U.S. patent application number 12/914183 was filed with the patent office on 2011-02-17 for polymer concentrates with improved processability.
Invention is credited to Andre Damman, Stephen Pask, Stephan Schroeder.
Application Number | 20110040008 12/914183 |
Document ID | / |
Family ID | 38125016 |
Filed Date | 2011-02-17 |
United States Patent
Application |
20110040008 |
Kind Code |
A1 |
Pask; Stephen ; et
al. |
February 17, 2011 |
POLYMER CONCENTRATES WITH IMPROVED PROCESSABILITY
Abstract
New polymer concentrates on the basis of polymer additives, like
e.g. fillers and flame-retardants, are provided which have in
particular an increased bulk density compared to the polymer
additives as such. This increased bulk density leads to a
substantial improvement in the processability of such concentrates,
their dispersibility during compounding and the properties of the
resulting polymer compound. Processing improvements include less
dust, faster processing and more homogeneous additive dispersion.
The invention also provides a process for preparing such new
polymer concentrates, a process for preparing polymer compounds
containing the new polymer concentrates, the respective polymer
compounds and a process for preparing formed parts thereof. Such
formed parts have more uniform properties such as density, wall
thickness, and in case of the flame-retardants more homogeneous and
consistent flame retardancy.
Inventors: |
Pask; Stephen; (Dormagen,
DE) ; Damman; Andre; (Leverkusen, DE) ;
Schroeder; Stephan; (Leverkusen, DE) |
Correspondence
Address: |
LANXESS CORPORATION
111 RIDC PARK WEST DRIVE
PITTSBURGH
PA
15275-1112
US
|
Family ID: |
38125016 |
Appl. No.: |
12/914183 |
Filed: |
October 28, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11602779 |
Nov 21, 2006 |
7846996 |
|
|
12914183 |
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Current U.S.
Class: |
524/405 ;
524/409; 524/410; 524/413; 524/425; 524/431; 524/436; 524/437;
524/445; 524/449; 524/451; 524/502; 524/521; 524/524; 524/563 |
Current CPC
Class: |
C08J 3/226 20130101;
C08J 2431/00 20130101 |
Class at
Publication: |
524/405 ;
524/563; 524/437; 524/436; 524/409; 524/410; 524/451; 524/449;
524/445; 524/425; 524/431; 524/413; 524/502; 524/521; 524/524 |
International
Class: |
C08L 31/04 20060101
C08L031/04; C08K 3/22 20060101 C08K003/22; C08K 3/38 20060101
C08K003/38; C08K 3/10 20060101 C08K003/10; C08K 3/34 20060101
C08K003/34; C08K 3/26 20060101 C08K003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 2005 |
EP |
05025846.6 |
Claims
1. A concentrate containing (1) one or more polymer additives and
(2) one or more polymers which comprise repeating units of
ethylene, vinyl acetate and optionally one or more other monomers,
wherein (a) the concentrate contains less than 10% by weight of one
or more polymers (2), based on the total weight of the polymer
additive(s) (1) and the polymer(s) (2), (b) the concentrate is
obtainable by mixing the polymer additive(s) (1) with a solution of
the polymer(s) (2) in a solvent and removing the solvent, (c) the
mean primary particle size ("d.sub.50") of the polymer additive(s)
(1) prior to the mixing with the solution of the polymer(s) (2) is
less than 10 .mu.m, and (d) the concentrate has a bulk density
which is at least 50% greater than that of the polymer additive(s)
(1) prior to the mixing with the solution of the polymer(s) (2),
wherein such bulk density is measured in accordance with DIN ISO
697 from January 1984.
2. The concentrate according to claim 1, wherein the mean primary
particle size ("d.sub.50") of the polymer additive(s) (1) prior to
the mixing with the solution of the polymer(s) (2) is less than 5
.mu.m.
3. The concentrate according to claim 1, wherein the mean primary
particle size ("d.sub.50") of the polymer additive(s) (1) prior to
the mixing with the solution of the polymer(s) (2) is less than 2
.mu.m.
4. The concentrate according to claim 1, wherein the mean primary
particle size ("d.sub.50") of the polymer additive(s) (1) prior to
the mixing with the solution of the polymer(s) (2) is in the range
of from 0.5-1.5 .mu.m.
5. The concentrate according to claim 1, wherein the polymer
additives (1) are fillers, flame-retardants, flame-retardant
synergists, pigments, other finely powdered polymer additives or
any mixtures thereof.
6. The concentrate according to claim 5, wherein a mixture of a
filler and a flame-retardant or a mixture of a filler, a
flame-retardant, and a flame-retardant synergist is used.
7. The concentrate according to claim 5 or 6, wherein as
flame-retardants aluminium trihydroxide (ATH), magnesium hydroxide,
antimony trioxide, or mixtures thereof are used.
8. The concentrate according to claim 5 or 6, wherein as
flame-retardant synergists zinc borate, antimony trioxide, sodium
antimonate, or mixtures thereof are used.
9. The concentrate according to claim 5 or 6, wherein as fillers
carbon black, graphite, metal powders, talc, clays, mica,
wollastonite, silica, calcium carbonate, hydrated minerals,
boron-containing compounds, zinc-containing compounds,
antimony-containing compounds, or mixtures thereof are used.
10. The concentrate according to claim 5, wherein as pigments iron
oxides or titanium dioxide are used.
11. The concentrate according to claim 1, wherein the polymer(s)
(2) contain 40 to 90% by weight vinyl acetate and 10 to 60% by
weight ethylene and optionally 10 to 50% by weight of one or more
further monomers, wherein the sum of all monomers in the polymer(s)
(2) still has to give 100% by weight.
