Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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-- 1 --
FI~E RETA~DA~r POLYKETONE POL ~ ER BLEND
~.
This invention relates to polyketone polymers. More
particularly, the invention relates to a reinforced flame
retardant polyketone polymer blend.
Polymers of carbon monoxide and ethylenically
unsaturated compounds which are commonly called poly-
ketones or polyketone polymers have been known and are
available for some time.
High molecular weight linear alternating polyketones
are of considerable interest because they exhibit a good
overall set of physical properties. This class of
polymers is disclosed in numerous patent documents, for
example in US-A-4880865 and US-A-4818811. The linear
alternating polyketones have established utility as
premium thermoplastics in the production of shaped
articles such as containers for food and drink and parts
for the automotive industry. These articles can be
produced by processing the polyketone polymer according
to well known methods. Certain mechanical properties of
the polyketones can be improved through blending with
e.g. reinforcements or other polymers, or by the addition
of additives-to the material. For example, the,stiffness
and heat resistance of poly~etones are improved by the
addition of a reinforcement to the material, such as
glass fibres.
The rise of the electronics industry has placed a
premium on the development of polymers which can be used
to support electrical circuitry. The polymers so used
should not be unfavourably affected by their proximity to
changing electrical fields and currents nor should their
intrinsic properties unfavourably affect the circuitry
about which the polymer is exposed. This can be best
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expressed by considering a simple electrical circuit such
as the emplacement of two electrical conductors supported
on a polymer support which maintains them at some finite ~
separation. A potential difference is found between the
two conductors. In such a case, among other desirable
features of the material, the polymer must physically
retain the separation of the two conductors to avoid a
short circuit.
Exposing the polymer to a non-sterile environment
subjects it to the deposition of any number of materials
on its surface. As these materials become affixed to the
surface of the polymer they cause a decrease in surface
resistance. This enables a current to flow and thereby
generates heat at the point about the deposition. Some
areas may have considerably more deposits than others
which can lead to voltage gradients which ultimately
results in surface discharges. Such surface discharges
produce very high temperatures at the point at which they
occur and thereby erode the surface. This erosive action
is called tracking.
One method for comparing the susceptibility of
materials to tracking is by their Comparative Tracking
Index (CTI). The CTI of a material is defined as the
numerical value of the voltage which will cause failure
by tracking when the number of drops of cont~m;n~nt
required to cause failure is equal to 50. For many of
the electrical and electronic applications of polymers it
is desirable to have a CTI greater than 350 V, in
particular greater than 400 V. The maximum which can be
measured is a CTI of 600 v.
Flammability is another important consideration in
applying particular polymers in electrical or electronic
uses. Many polymers and polymer blends must be modified
by the addition of a flame retardant to attain the
desired level of resistance to flammability. For
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example, US-A-4761449 proposes the addition of an
alkaline earth metal carbonate to polyketone to form a
flame retardant blend. US-A-4885328 proposes the use of
magnesium hydroxide as the flame retardant for poly-
ketones. US-A-4921897 proposes the addition of zinc
borate or barium borate as flame retardants for poly-
ketones.
Unfortunately, a combination of additives to a
polymer does not necessarily uni~ormly improve the
properties of the polymer. For example, neat poly-
ketones, reinforced polyketones and flame retarded
polyketones possess CTIs of 600V. This is generally
considered to be superior performance. However, when
polyketones, reinforcement, and flame retardant are
combined the material exhibits an unsatisfactorily low
CTI, ~or example as low as 250V. The addition of other
additives such as pigments also brings some uncertainty
into the overall set o~ physical properties that the
polymer will ultimately display.
Reinforced ~1ame retarded polyketones having CTIs in
the range found use~ul ~or electrical end uses would
greatly contribute to the range of applications for such
polymer blends. Such polyketone blends would be
especially beneficial if they could obviate or reduce the
need for one or more other additives such as pigments.
Such materials are useful in electrical connectors and
switch gears, as supporting materials and fasteners for
electrical circuitry, and as insulation for wires among
other applications.
