DE1060600B - Process for the production of aqueous polyvinyl ester dispersions - Google Patents

Description

The production of coarsely dispersed polyvinyl ester dispersions in the presence of a polyvinyl alcohol aqueous liquor is known from the patent 727 955 (IG. Farben). These dispersions have a good one Pigment compatibility and good frost stability. On the other hand, it has the disadvantage that the wet wiping resistance is not very good of the paints made from them. Only after a certain amount of aging do the films show properties which also meet higher demands. Another disadvantage of these dispersions is ίο stands in a certain hardness of the films made from them, which is presumably in the incorporation of Polyvinyl alcohol in the polymer chain has its cause.

The production of finely divided poly vinyl ester dispersions from patent 744318 is also known Combination of soap-like emulsifiers with sodium vinyl sulfate as a stabilizer. From these Dispersions give films with excellent gloss and very good wet wiping resistance. These After the addition of plasticizer, films also have greater flexibility than those obtained from the latices mentioned above. However, in comparison to the coarsely dispersed polyvinyl acetate dispersions, the finely dispersed polyvinyl acetate dispersions show a significantly poorer frost stability. Furthermore, because of their high degree of dispersity, they are poor pigment compatible. When pigment pastes are added, especially with higher pigmentation, coagulation phenomena occur easily that make the paint unusable. Furthermore, that of the soap emulsifier is in the The strong tendency to foam resulting from the liquor is very disruptive to processing. Both of these Dispersion types have the common disadvantage that the auxiliaries required for their production are in one In the case of polyvinyl alcohol, in the other case a soap emulsifier, in the formation of the dispersion film act as a foreign body.

It has now been found that the polymerization of vinyl esters or copolymerization with vinyl esters in water in the presence of a combination of compounds, eg. B. a condensation product of polypropylene oxide and ethylene oxide, which are compatible with both polyvinyl esters or vinyl ester-containing copolymers, act for them as plasticizers and are weak emulsifiers, with water-soluble salts of vinyl sulfonic acid, eg. B. sodium vinyl sulfonic acid, dispersions are obtained with greatly improved properties. Weak emulsifiers should be understood to mean those which, in an aqueous solution of about 1V, only lower the surface tension to a value between 33 and 45 dynes / cm, while normal soaps and good emulsifiers reduce the surface tension to a value of around 30 dynes / cm
of aqueous polyvinyl ester dispersions

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning,

Frankfurt / M., Brüningstr. 45

Dr. Werner Starck, Hofheim (Taunus),

Dr. Karl-Heinz Kahrs, Frankfurt / M.,

and Dr. Anton Staller, Frankfurt / M.-Unterliederbach,

have been named as inventors

occasionally lower between 25 and 30 dynes / cm - all values measured at 20 ° C.

The size of the latex particles produced is proportional to the surface tension of the polymerization liquor, provided that the emulsifier used has a sufficiently high cloud point in the aqueous Owns liquor, which naturally at least in the vicinity of the polymerization temperature, preferably higher, must lie.

Commonly used acetyl-containing polyvinyl alcohols lower the surface tension of the water at 20 ° C from 72 dynes / cm for pure water to about 45 dynes / cm in 1% aqueous solution. The thus obtained Accordingly, latices are coarsely dispersed.

Usual soap emulsifiers reduce by 10% aqueous solution at 20 ° C, the surface tension to 30 dyn / cm, occasionally to values between 25 and 30 dynes / cm.

Since very finely divided latices are obtained in the presence of soap emulsifiers, it is understandable that one should the use of less surface-active emulsifiers leads to somewhat coarser dispersions.

The latex particle size largely influences the properties of the dispersions such as frost stability, Pigment binding capacity. So is about setting the surface tension of the polymerization liquor steering of the desired properties is possible.

The dispersions produced according to the invention are still finely dispersed and have their dispersion films " still have an excellent gloss, but in addition their frost stability is improved to -— 18 ° C, while-

909 559/472

Finely dispersed latexes produced with soap emulsifiers only down to - 5 ° C, in exceptional cases up to - 10 ° C are frost-resistant.

While those produced according to patent 744 318 with soap emulsifiers and sodium vinyl sulfonic acid Highly foaming dispersions and the colors obtained from them and thus significant processing problems occur, which can often only be eliminated by adding antifoam agents, are shown by the new ones Dispersions practically no foam.