12. The concentrate according to claim 1, wherein the polymer(s)
(2) contain 60 to 80% by weight vinyl acetate and 20 to 40% by
weight ethylene and optionally 10 to 50% by weight of one or more
further monomers, wherein the sum of all monomers in the polymer(s)
(2) still has to give 100% by weight.
13. The concentrate according to claim 1, wherein the concentrate
contains 2 to 10% by weight of one or more polymers (2), based on
the total weight of the polymer additive(s) (1) and the polymer(s)
(2).
14. The concentrate according to claim 1, wherein the concentrate
contains 3 to 8% by weight of one or more polymers (2), based on
the total weight of the polymer additive(s) (1) and the polymer(s)
(2).
15. The concentrate according to claim 1, wherein the concentrate
contains 3 to 6% by weight of one or more polymers (2), based on
the total weight of the polymer additive(s) (1) and the polymer(s)
(2).
16. A method for preparing polymer compounds comprising mixing a
concentrate according to claim 1 with one or more polymers (3).
17. The method according to claim 16, wherein as polymers (3)
nitrile rubber ("NBR"), hydrogenated nitrile rubber ("HNBR"),
polyamides, polycarbonate, polyvinylchloride ("PVC"), AEM or EVM
are used.
18. A polymer compound comprising the concentrate according to
claim 1 and one or more polymer(s) (3).
19. The polymer compound according to claim 18 comprising as
polymers (3) nitrile rubber ("NBR"), hydrogenated nitrile rubber
("HNBR"), polyamides, polycarbonate, polyvinylchloride ("PVC"), AEM
or EVM.
20. A process for preparing formed parts containing a polymer
compound comprising processing the concentrate according to claim 1
with one or more polymer(s) (3).
21. Formed parts of the polymer compounds according to claim
19.
22. Formed parts according to claim 21 which are profiles,
equipment housings, or functional articles.
23. Formed parts according to claim 22 which are sealing profiles
or window profiles, equipment housings for computers, household or
industrial electrical equipment, hoses or belts.
Description
[0001] This application claims the benefit of European Application
No. 05025846.6 filed Nov. 26, 2005. This application is a
Divisional of U.S. patent application Ser. No. 11/602,779 filed
Nov. 21, 2006, currently pending, entitled "New Polymer
Concentrates with Improved Processability", the contents of which
are hereby incorporated by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to new polymer concentrates
containing (1) one or more polymer additive(s) and (2) one or more
polymer(s) which comprise repeating units of ethylene, vinyl
acetate and optionally one or more other monomers. The invention
also relates to a process for preparing such new polymer
concentrates, a process for preparing polymer compounds comprising
the new polymer concentrates, the resulting polymer compounds, a
process for preparing formed parts thereof and the formed
parts.
BACKGROUND OF THE INVENTION
[0003] Mineral hydroxides are an important class of polymer fillers
used in particular as flame retardants. Aluminium trihydroxide and
magnesium dihydroxide are the major examples of this class of
fillers. However, these hydroxides as well as other finely powdered
polymer fillers or additives present problems in handling and
particularly in compounding into polymers. Ideally, a finer
particle size of solid polymer additives should lead to better
dispersion in the polymer matrix, and better dispersion equates to
more efficient, uniform performance and improved polymer physical
properties. Therefore, the solid polymer additives often have
particle sizes reduced to less than 10 .mu.m. On the other hand,
finer particles are often more difficult to disperse and problems
of reagglomeration occur.
[0004] Additionally the general handling of finely powdered polymer
additives presents particular problems. One substantial problem of
finely powdered polymer additives is dusting. The creation of dust
involves loss of raw material, increased clean-up costs, and health
concerns for those handling the solids.
[0005] Another problem is bulk density. Finer solids tend to have
decreased bulk density and increased packaging size, volume and
cost. The fluffy nature and low bulk density of finely powdered
polymer additive solids adversely affects additive flow properties,
making them more difficult to meter when using continuous
compounding equipment, such as twin screw extruders, but also
making general handling difficult. More specifically, poor solids
mixing homogeneity results in poor performance in general, for
example poor physical properties in the final product. Finer solids
tend to lead to, for example, poor physical properties in the final
product.
[0006] One prior art approach to increasing the mixing homogeneity
in the addition of low bulk density solids to polymers involves
adding a liquid, such as a plasticizer, to the powder, prior to
mixing the powder with the polymer.
[0007] Blending the additive powder into the polymer in the form of
a masterbatch concentrate that can be diluted with more polymer to
achieve the desired final concentration of powder additive is a
further common approach. It decreases dusting during the ultimate
polymer processing step. However, it not only adds a costly
additional step, but it also does not deal with the problem of poor
mixing of a low bulk density additive powder and a polymer in
forming the masterbatch concentrate. In fact, the masterbatch
sometimes has poorer homogeneity because a higher proportion of
incompatible fine powder is added. This method also has a
disadvantage for fillers which are used in substantially larger
amounts, such as flame retardants, due to the large amount of
polymer carrier that is included in the final compound.
[0008] The approach described in U.S. Pat. No. 4,849,134 to solving
these problems is cold compaction of the filler. The disadvantage
of this method is that compaction (re-)agglomerates the fine
particles of the additive. Unless subsequent polymer processing
conditions result in complete breakup of the coarse compacted, i.e.
agglomerated particles and dispersion into the polymer, any
advantage of the fine particles is lost.
[0009] The aim of increasing the bulk density of fine polymer
fillers and in particular flame retardants, flame retardant
synergists, blends thereof, and other powdered polymer additives
has significant value. These additives are included in an amount of
about 1% by weight to about 60% by weight, often 10-40% by weight,
into a finished polymeric article.
