Note: Descriptions are shown in the official language in which they were submitted.
A PROCESS FOR THE__RODU TION OF AQUEOUS DISPER IONS OF
CHLOROPREN7E POLYMERS
This invention relates to a process for the production
of aqueous dispersions of carboxyl-functional chloroprenP
polymers which are suitable as raw materials for adhesives
having excellent adhesion, more particularly to rubber and
metals.
Contact adhesives are adhes ves which are applied to
both parts to be joined and left to dry. By subsequently
fitting the two parts together under pressure, a bond of
high initial strength is established. By virtue of their
o hi gh initial peel strength,chloroprene homopolymers and co-
polymers are suitable raw materials for contact adhesives.
Although contact adhesives based on chloroprene
polymers still predominantly contain organic solvents,
there is a need for ecological and economic reasons for
suitable aqueous dispersions. These dispersions should be
acidic to mildly nPutral and should preferably have pH
values of 2 to 8 and, more preferably, 6 to 8. They should
be shear-stable so that they do not lead to the precipita-
tion of coagulum under shear stressing, as encountered,
for example, during spraying.
~ queous dispersions o~ carboxyl-functional chloroprene
polymers are known, for example, ~rom DE-PS 24 26 012 (=US
4,123,514) and DE-OS 25 ~0 545. These dispersions are
prepared by polymerization of the monomers (in addition to
chloroprene, at least one ~,B-ethylenically unsaturated
carboxylic acid, such as methacrylic acid) in aqueous phase
in the presence of protective colloids; polyvinyl alcohol
and hydroxyalkyl cellulose are recommended as suitable
protective colloids~ Typical anionic, cationic or nonionic
emulsifiers are not used or only in very small quantities, if at
all. The dispersions obtained in this way are said to be
suitable as raw materials for adhesives.
Le A 27 723 - Foreign Countries
By virtue of their pronounced hydrophilicity, protec-
tive colloids present in the dispersion provide the dried
polymer film with the property of absorbing undesirably
large amounts of water in a humid environment. Since dried
adhesive layers are expected to swell only slightly, if at
all, even under unfavorable conditions, the chloroprene
polymer dispersions according to DE-PS 24 26 012 and DE-OS
25 00 545 are only suitable to a limited extent as raw
materials for adhesives.
In addition, the dispersions according to DE-PS 24 26
012 and DE-OS 25 00 545 also contain polymer particles
larger than l ~m in diameter. These particles tend to
sediment. Accordingly, an a~ditional step is necessary
before processing in order to redisperse the sediment. In
lS addition, applicants' own investigations have revealed
another disadvantage of the dispersions prepared in accord-
ance with DE-PS 24 26 012 and DE-OS 25 00 545. The chloro-
prene polymers have only a very low percentage content of
copol~merized units of ~,B-ethylenically unsaturated
carboxylic acid. The high concentration of carboxyl groups
in the aqueous phase indicates that a large proportion of
the carboxylic acid has not participated in the polymeriza-
tion reaction in the required manner.
Accordingly, the problem addressed by the present
invention was to provide non-s~dimenting, acidic or neutral
aqueous dispersions of copolymers based on chloroprene and
~,B-ethylenically unsaturated carboxylic acid in which the
content of unsaturated carboxylic acid in the aq~leous phase
would be as low as possible (i.e~ the unsaturated car-
boxylic acid would be incorporated to a high degree in the
copolymer). The dispersions would be suitable for use as
raw materials for adhesive~ and would provide the adhesive
layers with a long contact adhesion time, with high initial
and ultimate strength and with low water absorption.
~he low degree of incorporation of the unsaturated
Le A 27 723 2
21[?~
carboxylic acid in the polymers of DE-PS 24 26 012 and DE-
OS 25 00 545 is primarily attributable to the copolymeriza-
tion parameters of the chloroprene/unsaturated carboxylic
acid (specifically: chloroprene/methacrylic acid) system;
cf. for example Brandrup/Immergut, "Polymer Handbook", 2nd
Edition, II-156, J. Wiley, 1975. A higher degree of incor-
poration can generally be obtained by a higher conversion
although, in that case, the necessary reacti.on times and
higher concentrations of initiator also promote higher gel
contents of the polymers.
