DE2353881B2 - Aqueous TETRAFLUORAETHYLENE POLYMERISATE DISPERSION - Google Patents

Description

The invention relates to aqueous dispersions of tetrafluoroethylene polymers, in particular the improvement the shelf life of the same.

Aqueous dispersions of tetrafluoroethylene polymers are prepared by adding tetrafluoroethylene and optionally comonomers in an aqueous solution of polymerization initiator and fluorocarbon dispersant injected with gentle agitation at temperature and pressure polymerization conditions, an aqueous dispersion of about 15 to 45% by weight of tetrafluoroethylene particles of colloidal size less than 1.0 micron in diameter accrues. While the dispersant used during the polymerization (one works with under 1.0% by weight of polymer solids) is sufficient for coagulation to occur during polymerization to prevent the particles of colloidal size settle when the dispersion is stored, whereby the Separated particles form an irreversible coagulum, which when the dispersion is used for layering purposes means a loss of yield.

A nonionic, surface-active one already has for the dispersion after the end of the polymerization reaction Agents added to prevent the premature settling of the tetrafluoroethylene polymer particles (hereinafter also referred to as polymer solids) and thereby stabilizes the dispersion.

The addition of nonionic surfactant after polymerization has also proven to be a viable way to concentrate polytetrafluoroethylene particles in the aqueous phase of the dispersion under certain conditions in the form of surfactant addition and heating, with a decantable layer of water and surfactant (US Pat. No. 3,037,953 and 3,301,807). After concentration, additional surfactant is added to the concentrate to improve stability. According to the last-mentioned patent specification, a higher molecular weight is used for the second addition than for the first surfactant added for concentration. The higher molecular surface-active agent is more effective according to US-PS 33 01807, since its addition to the dispersion as an aqueous solution requires less additional water; As described, the additional water has the undesirable effect of reducing the viscosity of the dispersion.

As recently described in DT-OS 2145 950, when the concentration of nonionic, surface-active agent is increased above the previously normally used maximum value of 6 wt Dispersion gives These stabilized dispersions give a viscosity of 2OcP and higher and often of more than 3OcP. However, the viscosity of the stabilized dispersion is extremely sensitive to the concentration of the surfactant and / or the temperature , which makes it difficult to provide the dispersion user with an aqueous dispersion of reproducible behavior.

The invention relates to an aqueous dispersion based on tetrafluoroethylene polymers, consisting of

A. a homopolymer or copolymer of tetrafluoroethylene with possibly up to 35 percent by weight of other monomers polymerized in,

B. 1 to 6 percent by weight, based on the weight of the polymer A nonionic surface-active Middle,

which is characterized in that the dispersion is 1 to 25 percent by weight, based on the polymer. contains hydrophilic alkylene oxide polymer

The present invention makes aqueous tetrafluoroethylene polymer dispersion compositions of matter are available which have improved stability characteristics and properties. These compositions of matter consist essentially of an aqueous dispersion of Tetrafluoräthylenpolymerem, in their aqueous phase a moderate amount of nonionic, surface-active agent and at least 1 wt .-%, based on polymer solids, dissolved in a substantially hydrophilic alkylene oxide polymer which is not a surfactant in the dispersion according to the invention. These dispersions are more stable on storage than dispersions stabilized with non-ionic surfactant alone are. This advantage can be achieved with a lower viscosity of the dispersion, which is the case with certain applications where easy applicability is critical. In addition, the dispersions show according to Invention of high resistance without requiring large amounts of nonionic surfactant, whereby the side effect of certain, small increases in the content of nonionic surface-active substances Means leading to steep increases in viscosity is avoided. Further the problems viscosity sensitivity to nonionic surfactant content; and Necessity to use large amounts of nonionic during the sintering or fusing of the polymer Burning out surfactant is excluded.