It has now unexpectedly been found that the CTI of
reinforced flame retardant polyketone polymers can be
improved by the addition of a suitable compound.
Unexpectedly, useful CTI improving compounds for use in
the invention are zinc compounds, which are known per se
to act as flame retardant in polyketones, and that other
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CTI improving compounds are silicon oils. The zinc
compounds are also effective pigments for the reinforced
flame retardant polyketone polymers.
Accordingly, the present invention relates to a
reinforced flame retardant polyketone polymer blend
comprising a polyketone polymer, a reinforcement, a flame
retardant other than a zinc compound, and a comparative
tracking index (CTI) improving compound selected from
zinc compounds and silicon oils.
The invention relates also to a method for improving
the CTI of a reinforced flame retardant polyketone,
comprising a~m;x;ng the polyketone with a reinforcement,
a flame retardant other than a zinc compound, and a CTI
improving compound selected from zinc compounds and
silicon oils.
The present invention also relates to a reinforced
flame retardant polyketone polymer blend having a CTI
greater than 375 V, as measured by ASTM D 3638-93,
preferably greater than 400 V.
The terminology "reinforced flame retardant blend" is
used to indicate that the blend comprises a reinforcement
and a flame retardant.
The blends according to the invention have in
particular a flame retardancy of at least V-1, more in
particular at least V-O, as measured by the UL 94
Vertical Flammability Test, using 1.6 mm specimens. For
most applications it is sufficient that the blends have a
flame retardancy not higher than V-O, measured by using
O.8 mm specimens. The UL 9~ Vertical Flammability Test
is deemed to be the test in its version valid on
1 January 1996.
The blends of this invention may incorporate common -
polymer additives. For instance, extenders, lubricants,
pigments, plasticizers and other polymeric materials can
be added to the compositions to improve or otherwise
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alter the properties of the composition. In general, the
practice of this invention involves suitably contacting
sufficient quantities of the useful material to form the
inventive blend.
The polyketones for use in this invention, suitably
as the major component, are typically linear alternating
copolymers of carbon monoxide and at least one ethyleni-
cally unsaturated compound. Thus, the polyketone polymers
are typically o~ a linear alternating structure which
means that they contain typically one molecule o~ carbon
monoxide for each molecule o~ the ethylenically
unsaturated compound. Ethylenically unsaturated
compounds comprise suitably up to 20 carbon atoms and
include compounds which consist exclusively of carbon and
hydrogen and compounds which in addition comprise hetero
atoms, such as unsaturated esters, ethers and amides.
Unsaturated hydrocarbons are pre~erred. Examples of
suitable ethylenically unsaturated compounds are ali-
phatic a-olefins, such as ethene, propene, butene-1 and
hexene-1, cyclic olefins such as cyclopentene, aromatic
compounds, such as styrene and a-methylstyrene and vinyl
esters, such as vinyl acetate and vinyl propionate. The
preferred polyketone polymers are linear alternating
polymers of carbon monoxide and ethene or linear
alternating polymers of carbon monoxide, ethene and
another ethylenically unsaturated compound of at least
3 carbon atoms, particularly an a-olefin such as propene,
butene-1 or hexene-1.
When the preferred polyketone polymers of carbon
monoxide, ethene and another ethylenically unsaturated
compound are employed, there will be within the polymer
- typically at least 2 units incorporating a moiety of
ethene for each unit incorporating a moiety of the other
ethylenically unsaturated compound(s). Preferably, there
will be from 10 units to 100 units incorporating a moiety
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-- 6
of ethene for each unit incorporating a moiety of the
other ethylenically unsaturated compound(s). The polymer
chain of preferred polyketone polymers is therefore
represented by the repeating formula
[ CO~CH2 -CH2 ) ] X--[CO~G) ~y
where G is the moiety of the ethylenically unsaturated
compound of at least 3 carbon atoms polymerized through
the ethylenic unsaturation and the ratio of y:x is
typically no more than 0.5. When linear alternating
polymers of carbon monoxide and ethene are employed in
the compositions of the invention, there will be no
second ethylenically unsaturated compound present and the
polymers are represented by the above formula wherein y
i8 zero. When y is other than zero the --CO~CH2--H2~ units
and the -CO~G~ units are found randomly throughout the
polymer chain, and preferred ratios of y:x are from 0.01
to 0.1. The precise nature of the end groups does not
appear to influence the properties o~ the polymer to any
considerable extent so that the polymers are fairly
represented by the ~ormula ~or the polymer c.h~; n.~ as
depicted above.