Furthermore, the pigment binding capacity is lower than that of products made with soap emulsifiers very much increased, even with high pigment volume concentration occur in contrast to the usual finely dispersed polyvinyl ester dispersions show no signs of coagulation.

Compared to the coarsely dispersed polyvinyl ester dispersions, the new dispersions have the following advantages: The films made from them are far better wet smudge resistance, but also far more flexible, which is special is of great importance for paints that are under tension. By using a Emulsifier or a protective colloid, which with the binder, z. B. polyvinyl acetate, is compatible and Moreover, it acts as a plasticizer, eliminating the difficulties involved in forming the dispersion film when the latex particles converge due to the interfering liquor fractions, polyvinyl alcohol or soap emulsifier occur. From stability

ίο it is also useful for weak emulsifiers to be combined with sodium vinyl sulfate. The sodium vinyl sulfonic acid is incorporated into the polymer chain built-in.

The dispersions prepared according to the invention thus have the advantage of being frost-resistant, although they are finely dispersed, have a high pigment binding capacity and none during processing Show a tendency to foam. The technical advantages of the new dispersions are summarized in the following table:

Tuesday
spersion Emulsifier surfaces
tension
(20 ° C) dynes / cm
in 10%
aqueous solution Frost resistant
the ability of the disper
sion 24 hours
at Pigment binding capacity Elongation at break
of the dispersion
films from the with
25% dibutyl
added phthalate
Dispersion A.
B. AIk ₇ I- (C ₁₂ -C ₁₆ ) -
benzenesulfonic acid
sodium
Condensation product
made of polypropylene
oxide with ethylene
oxide
Molecular weight 4500
OH number 25 30th
37 -5 ° C
-18 ° C When adding a water
pigment paste (ζ. Β.
of iron oxide red) occurs without
Pigmentation aid in
Weight ratio of ^; l part
Dispersion with 2 parts of Pig
ment coagulation
1 part of dispersion can be used
without further ado with 2 parts
Add pigment (as a paste)
without the help of Pig
mentation aids. It kicks
no coagulation whatsoever
appearance on. 2000 to 2200%
3500 to over
4000%

Emulsifiers which can be used for the process according to the invention should, in addition to one compared to conventional Soap emulsifiers with lower surface activity have good compatibility with polyvinyl esters possess and have a good softening effect. Leave the latter two necessary properties very easily by fusing the emulsifiers with z. B. solid polyvinyl acetate in the heat and check the subsequent testing of the mixture.

The necessary conditions meet z. B. certain nonionic emulsifier types where the hydrophobic and hydrophilic residues are matched to one another in such a way that the surface tension is less than or equal to their aqueous solutions compared to that of pure water is only moderately lowered, namely to one Value between 33 and 45 dynes / cm. This is e.g. B. is the case with a number of connections through Condensation of polypropylene oxide with such an amount of ethylene oxide are made that you Cloud point in the water is still relatively z. B. is over 50 ° C high. The molecular weight of these condensation products should generally be in the range from 3,000 to 15,000, preferably in a range from 4,000 to 10,000. It is advisable to use such "weak emulsifiers" together with the in the Chain polymerized vinylsulfonate to use sodium, as this stabilizes the resulting Dispersion is made.

Since the above-mentioned emulsifiers are soluble in monomeric vinyl esters, they can also be used continuously are introduced with the monomers.

The usual peroxidic substances are used as catalysts in the process according to the invention Use such as hydrogen peroxide, potassium and ammonium persulphate, sodium perborate, potassium perborate, Sodium peroxide, potassium peroxide, urea peroxide etc. One can also use redox activation z. B. with potassium persulfate as an oxidizing agent and sodium bisulfite as a reducing agent or a combination of hydrogen peroxide and cobalt salts. The amount of catalyst can be from 0.01 to 10%, calculated on the monomer. Quantities of 0.05 to 0.5% are preferred based on the monomer. The emulsifiers are dissolved in water or, if they are monomer-soluble, partly dissolved in water, partly dissolved in the monomer. They are used in amounts of 1 to 10%, predominantly from 3 to 7%, based on the monomer.

The polymerization is usually carried out in such a way that the emulsifiers are dissolved in water, that catalyst and monomeric vinyl ester is added to the liquor in small amounts and

is heated until the polymerization has started, this is the case at 67 to 70 ° C. Then one lets running in further monomer continuously. After the feed has ended, the internal temperature is reached as a result Depletion of monomers is a maximum. It is then cooled down.