The substantially hydrophilic alkylene oxide polymer component of the dispersion of the invention is made by repeating alkylene oxide units are formed and are used for the purposes of the invention Concentrations, from 1 to 25% by weight, soluble in water at room temperature. The concentrations mentioned here

tion values of this component relate to the Polymer solids in the composition of matter. The alkylene oxide units of the polymer (component C) are "to achieve the essentially hydrophilic character of the polymer

(-CH ₂ O-) (-CH ₂ CH ₂ O-)

\ - CH ₂ CHCH ₂ O- /
Propylene oxide units

(- CH ₂ CH- Ο— \

and higher mol. alkylene oxide units should be avoided with the exception that small proportions of they can be present if they are distributed in a disorderly manner in the polymer, so that the formation of hydrophobic segments in the polymer is avoided, or if the higher molar alkeylene oxide units have sufficient hydrophilic substituents, such as OH in the case of

—CH ₂ —CH — CH ₂ - Ο— \ units
OH

"!O

are substituted.

The essentially hydrophilic character of the polymer is thus offset by the hydrophilic-hydrophobic character of the nonionic surfactants used in the compositions according to the invention, the hydrophobic part of the surfactant appearing to be absorbed on the surface of the tetrafluoroethylene polymer particles dispersed in the aqueous phase. In contrast , the absence of this hydrophobic character in the alkylene oxide polymers used according to the invention means that these polymers do not act as surfactants in the tetrafluoroethylene polymer dispersions according to the invention. This lack of interaction between the dispersed tetrafluoroethylene polymer component and the alkylene oxide polymer component is expressed in the advantages of improved storage stability with lower dispersion viscosity and reduced temperature sensitivity of the dispersion stabilized according to the invention.

The non-surface active nature of these polymers is illustrated by the following values. An aqueous dispersion of tetrafluoroethylene polymer (35% polymer, based on dispersed solids) in the form obtained in the polymerization reaction with a content of less than 1% by weight of dispersant (based on polymer) coagulated in a few ho seconds when exposed to the shear action a Waring mixer operating at the higher speed (Model 702B with dual speed) has been exposed . Such a small amount, in nonionic surface-active agent as 3 <■ * % by weight (based on polymer), gave the dispersion sufficient stability to undergo coagulation only after several minutes with the same shear action, which improves stability by a factor of one hundred In contrast, an essentially hydrophilic alkylene oxide polymer shows no noticeable stabilizing effect in the same and even much higher concentrations in the dispersion in the form obtained during the polymerization without the presence of a nonionic surface-active agent; the dispersion continues to coagulate within a few seconds of the onset of the high-speed Waring mixer shear.

The combination of this alkylene oxide polymer with moderate amounts of nonionic surfactant, however, gives a better stabilization result than using the latter alone.

Examples of substantially hydrophilic alkylene oxide polymers for purposes of the invention are Poly (methylene oxide), poly (ethylene oxide) (generally known and available as polyethylene glycols) and Polyglycerin. Other hydrophilic parts, such as methylene oxide units, can be present in each of these substances in the ethylene oxide polymer and hydroxyl units, which are present as substituents along the polymer chain or on one or more of the polymer end groups. A polyethylene glycol with a molecular weight of about 15,000 is replaced by two smaller polyethylene glycols Chains formed that are linked together by maleic anhydride.

The amount of this polymer (component C) for the purposes of the invention depends on its molecular weight, the desired degree of stabilization and the tetrafluoroethylene polymer concentration of the aqueous dispersion. In general, as the molecular weight decreases, the required amount of this polymer increases, and this relationship is also observed for the polymer solids concentration. Generally available dispersions and alkylene oxide polymers require at least 1 % by weight of this polymer in combination with nonionic surfactant in order to obtain a significant improvement in the dispersion stability. More than 25 % by weight of this polymer is unnecessary to achieve the best possible resistance: in most cases 1 to 6% by weight will suffice. The polymer is used in an amount. which is at least 1 % by weight and is effective for improving the stability of the dispersion.

