U.S. patent application number 12/990026 was filed with the patent office on 2011-05-12 for adhesive propylene polymer composition suitable for extrusion coating of paper substrates.
This patent application is currently assigned to BOREALIS AG. Invention is credited to Erkki Laiho, Auli Nummila-Pakarinen, Elke Pachner, Hanna Rajala, Markku Sainio, Juha Yli-Peltola.
Application Number | 20110111243 12/990026 |
Document ID | / |
Family ID | 39730799 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110111243 |
Kind Code |
A1 |
Laiho; Erkki ; et
al. |
May 12, 2011 |
Adhesive Propylene Polymer Composition Suitable for Extrusion
Coating of Paper Substrates
Abstract
Two-component adhesion composition suitable for extrusion
coating paper substrates which comprises a) from 70 to 98 wt % of
high melt strength polypropylene (A) with a branching index g' of
0.9 or less and b) from 2 to 30 wt % of a component (B) selected
from the group of (i) maleic anhydride-modified polypropylene
(MAPP) (ii) maleic anhydride-modified polypropylene wax (iii)
polypropylene homopolymer with high melt flow rate or (iv)
ethylene-vinyl acetate-based hot melt adhesive and its use.
Inventors: |
Laiho; Erkki; (Helsinki,
FI) ; Nummila-Pakarinen; Auli; (Porvoo, FI) ;
Pachner; Elke; (Wels, AT) ; Rajala; Hanna;
(Tampere, FI) ; Sainio; Markku; (Porvoo, FI)
; Yli-Peltola; Juha; (Helsinski, FI) |
Assignee: |
BOREALIS AG
Vienna
AT
|
Family ID: |
39730799 |
Appl. No.: |
12/990026 |
Filed: |
August 25, 2009 |
PCT Filed: |
August 25, 2009 |
PCT NO: |
PCT/US09/54892 |
371 Date: |
January 10, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61092448 |
Aug 28, 2008 |
|
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|
Current U.S.
Class: |
428/486 ;
428/511; 428/512; 428/514; 524/112; 524/517 |
Current CPC
Class: |
B32B 2307/306 20130101;
Y10T 428/31899 20150401; B32B 25/06 20130101; B32B 27/32 20130101;
B32B 27/20 20130101; B32B 27/327 20130101; C09J 123/12 20130101;
C08L 51/06 20130101; B32B 2439/70 20130101; C08L 23/0853 20130101;
C09J 2423/10 20130101; B32B 2255/12 20130101; Y10T 428/31906
20150401; B32B 2439/80 20130101; C09J 123/10 20130101; B32B 2323/10
20130101; B32B 27/10 20130101; A61B 2050/3008 20160201; Y10T
428/31895 20150401; A61B 50/30 20160201; Y10T 428/31808 20150401;
B32B 2307/412 20130101; Y10T 428/31902 20150401; B32B 2307/30
20130101; B32B 27/306 20130101; C08L 2666/24 20130101; B32B 2307/50
20130101; C09J 5/00 20130101; B32B 2270/00 20130101; B32B 2553/00
20130101; C09J 123/10 20130101; B32B 27/14 20130101; A61B 50/33
20160201; B32B 27/18 20130101; C09J 123/30 20130101; C08L 2666/24
20130101 |
Class at
Publication: |
428/486 ;
428/511; 428/512; 428/514; 524/112; 524/517 |
International
Class: |
B32B 27/10 20060101
B32B027/10; C08K 5/1539 20060101 C08K005/1539; C09J 137/00 20060101
C09J137/00 |
Claims
1. Two-component adhesion composition suitable for extrusion
coating paper substrates comprising a) from 70 to 98 wt % of high
melt strength polypropylene (A) with a branching index g' of 0.9 or
less, wherein the cross-linked fraction of the polypropylene (A)
does not exceed 1.0 wt.-%, determined as the relative amount of
polymer insoluble in boiling xylene (xylene hot insoluble fraction,
XHI) and b) from 2 to 30 wt % of a component (B) selected from the
group of (i) maleic anhydride-modified polypropylene (MAPP) or (ii)
maleic anhydride-modified polypropylene wax.
2. Composition according to claim 1, wherein the high melt strength
polypropylene (A) is a propylene homopolymer.
3. Composition according to claim 1, wherein the high melt strength
polypropylene (A) has been obtained by treating an unmodified
polypropylene (A') with a peroxide and optionally with a
bifunctional monomer.
4. Composition according to claim 1, wherein the maleic
anhydride-modified polypropylene (i) is a random copolymer of
propylene and ethylene.
5. Composition according to claim 1, wherein the maleic
anhydride-modified polypropylene (i) has a content of maleic
anhydride in the modified polypropylene in the range of 0.001 to 10
wt %, based on the weight of the modified polypropylene.
6. Composition according to claim 1, wherein the maleic
anhydride-modified polypropylene wax (ii) has been obtained by
grafting an unmodified polypropylene wax, which was prepared in the
presence of a metallocene catalyst.
7. Composition according to claim 1, wherein the maleic
anhydride-modified polypropylene wax (ii) has been obtained by
grafting an unmodified polypropylene wax, which had a weight
average molecular weight (Mw) of the polypropylene waxes of less
than 10,000 g/mol.
8. Composition according to claim 1, wherein the maleic
anhydride-modified polypropylene wax (ii) has a content of maleic
anhydride in the modified polypropylene wax in the range of 0.1 to
20 wt % based on the weight of the modified polypropylene.
9. (canceled)
10. (canceled)
11. Composition according to claim 1, wherein the ethylene-vinyl
acetate-based hot melt adhesive (iv) contains ethylene-vinyl
acetate-copolymers with 15 to 45 wt % vinyl acetate and having a
melt index (ISO 1133, 190.degree. C., 2.16 kg) in the range of 2 to
2500 g/10 min.
12. (canceled)
13. Extrusion coating process using paper as substrate and using
the polypropylene composition according to claim 1.
14. Extrusion coated article comprising a paper substrate and at
least one layer of the propylene polymer composition according to
claim 1 on at least one surface of the article.
15. An article according to claim 14 which is as packaging
material.
16. Composition according to claim 2, wherein the high melt
strength polypropylene (A) has been obtained by treating an
unmodified polypropylene (A') with a peroxide and optionally with a
bifunctional monomer.
17. Two-component adhesion composition suitable for extrusion
coating paper substrates comprising a) from 70 to 98 wt % of high
melt strength polypropylene (A) with a branching index g' of 0.9 or
less and b) from 2 to 30 wt % of a component (B) selected from the
group of (iii) polypropylene homopolymer with high melt flow rate
or (iv) ethylene-vinyl acetate-based hot melt adhesive.
18. Composition according to claim 18, wherein the high melt
strength polypropylene (A) is a propylene homopolymer.
19. Composition according to claim 18, wherein the high melt flow
rate polypropylene homopolymer (iii) has a melt flow rate measured
according to ISO 1133 at 230.degree. C. under a load of 2.16 kg of
from 50 to 3000 g/10 min.
20. Composition according to claim 18, wherein the high melt flow
rate polypropylene homopolymer (iii) has been obtained by a
controlled rheology technology using organic peroxides.
21. Composition according to claim 18, wherein the ethylene-vinyl
acetate-based hot melt adhesive (iv) contains ethylene-vinyl
acetate-copolymers with 15 to 45 wt % vinyl acetate and having a
melt index (ISO 1133, 190.degree. C., 2.16 kg) in the range of 2 to
2500 g/10 min.
22. Extrusion coating process using paper as substrate and using
the polypropylene composition according to claim 18.
23. Extrusion coated article comprising a paper substrate and at
least one layer of the propylene polymer composition according to
claim 18 on at least one surface of the article.
24. An article according to claim 23 which is a packaging material.
Description
[0001] The present invention relates to polypropylene-based
adhesive compositions, which are suitable for extrusion coating
especially of paper substrates.
[0002] In general, extrusion coating of substrates such as paper,
paperboard, fabrics and metal foils with a thin layer of plastic is
practiced on a large scale. The polymer is extruded first whereby
the flux of molten polymeric material passes through a flat die to
obtain a film a few microns thick, followed by a coating step,
whereby the film is laid on a support and passes on a cooling
cylinder. Upon cooling, the polymer adheres to its support.
[0003] Low density polyethylene (LDPE) is mainly used in extrusion
coating because of the ease in processing although stiffness,
barrier properties and temperature resistance of LDPE are often not
satisfactory.
[0004] Polypropylene, also known as propylene polymer, is a
well-known commercial polymer, which is used for a variety of
products, such as packaging films and moulded shapes.
[0005] Commercial propylene polymers exhibit several desirable
properties, such as good heat tolerance and transparency, which
make polypropylene polymers interesting in many application
fields.
[0006] However, since many polypropylene materials suffer from low
melt strength and low melt extensibility, they show poor
processibility in high speed extrusion coating.
[0007] Further, the adhesion of polypropylene on substrates like
paper is not satisfactory.
[0008] For these reasons only a few polypropylene-based systems are
available in the industry for extrusion coating at present.
[0009] Many efforts have been undertaken to improve the processing
properties of polypropylene polymers. The shortcomings during
processing have partially been overcome by the class of high melt
strength polypropylene. Such polymers are featured by the
introduction of branchings in the linear polymer backbone. This can
be achieved through post-reactor treatment, copolymerization with
dienes, and through polymerization with specific catalysts at high
temperatures.
[0010] Although these branched polymer types have improved
properties, there is still the desire to improve their adhesion to
substrates such as paper.
[0011] To improve the adhesion between the substrate and the
plastic layer different methods are commonly known, such as ozone
treatment of the molten polymer film, flame treatment and corona
treatment of the substrate or the use of an adhesive layer.
[0012] Various further proposals have been made to increase the
adhesion of propylene polymer layers to different substrates.
[0013] For example, U.S. Pat. No. 4,394,485 discloses four
component adhesive blends comprising modified polyolefin resins
with improved adhesion to polar substrates such as metal, glass,
paper, etc. The blend consists of high density polyethylene (HOPE),
LDPE, a polypropylene homo- or copolymer and a polyethylene polymer
grafted with carboxylic add or acid derivate and can be used in
processes like lamination, coextrusion, powder and/or extrusion
coating, blow molding, etc. The presence of polyethylene components
will necessarily limit the thermal stability of these
compositions.
