DE2752102C2 - Process for the preparation of dispersions by emulsion polymerization of vinyl esters - Google Patents

Description

a) 10 to 70% by weight of the total monomers,

b) a large excess, based on the stoichiometric amount, of a reduction system composed of sodium formaldehyde sulfoxylate and Water, an acetate and / or sulfate of an element of group VIII of the periodic table,

c) a common protective colloid,

d) a conventional capillary active agent as well

e) a conventional chain transfer agent with an aldehyde function,

an aqueous oxidation mixture of water-soluble peroxides and a bicarbonate and / or Acetate of an alkali metal or an alkaline earth metal gradually feeds and

in the second stage at constant temperature not below 6O ⁰ C further oxidation mixture and the remaining monomer content is continuously added

2. The method according to claim 1, characterized in that one cobalt acetate and / or sulfate begins.

3. The method according to claim I, characterized in that the oxidation mixture is hydrogen peroxide in the presence of bicarbonates and / or acetates of sodium or potassium are used,

45

The invention relates to a process for the preparation of vinyl ester dispersions to which, if appropriate, certain unsaturated carboxylic acid esters have been added, see above which are used in the adhesives industry. These dispersions have compared to emulsions from the State of the art outstanding properties.

It is known that the polymerization of vinyl acetate alone or together with other monomers selected from vinyl monomers and / or alkyl, aryl or cycloalkyl esters of unsaturated mono- or dicarboxylic acids having 3 to 15 carbon atoms, usually at a temperature of 65 to 70 ⁰ C. , which corresponds to the boiling point of the monomer to perform.

Such a temperature is initially obtained by heating the jacket with steam; higher temperatures can be obtained by the polymerization approach with a slight over- t> 5 printing.

Short reaction cycles are thus obtained, but the products are of poor quality, especially those intended for use in the adhesives industry.

It has now surprisingly been found that it is possible taking the disadvantages of the prior art Achieving high quality products overcome by going at lower temperatures within polymerizes in considerably shorter times and without initial heating of the reactants.

The inventive method for the preparation of dispersions by emulsion polymerization of Vinyl esters, which optionally butyl maleate, ethylhexyl maleate or alkyl acrylates with less than 12 carbon atoms in the alkyl radical are added, in an aqueous medium, in the presence of a water-soluble redox catalyst and a buffer system, as well optionally plasticizers and other customary additives is characterized in that one the polymerization is carried out in two stages, wherein one

in the first stage at 25 to 65 ° C of the mixture provided, consisting of

a) 10 to 70% by weight of the total monomers,

b) a large excess, based on the stoichiometric amount, of a reduction system from sodium formaldehyde sulfoxylate and water, an acetate and / or sulfate of an element of VIII. Group of the periodic table,

c) a common protective colloid,

d) a conventional capillary active agent as well

e) a conventional chain transfer agent with an aldehyde function,

an aqueous oxidation mixture of water-soluble peroxides and a bicarbonate and / or acetate Alkali metal or an alkaline earth metal gradually supplies and

in the second stage at constant temperature not below 60 ° C further oxidation mixture and the the remaining monomer content is continuously added.

This sequence of operations gives rise to the formation of two types of particles, the first in one lower temperature in the range of 25-65 ° C high protective colloid content and with a considerably broader distribution of the particle diameter, the second at a higher temperature, this temperature however being constant, with a distribution of Particles within a narrower range.

Such a heterogeneous character of the particles is particularly noticeable in the manufacture of adhesives, during the arrangement of the pieces to be joined by gluing a certain proportion of the Polymer particles must migrate to the interior of the porous support component, while the other Particles remain bound to the outer surface, thereby reducing the adhesive effect of the polymer is promoted.

Another advantageous feature of the process according to the invention is that dispersions with a high viscosity value and with what is indeed an extraordinary constancy of the viscosity regardless the dilution receives.

This latter is one of the most interesting preconditions in the field of dispersions for adhesives and for dispersants Water-based can be used, along with the rheological properties and resistance against shear stresses, which are also due to

25th

are at a high level.

It is also of interest to note that through appropriately varying the proportions of the monomer in the feed and in the feed stream Emulsions with different degrees of polymer dispersibility and thus different viscosity levels can be obtained while still maintaining the best technological properties and high levels of performance.

It was also surprisingly found that in Using the process according to the invention, a considerable reduction in the pollution of the reactor is achieved at the same time. It finds one Removal of possible traces of encrustation or a deposit by simply washing with water Extraordinary advantages attainable at low pressure instead of other are the increase in the efficiency of the Polymerization process which can be quantified in the order of 40-50%.

As stated above, the process according to the invention can be applied to the production of dispersions, starting from vinyl esters are used. Vinyl acetate has been named as a typical vinyl ester as it is is that which is currently used in larger quantities.

