Sulfonate Functional Polyvinyl Acetals

Abstract

Polyvinyl acetals with low solution viscosities and maximum Newtonian flow behavior contain sulphonate-functional vinyl ether or sulphonate-functional allyl ether units in addition to conventional vinyl ester, vinyl alcohol, and vinyl acetal units.

Description

COMPARATIVE EXAMPLE 1

5 ml of a 20% strength methanolic solution of dibutyl peroxycarbonate were added at 57° C., with stirring (100 rpm) to a mixture of 360 g of vinyl acetate and 354 g of methanol in order to initiate the reaction. A total of 35 ml of this initiator solution was then metered in over a period of 225 minutes. 45 minutes after the start of the initiator feed, 437 g of vinyl acetate were used as feed over a period of 2 hours. Once the initiator feed had ended, stirring of the mixture was continued at reflux for a further 2 hours. Cooling gave a 68% strength polymer solution.

INVENTIVE EXAMPLE 2

5 ml of a 20% strength methanolic solution of dibutyl peroxycarbonate were added at 57° C., with stirring (100 rpm) to a mixture of 334 g of vinyl acetate, 27 g of 1-allyloxy-2-hydroxypropylsulphonate, and 354 g of methanol in order to initiate the reaction. A total of 35 ml of this initiator solution was then metered in over a period of 225 minutes. 45 minutes after the start of the initiator feed, a further 405 g of vinyl acetate and a further 32 g of the allyl ether were used as feed over a period of 2 hours. Once the initiator feed had ended, stirring of the mixture was continued at reflux for a further 2 hours.

COMPARATIVE EXAMPLE 3

The procedure was analogous to that of Inventive Example 2, except that instead of the sulphonate-functional allyl ether in each case the same amount of an allyl polyglycol ether having about 23 ethylene oxide units (polyglycol A1100) was used.

COMPARATIVE EXAMPLE 4

The procedure was analogous to that of Inventive Example 2, except that instead of the sulphonate-functional allyl ether in each case the same amount of undecenoic acid was used.

COMPARATIVE EXAMPLE 5

The procedure was analogous to that of Inventive Example 2, except that instead of the sulphonate-functional allyl ether in each case the same amount of crotonic acid was used.

Each of the resin solutions obtained in Comparative or Inventive Examples 1 to 5 was hydrolysed using the following mixing specification to give the polyvinyl alcohol:

713 g of a resin solution adjusted to 30% by weight solids content were covered with 233 g of methanol. After addition of 48 ml of a 15% strength methanolic NaOH solution, stirring (200 rpm) was then started at 30° C. After 210 minutes, the hydrolysis process was terminated by acetic acid (adjustment to pH 7). The precipitated vinyl alcohol copolymer was isolated by filtration, washed with methanol, and dried.

After each of the resin solutions of Comparative or Inventive Examples 1 to 5 had been hydrolysed it was acetalized with butyraldehyde, using the following mixing specification:

150 ml of a 20% strength solution of the vinyl alcohol copolymer and 125 ml of HCl (20% strength) were stirred at stirrer rotation rate 450 rpm into an initial charge composed of 338 ml of deionized water, and the mixture was cooled to 0° C. 23.8 ml of butyraldehyde were then metered in over a period of 45 minutes. After the feed time of 45 minutes, the suspension was held at 0° C. for a further 40 minutes before then being heated to 25° C. over a period of 105 minutes. The reaction was completed over 90 minutes at this temperature. The suspension was then filtered and the product was repeatedly rinsed with deionized water, and dried.

The following products were obtained:

COMPARATIVE EXAMPLE 6

Non-functionalized polyvinylbutyral from Comp. Ex. 1.

INVENTIVE EXAMPLE 7

Allylsulphonate-functionalized polyvinyl butyral from Inv. Ex. 2.

COMPARATIVE EXAMPLE 8

Allyl-polyglycol-ether-functionalized polyvinyl butyral from Comp. Ex. 3.