[0014] According to U.S. Pat. No. 4,394,485 adhesion tests have
been done by heat sealing of compression molded films into
substrates, which is not comparable to the extrusion coating
process due the residence time, temperature and thickness of the
coating. Nevertheless, an improved adhesion to rather unporous
substrates like polypropylene (PP) and ethylene-vinyl alcohol
(EVOH) films, and aluminium foil was observed.
[0015] WO 00/69982 describes adhesive propylene polymer
compositions suitable for coating substrates, which show improved
adhesion to metals without the need for a primer coating or to
polymeric substrates, with a primer coating without the need for
post heating.
[0016] This blend consists of three components comprising (a) 50 to
80 wt % of an unmodified propylene polymer, which may be a homo- or
a copolymer, a heterophasic propylene polymer or mixtures thereof,
(b) 10 to 30 wt % of a high melt strength propylene polymer and (c)
3 to 30 wt % of a modified propylene polymer grafted with an
unsaturated compound having a polar group, wherein the total of
(a), (b) and (c) is 100%.
[0017] U.S. Pat. No. 4,957,968 describes a three component adhesive
thermoplastic elastomer blend, which is adherent to metal, glass,
wood, polyolefins and polar polymers with no pretreatment or use of
other adhesives.
[0018] The three components are (a) a polyolefin modified by a
chemically reactive functional group, (b) a polymer prepared from
one or more of the following: ethylene, propylene, butylene,
isobutylene, octene-1,4-methyl-pentene-1, hexene-1 and (c) an
olefinic elastomer. For example such a blend comprises (a) maleic
anhydride modified polypropylene, (b) polypropylene and (c)
ethylene propylene diene rubber.
[0019] WO 00/31181 describes wettable polypropylene compositions
comprising up to 85 wt % of unmodified polypropylene and up to 35
wt % of a hydrophilic, polar compound which includes functional
sites selected from the group consisting of carboxyl, hydroxyl,
ether or ester moieties. For example maleic anhydride-modified
polypropylene (MAPP) can be used as polar compound. To provide
permanent wettablity a mixture from unmodified polypropylene with
e.g. MAPP is treated with hot potassium hydroxide. The composition
can be used for example to achieve a wettable polypropylene
extrusion coating on paper or paperboard for use in packaging
applications where stiffness and printability is important.
[0020] Although much development work has been done in the field of
adhesive propylene polymer compositions, there is a continuous need
for alternative or improved adhesive propylene polymer
compositions, which can be used in extrusion coating for paper
substrates and which show an improved adhesion to the substrate
compared to known propylene polymer materials, high melt strength
propylene polymers and blends thereof.
OBJECT OF THE INVENTION
[0021] An object of the invention is therefore to provide
polypropylene compositions, which are particularly suitable for
extrusion coating on paper substrates, having high melt strength
and improved adhesion to paper or paperboard without the need of
surface treating methods or additional adhesion layers.
[0022] A further object of the invention is the use of the
polypropylene composition in extrusion coating processes using
paper or paperboard as substrate.
[0023] Another object of the present invention is to provide a
substrate or article which has at least one layer of highly
adherent propylene polymer composition on at least one surface.
SUMMARY OF THE INVENTION
[0024] The present invention relates to polypropylene compositions
useable for extrusion coating of paper substrates and showing
improved adhesion to the substrate, yielding extrusion coating
products of high quality.
[0025] Particularly, the present invention deals with two component
adhesion compositions suitable for extrusion coating paper
substrates comprising a blend of high melt strength polypropylene
and one component selected from the group of [0026] (i) maleic
anhydride-modified polypropylene (MAPP) [0027] (ii) maleic
anhydride-modified polypropylene wax [0028] (iii) polypropylene
homopolymer with high melt flow rate or [0029] (iv) ethylene-vinyl
acetate-based hot melt adhesive
DETAILED DESCRIPTION OF THE INVENTION
[0030] It has now been discovered that the problems and
deficiencies relating to the compositions and blends according to
the state of the art regarding insufficient adhesion to paper or
paperboard substrates can be avoided or at least significantly
decreased with a composition according to the present invention. It
has been noted that certain combinations of high melt strength
polypropylene with special polypropylenes or an ethylene-vinyl
acetate-based hot melt adhesive meet the objectives.
[0031] The two component adhesion composition suitable for
extrusion coating paper substrates according to the invention
comprises: [0032] a) from 70 to 98 wt %, preferably 75 to 95 wt %
of high melt strength polypropylene (A) with a branching index g'
of 0.9 or less and [0033] b) from 2 to 30 wt %, preferably 5 to 25
wt % of a component (B) selected from the group of [0034] (i)
maleic anhydride-modified polypropylene (MAPP) [0035] (ii) maleic
anhydride-modified polypropylene wax [0036] (iii) polypropylene
homopolymer with high melt flow rate or [0037] (iv) ethylene-vinyl
acetate-based hot melt adhesive
[0038] Thus the first mandatory component in the present invention
is a polypropylene (A) characterized by a certain degree of
branching. Possible polypropylenes (A) are so called
Y/H-polypropylenes and are for instance described in EP 0 787 750,
i.e. single branched polypropylene types (Y polypropylenes having a
backbone with a single long side-chain and an architecture
resembles a "Y") and polypropylene types in which polymer chains
are coupled with a bridging group (an architecture resembles a
"H"), as well as multi-branched polypropylenes, i.e. not only the
polypropylene backbone is furnished with a larger number of side
chains (branched polypropylene) but also some of the side chains
themselves. Such polypropylenes are characterized by rather high
melt strength.
[0039] A parameter of the degree of branching is the branching
index g'. The branching index g' correlates with the amount of
branches of a polymer. The branching index g' is defined as
g'=[IV].sub.br/[IV].sub.lin in which g' is the branching index,
[IV.sub.br] is the intrinsic viscosity of the branched
polypropylene and [IV].sub.lin is the intrinsic viscosity of the
linear polypropylene having the same weight average molecular
weight (within a range of .+-.10%) as the branched polypropylene.
Thereby, a low g'-value is an indicator for a high branched
polymer. In other words, if the g'-value decreases, the branching
of the polypropylene increases. Reference is made in this context
to B. H. Zimm and W. H. Stockmeyer, J. Chem. Phys. 17, 1301 (1949).
This document is herewith included by reference.
[0040] The intrinsic viscosity needed for determining the branching
index g' is measured according to DIN ISO 1628/1, October 1999 (in
Decalin at 135.degree. C.).
[0041] Thus it is preferred that the branching index g' of the
polypropylene (A) shall be less than 0.9, more preferably equal or
less than 0.8. In another preferred embodiment the branching index
g' of the polypropylene (A) shall be preferably less than 0.7.
[0042] The polypropylene (A) can be a propylene homopolymer or a
propylene copolymer, wherein the homopolymer is preferred.
[0043] Accordingly, the homopolymer as well as the copolymer can be
a unimodal or multimodal polymer composition.
[0044] In a preferred embodiment the polypropylene is preferably
unimodal. In another preferred embodiment the polypropylene is
preferably multimodal, more preferably bimodal.
[0045] "Multimodal" or "multimodal distribution" describes a
frequency distribution that has several relative maxima. In
particular, the expression "modality of a polymer" refers to the
form of its molecular weight distribution (MWD) curve, i.e. the
appearance of the graph of the polymer weight fraction as a
function of its molecular weight. If the polymer is produced in the
sequential step process, i.e. by utilizing reactors coupled in
series, and using different conditions in each reactor, the
different polymer fractions produced in the different reactors each
have their own molecular weight distribution which may considerably
differ from one another. The molecular weight distribution curve of
the resulting final polymer can be seen at a super-imposing of the
molecular weight distribution curves of the polymer fraction which
will, accordingly, show a more distinct maxima, or at least be
distinctively broadened compared with the curves for individual
fractions.
[0046] A polymer showing such molecular weight distribution curve
is called bimodal or multimodal, respectively.
[0047] The expression homopolymer used in the instant invention
relates to a polypropylene that consists substantially, i.e. of at
least 97 wt %, preferably of at least 99 wt %, and most preferably
of at least 99.8 wt % of propylene units. In a preferred embodiment
only propylene units in the propylene homopolymer are detectable.
The comonomer content can be determined with FT infrared
spectroscopy, as described below in the examples.
[0048] In case the polypropylene according to this invention is a
propylene copolymer, it is preferred that the comonomer is
ethylene. However, also other comonomers known in the art are
suitable. Preferably, the total amount of comonomer, more
preferably ethylene, in the propylene copolymer is up to 15 wt %,
more preferably up to 10 wt %.
[0049] It is also possible that the polypropylene is a propylene
copolymer comprising a polypropylene matrix and an
ethylene-propylene rubber (EPR).
[0050] The polypropylene matrix can be a homopolymer or a
copolymer, more preferably multimodal, i.e. bimodal, homopolymer or
a multimodal, i.e. bimodal, copolymer. In case the polypropylene
matrix is a propylene copolymer, then it is preferred that the
comonomer is ethylene or butene. However, also other comonomers
known in the art are suitable. The preferred amount of comonomer,
more preferably ethylene, in the polypropylene matrix is up to 8.00
mol %. In case the propylene copolymer matrix has ethylene as the
comonomer component, it is in particular preferred that the amount
of ethylene in the matrix is up to 8.00 mol %, more preferably less
than 6.00 mol %. In case the propylene copolymer matrix has butene
as the comonomer component, it is in particular preferred that the
amount of butene in the matrix is up to 6.00 mol %, more preferably
less than 4.00 mol %.
[0051] Preferably, the ethylene-propylene rubber (EPR) in the total
propylene copolymer is up to 60 wt %. More preferably the amount of
ethylene-propylene rubber (EPR) in the total propylene copolymer is
in the range of 15 to 60 wt %, still more preferably in the range
of 20 to 50 wt %.
[0052] In addition, it is preferred that the polypropylene being a
copolymer comprising a polypropylene matrix and an
ethylene-propylene rubber (EPR) has an ethylene-propylene rubber
(EPR) with an ethylene-content of up to 65 wt %.
[0053] The high degree of branching of the polypropylene (A)
contributes also to its melt strength. Accordingly it is preferred
that the polypropylene (A) is further characterized by a melt
strength of at least 10 cN at a maximum speed of at least 200 mm/s,
more preferably by a melt strength of at least 20 cN at a maximum
speed of at least 200 mm/s, still more preferably by a melt
strength of at least 25 cN at a maximum speed of at least 200 mm/s,
yet more preferably by a melt strength of at least 25 cN at a
maximum speed of at least 250 mm/s. The measuring of the melt
strength has been undertaken by a temperature of 200.degree. C.
with an acceleration of the melt strand drawn down of 120
mm/sec.sup.2. The exact measuring method is defined in the example
section.
