lim, Japan) is described in U.S. Pat. No.
3,869,430 A.
[0008] EP 0091766 A2 and DE 2304429 A1 describe stretching
procedures for perfluoropolymers. Stretching factors obtained in
these cases are at most 4.5; attempts to achieve greater stretching
lead to fibre breakage. It also appears that the stretching
procedure only improves the mechanical properties of perfluorinated
polymers to a very limited extent: modulus of elasticity after
stretching is at most 1228 MPa.
[0009] For the purposes of this invention, the term "filament"
means fibres, films or ribbons.
[0010] Films in particular are preferably stretched in more than
one direction.
[0011] The term "stretching" means a tensile procedure which is
carried out after extrusion has been concluded through use of
thermal and mechanical energy.
[0012] It was therefore an object of the present invention to
produce stretched filaments made of fluoropolymers, and to provide
a simple, non-hazardous and solvent-free process for the stretching
of fluoropolymers.
[0013] The object was achieved via stretched filaments made of
non-perfluorinated fluoropolymers, where the filaments are cooled
after stretching under full tensile load.
[0014] The present invention provides a process for the production
of stretched filaments comprising at least 80% by weight,
preferably 85% by weight, more preferably 90% by weight, still more
preferably 95% by weight, of fluoropolymers, and in particular
consisting thereof, characterized in that
the filaments have a rectangular cross section where the thickness
is less than the width, where the raw filaments are stretched with
a stretching factor (SF) greater than or equal to 3 at a stretching
temperature between 70.degree. C. and the Vicat temperature, which
is determined in accordance with DIN EN ISO 306:2004-10 B50, where
the filaments are cooled under full tensile load to below
50.degree. C., where no perfluorinated polymers are present.
[0015] The invention further provides stretched filaments produced
by the process of the invention.
[0016] The invention further provides the use of the stretched
filaments of the invention for the production of composites.
[0017] The invention further provides the use of the stretched
filaments of the invention for the production of winding
layers.
[0018] An advantage of the stretched filaments of the invention is
that they exhibit little shrinkage at elevated temperature, i.e.
exhibit almost no relaxation effect.
[0019] It is also advantageous that the stretched filaments of the
invention have high mechanical stability. Mechanical stability is
preferably measured as breaking stress in the direction of
stretching.
[0020] It is also advantageous that the stretched filaments of the
invention have surprising elasticity at relatively high stretching
factors.
[0021] It is also advantageous that the stretched filaments of the
invention have high mechanical stability, and that this is also
true at elevated temperature.
[0022] The stretched filaments of the invention, the composites of
the invention comprising the filaments of the invention, and the
production and use according to the invention are described by way
of example hereinafter, without any intention that the invention be
restricted to these illustrative embodiments. Where ranges, general
formulae, or classes of compound are stated below, these are
intended to comprise not only the corresponding ranges or groups of
compounds explicitly mentioned, but also all subranges and
subgroups of compounds that can be obtained by extracting
individual values (ranges) or compounds. Where documents are cited
for the purposes of the present description, their entire content
is intended to be part of the disclosure content of the present
invention. Where percentage data are provided hereinafter, these
are data in % by weight unless otherwise stated. Percentage data
for compositions are based on the entire composition unless
otherwise stated. Where average values are provided hereinafter,
these are averages by mass (averages by weight) unless otherwise
stated. Where measured values are provided hereinafter, unless
otherwise stated these measured values were determined at a
pressure of 101 325 Pa and at a temperature of 25.degree. C.
[0023] The scope of protection includes finished and packaged forms
that are conventionally used in commerce for the products of the
invention, not only per se but also in possible comminuted forms to
the extent that these are not defined in the claims.
[0024] Fluoropolymers can be selected from polyvinylidene fluoride
(PVDF), ethylene-tetrafluoroethylene copolymer (ETFE),
ethylene-chlorotrifluoroethylene copolymer (E-CTFE),
polychlorotrifluoroethylene (PCTFE),
chlorotrifluoroethylene-perfluoroalkylvinyl
ether-tetrafluoroethylene copolymer (CPT),
tetrafluoroethylene-hexafluoropropene copolymer (FEP) and
tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),
ETFE modified by a tercomponent, for example propene,
hexafluoropropene, vinyl fluoride or vinylidene fluoride (for
example EFEP); moreover also copolymers based on vinylidene
fluoride which comprise up to 40% by weight of other monomers, for
example trifluoroethylene, chlorotrifluoroethylene, ethylene,
propene and hexafluoropropene.
