DE2323104B2 - METHOD OF MANUFACTURING A MICROPOROUS PRINTING PLATE - Google Patents

Description

The invention relates to a method for making a microporous printing plate.

It is known to use a sponge rubber for printing, in particular for stamping, which has numerous interconnected micropores and which forms a printing or stamping surface in which printing or stamping ink is absorbed so that it is not it is necessary to have a new printing or stamping color on the printing or stamping surface for each imprint to apply.

Sponge rubber is usually made in a process that excludes unvulcanized rubber a propellant is added to the usual additives, whereupon the mixture with the help of rubber processing rollers kneaded and mixed intimately and then hot-pressed in a mold so that the gum is foamed and vulcanized. Such a process is very troublesome because of kneading and Vulcanizing require a lot of time and labor. In addition, those under the action of the propellant are in the Sponge rubber formed micropores not uniformly large and not uniformly distributed, so that the Micropores are uneven. This is undesirable for a stamp. Besides, the usual one Sponge rubber not as durable as desired.

The same manufacturing process and quality problems arise with the Use of sponge rubber in inking rollers used in printing technology.

There is therefore a need for a relatively simple method of making printing plates high durability with evenly distributed micropores.

The applicant has therefore set himself the task of creating a method for the production of printing plates which have numerous, evenly distributed and 104

have interconnected micropores, easy? high durability i.nd have a high absorption capacity for printing inks show.

This object is achieved according to the invention in that by mixing a photopolymerizable, liquid polyurethane with a viscosity of 1 to 100 P at 25 ° C with finely powdered table salt, sodium nitrate, sugar, tartaric acid or dextrin in a mixing ratio of polyurethane to finely powdered material of 1: 2 , 5 to 1: 5, based on the weight, a homogeneous mixture is produced, this liquid mixture is poured into a mold with a suitable shape, the mixture poured into the mold is irradiated with light of a wavelength of 300 to 400 μιτι to the to photopolymerize liquid polyurethane to a solid shaped body, whereby the light used for the irradiation can be kept away from certain parts of the surface of the mixture poured into the mold, the shaped body is removed from the mold and, if necessary, the mixture which has remained liquid is allowed to run off, then the shaped body in water is immersed in order to remove the fine powdery material in the for To dissolve m body and remove, and the resulting microporous molded body is dried.

The method according to the invention allows the production of microporous printing plates of high quality Durability that have uniformly large and uniformly distributed micropores.

From the publication “Chem. Zentralbl. «1962, p. 2611 the photopolymerization of liquid polyurethane compositions is known. From this publication it can be however, it does not teach the creation of the use of photopolymerizable polyurethanes of microporous printing plates with the excellent properties.

In FR-PS 15 15 026 are porous plastics has been described. For their production, for example, table salt or sugar are made from the hardened Leached mass. However, the patent is unable to provide any stimulus through photopolymerization of polyurethane printing plates to be produced in the manner according to the invention.

The printing plate produced by the method according to the invention has numerous micropores that distributed in the molded body and connected to other micropores. It has an excellent Ink absorbency and excellent durability. You can do it for parts of Use printing machines, for example for printing plates or inking rollers.

During the irradiation with light there is liquid on the surface of the poured into the mold Polyurethane a negative film or the like. Provided to keep the light away from certain parts of the surface. In this way, moldings in the form of letters or figures to be printed can be produced. Man the mixture of the liquid polyurethane and the finely powdered material can be applied to a suitable substrate pour and in these cases use the product as a printing plate with or without further processing.

Depending on the type of liquid polyurethanes, these can be molded parts of different strength, from soft to tough, form. One uses the variety that results in a microporous material that is the desired one Quality. The viscosity of the photopolymerizable, liquid polyurethanes is Temperature of 25 ° C in the range of 1 to 100 P,

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must be the fine powder: «Material m pay attention & t

This forum fc & iner will «in the form of a fine one Powder used, which preferably has such an S Grain size hai that it passes through a sieve of 200 mesh goes.

The photopolymerizable liquid polyurethane and the powdery material can be mixed homogeneously in any conventional mixer, for example a rotary mixer. The weight ratio of the liquid polyurethane * u the pulverulent material is from 1 25 to 1: 5> preferably 1: 3 to i: 4. If the ratio is within the above range, a compound of the pores in the product to each other is ensured, and there is obtained a microporous material that has an appropriate pore distribution and durability. After mixing, the mixture obtained is left to stand and / or evacuated so that the foam formed during mixing is destroyed *>. The foam-free liquid mixture is then poured into a suitable mold.

In a preferred embodiment of the invention, the cavity of the mold can have any shape have, for example correspond to a plate, a rod or a cylinder.