The polymerization can be carried out below 0 ° C with the addition of anti-freeze agents. It can also be polymerized at temperatures above 100 ° C., if necessary with the application of pressure. In general, however, polymerization temperatures between 65 to 85 ° C are preferred.

It may be advantageous to carry out the polymerization in the absence of oxygen, e.g. B. to perform under nitrogen. A p _ff value of about 3 to about 7 is usually used.

According to the invention, both polyvinyl ester dispersions can be used as well as dispersions of copolymers which incorporate at least one vinyl ester contain, manufacture. Examples of vinyl esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate mentioned. Copolymers can be produced from the labeled vinyl esters with each other or with z. B. acrylic esters, such as acrylic acid ethyl ester, Acrylic acid butyl ester, or with maleic acid, fumaric acid, itaconic acid ester, vinyl chloride etc.

example 1

In a three-necked flask made of glass with a reflux cooler, perforated blade stirrer (160 rev./min.), Two dropping funnels, a polymerization liquor is filled, consisting of
100 parts by weight of water,

5 parts by weight of a condensation product of polypropylene oxide and ethylene oxide with a OH number of 25, a molecular weight of 4500. The product lowers the surface tension of the water in 1% solution from 72 dynes / cm to 27 dynes / cm (20 ° C). The condensation product is with polyvinyl acetate, e.g. B. from K value 40, well tolerated, and from the melt of this mixture a clear, very flexible film can be produced.

1 part by weight of sodium vinyl sulfonate.
Formic acid is used to _{adjust to a p ff} value of 3.0.

The polymerization liquor is heated to 80 ° C. Then a catalyst solution consisting of 0.3 parts by weight of potassium persulfate in little Dissolved water, and added 5 parts by weight of vinyl acetate. The internal temperature drops for a short time about 70 ° C. External heating ensures that the internal temperature of 80 ° C is soon reached again is and then leaves 95 parts by weight of vinyl acetate while maintaining a polymerization temperature from 80 ° C to run in about 3 hours.

After the end of the monomer addition, the batch reaches 10 minutes as a result of a depletion of monomers a temperature peak of about 85%. The batch is then left with slowed stirring cooling down.

A polyvinyl acetate dispersion with a milk-like appearance and very low latex viscosity is obtained (about 2OcP - measured in the Hoeppler viscometer). The solids content is about 50%. The K value, measured in a mixture of methanol-water (85 to 15 parts by volume), is approximately 38 units. The residual monomer content is far less than 1%.

The dispersion is frost-resistant down to -18 ° C, i. H. after freezing at -18 ° C (24 hours) and thawing are the properties of the dispersion unchanged.

If the emulsifier used in the above formulation is replaced by a more effective, soap-like type, e.g. B. by alkyl (C ₁₂ -C ₁₆ ) -benzenesulfonate sodium or a paraffinsulfosaures sodium, whereby the surface tension of the water is lowered to a value of about 30 dynes / cm, one obtains a dispersion with much finer particles, which only Resistant to frost down to -5 ° C, but coagulates at -18 ° C.

If the dispersion according to the invention is added in the absence of pigmentation auxiliaries with a pigment paste containing, inter alia, iron oxide red, e.g. B. in a ratio of 2 parts of pigment to 1 part of dispersion, no coagulation phenomena occur, while dispersions with more effective emulsifiers such. B. alkyl- (C ₁₂ -C ₁₆ ) -benzenesulfonate sodium, paraffin sulfonate sodium with a chain length of 12 to 16 carbon atoms, were prepared, coagulate immediately.

If the dispersion prepared according to the present invention is mixed with 25% dibutyl phthalate and a film is cast and the elongation at break is determined on it, values are obtained which are between 3400 and more than 4000%. However, if you have the dispersion with more surface-active emulsifiers prepared of the type mentioned above, dispersions are obtained to which 25% dibutyl phthalate is added, provide a film with elongations at break of only 2000 to 2200%. The dispersion produced according to the invention so results after the addition of plasticizer much more flexible films than those with stronger Surface-active emulsifiers were obtained.

There is also a very important advantage of the new dispersion prepared according to the example in that they lather much less than those made with more surfactant emulsifiers became.

