U.S. patent application number 12/862058 was filed with the patent office on 2011-07-28 for nano-sized diene-based polymer latex particles.
This patent application is currently assigned to UNIVERSITY OF WATERLOO. Invention is credited to Guangwei He, Qinmin Pan, Garry L. Rempel.
Application Number | 20110184120 12/862058 |
Document ID | / |
Family ID | 41381856 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110184120 |
Kind Code |
A1 |
Pan; Qinmin ; et
al. |
July 28, 2011 |
Nano-sized diene-based polymer latex particles
Abstract
The present invention refers to diene-based unsaturated polymer
latex particles having a particle size measured as d.sub.90-value
of less than 60 nm and a method for their production.
Inventors: |
Pan; Qinmin; (Waterloo,
CA) ; Rempel; Garry L.; (Waterloo, CA) ; He;
Guangwei; (Coral Springs, FL) |
Assignee: |
UNIVERSITY OF WATERLOO
Waterloo
CA
|
Family ID: |
41381856 |
Appl. No.: |
12/862058 |
Filed: |
August 24, 2010 |
Current U.S.
Class: |
524/565 |
Current CPC
Class: |
C08F 236/12 20130101;
Y10T 428/2982 20150115; C08F 236/12 20130101; C08C 19/02 20130101;
C08L 9/04 20130101; C08F 2/24 20130101 |
Class at
Publication: |
524/565 |
International
Class: |
C08L 9/04 20060101
C08L009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2009 |
EP |
09 168 713.7 |
Claims
1. Diene-based unsaturated polymer latex particles having a
particle size measured as d.sub.90-value of less than 60 nm.
2. Latex particles according to claim 1, wherein the diene-based
latex particles are acrylonitrile/butadiene polymers.
3. Method for producing diene-based unsaturated polymers in latex
form comprising a) polymerization of at least one diene D and
optionally at least one copolymerisable monomer A b) in an aqueous
medium, preferably water, c) in the presence of a surfactant,
preferably an alkyl sulphate, wherein d) diene D and optionally at
least one copolymerisable monomer A are continuously charged into a
reactor containing the aqueous medium, a polymerisation initiator
and the surfactant, preferably in slow and steady feeding rate.
4. Method according to claim 3, wherein the diene D is
1,3-butadiene and wherein at least one copolymerizable monomer A is
reacted.
5. Method according to claim 3, wherein the copolymerizable monomer
A is acrylonitrile.
6. Method according to claim 3, wherein the polymerization is
performed in the presence of a surfactant in an amount of 0.1% to
1% in weight based on the total monomer amount used.
7. Method according to claim 3, wherein the obtained diene-based
latex particles have a diameter measured as d.sub.90-value of less
than 60 nm.
8. Method according to claim 3, wherein the polymerization
initiator is a redox initiator, preferably a persulfate.
9. Method according to claim 3, wherein the surfactant is an
alkylsulfate.
10. Method for hydrogenation of unsaturated diene-based polymers,
wherein diene-based latex particles according to claim 1 are
hydrogenated.
11. Rubber or rubber intermediate comprising a polymer according to
claim 1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to nano-sized diene-based
polymer latex particles, a method for producing such particles and
methods of using them as rubber and for conversion to hydrogenated
polymers.
BACKGROUND OF THE INVENTION
[0002] Diene-based unsaturated polymers, for example nitrile
butadiene rubbers, also known as NBR produced through
polymerization of acrylonitrile and butadiene are well-known in the
art. Processes for copolymerization of acrylonitrile and butadiene
are described for example in U.S. Pat. No. 3,690,349 and U.S. Pat.
No. 5,770,660. Depending on production conditions such polymers can
be obtained as latex in aqueous medium. Unsaturated diene-based
polymers such as NBR are used for a variety of purposes in
industry, moreover processes for hydrogenating such unsaturated
polymers are well-known in the art.
[0003] It has been known that carbon-carbon double bonds in
diene-based polymers may be successfully hydrogenated by treating
the polymer in an organic solution with hydrogen in the presence of
a catalyst to produce their saturated polymers which have
significantly improved end-use properties. Such processes can be
selective in the double bonds which are hydrogenated so that, for
example, the double bonds in aromatic or naphthenic groups are not
hydrogenated and double or triple bonds between carbon and other
atoms such as nitrogen or oxygen are not affected. This field of
art contains many examples of catalysts suitable for such
hydrogenations, including catalysts based on cobalt, nickel,
rhodium, ruthenium, osmium, and iridium. The suitability of the
catalyst depends on the extent of hydrogenation required, the rate
of the hydrogenation reaction and the presence or absence of other
groups, such as carboxyl and nitrile groups, in the polymers.