[0054] Furthermore, it is preferred that the polypropylene has a
melt flow rate (MFR) given in a specific range. The melt flow rate
mainly depends on the average molecular weight. This is due to the
fact that long molecules render the material a lower flow tendency
than short molecules. An increase in molecular weight means a
decrease in the MFR-value. The melt flow rate (MFR) is measured in
g/10 min of the polymer discharged through a defined die under
specified temperature and pressure conditions and the measure of
viscosity of the polymer which, in turn, for each type of polymer
is mainly influenced by its molecular weight but also by its degree
of branching. The melt flow rate measured under a load of 2.16 kg
at 230.degree. C. (ISO 1133) is denoted as MFR.sub.2 (230.degree.
C.). Accordingly, it is preferred that in the present invention the
polypropylene (A) has an MFR.sub.2 (230.degree. C.) in a range of
0.01 to 100 g/10 min, more preferably of 0.10 to 50 g/10 min, still
more preferred of 1.00 to 25 g/10 min.
[0055] Preferably the cross-linked fraction of the polypropylene
(A) does not exceed 1.0 wt.-%, even more preferred does not exceed
0.8 wt.-%, still more preferred does not exceed 0.5 wt.-%
determined as the relative amount of polymer insoluble in boiling
xylene (xylene hot insoluble fraction, XHI).
[0056] More preferably, the polypropylene of the instant invention
is isotactic. Thus the polypropylene according to this invention
shall have a rather high pentade concentration, i.e. higher than
90%, more preferably higher than 92% and most preferably higher
than 93%. In another preferred embodiment the pentade concentration
is higher than 95%. The pentade concentration is an indicator for
the narrowness in the stereoregularity distribution of the
polypropylene.
[0057] The high melt strength polypropylene (A) can be preferably
further defined by the way obtained.
[0058] Accordingly the polypropylene (A) can be the result of
treating an unmodified polypropylene (A') with thermally
decomposing radical-forming agents and/or with ionizing radiation,
where both treatments may optionally be accompanied or followed by
a treatment with bi- or multifunctionally unsaturated monomers,
e.g. butadiene, isoprene, dimethylbutadiene or divinylbenzene. A
suitable method to obtain the polypropylene (A) is for instance
disclosed in EP 0 879 830 A1 and EP 0 890 612 A2. Both documents
are herewith included by reference.
[0059] The unmodified polypropylene (A') has preferably a MFR.sub.2
(230.degree. C.) in a range of 0.05 to 45.00 g/10 min. More
preferably the MFR.sub.2 (230.degree. C.) is in a range of 0.05 to
35.00 g/10 min in case the unmodified polypropylene (A') is a
homopolymer. On the other hand the MFR.sub.2 (230.degree. C.) is in
a range of 0.05 to 45.00 g/10 min in case the unmodified
polypropylene (A') is a copolymer.
[0060] Preferably the unmodified polypropylene (A') comprises 85.0
to 99.9 wt.-% of propylene and 0.1 to 15.0 wt % of one or more
.alpha.-olefins with 2 or 4 to 18 carbon atoms, in particular
ethylene.
[0061] As stated above the unmodified polypropylene (A') is
preferably multimodal, more preferably bimodal. Accordingly it is
preferred that the unmodified polypropylene (A') has a molecular
weight distribution (MWD) of 5 to 60, more preferably in the range
of 15 to 35.
[0062] Moreover the unmodified polypropylene (A') has preferably a
weight average molecular weight (M.sub.w) of 500,000 to 1,500,000
g/mol, more preferably in the range of 600,000 to 1,000,000 g/mole.
The number average molecular weight (M.sub.n) preferably ranges of
25,000 to 100,000 g/mol and more preferably of 30,000 to 100,000
g/mol.
[0063] The number average molecular weight (Mn) and the weight
average molecular weight (Mw) as well as the molecular weight
distribution (MWD) are determined in the instant invention by size
exclusion chromatography (SEC) using Waters Alliance GPCV 2000
instrument with online viscometer. The oven temperature is
140.degree. C. Trichlorobenzene is used as a solvent (ISO
16014).
[0064] The peroxide used for the manufacture of polypropylene (A)
is preferably a thermally decomposing free radical-forming agent,
more preferably selected from the group consisting of acyl
peroxide, alkyl peroxide, hydroperoxide, perester and
peroxycarbonate.
[0065] The following listed peroxides are in particular
preferred:
[0066] Acyl peroxides: benzoyl peroxide, 4-chlorobenzoyl peroxide,
3-methoxybenzoyl peroxide and/or methyl benzoyl peroxide.
[0067] Alkyl peroxides: allyl t-butyl peroxide,
2,2-bis(t-butylperoxybutane),
1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
n-butyl-4,4-bis(t-butylperoxy) valerate,
diisopropylaminomethyl-t-amyl peroxide, dimethylaminomethyl-t-amyl
peroxide, diethylaminomethyl-t-butyl peroxide,
dimethylaminomethyl-t-butyl peroxide,
1,1-di-(t-amylperoxy)cyclohexane, t-amyl peroxide, t-butylcumyl
peroxide, t-butyl peroxide and/or 1-hydroxybutyl n-butyl
peroxide.
[0068] Peresters and peroxy carbonates: butyl peracetate, cumyl
peracetate, cumyl perpropionate, cyclohexyl peracetate, di-t-butyl
peradipate, di-t-butyl perazelate, di-t-butyl perglutarate,
di-t-butyl perthalate, di-t-butyl persebacate, 4-nitrocumyl
perpropionate, 1-phenylethyl perbenzoate, phenylethyl
nitro-perbenzoate, t-butylbicyclo-(2,2,1)heptane percarboxylate,
t-butyl-4-carbomethoxy perbutyrate, t-butylcyclobutane
percarboxylate, t-butylcyclohexyl peroxycarboxylate,
t-butylcyclopentyl percarboxylate, t-butylcyclopropane
percarboxylate, t-butyldimethyl percinnamate,
t-butyl-2-(2,2-diphenylvinyl) perbenzoate, t-butyl-4-methoxy
perbenzoate, t-butyl perbenzoate, t-butylcarboxycyclo hexane,
t-butyl pernaphthoate, t-butyl peroxyisopropylcarbonate, t-butyl
pertoluate, t-butyl-1-phenylcyclopropyl percarboxylate,
t-butyl-2-propylperpentene-2-oate, t-butyl-1-methylcyclopropyl
percarboxylate, t-butyl-4-nitrophenyl peracetate,
t-butylnitrophenyl peroxycarbamate, t-butyl-N-succiimido
percarboxylate, t-butyl percrotonate, t-butyl permaleic acid,
t-butyl permethacrylate, t-butyl peroctoate, t-butyl
peroxyisopropylcarbonate, t-butyl perisobutyrate, t-butyl
peracrylate and/or t-butyl perpropionate;
or mixtures of these above listed free radical-forming agents.
[0069] If present in the process for the manufacture of the
polypropylene (A), the (volatile) bifunctional monomers are
preferably ethylenically unsaturated, multifunctional monomers,
like C4 to C10 dienes and/or C7 to C10 divinyl compounds.
Especially preferred bifunctional monomers are butadiene, isoprene,
dimethylbutadiene and divinylbenzene.
[0070] The polypropylene (A) is preferably obtained by a process as
described in EP 0 879 830 A1 and EP 0 890 612 A2. Both documents
are herewith included by reference. Accordingly the polypropylene
is produced by [0071] (a) mixing [0072] (i) a unmodified propylene
homopolymer and/or copolymer (A') as defined above, preferably a
unmodified propylene homopolymer with a weight average molecular
weight (M.sub.w) of 500,000 to 1,500,000 g/mol, [0073] (ii) from
0.05 to 3 wt.-% based on the components of (i) and (ii), of a
peroxide selected from the group consisting of acyl peroxide, alkyl
peroxide, hydroperoxide, perester and peroxycarbonate, and [0074]
(iii) optionally diluted with inert solvents, [0075] (b) heating to
30-100.degree. C., preferably to 60-90.degree. C., [0076] (c)
sorption of volatile bifunctional monomers, preferably
ethylenically unsaturated, multifunctional monomers, like C4 to C10
dienes and/or C7 to C10 divinyl compounds, by the unmodified
propylene homopolymer and/or copolymer (A), preferably unmodified
propylene homopolymer (A), from the gas phase at a temperature of
from 20 to 120.degree. C., preferably of from 60 to 100.degree. C.,
where the amount of the absorbed bifunctionally unsaturated
monomers is from 0.01 to 10.00 wt.-%, preferably from 0.05 to 2.00
wt.-%, based on the propylene homopolymer (A'), [0077] (d) heating
and melting the polypropylene composition in an atmosphere
comprising inert gas and/or the volatile bifunctional monomers,
from sorption temperature to 210.degree. C., whereupon the
free-radical generators are decomposed and then [0078] (e) heating
the melt up to 280.degree. C. in order to remove unreacted monomers
and decomposition products, and [0079] (f) agglomerating the
melt.
[0080] Usual amounts of auxiliary substances, which may range from
0.01 to 2.5% by weight of stabilizers, 0.01 to 1% by weight of
processing aids, 0.1 to 1% by weight of antistats, 0.2 to 3% by
weight of pigments and up to 3% by weight of .alpha.-nucleating
agents, in each case based on the sum of the propylene polymers,
may be added before step a) and/or f) of the method and/or before
or during step d) and/or e) of the above described method.
[0081] The process for producing the modified propylene polymer
preferably is a continuous method, performed in continuous
reactors, mixers, kneaders and extruders. Batchwise production of
the modified propylene polymer however is feasible as well.
[0082] Practical sorption times .tau. of the volatile bifunctional
monomers range from 10 to 1000 s, where sorption times .tau. of 60
to 600 are preferred.
[0083] Polypropylene (A) can also be produced in the presence of a
metallocene catalyst, as, for example, described in EP 1 892 264
using a catalyst system comprising an asymmetric catalyst, whereby
the catalyst system has a porosity of less than 1.40 ml/g, more
preferably less than 1.30 ml/g and most preferably less than 1.00
ml/g. The porosity has been measured according to DIN 66135
(N.sub.2). In another preferred embodiment the porosity is not
detectable when determined with the method applied according to DIN
66135 (N.sub.2).