COMPARATIVE EXAMPLE 9

Undecenoic-acid-functionalized polyvinyl butyral from Comp. Ex. 4.

COMPARATIVE EXAMPLE 10

Crotonic-acid-functionalized polyvinyl butyral from Comp. Ex. 5.

Rheology was tested in the following printing ink mixing specification:

Preparation of printing inks:

Each of the polvinyl butyrals of Comparative or Inventive Examples 6 to 10 was used to produce a varnish whose flow time is 40 seconds in the DIN cup (4 mm aperture) to DIN 53211. 20.8 parts by weight of each varnish were then mixed with 21.7 parts by weight of a solvent mixture composed of ethanol and methoxypropanol (4:1 parts by weight) and with 7.5 parts by weight of pigment (Rubinrot, Irgalith 4BGL) in a disperser over a period of 60 minutes.

Rheological measurement:

Rheology was tested after one day by means of a cone- and plate-rheometer with the following settings: diameter 50 mm, angle 1°. Upward curve and downward curve in each case from 0.2/sec to 1000/sec over a period of 1 minute. Viscosity was measured with a shear gradient of D=10/s, D=100/s, D=1000/s, and the upward curve was measured at D_A=10/s.

The results are given in the table below:

	Comp.	Inv.	Comp.	Comp.	Comp.
	Ex. 6	Ex. 7	Ex. 8	Ex. 9	Ex. 10
D = 10/sec	3640	82	3820	1810	4420
D = 100/sec	423	55	450	480	542
D = 1000/sec	105	44	107	130	133
DA = 10/sec	527	90	69	1130	800

The results show that unfunctionalized polyvinyl butyral (Comp. Ex. 6) and polyvinyl butyrals functionalized with functional groups other than sulphonate functions (Comp. Ex. 8-10) give markedly higher viscosities than the allylsulphonate-functionalized polyvinyl butyral from Inventive Example 7. Furthermore, it is only with allylsulphonate-functionalized polyvinyl butyral that identical viscosities are obtained in the upward and downward curves (newtonian flow behaviour, absence of thixotropy).

Claims

1-10. (canceled)

11. Sulphonate-functional polyvinyl acetals comprise from 0.1 to 50% by weight of vinyloxyalkylsulphonates or allyloxyalkylsulphonates having unsubstituted or substituted, unbranched or branched C1-C6-alkyl groups.

12. Sulphonate-functional polyvinyl acetals of claim 11, comprising: a) from 20 to 70% by weight of vinyl acetal units,b) from 10 to 30% by weight of vinyl alcohol units,c) from 0.5 to 20% by weight of vinyl- or allyloxyalkylsulphonate units or mixtures thereof,d) from 1 to 10% by weight of vinyl ester units,

13. A process for the preparation of a sulphonate-functional polyvinyl acetal of claim 11, comprising acetalizing a hydrolysed vinyl ester copolymer of one or more monomers comprising vinyl esters, unbranched or branched C1-15 alkane carboxylic acids, sulphonate-functional vinyl ether and/or sulphonate-functional allyl ether comonomer(s), having ≧50 mol % of vinyl alcohol units, with one or more C1-15 aliphatic aldehydes, C6-15 aromatic aldehydes, or mixtures thereof.

14. The process of claim 13, wherein at least one aliphatic aldehyde selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde, is used for acetalizing.

15. In a printing ink employing a polymer binder, the improvement comprising employing as at least one binder, a sulphonate-functional polyvinyl acetal of claim 12.

16. The printing ink composition of claim 15, comprising from 5 to 20% by weight of pigment, and from 5 to 15% by weight of polyvinyl acetal binder and solvent.

17. In a corrosion protection composition, an unfired ceramic composition, a metal powder composition, or can coating composition, where an organic binder is employed, the improvement comprising selecting as at least one binder, a sulphonate-functional polyvinyl acetal of claim 11.

18. A can coating of claim 17, further comprising a crosslinking agent.

19. The composition of claim 18, wherein said crosslinking agent comprises an epoxy resin.