Note: Descriptions are shown in the official language in which they were submitted.
~LZ69~)
This invention relates to a new process for preparing a medium
or low density ethylene copolymer by a vapor phase polymerization using a
Ziegler catalyst of high activity.
Polyethylenes prepared by polymerization using a catalyst con-
sisting of a transition metal compound and an organometallic compound are
generally prepared by the slurry polymerization process, and the poly-
ethylenes usually produced are only those having a density not lower than
0.945. Such value is considered to be the limit in order to prevent poly-
mer deposition or fouling on the inner wall or stirrer in the interior of
a reactor at the time of polymeri~ation.
Medium or low density polyethylenes having a density below
0.945 g/cm3 are usually prepared by the so-called high pressure process
u.sing a radical catalyst. Quite recently, however, a high-temperature
sollltion polymerizatLon process using a Ziegler catalyst has also been
tried.
Low density polyethylenes prepared by the high pressure process
are advantageous in that they are superior in transparency and flexibility
to high density polyethylenes. At the same time, however, they are dis-
advantageous in that the melting point is low and films formed therefrom
are low in stiffness.
Also, polyethylenes prcparcd by the higll-tclnpcrat~re solutLon
polymerization process hnve a poor trnnHp.lrency and fLimls for[ned therefrom
give a sticky impression.
Regarding the production method, the high pressure process
requires a very lligh pressure, thus causing the investment in production
facilities to become incrcased, and also requires high power consumption
and other operation costs. The hlgh-temperature solution polymerization
process is also disadvantageous in that the resulting polyethylene must be
handled as a solution, thus requiring operation at a relatively low concen-
tration, resulting in the productivity becoming inferior and the production
-1-
.
~269~)0
of polyethylenes of a high grade in molecular weight becoming virtually
impossible. Furthermore, the polymers prepared according to the high-
temperature solution polymerization process contain a large amount of wax
because of a high temperature polymerization, so that it is necessary to
provide means for the separation thereof. In the solution polymerization
at a high temperature, moreover, side reactions, e.g., the hydrogenation
and dimerization of ethylene, briskly occur, thus requiring an increased
unit of ethylene and that of hydrogen.
In the production of polyolefins, copolymerizing ethylene with
other monomer has heretofore been known as one method of lowering the
density of polyethylene. However, if a medium or low density polyethylene
is to be prepared by the copolymerization of ethylene and other comonomer
according to a known method, the other comonomer is usually required in a
large exccss amount, and this fact itself is very disadvantageous when
viewed from the standpoint of the process. The copolymeriæation according
to the slurry polymerization process involves additional disadvantages,
i.e., the by-production of a low grade polymer or a solvent~soluble
polymer, and the polymerization product takes in solvent and becomes milky
or mushy, which Dot only makes the reactor operation and slurry transport
difficult, but also results in the separation of solvent from the polymer
being no longer easy. Furthermore, adl)esLon of copolymcr to the reactor
inside occurs due to Lts foullrlg~ and the result-Lng deterioration ln heat
transfer characteriE,tic causcs the polymerization temperature to become
uncontrollable.
In recent years it has been found that if a transition metal is
attaclled to a magnesium-containing solid carrier, e.g., MgO, Mg(OH)2,
MgC12, MgC03 and Mg(OH)Cl, and then combined with an organometa]lic com-
pound, the resulting catalyst system can serve as a catalyst of extremely
high activity in olefin polymerization. It is also known that the reaction
product of an organomagnesium compound, e.g. RMgX, R~Mg and RMg(OR), and a
~z~
transition metal compound, can serve as a high activity catalyst for
olefin polymerization (see, for example, Japanese Patent Publication No.
12105/64, Belgian Patent No. 742,112, Japanese Patent Publications Nos.
13050/68 and 9548/70).
However, even if such high activity catalysts with carrier are
used in the slurry polymerization or the high-temperature solution poly-
merization with a view to preparing medium or low density polyethylenes,
the foregoing drawbacks heretofore have not been completely eliminated.
The present invention has been devised after comprehensive
studies concerning the foregoing technical problems were carried out.