[0084] An asymmetric catalyst is a metallocene compound comprising
at least two organic ligands which differ in their chemical
structure. More preferably the asymmetric catalyst is a metallocene
compound comprising at least two organic ligands which differ in
their chemical structure and the metallocene compound is free of
C.sub.2-symmetry and/or any higher symmetry. Preferably the
asymmetric metallocene compound comprises only two different
organic ligands, still more preferably comprises only two organic
ligands which are different and linked via a bridge.
[0085] Said asymmetric catalyst is preferably a single site
catalyst (SSC).
[0086] Furthermore it is preferred, that the catalyst system has a
surface area of less than 25 m.sup.2/g, yet more preferred less
than 20 m.sup.2/g, still more preferred less than 15 m.sup.2/g, yet
still less than 10 m.sup.2/g and most preferred less than 5
m.sup.2/g. The surface area according to this invention is measured
according to ISO 9277 (N.sub.2).
[0087] It is in particular preferred that the catalytic system
comprises an asymmetric catalyst, i.e. a catalyst as defined below,
and has porosity not detectable when applying the method according
to DIN 66135 (N.sub.2) and has a surface area measured according to
ISO 9277 (N.sub.2) less than 5 m.sup.2/g.
[0088] Preferably the asymmetric catalyst compound, i.e. the
asymmetric metallocene, has the formula (I):
(Cp).sub.2R.sub.zMX.sub.2 (I)
wherein z is 0 or 1, M is Zr, Hf or Ti, more preferably Zr, and X
is independently a monovalent anionic ligand, such as
.sigma.-ligand R is a bridging group linking the two Cp ligands Cp
is an organic ligand selected from the group consisting of
unsubstituted cyclopentadienyl, unsubstituted indenyl,
unsubstituted tetrahydroindenyl, unsubstituted fluorenyl,
substituted cyclopentadienyl, substituted indenyl, substituted
tetrahydroindenyl, and substituted fluorenyl, with the proviso that
both Cp-ligands are selected from the above stated group and both
Cp-ligands have a different chemical structure.
[0089] The term ".sigma.-ligand" is understood in the whole
description in a known manner, i.e. a group bonded to the metal at
one or more places via a sigma bond. A preferred monovalent anionic
ligand is halogen, in particular chlorine (Cl).
[0090] Preferably, the asymmetric catalyst is of formula (I)
indicated above,
wherein
M is Zr and
[0091] each X is Cl.
[0092] Preferably both identical Cp-ligands are substituted.
[0093] Preferably both Cp-ligands have different residues to obtain
an asymmetric structure.
[0094] Preferably, both Cp-ligands are selected from the group
consisting of substituted cyclopentadienyl-ring, substituted
indenyl-ring, substituted tetrahydroindenyl-ring, and substituted
fluorenyl-ring wherein the Cp-ligands differ in the substituents
bonded to the rings.
[0095] The optional one or more substituent(s) bonded to
cyclopentadienyl, indenyl, tetrahydroindenyl, or fluorenyl may be
independently selected from a group including halogen, hydrocarbyl
(e.g. C.sub.1-C.sub.20-alkyl, C.sub.2-C.sub.20-alkenyl,
C.sub.2-C.sub.20-alkynyl, C.sub.3-C.sub.12-cycloalkyl,
C.sub.6-C.sub.20-aryl or C.sub.7-C.sub.20-arylalkyl),
C.sub.3-C.sub.12-cycloalkyl which contains 1, 2, 3 or 4
heteroatom(s) in the ring moiety, C.sub.6-C.sub.20-heteroaryl,
--SiR''.sub.3, --OSiR''.sub.3, --SR'', --PR''.sub.2 and
--NR''.sub.2, wherein each R'' is independently a hydrogen or
hydrocarbyl, e.g. C.sub.1-C.sub.20-alkyl, C.sub.2-C.sub.20-alkenyl,
C.sub.2-C.sub.20-alkynyl, C.sub.3-C.sub.12-cycloalkyl or
C.sub.6-C.sub.20-aryl.
[0096] More preferably both Cp-ligands are indenyl moieties wherein
each indenyl moiety bear one or two substituents as defined above.
More preferably each Cp-ligand is an indenyl moiety bearing two
substituents as defined above, with the proviso that the
substituents are chosen in such are manner that both Cp-ligands are
of different chemical structure, i.e. both Cp-ligands differ at
least in one substituent bonded to the indenyl moiety, in
particular differ in the substituent bonded to the five member ring
of the indenyl moiety.
[0097] Still more preferably both Cp are indenyl moieties wherein
the indenyl moieties comprise at least at the five membered ring of
the indenyl moiety, more preferably at 2-position, a substituent
selected from the group consisting of alkyl, such as
C.sub.1-C.sub.6 alkyl, e.g. methyl, ethyl, isopropyl, and
trialkyloxysiloxy, wherein each alkyl is independently selected
from C.sub.1-C.sub.6 alkyl, such as methyl or ethyl, with proviso
that the indenyl moieties of both Cp must chemically differ from
each other, i.e. the indenyl moieties of both Cp comprise different
substituents.
[0098] Still more preferred both Cp are indenyl moieties wherein
the indenyl moieties comprise at least at the six membered ring of
the indenyl moiety, more preferably at 4-position, a substituent
selected from the group consisting of a C.sub.6-C.sub.20 aromatic
ring moiety, such as phenyl or naphthyl, preferably phenyl, which
is optionally substituted with one or more substituents, such as
C.sub.1-C.sub.6 alkyl, and a heteroaromatic ring moiety, with
proviso that the indenyl moieties of both Cp must chemically differ
from each other, i.e. the indenyl moieties of both Cp comprise
different substituents.
[0099] Yet more preferably both Cp are indenyl moieties wherein the
indenyl moieties comprise at the five membered ring of the indenyl
moiety, more preferably at 2-position, a substituent and at the six
membered ring of the indenyl moiety, more preferably at 4-position,
a further substituent, wherein the substituent of the five membered
ring is selected from the group consisting of alkyl, such as
C.sub.1-C.sub.6 alkyl, e.g. methyl, ethyl, isopropyl, and
trialkyloxysiloxy, wherein each alkyl is independently selected
from C.sub.1-C.sub.6 alkyl, such as methyl or ethyl, and the
further substituent of the six membered ring is selected from the
group consisting of a C.sub.6-C.sub.20 aromatic ring moiety, such
as phenyl or naphthyl, preferably phenyl, which is optionally
substituted with one or more substituents, such as C.sub.1-C.sub.6
alkyl, and a heteroaromatic ring moiety, with proviso that the
indenyl moieties of both Cp must chemically differ from each other,
i.e. the indenyl moieties of both Cp comprise different
substituents. It is in particular preferred that both Cp are idenyl
rings comprising two substituents each and differ in the
substituents bonded to the five membered ring of the idenyl
rings.
[0100] Concerning the moiety "R" it is preferred that "R" has the
formula (II)
--Y(R').sub.2 (II)
wherein
Y is C, Si or Ge, and
[0101] R' is C.sub.1 to C.sub.20 alkyl, C.sub.6-C.sub.12 aryl, or
C.sub.7-C.sub.12 arylalkyl or trimethylsilyl.
[0102] In case both Cp-ligands of the asymmetric catalyst as
defined above, in particular case of two indenyl moieties, are
linked with a bridge member R, the bridge member R is typically
placed at 1-position. The bridge member R may contain one or more
bridge atoms selected from e.g. C, Si and/or Ge, preferably from C
and/or Si. One preferable bridge R is --Si(R').sub.2--, wherein R'
is selected independently from one or more of e.g. trimethylsilyl,
C.sub.1-C.sub.10 alkyl, C.sub.1-C.sub.20 alkyl, such as
C.sub.6-C.sub.12 aryl, or C.sub.7-C.sub.40, such as
C.sub.7-C.sub.12 arylalkyl, wherein alkyl as such or as part of
arylalkyl is preferably C.sub.1-C.sub.6 alkyl, such as ethyl or
methyl, preferably methyl, and aryl is preferably phenyl. The
bridge --Si(R').sub.2-- is preferably e.g. --Si(C.sub.1-C.sub.6
alkyl).sub.2-, --Si(phenyl).sub.2-- or --Si(C.sub.1-C.sub.6
alkyl)(phenyl)-, such as --Si(Me).sub.2-.
[0103] In a preferred embodiment the asymmetric catalyst, i.e. the
asymmetric metallocene, is defined by the formula (III)
(Cp).sub.2R.sub.1ZrCl.sub.2 (III)
wherein both Cp coordinate to M and are selected from the group
consisting of unsubstituted cyclopentadienyl, unsubstituted
indenyl, unsubstituted tetrahydroindenyl, unsubstituted fluorenyl,
substituted cyclopentadienyl, substituted indenyl, substituted
tetrahydroindenyl, and substituted fluorenyl, with the proviso that
both Cp-ligands are of different chemical structure, and R is a
bridging group linking two ligands L, wherein R is defined by the
formula (II)
--Y(R').sub.2-- (II)
wherein
Y is C, Si or Ge, and
[0104] R' is C.sub.1 to C.sub.20 alkyl, C.sub.6-C.sub.12 aryl, or
C.sub.7-C.sub.12 arylalkyl.
[0105] More preferably the asymmetric catalyst is defined by the
formula (III), wherein both Cp are selected from the group
consisting of substituted cyclopentadienyl, substituted indenyl,
substituted tetrahydroindenyl, and substituted fluorenyl.
[0106] Yet more preferably the asymmetric catalyst is defined by
the formula (III), wherein both Cp are selected from the group
consisting of substituted cyclopentadienyl, substituted indenyl,
substituted tetrahydroindenyl, and substituted fluorenyl
with the proviso that both Cp-ligands differ in the substituents,
i.e. the substituents as defined above, bonded to cyclopentadienyl,
indenyl, tetrahydroindenyl, or fluorenyl.
[0107] Still more preferably the asymmetric catalyst is defined by
the formula (III), wherein both Cp are indenyl and both indenyl
differ in one substituent, i.e. in a substituent as defined above
bonded to the five member ring of indenyl.
[0108] It is in particular preferred that the asymmetric catalyst
is a non-silica supported catalyst as defined above, in particular
a metallocene catalyst as defined above.
[0109] In a preferred embodiment the asymmetric catalyst is
dimethylsilyl
[(2-methyl-(4'-tert.butyl)-4-phenyl-indenyl)(2-isopropyl-(4'-tert.butyl)--
4-phenyl-indenyl)]zirkonium dichloride (IUPAC: dimethylsilandiyl
[(2-methyl-(4'-tert.butyl)-4-phenyl-indenyl)(2-isopropyl-(4'-tert.butyl)--
4-phenyl-indenyl)]zirkonium dichloride). More preferred said
asymmetric catalyst is not silica supported.
[0110] The above described asymmetric catalyst components are
prepared according to the methods described in WO 01/48034.
[0111] It is in particular preferred that the asymmetric catalyst
system is obtained by the emulsion solidification technology as
described in WO 03/051934. This document is herewith included in
its entirety by reference. Hence the asymmetric catalyst is
preferably in the form of solid catalyst particles, obtainable by a
process comprising the steps of [0112] a) preparing a solution of
one or more asymmetric catalyst components; [0113] b) dispersing
said solution in a solvent immiscible therewith to form an emulsion
in which said one or more catalyst components are present in the
droplets of the dispersed phase, [0114] c) solidifying said
dispersed phase to convert said droplets to solid particles and
optionally recovering said particles to obtain said catalyst.
[0115] Preferably a solvent, more preferably an organic solvent, is
used to form said solution. Still more preferably the organic
solvent is selected from the group consisting of a linear alkane,
cyclic alkane, linear alkene, cyclic alkene, aromatic hydrocarbon
and halogen-containing hydrocarbon.
[0116] Moreover the immiscible solvent forming the continuous phase
is an inert solvent, more preferably the immiscible solvent
comprises a fluorinated organic solvent and/or a functionalized
derivative thereof, still more preferably the immiscible solvent
comprises a semi-, highly- or perfluorinated hydrocarbon and/or a
functionalized derivative thereof. It is in particular preferred,
that said immiscible solvent comprises a perfluorohydrocarbon or a
functionalized derivative thereof, preferably C.sub.3-C.sub.30
perfluoroalkanes, -alkenes or -cycloalkanes, more preferred
C.sub.4-C.sub.10 perfluoro-alkanes, -alkenes or -cycloalkanes,
particularly preferred perfluorohexane, perfluoroheptane,
perfluorooctane or perfluoro (methylcyclohexane) or a mixture
thereof.
[0117] Furthermore it is preferred that the emulsion comprising
said continuous phase and said dispersed phase is a bi- or
multiphasic system as known in the art. An emulsifier may be used
for forming the emulsion. After the formation of the emulsion
system, said catalyst is formed in situ from catalyst components in
said solution.
[0118] In principle, the emulsifying agent may be any suitable
agent which contributes to the formation and/or stabilization of
the emulsion and which does not have any adverse effect on the
catalytic activity of the catalyst. The emulsifying agent may e.g.
be a surfactant based on hydrocarbons optionally interrupted with
(a) heteroatom(s), preferably halogenated hydrocarbons optionally
having a functional group, preferably semi-, highly- or
perfluorinated hydrocarbons as known in the art. Alternatively, the
emulsifying agent may be prepared during the emulsion preparation,
e.g. by reacting a surfactant precursor with a compound of the
catalyst solution. Said surfactant precursor may be a halogenated
hydrocarbon with at least one functional group, e.g. a highly
fluorinated C.sub.1 to C.sub.30 alcohol, which reacts e.g. with a
cocatalyst component, such as aluminoxane.
[0119] In principle any solidification method can be used for
forming the solid particles from the dispersed droplets. According
to one preferable embodiment the solidification is effected by a
temperature change treatment. Hence the emulsion subjected to
gradual temperature change of up to 10.degree. C./min, preferably
0.5 to 6.degree. C./min and more preferably 1 to 5.degree. C./min.
Even more preferred the emulsion is subjected to a temperature
change of more than 40.degree. C., preferably more than 50.degree.
C. within less than 10 seconds, preferably less than 6 seconds.
[0120] The recovered particles have preferably an average size
range of 5 to 200 .mu.m, more preferably 10 to 100 .mu.m.
[0121] Moreover, the form of solidified particles have preferably a
spherical shape, a predetermined particles size distribution and a
surface area as mentioned above of preferably less than 25
m.sup.2/g, still more preferably less than 20 m.sup.2/g, yet more
preferably less than 15 m.sup.2/g, yet still more preferably less
than 10 m.sup.2/g and most preferably less than 5 m.sup.2/g,
wherein said particles are obtained by the process as described
above.
[0122] For further details, embodiments and examples of the
continuous and dispersed phase system, emulsion formation method,
emulsifying agent and solidification methods reference is made e.g.
to the above cited international patent application WO
03/051934.
[0123] As mentioned above the catalyst system may further comprise
an activator as a cocatalyst, as described in WO 03/051934, which
is enclosed herein with reference.
[0124] Preferred as cocatalysts for metallocenes and
non-metallocenes, if desired, are the aluminoxanes, in particular
the C.sub.1-C.sub.10-alkylaluminoxanes, most particularly
methylaluminoxane (MAO). Such aluminoxanes can be used as the sole
cocatalyst or together with other cocatalyst(s). Thus besides or in
addition to aluminoxanes, other cation complex forming catalysts
activators can be used. Said activators are commercially available
or can be prepared according to the prior art literature.
[0125] Further aluminoxane cocatalysts are described i.a. in WO
94/28034 which is incorporated herein by reference. These are
linear or cyclic oligomers of having up to 40, preferably 3 to 20,
--(Al(R''')O)-- repeat units (wherein R''' is hydrogen,
C.sub.1-C.sub.10-alkyl (preferably methyl) or C.sub.6-C.sub.18-aryl
or mixtures thereof).
[0126] The use and amounts of such activators are within the skills
of an expert in the field. As an example, with the boron
activators, 5:1 to 1:5, preferably 2:1 to 1:2, such as 1:1, ratio
of the transition metal to boron activator may be used. In case of
preferred aluminoxanes, such as methylaluminumoxane (MAO), the
amount of Al, provided by aluminoxane, can be chosen to provide a
molar ratio of Al:transition metal e.g. in the range of 1 to 10
000, suitably 5 to 8000, preferably 10 to 7000, e.g. 100 to 4000,
such as 1000 to 3000. Typically in case of solid (heterogeneous)
catalyst the ratio is preferably below 500.
[0127] The quantity of cocatalyst to be employed in the catalyst of
the invention is thus variable, and depends on the conditions and
the particular transition metal compound chosen in a manner well
known to a person skilled in the art.
[0128] Any additional components to be contained in the solution
comprising the organotransition compound may be added to said
solution before or, alternatively, after the dispersing step.
[0129] The process for producing polypropylene (A) using the above
defined metallocene catalyst is a multi-stage process.
[0130] Multistage processes include also bulk/gas phase reactors
known as multizone gas phase reactors for producing multimodal
propylene polymer.
[0131] A preferred multistage process is a "loop-gas
phase"-process, such as developed by Borealis A/S, Denmark (known
as BORSTAR.RTM. technology) described e.g. in patent literature,
such as in EP 0 887 379 or in WO 92/12182.
[0132] Multimodal polymers can be produced according to several
processes which are described, e.g. in WO 92/12182, EP 0 887 379
and WO 97/22633.
[0133] A multimodal polypropylene (A) is produced preferably in a
multi-stage process in a multi-stage reaction sequence as described
in WO 92/12182. The contents of this document are included herein
by reference.
[0134] The second component of the composition can be selected from
the group of [0135] (i) maleic anhydride-modified polypropylene
(MAPP) [0136] (ii) maleic anhydride-modified polypropylene wax
[0137] (iii) polypropylene homopolymer with high melt flow rate or
[0138] (iv) ethylene-vinyl acetate-based hot melt adhesive
Ad (i) Maleic Anhydride-Modified Polypropylene (MAPP):
[0138] [0139] The graft modification of polymers with various
olefinically unsaturated monomers is well known in the art and
numerous commercially available graft modified maleic anhydride
polymers are available. [0140] The graft-modified polypropylene (i)
used in the present invention is a polypropylene modified by
partially or wholly grafting with maleic anhydride. [0141] The
propylene used for graft modification is a homopolymer of propylene
and/or a random copolymer of propylene and an alpha-olefin
containing constituent units derived from the alpha-olefin other
than propylene in amounts of not more than 10% by mole based on
100% by mol of the total of constituent units derived from
propylene and constituent units derived from an alpha-olefin other
than propylene. Ethylene and/or an alpha-olefin having 4 to 20
carbon atoms, including 1-butene, 1-pentene, 1-hexene, 1-heptene,
1-octene, 1-nonene, 1-decene and 4-methyl-1-pentene, are used as
the alpha-olefin in the propylene, either singly or in combination
of two or more kinds. [0142] In the propylene/alpha-olefin random
copolymer, constituent units derived from propylene are contained
in amounts of not less than 90% by mol, usually 90 to 99% by mol,
preferably not less than 96% by mol, and constituent units derived
from ethylene or an alpha-olefin of 4 to 20 carbon atoms are
contained in amounts of not more than 10% by mol, usually 1 to 10%
by mol, preferably not more than 6% by mol. [0143] Examples of
propylene/alpha-olefin random copolymers include a
propylene/ethylene copolymer, a propylene/1-butene copolymer, a
propylene/ethylene/1-butene copolymer and a
propylene/ethylene/1-octene copolymer. [0144] Preferably a random
copolymer of propylene with ethylene is used. [0145] The production
method of the polypropylene used for graft modification in the
present invention is not particularly limited. The polypropylene
may be produced by using well-known catalysts such as Ziegler-Natta
catalysts or a metallocene catalyst with well-known processes.
[0146] In the modified polypropylene, a part or the whole of
propylene (a propylene homopolymer or a propylene/alpha-olefin
random copolymer) is graft modified with maleic anhydride in an
amount of preferably 10.sup.-8 to 10.sup.-2 g equivalent, more
preferably 10.sup.-7 to 10.sup.-3 g equivalent, based on 1 g of the
polypropylene before the graft modification. That is, the modified
polypropylene may partly include unmodified polypropylene. When the
modified polypropylene for use in the invention contains unmodified
polypropylene, the content of the unmodified polypropylene is
desired to be not more than 95 parts per weight, usually 85 to 40
parts by weight, based on 100 parts by weight of the total of the
graft modified polypropylene and the unmodified polypropylene.
[0147] The method of graft modification of the propylene with
maleic anhydride is not particularly limited and can be carried out
by well-known graft polymerization methods such as a solvent method
or a melt kneading method. For example, a method of performing
graft reaction by adding the graft monomer maleic anhydride to a
molten polymer or a method of performing graft reaction by
dissolving a polymer in a solvent to make a solution to which the
graft monomer is added may be employed. [0148] When the graft
polymerization is carried out in the presence of a radical
initiator in the above processes, the graft monomer maleic
anhydride can be efficiently graft polymerized. In this case, the
radical initiator is used in an amount of usually 0.001 to 1 part
per weight based on 100 parts per weight of the polypropylene. The
radical initiators used herein are, for example, an organic
peroxide or an azo compound. [0149] Specific examples of the
radical initiators include benzoyl peroxide, lauroyl peroxide,
dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide,
2,5-dimethyl-2,5-di(t-butylperoxide)hexyne-3,
2,5-dimethyl-2,5-di-(t-butylperoxide)-hexane,
1,4-bis(t-butylperoxyisopropyle)benzene, azobisisobutyronitrile,
etc. [0150] The reaction temperature of the graft polymerization
reaction using a radical initiator or the graft polymerization
using no radical initiator is set in the range of usually 60 to
350.degree. C., preferably 150.degree. C. to 300.degree. C. [0151]
The content of the maleic anhydride can be easily controlled, for
example, by suitable selection of the grafting conditions. [0152]
The content of maleic anhydride in the graft-modified polypropylene
used in the present invention is in the range of 0.001 to 10 wt %,
preferably 0.01 to 5 wt %, more preferably 0.02 to 4 wt %. [0153]
The graft modified polypropylene has normally a melt flow rate
(MFR) measured according to ISO 1133 at 230.degree. C. under a load
of 2.16 kg of 0.01 to 1000 g/10 min, preferably 0.1 to 500 g/10
min, more preferably 1.0 to 50 g/10 min. [0154] The anhydride
modified polypropylene used in the present invention is preferably
a modification product obtained by grafting maleic anhydride on a
homopolymer of propylene or a propylene/ethylene random copolymer.
More preferably the MAPP used according to the invention is a
maleic anhydride modified propylene/ethylene random copolymer.
[0155] Examples of commercially available modified polypropylene
products that can suitably be employed in the present invention are
Priex.RTM. 25097 by Solvay, Hercoprime.TM. G-211 by Himont Inc.,
Admer.RTM. AT2059E by Mitsui Chemicals, Bynel.RTM. 50E803 by
DuPont, Exxelor PO 1020 by ExxonMobil, Polybond.RTM. 3200 by
Crompton, Scona.RTM. TPPP 2112 F by Kometra, and the like.
Ad (ii) Maleic Anhydride-Modified Polypropylene Wax
[0155] [0156] Suitable maleic anhydride-modified propylene waxes
include homopolymers of propylene or copolymers of propylene with
ethylene or one or more 1-olefins produced in the presence of a
Ziegler-Natta or metallocene catalyst and subsequently grafted with
maleic anhydride. [0157] 1-olefins used include linear or branched
olefins having 4 to 18 carbon atoms, preferably 4 to 10 carbon
atoms. These olefins may have an aromatic substitution which is in
conjugation with the olefinic double bond. Examples of such
compounds are 1-butene, 1-hexene, 1 octene or 1-octadecen and also
styrene. Preference is given to propylene homopolymers or propylene
copolymers with ethylene. [0158] Especially suitable modified
polypropylene waxes are those having a softening point Ts
(ring/ball) from 85 to 165.degree. C., a melt viscosity, measured
at a temperature 10.degree. C. above Ts, of between 20 and 40 000
mPas, preferably between 50 and 10.000 mPas and a density at
23.degree. C. between 0.89 and 0.96 g/cm.sup.3, preferably between
0.91 and 0.94 g/cm.sup.3. [0159] The weight average molecular
weight (Mw) of the polypropylene waxes used for being grafted is
preferably of less than 10.000 g/mol, more preferably in the range
of 500 to 10.000 g/mol, still more preferably in the range of 1.000
to 9.000 g.mu.mol. [0160] The fraction of the polar graft comonomer
(maleic anhydride), based on grafted polypropylene wax is
preferably 0.1 wt % to 20 wt %. [0161] In a preferred embodiment of
the present invention the grafted polypropylene wax has a high
degree of grafting, i.e. high content of maleic anhydride in the
graft-modified polypropylene wax used in the present invention.
[0162] The acid number of the modified propylene wax is from 0.5 to
120 mg KOH/g, preferably from 1 to 60 mg KOH/g, more preferably
from 2 to 40 mg KOH/g. [0163] The acid number is defined as the
number of milligrams of KOH which are required to neutralize one
gram of sample. Acid numbers were obtained by titrating weighed
samples dissolved in refluxing -xylene with methanolic potassium
hydroxide using phenolphthalein as an indicator. End points were
taken when the pink color of the indicator remained 10 seconds.
[0164] The synthesis of the unmodified, i.e. nonpolar, starting
waxes by means of catalysts of the Ziegler or metallocene type is
known from numerous documents. Thus, for example, DE-A-2329641
discloses a process by means of which .alpha.-olefins can be
polymerized in a direct polymerization reaction using Ziegler
catalysts to give homopolymer or copolymer waxes. DE-A-3148229
describes the preparation of highly crystalline polypropylene waxes
by polymerization likewise using titanium-containing catalysts; the
same in EP-A480190. In addition, propylene homopolymer and
copolymer waxes are also obtainable using metallocene catalysts
(e.g. U.S. Pat. No. 6,331,590, EP-A-321 852, EP-A-384 264, EP-A416
566 or EP 571 882). [0165] Suitable starting materials are low
molecular weight propylene homopolymers prepared using Ziegler or
metallocene catalysts and having melt viscosities, measured at a
temperature 10.degree. C. above Ts, of from 20 to 50 000 mPas. The
softening points (ring/ball) of such waxes are generally from 90 to
165.degree. C. Suitable waxes are both highly crystalline products
having a high proportion of isotactic or syndiotactic structures
and those having a low crystallinity and a predominantly atactic
structure. The degree of crystallinity of propylene homopolymers
can be varied within wide limits in a known manner by appropriate
selection of the catalyst used for the polymerization and by means
of the polymerization conditions. This applies particularly when
using metallocene catalyst systems. [0166] Further suitable
starting materials are propylene copolymer waxes which are prepared
using Ziegler or metallocene catalysts and comprise not only
propylene but also varying amounts of other olefins, for example
ethylene or higher .alpha.-olefins having a chain length range of
C.sub.4-C.sub.30, where the comonomer units can be distributed
either predominantly randomly or predominantly in blocks between
isotactic, syndiotactic or partially atactic polypropylene
sequences. Such waxes have softening points (ring/ball) of
generally from about 90 to 165.degree. C. [0167] Preferably
unmodified polypropylene waxes prepared in the presence of a
metallocene catalyst are used for being grafted with maleic acid.
[0168] The grafting process can be performed as described for
component (i), according to well-known processes. For example,
grafting with maleic anhydride may be performed for example
according to U.S. Pat. No. 5,998,547, U.S. Pat. No. 6,569,950 or EP
0 941 257. [0169] The reaction of the polypropylene wax with maleic
anhydride can be carried out either continuously or batchwise. In
the batchwise procedure, the wax is heated to a temperature above
its softening point and maleic anhydride and a peroxide, as
described above, are introduced into the melt while stirring,
either continuously over an appropriate period of time or in one or
more portions, if desired under a blanket of inert gas. The
reaction temperature is above the softening point of the wax,
preferably from 100 to 200.degree. C., particularly preferably from
130 to 180.degree. C. After metering in is complete, the mixture
can be left to react further at the same temperature or a different
temperature, if desired after addition of a further amount of
peroxide. Volatile components formed during the reaction or excess
volatile starting components can, for example, be distilled off
under reduced pressure or be removed by stripping with inert gas.
[0170] Examples of commercially available modified polypropylene
products that can suitably be employed in the present invention are
Licocene.RTM. PP MA 7452, Licocene.RTM. PP MA 6252 TP,
Licocene.RTM. PP MA 6452, Licocene.RTM. PP MA 1332 TP,
Licocene.RTM. PP MA 1452 all by Clariant, Epolene E-43 by Eastman,
and the like. (iii) Polypropylene Homopolymer with High Melt Flow
Rate [0171] According to the present invention polypropylene
homopolymers with high melt flow rate can also be used as component
B. [0172] The polymers that can be suitably be employed have a melt
flow rate (MFR) measured according to ISO 1133 at 230.degree. C.
under a load of 2.16 kg of from 50 to 3000 g/10 min, preferably
from 100 to 2000 g/10 min, more preferably from 200 to 1500 g/10
min. [0173] The expression homopolymer used in the instant
invention relates to a polypropylene that consists substantially,
i.e. of at least 97 wt %, preferably of at least 99 wt %, and most
preferably of at least 99.8 wt % of propylene units. In a preferred
embodiment only propylene units in the propylene homopolymer are
detectable. The comonomer content can be determined with FT
infrared spectroscopy, as described below in the examples. [0174]
The high melt flow rate polypropylenes used according to the
invention can be produced directly in a polymerization reactor by
well known processes, described in several patent applications (for
example in EP 0 320 150, EP 0 480 190, EP 0 622 380, EP 1 303 547,
EP 1 538 167, EP 1 783 145, WO 2007/140019, etc.). [0175]
Alternatively the high melt flow rate polypropylenes used according
to the invention can be obtained by controlled rheology (CR)
techniques, including, e.g., visbreaking, which means that a
polymer, having low melt flow rate, is subjected to a post-reactor
treatment, wherein the polymer molecules are subjected to
controlled scission in molten state. The scission may be carried
out by mechanical shearing, radiation and oxidation or chemically
with peroxy compounds. [0176] Preferably controlled rheology
treatments are carried out using organic peroxides. [0177] The
process of visbreaking a propylene polymer material is well known
to those skilled in the art and is described in several patent
applications (for example in U.S. Pat. No. 3,940,379, U.S. Pat. No.
4,951,589, U.S. Pat. No. 4,282,076, U.S. Pat. No. 5,250,631, EP 0
462 574, WO 02/096986, WO 2004/113438 [0178] The polymer used as
starting compound for the controlled rheology treatment may be
produced by any polymerisation process known in the art. [0179] The
polymerisation process may be a continuous process or a batch
process utilising known methods and operating in liquid phase,
optionally in the presence of an inert diluent, or in gas phase or
by mixed liquid-gas techniques. The process is preferably carried
out in the presence of a stereospecific catalyst system. [0180] As
catalyst any ordinary stereospecific Ziegler-Natta catalysts or any
metallocene catalyst capable of catalysing the formation of a
propylene polymer can be used. [0181] In addition, examples of
commercially available modified polypropylene products that can
suitably be employed in the present invention are Borflow.TM.
.mu.L504FB, HL508FB or HL512FB all by Borealis, Metocene MF650 by
Basell Polyolefins, Marlex.RTM. HGZ-1200 by Phillips Sumika
Polypropylene Company, Escorene.TM. PP3505 and PP3746 all by
ExxonMobile, EOD 96-36 and 3960X by Fina, Valtec grades like
HH442H, HH441, PF008, PF017, etc. by LyondellBasell etc.
(iv) Ethylene-Vinyl Acetate-Based Hot Melt Adhesive
[0181] [0182] A hot melt adhesive is generally manufactured from a
mixture of three components: a thermoplastic resin, a tackifying
agent, and paraffin or a microcrystalline polymeric wax. The
thermoplastic resins commonly used in compositions for the
manufacture of hot melt adhesives have included copolymers of
ethylene and vinyl esters, particularly vinyl acetate, or
copolymers of ethylene and alkyl acrylates, particularly ethyl
acrylate and butyl acrylate. [0183] According to the present
invention hot melt adhesives based on ethylene-vinyl acetate
copolymers can be used as component B [0184] Various formulations
including ethylene-vinyl acetate (EVA) copolymers are known in the
art. [0185] Ethylene-vinyl acetate (EVA) copolymers are
conventionally regarded as those copolymers of ethylene and vinyl
acetate where the weight percentage of ethylene in the polymer
molecule exceeds that of the vinyl acetate. [0186] The
ethylene-vinyl acetate copolymers (EVA) useful herein are those
containing at least about 15 to 45 wt % vinyl acetate and having a
melt index (ISO 1133, 190.degree. C., 2.16 kg) in the range of 2 to
2500 g/10 min. The EVA copolymers will preferably comprise less
than 40 weight percent vinyl acetate (VA), although EVA copolymers
are nowadays available with a vinyl acetate content of above 50 wt
% [0187] Useful commercially available ethylene-vinyl acetate
copolymers are for example ATEVA.RTM. grades from AT Plastics Inc.,
Brampton, Ontario, Escruene.RTM. grades from ExxonMobile,
Elvax.RTM. grades from Dupont, Evatane.RTM. grades, for example
supplied by Atofina, and the like. [0188] Useful commercially
available hot melt adhesives based on ethylene-vinyl acetate
copolymers that can suitably be employed in the present invention
are for example Sitomelt.RTM. grades like K 60811 from Kiilto OY,
Quicklock Hotmelt CH 155 supplied by Chemline India Ltd., 3M.TM.
Jet-melt.TM. hot melt adhesive grades, etc.
[0189] The two component adhesion compositions according to the
present invention comprise a) 70 to 98 wt % of component (A),
described in detail above and b) 2 to 30 wt % of component (B),
described in detail above.
[0190] Preferably the two component adhesion compositions according
to the present invention comprise a) 75 to 95 wt % of component (A)
and b) 5 to 25 wt % of component (B).
[0191] As component (B) preferably one compound selected from the
group of [0192] (i) maleic anhydride-modified polypropylene (MAPP)
[0193] (ii) maleic anhydride-modified polypropylene wax or [0194]
(iv) ethylene-vinylacetat based hot melt adhesive all described in
detail above, is used.
[0195] More preferably component (B) is (i) a maleic
anhydride-modified polypropylene (MAPP) or (ii) a maleic
anhydride-modified polypropylene wax and still more preferably
component (B) is a maleic anhydride-modified polypropylene wax.
[0196] The adhesive composition in accordance with the present
invention may furthermore comprise small amounts of additional,
conventional components (additives), commonly used and well known
in the adhesive art. The type and amount of such additives can be
selected by the skilled person on the basis of the general
knowledge in the art. Typically these additive do not amount to
more than 5 wt.-% (in total), based on the adhesive
composition.
[0197] The adhesive composition may be prepared in a usual manner,
including blending the individual components using appropriate
devices, such as kneaders and extruders.
[0198] Thus the highly adhesive composition of the present
invention may be prepared by mixing the two components and
optionally one or more additives, as described above, to form a
blend and then melt kneading the resulting mixture.
[0199] The melt-kneading may be carried out using a kneading
machine, such as a mixing roll, a Branbury mixer, a kneader, or a
single-screw or twin-screw extruder.
[0200] The adhesive composition according to the present invention
has particular utility as a coating for paper substrates.
[0201] Any types of papers conventionally known in the art for
preparing coated papers can be used, such as but not limited to
kraft paper, natural or synthetic pulp paper, paper board, liner
board and the like. The paper may further be bleached and/or
coated.
[0202] The adhesive composition in accordance with the present
invention is in particular suitable for coating by extrusion
processes.
[0203] The extrusion coating process may be carried out using
conventional extrusion coating techniques.
[0204] Hence, the adhesive composition according to the present
invention is fed, typically in the form of pellets, optionally
containing additives, to an extruding device. From the extruder the
polymer melt is passed preferably through a flat die to the
substrate to be coated. Due to the distance between the die lip and
the nip, the molten plastic is oxidized in the air for a short
period, usually leading to an improved adhesion between the coating
and the substrate. The coated substrate is cooled on a chill roll,
after which it is passed to edge trimmers and wound up. The width
of the line may vary between, for example, 500 to 1500 mm, e.g. 800
to 1100 mm, with a line speed of up to 1000 m/min, for instance 300
to 800 m/min. The temperature of the polymer melt is typically
between 275 and 330.degree. C. The polypropylene of the invention
can be extruded onto the substrate as a monolayer coating or as one
layer in coextrusion. In a multilayer extrusion coating, the other
layers may comprise any polymer resin having the desired properties
and processability.
[0205] Therefore, a further object of the invention is the use of
the polypropylene composition in extrusion coating processes using
paper, as defined above, as substrate.
[0206] The composition of the present invention is highly adhesive
and thus none of the methods commonly known in the art to improve
adhesion between the paper substrate and the polypropylene layer
produced from the composition according to the invention, such as
ozone treatment of the molten polymer film, corona treatment of the
substrate and use of a coextruded adhesion layer need to be
applied.
[0207] Nevertheless it is possible to perform ozone and/or corona
treatment in a know way, if desired or necessary.
[0208] The main end-uses for extrusion coated products obtained by
using the adhesive composition according to the invention are in
packaging applications, like liquid packaging for milk, juice, wine
or other liquids, flexible packaging for meat, cheese and medical
products, rigid packaging like detergent cartons, cup and plate
boards for oven or microwave use or sterilizable food packaging,
but also for photographic paper or industrial applications like
paper reel and ream wraps.
[0209] The present invention, as outlined above, therefore also
provides a substrate, respectively article which has at least one
layer of highly adherent propylene polymer composition according to
the invention on at least one surface.
[0210] Furthermore the present invention is also directed to the
use of the inventive article as packaging material, in particular
as a packaging material for food and/or medical products.
[0211] In the following, the present invention is described by way
of examples.
DEFINITIONS/MEASURING METHODS
[0212] The following definitions of terms and determination methods
apply for the above general description of the invention as well as
to the below examples unless otherwise defined.
[0213] Number average molecular weight (M.sub.n), weight average
molecular weight (M.sub.w) and molecular weight distribution (MWD)
are determined by size exclusion chromatography (SEC) using Waters
Alliance GPCV 2000 instrument with online viscometer. The oven
temperature is 140.degree. C. Trichlorobenzene is used as a solvent
(ISO 16014).
[0214] In detail: The number average molecular weight (M.sub.n),
the weight average molecular weight (M.sub.w) and the molecular
weight distribution (MWD) are measured by a method based on ISO
16014-1:2003 and ISO 16014-4:2003. A Waters Alliance GPCV 2000
instrument, equipped with refractive index detector and online
viscometer was used with 3.times.TSK-gel columns (GMHXL-HT) from
TosoHaas and 1,2,4-trichlorobenzene (TCB, stabilized with 200 mg/L
2,6-Di tert butyl-4-methyl-phenol) as solvent at 145.degree. C. and
at a constant flow rate of 1 mL/min. 216.5 .mu.L of sample solution
were injected per analysis. The column set was calibrated using
relative calibration with 19 narrow MWD polystyrene (PS) standards
in the range of 0.5 kg/mol to 11 500 kg/mol and a set of well
characterized broad polypropylene standards. All samples were
prepared by dissolving 5-10 mg of polymer in 10 mL (at 160.degree.
C.) of stabilized TCB (same as mobile phase) and keeping for 3
hours with continuous shaking prior sampling in into the GPC
instrument.
Melt Strength and Melt Extensibility by Rheotens Measurement:
[0215] The strain hardening behaviour of polymers is analysed by
Rheotens apparatus (product of Gottfert, Siemensstr. 2, 74711
Buchen, Germany) in which a melt strand is elongated by drawing
down with a defined acceleration. The haul-off force F in
dependence of draw-down velocity v is recorded.
[0216] The test procedure is performed in a standard climatised
room with controlled room temperature of T=23.degree. C. The
Rheotens apparatus is combined with an extruder/melt pump for
continuous feeding of the melt strand. The extrusion temperature is
200.degree. C.; a capillary die with a diameter of 2 mm and a
length of 6 mm is used and the acceleration of the melt strand
drawn down is 120 mm/s.sup.2. The maximum points (F.sub.max;
v.sub.max) at failure of the strand are characteristic for the
strength and the drawability of the melt.
[0217] Intrinsic viscosity: is measured according to DIN ISO
1628/1, October 1999 (in Decalin at 135.degree. C.).
[0218] The crosslinked fraction is assumed to be identical to the
xylene hot insoluble (XHI) fraction, which is determined by
extracting 1 g of finely cut polymer sample with 500 ml xylene in a
Soxleth extractor for 48 hours at the boiling temperature. The
remaining solid amount is dried at 90.degree. C. and weighed for
determining the insolubles amount.
Adhesion
[0219] Peel resistance (adhesive bond strength) was determined with
the T-Peel Test according to ASTM 0 1876-01 using an Instron 4502
tensile tester.
[0220] Test samples: extrusion coated UG kraft paper; 5 pieces, cut
in machine direction, 25.4.times.150 mm. Samples were conditioned
for one day at a relative humidity of 50.+-.2% at 23.+-.1.degree.
C.
[0221] The layers were separated at the desired interface, placed
to the arms of the tensile tester and the force required to pull
the layers apart was measured. The result was the force needed for
peeling given in N/cm (peel strength in terms of load per unit
width of bond line) The peeling types are defined as "fiber-tear"
(if the propylene composition film being extrusion coated onto the
paper substrate is separated from that paper takes fibers with it,
meaning extremely good adhesion; e.g. cohesive failure in paper) or
"no fibers" (no fibers are taken; pure peeling)
EXAMPLES
Materials used
[0222] Component (A): Daploy.TM. WF420HMS (High melt strength
polypropylene homopolymer; Borealis) [0223] Component (B): [0224]
(i) Priex.RTM. 25097 (Maleic anhydride grafted polypropylene random
copolymer; Solvay Plastics) [0225] (ii) Licocene.RTM. PP MA 7452
(Maleic anhydride grafted polypropylene wax, based on metallocene
technology) [0226] (iii) BorFlow.TM. HL504FB (polypropylene
homopolymer with MFR of 450 g/10 min, according to ISO 1133,
230.degree. C., 2.16 kg; Borealis) [0227] iv) Sitomelt K608/1 (EVA
based hot melt adhesive, Kiilto OY) [0228] (v) Primacor.TM. 3440
(ethylene acrylic acid copolymer, Dow) was used in a comparative
example
Example 1
Preparation of Blends of Component (A) with Component (B)
[0229] The compositions were formulated by dry mixing the above
described commercially available starting materials together and
then melt-blended. 90 to 95 wt % of WF420HMS were mixed with 5 to
10 wt % of one of the components (B).
[0230] For the Beloit line extrusion coating, the melt-blending was
carried out in a Werner&Pfleiderer ZSK40 twin-screw extruder at
a temperature of 200 to 240.degree. C. (Screw speed was 500 rpm,
output was 50 kg/h)
[0231] The polymer melt strings from extruder were cooled down in a
water bath and dried with air and cut into pellets.
[0232] For the Demaq line extrusion coating, the melt blending was
done in a compounder BESL 10, Berstorff ZE 25 with capacity of 5-10
kg/h. It has co-rotating twin-screws, with L/D ratio 40/25.
Starting materials were weighted and dry mixed together before
taking them to extruder for melt blending. Set value for melt
temperature was 200.degree. C. and temperature profile was
195-200-200-200-200-200-200-200, blending was done under nitrogen
flush. Set value for screw speed was 200 RPM and for feeders 7
kg/h. The polymer melt strings from extruder were cooled down in a
room-temperature water bath and dried with air and cut into
pellets.
Example 2-7
[0233] Extrusion coating runs were made on Beloit coextrusion
coating line. Beloit line had Extruders 1&2 with size of 4,5''
and L/D 24; output was 450 kg/h (for LOPE) and Extruder 3 in size
of 2,5'' and L/D 30; output was 170 kg/h. It had a Peter Cloeren's
die and a five layer feed block. The width of the line was 600-800
mm and the maximum line speed was 1000 m/min (design value).
[0234] In the coating line above a UG kraft paper (UPM Prime Wrap)
having a basis weight of 70 g/m.sup.2 was coated with a co-extruded
structure, which was composed of 20 g/m.sup.2 of WF420HMS on the
top layer and 20 g/m.sup.2 of WF420HMS respectively of blends
prepared according to Example 1 in the layer against paper.
Together all coatings had a basis weight of 40 g/m.sup.2. The
temperature of the polymer melt was set to 290.degree. C. and the
extruders' temperature profile was 200-240-290-290.degree. C. The
chill roll was matt and temperature of its surface was 15.degree.
C. Used die opening was 0.65 mm and nip distance was 160 mm. Melt
film touched the substrate for the first time+10 mm from nip to
substrate side. Pressure of the pressure roll was 3.0 kp/cm.sup.2.
The line speed was 100 m/min.
[0235] 5 test samples (25.4.times.150 mm) of WF420HMS coated paper,
as well as of WF420 HMS-blend coated paper were tested regarding
adhesion by the T-Peel Test according to ASTM D 1876 on an Instron
Tensile Tester.
[0236] Results are summarized in Table 1:
TABLE-US-00001 TABLE 1 Adhesion Test - no pre-treatments Coating
material Component(A)/(B) Load Load/width Improvement Example [wt
%] [N] s.d. [N/cm] s.d. [%] 2 WF420HMS[100] 0.73 0.04 0.29 0.016 0
3 WF420HMS[90]/ 1.56 0.118 0.61 0.046 113 Priex 25097[10] 4
WF420HMS[95]/ 1.71 0.077 0.67 0.030 134 Licocene PP MA 7452 [5] 5
WF420HMS[90]/ 0.91 0.083 0.36 0.033 24 BorFlow HL504FB [10] 6
WF420HMS[90]/ 1.05 0.048 0.41 0.019 43 Sitomelt K608/1 [10] 7
WF420HMS[90]/ 0.47 0.048 0.19 0.019 -35 Primacor 3440 [10] Example
7 is a Comparative Example s.d. standard deviation All samples
showed pure peeling, "no fiber" peeling type Improvement in % is
compared to the adhesion value of Example 2 (pure WF420HMS).
Example 8
[0237] Extrusion coating runs were made on Beloit coextrusion
coating line as described for Examples 2-7.
[0238] in the coating line above a UG kraft paper (UPM Prime Wrap)
having a basis weight of 70 g/m.sup.2 was coated with a co-extruded
structure, which was composed of 20 g/m.sup.2 of WF420HMS on the
top layer and 20 g/m.sup.2 of WF420HMS respectively of blends,
prepared according to Example 1, in the layer against paper.
Together all coatings had a basis weight of 40 g/m.sup.2. The
temperature of the polymer melt was set to 290.degree. C. and the
extruders' temperature profile was 200-240-290-290.degree. C. The
chill roll was matt and temperature of its surface was 15.degree.
C. Used die opening was 0.65 mm and nip distance 160 mm. Melt film
touched the substrate for the first time+10 mm from nip to
substrate side. Pressure of the pressure roll was 3.0 kp/cm.sup.2.
The line speed was 100 m/min.
[0239] Ozone treatment for the melt (Sherman) and Corona treatment
for the substrate (Vetaphone) have been employed for all samples.
Sherman ozone treater had a maximum output power of 4.0 kW and
ozone concentration around 30 g/m.sup.3. Set point for ozone was
2.6 kW and thus concentration of ozone was 19-20 g/m.sup.3.
Applicator's distance and angle from molten film was 70 mm and
45.degree., Vetaphone ET5 corona treater had a output power of 12
kW and frequency of 18 to 35 kHz. It had an HF-amplifier with
output voltage of 15 to 25 kV and multi-profile aluminium
electrode. Set point for used corona was 12.0 kW.
[0240] 5 test samples (25.4.times.150 mm) of WF420HMS coated paper,
as well as of WF420 HMS-blend coated paper were tested regarding
adhesion by the T-Peel Test according to ASTM D 1876 on an Instron
Tensile Tester.
[0241] Results are summarized in Table 2:
TABLE-US-00002 TABLE 2 Adhesion Test - ozone and corona
pre-treatment Coating material Component(A)/(B) Load Load/width
Improvement Example [wt %] [N] s.d. [N/cm] s.d. [%] 8 WF420HMS[100]
2.10 0.109 0.83 0.043 0 9 WF420HMS[90]/ 2.33 0.106 0.92 0.042 10
Priex 25097[10] 10 WF420HMS[95]/ 3.51 0.438 1.38 0.173 66 Licocene
PP MA 7452 [5] 11 WF420HMS[90]/ 2.11 0.181 0.83 0.071 0 BorFlow
HL504FB [10] 12 WF420HMS[90]/ 3.64 0.803 1.43 0.316 72 Sitomelt
K608/1 [10] 13 WF420HMS[90]/ 1.99 0.093 0.78 0.037 -6 Primacor 3440
[10] Example 13 is a Comparative Example s.d. standard deviation
Samples 8-11 and sample 13 showed "fiber-tear" peeling type, e.g.
cohesive failure in the paper For Sample 12 the failure was
"fiber-tear" for 2 of 5 pieces and "no fiber" for 3 of 5 pieces.
Improvement in % is compared to the adhesion value of Example 8
(pure WF420HMS).
Example 14-19
[0242] Extrusion coating runs were made on a Demag coating line. It
was a cast film line adapted to extrusion coating. The nip
configuration differed from conventional extrusion coating line's
horizontal die placing by the die being in 45.degree. angle from
horizontal direction; however the molten film was coming to the nip
tangential to chill roll as normally. Demaq line had an extruder
with L/D ratio 45/31 and maximum output was 60 kg/h. There were no
back pressure valves in Demaq. The die was a Ultraflex R75 450 mm
(Extrusion Dies Inc.). The maximum width of the paper roll for the
line was 420 mm and the maximum line speed was 200 m/min (design
value). Chill roll was glossy and maximum pressure for pressure
roll was 6 bar.
[0243] In the coating line above a UG kraft paper (UPM Prime Wrap)
having a basis weight of 70 g/m.sup.2 was coated in monolayer
structures with a layer of WF420HMS, respectively of blends,
prepared according to Example 1, all having a basis weight of 40
g/m.sup.2. The temperature of the polymer melt was set to
290.degree. C. The line speed was 20 m/min. Die opening was 0.5 mm,
nip distance 170 mm and nip pressure 6 bar.
[0244] 5 test samples (25.4.times.150 mm) of WF420HMS coated paper,
as well as of WF420 HMS-blend coated paper were tested regarding
adhesion by the T-Peel Test according to ASTM D 1876 on an Instron
Tensile Tester.
[0245] Results are summarized in Table 3:
TABLE-US-00003 TABLE 3 Adhesion Test - no pre-treatments Coating
material Component(A)/(B) Load Load/width Improvement Example [wt
%] [N] s.d. [N/cm] s.d. [%] 14 WF420HMS[100] 1.426 0.216 0.56 0.085
0 15 WF420HMS[90]/ 1.916 0.145 0.75 0.057 34 Priex 25097[10] 16
WF420HMS[90]/ 4.986 0.235 1.956 0.093 249 Licocene PP MA 7452 [10]
17 WF420HMS[90]/ 1.901 0.217 0.75 0.086 33 BorFlow HL504FB [10] 18
WF420HMS[90]/ 1.927 0.123 0.76 0.049 35 Sitomelt K608/1 [10] 19
WF420HMS[90]/ 1.132 0.198 0.45 0.078 -21 Primacor 3440 [10] Example
19 is a Comparative Example s.d. standard deviation Improvement in
% is compared to the adhesion value of Example 14 (pure
WF420HMS).
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