[0010] Certain advantages of a lower bulk density polymer additive
upon processing of one polymer, PVC, are referred to in U.S. Pat.
No. 3,567,669. This patent discloses a high speed mixing process
which requires a temperature of at least 170.degree. F. Under these
conditions, the PVC particles have a slightly sintered or glazed
surface. Solid additives are absorbed or adsorbed onto the polymer
surface.
[0011] U.S. Pat. No. 3,663,674 discloses densification of
poly-.alpha.-olefins. Such poly-.alpha.-olefins are prepared in a
dense granular form suitable for moulding or extrusion by the
application of sufficient mechanical energy to compress and
collapse the porous polymer particles recovered from the
polymerisation reactor. Cited advantages of increased bulk density
are improved handling characteristics and the lack of a thermal
history prior to processing. No mention is made of the effect of
the bulk density of powdered additives upon the processability or
properties of the polymer. Nor is there any mention of the use of
flame retardants or flame retardant synergists.
[0012] Based upon the teachings of the U.S. Pat. No. 3,567,669 and
U.S. Pat. No. 3,663,674 it was therefore the object of the present
invention to provide new concentrates of polymer additives, in
particular fillers and flame-retardants, and polymers which new
concentrates possess an enhanced processability, show an improved
dispersability of the additive throughout the polymer and
eventually result in improved properties of the formed parts
prepared by processing polymer compounds containing the new
concentrates.
SUMMARY OF THE INVENTION
[0013] The present invention is directed to a concentrate
containing [0014] (1) one or more polymer additives and [0015] (2)
one or more polymers which comprise repeating units of ethylene,
vinyl acetate and optionally one or more other monomers, wherein
[0016] (a) the concentrate contains less than 10% by weight of one
or more polymers (2), based on the total weight of the polymer
additive(s) (1) and the polymer(s) (2), and [0017] (b) the
concentrate is obtainable by mixing the polymer additive(s) (1)
with a solution of the polymer(s) (2) in a solvent and removing the
solvent, [0018] (c) the mean primary particle size ("d.sub.50") of
the polymer additive(s) (1) prior to the mixing with the solution
of the polymer(s) (2) is less than 10 .mu.m and [0019] (d) the
concentrate has a bulk density which is at least 50% greater than
that of the polymer additive(s) (1) prior to the mixing with the
solution of the polymer(s) (2), wherein such bulk density is
measured in accordance with DIN ISO 697 from January 1984.
[0020] The present invention is further directed to a process for
preparing the concentrates by mixing the polymer additives (1) with
a solution of the polymer(s) (2) and removing the solvent.
[0021] Eventually the present invention is directed to the use of
the inventive concentrates for preparing polymer compounds, to a
process for preparing polymer compounds comprising the
concentrates, a process for preparing formed parts on the basis of
such polymer compounds and the formed parts.
BRIEF DESCRIPTION OF DRAWINGS
[0022] For a fuller understanding of the nature and advantages of
the present invention, reference should be had to the following
detailed description taken in connection with the accompanying
drawings, in which:
[0023] FIG. 1: is a chart of the particle size distributions for
Examples 2b to 2f.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The polymer additive(s) (1) used to prepare the inventive
concentrates have a finely powdered form. The mean primary particle
size (also abbreviated as "d.sub.50") of the polymer additive(s)
(1) prior to subjecting the polymer additive(s) (1) to the
preparation of the inventive concentrate is less than 10 .mu.m,
preferably less than 5 .mu.m, particularly preferred less than 2.5
.mu.m.
[0025] The term "mean primary particle size" ("d.sub.50") means
that at least 50% of the polymer additive particles have a particle
size less than 10 .mu.m, preferably less than 5 .mu.m, and
particularly preferred less than 2 .mu.m, and most preferably
0.5-1.5 .mu.m. This mean primary particle size is typically
measured by laser diffraction e.g. by using a Malvern Mastersizer
S.
[0026] The polymer additives (1) which may be used to prepare the
inventive concentrates may be e.g. fillers, flame-retardants,
flame-retardant synergists, pigments or other finely powdered
polymer additives or any mixtures thereof. This includes mixtures
of different types of polymer additives (1) may be used, e.g. a
mixture of a filler and a flame-retardant or a mixture of a filler,
a flame-retardant, and a flame-retardant synergist. Such polymer
additives (1) are known and commercially available. Usually it is
not necessary to further reduce the particle size of the polymer
additives (1) available.
[0027] As flame-retardants aluminium trihydroxide (ATH), magnesium
hydroxide, antimony trioxide, or mixtures thereof are e.g.
suitable.
[0028] As flame-retardant synergists zinc borate, antimony
trioxide, sodium antimonate, or mixtures thereof are suitable to
additionally enhance the efficiency of the flame-retardant
itself.
[0029] Suitable fillers subjected to the preparation of the
inventive concentrates include carbon black, graphite, metal
powders, talc, clays, mica, wollastonite, silica, calcium
carbonate, hydrated minerals, boron-containing compounds,
zinc-containing compounds, antimony-containing compounds, and
mixtures thereof.
[0030] As pigments which can also be used in the present invention
for example iron oxides and titanium dioxide are mentioned.
