FI113286B - Paper machine for making soft crepe paper with high bulk - Google Patents

Abstract

A paper machine for the manufacture of a soft crepe paper grade, which in respect of bulk and softness is fully comparable to the one manufactured in a paper machine made for through-air drying by hot air, is in principle a conventional soft crepe paper machine, in which a conveying and imprinting fabric (25) is substituted for the pick-up felt. A pick-up device (23) operating with air flow picks up the web (15) from the forming fabric (9) and transfers it to the imprinting fabric (25) without any appreciable compaction of the web (15). The imprinting fabric (25) is maintained clean and dry by cleaning devices (41, 43, 45) and a device (47) for depleting the imprinting fabric (25) of water before it arrives at the pick-up device (23). Further, air current generating devices (35, 37, 39) are provided for removing water from the paper web (15) by passing air of ambient temperature through the web (15). These have a capacity that is sufficient for raising the dry solids content of the web to at least 25 % before the web arrives at the Yankee dryer (29). If desired, the paper machine may easily and in a short time be converted into a conventional soft crepe paper machine, essentially by substituting a pick-up felt for the imprinting fabric (25).

Description

113286

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a paper machine for the production of soft crepe paper as defined in the preamble of claim 1.

10 Prior Art

Conventional paper machines for soft crepe paper of the above type are widely known, cf. e.g., U.S. Patent 4,055,461. The soft crepe paper produced in such machines has certain limited values for sweat and softness. To achieve bulk and / or softness values above these limited values, special methods have been used, such as mixing in expandable microspheres of thermoplastics, as disclosed in U.S. Patent 4,619,734, or using machines that run through air drying by hot air, cf. e.g., U.S. Patents 3,303,576, 3,812,000, and 4,036,684, wherein the through-air drying is performed with »* * · ,,, · 20 cylinders with a tear-off jacket, which can be coated, e.g. * · Is fed internally and passes through the jacket or vice versa.

• ♦ • 4 · • · <· 'Known conventional paper machines for crepe paper which are

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'· *' Of twin wire, flat wire or chest roll types, however, are designed so that they cannot be easily converted to various functional structures to enable it,. . that can be made of soft crepe paper with a sweat and softness

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»· ',,! the requirements are considerably different.

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DESCRIPTION OF THE INVENTION> '30' 1, ': It is an object of the invention to eliminate the above problem and to provide. * a paper machine for soft crepe paper that can be converted in a simple way 2 113286 to suit the changing conditions on the market, such as actual competition and consumer expectations.

This object is achieved by the paper machine fulfilling the features of the characterizing part of claim 1.

Brief description of the drawings

The invention will be described in more detail below with reference to the drawings in which 10

Figure 1 schematically illustrates a preferred embodiment of a papermaking machine according to the invention for producing soft crepe paper.

Figure 2 schematically illustrates a portion of the paper machine of Figure 1, which paper machine 15 is provided with a single felt press which cooperates with a press roll at the Yankee cylinder.

Fig. 3 is a diagram illustrating the relationship between density and basis weight of soft crepe paper made on machines with two types: '; ': 20 functional structures.

> »* * * • t · • · ,,; 'Ways to Implement the Invention ♦ *» · *. '* Figure 1 schematically shows parts of a conventional papermaking machine suitable for making soft crepe paper such as tissue paper and other sanitary paper products. The paper machine shown is a twin-wire machine with a wire section 1, • i *

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press section 3 and drying section 5. The wire section 1 has a head box 7, an endless support or * · inner forming wire loop 9, an endless or outer forming wire loop 11 and * ... forming roll 13 which may have a perforated surface and be equipped with an internal suction device: ; 30 la, or it may alternatively have a flat surface. The headbox 7 feeds a single-ply or multi-ply stock jet into the gap between the two movable forming wires 9,11 to form the paper web 14 by dewatering the stock. Two 3 113286 forming wires pass together through a forming roll 13 and then in individual loops through a plurality of rolls, which are tracked to guide, orient and tighten the supporting or inner forming wire 9 and the covering or outer forming wire in that order. The rolls for the overlay forming wire 11 include a chest roll 17 and a guide roll 19 located a short distance downstream of the forming roll 13 and may be called a swivel roll. The overlay forming fabric 11 may be detached from the support forming fabric 9 and the paper web 15 either immediately before the support forming fabric 9 and the paper web 15 pass from the forming roll 13, or alternatively as needed or preferably at the transfer suction box 21 or other transfer device 10 preferably operated by air flow 13 and swivel roll 19. The support forming fabric 9 passes into the press section 3, where the paper web is moved to the press section 3 by means of a pick-up device 23 contained in the press section.

