DE2143950B2 - Process for the production of double-coated paper - Google Patents

Description

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The invention relates to a method of manufacture of double-coated paper, in which the paper coated on the inside with clay is passed through a calender and then on the smoothed »in-coated side containing a microcapsules Emulsion is applied.

One such method is known from U.S. Patent 34X52oy known. According to this patent specification the emulsion containing microcapsules is applied with a roller which is roughened Has flexible covering and when applying the emulsion against the previously smoothed paper web presses and roughening them (see in particular column 4, lines 20 to 41). The emulsion to be applied is from a nozzle or the like (cf. in particular Fig. 2) into the gusset between the application roller and the paper web sprayed (column 2, lines 24 2 (->). what an independent Requires control of the amount of emulsion fed. Since the paper surface in the Application of the emulsion necessarily roughened, but aiming for a smooth paper surface the bumps must then be removed again. The object of the invention is this to avoid additional work. According to the invention the object is achieved in that the Emulsion from a bath using a 3-roller system is transferred to the paper strand.

With the present invention it succeeds without anything new Roughening the previously smoothed paper surface to apply the required amount of emulsion, there is no need for independent control of the amount of emulsion fed. When according to the invention provided 3-roller system, the measuring roller automatically regulates the amount of emulsion that is released the bath is transferred to the paper web via the take-up and delivery roller. Since the invention Process does not necessarily have to be roughened to the required paper surface Applying the amount of emulsion also means that no subsequent smoothing of the paper surface is necessary; according to the invention, only the emulsion layer is smoothed and dried.

Further advantages and possible uses of the invention.

ua / v patents 2299693,2374862, 254KJon, 2712507, 2730456, 2730457, 2800457, 2929736, 2932582, 3020171, 3104980 and 3 129 103, a copying process is described in which separate layers are provided on a suitable support, one of the layers contains a liquid active ingredient, e.g. B. a colorless dye component in a liquid solvent is dissolved and enclosed in microscopic capsules evenly distributed in the ao layer is. This layer will hereinafter be referred to as the emulsion layer. The other Layer consists of clay or some other specific substance that can react with the liquid, a5 when it emerges from the capsules to a colored Create image> j. This layer is described below referred to as the clay layer. When the emulsion layer containing the encapsulated liquid in Surface contact with the clay layer is placed, color is only developed when using a pencil. Pencil. Stylus. Typewriter type lever, embossing plate impression or the like. Pressure is exerted, or when the capsules in the image areas are broken by heat. The liquid then emerges from the broken capsules and wets the adjacent absorbent material in the clay layer to develop an image.

In a multiplication record, the cover sheet of the set is made so that it is coated with the emulsion layer only on its underside. while the base sheet of the sentence is only provided with a layer of clay on its upper side. All intervening sheets are coated on the underside with an emulsion layer and on the () top side provided with a layer of clay and thus form sheets coated on both sides.

Because the emulsion layer contains more expensive materials and therefore represents the more complex coating, it is desirable to produce the clay layer with a high degree of surface smoothness in order to achieve this way of achieving more effective contact with the emulsion layer.i and as much as possible of of the encapsulated liquid dispensed from the coating. on Reason of the matter that the emulsion layer is sensitive is against pressure. to break the capsules prematurely, it was customary to use the paper first to coat with the clay layer, which can be calendered to the coating before Smooth application of the emulsion layer.

The emulsion layer consists of an aqueous mixture, the breakable microscopic capsules from tanned gelatin, which contains a liquid, color-forming substance, such as. B. in an organic solution

forming substance, such as / .. B. colorless dye dissolved in a solvent. A considerable amount (up to 50 percent by weight of the capsules) of coarse particulate solid can also be present in the emulsion layer mixture

be included, such as B. with the fragile capsules floating cellulose fibers. In the aqueous medium there can also be a small amount of water-soluble Binder be loosened. For a more detailed description of the emulsion layer, refer to U.S. Pat. No. 2,711,375 and others of the patents already referenced.