The mold can be made of any material that is inert to the liquid polyurethane. Man can use thermoplastics, e.g. B. polypropylene or thermosetting plastic, e.g. B. unsaturated poly jo ester. It is preferred to use a material of high corrosion resistance, e.g. B. stainless Steel or glass. In order to enable the irradiation with light to be carried out properly, used it is best to use clear glass. At least one side of the form must be translucent.

The irradiation takes place with light with a wavelength in the range from 300 to 400 / tm. Ultraviolet light in this wavelength range can easily be generated with the help of known light sources, for example with high pressure mercury vapor lamps. The required exposure line is from the Layer thickness of the liquid polyurethane to be photopolymerized and the light intensity depends and is with a layer thickness of a few millimeters, usually several minutes to about 20 minutes.

The photopolymerization is generally carried out by radical polymerization. The radical polymerization can only with difficulty advance in the zone in which the polymerizable liquid polyurethane of the Exposed to air. Therefore, the irradiation must be carried out in a vacuum or in an inert gas atmosphere or the surface of the liquid polyurethane is protected from the ingress of air by a suitable cover will.

Through the photopolymerization of the liquid mixture a solid molded body is formed in which a soluble, finely powdered material is evenly distributed is. The molded body is taken out of the mold and put in the solvent for the fine powder Material immersed. In the immersed shaped body, the existing on its surface are first Powder particles dissolved and removed from the surface, so that micropores are formed there in the the solvent progressively penetrates, whereupon the fine powder particles inside the casting dissolves, so that numerous micropores are formed, which are connected to one another in the molded body.

The required thawing time can last several hours «U amount to a day or a few days; this is «sn the thickness of the molded body and the combination of the depending on fine material and the solvent. You can shorten the rope if you can Diving opportunity a little heated or heated surface-active center clogs

After a long enough dive, the Pönv.kc ^ per dried, i.e. the remaining solvent of removed from the molded body. You get a printing plate with numerous, evenly distributed micropores.

Dk printing plate itself has an excellent Ink absorbency, so that one can achieve clear prints repeatedly without the need for each impression of printing ink must be applied to the printing surface.

The printing plate can of course also be used to manufacture stamp pads.

According to another embodiment of the invention, the mixture of the photopolymerisierfearen liquid polyurethane and the soluble fine powdery material poured into a mold that has cavities. which correspond to the desired letters or numbers. After that, the mold is ready to be manufactured a microporous printing plate treated in the manner described above.

A variant of this design is described below. This variant is advantageous because the microporous molded body not onto the substrate need to be glued. The mixture of the photopolymerizable liquid polyurethane and the soluble fine powdery material is poured into a mold that has two translucent sides and on this is irradiated. On one side of the form, light comes off certain parts of the surface kept away. The other side is irradiated over its entire surface with light to such an extent that the light does not penetrate to the opposite side of the liquid mixture poured into the mold. Man In this way, a molded body is obtained that has a closed curses on one side and on the other the other side has a surface formed with depressions or elevations and a porous pressure plate represents, which is integrally formed with the above-described molded bodies made of resin, which the / u correspond to the characters to be printed.

Another variant of the same embodiment leads to the same product as the one described first Variant. The one made up of the photopolymerizable liquid polyurethane and the soluble, fine-powdered Mixture of material is poured into a mold to form a relatively thin layer. That in the Mold poured, liquid mixture is irradiated on its entire surface with light, so that the liquid Polyurethane photopolymerizes into a relatively thin, solid product. Then there is another Amount of the liquid mixture poured and this further amount for photopolymerization with light irradiated, the light being kept away from certain parts of the surface of the liquid mixture.

This method has the advantage that the microporous Moldings do not need to be glued to a substrate and the process does so with molds can be carried out that are difficult to irradiate from two sides.

In all of the above-mentioned embodiments, the liquid mixture can also be directly around a Wave around or onto another suitable trilger

pour so that the solid resin directly on the shaft or the other carrier is cast and the microporous printing plate od. The like. Not glued or on needs to be assembled in another way. Such products can be used directly as a printing cylinder or Inking roller can be used.

The subject of the invention is hereinafter referred to Hand illustrated by examples

example 1

In a mixing vessel, 200 percent by weight of saline pjiver passed through a 200 mesh sieve passed through, and 100 parts by weight of a photopolymerizable liquid polyurethane, viscosity 30 P, mixed, stirring with a high-speed stirrer. After a homogeneous mixture was made, it was left in the jar for about 60 minutes left to stand so that the foam formed on stirring was destroyed.

The mixture was poured onto a mold made of transparent glass on which a square frame made of the same material and having a thickness of 10 mm was placed. The surface of the liquid mixture poured into the mold was covered with a protective plate made of clear glass. The liquid mixture was then irradiated through the upper and lower glass plates for 10 minutes with ultraviolet light having a wavelength of 300 to 400 μm , which was generated by ultraviolet lamps which were arranged at a distance of 5 cm from the plates. As a result of the irradiation, the liquid polyurethane photopolymerized to form a solid plate.