It has now surprisingly been found th~t the problem
stated above can be solved by polymerization by the so-
called "seed inflow process" in the absence of protective
colloids (but optionally in the presence of typical ionic
and/or nonionic emulsifiers) at temperatures of 5 to 35C
and preferably at temperatures of 10 to 35C, providing
steps are taken to ensure that the inflow of monomer, as
measured on the basis of polymer already present, does not
exceed certain low values.
Accordingly, the present invention relates to a
process for the production of aqueous dispersions of
chloroprene polymer containing
a) 90 to 99.6% by weight copolymerized chloroprene, of
which up to 10% by weight may be replaced by other
copolymerizable monomers and/or up to 2% by weiyht by
sulfur, based in either case on a), and
b) 0.4 to 10% by weight copolymerized ~,B-ethylenically
unsaturated carboxylic acid corresponding to the
following formula
R
I
H2C C CQOH
in which
Le A 27 723 3
2~5~
R represents hydrogen, C14 alkyl or CH2COOH,
by emulsion polymerization at 5 to 35C and preferably at
10 to 30C by the seed in~low method in the absence of
protective colloids, in which 70 to 98% by weight and
preferably 90 to 95% by weight monomer (a+b) ("inflow") is
polymerized in the presence of 2 to 30% by weight and
preferably 5 to 10% by weight polymer formed from the
monomers a and optionally b ("seed"), the inflow being
regulated in such a way that the ratîo by weight of polymer
formed to free monomer in the reaction mixture at any stage
of the subsequent polymerization process ~inflow process)
is ~50:<50, preferably >70:.~30 and, more preferably,
>80:<20,
the percentages of components a) and b) on the one hand and
of seed and inflow on the other hand adding up to 100.
"Other" copolymerizable monomers a) suitable for the
process according to the invention do not include the
carboxylic acids b), but instead mono- and di~ethylenically
unsaturated compounds containing 3 to ~ carbon atoms, such
as for example monoethylenically unsaturated aliphatic
compounds, such as acrylonitxile, methacrylonitrile, ~-
chloroacrylonitrile, vinylidene chloride, Cl_4 alkyl acry-
lates, C14 alkyl methacrylates, vinyl-substituted aromati.c
compounds, such as styrene and vinyl toll~enes, dienes, such
as 1,3-butadiene, 1-chloro-1,3-butadiene, 2,3-dichloro-1,3-
butadiene and 2-chloro-3-methyl-1,3-butadiene.
Carboxylic acids b) suitable for the process according
to the invention include, for example, acrylic acid,
methacrylic acid, 2-ethyl acrylic acid, 2-propyl acrylic
acid, 2-butyl acrylic acid, itacon.ic acid and mixtures
thereof; the most preferred carboxylic acid b) is meth-
acrylic acid.
The emulsion polymerization may be carried out in
alkaline or acidic aqueous medium; cf. "Ullmanns Encyklo
Le A 27 723 4
padie der Technischen Chemie", Vol. 9, pages 366 et ~.,
Verlag Urban und Schwarzenberg, Munchen/Berlin 1957;
"Encyclopedia of Polymer Science and Technology", Vol. 3,
pages 705 to 730, John Wiley, New York 1965; I'Methoden der
Organischen Chemie" (Houben-Weyl) XIV/1, 733 et ~q., Georg
Thieme Verlag, 5tuttgart 1961. The polymerization is
preferably carried out in an acidic pH range of 1.5 to 5
and, more particularly, 2 to 4.
The pH value may be adjusted and maintained by addi-
tion of mineral acids ~r water-soluble, organic, non-
polymerizable acids. The system may be buffered for
protection against unintentional shifts in the pH value.
Activators and activator systems are used to initiate
and maintain the polym~rization reaction. Preferred
activators or activator systems include hydrogen peroxide,
water soluble salts of peroxodisulfuric acid, such as
potassium peroxodisulfate, organic peroxides and, prefer-
ably, redox systems, i.e. combinations of inorganic or
organic peroxo compounds with suitable reducing agents.
