Rosin ester derivative as surfactants

Surfactant obtainable by and method for the production thereof comprising (1) esterifying a rosin with an alcohol to an acid value of less than 30, (2a) grafting the rosin ester with an unsaturated carboxylic acid or anhydride, the mole ratio carboxylic acid or anhydride/rosin (calculated as each rosin associated with a rosin ester) being from 0.05:1-1.5:1, (3a) esterifying the grafted rosin ester with a polyethylene glycol with an Mw of 1000-20000 the mole ratio glycol/free carboxylic acid group being from 0.2:1-1:1 to an acid value of less than 30, alternatively (2b) esterifying an unsaturated carboxylic acid or anhydride with a polyethylene glycol with a Mw of 1000-20000 the mole ratio glycol/free carboxylic acid group or anhydride being from 0.2:1-1:1 to an acid value less than 30, (3b) grafting the rosin ester from (1) with the ester from (2b), the mole ratio ester from (2b)/rosin ester (calculated as in (2a)) being from 0.05:1-1.5:1. The invention also relates to the use of the surfactant as a dispersing agent for tackifiers, to an aqueous tackifier dispersion comprising the surfactant as well as to the use of the aqueous tackifier dispersion in a pressure sensitive adhesive.

The present invention relates to a new surfactant, to a process for the 
production thereof and to the use of the surfactant as a dispersing agent 
for tackifiers. The invention also relates to aqueous tackifier 
dispersions including the new surfactant and to the use of the aqueous 
tackifier dispersions in pressure sensitive adhesives. 
Pressure sensitive adhesives based on e.g. aqueous acrylic and carboxylated 
styrene butadiene polymers are usually formulated to include a tackifier. 
The tackifier facilitates the coating process for the adhesive and 
improves the adhesive properties such as tackiness, peel-resistance and 
ease of surface wetting. The tack of an adhesive enables it to form an 
immediate bond between contacted surfaces when they are brought together. 
Tackifier resins consist mainly of rosin and derivatives thereof or 
hydrocarbon resins. In aqueous based adhesives it is common to include the 
tackifier resin in the form of an aqueous dispersion. The aqueous 
dispersion is made by first melting the rosin or resin and then adding a 
surfactant and water to form a dispersion in which the rosin/resin is the 
dispersed phase and water the continuous phase. A to of different 
surfactants are known. As typical surfactants there can be mentioned alkyl 
sulphonates, fatty alcohol sulphates, phosphate esters. GB 2 155 942 
relates to a surfactant comprising a salt of a sulphosuccinate half ester 
of an alkoxylated, fortified rosin. The drawback with known tackifier 
dispersions is that they reduce the cohesive strength (internal strength) 
of the adhesive dramatically. This is due to a combined effect of the 
lower molecular weight of the tackifier, compared with polymer resin, and 
the kind of surfactant used in the tackifier dispersion. 
It is accordingly an object of the present invention to obtain a surfactant 
for the preparation of tackifier dispersion with reduced loss in cohesive 
strength when formulated compared to known tackifier dispersions. It is 
further an object of the present invention to obtain a tackifier 
dispersion which is stable at room temperature and which has a good 
mechanical stability and low foaming characteristics. 
The objects of the invention are achieved by a surfactant as claimed in the 
claims. The surfactant is obtainable by 
(1) esterifying a rosin with an alcohol to an acid value of less than 30, 
(2a) grafting the rosin ester with an unsaturated carboxylic acid or 
anhydride, the mole ratio carboxylic acid or anhydride/rosin (calculated 
as each rosin associated with a rosin ester) being from 0.05:1-1.5:1, 
(3a) esterifying the grafted rosin ester with a polyethylene glycol with a 
Mw of 1000-20000, the mole ratio glycol/free carboxylic acid group being 
from 0.2:1-1:1 to an acid value of less than 30, alternatively 
(2b) esterifying an unsaturated carboxylic acid or anhydride with a 
polyethylene glycol with a Mw of 1000-20000, the mole ratio glycol/free 
carboxylic acid group or anhydride being from 0.2:1-1:1 to an acid value 
less than 30, 
(3b) grafting the rosin ester from (1) with the ester from 
(2b), the mole ratio ester from (2b)/rosin ester (calculated as in (2a)) 
being from 0.05:1-1.5:1. 
Similar surfactants are known from U.S. Pat. No. 4,260,550 but for quite 
different purposes. These surfactants are used in cream and lotion and 
hair care formulations. 