For the component of the composition of matter according to the invention (component B) formed by the nonionic surface-active agent, any nonionic, surface-active agent can be used which is soluble in water at room temperature (20 to 25 ^° C.) in the desired concentration. The nonionic surfactant can be formed from a single agent or a mixture of such agents. Preferably, the nonionic surface active agent is sufficiently volatile, so that at least 95 wt .-% of the same from the polytetrafluoroethylene during the sintering, are burned which is generally 5 sec. To 10 min. At a temperature in the range from J40 to 400 "C. Typically: such surface-active agents are obtained as reaction products of ethylene oxide with other compounds which introduce hydrophobic constituents into the surface-active agent formed, such as propylene oxide, amines, saturated and unsaturated alcohols and acids and alkylphenols.

active agents are the formulas
R [O (A) _n H] ₁
wherein (A) _{n is} the group

or a mixture of groups

- (C ₂ H ₄ O) T- and - (C ₃ H ₆ O) T-

(where π is in each case an integer equal to 2 to 50 and preferably 2 to 18, b is an integer equal to 0 to 30 and a is an integer equal to at least 2 and where a + b are equal to η ), χ is an integer equal to 1, 2 © der 3 and R is an aliphatic hydrocarbon group, which can be saturated or unsaturated or straight-chain, branched or cyclic or have such features in combination and contains 8 to 24, preferably 8 to 18 carbon atoms, examples of R being oleyl , Stearyl, tridecyl, lauryl, decyl and the groups derived from aliphatic glycols and triols

R'-C ₆ H ₄ O (B), ^

where B is the group

or a mixture of groups

+ C ₃ H ₆ OJ, -

R ³ -N [(CH ₂ CH ₂ O) .H1

R ²

R ³ —CON [(CH ₂ CH ₂ O) H]

where ρ is an integer equal to 2 to 50, ζ is an integer equal to 1 or 2, and R ^{3 is} an alkyl group having 1 to 8 carbon atoms, and R ^{2 is} a chemical bond to a group

■ i CH ₂ CH ₂ O- ^ H
when ζ is 2, and an alkyl group of 1 to 8 carbon atoms when ζ is 1, with the proviso that R ² + R ^{3 result in} at least 5 carbon atoms, and the polyalkylene oxide block copolymers of the formula
s

HO (C ₂ HaO) ^ C ₃ H ₆ O) Z (C ₂ H ₄ OkH

where / "is an integer equal to 15 to 65 and e and g are integers of sufficient size that e + g

together make up 20 to 90% of the total weight of the polymer. With each of the surfactants The mean of the above formulas is such a proportion of the hydrophobic and hydrophilic parts and such a total molecular weight that the

The above requirement for water solubility is satisfied and preferably also the above Volatility is obtained. Other specific surfactants include:

CH ₃ (CH ₂ ) ₄ CH ₂ (OCH ₂ CH ₂ ) ₃ OH
CH ₃ (CH ₂ ) ₆ CH ₂ (OCH ₂ CH ₂ ) ₃ OH

^25th

35

40

means (where m is in each case an integer equal to 2 to 50 and preferably 8 to 20, your integer is equal to 0 to 30 and c is an integer equal to at least 2 and c + d is equal to m ) and R 'is a monovalent, aliphatic and usually saturated group having 4 to 20 and preferably 8 to 12 carbon atoms, and

50

ss

65 ₃ ) CH ₂ ) ₅ OH

CH ₃ (CH ₂ ), CH ₂ (OCH ₂ CH ₂ ) ₅ OH

The nonionic surfactant is generally used in the dispersions according to the invention used in the amount that is sufficient to stabilize the polymer particles in the dispersion, what prevents their coagulation. Theoretically, this is the amount that is required to film the surface of the Polymer particles in the dispersions is required, this amount from the surface of the polymer particles which in turn depends on the particle size and weight percentage of the polymer present is dependent. In practice one will work with a certain excess of surface-active agent in order to ensure coverage on all polymer particles present, but even in this case the Amount is much smaller than it is according to DT-OS 21 45 960 to achieve the surprising increase in viscosity the dispersion is required. For the most common nonionic surfactant, about the available and primarily of interest polymeride dispersions generally 2 to 4% by weight the end. For other nonionic surfactants of higher or lower molecular weight larger or smaller quantities may be necessary. Generally speaking, the concentration of the nonionic surfactants in compositions according to the invention 1.0 to 6.0% by weight be. The surfactant concentrations mentioned here refer to the Weight of polymer solids in the dispersion.

