Emulsifiers and a process for the production of large particle size, homodisperse polymer dispersions using these emulsifiers

This invention relates to emulsifiers and to the production of large particle size, homodisperse polymer dispersions using these specific dispersion aids (emulsifiers) which show an unobvious effect.
In the context of the invention, "homodisperse" dispersions (latices) are those in which the latex particles have a narrow diameter distribution. Average latex particle diameters are defined for instance as average volume diameter DAV or as average number diameter DAN of the particles as follows: ##EQU1## (c.f. DIN 53 206),
The DAV/DAN ratio may be regarded as defining uniformity.
"Large" particle size dispersions may be those wherein the average particle diameter DAN is from 150 to 600 nm and preferably from 250 to 450 nm. Latices having a DAV/DAN ratio of <1.15 may be called "homodisperse".
It is known that large particle size polybutadiene latices are required for the production of high-impact thermoplastic molding compounds (for example high-impact polystyrene, ABS polymers). Basically, coarsely divided (rubber) latices may be prepared using standard emulsifiers by the seed latex method (cr. Houben Weyl, Methoden der Organischen Chemie, Makromolekulare Stoffe, Part 1, 1961, Thieme Verlag Stuttgart, page 339).
Emulsifiers based on the naturally occurring resin acids ("resin soaps") have been used for the production of polybutadiene latices, butadiene-styrene copolymer latices, polychoroprene latices. However, "resin soaps" promote the formation of new latex particles, so that undesirable finely divided, even dimodal or polymodal latices are formed.
Accordingly, though resin soaps have proved to be suitable for the production of finely divided polybutadiene and butadiene-styrene copolymer latices having favorable natural color and processibility, they are less suited to the production of homodisperse, large particle size latices.
The present invention is based on the discovery that large particle size latices can readily be obtained by using special emulsifiers in the batch emulsion polymerization, semicontinuous emulsion polymerization and continuous seed emulsion polymerization processes known per se.
The present invention relates to reaction products of 1 mol of a cycloaliphatic diol corresponding to formula I
HO--R--OH I
with 2 mols cycloaliphatic carboxylic anhydrides corresponding to formulae II and/or III ##STR3## in which R is a cycloaliphatic hydrocarbon radical containing 6 to 20 and preferably 6 to 15 carbon atoms, to which the hydroxy groups are attached directly or via methylene groups and
X represents ##STR4## chemical bond which reaction products are obtainable by fusion of the cycloaliphatic diol and of the cycloaliphatic carboxylic anhydride in an inert gas atmosphere at temperatures of from 100.degree. C. to 250.degree. C. and to the alkali and ammonium salts of these reaction products.
The invention also relates to their use as emulsifiers.
Reaction products of 1 mol (I) and 2 mols (II) or of 1 mol (I), 1 mol (II) and 1 mol (III) are preferred.
The new reaction products (emulsifiers) are alkali or ammonium salts of acidic resins which are obtained by reaction of 1 mol of a cycloaliphatic diol with 2 mol of a cycloaliphatic anhydride or with an anhydride mixture, for example by reaction of 1 mol of a cycloaliphatic diol with maleic anhydride and/or itaconic anhydride.
The reaction products according to the invention can be represented by the following general formula
Y.sub.1 --O--R--O--Y.sub.2 (IV)
in which the Y's independently represent ##STR5## in which X and R are as defined above.
In formula (IV), R is a cycloaliphatic radical with two bonds, a "spacer" for the two, preferably dimetrically opposite, hydroxyl groups attached to the ring system either directly or via a methyl group.
The substituents R may be cycloaliphatic ring systems, for example, of 6-membered or 5-membered and 6-membered optionally alkyl-substituted rings. Such ring systems can readily be synthesized, for example, from dienes and dieneophiles by the DIELS-ALDER reaction. Preferred substituents R are: ##STR6##
The diols required as starting product may be obtained in known manner by hydroformylation of cyclic dienes or of saturated aldehydes or alcohols with subsequent reduction of the aldehyde group (cf. Methodicum Chimicum, Kritische Ubersicht bewahrter Arbeitsmethoden und ihre Anwendung in Chemie, Naturwissenschaft und Medizin (Critical Review of Proven Methods and their Application in Chemistry, Natural Science and Medicine), Ed. F. Korte, G. Thieme Verlag, Stuttgart, 1975, pages 212 to 215).
Other diols are obtained by hydrogenation of the corresponding aromatic compounds such as, for example, hydroquinone or by addition of water onto the corresponding diolefins.
Particularly suitable diols are 1,4-cyclohexanediol, 1,4-bis-hydroxymethyl cyclohexane, bis-hydroxymethyl hexahydro-4,7-methanoindane (commercially available as "TCD-Diol" produced by hydroformylation of dicyclopentadiene) (U.S. Pat. No. 2,850,536), bis-hydroxymethylbicyclo-(4,3,0)-nonane, bis-hydroxymethyl norbornane, bis-hydroxymethyl cyclooctane.
The diols mentioned are generally isomer mixtures.
Anhydrides which may be reacted with the diols mentioned include hexahydrophthalic anhydride, tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, norbornane dicarboxylic anhydride, maleic anhydride and itaconic anhydride.
The last two anhydrides are preferably reacted with the diols mentioned above in combination with saturated anhydrides. Copolymerizable emulsifiers are obtained.
The diols may preferably be reacted with the anhydrides in bulk (in the melt). With small batches, the diol may be mixed with the anhydride and reacted in the melt. With larger batches, the molten components are preferably added separately from one another to a melt of already formed reaction product. In most cases, it is also of advantage initially to introduce the anhydride or anhydride mixture and than to add the diol thereto. In the production of asymmetrical emulsifier acids, it is even possible to introduce the diol first and then to add the anhydride of formula II and, lastly, maleic or itaconic anhydride.
The reaction may be accelerated by small quantities of a tertiary amine, such as triethylamine or tributylamine. The end of the reaction may be recognized by determination of the acid value of the melt and from the disappearance of the anhydride band in the infrared spectrum. The reaction mixtures may be characterized by their acid value and by GPC analyses.
