WO1990014998A1

WO1990014998A1 - Embossed wrapping paper

Info

Publication number: WO1990014998A1
Application number: PCT/SE1990/000380
Authority: WO
Inventors: Roland Evert LILJA
Original assignee: Mo Och Domsjö Aktiebolag
Priority date: 1989-06-09
Filing date: 1990-05-31
Publication date: 1990-12-13
Also published as: ATE102152T1; SE8902083L; NO914614D0; IE902068L; NO914614L; DE69007105T2; NO178145C; EP0476040A1; ES2049980T3; SE8902083D0; FI98142B; IE63811B1; EP0476040B1; DK0476040T3; FI98142C; SE502689C2; FI915767A0; DE69007105D1; NO178145B

Abstract

Embossed wrapping paper, preferably sack paper, whose embossing pattern shows a plurality of out of the paper plane raised, delimited identical figures: (A) the figures are straight-lined, from each other separated and over the paper plane evenly distributed and provided with three, four or more sides and planar figure surface which is parallel to, and situated at a distance of 0.05-0.40 mm from the surrounding paper surface and with a total figure area that constitutes «40 % of the total paper area that has been embossed, and by that (B) the connection surface between figure surface and surrounding paper surface, substantially is perpendicular to the paper plane.

Description

Embossed wrapping paper

It is earlier known to manufacture sacks of embossed ma¬ terial. This has primarily been done to increase the fric¬ tion between filled sacks which are piled.

The embossing patterns, that hitherto have been used on sacks, have meant that the sack material has shown bosses and, possibly, even recesses, relative to the original plane of the material. The thought has been that, by the piling of filled sacks, the bosses will be locked by the parts not em- bossed (alt. recesses) in the sack lying closest underneath. A classification of embossing patterns earlier used for sacks, is:

(i) raised ridges extending over the width of the paper, forming possibly a checked pattern where only the edges of the chequers are raised. See e.g.

US-A-3.904,465 and 3.283,992 and SE-A-12949/65.

(ii) out from the paper raised, delimited and, more or less large figure areas. See e.g. FR-A-2,353,207 (76 15678), DE-A-34 37 414, US-A-2.917,223. US-A- 3,495.761 and US-A-3,411,698.

(iii) JP-A-112635/1986.

Several of these earlier known embossing patterns have in common, that they show a plurality of, out from the plane of the paper raised, delimited figures, which are identical. It has been found that there is a need for improvements for patterned sack paper, i.a. regarding the friction between sacks which are piled. We have found, that these require¬ ments can be satisfied if the pattern, in addition, shows the following features:

A. the patterns are straight-lined, from each other separated and over the paper plane even distributed and provided with three, four or more sides and planar figure surface which is parallel with and situated at a distance of 0.05-0.40 mm from the sur¬ rounding paper surface and having a total figure area constituting 40% of the total paper area and

B. the connection surface between figure surface and surrounding paper surface is substantially perpen¬ dicular to the paper plane.

The pattern, according to the above, will even obtain a friction increasing effect on wrapping paper when goods, that have been wrapped in the paper, are piled one above the other.

With wrapping paper according to the invention is meant a paper, where the main part of the fibre material (e.g. 70%, w/w) usually originates from a long-fibred wood, such as spruce or pine. The fibre material is usually sulphate pulp and may be bleached or unbleached. Recycled fibres may be present in a greater or lesser extent. Several of the kinds of paper that are referred to, e.g. sack paper, may well be clopacked (creped). Normally, fillers are not pres- ent in the paper, and if they to some degree do, the amount usually is <?10% (w/w), such as (w/w). Among properties that are especially important for sack paper according to the invention, may tensile energy absorption index be men¬ tioned, which, in the longitudinal direction of the paper ought to be 0.4 kJ/kg, and in its cross direction ≥0.3 kJ/kg. The elongation in the longitudinal direction usually is 3*1% (in case of wrapping paper of a somewhat better qual¬ ity ≥2%) and in the cross direction 2.0% (appreciably >3.5%). As upper limits for these four properties, 7 kJ/kg, 6 kJ/kg, 20% respecively 15% are valid. High values of ten¬ sile energy absorption index and elongation indicate high- qualitative products. It can therefore not be excluded, that future development work may lead to, that the upper limits will be exceeded without therefore going beyond what is re¬ garded as sack paper according to the present invention. Values for tensile energy absorption index and elongation shall be determined according to ISO 1924/2-1985(E) .