The tetrafluoroethylene polymer in the compositions of matter according to the invention can be of the Homopolymers, polytetrafluoroethylene, or a copolymer of tetrafluoroethylene with be a minor proportion of other, copolymerizable, ethylene-saturated monomer. That Homopolymer can e.g. B. also small amounts of comonomer modifier! included, with the

Character of the homopolymer of not being processable in the melt continues to exist, such as up to 2 wt .-% of polymer units obtained by copolymerization of perfluoroalkyl or Oxyperfluoralkyltrifluoräthylen having 3 to 10 carbon atoms, preferably hexafluoropropylene, with tetrafluoroethylene (such as described in US-PS 31 42 665). In order to make the resulting copolymer melt-processable, larger amounts of these monomers or other monomers can also be present in amounts of up to 35% by weight. Examples of such copolymers are copolymers of tetrafluoroethylene with monomers such as hexafluoropropylene (as described in US Pat. No. 2,946,763), higher perfluoroalkenes. such as those with 4 to 10 carbon atoms, perfluoro (alkyl vinyl ethers), such as perfluoroethyl or perfluoropropyl vinyl ether (as described in LJS-PS 31 32 123). Perfluoro (2-methylen-4-methyl-1,3-dioxolane) (as described in US-PS 33 08 107) and the highly fluorinated monomers in which there is a single hydrogen atom that does not change the fluorocarbon character of the copolymer, examples of such monomers being 2-hydroperfluoroalkene having 1 to 3 carbon atoms, such as 2-hydropentafluoropropene. the ω-hydroperfluoroalkenes with 3 to 10 carbon atoms and the o> hydroperfluoro (alkyl vinyl ethers), which have 1 to 5 carbon atoms in the alkyl group.

The polytetrafluoroethylene in the aqueous dispersion composition according to the invention belongs to the aqueous dispersion type of polytetrafluoroethylene (in contrast to the grain type). As a specific melt viscosity of at least 1 × 10 ⁹ P at 380 ° C. under shear stress of 0.46 kg / cm ² shows, it has an extremely high molecular weight or belongs to the melt-processable type with a melt viscosity of 1
same conditions)

■ 10 ³ P to 1 · 10 ⁶ P (for the an. The average diameter of the tetrafluoroethylene polymer particles in the dispersion is determined using a relationship based on the theory of light scattering, from the percentage of incident light that, at 546 Millimicron wavelength passes through a unit amount of a dilute, aqueous dispersion (about 0.02% by weight polytetrafluoroethylene particles using a nominal value of 0.020 cmVg homopolymer for the quotient of the partial refractive index Δ π and Δ c of the dispersion at 25 ⁼ C. The particle size obtained in this way represents an average particle diameter of the measured particles and corresponds to theory, as confirmed by an analysis with the ultracentrifuge or a direct measurement of electron micrographs of the particles at 20,000 times magnification, almost that Weight average particle diameter he. The particles can have a rectangular shape or be irregular, such as oblong. Preferably the average particle diameter of the polytetrafluoroethylene particles in the dispersion is 0.32 to 0.45 microns; The invention is also applicable to the finer table sizes, e.g. B. down to an average particle diameter of 0.05 microns, applicable, which are characteristic of some of the available aqueous homopolymer and copolymer dispersions Tetrafluoräthylenpolymer The concentration in the aqueous medium is preferably 55 to 65 wt .-%. The tetrafluoroethylene polymer concentrations (polymer solids) mentioned here relate to the weight of the total dispersion.