[0031] The polymer(s) (2) used to prepare the inventive
concentrates comprise repeating units of ethylene, vinyl acetate
and optionally one or more other monomers. Such polymers are
commercially available and are typically produced by radical
initiated polymerisation of ethylene, vinyl acetate and optionally
one or more other monomers. Some commercial materials may also
contain minor amounts of a third monomer such as acrylic acid or
esters thereof. Such polymers are described in detail in Ullmann's
Encyclopedia of Industrial Chemistry 5.sup.th. Ed. 1993, VCH
Verlagsgesellschaft, Vol. 23, page 241 ff and the references cited
therein. In particular, these polymers can be prepared in solution,
for example in tert. butanol or methanol. Before isolation of the
polymer these processes yield a solution of polymer and unreacted
monomer in the respective solvent. Such solutions may be also be
used in order to prepare the inventive concentrates.
[0032] The polymers (2) used may contain 40 to 90% by weight,
preferably 60 to 80% by weight vinyl acetate and 10 to 60% by
weight, preferably 20 to 40% by weight ethylene. In said polymers a
percentage of the vinyl acetate and/or ethylene may be replaced by
one or more further monomers, e.g. 10 to 50% by weight of one or
more further monomers, wherein the sum of all monomers in the
polymer(s) (2) still has to give 100% by weight
[0033] Further monomer(s) encompass, but are not limited to, alkyl
esters of unsaturated mono- or di-carboxylic acids. Fumaric or
maleic acid mono- or di-ethyl esters are particularly suitable.
[0034] It is an important feature of the invention that the
concentrate contains less than 10% by weight of one or more
polymers (2), based on the total weight of the polymer additive(s)
(1) and the polymer(s) (2). Preferably the concentrate contains 2
to 10% by weight, particularly preferred 3 to 8% by weight and most
preferably 3 to 6% by weight of one or more polymers (2), based on
the total weight of the polymer additive(s) (1) and the polymer(s)
(2).
[0035] The second object of this invention is a method of preparing
such concentrates containing [0036] (1) one or more polymer
additives and [0037] (2) one or more polymers which comprise
repeating units of ethylene, vinyl acetate and optionally one or
more other monomers, comprising [0038] mixing the polymer
additive(s) (1) with a solution of the polymer(s) (2) in a solvent,
wherein the polymer additive(s) (1) have a mean primary particle
size ("d.sub.50") of less than 10 .mu.m prior to the mixing with
the solution of the polymer(s) (2), and [0039] removing the
solvent, wherein the concentrate has a bulk density which is at
least 50% greater than that of the polymer additive(s) (1) prior to
the mixing with the solution of the polymer(s) (2).
[0040] The polymer(s) (2) are used in a solution to prepare the
inventive concentrates. Solvents which are typically used to
prepare the solution of the polymer(s) (2) are organic solvents
like e.g. methanol, tert. butanol, toluene or methyl acetate.
Typically the solution of the polymer(s) (2) contains 70-99%.b.w of
the solvent and 1-30% by weight of the polymer(s), based on the
total amount of solvent and polymer(s), preferably 80-98% by weight
of the solvent and 2-20% by weight of the polymer(s). Additionally
the solution of the polymer(s) may contain from 2-20% by weight,
preferably 4-10% by weight of vinylacetate, based on the total
amount of solvent, polymer(s) and vinylacetate.
[0041] In the next step the solvent is removed. Typically other
volatiles may be also removed together with the solvent.
[0042] To prepare the concentrate of the polymer additive(s) (1),
preferably the fillers, flame-retardants, flame-retardant
synergists, pigments, other finely powdered polymer additives or
any mixtures thereof, and the solution of the polymer(s) (2)
different processes can be used, especially in order to get a
better redispersibility, higher bulk density, less trapped air,
less dusting properties and better flowability compared with the
typically fine powder of fillers known as state of the art. The
processes which are suitable differ in the amount of solvent in the
solution of the polymer(s) (2) that is used and which therefore has
to be removed in the second step from the solid granules, pellets
or tablets. For each process and the properties of the resulting
granules, pellets or tablets the amount of polymer remaining as
binder in the granules, pellets or tablets as well as the amount of
solvent initially present as moisture for plastizising, dispersing
and granulating, each related to the total amount of solids
employed, determine the economics of the process as well as the
particular method used and the properties of the final granules,
pellets or tablets.
[0043] The first process alternative of mixing the solid powder
particles of the polymer additive(s) (1) with the solution of the
polymer(s) (2) is to disperse the solid powder particles of the
polymer additive(s) (1) in the polymer solution by preparing a
suspension in a stirred vessel or even with additional
deagglomeration forces for the solid powder particles. Processes to
be used for dispersing the solid powder particles of the polymer
additive (1) can be different types of stirrers (e.g. propeller,
horseshoe, helix, tooth wheel), high shear dispersing units (e.g.
rotor-stator-mixers batch or continuous, colloid mills, corrundum
disk mills), continuous powder dispersing units (e.g. jet pumps,
powder draw in with rotor stator systems) or high energy systems
such as a jet disperser, ultrasonic systems, roller mills or
stirred media mills.
[0044] With these dispersing units the total solids content (this
shall mean by definition the sum of the polymer additive(s) (1) and
the polymer(s) (2)), is 5-80% by weight, preferably 10-70% by
weight and particularly preferred 20-60%, based on the total weight
of the solution of the polymer(s) (2) and the polymer additives
(1).
[0045] Subsequent to the dispersing step the granules, pellets or
tablets have to be formed either in an integrated shaping and
drying step such as fluidized bed granulation, spray granulation,
vacuum drying in a mixer granulator or in a drying step such as
spray drying or vacuum drying with a subsequent granulating step
such as roller compaction or tableting.