The press section 3 has an endless looped movable fabric 25 which is a felt in the first functional structure of a papermaking machine, i.e. a fabric provided with a fine fiber surface ("nap") consisting of a natural or synthetic material. The felt 25 is arranged to carry the paper web 15 from the pickup device 23 to a nip; '; the silicon formed between the press roll 27 and the Yankee cylinder 29 contained in: '*': 20 in the drying section 5. The press roll 27 presses the paper web 15 on the yoke surface of the Yankee cylinder 29: * ·. At the same time as the felt 25 and the press roll 27, which is a roller preferably with a tear-off surface in this functional structure of the machine, remove moisture:. 'Of paper. After said nip, felt 25 advances around guide roll 31 and through and through nip 1 formed between the second press roll 33 and the Yankee cylinder 25 29, whereby the felt 25 is pressed once more against the paper web 15 through the hole of any first press roll 27 to remove the pattern caused by the germinated surface.

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* ·; Downstream of the second press roll 33, means are provided for cleaning and stabilizing the felt 25, after which the felt 25 must have a moisture content, ',.,' Suitable for picking up the paper web 15 from the supporting forming wire 9.

30:> en: The Yankee cylinder 29 is covered with a hood (not shown) in which high speed hot air is blown against the paper web 15. The paper web is creped from a Yankee 4113286 cylinder 29 by means of a creping scraper, not shown, to achieve the desired degree of creping, whereby the final creped paper web is rolled in a reel (not shown).

The second functional structure of the papermaking machine is for producing soft crepe paper having higher bulk and softness values than can be achieved in a papermaking machine of the first functional structure. To accomplish this, the felt 25 is replaced by a transport and embossing wire. The use of brand printing fabrics in the manufacture of soft crepe paper, and the operation and benefits achieved by these 10 are well known, cf. e.g., Pulp & Paper, November 1977, Hanson, J.P., "What's Going Into Tissue", pages 93-102, especially pages 98-100 (Never underestimate knuckle power). Further, the airflow generating means 35,37,39 are tracked along at least one support or interior forming fabric 9, and a conveying and embossing fabric 25 to remove water from the paper web 15 by conveying air at ambient temperature to the same. and cleaning means 41,43 and 45 along conveyor and embossing wire 25 for cleaning it to continuously maintain its water and air permeability, and tracking means 47 for emptying the conveying and embossing wire 25. , before the wire 25 arrives at the pickup device 23.

20: ', · The conveyor and embossing fabric 25 can pass through the same rolls as the felt ··· or the guide roll 31 can be passed so that the conveyor and embossing fabric passes * * * *:'; a first press roll 27, which in the second functional structure is preferably a roll having a flat surface, extending along the shell surface of the Yankee cylinder 29 directly to a second press roll 33. In both cases, it is convenient that the second press roll

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; · 33 is released from the press contact with the Yankee cylinder 29 so that the paper web 15 '' is not subjected to another character printing function. The first embossing operation 'is achieved when the first press roll 27 presses the paper web 15 ,, onto the Yankee cylinder 29, whereby the pressing is performed with a force preferably 30 at least 50 kN / m relative to the web width. However, if in another functional: '' '; in the structure, the first press roll 27 is a roll having a perforated surface, such as a suction roll, where it is appropriate to subject the paper web 15 to a second imprinting operation by means of a second press roll 5113286 to remove patterning that may have been caused by