[0004] Hydrogenation of diene-based polymers has been very
successful, if organometallic catalysts or some special metal salt
catalysts and high-pressure gaseous hydrogen are used. Such success
has been realized in solution hydrogenation, bulk hydrogenation and
direct latex hydrogenation. For the solution hydrogenation of a
diene-based polymer, the polymer is first dissolved in an organic
solvent and then hydrogenation is carried out; after the
hydrogenation, post-treatment is applied to recycle the organic
solvent and to recover the metal catalyst. In this field, there
have been already many patents and patent applications filed in
this area, such as U.S. Pat. No. 6,410,657, U.S. Pat. No.
6,020,439, U.S. Pat. No. 5,705,571, U.S. Pat. No. 5,057,581, and
U.S. Pat. No. 3,454,644.
[0005] In direct latex hydrogenation, a catalyst is directly added
into the latex of a diene-based polymer for the hydrogenation
operation. Many diene based polymers, copolymers or terpolymers are
made by emulsion polymerization processes and they are in a latex
form when they are discharged from polymerization reactors.
Therefore it is very desirable to directly hydrogenate a
diene-based polymer in latex form which is receiving increasing
attention in the recent decade. Many efforts have been made to
realize such a process. U.S. Pat. No. 7,385,010 has disclosed a
process of direct hydrogenating diene-based polymer latex by using
organometallic catalysts and high-pressure gaseous hydrogen.
[0006] In bulk hydrogenation, a catalyst is directly mixed with a
diene-based polymer or a catalyst is entrapped into the polymer,
and then hydrogenation is applied. U.S. Pat. No. 7,345,115 teaches
a process of using an organometallic catalyst and high-pressure
gaseous hydrogen to hydrogenate bulk diene-based polymers at a
temperature higher than 100 deg C., in which the polymer is
directly mixed with the catalyst as particles.
[0007] A significant characteristic of the above processes is that
they all involve catalysts in which a noble metal is involved, that
they all require high-pressure hydrogen and that they may need a
relatively long reaction time.
[0008] To avoid using these noble metals and avoid being operated
under high-pressure, significant attention has been paid to the
hydrogenation of C.dbd.C bonds using hydrazine or a derivative of
hydrazine as a reducing agent together with an oxidant like oxygen,
air or hydrogen peroxide. The hydrogen source to saturate the
C.dbd.C bonds is then generated in-situ as a result of the redox
reactions in which diimide is also formed as intermediate. In U.S.
Pat. No. 4,452,950 the latex hydrogenation is performed using the
hydrazine hydrate/hydrogen peroxide (or oxygen) redox system to
produce diimide in situ. CuSO.sub.4 or FeSO.sub.4 is used as a
catalyst. U.S. Pat. No. 5,039,737 and U.S. Pat. No. 5,442,009
provide a more refined latex hydrogenation process which treats the
hydrogenated latex with ozone to break the cross-linked polymer
chains which form during or after the latex hydrogenation using the
diimide approach. U.S. Pat. No. 6,552,132 B2 discloses that a
compound can be added before, during or after the latex
hydrogenation to break crosslinks formed during the hydrogenation
using the diimide hydrogenation route. The compound can be chosen
from primary or secondary amines, hydroxylamine, imines, azines,
hydrazones and oximes. U.S. Pat. No. 6,635,718 B2 describes the
process for hydrogenating C.dbd.C bonds of an unsaturated polymer
in the form of an aqueous dispersion by using hydrazine and an
oxidizing compound in the presence of a metal compound containing a
metal atom in an oxidation state of at least 4 (such as Ti(IV),
V(V), Mo(VI) and W(VI)) as the catalyst. In Applied Catalysis A:
General 276 (2004) 123-128 and Journal of Applied Polymer Science
Vol. 96, (2005) 1122-1125 detailed investigations relating to the
hydrogenation of nitrile butadiene rubber latex via utilization of
the diimide hydrogenation route are presented which cover examining
hydrogenation efficiency and degree of hydrogenation.