[0046] Using the second process alternative less amount of solvent
is needed: High shear machines for moist powders, pastes or
suspensions are used in this case. Typical machines are extruders
such as single screw extruders, parallel rotating or counter
rotating, twin screw extruders or planetary extruders and kneaders
such as co-kneaders or sigma-kneaders as well as other batch or
continuous kneaders. With these machines, under high shear
conditions, the solid powder particles of the polymer additives (2)
can be dispersed in the solution of the polymer(s) (1) and
subsequently the mixture can be shaped by an integrated granulation
or a further shaping step such as low pressure extrusion with
frontal, radial or dome extrusion, pelletizing or granulating from
the moist state of product. Such dispersing units work with total
solid contents of 5-99% by weight, preferably 50-95% by weight and
particularly preferred 55-90% by weight based on the total weight
of the solution of the polymer(s) (2) and the polymer additives
(1).
[0047] The third and very effective process alternative to obtain
granules, which generally employs even less solvent, is growth
agglomeration by roll agglomeration or high shear agglomeration or
combinations thereof. These processes work by moving the powdered
particles of the polymer additive(s) (1) e.g. in a vessel, on a
pelletizer plate or in a mixing chamber. The solution of the
polymer(s) (2) is then added either at once as a batch, in a flow,
as a semibatch or continuously, by spraying either semibatchwise or
continuously. Under more or less intensive mixing the powder
particles agglomerate by means of fluid bridges and a growth
agglomeration results.
[0048] Depending on the particular process which is used for this
third alternative a more or less narrow particle size distribution
results which can be classified if desired in an integrated or
subsequent classifying process. The granulation process itself
needs relatively small amounts of the solution of the polymer(s)
(2). This third process alternative can be carried out with a total
solid content of 20-99% by weight, preferably 50-95% by weight and
particularly preferred 60-90% by weight, based on the total weight
of the solution of the polymer(s) (2) and the polymer additives
(1).
[0049] A very small amount of solvent is possible, when using the
affinity of the fine powder of the polymer additives (1) to
agglomerate because of its surface forces. The affinity can be
intensified and the stability of the resulting granules improved by
moistening the solid powder of the polymer additives (1) with a
very small amount of polymer solution at the beginning. The
subsequent granulating process either can be a growth agglomeration
or a dry pressure agglomeration e.g. roller compacting or
tableting.
[0050] For most applications of the inventive concentrates in the
form of granules the granules are required to be essentially
solvent free. How the solvent is removed depends on the form of the
moist product after dispersion and/or granulation. Due to the
necessity to ensure that no explosion can occur vacuum drying is
often used but also convective heat and mass transfer by static or
vibrating fluidized bed drying (fluidized bed), spray drying,
continuous-flow drying, flash drying or radiation dryers are
possible. Depending on the acceptable residual solvent a post
drying process (e.g. after a gentle convective drying process to
obtain granules of a certain strength) may be necessary. The
concentrate may be also subjected to a classifying, if this is
deemed helpful.
[0051] Also a spheronising step before or after drying may be
helpful, e.g. in order to improve the flow behaviour of the
granules, pellets or tablets or to improve the particle size
distribution as well as to abrade the rough edges remaining after
the granules, pellets or tablets have been formed and dried. Such a
step also reduces the dusting of the resulting product.
[0052] The preparation of granules, pellets or tablets and their
characterisation is described in an article by M. Muller,
Aufbereitungstechnik, 44, (2003), Nr. 2, page 22 ff and in an
article by Nold, Lobe and Muller, Interceram, 53, (2004), Nr. 2,
page 96 ff.
[0053] It is a decisive feature of the inventive concentrate, of
course after the removal of the solvent, that it has a bulk density
which is at least 50% greater than the one which the polymer
additive(s) (1) have prior to the mixing with the solution of the
polymer(s) (2). This means that the present invention allows the
preparation of solid concentrates with a high bulk density.
Preferably the bulk density of the inventive concentrate is at
least 100% greater than the one which the polymer additive(s) (1)
have prior to the mixing with the solution of the polymer(s)
(2).
[0054] The bulk density is measured in accordance with DIN ISO 697
from January 1984.
[0055] The invention is further directed to the use of the
inventive concentrates for preparing polymer compounds and to a
process of preparing such polymer compounds containing the
concentrates.
[0056] Such process of preparing polymer compounds containing the
inventive concentrates comprises mixing the inventive concentrates
with one or more polymers (3).
[0057] Such polymers (3) encompass, but not limited to, nitrile
rubber (also abbreviated as "NBR"), hydrogenated nitrile rubber
(also abbreviated as "HNBR"), polyamides, polycarbonate,
polyvinylchloride ("PVC"), AEM and EVM. All such polymers (3) are
well-known and either commercially available or may be prepared by
a person skilled in the art based on known synthesis or
manufacturing processes.
[0058] As used throughout this specification, the term "nitrile
rubber" or "NBR" is intended to have a broad meaning and is meant
to encompass an elastomer having repeating units derived from at
least one conjugated diene, at least one alpha-beta-unsaturated
nitrile, and optionally further one or more copolymerizable
monomers.
[0059] The conjugated diene may be any known conjugated diene,
preferably a C.sub.4-C.sub.6 conjugated diene. Preferred conjugated
dienes are butadiene, isoprene, piperylene, 2,3-dimethyl butadiene
and mixtures thereof. Even more preferred C.sub.4-C.sub.6
conjugated dienes are butadiene, isoprene and mixtures thereof. The
most preferred C.sub.4-C.sub.6 conjugated diene is butadiene.