The reaction of the diols with the anhydrides is preferably carried out in an inert gas atmosphere at temperatures in the range from 100.degree. to 250.degree. C. and preferably at temperatures in the range from 100.degree. to 200.degree. C. Nitrogen or argon is preferably used as the inert gas.
The pure substances (isomers), e.g. those corresponding to the formulae shown in Table 1, do not have to be isolated from the reaction mixtures for the use as emulsifiers in accordance with the invention. The diolefins used for hydroformuylation may themselves consist of mixtures. For example, dicyclopentadiene consists of a mixture of cis- and trans-Diels-Alder adduct. In the hydroformylation reaction, the number of isomers is further increased so that the diols used for reaction with the dianhydrides are generally mixtures of isomers. Accordingly, the formulae in Table 1, column 1, may be interpreted as isomer mixtures and the molecular weight in column 2 is that of the isomer mixture.
On completion of the reaction and after volatile constituents, particularly excess anhydrides, have been removed by distillation or sublimation, the reaction mixtures formed during the reaction of cyclic diols with the anhydrides mentioned are drained from the reactor while still hot and, after cooling, are comminuted to granulate or powder, In general, the reaction products are light resins with softening points above +20.degree. C. some of the resins show a tacky consistency reminiscent of natural resins. These properties of the emulsifiers may be desirable in the production of butadiene-styrene copolymers.
In the production of emulsion polymers comprising large particles, it is important to prevent formation of new particles during polymerization.
Formation of new particle in emulsion polymerization does not necessitate the existence of free micelles; new particles can also be formed when the quantity of emulsifier added is not sufficient for forming new micelles cf, A. S. Dunn in the Article "Emulsion Polymerization", pages 49-50, in Developments in Polymerization, Ed. by R. N. HAWARD, Applied Science Publishers Ltd, 1979).
How latex particles are formed is still not fully known (cf. N. Sutterlin, H. J. Kurth, G. Markert, Makromolekulare Chemie 177, 1549-1565 (1976)), more especially page 1550, introduction, sentence 2).
It was neither foreseeable nor to be expected that the reaction products according to the invention are particularly suitable for the production of large particle size, homodisperse rubber latices, (e.g. polybutadiene latices) particularly where polymerization is carried out at elevated temperature in an alkaline medium. On the contrary, saponification and loss of emulsifier properties was expected.
It has now been found that stable, large particle size, homodisperse latices can be produced with the reaction products according to the invention as emulsifiers and that coagulate formation is no more pronounced than with conventional emulsifiers. Surprisingly, only a small quantity of emulsifiers according to the invention is required.
Examples of emulsifier acids according to the invention are shown in Table I, numbers 1 to 3, 5 and numbers 7 to 9. They are generally dicarboxylic acids of which the alkali (Li, Na, K, ammonium) salts are soluble in water and act as emulsifiers in emulsion polymerization. The Na or K salts are preferably used.
The emulsifier-acids according to the invention are soluble, particularly in powdered form, in aqueous alkali hydroxides. An excess of alkali hydroxide is not necessary for dissolution and should be avoided. However, since the emulsifiers according to the invention are mostly used in combination with potassium peroxodisulfate for the polymerization of olefinically unsaturated compounds and since protons are formed during the decomposition of potassium peroxodisulfate, it is advisable additionally to introduce water-soluble base in such a quantity that the polymerization takes place at pH 8-12 and preferably at pH 10.5-11.5.
Butadiene, styrene, mixtures of butadiene and styrene, mixtures of butadiene and acrylonitrile and sparingly water-soluble acrylates or methacrylates and also vinyl esters are mentioned in particular as monomers which may be polymerized to coarsely divided aqueous dispersions using the emulsifiers according to the invention. In addition, the new emulsifiers are also suitable for the polymerization of mixtures of acrylonitrile with styrene and/or .alpha.-methyl styrene. Halogen-containing monomers, such as vinyl chloride and chloroprene may also be polymerized, in which case polymers of increased particle diameter and improved thermal stability are obtained.
The emulsifiers according to the invention are also suitable for the production of graft rubber latices and, in particular, for the production of graft rubber latices based on polybutadiene or butadiene/styrene copolymers or butadiene/acrylonitrile copolymers, suitable graft monomers including, for example., styrene, .alpha.-methyl styrene, acrylonitrile, methyl methacrylate or mixtures of these monomers, preferably styrene and alcrylonitrile in a ratio by weight of 95:5 to 60:40. Graft rubber latices of this type have rubber contents of 5 to 95% by weight and preferably 20 to 90% by weight and, after working up, for example by electrolyte coagulation and drying or by spray drying, may be converted into graft rubber powders which are suitable, for example, for the production of ABS polymers characterized by excellent thermal stability. ABS molding compounds of the type in question consist, for example, of 10 to 80% by weight and preferably 20 to 70% by weight of a graft rubber of styrene and acrylonitrile or methyl methacrylate on a particulate rubber having an average particle diameter d.sub.50 of 0.05 to 2 .mu.m and a rubber content of 20 to 90% by weight and of 90 to 20% by weight and preferably 80 to 30% by weight of a thermoplastic resin of 5 to 40 parts by weight acrylonitrile and 95 to 60 parts by weight styrene, .alpha.-methyl styrene, p-methyl styrene, methyl methacrylate or mixtures thereof.
Large particle size dispersions, more especially polybutadine dispersions, can be produced by standard emulsion polymerization processes. According to the invention, the new emulsifiers are used in the production of such dispersions. Where particularly homodisperse and large particle size latices are to be produced, a seed latex containing only a little emulsifier is initially introduced and monomers and aqueous emulsifier and initiator-solution is added continuously thereto.
Potassium peroxodisulfate is normally used as initiator, but redox systems of organic perioxides, reducing components and heavy metal traces, preferably in complexed form, may also be used. Other radical-forming compounds, such as azo-bis-isobutyronitrile and derivatives thereof containing water-solubilizing auxiliary groups, are also suitable.