The polyketone polymers of number average molecular
weight ~rom 1000 to 200,000, particularly those of number
average molecular weight from 20,000 to 90,000 as
determined by gel permeation chromatography are of
particular interest. The physical properties of the
polymer will depend in part upon the molecular weight,
whether the polymer is based on a single or on a
plurality of ethylenically unsaturated compounds and on
the nature and the proportion of the ethylenically
unsaturated compounds. Typical melting points ~or the
polymers are from 175 ~C to 300 ~C, more typically from
210 ~C to 270 ~C, as determined by differential scanning
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-- 7
calorimetry. The polymers have typically a limiting
viscosity number (LVN), measured in m-cresol at 60 ~C in
a standard capillary viscosity measuring device, from
0.5 dl/g to 10 dl/g, more typically from 0.8 dl/g to
4 dl/g.
Preferred methods for the production of the
polyketone polymers are known from US-A-4808699 and
US-A-4868282. US-A-4808699 teaches the production of
polyketone polymers by contacting ethene and carbon
monoxide in the presence of a catalyst comprising a
Group VII metal compound, an anion of a nonhydrohalogenic
acid with a pKa less than 6 and a bidentate phosphorus,
arsenic or antimony ligand. US-A-4868282 teaches the
production of polyketone polymers by contacting carbon
monoxide and ethene in the presence of one or more
hydrocarbons having an ethylenically lmsaturated group
with a similar catalyst.
The blends of this invention incorporate a
reinforcement, typically in a minor quantity. Suitable
reinforcements are inorganic materials and include
particulate fillers, such as mica and talc, and fibrous
reinforcement, such as glass fibres and wollastonite.
Glass fibre reinforcement is preferred.
The term "glass" is employed within its conventional
meaning to indicate that class of complex metal silicates
which are commonly referred to as glasses. Although the
addition of rare earth metal oxides or transition metal
oxides to metal silicates on occasion will produce a
glass of exotic properties, the glass from which the
glass fibre of the invention is produced is typically the
more common alkali metal silicate glass, particularly a
borosilicate glass.
Fibres produced of such glass are conventional and
are commercially available from a large number of
sources. The fibres are useful as reinforcements for
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polymeric products and are commercially used as such.
Short, chopped glass fibres with a circular cross section
are preferred. For example, fibres ranging in diameter
from 5.1 to 20.3 ~m (2x10-4 to 8x10-4 inch) and lengths
of at least 1.5 mm, especially from 2.54-12.7 mm (0.1 to
0.5 inch), can be used with good results. The glass
fibres are preferably obtained from the manufacturer with
a surface treatment compatible with the polyketone
polymer, such as a polyurethane sizing.
The reinforcement, in particular glass fibre, is
present in the blends of this invention in quantities
comprising between 5 and 40 wt~, based on total weight of
the blend. It is preferred that the range be between 7
and 30 wt~, between 11 and 25 wt~ being most preferred.
Various flame retardants may be used in this
invention, typically in a minor quantity. Examples are
halogenated flame retardants, such as decabromodiphenyl-
oxide and bis(1,2,3,4,7,7-hexachloro-2-norborneno)-
[a,e]-cyclooctane, antimony trioxide, alkaline earth
metal hydroxides and alkaline earth metal carbonates, cf.
for example US-A-4921897, US-A-4885328 and US-A-4761449.
