FR2655070A1 - PAPER PULP BASED ON CELLULOSIC FIBERS AND MINERAL FIBERS (GLASS) IN THE FORM OF WOOL. - Google Patents

Abstract

The invention relates to sheets based on cellulosic fibers produced by the papermaking process and containing mineral fibers. According to the invention, the paper pulp contains mineral fibers which have the characteristics of fibers intended for thermal insulation, namely: have an average diameter of between 3 and 8 micrometers and are in the form of a wool. The sheets obtained according to the invention have, in particular, the advantage of having an improved "hand".

Description

The invention relates to cellulosic fiber-based sheets

  More specifically, the invention relates to the improvement of certain

  properties of this type of products.

  The paper industry offers a wide variety of products in terms of both destination and composition.

  at pressure, the product must satisfy an im-

  bearing conditions: mechanical strength, dimensional stability, good appearance, good surface appearance In addition, under the conditions relating to the product itself,

  in addition to those related to the manufacturing process

  The choice of constituents must allow for the produc-

  under the best conditions of cost and efficiency.

  This set of factors requires the paper manufacturer to

  great control over the various constituents and their

  fluence, but also the most adequate determination 2 - combinations of constituents, the influences of these

being sometimes contrary.

  In paper for printing, the "hand" is a quality to which users are increasingly sensitive This specific property of paper is, in part, appreciated subjectively A paper with a good hand is appreciated as a quality paper The hand

  corresponds to the mass volume of the sheet A same gram-

  mage, the hand is better than the thickness is

  The user prefers a paper which is more

  "Regardless of the subjective aspect, an improvement

  the hand is also translated into a better "rigidity".

  of relatively low weights

  the leaves while presenting resistance to

  sufficient caniques can be too flexible.

  even for these low grammages, to have a certain

some rigidity.

  The invention therefore proposes to provide new papermaking sheets presenting, in particular, a

  improvement of the hand and this while remaining in conditions

satisfactory costs.

  The production of paper leaves according to the invention

  is made from a pulp based on cellulosic fibers containing a proportion which does not exceed 25% by weight of mineral wool, said wool being formed

  fibers that have the dimension-

  fibers produced for thermal insulation.

  The low use of half fibers

  in paper techniques aims at, usually

  It seems that the aim pursued previously has led to the proposal of only the use of fibers whose reinforcing ability is well known. In particular, it is a question of fibers. so-called "textiles", ie fibers produced continuously

  by mechanical stretching For their incorporation into the

  they must be reinforced, these fibers are cut into elements of a certain length of the order of a few

  millimeters or tens of millimeters.

3 -

  Textile fibers are remarkable for their

  they owe their regularity both in diameter

  than in length, both being linked to their mode of pro-

  Textile fibers are also distinguished from

  minerals produced under other conditions by the

  their diameter remains relatively large Typical-

  The diameter of textile fibers is between 9 and

micrometers.

  Apart from the fact that the textile fibers have large diameters, their cost is also relatively high for the use in question. In other words, their incorporation significantly increases the cost of the textile.

  final product, even when their content remains low.

  It should also be noted, contrary to the aim of

  followed according to the invention, it does not seem that these fibers have been considered to improve the hand of paper sheets. Still with a view to improving certain properties of

  papermaking sheets, and incidentally facilitate the sewer-

  of the pulp during the production process, it has been proposed to substitute fibers for

  obtained by "flame stretching" of glass filaments.

  The fibers in question usually have very small diameters of less than 3 micrometers. These fibers also have relatively constant diameters, even if they are not rigorously calibrated like textile fibers. As for textile fibers, their cost limits their use. textile fibers also, it does not appear that it was intended to use them for

  improve the hand of the leaves produced.

  A particularity of the invention is to use mineral fibers such as those commonly produced by techniques used for the formation of fibers for thermal insulation. An advantage of such fibers is that they are produced in large quantities and for relatively low costs In return,

  insulation fibers are less regular, especially in

  and are known to exhibit a certain fragility when subjected to mechanical stresses. Count 4 -

  on the one hand, the role that was expected of the

  previously incorporated in productions

  paper mills, but also treatments to which

  In the course of the preparation of the paste and the sheet, it is understood that the insulation fibers have so far been removed from this type of application. The inventors have shown that mineral fibers of the "insulation" type, incorporated in paper pulp, were not only not destroyed by

  treatment, but on the one hand are reduced to the

  most suitable for the considered uses (less than one millimeter) and above all, on the other hand, were

  able to give the leaves produced a "hand"

  even when these fibers are introduced in a small proportion. The reasons which lead to these properties are not perfectly elucidated The comparison with the effects obtained with textile fibers on the one hand and the very fine fibers, makes one think that the peculiarities of structure

  insulation fibers must intervene in a certain way

  In particular, we can think that a certain lack of homogeneity of these fibers can favor the "bouffant" of

  In other words, one might think that

  irregular shape and shape

  entanglement that "swells" the structure of the leaf.