According, therefore, to a broad aspect of this invention, it has been
found that a vapor phase polymerization reaction can be carried out in an
cxtremely stable manner and the catalyst removing step can be eliminated,
so it is possible to provide a vapor phase polymerization process for
ethylene which process as whole is very simple. Surprisingly, moreover, it
has been found that the process of aspects of this invention can very easily
provide a medium or low density ethylene polymer which has excellent trans-
parency and melts higher and is stronger than conventional low density poly-
ethylenes prepared according to the high pressure process.
In more particular terms, by a broad nspect of thl~ Lnvention,
a process has been provided for preparlng an ethylenc-propylene copolymer
having a melt index ranging from 0.01 to 10 and a derlsity ranging from
0.910 to 0.945, which comprises contacting a mixture of ethylene and 6 to
100 mol% thereof of propylene, in the vapor phase condition, with a cata-
lyst consistlng of a solid substance and an organoaluminum compound, the
solid substance containlng a magnesium-containing inorganic solid compound
and at least one of a titanium compou[ld and a vanadium conpound, whereby
ethylene and propylene are allowed to copolymerize.
By one variant, the at least one of a titanium compound and
vanadium compound is a halide, alkoxyhalide, oxide or halogenated oxide of
9~
at least one of titanium and vanadium.
By another variant, the at least one of a titanium compound
and vanadium compound is used as the addition product with an organocar-
boxylic acid ester.
By yet another variant, the magnesium-containing inorganic solid
compound is selected from the group consisting of metallic magnesium)
magnesium hydroxide, magnesium carbonate, magnesium oxide and magnesium
chloride.
By still another variant, the magnesium-containing inorganic
solid compound is selected from the group consisting of double salts,
double oxides, carbonates, chlorides and hydroxides containing a magnesium
atom and a metal selected from the group consisting of silicon, aluminum
und calcium.
By a still furtller variant, the magnesium-containing inorganic
solid compound is further treated or reacted with an oxygen-containing
compound, a sulfur-containing compound, a hydrocarbon or a halogen-
containing substance.
By a still further variant, the magnesium-containing inorganic
solid compound is contacted with an organocarboxylic acid ester before use.
By yet another variant, the organoalunlLnum conlpolmd is used as
the addition product with an orKanocarboxyllc acid ester.
By yet a further variant, the catalyst is prepared in the
presence of an organocarboxylic acid ester.
By another variant, the organocarboxylic acid ester is selected
from the group consisting of alkylestérs of benzoic acid, anisic acid and
toluic acid.
By a further variant, the polymerization is carried out at a
temperature in the range of from 20 to 110C. and at a pressure in the
range of from atmospheric to 70 kg/cm G.
By yet a further variant, the copolymerization is carried out in
~Z69~
the presence of hydrogen.
By another variant, before initiating the copolymerization, the
catalyst system is contacted with an o~-olefin having 3 to 12 carbon atoms
for 1 minute to 24 hours at a temperature in the range of from 0 to 200C.
and at a pressure in the range of from -1 to 100 kg/cm2-G.
It has now become clear that if a vapor phase polymerization
reaction is carried out according to the process of aspects of this inven-
tion using ethylene and propylene in a quantitative ratio within the range
specified herein and also using a catalyst consisting of a solid substance
and an organoaluminum compound, the solid substance containing a magnesium-
containing inorganic solid compound and at least one of a titanium compound
and a vanadium compound, such polymerization can be perfonned in extremely
high activity and extremely stably with reduced production of coarse or
ultra-fine particles and improved particle properties, and also with
minimized adhesion to the reactor and conglomeration of polymer partic]es.
It is therefore quite unexpected and surprislng that, according to the
process of aspects of this invention, not only can a vapor phase polymeriza-
tion reaction be carried out extremely smoothly, but also medium or low
density ethylene copolymers can be obtained easily.
The copo1~ymerization reaction of aspects of tlrls invention can
be performed at a relatlvely low telnpcrat-lre caHI,Iy to prcpare medium or
low density ethylene copolymers, so that the adhesion to reactor or con-
glomeration of product is not significantly observed. I'his point is
another advantage of aspects of this invention.
The process of aspects of this invention also enables the easy
obtaining of a medium or low density ethylene copolymer having a high melt
index. '~lis is a further advantage of aspects of this invention.