Some of these flame retardants may be combined to form
synergistic mixtures, for example halogenated flame
retardants with antimony trioxide.
By alkaline earth metal hydroxide or carbonate, which
represents a preferred class of flame retardants, is
meant a hydroxide or carbonate of a metal of group IIA of
the Periodic Table of Elements. While hydroxides of
beryllium, magnesium, calcium, strontium, and barium are
suitable, the preferred alkaline earth metal hydroxide
component is magnesium hydroxide. Most preferred is
magnesium hydroxide. Preferred alkaline earth metal
carbonates are calcium carbonate and partially hydrated
magnesium calcium carbonate. Most preferred is partially
hydrated magnesium calcium carbonate.
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The quantity of the flame retardant compound is
suitably selected between 10 and 70 ~w, more suitably
between 20 and 55 ~w, in particular between 25 and 40 ~w,
based on the weight of the blend.
The CTI improving compound may be selected from zinc
compounds and silicon oils.
The zinc compound is preferably a compound of zinc
borate or zinc oxide. Zinc borate i8 most preferred.
The typical composition of zinc borate is pZnO qB2O3,
wherein p/q is the molar ratio of ZnO to B2O3, and is
usually available in the hydrated form. A preferred zinc
borate has the formula 2ZnO-3B203 3-4H20, in particular
2ZnO 3B203 3.3-3.7H20. A preferred zinc borate
preparation is commercially available 2ZnO 3B2O3 3.5H2O.
As set out hereinafter, it may be advantageous to employ
a substantially anhydrous zinc borate. The term
"substantially anhydrous" expresses that the quantity of
water present therein calculated as molar ratio of H2O to
ZnO is typically less than 1, more typically less than
0.5. Very suitable anhydrous zinc borate is of the
formula 2ZnO~3B2O3.
Useful silicon oils can be described as comprising
chains of polydihydrocarbylsiloxanes, of which the
various hydrocarbyl groups may be the same or different.
The chains are typically linear. The hydrocarbyl groups
have in particular up to 8 carbon atoms. They are
preferably alkyl groups, in particular methyl groups. It
may be advantageous to employ a combination of methyl or
ethyl groups, in particular methyl groups, with aryl
groups, such as phenyl groups, or with alkyl groups
having 3 or more carbon atoms. The hydrocarbyl groups
may carry halogen atoms. Examples are polydimethyl-
siloxane, poly[dimethylsiloxane-co-(methyl)(phenyl)-
- siloxane)], typically containing 85-95 ~-mole (CH3)2SiO
repeating units and 5-15 ~-mole (CH3)(C6H5)SiO repeating
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-- 10
units, poly[(methyl)(3,3,3-trifluoropropyl)siloxane)],
and poly[dimethylsiloxane-co-(methyl)(3,3,3-trifluoro-
propyl)siloxane)], typically containing up to 10 ~-mole
(CH3)2SiO repeating units and at least 90 ~-mole
(CH3)(CF3-CH2-CH2)Sio repeating units. Polydimethyl-
siloxane i8 preferred. Very usefully, the silicon oil,
in particular polydimethylsiloxane, has a viscosity at
25 ~C in the range of 1,000-300,000 mm2/s, preferably in
the range of 5,000-100,000 mm2/s.
Silicon oils or other components of the blends of
this invention may be applied in the form of a
masterbatch. The masterbatch may be based on a
polyketone polymer but it is also possible to have the
masterbatch based on another polymer, such as a polyamide
or polyethene. The quantity of the silicon oil or such
another component in the masterbatch is frequently in the
range of 10-90 %w, based on the weight of the master-
batch, typically in the range of 30-70 ~w on the same
basis.
When a CTI improving compound is combined with a
flame retardant, in particular an alkaline earth metal
hydroxide, it may occur that there is a small decrease in
the level of the flame retardancy of the blend. This is
more in particular the case when a hydrated zinc borate
is used as the CTI improving compound. It has
unexpectedly been found that the decrease in flame
retardancy is smaller or not noticeable at all when as
the CTI improving compound a silicon oil or a sub-
stantially anhydrous zinc borate is used. Therefore
there is a preference for using a silicon oil or a
substantially anhydrous zinc borate as the CTI improving
compound.