The clay layer contains in a finely divided suspension z. B. attapulgite clay or special kaolin clay with or without other fillers, e.g. B. calcium carbonate, silica gel, Satin white and the like and a small amount of resin binders.

For the production of double-coated intermediate sheets the raw paper supply is supplied in the form of rolls 10, which can be rotated on one on one Unwind stand 14 mounted spindle 12 are mounted. The strand 16 of the Rohvorratspajriers is from the roller 10 via a series of idler rollers and guide rollers 18 to a first coating station 20 headed.

The first coating station includes a delivery roll 22 in circumferential contact first with the take-up roll 24 and then with the measuring roller 26. The lower part of the take-up roller 24 is immersed in a bath with a clay layer mix to pick up a layer of clay coating, part of which is passed on to form a layer on the peripheral surface of the discharge roller 22. Bev ir die Delivery roller 22 detects the underside of the paper strand 16, it is taken along by the measuring roller 26, which smooths the clay layer and measures the layer before contact with the paper takes place. The delivery roller 22 then grasps the bottom side of the paper strand 16 while it is between the guide rollers 30 and 32 passes through. A measured amount of aqueous clay layer mixture is applied to the soil side of the paper strand applied in an amount of about (1.5 to 1 kilograms per 100nv Paper surface.

From the first coating station 20, the now one-sided coated paper strand is pulled directly to the air knife 34, which works with a guide roller 36 to measure the coating on the surface of the paper and to distribute the coating mixture evenly on the surface. The coated strand becomes while still wet from the clay layer mixture. by the air knife to a portion 42 of a drying oven which is maintained at a temperature of about 105 ° C to 150 "C ¹ while the strand is carried on an endless conveyor belt 44. The upper run of the conveyor belt is held by rollers 46 and guided through the dryer on a curved path. It is advantageous to use a perforated belt or a conveyor belt made of a vapor permeable material to allow the water vapor to escape as it is released from the coating. The endless conveyor belt 44 is looped around rollers 48 and 50 outside of the dryer while the return path is through the dryer again to maintain the temperature with the conveyor belt being held on rollers 52 near the floor. A pick-up roller 54 is used to maintain the correct edge tension. For a detailed description of the drying system, reference is made to U.S. Patent 3 311 4 ^l ) y.

Before applying the emulsion layer with encapsulated material, it is now clay-coated on one side Paper strips guided in quick succession through the rollers of a calender, in the drawing as a 5-roll calender 61 with hard steel rolls is shown.

Calendering improves the smoothness and increases the resistance to distortion when settling and also reduces the porosity of the paper, which also results in a capsule coating with less expensive capsule coating material

ίο gets by. This not only gives a clear result Cost savings, but a wetting is limited to the surface, rather than that one Penetration occurs, resulting in a higher speed is achieved with less curl in the double-coated duplicating sheet. The clay coated paper 16 is then left with the dried clay coating 60 on top from the calender 61 via a series of guide and tension rollers 62 to a second coating

ao station 64, where the emulsion layer is applied. This second coating station is of the same construction as the first, it consists of a discharge roller / e 66 in contact with the uncoated side of the paper strand 16, one

as measuring roller 72 and a take-up roller 74, the lower part of which is immersed in a pan 76 with the emulsion mixture. The mixture is transferred from the beginning of the take-up roller to the circumference of the delivery roller, and the amount applied by the delivery roller is measured by the measuring roller of the 3-roller transition already described. Application occurs while the strand is held between guide rollers 68 and 70. Approximately 0.5 l-> is 0.7 kg per 10 (1 m ^{: are} attached.