TABLE I__________________________________________________________________________ Reaction mixture solidif- Acid Acid Structural formula Molecular point value valueNo. (not considering isomers) .degree.C. Time weight [.degree.C.] calc. found__________________________________________________________________________ ##STR7## 110 3 C.sub.28 H.sub.40 O.sub.8 :504.6 50-54 222.4 228 ##STR8## 110 3 C.sub.24 H.sub.32 O.sub.8 :448.5 34-36 250.2 253 ##STR9## 120 3 C.sub.30 H.sub.40 O.sub.8 :528.6 47-50 212.3 220 4.* ##STR10## 130 17 C.sub.28 H.sub.28 O.sub.8 :492.5 48-52 227.9 200 ##STR11## 110 4 C.sub.20 H.sub.24 O.sub.8 :392.4 21-23 286 280 6.* ##STR12## 130 4 C.sub.20 H.sub.28 O.sub.8 :396.4 7- 10 283.1 283 ##STR13## 120 3 C.sub.25 H.sub.34 O.sub.8 :462.5 20-23 242.6 250 ##STR14## 120 3 C.sub.22 H.sub.32 O.sub.8 :424.5 50-60 264.4 270 ##STR15## 120 3 C.sub.24 H.sub.36 O.sub.8 :452.5 46-50 248.0 25510* ##STR16## 150 4 C.sub.34 H.sub.54 O.sub.8 :590.8 64-67 189.9 203__________________________________________________________________________ *does not correspond to the invention The reaction temperature and reaction time for the production of the acidic emulsifier resins are shown in columns 3 and 4

EXAMPLES 1 to 36
The acidic emulsifier resins 1 to 3, 5 and 7 to 9 (according to the invention) and comparison resins 4, 6 and 10 are dissolved in the equivalent quantity, based on the measured acid value, of aqueous potassium hydroxide and adjusted to a solids content of 5% by weight. These resins are identified in Table I and were produced by melting together one mol of a cycloaliphatic diol and two mols of a cycloaliphatic anhydride.
Tables II to V show the polymerization results obtained where various monomers (styrene, n-butyl acrylate, vinyl versatate, ethyl acrylate) and various emulsifier resins are used. The average particle diameters d.sub.T shown were determined by turbidimetry (see H. Lange Kolloid-Z.Z. Polymere 223, 24-30 (1968)).
The emulsifier resins are less suitable for the polymerization of vinyl acetate, vinyl propionate and ethyl acrylate.
The polymerizations were carried out in corked, 500 ml glass bottles, which were rotated in a water bath for 15 hours at 70.degree. C. in protective baskets, in the absence of oxygen (purging of the mixtures in the bottles with nitrogen or pure argon). The following recipe was used:
______________________________________Water 95.9 parts by weight5% by weight emulsifier solution 69.7 parts by weight1% Na.sub.2 CO.sub.3 solution 15.4 parts by weight1% K.sub.2 S.sub.2 O.sub.8 solution 26.1 parts by weightMonomer 87.1 parts by weightTotal parts by weight 294.2 parts by weight.______________________________________
At complete monomer conversion, latices having a solids content of 30.9% are obtained. In all tests, the emulsifier content is 4%, based on the monomer used, and the initiator content 0.3%, based on monomer.
Tables II to V show that, where emulsifiers of non-invention anhydrides or diols are used, either undesirably finely divided latices are obtained (see tests 4, 9, 13, 18, 22, 27, 31 and 36) or coagulate is formed in very large amounts (see tests 6, 24 and 33). The emulsifiers based on formulae 1, 2 and 9 (cf. Table I), which lead to large particles and are also generally characterized by minimal coagulate formation, proved to be particularly advantageous in the case of styrene and also in the case of butadiene as discussed in the following Examples.
TABLE II______________________________________Polymerization of styreneEx- % Particleam- Solids Coagulate pH diameterple Emulsifier used of latex [g] value d.sub.T (nm)______________________________________1 Di-K-salt of 1 30.8 0.2 9.3 1802 Di-K-salt of 2 30.5 0.4 7.9 2203 Di-K-salt of 3 30.6 <0.1 8.0 100 4* Di-K-salt of 4 30.5 <0.1 8.1 705 Di-K-salt of 5 21.3 10 7.8 360 6* Di-K-salt of 6 24.5 large -- -- amount of coagulate7 Di-K-salt of 8 29.5 5.3 9.8 6008 Di-K-salt of 9 30.4 1.5 9.3 290 9* Di-K-salt of 10 30.8 <0.1 9.2 70______________________________________ *= does not correspond to the invention
TABLE III______________________________________Polymerization of n-butyl acrylateEx- % Particleam- Solids Coagulate pH diameterple Emulsifier used of latex [g] value d.sub.T (nm)______________________________________10 Di-K-salt of 1 30.4 1.3 7.8 13011 Di-K-salt of 2 30.4 1.1 7.5 16012 Di-K-salt of 3 30.3 2.0 7.3 110 13* Di-K-salt of 4 30.4 <0.1 7.6 7014 Di-K-salt of 5 29.3 3.8 7.0 200 15* Di-K-salt of 6 30.0 3.1 6.7 18016 Di-K-salt of 8 29.3 7.2 7.3 26017 Di-K-salt of 9 30.1 2.9 7.4 170 18* Di-K-salt of 10 30.7 0.7 8.1 60______________________________________ *= does not correspond to the invention
TABLE IV______________________________________Polymerization of vinyl versatateEx- % Particleam- Solids Coagulate pH diameterple Emulsifier used of latex [g] value d.sub.T (nm)______________________________________19 Di-K-salt of 1 26.0 1.7 7.8 11020 Di-K-salt of 2 26.8 5.3 7.6 80021 Di-K-salt of 3 26.5 6.1 7.5 370 22* Di-K-salt of 4 30.4 1.8 7.3 8023 Di-K-salt of 5 coagulate 24* Di-K-salt of 6 coagulate25 Di-K-salt of 8 25.8 21.9 6.2 220026 Di-K-salt of 9 28.0 10.6 6.2 1300 27* Di-K-salt of 10 30.2 1.8 8.6 100______________________________________ *= does not correspond to the invention
TABLE V______________________________________Polymerization of ethyl acrylateEx- % Particleam- Solids Coagulate pH diameterple Emulsifier used of latex [g] value d.sub.T (nm)______________________________________28 Di-K-salt of 1 29.4 4.5 7.6 17029 Di-K-salt of 2 28.0 13.5 7.3 21030 Di-K-salt of 3 28.8 9.6 7.3 160 31* Di-K-salt of 4 30.2 2.6 7.2 10032 Di-K-salt of 5 28.8 9.9 7.0 340 33* Di-K-salt of 6 26.7 17.6 6.6 42034 Di-K-salt of 8 26.9 19.4 7.0 47035 Di-K-salt of 9 26.5 16.7 7.2 270 36* Di-K-salt of 10 30.2 1.4 8.0 80______________________________________ *= does not correspond to the invention
EXAMPLES 37
Seed Latex as Starting Material
A seed latex having an average particle size of approx. 100 nm is required for the following Examples. Its production is described in the following:
The following materials are introduced into a 6 liter stainless steel autoclave equipped with an infinitely variable paddle stirrer and internal temperature control:
______________________________________Deionized water 2282.00 gNa salt of disproportionated abietic acid 388.00 g(DRESINATE .RTM. 731), 10% by weight in waterTert.-dodecyl mercaptan, 2.5% by weight 6.00 gK.sub.2 S.sub.2 O.sub.8 solution in water 155.00 gPotassium hydroxide, solid (high purity) 1.15 g______________________________________
The autoclave is evacuated and the reduced pressure is equalized with pure nitrogen (3 times). Butadiene is then introduced into the re-evacuated autoclave:
______________________________________Butadiene 1900.00 gRotational speed of the paddle stirrer: 125 r.p.m. [min.sup.-1 ]______________________________________
The mixture is heated to 65.degree. C. and polymerized for about 20 h until the pressure falls to 4 bar. Approx. 4.6 kg of an approx. 40% polybutadiene latex are obtained. The latex has an average particle diameter DAV of approx. 100 nm, as determined by the ultracentrifuge technique.