Other vinyl esters worth mentioning are: vinyl propionate vinyl laurate; particularly satisfactory results are obtained when using the vinyl esters Butyl maleate, ethylhexyl maleate or alkyl acrylates, in which the number of carbon atoms of the alkyl radicals lower than 12 is to be added.

From US-PS 29 98 400 it is already known polyvinyl acetate emulsions (not a dispersion) that free of flakes and coagulum, using a modifying ingredient, namely one

Methyl vinyl ether / maleic acid hydride copolymers, to manufacture. The aim of the process according to this US-PS is to obtain an emulsion which is free from Flakes is. According to the invention, however, this goal is not sought, rather that of the invention Process for the preparation of polyvinyl ester dispersions directed primarily in the field of Adhesives should + be used and therefore should have a high binding force, whereby the Manufacturing process of such dispersions with high binding force and short reaction times favorable energetic conditions and carried out without the use of expensive components will.

The following examples illustrate the invention. The parts given are parts by weight.

In Examples 2, 3 and 6 to 9 were in the first 50% of the oxidation mixture added to each stage; in Example 4 was that added in the first stage Amount of oxidation mixture 33.3%. In Example 5, the percentage of the oxidation mixture added was not measured; the additional speed was only gradually decreased depending on the thermal requirements of the reaction

The viscosities were determined at 20 ⁰ C using a Brookfield Viscometer (HAT) at 20 rpm.

The freeze-thaw cycles were followed by loading the dispersion is determined in a thermostat with usually five runs from -20 to + 20 ° C. Everyone The cycle lasts 12 hours, at the end of each cycle the viscosity of the dispersion was measured.

The mechanical strength resulted from the

35

60

65 Decrease in viscosity with too rapid stirring, in which Effects of shear forces, torsional forces, lamination tests and pumping tests. the Dispersion was made vigorously using a turbo stirrer of 1500 OpM, and after 24 hours the residual viscosity was determined.

"Removed encrustations" are to be understood as the encrustation of the reactor, which then follows the Procedures were eliminated.

The term "storage period" is to be understood as meaning the "storage stability"; To determine this, the dispersions were ^{kept in an oven at 50 °} C. for 30 days, and the initial and final viscosities were compared.

example 1 Comparative manufacturing

A 161 polymerization reactor was charged made of stainless steel equipped with a stirrer and a reflux condenser, with the following Formulation based on 100 parts of the monomer:

45

50

Vinyl acetate 100 parts water 95 pieces partially saponified Polyvinyl alcohol (alkaline alcoholysis) 134 pieces Sodium dodecy benzene sulfonate 04 parts Hydrogen peroxide (35%) 035 parts

It performs all of the ingredients together with 20 parts of vinyl acetate to, heated to 68 ⁰ C and resulting from the polymerization by adding the remaining vinyl acetate h during 4 supplies at a reaction temperature of 68-7O ⁰ C

Analysis results solid components 504% Vinyl acetate 100 parts viscosity 20 500 mPas water 95 pieces pH 4.4 partially saponified sediment 180 mg / kg Polyvinyl alcohol mechanical stability sufficient (alkaline alcoholysis) 7.5 parts removed incrustations 520 g Sodium formaldehyde Viscosity after dilution sulfoxylate 0.35 parts (25 parts water) 500 mPas Resistance to Freeze-thaw cycles small amount resistance versus mechanical Stress small amount Storage time sufficient Particle size 7%, approx. 500 nm 75%, approx. 3000 nm 18%, about 1000nm a few Lump Example 2

Propionaldehyde 0.14 parts Cobalt acetate 0.003 parts

35% hydrogen peroxide 03 parts Sodium bicarbonate 0.14 parts

At the beginning, water, the polyvinyl alcohol, which has previously been dissolved in water, the sodium formaldehyde sulfoxylate, the propionalnehyde, the cobalt acetate and 40 parts of vinyl acetate are added. Then you start with adding hydrogen peroxide and bicarbonate in portions.

After 50% of the oxidation system has been added, the remaining vinyl acetate is started to be fed in at 55 ° C. By the simultaneous addition of the oxidizing system, the temperature rises to 75-80 ⁰ C. During the two-hour supply of the vinyl acetate, the reaction temperature is kept below 80 ^° C.