This solid plate, containing saline powder, was taken out of the mold and placed in. For 24 hours Immersed in water so that the salt powder contained in the plate was dissolved. After that the plate air dried. A microporous plate was obtained in which numerous micropores were uniformly distributed was.

To produce a printing plate, the plate obtained was cut to the desired format and letters were carved out on one side. This printing plate could do 10% more ink absorb than the usual printing plates made of porous materials produced with the aid of a propellant. Even after a continuous printing test with more than a thousand impressions, the letters only showed one little wear and tear and clear impressions were obtained.

Example 2

In a mixing vessel, 300 parts by weight of sodium nitrate powder passed through a 200 mesh passed through, with 100 parts by weight of the photopolymerizable, liquid polyurethane, viscosity 14 P, mixed. It was stirred with a high-speed stirrer. After a homogeneous mixture had formed, it was evacuated in a vacuum vessel so that the foam formed by stirring was destroyed.

The liquid mixture was poured into a mold consisting of a jacket with an inner diameter of 20 mm and a height of 50 mm and a base plate made of stainless steel and in the middle contained a wave. The surface of the mixture poured into the mold was covered with a polyester film covered.

The mold filled with the mixture was mounted on a turntable which was rotated at 3 rpm. The mixture was irradiated for about IC min with ultraviolet light with a wavelength of 300 to 400 μνη with the aid of the UV lamp also used in Example 1, which was arranged at a distance of 5 cm from the cylinder. In this way, the liquid resin was photopolymerized into a solid column with the shaft in the center.

ίο The resulting column of sodium nitrate powder containing solid polyurethane was removed from the mold together with the shaft, for Dissolve the sodium nitrate immersed in a solution of a non-ionic detergent for 8 hours and then dehydrated and dried under the action of pulling force. A microporous column was obtained which possessed numerous, evenly distributed micropores and yes the one wave was arranged centrally.

This product could be used as a paint roller in a ticket machine without further processing will. The roller could absorb 30% more ink than a conventional felt roller. Since the The hardness of the roller made it possible to produce prints that were not smeared by over-inking.

B e i s ρ i e 1 3

In the manner indicated in Example 1, 100 parts by weight of a photopolymerizable, liquid Polyurethane and 300 parts by weight of sodium chloride powder with a grain size below 200 mesh homogeneous mixture produced.

The mixture was poured onto a mold plate made of glass on which a square frame 5 mm thick and made of the same material was placed. The upper surface of the liquid mixture poured into the mold was covered with a negative film on which the letter S was depicted so that the film touched the liquid surface directly and prevented air from entering it. The liquid mixture was then irradiated for 10 minutes with ultraviolet light at a wavelength of 300 to 400 μπ \ , with the aid of the ultraviolet lamp also used in Example 1, which was arranged 5 cm above the negative film.

As a result, the liquid polyurethane photopolymerized under the image of the letter S on the Negative film to form a molded body.

This molded body, which contained sodium chloride powder, was taken out of the mold and removed from the protective negative film separated. The molded body was then immersed in water for 6 hours, with unpolymerized liquid polyurethane drained and the salt dissolved. Thereafter, the molded body was air dried. A microporous shaped body was obtained which had the shape of a letter and in which numerous micropores were evenly distributed.

The letter body thus obtained was placed on a pad made of sponge rubber and then mounted on a holder. In this way, a microporous printing plate was prepared. Compared to conventional printing plates made of porous materials that have been produced with the help of propellants the pressure plate was only a little higher

6; Ink absorbency. It was found However, after a long-term test with over ten thousand impressions, there was almost no wear and tear on the body of the letter, and even after that the prints were still clear.

Example 4

In the manner indicated in Example 2, 100 parts by weight of a photopolymerizable liquid Polyurethane and 300 parts by weight of sodium nitrate powder under 200 mesh a homogeneous mixture manufactured.

The liquid mixture was poured onto a 3 mm thick sponge rubber mat placed at the bottom of the cavity of a stainless steel mold. The upper surface of the liquid mixture poured into the mold was covered with a negative film on which a specific address was depicted. A transparent glass plate was placed between the liquid poured into the mold and the negative film. The cast mixture was then irradiated for about 10 minutes in the manner specified in Example 3 with ultraviolet light with a wavelength of 300 to 400 μνη, so that the liquid polyurethane under the image of the address photopolymerized to form molded bodies which adhered to the sponge rubber layer.