EXAMPLES 38 to 41
Comparison
Preparation of polybutadiene latices by seeded semicontinuous polymerization having a particle size of approx. 200 nm.
The polybutadiene latex prepared in accordance with Example 37 is initially introduced as seed latex and butadiene is added thereto in such a quantity that the average latex particle diameter is about doubled in the polymerization.
The polymerization formulations of Examples 38 to 41 for the various polymerization temperatures are shown in Table VI. The mixtures A are initially introduced, the autoclave is repeatedly evacuated and the vacuum is eliminated with nitrogen. After re-evacuation, butadiene (B) is introduced and the polymerization mixture is heated to the particular temperature (60.degree. C. or 70.degree. C. or 80.degree. C. or 90.degree. C.).
Emulsifier/activator solution C is added according to the conversion. One third of C is added at a solids content of the latex of 20% by weight, one third at a solids content of 30% by weight and the remainder at a solids content of 40% by weight. The additions may also be more finely graduated, for example one tenth of C may be added after every 5% increase in the solids content.
The time-solids content relation for this series of tests is shown in Table VII.
It can be seen from Table VII that the polymerization reactions take place much more quickly at elevated temperature.
According to M. Morton and P. P. Salatiello (J. Polymer Science, 8, 215-224 (1952), cf. page 22), the growth constant K.sub.w of the polymerization of butadiene shows the following dependence on temperature:
K.sub.w =1.2.multidot.10.sup.8 exp (-9300/R.multidot.T) [1.multidot.mol.sup.-1 .multidot.sec.sup.-1 ]
Accordingly, the activation energy of the growth reaction is 9300 cal. If the corresponding value in cal (1.986 cal) is used for the gas constant, the following result is obtained:
K.sub.w =1.2.multidot.10.sup.8 exp (-9300/(1.986.multidot.(273.15+.degree. C.))
______________________________________ Temp. [.degree.C.] K.sub.w______________________________________ 0 .about.4 10 8 20 14 30 23 40 38 50 61 60 94 70 142 80 209 90 301 100 425______________________________________ ##STR17## - (to be compared with K.sub.w of other monomers at 60.degree. C.: Styrene: 176; Methacrylic Acid Methyl Ester: 367; See: B. Vollert Grundri.beta. der Makromol. Chemie, Springer (1962) S. 66).
TABLE VI__________________________________________________________________________Example No. 38 39 40 41Polymerization temperature 60 70 80 90__________________________________________________________________________Deionized water (g) 957.00 957.00 957.00 957.00KOH, solid (g) 1.72 1.72 1.72 1.72Polybutadiene latex, 35% 522.00 522.00 522.00 522.00particle diameter 100 nm (g)Na salt of disproportionated 73.00 73.00 73.00 73.00abietic acid, aqueous 10% Asolution (g)(Dresinate .RTM. 731)Tert.-dodecyl mercaptan (g) 4.93 4.93 4.93 4.93K.sub.2 S.sub.2 O.sub.8 solution, 2.5% (g) 164.4 82.2 41.1 20.7(in H.sub.2 O)Butadiene (g) 1461.0 1461.0 1461.0 1461.0 } BDresinate .RTM. 731:Na salt of disproportionated 173.5 173.5 173.5 173.5resinic acid, aqueous 10% Csolution (g)K.sub.2 S.sub.2 O.sub.8 solution, 2.5% -- 82.2 123.3 143.7Coagulate (g) none none 25 noneSolids content % approx. 50% approx. 50% approx. 50% approx. 50%pH value 11.1 10.4 11.2 11.2Flow time, DIN 53 211 21.7 21.4 26.4 24.9[secs.] (4 mm diameter nozzle)LCS diameter [nm] (laser correla- 210 200 198 200tion spectr.)DAN 193.3 164 169 139DAL 195.6 171 174 157DAF (see DIN 199.8 177 178 173DAV 53 206) 208.1 181 181 184DVN 196.2 171 173 156DO* 157 95.2 101 80D10 180 153 157 104D20 184 173 172 181D30 186 174 175 189D40 188 178 178 192D50 190 184 181 195D60 193 188 187 196D70 197 190 189 197D80 204 194 193 200D90 223 199 200 206D100 585 218 218 229DAV/DAN 1.08 1.10 1.07 1.32__________________________________________________________________________ *Particle-Size Distribution according to measurements with the ultracentrifuge (W. Scholtan H. Lange Koll. Z.Z. Polymere, 250, 782-796 (1972)).