Blends comprising a polyketone polymer and a
substantially anhydrous zinc borate are novel.
Therefore, the present invention also relates to such
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blends per se. Such blends can be used as a starting
material for the production of the reinforced flame
retardant blends according to this invention.
The quantity of the CTI improving compound present in
the blends of this invention may be selected within wide
ranges. The CTI improving compound is frequently applied
in a minor quantity. Typically the quantity of the CTI
improving compound is selected between 0.2 and 30 ~w,
based on the weight of the blend. When the CTI improving
compound is a zinc compound, there is particular
preference to have it present in a quantity between 3 and
15 ~w, relative to the weight of the blend, however,
substantially anhydrous zinc borate is preferably used in
a quantity of between 0.2 and 10 ~w, more preferably
between 0.5 and 5 ~w. When the CTI improving compound is
a silicone oil, there is preference to have it present in
a quantity between 0.2 and 5 ~w, in particular between
0.5 and 3 ~w, relative to the weight of the blend.
The blends of this invention are produced by mixing
the various materials with the polyketone polymer. The
method by which this achieved is not critical to this
invention. Good dispersion of the flame retardant
generally contributes to good flame retardancy and CTI
performance. In one blending procedure, the components
are dry blended in particulate form and converted to a
substantially uniform composition, e.g., by extrusion.
Alternatively, the polyketone polymer is heated until
molten and the other components are mixed throughout the
polymer by use of, e.g., a high-shear mixer or extruder.
Reinforced flame retardant polyketone polymer blends
have frequently a pronounced colour. It has also been
found that the use of a zinc compound in the present
blends provides a thorough and even light colour which is
highly desired for some applications. Thus, for certain
uses this blend eliminates the need for additional
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pigment. Additionally, due to the light colour of the
blend, a broader range of pigmented colours is achievable
with these blends.
The inventive blends can be processed by conventional
methods such as extrusion and injection moulding into
various articles of manufacture such as electrical
connectors and switch gears, as supporting materials and
fasteners for electrical circuitry, and as insulation for
wires among other applications.
The invention is further illustrated by the following
examples.
Ex~mple 1 (Po1yketone Form~t;on)
A linear terpolymer of carbon monoxide, ethylene, and
propylene was produced in the presence of a catalyst
composition formed from palladium acetate, the anion of
trifluoroacetic acid and l,3-bis(diphenylphosphino)-
propane. The melting point of the terpolymer was 220 ~C
and it had a limiting viscosity number (LVN) of 1.1
measured at 60 ~C in m-cresol.
~x~mple 2
Blends were prepared of the terpolymer of Example 1,
"OCF 408BC" (trademark) chopped glass commercially
available from Owens-Corning, Inc, "MAGNIFIN H10"
(trademark) magnesium hydroxide from Martinswerk GmbH,
"FIREBRAKE ZB" (trademark) zinc borate
(2ZnO 3B2O3~3.5H20) from US Borax, Inc., and "MYVAPLEX
600" (trademark) glycerol monostearate processing aid
commercially available from Eastman Chemical Co.
The blends were prepared as shown in Table 1 by
blending on a 25 mm twin screw extruder operating at a
melt processing temperature of between about 250 and
270 ~C. Sample A is comparative (not according to this
invention).
The blends were injection moulded into 3.2 mm
(1/8 in) tensile and flexural bars in an injection
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moulding machine. Extruded strand was used for the
assessment of flame retardancy in terms of limiting
oxygen index (LOI).
~ 1e 3 (CTI)
The CTI of each blend of example 2 was measured
according to ASTM D 3638-93. CTI values are reported in
Table 1 below.
This example illustrates the substantial improvement
in the CTI o~ blends made according to this invention
(having both a zinc borate and alkaline earth metal
hydroxide or carbonate) relative to blends without the
zinc borate.