In the case of a paper machine in another functional structure, which is intended to function as intended and produce marketable soft crepe paper grade, it is very important that the conveyor and embossing wire 25 is kept clean and additionally dewatered when it arrives at the pickup device. 23. The cleaning devices 41,43,45 are therefore wider than those required for cleaning and stabilizing the felt in a conventional tissue paper for crepe paper) and include a plurality of oscillating needle jets 41, a plurality of fish tail jets 43, and a plurality of suction boxes 45. When these jets and can of course also be used to clean and standardize the felt, but not all jets and suction boxes are normally used. Two of the fish tail jet tubes 43 are shown to be located and oriented such that a flood nip can be provided at the point where the fabric 25 begins to wrap around the guide roll. The flood nipple is particularly suitable for cleaning and standardizing the felt, but it is also useful for cleaning the transport and embossing fabric 25.

j ' ". The standardized blanket contains an amount of water that facilitates the picking of the paper web 15 from the forming wire 9 ·. In contrast, the transport and embossing fabric 25 is dewatered by dewatering means 47 upstream of the pick-up point. The dewatering means 47 'i * operate suitably by means of a flow of air passing through a conveyor and embossing wire and, in the embodiment shown, is a suction box 47, but it would of course be possible to alternatively use only the blow nozzle or suction box 25 with it. Suction box 47 and at least one suction box 43 can be installed * «·

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Suitably such that they can be easily moved between an active position in which they grip the wire 25 and an inactive position in which they do not grip the wire 25 because> ·; '· · They do not need to be active when wire 25 is a blanket. A number of jet water recovery • · · • ... * devices have been tracked to collect jet water passing through the wire 25 without: ': 30 being sucked into the cleaning simulators 45.

6, 113286

In a conventional paper machine, the pickup device may be a roll or a shoe having a flat surface. To ensure picking without any significant condensation of the paper web in the second functional structure, the pickup device should preferably operate by an air flow passing through forming wire 9, paper web 15, and conveyor and embossing wire 25 and may include a suction device such as a suction roll An even better effect is obtained if the blow nozzle 53 is imaged within the loop of the support forming wire 9 and is oriented with the suction zone of the shoe 51 or roll. The airflow pickup device 23 also functions excellently in the first functional structure 10 in which the fabric 25 is a blanket. In this case, a blow nozzle 53 is not required to ensure that the paper web 15 is picked up from the forming wire 9.

In the second functional structure, at least as much water can be removed from the newly formed wet paper web 15 without significant condensation so that when the paper web is pressed onto the hot jacket surface of the Yankee cylinder 29, no vapor bubbles are formed causing the web 15 to disengage from the 35,37,39 tracked to provide a flow of air at ambient temperature through the paper web 15. 1; In the embodiment, the airflow generating means 35,37,39 comprise two suction boxes 20 35,37 located in the loop of the carrier forming wire 9 between the transfer suction box 21 and the pickup device 23, and the suction box 39 located within the loop of the first and the the number of pressure boxes 35,37,39 and their location between the transfer suction box 21 and the first pressure roller 27 may vary within the scope of the present invention. However, it should be noted that a moist and relatively brittle · '. * Us the crepe paper web 15 does not attach too firmly to the carrier forming fabric 9 or the carrier and embossing fabric 25. If desired, members 55 can be followed to fit:' ·· to apply the release agent to the carrier and embossing fabric 25 to bond to the fabric. can be reduced.Such a body can be illustrated e.g.

30, directly downstream of the suction box 47 on the side of the wire 25, conventional means not shown are also tracked to provide and maintain an optimum and stable 7113286 level of coating on the Yankee Cylinder 29. The natural coating consists essentially of hemicellulose and fibrous particles, but the adhesive and / or release agent may be added to improve the adjustment of the adhesive properties of the coating. The amount of hemicellulose is adjusted by adjusting the pH of the stock to 5, while chemicals can be added to the stock or applied to the formed paper web, or preferably directly to the shell surface of the Yankee cylinder. The bonding of the web to the coating affects all the properties of the paper web, and the coating also affects the wear of the Yankee cylinder surface and the stencil blade.

