CS243511B1 - Medium for screen printing pastes - Google Patents

Abstract

The medium for the production of screen printing pastes, especially for decorating ceramic ware under glaze by screen printing in rapid firing conditions, consists of a mixture of at least one substance from the group comprising block copolymers of propylene oxide and ethylene oxide and condensates of fatty, preferably coconut acids with diethylene glycol and formaldehyde and at least one substance from the group comprising polyvinyl acetate, acrylate copolymers with vinyl acetate and resin acids, preferably abietic acid.

Description

(54) Medium for the production of screen printing pastes

The medium for the production of screen printing pastes, in particular for screen printing of ceramic shards under the glaze under high-speed glazing, consists of a mixture of at least one substance selected from block copolymers of propylene oxide and ethylene oxide and condensates of fatty, preferably coconut, a group selected from polyvinyl acetate, acrylate copolymers with vinyl acetate and resin acids, preferably abietic acid.

BACKGROUND OF THE INVENTION The present invention relates to a medium for the production of screen printing pastes, in particular for screen printing under ceramic glazing, under rapid-firing conditions.

Screen printing is one of the modern methods used to decorate ceramic shards under the glaze. It consists in the application of pastes containing a frit dye and medium on the body, optionally glazed, followed by firing. The firing is carried out at temperatures between 1100 and 1150 ^U C for 3 to 20 hours.

For economic reasons, rapid firing is also used at temperatures below 1000 ° C for a maximum of 1 hour. Until now, it is not possible to use quick firing on decorated and then glazed shard, because the color of the decor does not react sufficiently with the glaze and the final product is of poor quality.

Therefore, rapid firing can only be used for glazing. However, this procedure requires the use of a body with a higher degree of water absorption. In order to keep the decor in the desired shape during further processing, it must be fixed with special fixatives.

The processing of decorated glazed materials in this manner also greatly causes mechanical defects on the glazing (e.g., scraping, abrasion, peeling, punching, bouncing, etc.), but also peeling of the applied paste during decorating, and uneven decor edges.

These drawbacks cause considerable waste in decorating.

According to the invention, these disadvantages are overcome by the medium for the production of screen printing pastes, in particular for the screen printing of ceramic shards under the glaze under rapid-firing conditions. SUMMARY OF THE INVENTION The medium consists of a mixture of at least one substance selected from the group consisting of block copolymers of propylene oxide and ethylene oxide containing from 65% to 75%, preferably 70% by weight of ethylene oxide, the molecular weight of the propylene oxide base being 900 and fatty condensates. preferably coconut acids in length carbon chain Οθ to θ £ _Ο, with diethylene glycol and formaldehyde in the molar ratio 1: 4: 4 to 1: 8: 8, preferably 1: 6: 6, and at least one substance from the group comprising polyvinyl acetate, acrylate copolymers with vinyl acetate and resin acids, preferably abietic acid, in a weight ratio of 70% to 99.5% of the first group and 0.5% to 30% of the second group.

The medium according to the invention provides improved bonding of the screen printing paste and the glaze due to the reduced interfacial tension between the printed material and the transparent glaze, as well as a better coloring or blending of the paste and glaze on the contact surface.

A short firing time at lower temperatures is then sufficient to produce the desired reaction. It also reduces printing errors, eliminates marginal irregularities in the sample and prevents damage to the glaze.

A further advantage of the medium according to the invention is the reduction of the amount of waste in decorating and the lower consumption of netting in the production of decorative plates, while avoiding the sticking of the glaze on the screen during printing. In addition, there is no need to use it when decorating fixatives.

The advantages of the medium according to the invention are illustrated in more detail by the following examples: all ratios of the individual components, parts and percent, are by weight.

Example 1

A mixture of 4 parts propylene oxide / ethylene oxide block copolymers containing 70% ethylene oxide is prepared, wherein the molecular weight of the propylene oxide base is 900, and 1 part polyvinyl acetate with 9 parts water.

The medium thus prepared is stirred for 2.5 hours in a mixer with 0.950 kg of ZTA 6473 flux consisting of 13.6% silica, 0.5% alumina, 0.2% calcium oxide, 0.2% magnesium oxide, 2.0% of zinc oxide, 60.4% of lead oxide, 20.1% of phosphorus pentoxide and 0.05 kg of K 507 dye, consisting of iron, chromium and aluminum oxides. The resulting paste is applied to the body by sieve No. 19 and glazed with a transparent glaze. The sample is baked at 980 ° C for 55 minutes.

The finished product exhibits a perfect surface without defects caused otherwise by screen printing.

Example 2

Medium from 4 parts / i. 80%) of coconut acid condensate with diethylene glycol and formaldehyde in a molar ratio of 1: 6: 6 and 1 part (i.e. 20% acrylate copolymers with vinylacetate and 12 parts water.