F.x~m~le 4 (Fl~me Test;ng)
Standard test method ASTM D 2863-77 was used to
evaluate the burning behaviour o~ the blends of
example 2. This test measures the minimum concentration
of oxygen in an oxygen-nitrogen atmosphere that is
necessary to initiate and support a flame for 180 seconds
on a test specimen. The result of the test is expressed
as the percentage of oxygen in the oxygen-nitrogen
atmosphere and is called the Limiting Oxygen Index (LOI)
of the composition. LOIs are reported in Table 1 below.
Each of the blends is seen to display good flame
retardancy, as evidenced by LOI > 28~.
F.x~m,pl e 5 (phys;c~1 Test;ng)
Impact, flexural, and tensile properties of the
blends of example 2 are shown below in Table 2.
This example shows that the advantages of the
invention were achieved without signi~icant loss of
mechanical properties.
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- 14 -
Table 1. Flammability and Tracking Resistance
Sample* Concentration Flame LOI CTI
Zinc Borate (~wt) Retardant** (~ 02) (V)
A 0 H10 ~40 375
B 4 H10 35 575
C 7 H10 34 ~600
D 10 H10 35 ~600
*All samples contain:
15 wt~ "OCF 408BC" chopped glass fibres
25 wt~ magnesium hydroxide
O.5 wt~ "MYVAPhEX 600" glycerol monostearate
1 wt~ tricalcium phosphate as a melt stabilizer
**H10 = "MAGNIFIN H10" magnesium hydroxide
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W O 97/14743 PCT/EP96/04513
NO 1 Q N ~ N
H J ~
r~ ~ _ _ _ _
a ~ 4~
r C) _
O
Z; H 1
,~ D~ . . .
J P, In ~D I
~ ---- _ _
X V
o
~ O ~1
~1 UlLt) O O 1~')
rL ~ t~ ~ I
C ~
V d~ Ln m In
U o U~ o o
,~ ~ 0 ~ a~
~ ~ _ _ _ _ _
~ d~ O ~ 0
a c
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0\o ~
~Q ~ ~ ~
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'L V
- -( 11~
N lV
m v ~
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- 16 -
~mple 6
A linear terpolymer of carbon monoxide, ethene and
propene was produced by polymerizing the monomers in the
presence of a catalyst formed from palladium acetate, the
anion of trifluoroacetic acid and 1,3-bis[bis(2-methoxy-
phenyl)phosphino]propane. The melting point of the
polymer was 220 ~C and the LVN was 1.1 dl/g, as measured
in m-cresol at 60 ~C.
Ex~mrles 7-10 (Example 7 for comparison)
Blends were prepared of the terpolymer of Example 6
using as the blend components "OCF 429 YZ" chopped glass
commercially available from Owens-Corning, Inc,
"MAGNIFIN H5" (trademark) magnesium hydroxide from
Martinswerk GmbH, zinc borate (2ZnO 3B2O3 3.5H2O)
(FIREBRAKE 290 (trademark), ex Borax Consolidated Ltd.)
and polydimethylsiloxane (MB 50-011 silicone oil
masterbatch (50 ~w with 50 ~w polyamide-6), ex Dow
Corning). The blends, shown in Table 3, were prepared by
blending in a twin screw extruder operating at a melt
temperature of about 250 ~C. CTI values were determined
using ASTM D 3638-93 and the flame retardancy was tested
by the UL 94 Vertical Flammability Test (1.6 mm
specimens). The test results were as indicated in
Table 3.
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- 17 -
T~hle 3
Example 7 a) 8 9 10
Composition (%w):
Polymer 60 58 5558
Glass fibre 15 15 1515
Magnesium hydroxide 25 2525 25
Zinc borate - 2 5
Polysiloxane - - -1 b
Properties:
UL 94 test c) V-0 V-1 V-1 V-o
CTI (V) 225 300 500425
a) for comparison
b) i.e. 2 ~w masterbatch
c) at 1.6 mm
f ~ 3