[0025] Fluoropolymers of the filaments of the invention are not
perfluorinated polymers. The fluoropolymers preferably have
hydrogen alongside fluorine as substituents on carbon; more
preferably, the carbon atoms of the backbone, i.e. the carbon atoms
that form the polymer chain, exhibit some extent of hydrogen
substitution. It is still more preferable that there is hydrogen
substitution on at least 5 mol % of the carbon atoms of the
fluoropolymers, preferably at least 10 mol %, 20 mol %, 30 mol % or
40 mol %, and in particular 50 mol %; the corresponding upper
limits are preferably 90 mol %, 80 mol %, 70 mol %, 60 mol % and in
particular 50 mol %. These content data are particularly preferably
based on the carbon atoms of the backbone of the
fluoropolymers.
[0026] It is preferable that the fluoropolymers of the filaments of
the invention exhibit branching only at no more than 25% of the
carbon atoms of the backbone; branching occurs where there are
carbon-carbon bonds between a backbone carbon atom and another
carbon atom. More preferably, the fluoropolymers have branching at
no more than 20%, 15%, 10%, or 5% of carbon atoms of the backbone,
and with particular preference at no carbon atom of the
backbone.
[0027] It is further preferable that the fluoropolymers of the
filaments of the invention have no ether groups.
[0028] Fluoropolymers of the filaments of the invention are
preferably selected from polyvinylidene fluoride (PVDF),
ethylene-tetrafluoroethylene copolymer (ETFE),
ethylene-chlorotrifluoroethylene copolymer (E-CTFE),
polychlorotrifluoroethylene (PCTFE), ETFE modified by a
tercomponent, for example propene, or modified by vinylidene
fluoride; moreover also copolymers based on vinylidene fluoride
which comprise up to 40% by weight of other monomers. PVDF is in
particular preferred.
[0029] It is preferable that the fluoropolymers comprise no
solvents.
[0030] The Vicat temperature of the fluoropolymers of the filaments
of the invention is preferably at least 80.degree. C., more
preferably at least 90.degree. C., still more preferably at least
110.degree. C., particularly preferably at least 125.degree. C. and
with particular preference at least 140.degree. C.
[0031] The Vicat temperature is known to the person skilled in the
art and is preferably determined in accordance with DIN EN ISO
306:2004-10, B50. The required temperature in each case has a
tolerance of plus/minus 5.degree. C.; for the value 140.degree. C.,
therefore, the values 135.degree. C. to 145.degree. C. are
included.
[0032] The width to thickness ratio of the filaments of the
invention is preferably at least 25 to 1, more preferably at least
50 to 1, still more preferably at least 100 to 1, particularly
preferably at least 200 to 1, more particularly preferably at least
300 to 1, with particular preference at least 400 to 1.
[0033] Preference is given to a stretching temperature of from
70.degree. C. up to the Vicat temperature [.degree. C.], more
preferably 85.degree. C. to 5% below Vicat temperature [.degree.
C.] and with particular preference 100.degree. C. to 10% below
Vicat temperature [.degree. C.].
[0034] The filaments of the invention have been produced by
stretching of the raw filaments by a stretching factor (SF) that is
preferably greater than or equal to 3, more preferably greater than
or equal to 5, with particular preference greater than or equal to
10, or greater.
[0035] The person skilled in the art is familiar with determination
of the stretching factor. It is preferably determined by
determining the length of the raw filament before stretching and of
the filaments after stretching. The factor is then calculated by
dividing the lengths after stretching by the lengths before
stretching. The stretching factor is stated as numerical value of 1
or greater, or else as corresponding percentage value in which the
numerical value of 1 then corresponds to 100%.
[0036] It is preferable that, starting from a stretching factor of
3.0, the filaments of the invention have high elasticity; the
elasticity is preferably expressed as modulus of elasticity.
[0037] It is more preferable that, with a stretching factor of 3.0,
the modulus of elasticity of the filaments of the invention has
risen to less than twice the value for the unstretched input
material, preferably less than 1.5 times the said value.
[0038] The rise of the modulus of elasticity starting from a
stretching factor (SF) of 3.0 is still more preferably only up to
150 MPa for each stretching-factor change of 1.0, particularly
preferably up to 120 MPa, with particular preference up to 100
MPa.
[0039] In particular, for a rise of the stretching factor from 3 to
4 the modulus of elasticity rises by at most 150 MPa, by at most
120 MPa and very particularly by at most 100 MPa.
[0040] It is preferable that the filaments of the invention have
been stretched in free space, without contact. The zone in which
the stretching takes place is a zone in which the ambient
atmosphere is heated, therefore by way of example being a type of
tube oven or the space between at least two heated plates.
[0041] The filaments of the invention can be stretched continuously
or batchwise.
[0042] Preference is given to static stretching procedures, i.e.
stretching procedures in which one end of the filament remains
stationary with speeds of 10 mm/min up to 200 mm/min, preferably of
20 mm/min up to 100 mm/min, more preferably 30 mm/min to 80
mm/min.