[0009] It has been found that there are side reactions at the
interphase of the latex particles and within the polymer phase,
which generate radicals to initiate the crosslinking of polymers in
the latex form. Using radical scavengers did not show any evidence
in helping to suppress the degree of gel formation. Although there
are methods developed to reduce the crosslinking, the
aforementioned diimide route still encounters gel formation
problems, especially when high hydrogenation conversion is
achieved. Therefore, the resulting hydrogenated rubber mass is
difficult to process or is unsuitable for further use because of
its macroscopic three dimensional cross-linked structure.
SUMMARY OF THE INVENTION
[0010] It was an object of the present invention to provide new
diene-based unsaturated polymers which can easily be hydrogenated
with reduced gel formation. A further object of the present
invention was to provide processes for producing same unsaturated
polymers.
[0011] The present invention provides new nanosized diene-based
unsaturated polymer particles in latex form wherein the particles
have a particle size measured as d.sub.90-value of less than 60 nm,
preferably less than 40 nm, more preferably less than 30 nm and
most preferably 20 nm. In one embodiment the diene-based
unsaturated polymer is an acrylonitrile/butadiene polymer.
[0012] Furthermore, the present invention provides a method for
producing diene-based unsaturated polymers in latex form comprising
[0013] a) polymerisation of at least one diene D and optionally at
least one copolymerizable monomer A [0014] b) in an aqueous medium,
preferably water, [0015] c) in the presence of a surfactant,
preferably alkylsulfate, wherein [0016] d) diene D and optionally
at least one copolymerizable monomer A are continuously, preferably
in slow and steady feeding rate, charged into a reactor containing
the aqueous medium, a polymerisation initiator and the
surfactant.
[0017] In one preferred embodiment the diene D and optionally
monomer A are added continuously and slowly. The length of the
addition period depends on reaction conditions, which in principle
does not allow the monomers D and A to be accumulated into droplets
in the waster phase and usually is at least 10 minutes. In a
further preferred embodiment an amount of less than 1% (in weight,
based on the amount of water), preferably less than 0.1% (in
weight, based on the amount of water) of unreacted diene D and
optionally monomer A in the water phase in the reactor is
maintained.
[0018] In a further preferred embodiment a small amount of a redox
polymerization initiator is used, which is in the range of 0.0.5%
to 5%, preferably 0.1%-1% in weight based on the total amount of
the monomers.
[0019] For the purposes of the present invention the term "diene D
and optionally at least one copolymerizable monomer A are
continuously charged into a reactor" means that not the complete
nor almost the complete amount of reactants are put together into
the reactor at the very beginning of the reaction. The term
includes feeding the reactants with essentially the same feeding
rate and concentration including increasing and decreasing such
rates. Furthermore, the term includes addition of the reactants in
small portions during the reaction.
[0020] The process according to the present invention is useful for
the production of nanosize particles according to the present
invention having a d.sub.90-diameter of less than 60 nm.
[0021] For the purposes of the present invention the
d.sub.90-diameter means that 90% of the particles have a diameter
less than the value indicated.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The diene-based latex particles are based on at least one
diene monomer, preferably at least one conjugated monomer D. The
diene D can be of any nature. In one embodiment (C.sub.4-C.sub.6)
conjugated dienes are used. Preference is given to 1,3-butadiene,
isoprene, 1-methylbutadiene, 2,3-dimethylbutadiene, piperylene,
chloroprene, or mixtures thereof. Particular preference is given to
1,3-butadiene and isoprene or mixtures thereof. Special preference
is given to 1,3-butadiene.
[0023] Suitable copolymerizable monomers A include acrylonitrile,
methacrylonitrile, styrene, alphamethyl styrene, propyl acrylate,
butyl acrylate, propyl methacrylate, butyl methacrylate, and
unsaturated carboxylic acids selected from fumaric acid, maleic
acid, acrylic acid and methacrylic acid.
[0024] According to the present invention, the conjugated diene D
forms from about 15 to about 100% by weight of the carbon-carbon
double bond containing polymer in the latex form. If
copolymerizable monomers A are used and selected from styrene and
alphamethyl styrene, the styrene and/or a methyl styrene monomer
preferably forms from about 15 to about 60% by weight of the
polymer. If the other copolymerizable monomers A are used and
selected from acrylonitrile and methacrylonitrile, the
acrylonitrile and/or methacrylonitrile monomer preferably forms
from about 15 to about 50% by weight of the polymer, with the
conjugated diolefin forming from about 50 to about 85% by weight of
the polymer.