It was surprisingly found that with the new surfactants according to the 
invention stable tackifier dispersions could be prepared which resulted in 
adhesives with improved cohesive strength compared with known tackifier 
systems but without detrimentally affecting the adhesive performance. With 
some polymer binders the tackifier dispersion according to the invention 
even maintains the same cohesive strength as with the neat polymer. 
The surfactant according to the invention is prepared from a rosin. Rosin 
is a natural product consisting of mixed unsaturated acids. The rosin 
acids are mainly monobasic carboxylic acids containing the phenanthrene 
skeleton with 20 carbon atoms in the molecule. The difference between the 
acids is the number and position of the double bonds. Natural rosin may be 
classified due to its origin namely as gum rosin, wood rosin or tall oil 
rosin. The surfactant according to the invention can be prepared from any 
of these rosins or from mixtures thereof. 
It is also possible to start with a disproportionated rosin. 
Disproportionation is a method of stabilizing the rosin. It involves 
transferring hydrogen atoms from one molecule of abietic acid to another. 
It is carried out by heating a rosin at 100.degree. to 300.degree. in the 
presence of a disproportionation catalyst. Examples of disproportionation 
catalyst are supported or non supported metals such as palladium, nickel 
and platinum iodine, iodides such as iron iodide, SO.sub.2 and sulphides 
such as iron sulphide. The catalyst is employed in the amount of 0.1% to 
5% by weight on the basis of the amount of a rosin employed. The 
disproportionated rosin prepared in the above manner has preferably a 
content of abietic acid of not more then 5% by weight. 
In the first step to obtain the surfactant, according to the invention, the 
rosin is esterified with an alcohol. The esterification of the rosin can 
be carried out by usual methods for instance, it is carried out by heating 
rosin with a mono or polyhydric alcohol in a closed or open reaction 
vessel in the presence or absence of an esterifying catalyst and in the 
presence of or absence of a solvent at 180.degree. C. to 300.degree. C., 
preferably 200.degree. C. to 290.degree. C. for 1 hour to 20 hours, 
preferably 5 to 15 hours. 
Examples of esterifying catalysts employed if desired are acidic catalysts 
such as sulphuric acid, acetic acid, hypophosphorous acid and p-toluene 
sulphonic acid, alkaline earth metal hydroxides such as calcium hydroxide, 
metal oxides such as magnesium oxide and calcium oxide, carbonates such as 
calcium carbonate and acetates such as magnesium acetate and calcium 
acetate. 
As alcohols mono or polyhydric alcohols can be used. Use is suitably made 
of polyhydric alcohols and preferably of straight or branched chain non 
aromatic polyhydric alcohols containing 2 to 18 carbon atoms. Suitable 
alcohols are glycols such as triethylene glycol, diethylene glycol, 
polyethylene glycol, glycerol, trimethylolethane, trimethylolpropane, 
pentaerythritol, diglycerol, dipentaerythritol, mannitol, sorbitol, 
hexitol, decanol and methanol. Triethylene glycol, glycerol and 
pentaerythritol are preferred. The alcohols may be-employed alone or in 
combination. 
The alcohol is preferably employed in such an amount that the ratio of the 
hydroxyl equivalents of the alcohol to the carboxyl equivalents of the 
rosin is in the range from 1.0:1.0 to 1.5:1.0. 
The rosin ester obtained by esterifying the rosin in the manner described 
above has a softening point of -30.degree. C. to 140.degree. C. and has an 
acid value of not more than 30 mg KOH/g and preferably not more than 25 mg 
KOH/g. 
In the next step the esterified rosin is grafted with an unsaturated 
carboxylic acid or anhydride. Preferably the carboxylic acid is an 
.alpha.-.beta. ethylenically unsaturated acid which is grafted onto the 
rosin by reaction with the unsaturation in the rosin acids. A common 
reaction between the unsaturated acid and the rosin acid is the 
fortification reaction. In this reaction a Diels-Alder adduct is formed 
from a conjugated double bond of the rosin acid and the .alpha.-.beta. 
unsaturated carboxylic acid or anhydride. As suitable acids can be 
mentioned fumaric acid and its half esters, maleic acid (and anhydride) 
and its half esters, acrylic acid, methacrylic acid and related acryl and 
aryl acids, itaconic acid (and anhydride), and oligomers and copolymers of 
acrylics and vinyls with ethylenically unsaturated acids styrene/acrylic 
acids copolymer, etc). The fumaric acid and maleic acid (and anhydride) 
are the preferred ones. 