Thanks to these advantages, the copolymer as set forth herein
can be obtained efficiently by vapor phase polymerization.
l'he propylene polymerized with ethylene in the process of aspects
31~2~
of this invention adjusts the density and molecular weight of the resul-
ting copolymer,and the copolymer obtained is superior in transparency and
elasticity. It also exhibits a very high resistance to impact and to
environmental stress cracking. Consequently, the copolymer produced
according to the process of aspects of this invention can be Eormed into
films, sheets, hollow containers, insulation for electric wires and
various other products by means of known methods, e.g., extrusion molding,
blow molding, injection molding, press forming and vacuum forming, and
thus can be used in various applications. Particularly in the field of
films, the copolymer produced according to the process of aspects of this
invention exhibits its features because of excellent transparency, anti-
blocking property, heat sealing property and flexibility. That is, it is
possible to attain an equal or even superior transparency to that of a
high pressure process film, and the strength which is a specially important
physical property required of a film is much higher than that of a high
pressure process polyethylene. Besides, a large elongation permits forming
of an extremely thin film.
Although the density of the copolymer produced according to the
process of aspects of this invention is medium or low, the crystallinity
is relatively high and the heat resistance is good, providing nn unsticky
film of high transparency, for whicll re~son the copolymer In qucst-Lon is
especially suitable for use as a film for packing or agriculatural use. It
is also suited to blow molding because of high transyarency, stiffness and
resistance to environmental stress cracking.
The catalyst system used in the process of aspects of this
invention consists of the combination of a .solid substance and an organo-
aluminum compound, the solid substance containing a magnesium-containing
inorganic solid compound and at least one of a titanium compound and a
vanadium compound. The solid substance just referred to above is obtained
by attaching at least one of a titanium compound and a vanadium compound
-- 6 --
9~0
to an inorganic solid carrier typical of which are metallic magnesium,
magnesium hydroxide, magnesium carbonate, magnesium oxide and magnesium
chloride; double salts, double oxides, carbonates, chlorides and hydrox-
ides containing a metal selected from silicon, aluminum and calcium, and
magnesium atoms; further, these inorganic solid carriers treated or
reacted with an oxygen-containing compound, a sulfur-containing compound,
a hydrocarbon or a halogen-containing substance.
As the titanium compound and the vanadium compound referred to
herein, halides, alkoxyhalides, oxides and halogenated oxides of titanium
and vanadium may be used. Examples are tetravelent titanium compounds,
e.g., titanium tetrachloride, titanium tetrabromide, titanium tetraiodide,
monoethoxytrichlorotitanium, diethoxydichlorotitanium, triethoxymonochloro-
titanlum, tetraethoxytitanium, monolsopropoxytrichlorotitanium, diisoprop-
oxydlchlorotLtanlum and tetraisopropoxytltanium; various titanium tri-
halides obtained by reducing titanium tetrahalides with hydrogen, aluminum,
titanium or an organometallic compound; tetravalent vanadium compounds,
e.g., vanadium tetrachloride; pentavalent vanadium compounds, e.g., vana-
dium oxytrichloride and orthoalkylvanadate; and trivalent vanadium com-
pounds, e.g., vanadium trichloride and vanadium triethoxide.
Among the above-exemplified titanlum compolmds and vanadium com-
pounds, tetravalent titanium compounds are JpecLally preL~rred.
The catalyst used ln the process of aspects of thls invention
consists of the comblnatlon of a solld substance, whlch is obtained by
attaching at least one of a titanium compound and a vanadium compound to
the foregoing solid carrier, and to an organoaluminum compound.
By way o illustrating preferred catalyst systems, mentlon may
be made of the following solid substances (tlle R ln the followlng formulae
represents an organlc radical and X represents halogen~ combined with an
organoaluminum compounds: MgO-RX-TlCl~ system (see Japanese Patent Publi-
cation No. 3514/76), Mg-SIC14-TiC14 system (see Japanese Patent Publication
~ ~3LZ~9~
No. 2386~/75), MgC12-Al(OR)3=TiCl4 system (see Japanese Patent Publication
Nos. 152/76 and 15111/77), M~cl2-sicl4-RoH-Ticl4 syste (see Japanese Patent
Laying ~pen Print No. 106581~74), Mg(OOCR)2-Al(OR)3-TiC14 system (see
Japanese Patent Publication ho. 11710/77), Mg-POC13-TiC14 system (see
Japanese Patent Publication ~o. 153/76), MgC12-AlOCl-TiC14 system (see
Japanese Patent Laying Open llrint No. 133386/76).