[0025] If other copolymerizable monomers A are used and selected
from acrylonitrile and methacrylonitrile and additionally from an
unsaturated carboxylic acid, the acrylonitrile or methacrylonitrile
forms from about 15 to about 50% by weight of the polymer, the
unsaturated carboxylic acid forms from about 1 to about 10% by
weight of the polymer and the conjugated diolefin forms from about
40 to about 85% by weight of the polymer.
[0026] Preferred products include styrene-butadiene polymers of the
random or block types, butadiene-acrylonitrile polymers and
butadiene-acrylonitrile-methacrylic acid polymers. Preferred
butadiene-acrylonitrile polymers have an acrylonitrile content of
from about 25 to about 45% by weight.
[0027] A particularly suitable copolymer to be used in the present
invention is a nitrile rubber (also abbreviated as "NBR") this
being a copolymer of an .alpha.,.beta.-unsaturated nitrile,
particularly preferred acrylonitrile, and a conjugated diene,
particularly preferred 1,3-butadiene and optionally one or more
further copolymerizable monomers, such as
.alpha.,.beta.-unsaturated monocarboxylic or dicarboxylic acids,
their esters or amides.
[0028] As .alpha.,.beta.-unsaturated monocarboxylic or dicarboxylic
acids in such nitrile rubbers preference is given to fumaric acid,
maleic acid, acrylic acid and methacrylic acid.
[0029] As esters of .alpha.,.beta.-unsaturated carboxylic acids in
such nitrile rubbers preference is given to using their alkyl
esters and alkoxyalkyl esters. Particularly preferred alkyl esters
of .alpha.,.beta.-unsaturated carboxylic acids are methyl acrylate,
ethyl acrylate, propyl acrylate, n-butyl acrylate, tert-butyl
acrylate, propyl methacrylate, n-butyl methacrylate, tert-butyl
methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate and
octyl acrylate. Particularly preferred alkoxyalkyl esters of
.alpha.,.beta.-unsaturated carboxylic acids are
methoxyethyl(meth)acrylate, ethoxyethyl(meth)acrylate and
methoxyethyl(meth)acrylate. It is also possible to use mixtures of
alkyl esters, e.g. those mentioned above, with alkoxyalkyl esters,
e.g. in the form of those mentioned above.
[0030] A preferred terpolymer according to the present invention is
a terpolymer of acrylonitrile, 1,3-butadiene and a third monomer
selected from the group consisting of fumaric acid, maleic acid,
acrylic acid, methacrylic acid, n-butyl acrylate, and tert-butyl
acrylate.
[0031] The synthesis of the polymer can be undertaken in latex
form. The polymers to be produced according to the present
invention are in nanoparticles in the latex.
[0032] The synthesis process of the present invention can be
achieved with use of a chemical redox initiator, such as ammonium
persulphate (APS). Further polymerization initiators include
thermal initiators such as potassium persulfate, dialkylperoxides
or azocompounds and redox initiators, for example
alkylhydroperoxides such as diisopropylbenzine, p-menthane and
pinane hydroperoxides, optionally in combination with cholated
salts and suitable reducing agent.
[0033] The initiator can be used in small quantities. An amount of
APS with respect to the total monomers is in the range of 0.0.5% to
5%, preferably 0.1%-1% in weight based on the total amount of the
monomers.
[0034] The synthesis process of the present invention is preferably
carried out with a surfactant, such as sodium dodecyl sulfate
(SDS). The amount of the surfactant can be from about 0.1% to about
15%, preferably 0.1 to 1% in weight based on the total monomer
amount used.
[0035] In a preferred embodiment of the present invention water is
used as the medium. The amount of water is from about 2 times to
about 30 times, preferably from 5 times to 10 times, in weight
based on the amount of the monomers used.
[0036] The synthesis process of the present invention can be
undertaken in a suitable reactor equipped with temperature
regulating and monomer feeding and agitating means.
[0037] Generally, according to the present invention, the reaction
temperature suitable for the present invention is from about
0.degree. C. to about 100.degree. C., preferably from about
15.degree. C. to about 70.degree. C.