The unsaturated carboxylic acid is reacted in the mole ratio of 
0.05:1-1.5:1, preferably 0.2:1-0.8:1 with each rosin associated with a 
rosin ester, i.e. a pentaerythritol rosin ester has a maximum of 4 rosins 
associated with it, whilst a glycerol ester has a maximum of 3. The final 
acid value should at least be greater than 30. The reaction temperature is 
from about 170 to about 220.degree. C. 
Then in the final step the grafted/fortified rosin ester is further 
esterified with a polyethylene glycol with a Mw of 1000-20000. The Mw of 
the polyethylene glycol is preferably 4000-16 000, more preferably 
5000-12000, and most preferably 8000-12000. Polyethylene glycol is 
suitably reacted in the mole ratio of 0.2:1-1:1 with each free carboxylic 
group, so that the final acid value is less than 30 and preferably less 
than 25, and most preferably less than 5. The reaction is suitably 
undertaken at a temperature of between 180.degree. C. to 300.degree. C. 
preferably at 240.degree. to 290.degree. C. for 1 hour to 20 hours, 
preferably 5 to 15 hours in the presence of a catalyst. As suitable 
catalysts can be mentioned acidic catalysts such as sulphuric acid, acetic 
acid, hypophosphorous acid and p-toluene sulphonic acid, alkaline earth 
metal hydroxides such as calcium hydroxide, metal oxides such as magnesium 
oxide and calcium oxide, carbonates such as calcium carbonate and acetates 
such as magnesium acetate and calcium acetate. 
Alternatively the reaction between the carboxylic groups of the unsaturated 
acid/anhydride and the polyethylene glycol is carried out first and the 
grafting of the esterified rosin is carried out with the polyethylene 
glycol ester of the unsaturated acid/anhydride. This manner of production 
gives a lower yield than the first reaction mode but it is a possible way 
of production. 
The surfactants according to the invention are preferably used as 
dispersing agents to prepare tackifier dispersions, though other 
surfactant applications are possible. Preferably the tackifier dispersion 
is a dispersed rosin. The tackifier rosin can be an unmodified or a 
modified rosin. There are a lot of different ways of modifying rosin. The 
rosin can be partially fortified or esterified, preferably the rosin is a 
glycerol, pentaerythritol or triethylene glycol ester. The rosin can be 
treated with paraformaldehyde in the presence of paratoluene sulphonic 
acid to inhibit crystallization or it can be stabilized by 
disproportionation. Rosins partially saponified with sodium or potassium 
hydroxide or with a volatile base (ammonia or a lower amine such as 
triethanolamine) is also useful. The different kinds of rosin can be used 
as such or in mixtures of two or more. It is also possible to incorporate 
a C.sub.5 to C.sub.9 hydrocarbon resin. 
When preparing the tackifier dispersion the rosin is first melted and the 
surfactant according to the invention is added as a concentrate or in an 
aqueous solution. The surfactant is suitably added in an amount of 2-15% 
by weight based on the weight of tackifier resin, preferably 5-8%. 
Sufficient hot water (e.g. 20 to 40% based on the weight of tackifier 
resin) is stirred in to form a creamy water in oil emulsion. On dilution 
with water the emulsion inverts to provide a stable oil in water emulsion, 
typically having a solids content of 20% to the maximum achievable oil in 
water concentration, preferably 50-60% by weight solids. 
The preferred physical properties of a tackifier dispersion are that the 
total solids content is greater than 50%, the mean particle size is less 
than 2.0 microns and maximum viscosity is 1000 cps (Brookfield 3/50 rpm). 
It is preferred that the tackifier dispersion has a stable shelf life of 
six months and will demonstrate no separation, coagulation or deposition. 
It is also preferrad that the dispersion is low foaming and have good 
mechanical stability during pumping, transportation and mixing, as well as 
low foaming and good stability when formulated and during coating. The 
surfactant should allow the release of water after coating when passed 
through the drying ovens. By using the surfactant according to the 
invention it is possible to prepare a tackifier dispersion which exhibits 
the desired physical properties. 
If required, small quantities of anionic surfactants, preferably less than 
1%, can be incorporated into the dispersion. However, tackifier 
dispersions manufactured solely with these anionic surfactants have a 
negative effect upon the cohesive strength of a formulated pressure 
sensitive adhesive. Typical anionic surfactants include alkyl aryl 
sulphonates, such as sodium or calcium alkyl benzene sulphonates, fatty 
alcohol sulphates, eg sodium lauryl sulphate, phosphate esters, eg the 
sodium salts of mono- and di-esters of orthophosphoric acid, esters of 
sulphosuccinic acid, the sodium salts of sulphated monoglycerides and 
sulphonates or sulphosuccinates of alkyl phenol polyoxyalkylene oxide 
condensates or of polyoxyalkylene oxide condensates, eg the ammonium salt 
of nonylphenol polyethylene oxide sulphonic acid. 