TABLE VII______________________________________Time-solids content relation E = 38 39 40 41Time [h] 60.degree. C. 70.degree. C. 80.degree. C. 90.degree. C.______________________________________1 S = 12.5 14.5 15.8 20.52 13.6 17.0 20.0 27.53 15.0 20.0 23.5 34.04 16.0 23.0 27.5 40.05 17.5 26.0 31.5 46.56 18.8 29.0 35.5 49.07 20.0 32.0 39.0 50.08 21.6 35.0 38.59 22.8 38.0 46.510 24.0 40.5 48.711 -- -- 50.015 31.0 45.020 39.0 48.525 44 50.032 49.5______________________________________ E = Example No. S = solids content in % by weight (latex)
Accordingly, an increase in temperature of 10.degree. accelerates the reaction velocity by a factor of approximately 1.5 for a constant monomer concentration and radical concentration in the latex particle.
Table VI shows that, starting from the same seed latex in different ways at 60.degree. to 90.degree. C. there are resulting final latices wherein the average latex particle diameter is approximately 200 nm.
An attempt to produce final latices with average particle diameters of 400 nm from seed latices having an average particle diameter of 100 nm by increasing monomer input, fails as new latex particles are formed when the average particle size of approximately 200 nm is reached. This is true where DRESINATE.RTM. is used as emulsifier and potassium peroxodisulfate as initiator, the formation of new latex particles being the more pronounced, the higher the polymerization temperature and the higher the amount of emulsifier necessary to prevent the formation of coagulate.
EXAMPLES 42 to 49
Efforts for the production of large particle size polybutadiene latices by semicontinuous seed polymerization.
The polybutadiene latices with particle diameters of approximately 200 nm produced in accordance with Examples 38 to 41, Table VI, are used as seed latices (cf. Table VIII, line 6). A same similar polymerization process as in Examples 38 to 41 is applied. The same seed latex is now "enlarged" using the Na salt of disproportionated abietic acid (DRESINATE.RTM. 731) and then as a comparison, a preferred emulsifier according to the invention (dipotassium salt of the acid of formula 1 (cf. Table I) by polymerizing butadiene onto the seed latex. One third of the emulsifier-activator solution C is added when the latex solids content is 20%, one third when the latex solids content is 30% and the remainder when the latex solids content is 40%.
It can be seen from Table VIII that the amount of coagulate is always lower where the emulsifier according to the invention is used than where DRESINATE.RTM. is used.
In addition, particle size determination (by means of ultracentrifuge analysis of the dispersions) as indicated in Table VII, shows that, the emulsifier according to the invention yields larger average latex particle diameters and a narrower latex particle diameter distribution. Accordingly, the DAV/DAN ratio of the final latices is closer to 1.0 where the emulsifiers according to the invention are used than where DRESINATE.RTM. is used.
TABLE VIII__________________________________________________________________________Temperature 60.degree. C. 70.degree. C. 80.degree. C. 90.degree. C.Example No. 42 43** 44 45** 46 47** 48 49**__________________________________________________________________________Deionized water 973.8* 973.8 1052 1052 1052 1052 1052 1052KOH, solid 1.72 1.72 1.72 1.72 1.72 1.72 1.72 1.72Seed latex Example 38 38 39 39 40 40 41 4135% 504.9* 504.9 426.9 426.9 426.9 426.9 426.9 426.910% Dresinate 731 39.6* -- 37.6 -- 41.0 -- 41.7 --solution10% solution emulsi- -- 39.6 -- 37.6 -- 41.0 -- 41.7fier of formula 1 inTable I di-K-saltTert.-dodecyl 4.93* 4.93 4.93 4.93 4.93 4.93 4.93 4.93mercaptanK.sub.2 S.sub.2 O.sub.8 solution, 164.3* 164.3 82.2 82.2 41.1 41.1 20.6 20.62.5%Butadiene 1467* 1467 1494 1494 1494 1494 1494 149410% Dresinate 130.3* -- 147.5 -- 160.8 -- 163.5 --solution10% solution emulsi- -- 130.3 -- 147.5 -- 160.8 -- 164.5fier 1, di-K-saltK.sub.2 S.sub.2 O.sub.8 solution, -- -- 82.2 82.2 123.3 123.3 143.7 143.72.5% *All quantities in [g]- **According to the inventionCoagulate (g) 43 20 64.5 5.6 101.5 2.0 69 44pH value 11.5 12.0 11 11 10.7 11.0 11.5 12.0u = DAV/DAN 1.41 1.03 1.45 1.04 1.19 1.04 1.29 1.04DAN* 174.3 329.5 130.3 250.6 188.3 296.3 148.0 275.2DAL 193.9 332.0 149.0 253.6 203.4 300.2 162.0 278.0DAF 218.5 334.8 169.8 257.0 215.2 304.2 176.4 281.8DAV 245.8 338.2 188.9 260.9 224.2 308.3 191.2 287.2DVN 194.7 332.1 148.8 253.7 -- 300.2 -- 278.4D0 ITGV** 104 270 84 207 102 236 85 219D10 136 296 95 224 195 259 127 242D20 157 314 117 231 204 271 162 253D30 186 322 174 236 207 281 166 263D40 209 327 181 242 212 293 169 277D50 236 332 191 249 219 312 172 287D60 265 337 202 263 227 322 181 294D70 293 343 214 278 233 329 198 300D80 319 350 228 288 244 337 226 306D90 350 364 248 300 275 345 265 314D100 407 555 298 785 312 780 353 1600__________________________________________________________________________ *Definitions according to DIN 53 206 **ITGV -- integral latex particle diameter distribution, as determined by the ultracentrifuge technique ***According to the invention
EXAMPLE 50
According to the Invention
Polybutadiene Latex, Particle Diameter d=200 nm
The following materials are introduced in the absence of oxygen into a 6 liter stainless steel autoclave (operating pressure up to 20 bar) equipped with an infinitely variable paddle stirrer (150 r.p.m.) and internal temperature control:
______________________________________Deionized water 2282.00 gEmulsifier of formula 1, 50.00 gTable I, di-K-saltTert.-dodecyl mercaptan 5.00 g2.5% aqueous potassium peroxodisulfate 155.00 gsolutionKOH, solid (100%) 1.15 gButadiene 1650.00 g______________________________________
The mixture is heated to 65.degree. C. and polymerized for 32 hours until pressure drops down.