To prepare the dispersion according to the invention, the surfactant and the> alkylene oxide polymer can be added to the aqueous dispersion after the polymerization. If the polymer solids concentration of the dispersion in the form obtained during the polymerization is below the desired value, the dispersion can be concentrated, such as

ίο by the method of operation of the addition described above of surfactant and decanting, and then to the concentrated, aqueous dispersion that Add alkylene oxide polymers. The content of the concentrated, aqueous dispersion of surface-active

is tive means in the latter case is im generally 1.0 to 4.0% by weight, and the addition of further surface-active agent is not necessary. By adding the alkylene oxide polymer to the concentrated dispersion, the desired Storage stability of the dispersion can be obtained. The resulting, stabilized, aqueous polytetrafluoroethylene dispersion can be used in the same way as previously available aqueous tetrafluoroethylene polymer dispersions. So the dispersion is suitable according to

2s invention as a coating or coating agent, e.g. B. for fiberglass or silk mats.

The viscosity of the dispersion is measured using a Brookfield Synchro-Lectric type viscometer, model LTV. All measurements are carried out at 60 rpm and a temperature of 23 to 27 ^C C using the appropriate spindle. The determination of the storage stability is carried out with reference to the speed of the coagulum or sediment formation in an aqueous polytetrafluoroethylene dispersion, which is in an amount of 100 ml in a 100 ml graduated cylinder which was sealed with a cap and at ambient conditions (approximately 25 ⁰ C) is left to stand. Every 30 days, the height of the interface between the dispersion and protruding, clear material (in ml) is measured and the cylinder is then turned over once and the volume of the sediment that has accumulated on the bottom (in ml) is measured.

To quickly check the sedimentation rate, 30 ml of polytetrafluoroethylene in an aqueous dispersion are added to a calibrated; Spin tube, spins for 2 hours (on a medical centrifuge - model X-213 International Clinical - with a head that holds two 15 ml and two 50 ml containers) at 2000 rpm, pours the dispersion and determines the volume of sediment remaining in the container

The following examples, in which parts and percentages, unless otherwise stated, refer to:

Refer to weight, serve the purpose of further explanation

¹ ^ "" ■ ' -a-

For comparison purposes, a series of aqueous dispersions containing polytetrafluoroethylene in a concentration of 60% by weight and with an average particle diameter in the range from 0.32 to 5035 microns and non-ionic. surfactant in an amount (after concentration to the aforementioned polymer solids concentration) of 1:% by weight. Various amounts of additional nonionic surfactant were added to these dispersions in order to demonstrate the effect of using surfactant alone to improve storage stability.

Disper Total salary Viscosity of the Camp-- sion on surface Dispersion. resistance active cP at 25 ^° C (Quick check). Medium, wt% ml of sediment a 3.3 11.2 9.0 b 5.3 13.3 6.8 C. 7.3 17.6 3.8 d 9.3 IbO 3.8 e 11.3 336 3.0 f 2.0 11.5 10.0 G 4.0 11.8 10.0 H 6.0 14.8 6.8 i 8.0 16.9 4.0 J 10.0 21.5 2.3 k 12.0 224 1.7

In dispersions a- e .v was used as a surface-active agent to narrow the dispersion as a non-ionic agent

CH J

(A)

and for the following addition of nonionic surfactant

CH ₃ (CH ₂ ) ,,, - ,, CH ₂ (OCH ₂ CH ₂ ) ,, -,

(B)

used. In the case of dispersions f-k, a surfactant was used to narrow the dispersion

CH ₁ ClCH, I ₂ CH ₂ QCH, I ₂ -;

used and after narrowing to achieve the

5- (OCH ₂ CH ₂ I ₁₀ OH (C)

the same nonionic surface-active agent is added to the content mentioned in the table above.