There is also some water drainage from the paper web due to air flow to the transfer suction box 21 and suction shoe 51. To further improve drainage, a steam box 61 may be provided to directly heat the paper web 15 upstream of the suction box 35 and forming web 9. Heating reduces the viscosity of the water so that it is easier to absorb. In addition, the rate of dewatering is increased by air suction. Of course, it is naturally possible, if desired, to provide a second steam box, not shown, to heat the web 15 directly with steam immediately upstream of the suction box 39 located on the transport and embossing wire 25 ···. inside the loop. In order to protect the paper web 15 from droplets of condensate and; 20 of the possible water splashes, when supported from below the transport and embossing fabric 25: J, the heated canopy or shield element 63 • i · covering the web 15 is disposed above the underside of the transport and embossing fabric 25. The roof element * _ '·: 63 may be provided with channels not shown for conducting hot water or steam; 1 'through it, but it can also be heated in some other way, such as by means of electricity.

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In order to avoid the formation of the above-mentioned vapor bubbles between the paper web 15 and the Yankee cylinder 29, the dry content of the paper web 15 should be at least about 25% when the first press roll 27 presses the web 15 onto the Yankee cylinder 29. Paper web dewatering suction boxes 35,37,39, air flow through web 15 and possible 'direct heating with steam are adjusted to provide the aforementioned dry matter content. Direct heating by steam can be replaced by 8113286 using infrared radiation from, for example, one or more dome-type infrared heaters, not shown, or other devices capable of emitting infrared radiation. Dome-type infrared heaters can also be used to facilitate drying of paper web 15 on Yankee cylinder 29, and Figure 15 illustrates one such infrared dome 65 somewhat downstream of second press roll 33. Compact standard dome with one row of infra-red elements can kW / m of web width.

The paper web 15 usually reaches a dry matter content of about 20-30% already with the forming fabric 9, and the dry matter content is increased by one or more percent along the conveyor and embossing fabric 25. If the dry matter content of the web 15 is to be increased further before the web is pressed onto the Yankee cylinder 29, it is possible to supplement the paper machine with a conventional single-felt press as shown schematically in Figure 2.

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In Fig. 2, a conveying and embossing fabric 25 carrying a paper web 15 from below is passing from below the first press roll 27 to and around the swivel roll 67, from where it passes to the press nip formed by the first press roll 27 and; **. between the Yankee cylinder 29. The press roll 27 forms a conventional monofilament; '; 20, with the reference roll 69 generally referred to as 69, such that the press roll 71 and the endless felt 73 pass through a plurality of rolls 75. The suction box 77 is _ * imbedded inside the loop of the transport and embossing fabric 25 upstream: '· the rotating roller 67 to ensure that the paper web 15 does not pass into the press felt 73, * * * V · but remains attached to the conveyor and embossing fabric 25. 15 solids content max. 5% more • $ 9> · '.

»<1« '·· In the modification of the single felt press of Fig. 2 (not shown), the lower press roll 71 \ is moved from its illustrated clock six position relative to the press roll 27 to the clock' 1, i 30 seven. This makes it possible to omit the swivel roller 67 and the suction box 77 \ it '·. Once the transport and embossing wire 25 supporting the paper web 15 has passed the nip between the press rolls 27,71, it follows the surface of the press roll 27 up to nip 113286 formed by the roll 27 and the Yankee cylinder 29. The press nip formed by the rolls 27,71 at seven positions The paper web 15 is thus not moved to the press felt 73, but instead remains attached to the underside of the transport and embossing wire 25 as the latter moves upwardly on the press roll 27.

In order to avoid unnecessarily overloading the drawing with details which depict conventional devices used solely in paper machines and which do not form any part of the present invention, such details are omitted. Examples of such non-illustrated details include cleaning devices for forming wires 9 and 11 and pressing felt 73, and a circulating water recovery device and device for stretching, orienting and operating various endless fabrics.

