USE OF COMPACTED POLYVINYL ACETALS AS BINDER IN CERAMIC GREEN SHEETS

Abstract

Use of a compactate comprising polyvinyl acetal as a binder for the production of a ceramic green sheet or a ceramic moulded body wherein the polyvinyl acetal has a molecular weight of equal to or more than 50,000 g/mol when measured by gel permeation chromatography according to DIN ISO 16014-1:2019-05 and a suspension composition comprising one or more inorganic pigments, one or more organic solvents, one or more binders, one or more plasticizers, and one or more dispersing agents, wherein the binder is the compactate, are disclosed.

Claims

1. A method for producing a ceramic green sheet or a ceramic moulded body, the method comprising: preparing the ceramic green sheet or the ceramic moulded body using a compactate comprising polyvinyl acetal as a binder, wherein the polyvinyl acetal has a molecular weight of equal to or more than 50,000 g/mol when measured by gel permeation chromatography according to DIN ISO 16014 1:2019-05.

2. The method according to claim 1, wherein the polyvinyl acetal is polyvinyl butyral.

3. The method according to claim 1, wherein the polyvinyl acetal has a molecular weight of equal to or more than 50,000 g/mol and equal to or less than 150,000 g/mol when measured by gel permeation chromatography according to DIN ISO 16014 1:2019-05.

4. The method according to claim 1, wherein the compactate has a median particle size of 1 to 5 mm.

5. (canceled)

6. A compactate, comprising polyvinyl acetal with a molecular weight of equal to or more than 50,000 g/mol when measured by gel permeation chromatography according to DIN ISO 16014 1:2019-05.

7. The compactate according to claim 6, which has a median particle size of 1 to 5 mm.

8. A process for preparing the compactate according to claim 7, the process comprising: compacting a polyvinyl acetal powder using a roller mill.

9. A suspension composition, comprising: one or more inorganic pigments, one or more organic solvents, one or more binders, one or more plasticizers, and one or more dispersing agents, wherein the binder is the compactate according to claim 6.

Description

EXAMPLES

Example 1PVB Compactate 1

[0031] Polyvinyl butyral powder (Mowital B 75 H with a molecular weight of 100,000 g/mol+/10,000 g/mol) is drawn between two counter-rotating, water-cooled rollers using a roller compactor with a line pressure of 15 kN/cm at a temperature of 45 C. The resulting 0.5-1.0 cm thick sheets are then crushed and subsequently further reduced in size with the aid of a granulator to obtain a compactate with a median particle size of 1-3 mm.

Dissolution Behaviour of PVB Powder Vs. PVB Compactate

[0032] 10 g of PVB powder or compactate, respectively, was mixed with 90 g of a solvent mixture (1:1 mixture of ethanol and toluene). For the dissolution process, a rotating and tilting mixer was used (supplier: IKA, model: Kipp-/Rollenmischer, digital, 6).

[0033] After defined periods of time (0 h, 3 h, 6 h, 18 h and 24 h) the mixer was stopped and 1 g of the supernatant was taken and the solid content was determined with the help of an oven to evaporate the solvent. For the analysis a digital precision balance was used.

TABLE-US-00001 Dissolution rate in [%] Start Time: Time: Time: Substrate (0 h) 3 h 6 h 18 h Mowital B 75 H Powder 0% 90% 98% 100% Compactate 1 of Mowital B 75 H 0% 100% 100% 100%

Results

[0034] Compactate 1 is completely dissolved after 3 hours already. On the other hand, the corresponding powder material needed a dissolution time of more than 6 hours to be completely dissolved.

Particle Counts in Solution of PVB Powder and PVB Compactate

[0035] Compactate 2 was prepared as described above for compactate 1 except that Mowital B 30 HH, a PVB with a molecular weight of 35,000 g/mol+/10,000 g/mol commercially available from Kuraray Europe GmbH, was used.

[0036] 2 g of PVB powder or compactate, respectively, was dissolved in 98 g of a solvent mixture (1:1 mixture of ethanol and toluene) using a tilting/rotating mixer. After 24 hours, a 50 ml sample was taken and analyzed by single particle measurement with laser focus using the Accusizer 780 by Soliton GmbH. Only particles with sizes in the range of 2-500 m were counted.

TABLE-US-00002 Counts per mL Increase of particle (particle size counts in % from Substrate 2-500 m) powder to compactate Mowital B 75 H 218 Compactate 1 467 +114% Mowital B 30 HH 155 Compactate 2 710 +358%

Results:

[0037] Residual particles with a size of 2 to 500 m can be a major problem in the production of ceramic green sheets and the amount present in the binder solution must therefore be minimized. While the compacting process with regard to compactate 1 shows only moderate increase in particle size, compacting the PVB material with a lower molecular weight (compactate 2) surprisingly leads to a much higher increase of particle count from powder to compactate.