2xamples o~ such redox systems include the combinations
potassium peroxodisulfate/sodium dithionite, ammonium
persulfate/sodium hydroxymethyl sul~inate, diisopropyl
hydroperoxide/hydrogen sulfide and peroxide/triethanol-
amine. The activators or activator systems are generally
used in quantities of 0.1 to 3 mmol and pre~erably in
quantities o~ 0.2 to 2.5 mmol per 100 g polymerizable
monomer used.
Suitable emulsifiers are, basically, any anionic,
cationic, amphoteric and nonionic emulsifiers ~except for
protective colloids), i.e. compounds of the type described,
for example, in 'IMethoden der Organischen Chemie" (Houben-
Weyl), 4th Edition, Vol. 141, Georg Thieme Verlag, Stutt
gart 1961, pages 190 et se~.
Preferred anionic emulsifiers are alkyla~yl sulfonates
containing ~ to 18 carbon atoms in the alkyl radical, C81a
Le A 27 723 5
alkyl sul~ates and sulfonates, sulfonated succinic acid
esters, sulfonated, sulfated or phosphated addition prod-
ucts of alkylene oxides (more particularly ethylene and,
optionally, propylene oxides) with C~1z alkylphenol~ and
water-soluble naphthalene ~ulfonic acid/formaldehyde
condensates. Particularly pre~erred anionic emulsifiers
are the salts of the sulfated ethoxylation product of
nonylphenol preferably containing 3 to 8 ethoxy units per
molecule. Preferred cations of the anionic emulsi~iers are
sodium, potassium and ammonium. Other preferred ionic
emulsifiers are the salts of the diterpene carboxylic acids
obtained from tall oil, pine balsam and root rosin and,
more particularly, the dispro~ortionation, partial hydro-
genation and polymerization products thereof; see W.
lS Barendrecht, ~.T. Lees in Ullmanns Encyklopadie der tech-
nischen Chemie, 4th Edition, Vol. 12, Verlag Chemie,
Weinheim/New York 1976, pages 528-538.
Preferred cationic emulsifiers are amine salts,
quaternary ammonium and pyridinium salts, such as salts of
dodecyl amine, salts of esterification products of paraffin
fatty acid and dimethyl aminoethanol, salts of condensates
of oleic acid and N,N-diethyl ethylenediamine, salts of
reaction products of primary amines with bis-(2-chloro-
ethyl)-ether or 2 chloro-2'-hydroxydiethyl ether; cetyl
pyridinium chloride, lauryl pyridinium sul~ate; the ~alts
o~ hydrogenated or dehydrogenated abietylamines.
Pre~err~d nonionic emulsifiers are polyadducts based
on ethylene oxide and/or propylene oxide.
The emulsifiers are generally used in quantities of
0.1 to 4% by weight and preferably in quantities of 0.5 to
2.5% by weight, based on monomers to be polymerized.
The process according to the in~ention may be carried
out in the presence of so-called molecular weight regula-
tors ("regulators" for short); cf. "Methoden der 0rganis-
chen Chemie" (Houhen-Weyl), 4th Edition, Vol. 14/1, Georg
Le A 27 723 6
Thieme Verlag, stuttgart 1961, pages 197 et ~g., more
particul~rly pages 31~ et seq. The regulators may be used
in quantities of o.l to 3% by weight and preferably in
guantities of o.3 to 1.5~ by weight, based on monomers to
be polymerized. Suitable regulators include CalB alkyl
mercaptans, such as octyl mercaptan, linear or branched
dodecyl mercaptan, tridecyl mercaptan or mixtures thereof,
di-C420-alkyl xanthogene disulfides containing linear,
branched or cyclic alkyl radicals, such as ethyl xanthogene
disulfide, isopropyl xanthogene disulfide and bis-(methyl-
enetrimethylolpropane)-xanthogene disulfide, polysulfides
and haloforms, such as iodoform. Both molecular weight and
gel content may be influenced by the regulators. It has
been found that the adhesives made from dispersions pro-
duced in accor~ance with the invention have particularlyfavorable properties when the gel content of the chloro-
prene polymers does not exceed 95% by weight.
The gel content is the percentage component which is
insoluble in tetrahydro~uran at 25C (allow 250 mg sample
to stand in 25 ml THF for 24 hours, centri~uge and dry at
70C to constant weight).
A "seed inflow process" is understood to be a polymer-
ization process in which an emulsion polymer (~Iseed~) is
first prepared from a small part o~ the total monomers to
be polymeriæed and the rest of the monomers to be polymer-
ized are left to polymerize in the presence of the seed
either in the same reaction vessel or in another reaction
vessel. It is essential that the polymerization reaction
used to prepare the seed is completed, i.e. the solids
content must have increased to more than 95%, based on
total monomer used. It is also essential that the monomers
to be polymerized in the subsequent inflow process are
introduced in a form which precludes the premature forma-
tion of an emulsion in the inflowing monomer. In other
words, the monomers on the one hand and the emulsifiers and
Le A 27 723 7
activators on the other hand may be regularly run in
separately. Where this procedure is adopted t it should
thus be assumed that few new polymer particles axe formed,
i.e. the monomers of the inflow polymerize onto the polymer
particles of the seed. In one particular e~bodiment, a
small part of the inflow monomers may first be added to the
seed so that these monomers swell the polymer particles of
the seed and, hence, can bring them into a "more polymeriz-
able" state. The remainder of the inflow monomers may then
be introduced, the inflow rate being determined not only by
the claimed parameters, but also by how quickly the energy
released during the exothermic reaction can be dissipated.
In practice, a seed inflow process such as this may
appear, for example, as follows:
The monomer, emulsifier, regulator and the oxidizing
component of a redox activator system are initially intro-
duced into water. This mixture is then heated to reaction
temperature and the reaction is initiated by addition of a
reducing component of the redox activator system, preferab-
ly in the form o~ an aqueous solution, optionally in
admixture with more emulsifier and/or regulator. The
mixture is left to react until there is no further increase
in the solids content. The resulting polymer is the
"seed".
If desired, a small proportion of monomer and, option-
ally, regulator may then be added and the seed allowed to
swell.
Monomers on the one hand and regulator, emulsifier and
activators on the other hand are then separately added in
such a way that the claimed ratio of polymer formed to fre~
monomer is not exceeded in the reaction mixture. The
components are normally allowed to flow in uni~ormly,
although the inflow of monomer and inflow of activator may
also overlap in such a way that the inflow of monomer is
over before the inflow of activator.
Le A 27 723 8
~S~,5
The average particle size of the "seed" polymer is
preferably 50 to 100 nm while the average particle size of
the polymer in the dispersion prepared in accordance with
the invention is preferably 100 to 300 nm and, more pre~er-
ably, 100 to 200 nm, with the proviso that the average
particle size increases by at least 50% during the in~low
polymerization process. In the context of the invention,
the "average particle size" is the ~ value according to
DIN 53 206, i.e. the diameter which belongs to the arith-
lo metic mean of all particle volumes or masses.
The average particle size may be determined by ultra-
centrifuge measurements (H.G. Muller, Colloid & Polymer
Sci. 267, 1113-1116 (1989~).
Dispersions containing no more than 1~ by weight,
based on solids, polymer particles having an average
particle size of more than 1 ~m can he produced by the
process according to the invention.
The process according to the invention may be con-
tinued to a final monomer conversion of more than 85~ by
weight and preferably more than 95% by weight. However,
the reaction may also be terminated at an earlier stage by
addition of polymerization inhibitors, such as diethyl
hydroxyl amine or phenothiazine/butyl pyrocatPchol mix-
tures. Residual monomers may be removed in the usual way,
for example with steam.
The dispersion accumulating on completion o~ polymer-
ization in ~he acidic pH range may be adjusted to the
desired pH value, preferably in the range ~rom pH 6 to pH
8, by addition of aqueous potassium or sodium hydroxide
solution, by addition of ammonia or by addition of amines,
such as for example diethanolamine or triethanolamine.
The dispersions prepared in accordance with the
invention are suitable for the production of water-based
adhesives which are free from, or low in, organic solvents.
In this context, "low'l means a content o~ less than 30% by
Le A 27 723 9
~5~ 5
weight (organic solvent), based on the final adhesive.
For the production of adhesives from dispersions
prepared in accordance with the invention, it is possible
for example to use fillers, such as silica ~lour, quartz
sand, highly disperse silica, hea~y spar, calcium car-
bonate, chalk, dolomite or talcum, optionally ~ogether with
wetting agents, such as for examplP polyphosphates, such as
sodium hexametaphosphate, naphthalene sulfonic acid,
ammonium or sodium polyacrylic acid salts, the fillers
generally being added in quantities of lo to 60~ and
preferably in quantities of 20 to 50~ by weight, based on
adhesive, and the wetting agents generally being added in
quantities of 0.2 to 0.6% by weight, based on filler.
Particularly important additives are zinc and magnes-
ium oxide which act as acceptors for small quantities of
hydrogen chloride which can be eliminated from the poly-
mers.
Other suitable auxiliaries are organic thickeners,
such as for example cellulose derivatives, alginates,
starch, starch derivatives or polyacrylic acid, which may
be used in quantities of 0.01 to 1% by weight, based on
adhesive, or inorganic thickeners, ~uch as bentonites ~or
example, which may be used in quantitie~ af 0.05 to S% by
weight, based on adhesive.
Fungicides may also be added to preserve the adhe-
sives. Fungicides are generally used in quantities of 0.02
to 1% by weight, based on adhesive. Suitable fungicides
are, for example, phenol and cresol derivatives or organo-
tin compounds.
Tackifying resins, such as for example unmodified or
modified natural resins, such as colophony esters, or
synthetic resins, such as phthalate resins, may also be
added to the adhesive. Organic solvents, such as for
example toluene, xylene, butyl acetate, methylethyl ketone,
ethyl acetate, dioxane or mixtures thereo~, ar plastic-
Le A 27 723 10
2~
izers, such as for ~xample adipate-, phthalate- or phos-
phate-based pla.sticizers, may also be added to the disper-
sions prepared in accor~ance with the invention.
The adhesives thus prepared are suitable for bonding
materials of the same kind or of different kinds to ~ne
another, including for example wood, paper, plastics,
textiles, leather, rubber and inorganic materials, such as
ceramics, earthenware or asbestos cement.
In the following Examples, percentages and parts are
by weight.
Examples
Tests
Determination of gel content
The dispersion is applied to a ylass plate and dried
for three days under nitrogen at room temperature to ~orm
a film. 250 mg sample are dissolved or swollen in 25 ml
THF (containing 1 g polymerization inhibitor per liter THF)
for 24 hours at room temperature in a closed vessel. The
mixture is ultracentrifuged for 1 hour at 20,000 r.p.m. and
the percentage by weight of material removed by centrifug-
ing is determined after drying.
Determination of peel strength
The test is carried out in accordance with DIN 53 273.
A 100 ~m thick wet film of the dispersion is applied
to two test specimens ~Nora rubber, roughened, lOOx30 mm)
and aired ~or 1 hour at room temperature. The test spec-
imens are then fitted together for 10 seconds under a
pressure of 4 bar. The bond is then tensile tested at room
temperature in a commercially available tensile testing
machine. The strength values are determined immediately
after bonding and khen after 1 and 9 days.
Le A 27 723 11
i9~5
Determination o~ tensile shear strength
Beechwood test specimens measuring 40x20x5 mm are
coated twice with the dispersion so that a 100 ~m thick wet
film is formed. After drying for 30 minutes at room
temperature, the test specimens are fitted together so that
they overlap over an area of 20 x 10 mm (1 minute, 0.3
bar). Tensile shear strength is measured immediately af~er
~onding and then a~ter 1 day and 9 days.
Determination of the carbo~ylate group content in the serum
and in the polymer
The determination is effected by conductometric
titration in dependence upon the pH value.
The conductivity of the original latex and the latex
after serum exchange are measured in dependence upon the
adjusted pH value. The carboxyl group contents both in the
original latex (= sum of COOH groups in the serum + poly-
mer) and in the polymer can be determined from the titra-
tion data.