These solid molded articles containing sodium nitrate powder were made together with the sponge rubber mat removed from the stainless steel mold and placed in a for 8 hours Immersed solution of a nonionic detergent, the non-polymerized liquid polyurethane expired and the sodium nitrate powder was dissolved. Thereafter, the assembly was washed and dried. A microporous letter body suitable for printing addresses on a Sponge rubber mat received.

The microporous letter body had a 10% higher ink absorbency than that conventional blocks made of porous materials produced with the aid of a propellant. Even after one A long-term test with over a thousand impressions showed only minor wear and tear on the body of the letter and clear prints were still obtained.

Example 5

In the manner indicated in Example 1, 100 parts by weight of a photopolymerizable liquid Polyurethane and 300 parts by weight of sodium chloride powder under 200 mesh produced a homogeneous mixture.

The liquid mixture was poured onto a mold plate made of transparent glass with a square frame made of the same material and 3 mm thick. The upper surface of the mixture poured into the mold was covered with a transparent glass plate and thereby protected from the ingress of air. The liquid mixture was irradiated for about 8 minutes through the upper and lower glass plate in the manner indicated in Example 1 with ultraviolet light with a wavelength of 300 to 400 μm , so that the liquid polyurethane photopolymerized to form a solid plate.

Then the protective upper glass plate was removed and another amount of the liquid mixture consisting of the photopolymerizable liquid polyurethane and the common salt powder was poured onto the solid plate to a thickness of 3 mm. The liquid mixture poured into the mold was covered with the glass plate again. A negative film on which a certain name was depicted was placed on top of this. The second amount of the liquid mixture poured into the mold was irradiated for about 7 minutes through the negative film with ultraviolet light having the wavelength indicated above, so that the liquid polyurethane under the letters of the name on the negative film to the shape of the letters corresponding bodies of solid Polyurethane photopolymerized.
This item was made from solid polyurethane

ίο removed from the stainless steel mold, removed from the protective glass plate and immersed in water for 24 hours so that unpolymerized liquid resin drained and the saline powder was dissolved. Thereafter, the molded body was dried. A microporous name printing plate was obtained on which the letters of the name were raised were arranged. The plate had numerous, evenly distributed micropores. The ink absorption capacity of the name printing plate was about 10% higher than that of a conventional one Plate made of porous materials produced with the aid of a propellant. Even after a long attempt with thousands of impressions there was little wear and tear on the letter bodies still received clear impressions.

Example 6

In the manner used in Example 1, 100 parts by weight of a photopolymerizable liquid gene polyurethane and 300 parts by weight of sodium chloride powder under 100 mesh produced a homogeneous mixture. A mold was constructed consisting of a standing cylinder made of clear synthetic resin, mil an inner diameter of 20 mm and a height of 50 mm and a rubber roller of 10 mm Diameter, which had a shaft and was located in the center of the cylinder, and a bottom plate stainless steel.

The liquid mixture was poured into the 5 mm wide annular cylindrical space of the mold. The top of the cylinder was covered with a polyester film. Around the perimeter of the resin cylinder! a negative film was put around, which was provided with a certain image. The mold filled with the liquid mixture was mounted on a turntable which was rotated at 3 rpm. There; poured liquid mixture was irradiated in the manner given in Example Ί for 10 minutes with ultraviolet with a wavelength of 300 to 400 μτη , se that the liquid polyurethane was photopolymerized to a solid polyurethane column, which on its periphery with a letter body and in the middle it was provided with a rubber roller with a shaft.

The column was removed from the mold and immersed in a solution of a nonionic egg for 8 hours Dipped in detergent. The non-polymerized liquid polyurethane ran off and became the sodium Ni dissolved kicking powder. The column was then dewatered and dried under the action of centrifugal force. May received in this way a printing cylinder with a rubber roller on the microporous letter body were arranged.

When using the cylinder in an automat!

see stamp machine were as a result of the appropriate! Hardness of the rollers not smeared by over-dyeing Get prints.

509584/4:

Claims (1)

Claim: 23 Process for the production of a microporous printing plate, characterized in that by mixing a photopolymerizable, liquid polyurethane with a viscosity of 1 to 100 P at 25 ° C with finely powdered table salt, sodium nitrate, sugar, tartaric acid or dextrin in a mixing ratio of polyurethane to finely powdered material of 1: 2.5 to 1: 5, based on the weight, a homogeneous mixture is produced, this liquid mixture is poured into a mold with a suitable shape, the mixture poured into the mold is irradiated with light with a wavelength of 300 to 400 μπ \ is to photopolymerize the liquid polyurethane to a solid molded body, the light used for the irradiation can be kept away from certain parts of the surface of the mixture poured into the mold, the molded body is removed from the mold and, if necessary, the liquid mixture is allowed to run off, then the shaped body is immersed in water in order to f to dissolve and remove a powdery material in the shaped body, and the resulting microporous shaped body is dried.