In these catalyst ~ystems, at least one of a titanium compound
and a vanadium compound may be used as ~he addition product with an
organocarboxylic acid ester. The foregoing magnesium-containing inorganic
compound carriers may be con~acted with an organocarboxylic acid ester
before use. Also, an organo~luminum compound may be used as the additlon
product with an organocarbox~lic acid ester, which would cause no trouble.
Furthermore, in every case in the process of aspects of this invention,
a catalyst system which has l)een prepared in the presence of an organo-
carboxylic acid ester may be used without trouble.
Various aliphatic, alicyclic and aromatic carboxylic acid esters
may be used as organocarboxylic acid esters, among which aromatic carboxylic ~ -
acids having 7 to 12 carbon ~toms are specially preferred. Examples are
alkylesters, e.g., methyl and ethyl of ben~oic acid, anisic acid and
toluic acid.
To illustrate organoaluminum compounds which may be used in the
catalyst used in the process of aspects of this invention, mention may be
made of those represented by the general formulae R3Al, R2AlX, RAlX2,
R2Al~R, RAl(OR)X and R3A12X3 wherein R, which may be the same or different,
is Cl to C20 alkyl or aryl a~d X is halogen, for example, triethylaluminum,
triisobutylaluminum, trihexylaluminum9 trioctylaluminum, diethylaluminum
chloride, ethylaluminum sesquichloride, and mixtures thereof.
The amount of an olganoaluminum compound used in the catalyst
system used in the process o~ aspects of this invention is not specially
- 30 restricted, but usually it is in the range of from 0.1 to 1000 mols per
'~
mol of a transition metal compound.
In the polymerization reaction, a mixture of ethylene and propy-
lene is polymerized in the vapor phase in a reactor, which may be a known
type, e.g., a fluidized bed or an agitation vessel.
The polymerization reaction conditions involve temperatures
usually in the range of from 20 to 110C., preferably from 50" to 100C.,
and pressures in the range of from atmospheric pressure to 70 kg/cm G,
preferably from 2 to 60 kg/cm2-G. The molecular weight can be adjusted by
changing the polymerization temperature, the molar ratio of catalyst or
the amount of comonomer, but the addition of hydrogen into the polymeriæa-
tion system is more effective for this purpose. Of course, using the
process of aspects of this invention, two or more stage polymerization
reactions involving differcnt polymerization conditions, e.g., different
hydrogen and comonomer concentrations and different polymerization tem-
peratures may be carried out, without trouble.
In the process of aspects of this invention, moreover, the fore-
going catalyst systems may be contacted with an o<-olefin before their
use in vapor phase polymerization reaction whereby their polymerization
activities can be largely improved and a more stable operation is assured
than in untreated condition. In this case, vnrious c~-oleEins are employ-
able, preferably those huvLng 3 to 12 carbon atoms and more prefer.qbly
those having 3 to 8 carbon atoms, for exarnple, propylene, butene-l,
pentene-l, 4-methylpentene-1, hexene-l, heptene-l, octene-l, and mixtures
thereof. The temperature and time of the contact between the catalyst used
in the process of aspects of this invention and an o~ -olefin can be
selected in a wide range, for example, the contact treatment may be applied
for 1 minute to 24 hours at a temperature ranging from 0 to 200C., pre-
ferably from 0 to 110C.
The amount of an ~-olefin to be brought into contact can also be
selected in a wide range, but usually it is desired that the contact
~269~
treatment in question be conducted with an ~-olefin in an amount ranging
from 1 g to 50,000 g~ preferably from 5 g to 30,000 g, per gram of the
aforesaid solid substance and that 1 g to 500 g of the ~<-olefin be
reacted with the solid substance. The contact pressure may be selected
optionally, but usually it is desired to be in the range of from -1 to
100 kg/cm2 G.
In the treatment with an C<-olefin, the total amount of an
organoaluminum compound to be used may be combined with the foregoing
solid substance and thereafter the resulting mixture may be contacted with
the ~-olefin, or part of the organoaluminum compound may be combined with
the solid substance and thereafter the resulting mixture may be contacted
with the ~-olefin, while the remaining portion of the organoaluminum com-
po~ d may be .L;cparatcly added in the simultaneous presence of hydrogen gas
or other inert gas, e.g., nitrogen, argon or helium, the catalyst used in
the process of aspects of this invention may be brought into contact with
an '~ -olefin without causing troub]e.