Henceforth, the terminology longitudinal direction = the machine direction of the paper is current, which, in most cases, also is the main direction of the fibres. Cross di¬ rection is perpendicular to longitudinal direction.

The figures of the embossing patterns may be straight- lined triangles (triangles), quadrangles, pentagons etc., whereby quadrangles are preferred, and especially of the kind in which there are sides parallel in pairs, like in parallelograms, for example of the kind equilateral. Exam¬ ples of preferred quadrangles are rhombs including squares, rectangles and rho boides (= a parallelogram which is neither equilateral or right-angled). Usually, the pattern figures according to the invention show an even-numbered symmetry axis, which, at the most, is four-numbered. In one and the same embossing pattern it is preferred, that all the figures of the pattern are identical, even if, for some pat- terns, may occur, that an improved friction paper to paper is achieved if 2, 3, 4 or more different kinds of figures exist.

The identical figures are evenly distributed over the patterned surface. The meaning of that is that, if a straight line is drawn over the surface of the paper and is allowed to intersect a plurality of figures in the same way, the distance between beside each other lying Identical fig¬ ures that are intersected by the line, always shall be the same. The corresponding distance for other similar lines must not, however, be the same as for the line first men¬ tioned.

The paper according to the invention may, along one or both of its longitudinal sides, have an outer zone lacking the evenly distributed embossing figures. Alternatively, the figures in these zones may be less distinct because they are not raised as much out of the original paper plane as the more central parts, or because the angle between figure plane and the connection surface to the original paper plane is greater"than 90°. Outer zones of this kind are 1-2 dm, if they exist in the wrapping paper.

Normal pattern frequency usually is below 500, such as

2 below 200 identical figures/dm . As an example, 10-100 may

2 be mentioned, such as 20-60 identical figures/dm . The total pattern area is 40% and usually £0.5% (preferably above 1%) of the total pattern area. It has been shown, that very good improvements in the friction paper to paper may be achieved, if the total figure area is below 30%, such as be¬ low 20% or below 10% of the total pattern area. By improved friction properties is meant, that the im¬ provement i_ >1%. such as £5%, relative to corresponding unembossed paper (the friction coefficient for paper to paper measured in any direction) . The way of measuring is given in the. experimental part. If two identical papers according to the invention are placed with their upper sides against each other, substan¬ tially most of the identical figures (£90%) in one of the papers, ought to be placed between corresponding figures in the other paper in that way, that slipping will be made more difficult (the friction will be increased) because the fig¬ ures in one of the papers will hit the corresponding figures in the other. The greatest distance between two sides in one and the same figure shall, therefore, in many of the most preferred embodiments, be longer than the shortest distance to the closest lying figure in the same paper. The mentioned longest distance always is a distance corner-to-corner, which in a right-angled triangle always is a side and in a right-angled polygon, always a diagonal.

The orientation of the pattern figures shall preferably be of that kind, that the machine direction of the paper di¬ vides an angle in the figures in substantially two (+/- 10°) equally large angles. If an acute angle exists in the fig¬ ures it is preferably such a one that is divided.

In the most preferred embodiment the figures consist of parallelogram. These are shown in figure A and can be defined by the help of a checked pattern, which arises if a first number of parallel, straight lines 1,. 1₂ l3_....ln are intersected by a second number of parallel, straight lines 1' , 1' 1' ...1' at an angle 3 . The lines extend over the width of the paper, n and n are integers which may be even or uneven and are always greater than 10. The exact number of lines is determined by the distance between them, their slope in relation to the width and the width of the sack paper. The perpendicular distance between the lines in one group are alternating, and is

and ^λ2 = a. and between 1 ¹ , and l¹ '2 " ^C' and = b. 1 '2 ^and 1 '3 " ^d' and = a. 1 ^• ₃ and 1 - c. and = b 1 '4 _A and 1 '₅ = d,

1n-1, and 1n = a or _^■•n-1, and 1'n = c b for n = even resp. or d for n = an even uneven integer. resp. uneven integer In general it is valid that the distances a, b, c and d 5 cm, preferably -$:3 cm, and that a b , and c _; d. In one important embodiment is a = c and b = d, with preference that a at the same time is <? b. The figures of the pattern are defined as the whole checked pattern minus the area between lines present at the distances b and d from each other. The most studied embodiments of the invention, on the priority day of the application, have a, b, c and d always been > 0.05 cm, such as > 0.1 cm.

The angle y fulfills the condition 10° _/6 -ζ. 170°, such as 10° ζ /5 90° or 90° ^ . ^ 170°.