As the results shown in the table show, the combination of surface-active ethoxyl used in dispersions a-c requires. aliphat. alcohol means a concentration of 7 wt .-% ,: before a tolerable level of storage is resistant ness achieved while a good Bestandigkei 11.3% are required, but being established a Viskositä of 336 cP. The dispersions f-k show a similar behavior; A surfactant concentration of 8.0% is necessary in order to achieve an acceptable shelf life, while 12.0% must be used for a very good shelf life, which is associated with a viscosity of 224 cP.

Examples 1 to 14

These examples illustrate the high shelf life, indigenous by replacing a larger part of the bishei conventionally added surfactant ει By means of polyethylene glycols different Mole kulargewichts can be achieved. It was the same aqueous polytetrafluoroethylene dispersion as in liei above comparison tests used, and the Geha! of surfactant corresponded to the remainder ar nonionic surfactant, which after decanting the layer of water and surfaces active agent remains in the dispersion. To de resulting, concentrated, aqueous dispersion was Then polyethylene glycol was added and the dispersion was checked for storage stability. Results:

Example

Surface polyethylene glycol

active agent ¹ ).

Wt% molecular weight

Wt% ^; )

Viscosity.
cP at 25 ° C

sediment
volume,
mi

2.0
2.1
2.1
2.1
2.1
2.1
2.0
1.8
1.8
1.8
1.8
1.8
2.0
2.3

1300-1600

6000-7500

6000-7500

6000-7500

6000-7500

6000-7500

5000-7500

6000-7500

15,000

15,000

15,000

15,000

570-630

6000-7500

13.3
1.3
2.0
2.7
3.3
4.0
5.0
6.7
1.3
2.7
4.0
5.3

18.7
2.7

33.9
15.2
18.3
19.2
23.2
24.6
29.2
38.7
20.4
42.4
95.5 196 31.3 16.3

1.6
7.5
4.2
3.2
2.0
2.5
2.5
1.2
2.6
1.0
0.4
0.2
1.8
2.7

') In Example 1 to 13 C and in Example 14 A. ^s ) Based on polymer solids.

As these results show, polyethylene glycol is more effective than nonionic, surface-active agent in improving the storage stability: With relatively lower concentrations of polyethylene glycol, the dispersion achieves just as much better storage stability as, or rather, with higher concentrations of nonionic, surface-active agent, and this The result is obtained without the excessive increase in the dispersion viscosity which otherwise occurs. In dispersion c, for example, a surfactant concentration of 7.3% by weight was necessary in order to achieve a sediment volume of 3.8 ml.

while a sediment volume of 3.2 rr at a total concentration of additives (oberflä chenaktives equivalents plus glycol) of 4.1 wt ⁰ / is obtained in Example 3, and Example 9 shows an even better result ■ at a total concentration of additives of only 3.1% by weight.

Examples 15-19

In this series of experiments were surface-active with vem agent alone and with surface-active agent plus polyethylene glycol stabilized dispersions

subjected to long-term storage stability testing, the same aqueous polytetrafluoroethylene dispersion as used above. One of the samples of the concentrated, aqueous dispersion (polymer solids 61.9% by weight) contained 2.1% by weight of surface-active material remaining from the concentration stage Center! (A) and 7.5% by weight (B) was added. the

The resulting dispersion had a viscosity of 270 cP at 25 ° C and formed 11 ml of sediment after storage for 4 months at ambient temperature. Other samples of the dispersion concentrated with (C) (polymer solids 60.0% by weight) were with different amounts of polyethylene glycol of different molecular weight added. Results:

example surfaces Polyethylene glycol Wt% Viscosity, Sediment after active agent, 2.7 cP at 25 "C 4 months, Wt% Molecular weight 5.0 ml 15th 2.1 6000-7500 3.0 19.9 3 Ib 2.0 6000-7500 5.3 29.2 -> 17th 1.85 15,000 13.4 46.0 4th 18th 1.81 15,000 196 2 19th 2.0 1300-1600 33.9 3

These results show an improved shelf life under actual conditions Wagering resemblance. This improvement is, like the results further / inherent, with smaller ones Concentrations of additive achievable.