  In comparison, textile fibers which are

  In fact, for very fine fibers, they could be insufficiently resistant to pressure so that, even if entangled, they would not be able to occupy the necessary volume to obtain

this bouffant.

  Even if the explanation is only a hypothesis, the

  The effect of the length of the fibers is an example If one uses indeed fibers too short, the gain of hand diminishes Conversely, in the direction of the confirmation of this one the elongation of the fibers beyond a certain threshold brings no further improvement In both cases, this can be justified by the ability of the fibers to

  form well entangled clusters.

  It should be emphasized in this connection that a certain fragility of the fibers "insulation" is not an inconvenience for the implementation of the invention In the usual modes of production of these fibers, which we will specify later,

  the length of recovered fibers is usually several

  tens or even hundreds of millimeters.

  It goes without saying that when it is introduced into the

  the preparation of the pulp, mineral wool

  The process undergoes operations that break the original fibers into much shorter sections, whether this introduction is made at the level of the pulper, the refiner or even the

checkout.

  In the experiment, in order for the papermaking sheets to have the desired qualities, the mineral fibers they contain preferably have a length of at least

  0.1 mm Taking into account, on the one hand, the other

  fibers, especially their diameter, and secondly the conditions of use, it is preferable that

  in the pulp used a high proportion of the medium fibers

  have a length of between 0.2 and 0.6 mm.

  Under these conditions, the breakage of the fibers during the preparation of the dough is an advantage when starting from fibers "insulation", in that it is not necessary to perform a cutting operation prior to

incorporation into the dough.

  If we can use the glass wool

  production processes and in more or less bulky tufts, a

  this wool with smaller dimensions facilitates the in-

  In this sense, it may be advantageous, especially

  to feed the fiberglass paste and also to facilitate the incorporation thereof into the dough and to obtain a homogeneous mixture, to use "nodules" previously prepared from the wool in bulk These nodules , whose dimensions are for example 0.5 to 5 mm, are obtained by a shredding operation of the 6 - wool in bulk followed by "nodulation" in a rotating drum It should be clearly seen that this type of operation, even if it results in cuts of the initial fibers, gives them no regularity Moreover, the lengths of the fibers after the nodulation operation are relatively large compared to those that are

  fixed when cutting continuous fiber

  naked (textile type) for incorporation into the dough on both the treated materials, but also in the conditions of implementation and the results obtained, these nodulation operations are not similar to those

  cutting or cutting done previously.

  Apart from the fact that the lengths of the fibers are in

  part of the result of the treatment of the dough, another

  3 dimensional feature distinguishes the "isolated" fibers

  other mineral fibers previously used.

  Indeed, the average diameters of the insulation fibers are,

  traditionally, included in a range of 3 to 8 micro-

  meters and, more usually, in the range 4 to 6 micro-

meters.

  In the field of insulation, the choice of fiber diameters results from various considerations Thus, for the same fiber mass, the thermal resistance of the wool is all the higher as the diameters of the fibers are smaller Conversely , too fine fibers do not offer the necessary mechanical strength to keep the

  wool its properties over long periods of use.

  To these contrary imperatives are added considerations

  It is clear that the stretching of

  These considerations, to a certain extent, also apply to the fibers used in the pulp when they are given as their role.

  the improvement of the hand Fibers must be sufficient

  particularly fine so that, for a given mass, the effect

  bulking is important and yet have a good

resistance to crushing.

  The insulation fibers used according to the invention are obtained by known techniques. These are 7-techniques in which the molten mineral mass is subjected to a centrifugation operation. Depending on the case, the centrifugation makes the material pass through calibrated or only disperses the melt more randomly At the centrifugation is often added a

  effect of drawing fibers by the action of gaseous currents.

  For the invention, the preferred fibers come from techniques in which the centrifuge also serves as a die. The wool obtained by these techniques has the great advantage of being practically free from

  particles, that is to say particles of

  much higher than that of the fibrous mass

so-called.