[0038] According to a preferred embodiment of the present
invention, during the course of the reaction, the reaction time is
from about one quarter of an hour to about 100 hours, preferably
from about 1 hour to 20 hours, depending on operational
conditions.
[0039] According to a preferred embodiment of the present
invention, during the course of the reaction, the monomer feeding
time is from is from about one quarter of an hour to about 50
hours, preferably from about 1 hour to 10 hours, depending on
operational conditions.
[0040] According to a preferred embodiment of the present
invention, during the course of the reaction, after the monomer
feeding is finished, an aging time is preferred and it is from
about one quarter of an hour to about 50 hours, preferably from
about 1 hour to 10 hours, depending on operational conditions.
[0041] According to a preferred embodiment of the present
invention, when the reaction is complete, to the extent desired,
the reaction vessel can be cooled (if applicable) and the polymer
latex is obtained.
[0042] In a preferred embodiment the resulting latex may be blended
with additives known in the art for example an antioxidant and may
be transferred to coagulation and washing vessels with sufficient
agitation to prevent agglomeration. Subsequently, the product may
be fed into a final dewatering device, pelletized, coated with a
partitioning agent and transferred to suitable dryers.
[0043] The polymerization may be performed in reactors known in the
art. In one embodiment the reactor is at least one vessel provided
with a stirrer, temperature sensing means for measuring the
progress of the polymerization and at least one inlet for the
continuous addition of the monomers. Furthermore, there are means
to provide an adequate and continuous addition rate of the monomers
regulating the flow rate to reactor volume ratio.
[0044] Nanosized diene-based polymers obtained according to the
present invention can generally be used for the same technical
applications as diene-based latex particles with a higher particle
size as rubber or rubber intermediate showing improved properties
with respect to the resistance to degradation by heat, oxygen, and
ozone. Furthermore, the nanosized diene-based latex particles,
especially based on acrylonitrile and butadiene, can easily be
hydrogenated for the production of for example hydrogenated NBR,
known as HNBR.
EXAMPLES
[0045] The materials which were used in the reaction and analysis
are listed in Table 1.
TABLE-US-00001 TABLE 1 Specification of the Materials Material
Supplier Potassium persulfate (KPS, 98% purity) Aldrich Chemical
Company Sodium dodecyl sulfate (SDS, 95% purity) Sigma-Aldrich
Company Butadiene LANXESS Inc. Acrylonitrile Aldrich Chemical
Company n-dodecyl mercaptan (n-DDM) Aldrich Chemical Company
[0046] The following Examples illustrate the scope of the invention
and are not intended to limit the same.
Example 1
[0047] 0.1 part of KPS, 0.5 parts of SDS, 0.05 part of n-DDM and 40
parts of water were put into a 300 mL stainless steel high-pressure
reactor (Parr Instruments) equipped with a impeller stirrer, an
addition tube and a thermal couple. After the temperature was
raised to 85.degree. C., the mixture of 1.5 parts of acrylonitrile
and 3 parts of butadiene was added as small portions over a period
of 150 min. After addition of the monomer mixture, the reaction
mixture was kept at 80-85.degree. C. for an additional 20 min
before cooling to halt the reaction.
[0048] The solid content was determined by a weighing method and
the z-average particle size was measured using a dynamic light
scattering method with a 90Plus particle size analyzer (Brookhaven
Instrument Corporation). The number average particle sizes were
measured with a Natrac 150 instrument (Microtrac Inc.). The
copolymer composition was measured using an IR technique. A Bio-Rad
FTS 3000.times. spectrometer was used. The infrared samples were
prepared by casting polymer films from MEK solution onto sodium
chloride disks. The particle size of the polymer such obtained is
30 nm.
Example 2
[0049] The same conditions and procedures as described in example 1
were employed, except the reaction temperature was 90.degree. C.
and the reaction time was 35 min and aging time was 25 min. The
particle size of resultant NBR was 19.3 nm
Example 3
[0050] The same conditions and procedures as described in example 1
were employed, except the amount of n-DDM was 0.025 part, the
reaction temperature was 70.degree. C. and the reaction time was
135 min and aging time was 60 min. The particle size of resultant
NBR was 19.1 nm
Example 4
[0051] The same conditions and procedures as described in example 1
were employed, except the reaction temperature was 70.degree. C.
and the monomer feeding time was 180 min and aging time was 25 min.
The particle size of resultant NBR was 23.5 nm
[0052] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *