RUBBER LATEX COMPOUNDS

CAOUCHOUCS DE LATEX

English Abstract

A B S T R A C T
Novel rubber latex compounds comprise an aqueous dispersion of a natural
or synthetic rubber latex and as a foaming agent an alkyl alkoxy sulpho-
succinamate of the formula:-
<IMG>
wherein R represents an alkyl group having from 7 to 18 carbon atoms, one
of X and Y represents a hydrogen atom and the other represents a sulphate
group, n is an integer having a value of from 0 to 5 and R1 represents an
alkylene group comprising 2 or 3 carbon atoms. These foaming agents com-
bine the virtues of acceptable foaming properties with relatively high
solubility in aqueous solution. They can be prepared and transported as
aqueous concentrates containing up to 45% of solids material.
Those co pounds wherein R represents a branched chain alkyl group are
believed to be novel and are claimed as such.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A latex compound which comprises an aqueous disper-
sion of a rubber latex and a sulphosuccinamate of the formula:
<IMG>
wherein R represents an alkyl or alkaryl group having from
7 to 18 carbon atoms, R1 represents an alkylene group having
2 to 3 carbon atoms, n is an integer having a value of from
0 to 5 and one of the groups X and Y represents a hydrogen
atom whilst the other represents a sulphate group.
2. A latex compound according to claim 1, wherein the
latex is a natural rubber latex, a non-carboxylated styrene-
butadiene latex or a mixture of the two.
3. A latex according to claim 1, wherein the latex
used to form the compound comprises from 50 to 70% by weight
of solid material.
4. A latex compound according to claim 1, which com-
prises from 1 to 10 phr of the sulphosuccinamate where phr
is parts by weight of solid matter per 100 parts by weight
of rubber solids in the latex.
5. A latex compound according to claim 4, which com-
prises from 3 to 8 phr of the sulphosuccinamate.
6. A latex compound according to one of claims 2, 3
or 4, wherein the sulphosuccinamate is a compound wherein
n has a value of from 0 to 3.
7. A latex compound according to any one of claims
2, 3 or 4, wherein R1 represents an ethylene group.
8. A latex compound according to claim 1 wherein R
represents an alkyl group comprising from 8 to 18 carbon atoms.
9. A latex compound according to claim 1 which further
comprises a curing agent.
10. A latex compound according to claim 5 wherein the
sulphosuccinamate is a compound wherein n has a value of from
0 to 3.
11. A latex compound according to claim 5 or 6 wherein
R1 represents an ethylene group.

16
12. A foam backed substrate which has been produced
by application of a latex compound according to preceding
claim 1 and drying and curing said compound.
13 A sulphosuccinamate of the formula:
<IMG>
where n is an integer having a value of from 0 to 5, R1 re-
presents an alkylene group comprising two or three carbon atoms,
one of the groups X and Y represents a hydrogen atom and the
other represents a sulphate group S03?, and R represents an
alkyl or alkaryl group having from 7 to 18 carbon atoms wherein
the aliphatic carbon chain is branched at at least one point.
14. A sulphosuccinamate according to claim 13, wherein
R represents a branched chain alkyl group comprising from
8 to 14 carbon atoms.
15. A sulphosuccinamate according to claim 14, wherein
R represents a branched chain alkyl group having from 11 to
14 carbon atoms.
16. A sulphosuccinamate according to claim 13, wherein
n has a value of from 0 to 3.
17. A sulphosuccinamate according to claim 16, wherein
n has a value of 0 or 1.
18. A sulphosuccinamate according to any one of claims
13, 14 or 15, wherein R1 represents an ethylene group.
16

Description

~lZ~46
This invention relates to the manufacture of rubber latex foams.
These latexes are aqueous dispersions of natural or synthetic materials
and the foams are applied for example to the back surface of carpets to
improve the appearance thereof and to give weight and a more luxur;ous
tread to the carpet. The latex dispersion is formulated with a chemical
foaming agent (amongst other ingredients) in order that a foam can be
produced which comprises a large quantity of entrapped air evenly dis-
tributed through the latex.
The choice of foaming agent which is added to the latex is critical
in that it must be able to provide optimum frothing power in order to
entrap a large volume of air and provide a foam which is stable and
does not collapse before it can be cured.
One class of compounds which have been used as the foaming agent for
rubber latexes are sulphosuccinamates having the formula:-
RNHC ~ C - C- C~ O M+
X Y
wherein R represents an aliphatic group comprising from 8 to 22 carbon
atoms one of the groups X and Y represents a hydrogen atom and the
other represents a sulphate group S03 an~ M represents an
alkali metal, alkaline earth metal or ammonium cation.
They are conveniently manufactured by the reaction of an amine
RNH2 with maleic anhydride and subsequently with a sulphite which
reactions proceed substantially according to the equations:
~
~k

~l~2~46
-- 2 --
~) CONHR
~C'~
- C O
RNH2 + 11 / )
C
C~D COOH
CONH R
2 - H
C/ 'S~
C - - )RNHCOf H--COO +
H SO3
COOH
H¦ I
RNHCO--Cl--IC--EOO
H s03
,,

~ 7 ~L~i -
The hydrophobic group R can be any aliphatic group having an
average of from 8 to 22 carbon atoms. The amines RNH2 which have been
employed as the feedstock are derived from synthetic or natural sources.
The vast majority of the sulphosuccinamate surfactants previously
available have comprised groups R which contain from 10 to 18 carbon
atoms suchas lauryl, my~istyl, cetyl, stearyl, oleyl or cocoyl groups,
the carbon atoms in the R group being arranged in a straight chain.
These compounds give an adequate performance as latex foaming
agents. They are sufficiently good foaming agents to be used in the so-
called no-gel foaming systems, i.e. those in which the stability of the
foamed latex is sifficiently good that it does not collapse before
drying and curing can take place. In contrast the so-called gel
systems are those on which the latex foam is relatively unstable and
requires the addition of a gelling agent to improve that stability.
However these sulphosuccinamates used in the no gel systems suffer
from the disadvantage that they are relatively insoluble in aqueous
media. As is the case with other surface active materials it is
desirable to prepare transport and sell them in the form of a con-
centrated solution which is stable to physical change even upon por-
longed storage. The alkyl sulphosuccinamates which have been derived
from natural amines can only be prepared as solutions comprising from
35 to 40~ by weight of solids material and even at these concentrations
they suffer from a tendency to deposit active material as a sediment
or even to gel upon prolonged storage. Careful selection of the length
and distribution of the alkyl chain in the amine feedstock can
alleviate this problem since in general shorter chains s~alkenyl

il2~74
-- 4 --
amines lead to sulphosuccinamates having marginally improved solubility
properties but this improvement does not completely overcome the
solubility problems particularly sedimentation on prolonged storage.
Sulphosuccinamates which are derived from synthetically produced amine
feedstocks which amine comprise alkyl groups having a branched carbon
chain exhibit improved solubility characteristics. West Genman Patent
Application 2657581 describes sulphosuccinamates wherein 50~ of the alkyl
chains were 2 methyl branched.
We have now discovered a particular class of sulphosuccinamates
which exhibit improved solubility characteristics and give acceptable
performance as latex foaming agents. This class comprises compounds of
the formula
H H
Ra~ I-- ( 1 n ~J~ICÇ~ C C--COO
X Y
wherein n is an integer having a value of from 0 to 5; one of the
groups X and Y represents a hydrogen atom, whilst the other represents
a sulpha~e group~ Rl represents an alkylene ~roup having 2 or 3 carban
atoms and ~ represents an alRyl or alkaryl group having from 7-18 carbon atoms.
These sulphosuccinamates may be used as foaming agents in the
production of latex foams from rubber latices which are preferably
natural latices, non-carboxylated styrene-butadiene latices or mixtures
of the two. Rubber latexes are conventionally sold as aqueous disper-
sions comprising from 50 to 65 or 70% by weight of solid material.
These dispersions are formulated into a latex compound which further
comprises the foaming agent.
:, . ~,;

3L3LZ ~4 ~
Latex compounds comprising from 1 to 10 phr preferably from 3 to
8 phr of a sulphosuccinamate as hereinbefore defined form one aspect of
our invention. (phr is parts by weight of solid matter per 100 parts by
weight of rubber solids in the latex dispersion.)
The latex compound is frothed with air so as to produce a foam
having the desired density. This is conveniently achieved by the
continuous controlled introduction of the latex compound and air into
a continuous mechanical foaming machine. The foam thus produced is
spread onto the substrate dried and cured.
In conventional manufacture procedures for latex backed carpets
the foam is applied to the back of a continuous belt of carpet the
thickness of the foam being regulated by a doctor knife. The carpet is
passed under a bank of infra-red heaters so as to form a skin on the
surface of the foam ~nd through a long oven to simultaneously cure
and dry the foam. Foam backed substrates which have been produced by
treating with a foamed latex compound as hereinbefore defined, drying
and curing the foam form a further aspect of our invention.
The latex compound will normally further comprise other ingredients
such as a curing agent for the latex e.g. sulphur and/or a sulphur
donating compound such as zinc thiodicarbonate or zinc mercaptobenzo-
thiozole , zinc oxide, a filler e.g. calcium carbonate and an anti-
oxidant. Optionally a dispersant e.g. polyphosphate and a thickener
e.g. a polyacrylate or methyl-cellulose may be added to the latex
F~ ~ ! 5 U Ip/~O5ucc- ~ c""~
compound as necessary. The ulphosucci~e foaming agent may be re-
placed in part say up to 40% by weight by an auxiliary foaming agent
especially an alkyl sulphate, an alkyl ether sulphate or an amine
oxide.

1~2474
-- 6 --
The amounts of these ingredients which are employed is dependant
upon the precise nature of the latex and on the desired properties of
the particular foam.
The preferred sulphosuccinamates for present use are those wherein
n has a value of: from O to 3, most preferably a value of O to 1.
Compounds which comprise a mixture of species wherein n take different
values but where the average value of n falls within the range defined
above also form part of our invention.
The group Rl may represent an ethylene -CH2-CH2- propylene
-CH2-CH2-CH2- or isopropylene -CH2-CIH- group. Most preferred sulpho
H3
succinamates for use according to our invention are those wherein Rl
represents an ethylene group i.e. those which can be regarded as alkyl
(polyethoxy) sulphosuccinamates.
The alkyl chain R preferably comprises from 8 to 18 e.g. from
8 to 14 and most preferably from 11 to 14 carbon atoms. The carbon
atoms may be arranged in straight or in branched chains or may comprise
a mixture of species having branched and straight chains.
The sulphosuccinamates may be prepared in the acid form or in the
form of a salt of that acid. For convenience they are normally prepared
in the form of their sodium salts.
Those compounds wherein R represents a branched chain alkyl group
are believed to be novel. Accordingly, from a further aspect our
invention provides compounds of the formula:
RORl [ORl ) n NHCO~- C - C COO
X Y
wherein n is an integer having a value of from O to 5, Rl represents

1~L2~7 ~L~
an alkylene group comprising two or three carbon atoms9 one of the
groups X and Y represents a hydrogen atom and the other represents a
sulphate group S03 and R represents an alkyl or alkaryl group having
from 7 to 18 carbon atoms wherein the alphatic carbon chain is branched
at alt.least one point.
These sulphosuccinamates and thos other sulphosuccinamates may be
derived from primary alkyl alkoxy amines using conventional techniques
of synthetic organic chemistry and in particular the route outlined
above.
The amines which are used as the feedstock in the manufacture of
alkyl alkoxy sulphosuccinamates may in turn be derived from alcohols
having the formula ROH which may be natural or synthetic products. These
may be converted to the desired amines using the techniques described in
U~ Patents 2371892 and 2372624bY reaction with acrylonitrile followed by
15 by hydrogenation; the reaction proceeding according to the equations:-
ROH + CH2 - CHCN ? RO CH2CH2CN
H2
ROCH2 CH2CN ~ 3 RO CH2CH2CH2NH2
Alternatively the alcohol may be condensed with an alkylene oxide follow-
20 ed by ammonolysis of the resulting compound according to the equations
(for ethylene oxide):-
ROH ~ x (CH2CH20)x > R (OCH2CH2)x OH
NH
R (OCH2CH2) OH 3 > R (OCH2CH2)x NH2
~!

3L~L~ 7~L~
These alkyl alkoxy amines may then be reacted w;th maleic anhydrideus;ng conventional techniques e.g. by the addition of a substantially
equimolar ~uantity of the amine to molten maleic anhydride at tempera-
tures in the range 50 to 110C which temperatures are maintained for a
period of ~ to 1~ hours. The maleamide intermediate may then be added
to an aqueous solution of an alkali metal alkaline earth metal or
ammonium sulphite or sulphurous acid and the reaction mixture maintained
at a temperature of from 40 to 100C for a period of 1 to 5 hours. Even
where the reaction per;od is prolonged the produce solut;on of sulpho-
succinamate whether in the form of an acid or its salt will be contamin-
ated by unreacted amine. The product is preferably prepared in the form
of its alkali metal and especially its sodium salt.
These solutions of the sodium salts of the sulphosuccinamates
which are useful in our invention may be formulated as compositions
comprising up to 45% by weight of solid material. They will preferably
be prepared and sold as solutions comprising from 35 to 45% by weight of
solid material. The invention is illustrated by the following examples
of which examples 1 to 4 illustrate the preparation of sulphosuccinamates
useful according to the invention.
Example 1
~ 0~
265 gms (1 gm mole) 4~ a synthetic primary amine believed to have
the formula ROCH2CH2NH2 were added with stirring to 989 (1 9 mole) of
maleic anhydride at a temperature of 80 to 90C. The amine used was
obtained from Messrs Hoechst A.G. under the nomenclature HOE 2504/2
wherein R is believed to be a mixture of alkyl groups containing

~2~746
11 to 15 carbon atoms, the alkyl groups being an approximately 50/50
mixture of straight and branched chains. The maleamide was stirred at
this temperature for a further 30 minutes.
The molten maleamide product was slowly added with stirring to a
solution of 130 9 ~1.03 9 moles) of anhydrous sodium sulphite in 700 g of
water at a temperature of 50 to 75C. The resulting solution was main-
tained at a temperat.ure of 70 - 75C with stirring for a further three
hours. The resultant clear solution containing 40% as solid material of
a disodium alkyl sulphosuccinamate and of viscosity 44.9 centistokes at
20C remained a clear solution even a~ter storage at 0C for a period of
six months. In contrast a 35% solids solution of disod;um alkyl sulpho-
succinamate prepared from a synthetic primary amine, RNH2, where R
represents an aliphatic group having from 13 to 15 carbon atoms,
approximately 50% of the groups containing branching, precipitated a
small quantity of insoluble matter under the same storage conditions.
At concentrations above 45% solids this alkyl alkoxy sulphosuc-
cinamate formed a gel at 20C.
Example 2
1369 (0.59 mole) of a synthetic primary amine having the formula
R0 CH2CH2CH2NH2 were added to with stirring to 53.9~ (0.55g mole) o
maleic anhydride at a temperature of 60 to 70C. The maleamide reaction
product was stirred for a further hour at this temperature.
The alkyl alkoxy amine used in the preparation was obtained from
Humko Products Limited under the nomenclature Kemamine*AP860 wherein we
believe R is a mixture comprising 12 and 14 carbon atoms in the alkyl
chain. The carbon atoms in R are arranged in straight chains.
* Trademark
C~

- lo - ~
The molten maleamide reaction produce was slowly added with sitring
to a solution of 69.39 of sodium sulphite and 3.29 of sodium hydroxide in
6449 of water at a temperature of 65 to 70C. The reactant solution was
maintained at this temperature for approximately 30 minutes.
The resultant clear solution containing 35% disodium alkyl alkoxy
sulphosuccinamate remained a clear solution on storage at 20C but did
~end to shed a very small quantity of insoluble matter on storage at 0C.
The viscosity of this 35% solution at 20C was 16.0 centistokes
at 20C.
lo In contrast a 35% solution of disodium alkyl sulphosuccinamate pre-
pared from a synthetic primary amine, RHN2, wherein R represents an ali-
phatic group having from 15 to 17 carbon atoms, approximately 50% of the
groups containing branched chains precipitated a substantial quantity of
insoluble matter on storage at 0C during the same period of time.
Example 3
1369 (0.5 mole) of a synthetic primary amine having a formula
ROCH2CH2CH2NH2 were added with stirring to 53.99 (0.55 g mDles) of maleic
anhydride at a temperature of 60 to 70C. The maleamide reaction product
was stirred for a further hour at this temperatu~e.
The alkyl alkoxy amine used in this preparation was obtained from
Humko Products Limited under the nomenclature Kemamine*AP8600 (a purer
amine derived by distillation of Kemamine*AP860 ) wherein we believe
R is a mixture comprising 12 and 14 carbon atoms in the alkyl chain. The
carbon atoms in R are arranged in straight chains.
* Trademark
~'

llZ~'74G
The molten maleamide reaction product was slowly added with
stirr;ng to a solut;on of 69.3gof sodium sulph;te and3.2s of sod;um
hydrox;de in 6449 of water at a temperature of 65 to 70C. The reactant
sol~lt;cn was maintained at this temperature for approximately 30 m;nutes.
The resultant clear solution containing 35% of solids matter of a
disodium alkyl alkoxy sulphosuccinamate, as with the product ;n Example 2,
remains a clear solution on storage at 20C but d;d tend to shed a small
quant;ty of ;nsoluble matter on storage at 0C.
The viscos;ty of this 35% solut;on at 20C was 15.9 centisbokes.
Example 4
Using the molar rat;os and reaction conditions described ;n Example
2, a 40% solids solution of sodium alkyl alkoxy sulphosuccinamate was
prepared from an alkyl alkoxy amine ROCH2CH2NH2 suppl;ed by Messrs
Hoechst A.G. under nomenclature HOE F1940D wherein the alkyl groups ;n R
are compr;sed of highly branched alkyl chains contain;ng 7 to 9 carbon
atoms.
The v;scosity of this 40% solution at 20C was 116 centistokes.
This solution remained a clear liquid on prolonged storage at 0. and 20C.
Solutions of the alkyl alkoxy sulphosuccinamate remained clear liquids
at 20C at concentrat;ons of up to 45.9%. Above this concentration
solutions tended to ge1.
Example ~
Using the molar rat;os and reaction conditions described in Example
2, a clear 35% solut;on of a sodium alkyl alkoxy sulphosucc;namate was
prepared from an alkyl alkoxy amine ROCH2CH2CH2NH2 suppl;ed by Messrs

Z4~
- 12 -
Humko Chemicals Limited under the nomenclature Kemamin~ AP990 wherein
we believe the alkyl groups in R are composed of highly branched alkyl
cha;ns containing 9 to 13 carbon atoms.
The viscosity of this clear solution was 25 centistokes at 20C.
This solution remained a clear solution on prolonged storage at 0C
and 2G~C.
The efficiency of various sulphosuccinamates was compared by making
a series of latex compounds according to the following formulation:
Intex*131 100 phr
Cure dispersion 8 phr
Foam;ng Agent 5 phr
Filler (Calmonte*AD)150 phr
Calgo~ PT 1 phr
(l) Intex 131 is a synthetic non-carboxylated styrene-butacliene latexsupplied by International Synthetic Rubber Company Limited.
phr is parts by weight of dry solids per 100 parts by weight of
rubber solids in latex dispersion.
Each latex compound was foamed by beating in air using a household
food mixer for 7 minutes and the density was noted. Two samples of the
wet foam were spread to uniform thickness on metal plates. One sample
(A) was immediately cured in an oven at 130 to 140C for 30 minutes. The
second sample (B) was allowed to stand for 10 minutes and then cured in a
similar manner. The second sample, therefore, ind;cates the bank
stability of the wet foam.
* Trademarks
ai

l~LZ ~6
- ~3 -
The cured foams A and B were examined visually for uniformity of
bubble structure on the surface, uniformity of bubble structure in the
bocly of the sample and surface crazing. Marks in the range 1 to 5 were
awarded for each quality higher marks representing better performance.
The results are summarised in the following table:-

1"12'~'7~6
E ~ ~ C~ o
._ ~ C~ l N . C~J C~l
_ O ~IJ O O O O O O ~ O O
S l~t~
~O _ O ~D ~ O
C~l C`
V ~
~ a:l ~ ~ ~ C ~D ,
E ~ v~ . ~1 ~
~ , ~ ~., ~ ~ ~ ~ ~ ~ ~ $ ~
4 t~ ~ ~
_ ~ ~'~
c~ ~a~
a~ u a~
V ~ ~ L~ o ~o
I ~ a~ ~v
E U v~ : ~ ~
ec ~ L ~ ~ ~ L~> ~) 3
CV ~ ~
~ a~ ~n 3
~ ~ ~ ~ ~ ~ Ln Ln Ln ~ S C
'~ . . ~
~ ~ CL
,~ el o
~ * * O * E >~ E :~ 00 C ~ C ~ O
c ~ O a~ c ~ C t _ ~ --~ ~ ~ .~ --C a~ s
._ . u~ O 10 3 a~ 3 C
E E 1~ E ~ ,
~- ~ T Y ~ 2 ~ Z ~ ~ I
EQ-- E~
x _ c~l ~ ~ ~ cl: m ~ ~ ~ ~ *
L~
C~7 ~4