Figure 3 is a diagram showing the density as a function of basis weight of soft crepe paper manufactured on the one hand in a conventional paper machine according to a first functional structure and on the other machine after being reinstalled in a second functional structure. The alternative shown in Figure 2; a single felt press was not used. The top line 79 thus relates to soft crepe paper; I20, manufactured in the conventional manner, and downline 81, concerns soft crepe paper made in a rebuilt machine, where the picking felt was replaced with a transport and embossing wire and where the water was removed from the paper web by a racket at ambient temperature. air through the web in an amount sufficient to raise the dry solids content of the paper web to at least 25% before the paper web arrives at the Yankee cylinder. As can be seen from the graph, the latter soft: · 'crepe paper 81 has a density which, at low basis weights, is about half * *' of the density of conventional soft crepe paper, and the percentage difference increases with increasing weight: * · ·. Because the bulk is an inverse density, e.g., 200 kg / m3 corresponds to a swell of 5 dm3 / kg and a density of 80 kg / m3 corresponds to a 12.5 drriVkg of line 81: 1 .: 30 soft crepe paper has twice the bulk at low basis weight with conventional soft crepe paper and the percentage difference of the sweat increases with increasing basis weight.

10 113286

The density of the soft crepe paper made in a conventional through-air dryer using hot air is of the same order of magnitude as that indicated by the lower line 81. Thus, the bulk of the soft crepe papa-5 peril of the underline 81 is completely proportional to the paper grade sweat made in a hot air air dryer. Although the softness has not been measured, it is known that softness increases with the increasing sweat of soft crepe paper. Increased softness is appreciated by consumers, but in some cases can lead to application problems when converting soft crepe paper into hopeful end products.

The conversion construction required to convert a paper machine according to the invention from one functional structure to another consists essentially of changing the picking felt to a conveyor and embossing wire or vice versa. It is further required that certain components, such as the second press roll 33, the dewatering suction box 47, and possibly one suction box 45 of the cleaning means for the transfer and embossing wire 25, be changed from the inactive position to the active position, and other components such as a possible device 55 for applying the release agent to the transport and embossing wire 25, activated or: 'j': 20 deactivated. It is further recommended, but not necessary, that in cases where; The first press roll has a perforated surface, replacing said roll with a flat surface roll. As a result, the time required for conversion work will be reduced. Conversion construction should only take a slightly longer period (about 12 hours V · or less) than is required to replace a picking blanket in a conventional paper machine for soft crepe paper.

The cost of converting an existing old tissue paper machine to a paper machine of the present invention is estimated to be 10% to 20% of the cost of a new through-air dryer. Thus, with respect to the relatively low machine cost 30, the soft crepe paper manufacturer can produce a soft crepe paper grade that is wholly proportional to the crepe paper quality produced on a machine using continuous air drying 11 113286 using hot air. Roughly calculated, production is halved because much of the dewatering is done through ambient temperature airflow, followed by drying on a Yankee cylinder, which requires a significantly lower machine speed, about half the speed of a conventional soft crepe paper machine, but the production cost is when producing it in a through-air dryer. When looking at the cost of a product sold to a consumer, i.e., a paper napkin pack, it is seen that the change from a conventional paper napkin to a large bulk paper napkin produced in a papermaking machine according to the invention enables such savings in the amount of used paper fibers. In addition, the consumer will get a softer and more pleasant product.

The fact that it is possible to produce soft crepe paper in a conventional paper machine for soft crepe paper without the use of picking felt must be considered surprising. It was further surprising that the soft crepe paper quality produced in the machine of the invention would be completely proportional in terms of bulk and softness to the paper quality produced in a paper machine utilizing hot air drying.

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The invention has been described above with reference to a C-wrap type double-wire former, but it can of course also be applied to other formers such as S-wrap double type wire forming machines, flat wire forming machines and vacuum roll forming machines.