Example 4 Analysis results

solid components

viscosity

sediment

mechanical stability

Incrustations Viscosity after dilution

(25 parts water)

Resistance to Freeze-thaw cycles: Resistance to

a mechanical one

Stress viscosity Storage time viscosity Particle size

50.7%

37,000 mPa

4.5

100 mg / kg

very good

20 g

6500 mPa ■ s very good

very good

unchanged

very good

unchanged

40%, approx. 500 nm

60%,

less than 500 nm

no lumps

20th

JO

35

Example 3 Vinyl acetate

water

Polyvinylpyrrolidone (K90) Sodium dodecylbenzene

sulfonate

Sodium formaldehyde

sulfoxylate

Cobalt acetate

35% hydrogen peroxide

Sodium bicarbonate

100 parts

95 pieces

7 parts

0.4 parts

0.15 part 0.0035 part 0.3 part 0.16 part

45

50

The procedure is that of Example 2, wherein the reaction temperature does not exceed 80 ⁰ C.

Analysis results

55

solid components

viscosity

sediment

mechanical stability

removed incrustations

Resistance to Freeze-thaw cycles Storage time Particle size

50.6%

17 00OmPas

4.45

40 mg / kg

very good

25 g

very good very good

60%, approx. 1000 nm 40%, approx. 500 nm no lumps

b0

Vinyl acetate

water

Methyl cellulose (400 cP) Sodium dodecylbenzene

salfonat

Nonylphenol polyglycol ether Propionaldehyde Cobalt acetate Sodium form aldehyde

sulfoxylate

Dibutyl phthalate

35% hydrogen peroxide

sodium

100 parts

90 pieces

3 parts

0.25 part 0.5 part 0.2 part 0.0025 part

0.18 parts 25 parts 0.35 parts 0.15 parts

It is charged with water, methyl cellulose, sodium dodecylbenzenesulfonate and the nonylphenol polyglycol ether, all of the ingredients in water beforehand have been dissolved, the propionaldehyde, sodium formaldehyde sulfoxylate and with 30% of the vinyl acetate Dibutyl phthalate.

Are then added portionwise hydrogen peroxide and sodium bicarbonate according to the progress of the reaction and charged with the remaining vinyl acetate and dibutyl phthalate, wherein the reaction temperature is maintained at about 60 ⁰ C.

Analysis results

solid components viscosity

sediment

mechanical stability

Resistance to Freeze-defrost cycles Abrasion resistance in

humid environment

Resistance to Saponifiers Storage time Particle size

removed incrustations

55.5%

13 50OmPa s

4.4

42 mg / kg

very good

very good . very good

Well

very good

60%, approx. 500 nm

40%,

less than 500 nm

no lumps

37 g

Example 5 Vinyl acetate 100 parts Dibutyl maleate 25 parts

Water 80 parts hydroxyethyl cellulose 3 parts

Nonylphenol polyglycol ether 2 parts sodium dodecylbenzenesulfonate 03 parts

Vinyl sulfonate 0.15 parts

N atrium formaldehyde sulfoxylate 0.6 parts

Crotonaldehyde 0.07 part Acetaldehyde 0.10 parts

35% hydrogen peroxide 0.55 parts

Methanol 10 parts sodium bicarbonate 0.25 part

All of the above ingredients are carried out with the exception of hydrogen peroxide and sodium bicarbonate, which are proportioned according to the thermal Progress of the reaction will be added, too.