[0060] The alpha-beta-unsaturated nitrile may be any known
alpha-beta-unsaturated nitrile, preferably a C.sub.3-C.sub.5
alpha-beta-unsaturated nitrile. Preferred C.sub.3-C.sub.5
alpha-beta-unsaturated nitriles are acrylonitrile,
methacrylonitrile, ethacrylonitrile and mixtures thereof. The most
preferred C.sub.3-C.sub.5 alpha-beta-unsaturated nitrile is
acrylonitrile.
[0061] Preferably, the copolymer contains in the range of from 40
to 85% by weight of repeating units derived from one or more
conjugated dienes, in the range of from 15 to 60 weight percent of
repeating units derived from one or more alpha-beta-unsaturated
nitriles. More preferably, the copolymer contains in the range of
from 55 to 75 weight percent of repeating units derived from one or
more conjugated dienes, in the range of from 25 to 40 weight
percent of repeating units derived from one or more
alpha-beta-unsaturated nitriles.
[0062] Optionally, the copolymer may further contain repeating
units derived from one or more copolymerizable monomers, such as
unsaturated carboxylic acids, alkyl acrylates and/or styrene.
Repeating units derived from one or more copolymerizable monomers
will replace either the nitrile or the diene portion of the nitrile
rubber and it will be apparent to the skilled in the art that the
above mentioned figures will have to be adjusted to result in 100%
by weight
[0063] The "hydrogenated nitrile rubber" or "HNBR" means that the
residual double bonds (RDB) present in the starting nitrile
polymer/NBR are hydrogenated to a certain extent, typically more
than 50% of the residual double bonds are hydrogenated, preferably
more than 90%, more preferably more than 95% and most preferably
more than 99% of the residual double bonds are hydrogenated.
[0064] The term "polyamide" shall encompass homo- or copolymers
which contain monomer repeating unit, which are linked by amide
groups (--C(.dbd.O)--NH--). Examples of such polyamides cover
polycaprolactam (nylon 6), polylaurolactam (nylon 12),
polyhexamethylenadipate (nylon 6.6), polyhexamethylenazelamide
(nylon 6.9), Polyhexamethylensebacamide (nylon 6.10),
polyhexamethylenisophthalamide (nylon 6, IP), polyaminoundecansaure
(nylon 11), Polytetramethylenadipamide (nylon 4.6) as well as
copolymers of caprolactame, hexamethylendiamine and adipic acid
(nylon 6.6) and aramides like e.g.
polyparaphenylenterephthalamide.
[0065] The term "polycarbonate" shall encompass the group of
thermoplastic materials which can be formally considered to be a
polyester from carbonic acid and aliphatic or aromatic dihydroxyl
moieties. Economically the most important example are the
polycarbonate produced from bisphenol A
(2,2-(4,4-dihydroxy-diphenyl)-propane) and phosgene, but for
particular properties other dihydroxy-diaryl-alkanes as well as
other dihydroxy aromatic or aliphatic moieties can be included
during the manufacturing process.
[0066] "Polyvinylchloride" or "PVC" shall be assumed to mean those
polymers prepared by either suspension, emulsion or bulk
polymerisation processes and based formally on the monomeric unit
CH.sub.2--CHCl. Those polymers commercially available can also
contain comonomers such as vinyl acetate, vinylidene chloride or
acrylonitrile. Additionally, PVC is also available which has been
chlorinated after polymerisation and these polymers too are
included within the scope of the present invention.
[0067] "Polyacrylates" or "AEM" is used herein to mean the polymers
produced by an emulsion (co)polymerisation of, but not limited to,
one or more of the following monomers: ethyl acrylate, butyl
acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, caprolacton
acrylate, 2-chloroethyl vinyl ether, vinyl chloroacetate, p-vinyl
benzyl chloride, allyl glycidyl ether, glycidyl methacrylate,
acrylic acid and methacrylic acid.
[0068] Eventually the invention concerns the polymer compounds
containing the inventive concentrates and one or more polymers (3),
a process for preparing such polymer compounds as well as the
formed parts manufactured from the polymer compounds.
[0069] The preparation of the polymer compounds is typically
achieved by compounding the concentrates of the present invention
with one or more polymers (3). This compounding can be done by
using for example an internal mixer, a mixing extruder, such as a
twin screw extruder or a bus co-kneader.
[0070] The polymer compounds containing the inventive concentrates
can be used for preparing formed parts thereof. Such formed parts
may be profiles such as sealing profiles or such as window
profiles, equipment housings such as for computers and household or
industrial electrical equipment, and for functional articles such
as hoses and belts.
[0071] Such formed parts can be formed by extrusion, injection
moulding or compression moulding techniques and may be vulcanised
(crosslinked) after forming to improve the mechanical properties of
the finished articles.
[0072] The concentrates obtained by the process of this invention
can be described as low dusting during processing and are easy to
meter and handle. They maintain the fine particle size, and
nevertheless show low dusting. When being used for preparing
polymer compounds, they are dispersed in the polymer faster and
more efficient than the untreated polymer additive(s) and yield
polymer compounds having improved performance due to the more
uniform and homogeneous incorporation of the polymer additive(s).
Such increase of the compounding speed enhances the commercial
attractiveness of the processing.
[0073] Formed parts containing the inventive concentrates are more
uniform with respect to density, wall thickness, and more
homogeneous compared to formed parts known so far. Physical
properties such as flammability test performance and/or impact
strength also are enhanced.
[0074] Those skilled in the art would not have expected that
increasing the bulk density of the specific polymer additives (1)
by transferring them into the inventive concentrates would enhance
the processability, achieve better dispersion of the additive
throughout the polymer, or enhance the properties of the processed
polymer compound.
EXAMPLES
[0075] The concentrates of the present invention can be
characterised visually to determine their tendency to form dust. A
quantitative indication of the tendency to form dust can be derived
from a sieve analysis.