Approx. 4000 g of a coagulate-free 39-40% polybutadiene latex are obtained. The latex can be freed from residual monomers without foaming by distilling off approximately 10% of the water in the latex and replacing it with deionized water rendered alkaline with KOH to pH 9.
Ultracentrifuge particular size analysis of the latex showed the following particle diameter distribution:
______________________________________D0 90 DAN 166.4D10 132 DAL 177.1D20 192 DAF 185.3D30 196 DAV 191.1D40 197 DVN 176.1D50 198D60 198D70 199D80 201 DAV/DAN = 1.15D90 208D100 224______________________________________
EXAMPLE 51
According to the Invention
Production of a Polybutadiene Latex, Average Particle Diameter DAV 250 nm, by the Continuous Addition Process
The following materials are introduced into a 40 liter stainless steel autoclave (operating pressure up to 25 bar) equipped with an infinitely variable paddle stirrer (120 r.p.m.) and internal temperature control:
______________________________________Deionized water 15350.00 gPotassium hydroxide, solid 87.50 gEmulsifier resin of formula 1, Table I 332.50 g(finely powdered)______________________________________
The pH value of the clear aqueous solution is approximately 11.5.
After repeated evacuation and purging with nitrogen, the autoclave is re-evacuated and a mixture of
______________________________________butadiene 2900.00 gtert.-dodecyl mercaptan 9.00 g______________________________________
is subsequently introduced. The mixture is heated with stirring to 65.degree. C., after which polymerization is initiated by the introduction under pressure of a solution of
______________________________________potassium peroxodisulfate in water, 2.5% 1043.00 g______________________________________
After a solids content of 6-10% by weight has been reached, a mixture of
______________________________________butadiene 8250.00 gtert.-dodecyl mercaptan 26.00 g______________________________________
is uniformly introduced over a period of 55 h.
After addition of the butadiene, the mixture is stirred at elevated temperature (70.degree. C.) until the pressure has fallen to 4 bar.
The crude latex then has a solids content of approximately 39-40%.
The total polymerization time is approximately 75 hours.
The butadiene still present in the autoclave is largely removed by venting the reactor overhead at approximately 50.degree. C., followed by condensation, and the crude latex is subjected to steam distillation until no more butadiene and divinyl cyclohexene can be detected in the latex.
The demonomerized latex is freed from slight precipitations by filtration through 50 .mu. mesh sieves. It has an average latex particle diameter (DAV of 250 nm, as determined by the ultracentrifuge technique; the polymer has a swelling index of 25 and a gel content of 85%.
EXAMPLE 52
Polybutadiene latex, particle diameter 370 nm (According to the Invention
The following materials are introduced into a 6 liter stainless steel autoclave corresponding to Example 50:
______________________________________Deionized water 2524.0 gEmulsifier of formula 9 (Table I) 55.0 gdipotassium saltTert.-dodecyl mercaptan 5.7 g2.5% aqueous K.sub.2 S.sub.2 O.sub.8 solution 172.0 gKOH, solid (100%) 1.3 gButadiene 1832.0 g______________________________________
Polymerization is carried out for 100 hours at 65.degree. C., after which the temperature has fallen to around 6 bar. A 39% polybutadiene latex having an average particle diameter DAV of 376 nm is obtained.
______________________________________Results of ultracentrifuge analysis:______________________________________D0 339 DAN 371.2D10 353 DAL 372.1D20 358 DAF 373.5D30 361 DAV 375.7D40 364 DVN 372.3D50 367D60 370D70 373 DAV/DAN = 1.01D80 375D90 383D100 1000______________________________________
EXAMPLE 53
Production of a Polybutadiene Latex, Average Particle Diameter 350 nm (Seed Inflow Process) (According to the Invention)
The following are introduced in the absence of oxygen into a 40 liter stainless steel autoclave (operating pressure up to 25 bar) equipped with an infinitely variable paddle stirrer (120 r.p.m.) and internal temperature control:
______________________________________Deionzed water 8000.00 gPotassium chloride 30.00 gEmulsifier 1 (Table I), diacid powdered 15.50 gPotassium persulfate K.sub.2 S.sub.2 O.sub.8, solid 10.00 gCaustic potash KOH, solid (100%) 7.80 gPolybutadiene latex, particle diameter 507.00 g100 nm, 35% (Example 37)______________________________________
The autoclave is evacuated three times, the vacuum being eliminated with nitrogen. After re-evacuation,
______________________________________butadiene 3000.00 gn-dodecyl mercaptan 9.00 g______________________________________
are drawn into the vacuum from a supply vessel.
The mixture is then heated to 60.degree. C. After a latex solids content of 10% has been reached, the following monomer streams are added over a period of 70 hours:
______________________________________Activator-emulsifier inflow (clear solution)Deionized water 7113.00 gPotassium peroxodisulfate K.sub.2 S.sub.2 O.sub.8 30.00 gEmulsifier 1 (Table I) diacid 180.00 gCaustic potash, KOH, solid 8.90 gMonomer inflow (homogeneous solution)Butadiene 13000.00 gn-Dodecyl mercaptan 39.00 g______________________________________
At the beginning of the addition, the polymerization temperature is kept constant at 70.degree. C. After a polymerization time of approximately 90 hours, an approximately 50% polybutadiene latex has formed. There are no significant quantities of coagulate either in the autoclave or in the latex.
The latex can be demonomerized without foaming. The polymer has a gel content of approximately 75 to 80% and a swelling index of 25 to 30. The particle diameter distribution of the latex is very narrow and the mean particle diameters are approximately 350 nm, as can be seen from FIG. 1 (electron micrograph, contrasting with osmium tetroxide).
The latex, which can also be produced on an industrial scale in this way, is suitable as a graft base for ABS polymers and other high-impact thermoplastic molding compounds (cf. Example 57).