Determination o~ shear stability
Shear stability is determined by stirring the disper~
sion with an IKA U-Turrax s~irrer. The dispersion is
sheared for 5, 15 and 30 minutes at 5,000 r.p.m. and then
examined for fish eye fo~ma~ion or coagulate.
Assignment:
S minutes' shearing without coagulate: inadequate (-~
15 minutes' shearing without coagulate: satisfactory (o)
30 minutes' shearing without coagulate: very good (+)
The modulus of elasticity is determined in accordance
with DIN 53 455 and 53 457.
Le A 27 723 12
%~
Determination of water absorption
1. ample preparation
In accordance with the formula:
5.6 x density polymer
= g dispersion,
solids content
dispersion is poured into a tin dish (60 mm 0 x 8 mm
height) until a 2 mm thick film is formed.
The adhesive film is stored for 14 days in a
standard conditioning atmosphere until it is complete-
ly dry. Two 20 x 20 mm test specimens are then
prepared, weighed on an analytical balance (accuracy
+ 0.001 g) and stored in water for 24 h at 23C. The
test specimens are then wiped with a dry paper tissue.
2. Measurement
The weight of the adhesive films is then deter-
mined. The increase in weight (water absorption) is
expressed in ~.
Determination of contact adhesion time Cminutes]
In a standard conditioning atmosphere (23C/50~
relative air humidity), 5 mm wide and 0.32 mm thick adhe-
sive films are applied in a length of approx. 300 mm to
index card (250 g/m2) using a stencil of 0.32 mm thick
wood-free art cardboard (weight per unit area 246 g/m2) and
a film applicator.
Approx. 30 mm long adhesive films are cut out from
these samples at time intervals of 5 mins. and are applied
crosswise in pairs to the stamp of an apparatus so that a
bonded area of 0.25 cm2 is formed. This bonded area is
subjected to a constant load of 50 g for 10 seconds.
Le A 27 723 13
2~S~
The contact adhesion time is at an end when the
adhesive films no longer adhere ~o one another a~ter
removal from the apparatus.
Products used
The ammonium salt of a sulfated ethoxylated nonyl
phenol containing on average four ethoxy groups per mole-
cule is used as the emulsifier.
The product o~ Comparison Example 1 is ~Neoprene 115,
a product of DuPont, Wilmington/Del.~ USA.
The product of ComparisGn Example 2 is ~ispercoll C
74, a product of Bayer AG, Leverkusen.
ExamPles 1 to 5
(Seed inflow process with "internal seed")
0.25 part ammonium persulfate (APS), 88.5 parts
deionized water, 0.07 part emulsifier, 4.2 parts chloro-
prene, 0.15 part methacrylic acid and 0.1 part tert.
dodecyl mercaptan (t-DDM) are introduced into a stirred
reactor.
The reaction vessel is heated to the polymerization
temperature (see Table 1) and the polymerization reaction
is initiated by starting the inflow of activator consisting
of 6.8 par~s deionized water, 0~05 part sodium hydroxy-
methyl sulfonate and 1 part ~mulsifier. AEter a reactiontime o~ 45 minutes, no further increase in the solids con~
tent is observed. The polymer particles of the resulting
dispersions had an average particle size of 55 to 65 ~m.
4.2 Parts chloroprene and 0.15 part t-DDM were then
added to the "seed". After a swelling time of 15 minutes,
a monomer inflow of 90.8 parts chloroprene, 3.8 parts
methacrylic acid and 1 part t-DDM is uniformly started.
On completion of the monomer inflow (8 hours) and the
activator inflow (12 hours), the dispersion i5 freed from
residual monomer by distillation with steam a~d adjusted
Le A 27 723 14
~:~?5~ 5
with ammonia to pH 6,5--7.5.
In the following, PS stands for "particle size" and PS
for "average particle size".
Table 1
Examples
1 2 3 4
Temp. t~C] 10 15 20 25 30
Gel content t~] 5
Peel strength [N/mm]
- immediately 1.4 o.7 o.6 0.6 0.7
- 1 day 8.3 2.2 2.0 2.0 2.2
- 9 days 9.9 5.1 4.6 4.0 5.1
Contact adhesion 1 >8 >~ >8 >8
time [h.]