In front of the coating station 64, the coated strand becomes a / wide air knife via a roller 80 48, which in turn measures the amount of coating mixture that is on the strand can remain, and the mixture is evenly distributed over the strand. Behind the air knife is the clay-coated surface is captured by one or more rollers 82 to cover the coating by reverse roller technology to smooth. Although such backward rollers ensure the improvement of the smoothness of the Coating, however, they are not essential in themselves for the emulsion layer. Of the smoothing rollers 82, the one is now coated on both sides Strips passed around roller 80, around the dry layer down and the moist emulsion layer to the top, and then pulled through a suction zone 84 to an upper part 86 of the drying oven, where it is carried on the surface of another endless conveyor belt 83. The upper run of the conveyor belt is carried out by longitudinally separated transversely extending rollers 90 is guided through the dryer in a curved path and the conveyor belt also supports the strip on a short distance after the exit of the dryer, causing the conveyor belt to go down is fed back through the furnace on rollers. A roller 92 is outside the dryer for adjustment the conveyor belt tension provided. Here, too, a vapor-permeable conveyor belt is useful.

The strand 16, on one side with a dried emulsion layer 60 and on the opposite Side coated with a dried clay layer 94 is then over a series

guided by guide and tension rollers 96 to a winding roller 98, which is on a winding stand 100 is mounted and winds up the coated strand. The strand is thus made by the layering device and drawn through the dryer under tension supplied by the take-up roll will.

Even with the conventional method, the coatings were applied in the same order, namely first application of the clay layer and then the emulsion layer, but the coatings were in different work steps on different machines with different calenders and another machine in between. Such a three-part one Procedure requires significantly more investment capital, space and manpower, and the non-integrated Arrangement creates difficulties with transportation and with the schedule, which is quick and easy interfere with economical production of duplicating sheets.

Efforts have been made to unite the work steps on the coating machine only to summarize by first applying the emulsion layer and then the clay layer was with the possible omission of the calender, but certain advantages in terms of quality and the mode of action is achieved when the sequence is reversed and that which takes place in the operation Calendering is applied immediately prior to emulsion coating.

In terms of economy, the capsule mute coating is the more complex coating It is therefore desirable to achieve the highest possible surface smoothness during use To obtain clay layer so as to have the closest possible contact between the emulsion layer and the clay layer to achieve in the copier system. This will allow the encapsulated liquid to exit from it the capsules are best exploited.

Furthermore, in terms of economy, it was found that when coated with clay Rope of paper in the manner described immediately before the paper is moistened with the aqueous Emulsion coating is calendered, the amount of emulsion coating that is applied to the paper is reduced and the cost can be further reduced without affecting the mode of operation suffers.

In terms of performance, it has been found that improved smoothness and reduced porosity is obtained even if the coated sheet is re-coated with the aqueous emulsion layer is soaked because the aqueous emulsion layer penetrates less deeply into the base paper. Therefore, less has to be Moisture is driven out of the paper, causing higher speeds in the Manufacture with less risk of wrinkles or puckers in the dried sheet is achieved.

Obviously, the procedure described represents the the simultaneous layering, the 3-roll measuring and the high-speed drying in one continuous Work step on a single machine combines fewer requirements for previous ones or downstream processing equipment, improves quality, significantly reduces labor costs, Greatly improves the raw material utilization and also produces a better and more uniform one Product.

The described tandem process produces a double-coated paper of better quality, better copy quality, improved resistance to contamination due to the smoothness of the Clay coating, improved character clarity through Elimination of a layer structure, minimal or no curling, less paper distortion - and all of this with low material costs and less waste.

1 sheet of drawings

Claims (3)

Patent claims: 1. Method of making double coated Paper in which the paper coated on one side with clay is guided through a calender and then on the smoothed uncoated Side an emulsion containing microcapsules is applied, characterized in that that the emulsion is transferred from a bath to the paper strand by means of a 3-roller system will. 2. The method according to claim 1, characterized in that that as a 3-roller system, a combination of take-up, measuring and delivery roller is used. 3. The method according to claim 1, characterized in that with the 3-roll system per 100 nv paper surface 0.5 to 0.7 kg emulsion be applied. It shows u a schematic side view of a, gs machine according to the present invention