An amount of 0.25 kg of this medium was mixed for 2.5 hours on a paste, which was coated with No. 14 sieve on a shard and glazed with a transparent glaze. After firing for 56 minutes at a temperature of 975 ° C, a flawless product was obtained which was perfectly reacted and with a perfect décor shape without further damage.

Example 3

A medium was prepared from a mixture of coconut acid condensate with diethylene glycol and formaldehyde in a molar ratio of 1: 6: 6 and resin acids in a ratio of 98% coconut condensate and 2% resin acids, and 1 part of this mixture was stirred for 2.5 hours in mixer with 10 parts water and 0.96% flux ZTA 6473 and 0.04 part K 90368.

The resulting paste was applied through a No. 19 sieve to shard and was flash fired for 56 minutes at 980 ° C after glazing with a transparent glaze.

Perfect decor was obtained, well recognizable and reacted through the glaze, without tearing or other damage.

Example 4

Following the procedure of Example 3, where 2% abietic acid was used instead of resin acids, an impeccable decor was again obtained, well reacted with the glaze.

Example 5

A medium of 80% propylene oxide / ethylene oxide block copolymers according to Example 1 and 20 Ϊ acrylate copolymers with vinyl acetate was prepared. Κ 1 part of this mixture was added 10 parts of water.

An amount of 0.27 kg of the thus prepared medium was introduced into a mixer with 0.98 kg of ZTA 6473 flux and 0.22 kg of K 507 and mixed for 2.5 hours, the resulting paste was applied through a No. 19 sieve to shard and glazed with transparent glaze. The firing was carried out in an oven at 975 ° C for 56 minutes.

The finished product showed a perfectly reacted decor without any damage.

Example 6

1000% water was added to the prepared medium of the 98-propylene oxide-ethylene oxide block copolymers of Example 1 and 2% resin acid mixture. An amount of 0.27 kg of the mixture thus prepared was added to the mixer and stirred for 2.5 hours.

The resulting paste was applied through a No. 19 sieve to the body and glazed with a transparent glaze. The firing was carried out in an oven at 975 ° C for 56 minutes.

The finished product showed a perfectly reacted decor without any damage.

Example 7

To the prepared medium of 80% coconut condensate according to Example 2 and 20% polyvinyl acetate was added 1000% water. An amount of 0.27 kg of the flux thus prepared was introduced into a mixer with 0.98 kg of ZTA 6473 flux and 0.22 kg of K 507 dye, and stirred for 2.5 hours.

The resulting paste was coated with No. 19 sieve on a shard and glazed with a transparent glaze. The firing was carried out in an oven at 975 ° C for 56 minutes.

The finished product showed a perfectly reacted decor without any damage.

Example 8

To the prepared medium of 50% block copolymer according to Example 1, 30% coconut acid condensate mixture according to Example 2, 12% polyvinyl acetate and 8% acrylate copolymers with vinyl acetate were added 1000 parts of water.

An amount of 0.25 kg of this mixture was added to the mixer along with 0.930 kg of ZTA 6473 flux and 0.05 kg of K 507, and mixed for 2.5 hours. The resulting paste was applied through a No. 19 sieve to the body and glazed with a transparent glaze. Firing in an oven for 35 minutes at 980 ° C provided a flawless product without any defects.

Example 9 κ 1000% water was added to the prepared medium of 50% block copolymer according to example 1 and 48% coconut acid condensate according to example 2 and 2% resin acids according to example 3.

An amount of 0.27 kg of the thus prepared mixture was added to the mixer along with 0.98 kg of ZTA 6473 flux and 0.02 kg of K 507, and mixed for 2.5 hours, the paste was applied through a No. 19 sieve to shard and glazed with transparent glaze. The firing was carried out in an oven at 975 ° C for 56 minutes.

The final product showed a perfectly reacted decor without any defect.

Claims (1)

SUBJECT OF THE INVENTION Medium for the production of screen printing pastes, in particular for screen printing of ceramic bodies under glaze under rapid-burning conditions, characterized in that it consists of a mixture of at least one substance selected from the group consisting of block copolymers of propylene oxide and ethylene oxide. 65% to 75%, preferably 70% ethylene, wherein the molecular weight of the propylene oxide base 900 and condensates of fatty preferably coconut acids in length carbon chain Cg-C _2Q with diethylene glycol and formaldehyde in the molar ratio 1: 4: 4 to 1: 8: 8, preferably 1: 6: 6, and at least one of the group consisting of polyvinyl acetate acrylate copolymers with vinyl acetate and resin acids, preferably abietic acid, in a weight ratio of 70% to 99.5% of the first group substance and 0.5 up to 30% of a second group substance.