EXAMPLE 54
Seed inflow process of Example 53 with another emulsifier according to the invention.
The procedure is as in Example 53, except that the emulsifier described there is replaced by the same quantity in grams of an emulsifier having the idealized structure 7 in Table I in the form of the dipotassium salt.
After a polymerization time of approximately 100 hours, an approximately 50% polybutadiene latex has formed. Its particle size distribution was determined by the ultracentrifuge technique:
______________________________________D0 334 DAN 418.6D10 393 DAL 422.0D20 398 DAF 427.0D30 402 DAV 435.4D40 406 DVN 422.5D50 410 DAV/DAN = 1.04D60 415D70 422D80 432D90 490 DAV/DAN = 1.04D100 1000______________________________________
The polymer has a gel content of 70% and a swelling index of 30.
This latex is also eminently suitable as a graft base for the production of high-impact molding compounds.
EXAMPLE 55
Seed Inflow Polymerization Process Using an Emulsifier According to the Invention and a Redox Initiator System
The following are introduced into an autoclave corresponding to Example 53:
______________________________________Deionized water 8000.00Emulsifier of formula 1 in Table I, 15.50diacid, powderedPotassium hydroxide, solid, 100% 3.50 APolybutadiene latex, particle diameter 507.00100 nm (Example 37)Storage vessel I Butadiene 1500.00 Bn-Dodecyl mercaptan 9.00Storage vessel II Butadiene 1500.00 Cp-Menthane hydroperoxide, 50% 7.00Storage vessel IIIDeionized water 490.00Sodium formaldehyde sulfoxylate(Rongalit C .RTM.), solid 1.50 DFe(II))-ethylenediamine tetraacetic acid 5.00complex, 0.05 molar solution in waterStorage vessel IVDeionized water 6623.00Rongalit C .RTM., solid 4.50Emulsifier acid of formula 1, Table I 170.60 EKOH, solid 38.60Storage vessel V Butadiene 8654.00 Fn-Dodecyl mercaptan 39.00Storage vessel VI Butadiene 4347.00 Gp-Menthane hydroperoxide, 50% 29.80______________________________________
After mixture A has been introduced, the autoclave is repeatedly evacuated and the pressure equalized with nitrogen. After re-evacuation, mixtures B and C are drawn in.
The autoclave is heated to an internal temperature of 70.degree. C., after which D is added.
After a solids content in the crude latex of approximately 7 has been reached, streams E, F and G are introduced into the reactor over periods of 70 hours, 55 hours and 60 hours, respectively.
After a polymerization time of 100 hours, the polymerization reaction is terminated, the crude latex is vented and demonomerized.
The latex particle diameter distribution of the coagulate-free, demonomerized latex appears as follows:
______________________________________D0 219 DAN 389D10 374 DAL 391D20 378 DAF 393D30 382 DAV 395D40 386 DVN 391D50 389D60 393D70 397D80 402 DAV/DAN 1.015D90 412D100 1100______________________________________
The latex is eminently suitable as a graft base for the production of ABS polymers and other high-impact thermoplastics and shows further improved thermal stability compared with persulfate activation.
EXAMPLE 56
Comparison
The procedure is as in Example 53 except that, instead of the emulsifier according to the invention, the same quantity (in g) of DRESINATE.RTM.731 is used.
After a polymerization time of approximately 80 hours, the pressure has fallen to around 3.5 bar and a latex having the following particle size distribution has formed:
______________________________________D0 117.5 DAN 170.5D10 144 DAL 179.2D20 156 DAF 190.2D30 165 DAV 203.2D40 174 DVN 179.8D50 183D60 196D70 233D80 268 DAV/DAN = 1.19D90 285D100 326______________________________________
The latex has a gel content of approximately 95% and a swelling index of approximately 20. The latex is unsuitable as a graft base for the production of ABS polymers because the strength values of ABS moldings produced therewith are inadequate.
FIG. 2 shows the evolution of the average latex particle diameter as a function of time on the basis of quasicontinuous measurements. Starting from the same seed latex, the particle size develops differently where the emulsifier according to the invention is used than where Dresinate is used.
The measurements were performed by laser correlation spectroscopy. The latex particle diameter determined by laser correlation spectroscopy is larger by a factor of 1.2 than the particle diameter determined by electron microscopy or by the ultracentrifuge technique.
Particulars of the on-line measurement of latex particles can be found, for example, in DE-OS 3 303 337.
EXAMPLE 57
According to the Invention
Graft Polymerization of a Styrene/Acrylonitrile Mixture onto the Polybutadiene Latex of Example 53
50 Parts by weight polybutadiene (in the form of a latex having a solids content of 25% by weight prepared by dilution of the polybutadiene latex of Example 53 with deionized water) are heated under nitrogen to 63.degree. C., followed by the addition of 0.5 part by weight K.sub.2 S.sub.2 O.sub.8 (dissolved in 15 parts by weight water). A mixture of 36 parts by weight styrene and 14 parts by weight acrylonitrile and also 1.5 parts by weight of the sodium salt of disproportionated abietic acid (dissolved in 25 parts by weight water)) is then introduced over a period of 4 hours during which the grafting reaction takes place. Following an after-reaction time, the latex is coagulated in a magnesium sulfate/acetic acid solution and the resulting powder is dried in vacuo at 70.degree. C.
EXAMPLE 58
According to the Invention
Testing of a mixture of the graft polymer described in Example 57 with a styrene/acrylonitrile copolymer and an .alpha.-methyl styrene/acrylonitrile copolymer.
The graft polymer described in Example 57 was mixed in an internal kneader with a styrene/acrylonitrile copolymer (72:28, M.sub.w approx. 115,000, M.sub.w M.sub.n -1.ltoreq.2) or with an .alpha.-methyl styrene/acrylonitrile copolymer (72:28, M.sub.w approx. 75,000, M.sub.w /M.sub.n -1.ltoreq.1) in the ratios by weight shown in Table IX. 2 Parts by weight pentaerythritol tetrastearate and 0.1 part by weight of a silicone oil (based in each case on 100 parts by weight graft polymer+copolymer) were used as additives. After processing by injection molding, impact strength (DIN 53 453), hardness (DIN 53 456), Vicat B softening point (DIN 53 460), MVI (DIN 53 735u) and also natural color (after processing at 240.degree. C. to 280.degree. C.) and surface gloss (according to DE-AS 2 420 358) were determined, the results being shown in Table IX.