A pressure sensitive adhesive is prepared by blending the tackifier 
dispersion with a latex or combination of latices using conventional 
blenders to provide a homogenous mixture in an amount of 20 to 150 parts 
by weight per 100 parts of dry polymer in the latex, preferably 20 to 100 
parts by weight per 100 parts of dry polymer. 
A variety of polymer latices can be used preferably derived from natural or 
synthetic rubbers or elastomers such as styrene-butadiene copolymers, 
natural rubbers. polychloroprene, acrylonitrile-butadiene or alternatively 
latices derived from various acrylic or vinyl latices such as ethyl hexyl 
acrylate, butyl acrylate, methyl methacrylate, ethyl acrylate copolymers, 
ethylene vinyl acetates etc. 
The prepared adhesive can be coated on a suitable carrier and dried. As 
suitable carriers can be mentioned, in the case of tapes and labels, a non 
woven material eg. paper, a woven material eg. cotton; a homopolymer of an 
unsaturated monomer such as ethylene, propylene or vinyl chloride or the 
carrier can be of polyester or polyamide. 
The adhesive composition is applied to the carrier by conventional coating 
techniques such as roller coaters, blade coaters, meyer rods or air 
coaters and dried by passing through a heating tunnel or oven. The 
adhesive coat is either applied directly or by transfer coating. 
The dry coat weight is suitably from 15 to 70 gsm. For packaging tapes and 
label applications the dry coat weight is generally from 15 to 30 gsm and 
for masking tapes about 30 to 60 gsm.

The invention is now illustrated by means of the following examples, where 
parts and percentages mean parts by weight and percentages by weight 
unless otherwise specified. 
EXAMPLE 1 
100 g rosin was heated under a nitrogen blanket at 280.degree. C. with 
constant agitation in combination with 15 g glycerol in the presence of 
0.23 g zinc oxide catalyst for 8 hours to obtain a product of acid value 
10mg KOH/g, ring and ball 88.degree. C. 
95 g of the glycerol ester from above was cooled to 180.degree. C. and 
reacted with 9.5 g maleic anhydride for 4 hours until the water soluble 
acid value was less than 5 mg KOH/g, to obtain a product of acid value 
63.0 mg KOH/g, ring and ball 134.degree. C. This product was further 
reacted with 950 g polyethylene glycol with a Mw of 8000 at 280.degree. C. 
in the presence of 2 g paratoluene sulphonic acid for 14 hours. The final 
acid value was 2.5 mg KOH/g, ring and ball 55.0.degree. C. 
400 g of a pentaerythritol ester of rosin, (AV=18 mg KOH/g ring and 
ball=85.0.degree. C.), was warmed in a pot to 110.degree. C. When molten 
with stirring 2.4 g of a 50% solution of KOH was added followed by 24.0 g 
of the above produced surfactant. 70 ml hot water was added to obtain the 
inversion followed by 260 ml hot dilution water to obtain a stable 
dispersion of mean particle size 1.5 microns. The viscosity was 280 cps 
(Brookfield 3/50rpm) and solids content 55.4%, dried film ring and ball 
83.4.degree. C. 
This rosin dispersion has a minimum 6 months shelf storage stability, low 
foaming characteristic and good shear stability. 
60 parts and 80 parts (by dry weight) of the tackifier dispersion, prepared 
above (Tackifier A) were blended separately to each of 100 parts (by dry 
weight) of butyl acrylate polymer (Acronal.TM. 3433) using a laboratory 
shear blender. The adhesive was coated to silicone release liner using a 
meyer bar and then dried at 90.degree. C. for 10 minutes in a fan assisted 
oven to obtain a target coat weight of 20 gsm, before laminating to 80 gsm 
face paper. The laminate was conditioned at 50 relative humidity at 
23.degree. C. before assessing the adhesive properties. The following 
tests were applied to 25 mm strips of the coated samples: 
Shear: 1860 g weight applied to 25 mm sq. sample bonded to a vertical glass 
surface. 
Glasspeel: 180.degree. peel after 20 minutes adhesion to glass after being 
applied by rolling a 2 kg roller the length of the sample in both 
direction twice. FINAT Test Method 1. 