The amount of propylene should be in the range of from 6 to 100
mol%, preferably from 6 to 60 mol% based on the amount of ethylene. Out-
side this range, it is virtually impossible to obtain the object product
from the process of aspects of this invention, nalllely an ctlly1cllc-propylene
copolymer having a melt Lndcx rangLng Erom 0.01 to 10 ~nd a density ranging
from 0.910 to 0.945. The amount of propylene to be used can be easily
adjusted according to the composition ratio of the vapor phase in the
polymerization vessel.
In the copolymerization according to the process of aspects of
this invention, moreover, various dLenes may be added as termonomers, e.g.,
butadiene, l,4-hexadiene, 1,5-hexadiene, vinylnorbornene, ethylidenenor-
borene and dicyclopentadiene.
Working examples of aspects of this invention are given below,
but it is to be understood that these examples are for illustration only
-- 10 --
for working aspects o~ this invention.
Example l
l kg of anhydrous magnesium chloride, 50 g of 1,2-dichloroethane
and 170 g of titanium tetrachloride were subjected to ball milling for 16
hours at room temperature in a nitrogen atmosphere to allow the titanium
compound to be attached to the carrier. The resulting solid substance con~
tained 35 mg of titanium per gram thereof.
There were used a stainless steel autoclave as a vapor phase
polymerization apparatus, a blower, a flow ratio adjuster and a dry cyclone
lC to form a loop, and the temperature of the autoclave was adjusted by passing
warm water through the jacket.
Into the autoclave adjusted to 80C. were introduced the solid
substarlce prepared above and triethylaluminum at the rates of 250 mg/hr and
50 mmol/l-r, respectively, and also introduced were propylene, ethylene and
hydrogen so that the propylene/ethylene ratio (molar ratio) was 0.35 and
the hydrogen gas pressure was 10% of the total pressure, whlle the gases
in the system were circulated by the blower, under which conditions there
was conducted polymerization. The resulting ethylene copolymer had a bulk
density of 0.380, a melt index (ML) of 1.6 and a density of 0.928. It was
powdered with most particle sizes falling under the r~nge of 250 to 500 ~.
The polymerizatLon activity wns vcry h:lgll, 209,300 g copolymcr/g Ti.
After a corltirluous operation for 10 hours, the autoclave was
opened and its interior was checked to find that the inner wall and the
stirrer were clean with no polymer adhesion observed. ~lus, it is apparent
that an extremely stab]e operation is made possible according to the pro-
cess of aspects of this invention, though it is impossible according to
the slurry polymerization shown in Comparative Example 1 below.
The copolymer prepared above was formed into a film 400 mm in
fold diamter by 30~l thick by an inflation film forming 75 mm~ die in a
3~ 50 nun~ extruder. ~le film was superior in strength and had a high trans-
-- 11 --
~12690~
parency with a haze value of 5.8% measured according to JIS K6714.
Comparative Example 1
A continuous slurry polymerization was carried out at 85DC. using
the same catalyst as that used ;n Example 1 and in the presence of hexane
as solvent.
Hexane as a polymerization solvent containing 5 mg!~ of the
solid substance and 1 mmol/~ of triethylaluminum was fed at the rate of
40 ,e /hr, and further introduced were ethylene, propylene (80 mol% of
ethylene) and hydrogen at the rates of 8 kg/hr, 9.6 kg/hr and 3Nm /hr,
respectively, while a continuous polymerization was conducted on condition
that the residence time was 1 hour. The resulting copolymer was continu-
ously withdrawn as slurry. In 2 hours after initiation of the polymeriza-
tion, the polymer slurry withdrawing pipe was obturated, so the polymeriza-
tion was compelled to be discontinued.
A check was made for the in.erior of the reactor to find that
the hexane layer was emulsified and a large amolmt of a rubbery polymer
adhered to the gas-liquid interface and to the withdrawing pipe.
The copolymer prepared above had a bulk density of 0.253, MI of
1.4 and a density of 0.930.
Example 2
_._
830 g of nnhydrolls magneELum chlorldc, 50 g of alllmLnllm oxy-
chlorlde and 170 g of titanium were subjected to ball milling for 16 hours
at room temperature in a nitrogen atmosphere. The resultLng solid substance
contained 41 mg of titanium per gram thereof.