[0043] Preferred continuous stretching procedures are carried out
in a manner that provides a low transport speed preferably in the
range from 10 mm/min up to 3000 mm/min, preferably from 50 mm/min
up to 2500 mm/min, more preferably 100 mm/min to 2000 mm/min, even
more preferably 500 mm/min to 1500 mm/min. The speed of the
faster-running transport unit is calculated by way of the
stretching factors.
[0044] The filaments of the invention can be stretched by a single
stretching procedure or by a number of successive stretching
procedures. The latter case always requires selection of a
relatively high stretching temperature. A single stretching
procedure is more preferable.
[0045] The filaments of the invention are cooled after the
stretching procedure to below 50.degree. C. This cooling preferably
takes place slowly, preferably for at least 10 seconds, more
preferably for at least 20 seconds, still more preferably for at
least 30 seconds, particularly preferably for at least 45 seconds,
with particular preference for at least 1 minute.
[0046] The stretched filaments of the invention preferably exhibit
only minor shrinkage/relaxation in the direction of tension when
heated to a temperature (relaxation temperature) below the melting
point.
[0047] It is preferable that the relaxation temperature is above
25.degree. C. and below the melting point, preferably below the
stretching temperature.
[0048] Relaxation of the filaments of the invention is preferably
at most 6%, based on the stretched length, preferably at most 5.5%,
more preferably at most 5%, still more preferably at most 4.5%, and
with particular preference at most 4%.
[0049] It is preferable that the relaxation of the filaments of the
invention does not take place under tensile stress.
[0050] It is preferable that the length of the stretched filaments
of the invention is greater than 5 times a dimension situated at
right angles to the length; it is preferable that the filaments are
what is known as continuous filaments. The length of the filaments
is always determined in the direction of tension.
[0051] For the purposes of this invention, the term "filament"
means fibres, films or ribbons.
[0052] Films in particular are preferably stretched in more than
one direction.
[0053] It is preferable that the filaments do not have a round
cross section.
[0054] The individual filaments can be used to manufacture
composites; preferred composites of ribbons are therefore laid
scrims, weaves such as mats, and also mixed forms.
[0055] Laid scrims can consist either of filaments cut-to-size to a
particular length or of continuous filaments in the form of
windings around, for example, tubes.
[0056] Preferred laid scrims made of continuous filaments of the
invention are winding layers around hollow bodies, the filaments
here preferably being ribbons. Winding is preferably unidirectional
or multidirectional. Multidirectional winding layers exhibit an
angle in relation to the direction of tension of the filaments.
This angle is preferably in the range from 5.degree. to
120.degree., more preferably from 30.degree. to 90.degree., with
particular preference 15.degree. to 80.degree.. In the case of
winding layers around tubes, these winding layers exhibit an angle
of inclination in relation to the centre of the tube. It is
preferable that different winding layers exhibit different angles
of inclination. The design of the winding layers around tubes in
relation to the angle of inclination is preferably such that after
one rotation the edges of the layer are flush with, and adjoin, one
another.
[0057] It is preferable that no yarns are produced from the
filaments, where yarns are preferably produced from a plurality of
individual filaments by braiding (e.g. plaits and cords) or by
twisting (e.g. cables); in particular, no yarns are produced from
filaments with round cross section.
EXAMPLES
[0058] Materials:
[0059] PVDF: Solef.RTM. 1006, trademark of Solvay, USA
[0060] PVDF: Solef.RTM. 6008, trademark of Solvay, USA
[0061] FEP: Neoflon.RTM. NP-20, trademark of Daikin Industries,
Japan
[0062] Methods
[0063] DSC:
[0064] Perkin Elmer Diamond, automatic peak recognition and
integration by a method based on DIN EN
[0065] ISO 11357-1: 2010, heating rate 20 K/min.
[0066] Vicat:
[0067] DIN EN ISO 306:2004-10, Method B, 50 N (loading 5 kg).
Example 1a, Production of Specimens
[0068] An extruder (Collin E45M) was used at a temperature of
260.degree. C. to extrude PVDF (Solef 1006), which was calendered
to give a ribbon of thickness 650 .mu.m and width 35 mm and cooled
to 57.degree. C. Take-off speed was 1.4 m/min.
[0069] E 1,* are samples made of PVDF Solef 1006;
[0070] E 2,* are samples made of FEP.
Example 1 b, Production of Specimens
[0071] An extruder (Collin CE20) was used at a temperature of
240.degree. C. to extrude PVDF (Solef 6008), which was calendered
to give a ribbon of thickness 150 .mu.m and width 120 mm and cooled
to 89.degree. C.; take-off speed was 2.1 m/min.
[0072] E 3,* are samples of this Example 1 b.