Examples 20 and 21

This series of tests explains the relative insensitivity of the viscosity of dispersions according to the invention to small changes in temperature. The aqueous polytetrafluoroethylene dispersion described in detail above was concentrated to a polymer solids content of 59.5% by weight using (A) and then to a surfactant content of 9.0% by weight by adding (B) .-% brought. This dispersion had a viscosity of 35 cP at 23 ° C. which increased almost linearly with the temperature to 64 cP at 27 ^r C.

The same aqueous polytetrafluoroethylene dispersion was used for comparison concentrated using (C) and the resulting concentrated dispersion (60.7 wt% polymer solids) containing 2.8 wt% of this surfactant at 2.7 wt% Polyethylene glycol (molecular weight 6000 to 7500) added. The resulting dispersion showed in the temperature range constant viscosity from 23 to 27 ° C.

In a corresponding manner, the same dispersion, which was concentrated to 60% by weight of polymer solids and had a residual surfactant content of 1.8% by weight (C), was mixed with 32 % by weight of polyethylene glycol with a molecular weight of 15,000 offset. The resulting dispersion had a viscosity of 57 cP at 23 ⁰ C, the linearly reduced with increasing temperature to 50 cP at 27 ° C.

Example 22

The procedure and polyethylene glycol essentially corresponded to Examples 9 to 12 with the modification, that the concentration of surfactant was 4.0% by weight and glycol was 3.3% by weight. The accruing The dispersion gave a viscosity of 60.1 cP at 25 ° C. and a sediment volume in the storage stability test from 0.3 ml.

Example 23

In this experiment, a methoxypolyethylene glycol with a molecular weight was used as the alkylene oxide polymer used by about 5000. An aqueous dispersion of polytetrafluoroethylene, which after concentration 2.2% by weight of C was reduced to a content of the above glycol of 6% by weight and a polytetrafluoroethylene solids concentration formulated by 60%. The resulting dispersion had a viscosity of 20 cP at 25 ° C. and a sediment volume of only 1.5 ml.

Example 24

The procedure of Example 23 was essentially repeated, with the modification that the alkylene oxide polymer used was an ethylene oxide polymer which had a small proportion of pronylene oxide units and a hydroxyl end group in a random distribution along the polymer chain. The concentration of this oxide polymer in the dispersion was 4.3% by weight. The resulting dispersion, which had a polymer solids content of 60%, had a viscosity of 19.7 cP at 25 ° C. and a sediment volume of only 1.8 ml.
45

Example 25

The procedure of Example 23 was essentially repeated except that an additive; of decaglycerine as alkylene oxide polymer to the dispersion took place in such an amount that a < Concentration of 20 wt .-% was reached. The resulting dispersion of 60% polymer solids-Ge Halt resulted in a viscosity of 17.0 cP at 25 ° C and egg? Sediment volume of only 1.5 ml.

Example 26

The procedure of Example 23 was essentially repeated with the modification that the concentration of (C) was 1.8% by weight and the glyc (a linear glycol with a molecular weight of about 18,500 was used in such an amount that a concentration of 3.3 wt ^u / om the dispersion was achieved. the resulting dispersion of 60 ° polymer solids content gave a viscosity ve 32.4 cP at 25 ° C and a sediment volume of 1.9 ml ni.

Claims (2)

Patent claims: 1. Aqueous dispersion based on 'Tetrafluoroethylene polymers, consisting of A. a homopolymer or copolymer of tetrafluoroethylene with possibly up to 35 percent by weight of other monomers polymerized, B. 1 to 6 percent by weight, based on the ι ο Weight of polymer A of nonionic surfactants, characterized in that the dispersion C. 1 to 25 percent by weight, based on the polymer, of hydrophilic Alkylenoxydpolyme rer contains 2. Dispersion according to claim 1, characterized in that the used hydrophilic alkylene oxide polymers Is polyethylene glycol.