It is preferred that the lines 1- , 1 , 1 1 have a positive slope and that the lines 1', -L. I¹ _t-. l'

...1 have a negative slope compared with the machine di- rection of the paper. The angle β is readily divided in half by the machine direction.

The Figures 1-6 show examples of patterns in question seen from above. The machine direction of the papers is in¬ dicated with a double-arrow [<-->].

Figure 1 shows a paper according to the invention where a=c b=d. The angle yβ is 60° and the figure frequency is 39

2 pieces/dm . The symmetry axis is two-numbered. The machine direction divides the angle /3 in half.

Figure 2 shows a paper patterned in a similar manner. a=c b=d. The angle /& is 30° and is divided in half by the

2 machine direction. The figure frequency is 28 pieces/dm .

The symmetry axis of the figures is two-numbered.

Figure 3 also shows a paper according to the invention, where a=c^b=d. The angle β is 30° and is divided in half by the machine direction. The symmetry axis of the pattern is

2 two-numbered. The figure frequency is 48 pieces/dm .

Figure 4 shows a paper where a=c_:b=d. The angle & is

90° and is divided by the machine direction in one angle which is 0° and one which is 90°. The symmetry axis is four-

2 numbered. The figure frequency is 49 pieces/dm .

Figure 5 shows a paper whose pattern is rather like the one in the preceding figure, but whith smaller squares and greater figure frequency.

Figure 6 shows a paper according to the invention where a c .d 4b . The angle fl is 90° and is divided in half by the machine direction. The symmetry axis of the figures is

2 two-numbered. The figure frequency is 32 pieces/dm .

Manufacturing the paper of the invention and apparatus to be used by the manufacturing.

One aspect of the invention is a method for manufactur¬ ing a wrapping paper, preferably sack paper, containing the pattern defined above, by way of embossing a web of sack paper. The paper web as such is manufactured in a way for wrapping paper known per se, and means in the preferred em¬ bodiments of the invention a clopacking stage. The embossing is carried out by allowing the paper web, after a possibly clopacking, pass through a roll nip, where one of the rolls is softer than the other (pressing- respectively embossing roll).

The harder of the rolls (the embossing roll) has an en¬ velope surface which suitably is made of metal (e.g. steel or cast iron) or another hard material. Its envelope surface shows for the wrapping paper of the invention said pattern provided with evenly distributed, raised and identical fig¬ ures with differences which are due to that the envelope surface not is made of paper. Starting from the earlier men¬ tioned description of the pattern of the paper, thus what applies is, that "paper" shall be substituted with "envelope" alternatively with "envelope surface" and "the machine direction of the wrapping paper" with "the tangen¬ tial direction of movement of the envelope surface when the roll is rotating around its axle". As a rule, the raise of the figures shall be somewhat larger than the corresponding raise in the embossed paper. The interval, which usually is suitable for the roll, therefore is 0.06-0.45 mm instead of 0.05-0.40 mm that is applied for the paper. The roll may well be constructed so it can be heated, in order that the paper will dry as fast as possible after the embossing. The paper will partly then more easily lift from the roll and the embossing pattern will partly be freezed more effective¬ ly, which, at the same time, makes it more stable. The best, therefore, is if the roll is constructed in a usual way as a drying cylinder in a paper machine, i.e. hollow with an in¬ let for hot steam (approx. 125-190°C) and outlet for conden¬ sate and so-called "spoiler bars" to improve the withdrawal of condensate and to create turbulence in the condensate film which is obtained on the inner walls of the cylinder. The roll is suitably made from a roll provided with a smooth envelope surface by brooching out recesses corresponding to the surface between lines with the distances b and d between each other (see the above). The depth of the recesses lies in the above mentioned interval.

The pressing roll is made of elastic material which per¬ mits that the figures of the embossing roll can be complete¬ ly impacted in the material when the rolls are pressed against each other. An excellent material is rubber, e.g. hard rubber. The pressing roll is suitably cambered to per- mit an even line pressure along itself during the embossing.

2 A suitable embossing pressure (kp/cm ) depends on fac¬ tors such as the raise of the figures out of the envelope surface, the hardness of the pressing roll, the thickness of the paper, choice of fibre material, speed in the head box

2 etc. Suitably, the embossing pressure is 1-10 kp/cm . In order to obtain an effective embossing, which results in a stable pattern, the embossing most suitably should be carried out at a dry solids content of 60-80%, preferably

65-70% (w/w). After the embossing the paper is dried to a dry solids content of above 90% (w/w).