Example 2, Stretching of Specimens
[0073] Method 1:
[0074] Specimens according to Example 1a were stretched in a
tensile tester (Zwick, Z101-K) at 10 mm/min at 140.degree. C.
Before the tensile load was released, the specimens were cooled to
below 50.degree. C.
[0075] Method 2:
[0076] An endless specimen according to Example 1a was provided on
a reel and stretched on a continuously operating machine (Retech
drawing machine) at a material-feed rate of 4 rpm with a tension
rate of up to 32 rpm to give a stretching factor (SF) of 8. The
stretching temperature was 140.degree. C.
[0077] Method 3:
[0078] Specimens according to Example 1a were stretched in a
tensile tester (Zwick, Z101-K) at 10 mm/min at 100, 120 and
140.degree. C. Before the tensile load was released, the specimens
were cooled to below 50.degree. C. The stretched specimens thus
produced were again clamped into the machine and were again
stretched at 100, 120 and 140.degree. C. at 10 mm/min.
[0079] Table 2 presents the results.
[0080] Method 4:
[0081] An endless specimen according to Example 1 b was provided on
a reel and stretched on a continuously operating machine (Retech
drawing machine) at a material-feed rate of 1.5 m/min and at
variable tension rates to realize various stretching factors (SF).
The stretching temperatures were 120.degree. C.
[0082] Table 3 presents the results.
[0083] Method 5:
[0084] An endless specimen according to Method 4 (stretched with
SF=6) was provided on a reel and stretched on a continuously
operating machine (Retech drawing machine) at a material-feed rate
of 1.5 m/min and at variable tension rates to realize various
stretching factors (SF). The stretching temperatures were
120.degree. C.
[0085] Table 4 presents the results.
Example 3a, Mechanical Tests
[0086] Tensile Tests
[0087] Dumbbell specimens in accordance with DIN 527-2:2012
(specimen type 1BA) were punched out of the stretched (Method 1)
ribbons; the thickness resulted from the stretching test and was
not altered.
[0088] Test equipment from Zwick was used to test tensile strength
at a temperature of 23.degree. C. and relative humidity of 50%.
Test speed=10 mm/min, clamped length=120 mm and measurement length
of incremental gauge=75 mm.
[0089] The results are provided in Table 1, and also in FIGS. 1 and
2.
[0090] The results are the arithmetic average from 3 specimens.
Example 3b, Mechanical Tests
[0091] Tensile Tests
[0092] Tensile strength in accordance with DIN 527-2:2012 was
measured from the stretched (Methods 4 and 5) ribbons; the
thickness resulted from the stretching test and was not
altered.
[0093] Test equipment from Zwick was used to test tensile strength
at a temperature of 23.degree. C. and relative humidity of 50%.
Test speed=60 mm/min, clamped length=100 mm.
[0094] The results are provided in Table 4, and also in FIGS. 3 and
4.
[0095] The results are the arithmetic average from 3 specimens.
TABLE-US-00001 TABLE 1 T = 23.degree. C., results of the tensile
tests according to Example 3a. E 1.0 E 1.1 E 1.2 E 1.3 Stretching
factor 1 1.4 3.0 4.5 Modulus of elasticity [MPa] 2144 2965 3367
3323 Max strength (stress) .sigma..sub.m [MPa] 58.02 173.34 248.60
284.64
TABLE-US-00002 TABLE 2 Results of the stretching tests according to
Example 2, Method 3. Stretching temperature [.degree. C.]
Stretching procedure 100 120 140 Stretching factor during 1st 5.00
5.34 5.12 stretching procedure Stretching factor during 2.03 2.17
2.45 2nd stretching procedure Overall stretching factor 10.15 11.59
12.54
TABLE-US-00003 TABLE 3 Results of the stretching tests according to
Example 2, Method 4. Speed of stretching reel Stretching Speed of
1st reel [m/min] [m/min] factor 1.5 9.0 6.0 1.5 10.6 7.1 1.5 12.0
8.0 1.5 13.6 9.0 1.5 15.2 10.1
TABLE-US-00004 TABLE 5 Results of the stretching tests according to
Example 2, Method 5. Stretching procedure E 3.1 E 3.2 E 3.3
Stretching factor during 1st 6 6 6 stretching procedure Stretching
factor during 1.21 1.32 2.15 2nd stretching procedure Overall
stretching factor 7.30 7.96 8.63
TABLE-US-00005 TABLE 4 Results of the tensile tests according to
Example 3b. E 3.4 E 3.5 E 3.6 E 3.7 Stretching factor 1 6 7.3 8.6
Modulus of elasticity [MPa] 1200 2160 2390 2670 Max strength
(stress) .sigma..sub.m [MPa] 49.6 301 350 370
* * * * *