The so]id substance just prepared above and triethylaluminum were
fed at tlle rates of 200 mg/hr and 50 mmol/llr, respectively, and the same
polymerization as in Example 1 was carried out at 80C. with the proviso
that the propylene/ethylene ratio in the vapor phase was 0.20 and the
hydrogen gas pressure was 14% of the total pressure.
After 10 hours of continuous operation, the interior of the
- 12 -
1~269~Q
autoclave was checked, but there was no polymer adhesion.
The resulting copolymer had a bulk density of 0.406, MI of 1.
and a density of 0.938. The polymerization activity was very high,
300,500 g ethylene copolymer/g Ti.
In the same manner as in Example 1, the copolymer was forme~
into a film 400 mm in fold diameter by 30 ~ thick, which was superior in
transparency and in strength.
Comparative Example 2
A solution polymerization was carried out using the sc~me catalyst
as that used in Example 2 and in the presence of j-paraffin as solvent.
n-Paraffin containing 25 mg/~ of the solid substance prepared
in Example 2 and 5 mmol/~ of triethylaluminum was fed at the rate of
40 ~ /hr, and further introduced were ethylene, propylene (117 mol% of
ethylene) and hydrogen at the rates of 8 kg/hr, 14 kg/hr and O.lNm3/hr,
respectively, and a continuous polymerization was carried out at 160C.
on condition that the residence time was 1 hour.
The resulting ethylene had MI of 1.5 and a density of 0.931,
and the polymeri~tion activity was 97,000 g copolymer/g Ti. Thus, it is
apparent that in such a solution polymerization, despite a large excess of
propylene used with respect to ethylene, the denstty was not lowcrcd so
much, and the polymerizatiorl actlvlty ~nd ciriclcllcy wcre low.
Example 3
830 g of anhydrous magnesiu~ chloride, 120 g o~ anthracene and
170 g of titanium tetrachloride were subjected to ball milling in the same
manner ~s in Rxample 1 to give a solid substance which contained 40 mg of
titanlum per gram thereof.
Using the same apparatus as that used in Example 1, the solid
substance and triisobutylaluminum were fed at 80C. at the rates of 500
mg/hr and 150 mmol/hr, respectivcly, and a polymerization was conducted
while making ad~ustment so that the propylene/ethylene ratio in the vapor
- 13 -
1~2~9Qo
phase was 0.82 and the hydrogen gas pressure was 15% of the total pressure.
The polymerization was continued stably for 10 hours; then the
autoclave was opened to find that there was no polymer adhesion inside ~he
reactor.
The polymerization activity was 187,000 g copolymer/g Ti, and
the resulting polymer had a bulk density of 0.375, MI of 4.4 and a density
of 0.915.
The ethylene polymer thus prepared was formed into an inflation
film 400 mm in fold diameter by 30~ thick in the same manner as in Example
1. The film was superior in strength and in transparency with a haze
value of 4.9% measured according to JIS K6714.
Example 4
400 g oE magnesium oxide and 1300 g of anhydrous aluminum
chloride were reacted together at 300C. for 4 hours, then 950 g of the
reaction product and 170 g of titanium tetrachloride were treated in the
same way as in Example 1 to give a solid substance which contained 39 mg
of titanium per gram thereof.
Using the same apparatus as that used in Example 1, the solid
substance just prepared above and triethylaluminum were fed as catalyst
at the rates of 500 mg/hr and 250 mmol/hr, reflpectively, and a polymeriza-
tion was conducted at 70C. while circuLating a mLxed ethylene-propylene
gas containing 72~ of propylene based on the amount of ethylene and also
hydrogen gas adjusted to 10% of the total pressure.
After 18 hours of continuous operation, the interior of the
rcactor was checked to flnd that there was no polymer adhesion.
The res~llting copolymer was composed of oval particles with a
narrow particle size distribution, having an average particle diameter of
800 ~ , a bulk density of 0.36~, MI of 0.60 and a density of 0.920, and
the polymerization activity was 223,000 g copolymer/g Ti.
The copolymer, without pelletizing, was formed into a hollow
1~269~C~
bottle having a capacity of 600 cc by means of a high-speed blow molding
machine. The bottle had a clean surface without draw-down.