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Claims (12)

A paper machine for producing soft crepe paper comprises a wire portion (1) comprising at least one forming wire loop (9) for forming a paper web (15), and a drying portion (5) provided with a yankee cylinder (29). the paper web (15) is dried, the paper machine having a first operating embodiment for producing soft crepe paper having certain values of bulk and softness, in which first operating embodiment a pressing portion (3) located between the wire portion (5) an endless loop of movable blanket (25) arranged to run from a removing member (23) located at a junction between the wire portion (1) and the pressing portion (3) of a pressing roller (27) forming a nip with the yankee cylinder (29), during support. of the paper web (15) on its underside, and wherein the supporting forming wire (9) is arranged to extend to said take-off member (23) in the pressing portion (3) for transferring the shaped paper web (15) to said web oxygen (25), characterized in that the paper machine is designed to be easily convertible between said first operating embodiment and a second operating embodiment for producing soft crepe paper with higher values of bulk and softness relative to the first operating embodiment, in which the second operating embodiment of the press part (3) blanket (25) is replaced by a conveyor and embossing wire loop (25), first airflow generating means (35,37) are provided> # in the supporting forming wire loop (9) before the take-off device (23) and * · * t · 20 other airflow generating means (39) are arranged in the conveying and embossing wire coil (25) between the take-off device (23) and the pressing roller (27) for removing the water from the paper web (15) by flowing at ambient temperature. through the * ♦ * · the woven paper web (15), cleaning means (41,43,45) are arranged along the transport and embossing wire (25) for cleaning the same so that its water and air permeability is continuously maintained, and third air flow generating means (47) are arranged to empty the transport and embossing wire (25) on water: before reaching it. to said take-off device (23). A paper machine according to claim 1, wherein in the first operating embodiment there is provided a second press roller (33), which downstream of the first mentioned press roller (27) in it, forms a second nip with the yankee cylinder ( 29), and the felt after the first mentioned <<I type runs over a guide roller (31) to and through the second nip and is pressed there against the paper web (15), characterized in that in the second operating embodiment the second pressing roller (33), in the case that the first pressing roller (27) has a smooth surface, is raised to press contact with the yankee cylinder (29) so that a second embossing of the paper web (15) is avoided. Paper machine according to claim 1 or 2, characterized by said removing means (23) for penumatically removing said web (15). Paper machine according to claim 3, characterized in that the removing means (23) comprises a suction means (51) located within the transport and embossing wire loop (51) for removing the paper web (15) from the forming wire (9) and transferring the web (15) to the the transport and embossing wire (25) without significant compaction of the web (15). Paper machine according to claim 4, characterized in that the removal means (23) comprises a blow nozzle (53) located inside the forming wire coil (9) opposite to a suction opening arranged in the suction means (51). Paper machine according to any one of claims 1 to 5, characterized in that the air-generating means comprise at least one suction cup (35,37,39). »· R; i 20 »(i : 7. A paper machine according to claim 6, characterized in that an angel cover (61) for heating the moist paper web (15) by means of direct thread is provided immediately • "Il:", * upstream of the suction tray (35) and on it. path-bearing side of the wire (9). »·» I · Paper machine according to any of the preceding claims, characterized in that at least one; (1) IR cover (65) is arranged for IR heating of the paper web (15). A paper machine according to claim 8, characterized in that the IR cap (65) is arranged ": at the yankee cylinder (29) downstream of the pressing roller (27). \: 30 17 113286 Paper machine according to any of claims 1 to 9, characterized in that the pressing roller (27) constitutes a counter roll in a single felt press (69) for further dewatering of the web (15) before the pressing roller (27) presses the web (15) onto the yankee cylinder. (29; Fig. 2). 11. A paper machine according to any one of claims 1 to 10, characterized in that a heating element (63) is provided above the lower portion of the transport and embossing wire coil (63) to protect the paper web (15) from water splashes and condensation drops. A paper machine according to any of claims 1 to 11, characterized by means (53) for applying detergent which reduces adhesion of the web to transport and embossing coils (25). '> · • · I 1 I »· * · f I ·! I »* 1 1 · I ·» I ♦ 2 1 · 1 »» * 1 1 * · • I • · I · t I I 1 * 1 i · I »• f» i>>> t I