Example 2

A polymerisation liquor consisting of:
100 parts by weight of water,

5 parts by weight of a condensation product of polypropylene oxide and ethylene oxide with a OH number of 25, a molecular weight of 4500. The product lowers the surface tension of the water in 1% solution from 72 dyn / cm to 37 dyn / cm (20 ° C). The condensation product is well compatible with block polyvinyl acetate of K value 40 when fused, and the mixture gives a very flexible, smooth, crystal-clear film.

1 part by weight of sodium vinyl sulfate.
Formic acid is used to _{adjust to a p w} value of 3.0. It is heated to 80 ° C. and a catalyst solution consisting of 0.3 parts by weight of potassium persulfate, dissolved in a little water, is added.

Then 5 parts by weight of a monomer mixture consisting of 30% maleic acid dibutyl ester and 70% vinyl acetate, added. The temperature drops to about 75 ° C for a short time If you choose the external heating, the internal temperature of 80 ° C will soon be reached again, and within 95 parts by weight of a mixture of 5 hours

Claims (1)

7 8 Mixture of 3O% dibutyl maleic acid and 70% by weight potassium persulfate in a little water and 5 parts by weight of monomeric vinyl propionate are added to vinyl acetate while maintaining an internal temperature. the ron 80 ° C added. After the end of the internal temperature drops rapidly to about 75 ° C. By When the internal temperature rises to monomers, the external heating is brought back to 80 ° C. ; A temperature peak of 87 ° C. It is then heated 5 parts by weight of vinyl propionate are then added shortly after and leaves the approach with slow maintenance of an internal temperature of 80 to 82 ° C leadership get cold. added over the course of an hour. After loading A copolymer dispersion is obtained with the end of the addition of monomer, the internal The following data: temperature to over 90 ° C. Then slowly Solid about 49% io, stirred cold. Monomer residue below 1% A polyvinyl propionate dispersion is obtained with Latex viscosity about 40 cP with a dry content of about 51% and a residual The advantages of the dispersion are its monomer content of less than 1%. low foaming, an extraordinarily good. The elongation at break of the film is a value ³ igment binding capacity, very good wet wiping of about 4000%, much higher than when used strength and good flexibility of the dispersion film, soap-like emulsifiers, with elongation at break For the elongation at break values of over 2000%, values of around 2500% are measured on the film, The dispersions are frost-resistant down to -18 ° C : eptur, but with the choice of an emulsifier with and very good pigment compatibility. > Better surface activity only values of about ao -p .100 to 1200% receives, even if you have the share of j / ai-ext claims: to maleic acid dibutyl ester to 37%. 1. Process for the preparation of aqueous The dispersion obtained is also stable to low temperatures. ) is -18 ° C holding copolymer dispersions, thereby Example 3 ^a5 characterized in that the polymerization in Presence of salts of vinyl sulfonic acid and In a three-necked glass flask with reflux of emulsifiers in 1% aqueous solution : ühler, two dropping funnels and a perforated blade stirrer at 20 ° C, one in the range from 33 to 45 dynes / cm Agitation: 160 rev / min.) Will have a polymeriza- lying surface tension and the Ionic liquor filled, consisting of 30 containing polyvinyl esters or vinyl esters 00 parts by weight of water, copolymers are both well tolerated 5 parts by weight of a condensation product from as well as a plasticizer for these polymers Polypropylene oxide and ethylene oxide work together. Molecular weight of about 4500, an OH number 2. Process according to Claim 1, characterized by about 25, which draws 35 in 1% aqueous solution, that as emulsifiers, condensation surface tension of the water from 72 dyn / cm lowers products made of polypropylene oxide and ethylene oxide to 37 dyn / cm (measured at 20 ° C). That will be used. Condensation product is with block polyvinyl 3. The method according to claim 1 and 2, characterized acetate well tolerated when fused, and characterized that, as emulsifiers, condensers the mixture gives a very soft, pliable, 40 cationic product made of polypropylene oxide and ethylene crystal clear film. oxide, which has a molecular weight of 4000 to 1 part by weight of sodium vinyl sulfate, 10,000 and a cloud point above 50 ° C 0.6 parts by weight sodium acetate, anhydrous. sit, be used. With glacial acetic acid value is overall of 5.7 on a p _H Splits. Then set an internal temperature of 45. Considered publications: 0 ⁰ C, gives a catalyst solution from 0.3 Ge German Patent Nos. 727 955, 744 318. © 909 559/472 6.59