PS [nm] 147 lS2 155 151 15B
Examples 6 and 7
Further polymerizations were carried out using the
formulation of Example 3 except that the guantity of
methacrylic acid was varied. The reactions were carried
out by the process described for Examples l to 5.
Table 2
Examples
6 7 3
(Comparison) (Invention)
~ethacrylic acid [Parts] 0 1.9 3.8
Gel content t~] <5 <5
Peel strength tN/mm]
- immediately 0.4 0.~ 0.6
- 9 days 1 78 4 6 2 0
Contact adhesion
time [h.] >8 ~8 ~8
PS tnm] 166 151 155
Le A 27 723 ~5
Examples 8_to 11
Dispersions having different regulator contents were
prepared on the basis of the formulation of Example 3.
Table 3
Examples
8 9 10 11 3
(Comparison) (Invention)
.
t-DDM [parts] 0 0.25 0.50 0.75 1.00
Gel content >95 95 94 <5 <5
Peel strength
[N/mm] .
- immediately 0.1 1.0 1.0 1.6 0.6
- 1 day 0.1 2.9 3.4 3.0 2.0
- 9 days 0.1 4.1 4.0 5.6 4.6
Contact
adhesion
time th.] - >8 >8 >8 >8
PS [nm] 155 147 138 150 155
Le A 27 723 16
Example 12
(Seed inflow process with "external seed")
Seed latex:
0.34 Part ammonium persulfate, 112.75 parts deionized
water, 0.34 part 10% aqueous sulfuric acid, 0.69 part
sodium dodecyl benzenesulfonate, 0.21 part dipotassium
hydrogen phosphate, 3.31 parts chloroprene, 0.14 part
methacrylic acid and 0.69 part t-DDM are introduced into a
stirred reactor. The reactor is temperature-controlled to
200C and the polymerization reaction is activated by
starting an inflow consisting of 13.75 parts deionzed water
and 0.12 part sodium hydroxymethyl sulfinate (inflow time
11 hours). 30 minutes after the start of the inflow of
activator, a monomer inflow of 63 parts chloroprene and
2O35 parts methacrylic acid is started (inflow time 10
hours). PS of the seed latex: 63 nm.
Grafting stage:
0.54 Parts ammonium persulfate, 65 parts deionized
water, 0.17 part emulsifier, 0.25 part dipotassium hydrogen
phosphate, 0.25 part 10% aqueous sulfuric acid, 15 parts of
the seed latex, 2.9 parts chloroprene, 0.1 part methacrylic
acid and 1 part t-DDM are introduced into a stirred reac-
tor. The reactor is temperature-controlled to 20C and the
polymerization is initiated by starting an inflow (20 parts
deionized water, 0.18 part sodium hydroxymethyl sulfonate,
1 part emulsifier, inflow time 17 hours). After 30 min-
utes, a monomer inflow of 93.5 parts chloroprene and 3.5
parts methacrylic acid is started (inflow time 15 hours).
Table 4
Gel content ~%] 20
Peel strength [N/mm]
- immediately 1.7
- 1 day 3-4
Le A 27 723 17
- g days 5.8
contact adhesion time [h.] >8
PS [nm] 200
Comparison Examples 1 and 2
Commercially available polychloroprene latices corre
sponding to the prior art were used for comparison with the
dispersions according to the invention.
Example 12 comparison Examples
1 2
Solids [%] 49.7 45.3 55.1
pH value 6.9 6.9 12.4
Gel content [%] 21 55 13
Av. PS ~nm] 208 290 110
E modulus [MPa] 1.15 0.61
Peel strength ~N/mm]
- immediately 1.7 0.4 3.2
~ 1 day 3.4 0.9 8.8
- 9 days 5.8 1.7 9.6
Contact adhesion
time [h.] >8 >8 <0.5
Water absorption [%] 4 33
Shear stability + - -
COOH groups/serum [~] 14 68 80
COOH groups/
polymers [%] 86 32 20
Le A 27 723 18