[0076] The bulk density can be measured according to DIN ISO 697
from January 1984.
[0077] The quality of the dispersion of the polymer additives (1),
in particular of fillers, in polymers and, in particular, in rubber
can be measured by the shear modulus at varying amplitudes as
described in A. R. Payne, R. E. Whittacker, Rubber Chem. Technol.
44, 440 (1971).
[0078] In the Examples Mg(OH).sub.2 was used as polymer additive
(1), which has the trade name Magnifin.RTM. H10A (Fa. Martinswerk,
Germany) and a mean primary particle size (d.sub.50) of 0.65-0.95
.mu.m measured by laser diffraction using a MALVERN MASTERSIZER
S.
Examples 1a-d
Preparing an Inventive Concentrate in the Form of Fine Granules by
Dispersing as a Polymer Additive (1) a Flame Retardant in an
Organic Polymer-Solution and Vacuum Drying of the Granules
Example 1a
[0079] In a first example 1a 95 g of the flame retardant
Mg(OH).sub.2, (Magnifin.RTM. H10A, Fa. Martinswerk) was dispersed
in 155 g of a solution containing 95 vol.-% of tert. butanol, 5
vol.-% vinyl acetate and 5 g of an ethylene vinyl acetate copolymer
itself containing 70% by weight vinyl acetate and 30% by weight
ethylene (Levapren.RTM.700, Lanxess Deutschland GmbH, Germany). The
flame retardant was dispersed by a batch lab disperser (Ultraturrax
T18, Fa. IKA, Germany) for 5 minutes resulting in an increase of
temperature of 10.degree. C. The resulting suspension had a solid
content of 40% by weight. After dispersion, the suspension was
dried at 20.degree. C. in a lab extractor hood to yield a thick,
solvent containing, paste which was then vacuum dried at 40.degree.
C. for 48 h. The resulting fine granules of Mg(OH).sub.2 contained
5% by weight ethylene vinyl acetate copolymer.
[0080] This procedure was repeated for the following examples all
employing Mg(OH).sub.2 as a filler (Magnifin.RTM. H1M, Fa.
Martinswerk) and the copolymer used in Example 1a.:
Example 1b
[0081] 90 g of filler, 160 g of a solvent mixture (95 vol. % of
tert. butanol and 5 vol. % of vinyl acetate), 10 g of ethylene
vinyl acetate copolymer.
Example 1c
[0082] 98 g of filler, 152 g of a solvent mixture (95 vol. % of
tert. Butanol and 5 vol. % of vinyl acetate), 2 g of ethylene vinyl
acetate copolymer
Example 1d
[0083] 99 g of filler, 151 g of a solvent mixture (95 vol. % of
tert. Butanol and 5 vol. % of vinyl acetate), 1 g of ethylene vinyl
acetate copolymer
Examples 2a-f
[0084] Preparing an inventive concentrate in the form of coarser
granules by agglomerating as a polymer additive a flame retardant
with an organic binder solution containing an ethylene vinyl
acetate copolymer and vacuum drying of granules.
[0085] In a second example coarse granules were produced by growth
agglomeration in an intensive mixer (Eirich-Mixer R02, Fa. Eirich,
Hardheim, Germany).
Example 2a
[0086] 1000 g of flame retardant Mg(OH).sub.2 (Magnifin.RTM. H10A,
Fa. Martinswerk, Germany) was placed in an "Eirich-Mixer". The
mixing was carried out under a blanket of nitrogen (Level 1 of
mixer vessel, 1500 U/min of a pin mixing tool). 350 g of polymer
solution containing 85.5% by weight of tert. butanol, 4.5% by
weight vinyl acetate and 10% by weight of an ethylene vinyl acetate
copolymer, itself containing 70% by weight vinyl acetate and 30% by
weight ethylene (Levapren.RTM.700, Lanxess Deutschland GmbH) was
added in 3:30 min by a flexible tube pump to the dry powder. While
the solution was added the granules grew and after a further 5 min
of post mixing the granules were modified to a more narrow particle
size distribution.
[0087] The granules were then dried at 20.degree. C. in a lab
extractor hood for 24 h and finally vacuum dried for 48 h at
40.degree. C.
[0088] The resulting coarse granules contained 3.6% by weight
ethylene vinyl acetate copolymer.
[0089] This procedure was repeated for the following examples all
employing as a filler Mg(OH).sub.2 (Magnifin.RTM. H1M, Fa.
Martinswerk) and the copolymer used in Example 2a:
Example 2b
[0090] 1000 g of filler, 350 g polymer solution with 89.6% by
weight tert. butanol, 4.7% by weight vinyl acetate and 5.7% by
weight ethylene vinyl acetate copolymer; mixing conditions: mixer
vessel level 1, mixing tool 750 U/min
Example 2c
[0091] 1000 g of filler, 350 g polymer solution with 81.4% by
weight tert. Butanol, 4.3% by weight vinyl acetate and 14.3% by
weight ethylene vinyl acetate copolymer; mixing conditions: mixer
vessel level 1, mixing tool 750 U/min
Example 2d
[0092] 1000 g of filler, 350 g polymer solution with 85.5% by
weight tert. Butanol, 4.5% by weight vinyl acetate and 10% by
weight ethylene vinyl acetate copolymer; mixing conditions: mixer
vessel level 1, mixing tool 750 U/min
Example 2e
[0093] 1000 g of filler, 350 g polymer solution with 85.5% by
weight tert. Butanol, 4.5% b.w vinyl acetate and 10% by weight
ethylene vinyl acetate copolymer; mixing conditions: mixer vessel
level 1, mixing tool 1500 U/min
Example 2f
[0094] 1000 g of filler, 350 g polymer solution with 85.5% by
weight tert. Butanol, 4.5% by weight vinyl acetate and 10% by
weight ethylene vinyl acetate copolymer; mixing conditions: mixer
vessel level 1, mixing tool 3000 U/min
[0095] The products from Examples 2b-2e were analysed by sieve
analysis (vibrating lab sieve, 100 g, 30% intensity, 10 min) to
determine their particle size distribution, but also to determine
their fines content which is an objective measure of their dusting
characteristic.