The sack of the invention and the manufacturing thereof

One aspect of the invention is a sack, which surface wholly or partially shows the embossing pattern mentioned above. The sack material may wholly or partially be made of plastic or paper. The pattern consists of a plurality of out of the surface of the sack raised, delimited patterns which are identical. Characterizing features are;

A. the patterns are straight-lined, from each other sepa¬ rated and evenly distributed over the patterned surface and are provided with three, four or more sides and a planar figure surface which is parallel with, and situ¬ ated at a distance of 0.05-0.40 mm from the surrounding sack surface and with a total figure area that consti¬ tutes <<40 of the total paper area and

B. the connection surface between figure surface and the surrounding sack surface, is substantially perpendicular to the sack surface.

Otherwise, the same is valid for the sack as for the em¬ bossing pattern of the paper with regard to that the em¬ bossed surface does not need to be made of paper. In the case that the embossed surface does not have any machine di¬ rection, with the machine direction of the paper is meant the height direction of the sack. If only parts of the sack surface are covered with the embossing pattern, it is suit¬ ably on the upper or lower side of the sack, i.e. those sides of the sack that by piling lies against other sacks. The sack according to the invention is constructed in a manner known for sacks per se, in which the sack material may consist of one to six different layers, so called sheets, in which the outermost sheet, according to the in¬ vention, preferably is made of paper. The embossing pattern is situated on the outer layer or, as an alternative, is glued on in the form of embossed sheet of plastic or paper.

By the manufacturing of sacks, one is starting from one or more rolls of web formed sack material, which are just as broad as the circumference of the sack including that part (for example paste joints) which shall be used to form the web material into a longitudinal tube. For each sheet a roll is used, by which that web material which shall be in the outside of the sack (outer web) shall be embossed with any of the patterns given above, or if it is not, it is moisten¬ ed, embossed and dried in connection to the unwinding. The different webs of material are stored, by the unwinding, continuously one upon the other, whereafter the in that way obtained, possibly multiple sheeted web material, continu¬ ously is formed and joined together (pasted together) into a tube. This is later cut into suitable sack lengths, where- after one of the ends of the respective lengths, is joined together to form the bottom of the sack. Alternatively, the web material is cut to sack length, which therafter is join¬ ed together into a tube and is sealed in one end.

The different aspects of the invention are also made clear in the patent claims which are a part of the descrip¬ tion. Experimental part

1. Abstract

Sack paper, taken from the paper machine at a dry solids content of approx. 65%, has been embossed in a laboratory press under conditions intended, as far as possible, to be equal to embossing in the paper machine.

The static friction paper to paper of the embossed papers, tensile strength, flexure, tensile energy absorp¬ tion, and air resistance were tested.

The friction increases while the tensile energy absorp- tion decreases and the air resistance increases by the em¬ bossing of the sack paper. According to the test result, re¬ commended are the patterns D, large squares, B, oblong sparse rhombes, C, oblong dense rhombes and oblong rectan¬ gles in now said order.

2. Putting into practise

2.a Embossing

Paper in the form of sheets were taken out from the paper machine at a dry solids content of approx. 65% during change of quality. The sheets were stored in plastic bags in order to prevent drying until the embossing had been carried out.

The paper sheets were embossed under static conditions in a laboratory press by the help of a steel plate provided with a desired pattern. Patterns that were studied, are evi- dent from the figures 1-6. The embossing was carried out at

2 the pressure 3 kp/cm during the times 1 s and 5 s. The sheets were thereafter dried against a drying cylin¬ der between two rigid sheets of blotting-paper, in that way, that they were kept stretched.

2.b Tensile strength, extension, tensile energy absorption were determined according to ISO 1924/2-1985 (E) and air re¬ sistance according to ISO 3687-1976.

2.c Determination of friction coefficient

This was carried out according to TAPPI T:503, by means of an inclined plane from Buchel van der Korpat, Holland. The friction, overside against overside, was determined between two strips that had been cut out of the conditioned sheets in their longitudinal respectively their cross direc¬ tion. The tests were repeated five times for each pattern. The mean value [Mv] of the obtained friction coefficients is evident from Table 1. By cutting the strips in other direc¬ tions and/or to match them together in other ways, the fric¬ tion coefficient may be determined also for other directions in the sack paper.