27 52 102
8th solid components 56.3% Vinyl acetate 100 parts solid components ■ Vinyl acetate 53.5% 35% hydrogen peroxide i solid components 25th 49.9% I.
79,000 mPas S Vinyl acetate 100 parts introduced at the beginning -: ⁵ C. vi solid components 50.3% | i 230244/330 The polymerization takes place at a temperature of cobalt acetate viscosity 12 50OmPa ■ s water 87 pieces viscosity ο e ι s ρ ι e water 27,000 mPa s Sodium bicarbonate r
0.003 part I. ίο viscosity 4.5 f 30 water 95 pieces \ and 50 parts continuously thereafter. The i; Analysis results U viscosity 50,000 mPas % carried out at a maximum of 70 ° C. pH
sediment 4.2
110 mg / kg partially saponified
Polyvinyl alcohol pH partially saponified 4.7 0.28 parts "' pH 115 mg / kg § partially saponified Reaction temperature was 70 pH 4.7 % mechanical stability very good (acidic alcoholysis) 7.5 parts sediment Polyvinyl alcohol 65 mg / kg 0.17 parts sediment very good f Polyvinyl alcohol > "Sediment 95 mg / kg I. Analysis results Resistance to Sodium formaldehyde mechanical stability
removed incrustations (alkaline alcoholysis)
Sodium formaldehyde very good
18g 5 The procedure is the same as in Example 2. mechanical stability 31g f (alkaline alcoholysis) 7.5 parts i mechanical stability very good S: Freeze-defrost cycles very good sulfoxylate 0.35 parts Viscosity after dilution sulfoxylate The reaction temperature is maintained at about 70 ⁰ C. · removed incrustations Sodium formaldehyde removed incrustations 27g § Resistance to Propionaldehyde 0.14 parts (25 parts water) Propionaldehyde 4400 mPas Analysis results ä 15 Viscosity after dilution 820OmPa-S L ) "> sulfoxylate $ 0.32 parts ^; Viscosity after dilution an abrasion in damp Cobalt acetate 0.003 parts Resistance to (25 parts water) I. Propionaldehyde 0.12TeMe t (25 parts water) 5800 mPas | Surroundings Well 35% hydrogen peroxide 0.3 parts a mechanical one Resistance to I. Cobalt acetate 0.03 part no 55 Resistance to Resistance to Sodium bicarbonate 0.12 parts Stress very good a mechanical one very good |. 35% hydrogen peroxide 0.28 parts of Z. a mechanical one Saponifiers Well Storage time very good Stress very good f Sodium bicarbonate
40 αϊ 7 parts 9 Stress very good Storage time very good The procedure is the same as in Example 2, wherein Resistance to 20 storage time The procedure is the same as in Example 2, where '■■ Resistance to Particle size 70%, approx. 500 nm the reaction temperature does not exceed 75 ° C. Freeze-thaw cycles very good Resistance to very good | but 50 parts of vinyl acetate Freeze-thaw cycles very good 30%, Analysis results Particle size 70%, approx. 500 nm Freeze-thaw cycles 30%, approx. 500 nm *
70%, } ⁶⁰ storage time very good less than 500 nm 30%, Particle size less than 500 nm r Particle size 40%, approx. 500 nm no lumps less than 500 nm no lumps,; 50%, removed incrustations 42 g no lumps 5.
Example 8 f less than 500 nm Example 6 ι τ no lumps 65
example 9 100 parts Vinyl acetate 100 parts 95 pieces water 270TeOe 7.5 parts 032 parts 0.12 parts 7th

partially saponified

Polyvinyl alcohol

(alkaline alcoholysis) 12 parts

Sodium formaldehyde

sulfoxylate 0.35 parts

Propionaldehyde 0.12 parts

Cobalt acetate 0.03 part

35% hydrogen peroxide 0.30 parts

Sodium bicarbonate 0.19 parts

The procedure is the same as for Example 2 except that the reaction temperature does not exceed 70 ° C.

Analysis results

27 52 102 10 Vinyl sulfonate 0.2 parts Sodium formaldehyde sulfoxylate 0.52 parts Vinyl derivative A *) 40 parts ■ '' propionaldehyde 0.25 parts 35% hydrogen peroxide 0.3 parts Sodium bicarbonate 0.2 parts Methanol 10 parts

solid components

viscosity

sediment

mechanical stability

removed incrustations viscosity after dilution (25 parts water)

Resistance to

a mechanical one

Stress

Storage time

Resistance to

Freeze-thaw cycles

Particle size

36.5%

34 00 mPas

4.6

46 mg / kg

very good

30 g

570OmPa s

very good very good

very good

50%, approx. 500 nm

50%,

less than 500 nm

no lumps

Example 10

Vinyl acetate 100 parts

Water 135 parts

Hydroxyethyl cellulose 4 parts

Polyglycol ether 2.5 parts

Sodium dodecylbenzene

sulfonate 0.3 parts

20th

*) Viryl derivative of a mixture of cyclic and mostly tertiary acids with 9-11 carbon atoms.

All ingredients are added together with a third of the vinyl acetate, vinyl derivative A and propionaldehyde. Then you start adding the bicarbonate and hydrogen peroxide. Upon reaching a temperature of 60 ⁰ C, the remaining vinyl derivative A ₁ and the remaining vinyl acetate propionaldehyde are supplied and the reaction temperature is adjusted such that it does not exceed 80 ° C. When the reaction has ended and after cooling, methanol and water (ratio 1: 1) are added.

solid components

viscosity

pH

sediment

mechanical stability

Resistance to

Freeze-thaw cycles

resistance

compared to abrasion in

humid environment

Resistance to

Saponifiers

increased storage time

viscosity

Analysis results

51.2% 2800 mPa 4.4

8.0 mg / kg very good

very good

very good

very good very good unchanged

Claims (1)

Patent claims: 1. Process for the preparation of dispersions by emulsion polymerization of vinyl esters, which optionally butyl maleate, ethylhexyl maleate or alkyl acrylate; r.i less than 12 carbon atoms are added in the alkyl radical, in aqueous Medium, in the presence of a water-soluble redox catalyst and a buffer system, as well as optionally plasticizers and other customary additives, characterized in that the polymerization is carried out in two stages performs, where one in the first stage at 25 to 65 ° C of the mixture presented, consisting of