[0096] All products had <1 wt.-% fines after drying; they did
not dust when shaken.
[0097] The particle size distributions are shown in the following
Table 1 and in FIG. 1.
TABLE-US-00001 TABLE 1 Example 2b 2c 2d 2e 2f Sieved Fraction/%
>4 mm 22.2 5.. 7.9 16.2 0 2-4 mm 60.8 40.6 49.3 40.4 21.2 1-2 mm
16.1 43.5 36.3 34.1 62.5 0.5-1 mm 0.7 10.2 6.4 8.7 15.3 <0.5 mm
0.1 0.4 0.1 0.6 1.1
TABLE-US-00002 TABLE 2 Measurement of the bulk density of the
granules of Examples 1 and 2 in accordance with DIN ISO 697 from
January 1984. EVA bulk density Trial Parameters Sieve fraction* [%
b.w.] [g/l] Comparative No mixing, analysed as As received 0 300
Example received (Magnifin .RTM. H10A) Example 2b Eirich-Mixer, 750
rpm no Classification after 2 825 Granulation Example 2c
Eirich-Mixer, 750 rpm no Classification after 4.8 865 Granulation
Example 2d Eirich-Mixer, 750 rpm no Classification after 3.4 855
Granulation Example 2e Eirich-Mixer, 1500 rpm no Classification
after 3.4 845 Granulation Example 2f Eirich-Mixer, 3000 rpm no
Classification after 3.4 800 Granulation Example 2b Eirich-Mixer,
750 rpm Classifying fraction 2-4 mm 2 685 Example 2c Eirich-Mixer,
750 rpm Classifying fraction 2-4 mm 4.8 740 Example 2d
Eirich-Mixer, 750 rpm Classifying fraction 2-4 mm 3.4 725 Example
2e Eirich-Mixer, 1500 rpm Classifying fraction 2-4 mm 3.4 745
Example 2f Eirich-Mixer, 3000 rpm Classifying fraction 2-4 mm 3.4
670 Example 1a Ultra-Turrax T18, no Classification after 5 485
20.000 rpm Granulation Example 1c Ultra-Turrax T18, no
Classification after 2 480 20.000 rpm Granulation *Column "Sieve
Fraction" The entry "no Classification after Granulation" under
"Sieve Fraction" means that the product as obtained after
granulation was directly subjected to the measurement of the bulk
density. The entry "Classifying fraction 2-4 mm" under "Sieve
Fraction" means that the product obtained after granulation was
subjected to a classifying at first and the fraction obtained
therefrom which had a particle size of 2-4 mm was then subjected to
the measurement of the bulk density.
Example 4
Processing the Granules from Examples 1 and 2 in a Polymer on a Two
Roll Mill
[0098] The concentrates from Examples 1 and 2, as well as untreated
Mg(OH).sub.2 (comparative example) were mixed with an ethylene
vinyl acetate copolymer to produce a visually homogeneous sheet on
a laboratory two roll mill. The time taken to produce the
apparently homogeneous sheet was recorded.
[0099] The two roll mill (LaboWalz W80T; Vogt Maschinenbau GmbH)
used had the following specifications:
Roll diameter: 80 mm, Roll breadth: 280 mm, Roll speed: front: 16.5
Upm, back: 20 Upm, Friction: 1:1.2, Set temperature: 20.degree.
C.
[0100] For each experiment 50 g ethylene vinyl actetate copolymer
(Levapren.RTM. 700, Lanxess Deutschland GmbH, Germany) was put on
the mill and a continuous sheet formed. Thereafter, either the
untreated filler (Mg(OH).sub.2) or the inventive concentrate was
added as rapidly as possible. For the untreated filler the distance
between the rolls (the nip) had to be reduced to 0.5 mm in order to
maintain the majority of the powder in the bank of rubber in the
nip. For all other experiments the nip was maintained at 0.7
mm.
[0101] The sheets from these experiments were used to measure the
shear modulus at varying amplitudes and at a constant frequency of
10 Hz, a temperature of 60.degree. C. using a Rubber Process
Analyser (RPA 2000) made by Alpha Technology. The limiting shear
modulus at zero amplitude can be seen as a measure of the quality
of the dispersion of fillers in a rubber matrix. The results as
given in Table 2 below clearly show that the limiting shear modulus
at zero amplitude is substantially lower and therefore the
dispersion of the filler in the matrix considered better, if the
additive is not used untreated but in the form of the inventive
concentrates.
TABLE-US-00003 TABLE 3 Time to visual Limiting Shear incorporation
Modulus/kPa Untreated Filler* 490 s 900 Example 1a 240 s 730
Example 1c 260 s 740 Example 2d 360 s 700 Example 2c 315 s 700
Example 2b 375 s 780 Example 2e 405 s 725 Example 2f 470 s 750
Levapren 700** .-. 195 *For comparison: Mg(OH).sub.2 as Magnifin
.RTM. H10A, Fa. Martinswerk **For comparison, Levapren .RTM. 700
(Lanxess Deutschland GmbH, Germany) was solely used.
* * * * *