Polypeel: 180.degree. peel after 20 minutes adhesion to untreated 
polyethylene sheet after being applied as in 2. 
Looptack: Instantaneous tack to stainless steel. FINAT Test Method 9. 
Polytack: Instantaneous looptack to untreated polyethylene sheet. 
The test result is given below. Tackifier A is the tackifier dispersion 
according to the invention. Tackifier B is a tackifier dispersion with the 
same pentaerythritol ester of rosin as in the example above but with a 
conventional surfactant. The surfactant was an alkyl phosphate. To both 
tackifier dispersions 0.3 parts potassium hydroxide was added as a co 
stabilizer. 
______________________________________ 
100 parts dry Acronal .TM. DS 3433 
% Tackifier 
Shear Glasspeel 
Polypeel 
Looptack 
Polytack 
parts (dry) 
(Hr) (N) (N) (N) (N) 
______________________________________ 
-- 11.8 10.4 2.7 10.0 4.4 
80 Tackifier 
12.8 PT 8.1 22.1 5.7 ss 
60 Tackifier 
8.4 PT 8.2 21.1 11.2 
A 
80 Tackifier 
6.3 PT 1.9-4.1 ss 
17.8 3.2 ss 
B 
60 Tackifier 
6.9 PT 8.5 19.1 10.6 
B 
______________________________________ 
(PT means Paper Tear and ss means Slipstick Mode of Failure). 
EXAMPLE 2 
Example 1 was repeated with 2-Ethyl hexyl acrylate (Acronal.TM. V205) as 
the polymer instead of butylacrylate. The results were as follows: 
______________________________________ 
100 parts dry Acronal .TM. V 205 
% Tackifier 
Shear Glasspeel 
Polypeel 
Looptack 
Polytack 
parts (dry) 
(Hr) (N) (N) (N) (N) 
______________________________________ 
-- 10.4 PT 5.5 9.8 6.6 
40% Tacki- 
3.8 PT 1.5-3.2 ss 
PT 2.6 ss 
fier A 
30% Tacki- 
3.0 PT 9.3 23.8 6.2 ss 
fier A 
40% Tacki- 
2.0 PT 1.5-7.7 ss 
21.2 3.2 ss 
fier B 
30% Tacki- 
1.8 PT 1.6-7.7 ss 
23.0 6.0 ss 
fier B 
______________________________________ 
(PT means Paper Tear and ss means Slipstick Mode of Failure). 
EXAMPLE 3 
100 g rosin was heated under a nitrogen blanket at 275.degree. C. with 
constant agitation in combination with 24.1 g triethylene glycol (TEG) in 
the presence of 0.2 g hypophosphorous acid catalyst for 11 hours to obtain 
a product of acid value 24 mg KOH/g, liquid at 23.degree. C. 
45 g of the TEG ester from above was cooled to 180.degree. C. and reacted 
with 4.5 g maleic anhydride for 4 hours until the water soluble acid value 
was less than 5 mg KOH/g, to obtain a product of acid value 41.6 mg KOH/g, 
ring and ball 66.2.degree. C. This product was further reacted with 500 g 
polyethylene glycol with a Mw of 10000 at 275.degree. C. in the presence 
of 1.1 g hypophosphorous acid for 16 hours. The final acid value was 2.5 
mg KOH/g, ring and ball 63.0.degree. C. 
400 g of a glycerol ester of rosin, (AV=13 mg KOH/g ring and 
ball=86.0.degree. C.), was warmed in a pot to 110.degree. C. When molten 
with stirring 2.4 g of a 50% solution of KOH was added followed by 24.0 g 
of the above produced surfactant. 70 ml hot water was added to obtain the 
inversion followed by 260 ml hot dilution water to obtain a stable 
dispersion of mean particle size 1.5 microns. The viscosity was 560 cps 
(Brookfield 3/50rpm) and solids content 60.0%, dried film ring and ball 
80.8.degree. C. This is tackifier C. 
Adhesive performance (coating and testing as described in Example 1). 
______________________________________ 
70 parts dry Acronal .TM. V 205 
Tackifier C 
Shear Glasspeel 
Polypeel 
Looptack 
Polytack 
parts (dry) 
(Hr) (N) (N) (N) (N) 
______________________________________ 
30 2.8 PT 1.7-6.9 ss 
22.1 5.3 ss 
______________________________________ 
(PT means Paper Tear and ss means Slipstick Mode of Failure).