TABLE IX__________________________________________________________________________Testing of the graft rubber described in Example 57 .alpha.-methyl Styrene/ styrene/Graft poly- acryloni- acryloni-mer of Exam- trile copolymer trile copolymer RT -40.degree. C. Vicat MVIple 57 [parts [parts by [parts by a.sub.k a.sub.k Hc B [cm.sup.3 / Gloss Natural colorby weight] weight] weight] [kJ/m.sup.2 ] [kJ/m.sup.2 ] [n/mm.sup.2 ] [.degree.C.] 10 mins.] 240.degree. C. 260.degree. 280.degree.__________________________________________________________________________ C.30 70 -- 15.3 9.4 103 102 8.0 F-G -- -- --40 60 -- 16.8 12.3 84 100 5.9 F light light light50 50 -- 17.2 14.6 67 96 4.1 F -- -- --20 -- 80 10.4 5.5 113 115 2.0 F -- -- --30 -- 70 13.9 7.6 93 113 1.6 F -- -- --40 -- 60 16.7 10.3 77 109 1.2 E-F light light yellowish__________________________________________________________________________
EXAMPLES 59
According to the Invention
Graft Polymerization of a Styrene/Acrylonitrile Mixture onto the Polybutadiene latex of Example 53
The procedure was as described in Example 57 except that, instead of the sodium salt of disproportionated abietic acid, 1.5 parts by weight of compound 1 in Table I in the form of the dipotassium salt was used as emulsifier in the graft reaction.
EXAMPLE 60
According to the Invention
Testing of a Mixture of the Graft Polymer Described in Example 59 with a Styrene/Acrylonitrile Copolymer and an .alpha.-Methyl Styrene/Acrylonitrile Copolymer
The resin components described in Example 58 were used and the results are shown in Table X.
TABLE X__________________________________________________________________________Testing of the graft rubber described in Example 59 .alpha.-methyl Styrene/ styrene/Graft poly- acryloni- acryloni-mer of Exam- trile copolymer trile copolymer RT -40.degree. C. Vicat MVIple 59 [parts [parts by [parts by a.sub.k a.sub.k Hc B [cm.sup.3 / Gloss Natural colorby weight] weight] weight] [kJ/m.sup.2 ] [kJ/m.sup.2 ] [n/mm.sup.2 ] [.degree.C.] 10 mins.] 240.degree. C. 260.degree. 280.degree.__________________________________________________________________________ C.30 70 -- 16.1 9.3 103 103 8.2 F-G -- -- --40 60 -- 17.1 13.0 85 101 5.8 F very very light light light50 50 -- 17.6 14.0 67 95 4.0 F -- -- --20 -- 80 10.5 6.3 114 115 2.2 F -- -- --30 -- 70 13.5 8.1 95 113 1.7 F -- -- --40 -- 60 16.9 10.0 76 108 1.2 E-F very very light light light__________________________________________________________________________
EXAMPLE 61
According to the Invention
Graft Polymerization of a Styrene/Acrylonitrile Mixture onto the Polybutadiene Latex of Example 56
50 Parts by weight polybutadiene (in the form of a latex having a solids content of 25% by weight prepared by dilution of the polybutadiene latex of Example 56 with deionized water) are heated under nitrogen to 63.degree. C., followed by the addition of 0.5 part by weight K.sub.2 S.sub.2 O.sub.8 (dissolved in 15 parts by weight water). A mixture of 36 parts by weight styrene and 14 parts by weight acrylonitrile and also 2 parts by weight of compound 1 in Table I in the form of the dipotassium salt (dissolved in 25 parts by weight water) is then added over a period of 4 hours during which the graft reaction takes place. Following an after-reaction time, the latex is coagulated in a magnesium sulfate/acetic acid solution and the resulting powder is dried in vacuo at 760.degree. C.
EXAMPLE 62
According to the Invention
Testing of a Mixture of the Graft Polymer Described in Example 61 with a Styrene/Acrylonitrile Copolymer and an .alpha.-Methyl Styrene/Acrylonitrile Copolymer
The components described in Example 58 were used in the quantities shown in Table XI which also shows the natural colors after processing at 240.degree. C. to 280.degree. C.
TABLE XI__________________________________________________________________________Testing of the graft rubber described in Example 61Graft polymer Styrene/acrylo- .alpha.-methyl styrene/of Example 61 trile copolymer acrylonitrile copolymer Natural color[parts by weight] [parts by weight] [parts by weight] 240.degree. C. 260.degree. C. 280.degree. C.__________________________________________________________________________40 60 -- light light light30 -- 70 light light yellowish__________________________________________________________________________
EXAMPLE 63
Comparison
Graft Polymerization of a Styrene/Acrylonitrile Mixture onto the Polybutadiene Latex of Example 56
The procedure is as described in Example 1 except that, instead of the dipotassium salt of compound 1 in Table I, 2 parts by weight of the sodium salt of disproportionated abietic acid were used as emulsifier in the graft reaction.
EXAMPLE 64
Comparison
Testing of a mixture of the graft polymer described in Example 63 with a Styrene/Acrylonitrile Copolymer and an .alpha.-Methyl Styrene/Acrylonitrile Copolymer
The components described in Example 58 were used in the quantities shown in Table XII which also shows the natural colors after processing at temperatures of 240.degree. C. to 280.degree. C.
TABLE XII__________________________________________________________________________Testing of the graft rubber described in Example 63Graft polymer Styrene/acrylo- .alpha.-methyl styrene/of Example 63 trile copolymer acrylonitrile copolymer Natural color[parts by weight] [parts by weight] [parts by weight] 240.degree. C. 260.degree. C. 280.degree. C.__________________________________________________________________________40 60 -- light light yellowish30 -- 70 light yellow- yellow ish__________________________________________________________________________

Emulsifiers and a process for the production of large particle size, homodisperse polymer dispersions using these emulsifiers

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