Results

The tensile strength is scarcely affected by the em¬ bossing while the extension seems to decrease somewhat, which results in a tensile energy absorption decrease of up to 20% in the longitudinal, and up to 16% in the cross di¬ rection.

The air resistance increases up to 12 units, from 29 to 41 s.

The friction increases up to 0.11 units from 0.63 to 0.74. Table 1

Pressing Pressing Tensile Extension Tensile Air- Friction time pressure strength % energy ab- resi- coeffic. kN/m sorp. J/m stance

Fig. sec. I /αn long.across long.across long.across sec.

1 1 3 7.16 3.04 2.78 10.64 127 233 37.7 0.67

1 5 3 6.51 3.38 2.93 11.20 124 267 37.8 0.61

2 1 3 6.50 2.95 2.85 9.93 117 214 34.0 0.70

2 5 3 7.01 3.06 2.87 9.63 126 213 36.5 0.68

3 1 3 6.62 2.90 2.92 10.14 123 218 35.7 0.72

3 5 3 6.36 3.03 2.68 11.05 108 242 41.2 0.67

4 1 3 7.00 3.00 3.19 11.37 137 248 35.3 0.72

4 5 3 7.06 2.97 2.88 10.43 126 225 36.1 0.74

5 1 3 6.63 2.88 2.84 10.00 119 215 28.5 0.62

5 5 3 6.97 3.01 3.05 10.08 133 221 35.9 0.64

6 1 3 6.59 3.03 2.90 9.87 122 216 30.3 0.68

6 5 3 6.57 3.22 2.74 11.42 114 256 35.9 0.68

0 0 0 6.86 3.18 3.24 11.22 139 254 28.9 0.63

Figure 1 = Rhcmbs 4 x 6 πm, 39 pieces/dm

Figure 2 = Rhcπbs 3 x 9 πm, 28 pieces/to

Figure 3 = Rhcmbs 3 x 9 πm, 48 pieces/dm

Figure 4 = Squares 5 ππt, 49 pieces/dm

2

Figure 5 = Squares 3,! 5 πm, 49 pieoes/dm

Figure 6 = Rectangle, diagonally, 32 pieces/dm

Figure 0 = Uheπfcossed paper

SUBSTITUTE SHEET

Claims

PATENT CLAIMS

1. Embossed wrapping paper, preferably sack paper, whose embossing pattern shows a plurality of out of the paper plane raised, delimited, identical figures c h a r a c t e r i z e d by, that

A. the patterns are straight-lined, from each other sepa¬ rated and over the paper plane evenly distributed and provided with three or more, preferably four sides and planar figure surface, which is parallel to and situated at a distance of 0.05-0.40 mm from the surrounding paper surface and with a total figure area which constitutes <40%, preferably <20%, of the total paper area that has been embossed, and by that

B. the connection surface between figure surface and sur¬ rounding paper surface substantially is perpendicular to the paper plane.

2. Embossed wrapping paper according to claim 1, c h a r a c t e r i z e d by, that the figures consist of parallelograms defined as chequers in the checked pattern that is obtained if a number of parallel lines (1,, 1₂,

V V are intersected by i number of other parallel lines (!' 1' ^A 2' 1^*'3' ^x 4' 1^A'5' 1' ) under an angle . where n and n are integers greater than 10 and where the perpendicular distance between

1, and 1_ = a. and between 1', and 1'₂ = c.

1₂ and 1₃ = b. 1'₂ and 1'₃ = d,

1₃ and 1 = a. 1'₃ and 1'₄ = c.

14- and l_c5 = b 1^»4. and 1' b = d,

an even uneven integer. resp. an uneven integer. where the figures in the pattern are defined as the total area over which the lines extend, minus the area between lines at the distance b respectively d from each other, and where a, b, c, d are chosen so, that a b and c<d.

3. Embossed wrapping paper according to claim 2, c h a r a c t e r i z e d by, that a = c and b = d, pre¬ ferably with a^b.

•

4. Embossed wrapping paper according to any one of the claims 2-3, c h a r a c t e r i z e d by, that the lines 1 1₂ ....1 have a positive slope and the lines l¹,. 1'₂ ...l^l have a negative slope against the machine direction of the paper, preferably with the same absolute value and that the angle is 10° < A ^170°, pre¬ ferably 10°< S 90t^«o

5. Embossed wrapping paper according to claim 1, c h a r a c t e r i z e d by, that a corner-to-corner distance, in appropriate cases a diagonal distance, in respective figure is longer than the shortest distance to the figure lying closest nearby.