  The advantage of the techniques in which the produc-

  13 fiber combination combines centrifugation and stretching

  First of all, it is the efficiency of these techniques which makes it possible to lower the cost of wool. Moreover, it seems that the implementation of gaseous currents at high speeds in the drawing process results in the

  production of fibers particularly suitable for felting.

  This can be explained by the existence of strong turbulence in these gaseous currents, resulting in the formation of fibers

very "curly".

  Particularly preferred methods for obtaining these fibers are those described in European patents.

No. 91,381 and No. 91,866.

  The advantage of the techniques described in these patents

  is to allow the production of fibers of characteristic

  varied in all cases in large quantities and for

relatively low costs.

  According to the invention, the fibers used have

  average diameter between 3 and 8 micrometers as we have seen, but for a given wool and a given average diameter, the fibers, taken individually, can deviate from these average values In any case, whatever the average diameter of the selected fibers, at least 80% by weight of the fibers constituting the wool have a diameter of between 3 and 8 micrometers The differences between fibers of the same wool are more or less important 8 - depending on the production method The techniques indicated more

  high lead to fibers whose histogram is relative to

  For example, for a wool whose average fiber diameter is of the order of 5 micrometers, 90% by weight of the fibers have a diameter of between 3.5 and 7 microns. For the uses envisaged according to the invention,

  than the distribution of the diameter of the fibers, the im-

  bearing is to avoid the presence of infibulated particles.

  The fibers obtained according to the techniques in reference are, from this point of view, quite remarkable. The rate of infibré, for wool insulation, is much lower than

  what we get by other techniques.

  The introduction of mineral fibers into the paper composition is deliberately limited to a maximum of 25% by weight of the dry matter It is possible to increase

  the amount of mineral fiber but, in addition to the

  corresponding cost increase, the resulting paper can

  present unintended peculiarities for the impres-

  too high a mineral fiber content may

  This leads to an undesirable increase in porosity.

  Moreover, if the improvement of the hand is

  even for low levels of mineral fiber, a minimum of 2% may be considered necessary for

  lead to a significant result.

  Preferably, the mineral fiber content is

  between 2 and 15% by weight of the dry matter of the

paste used.

  When it comes to improving the hand, another way to specify the amount of mineral fiber needed is to

  to fix it according to the minimum improvement

  quis A useful lower limit of the gain can be fixed at

  about 3% The minimum amount of fiber introduced

  the invention is therefore such that, preferably, the gain

  of at least 3% in relation to the paper obtained

  held with an identical dough except for the presence

of these mineral fibers.

  The invention also relates to papermaking sheets

  cellulosic fiber-containing materials containing insulating mineral fibers, sheets of which the hand

  Such paper sheets are, in

  particular, those in whose composition the only agent likely to improve the hand is constituted by these mineral fibers In this connection, it should be noted that other agents are known which have the role of increasing the mass volume Among those These include, in particular, what can be described as "lightening" loads such as microspheres. The disadvantage of such agents, in particular

  out of their often high cost, is that they can

  to the substantial lowering of certain

  mechanical properties such as burst strength or tear resistance A remarkable advantage of using fiber insulation for improving the

  under the conditions of the invention, is that the

  mechanical properties in question are little affected.

  The invention is described in detail in the

  examples which are intended only to illustrate it.

LEXEPE 1

  Samples are prepared from a paste

  Sophisticated kraft refined to 210 SR, incorporating various

  lities and quantities of glass wool.

  To facilitate their incorporation, the glass fibers are first soaked in water and then added to the dough with stirring The mixture is passed to Lhomargy shredder

for 2 minutes.

  The leaves are made with the Noble form

  and Wood in 150 g / m 2, following the standard NF Q 50-002.

  The tests are carried out incorporating increasing amounts of fiber. A comparison is made using

of a control sheet.

  The sheets according to the invention (n O 2), in which

  the insulation fibers have an average diameter of 4 microns.

  very, are also compared to leaves prepared in

  incorporating microfibres with a diameter of 1

crometer (n O 1).

  The results of the hand measurements (in cm 3 / g) of the sheets prepared according to standard NF Q 03-016 (ISO R 534) are as follows: -:% glass fibers: O: 2 5: 10

: 1 1.37 1.37 1.39: 1.45

2: 1.37: 1.50: 1.65: 1.68:

  The addition of the glass fibers under the conditions of the invention causes an increase of the hand itself 1 O for a content of 2%. The gain in hand obtained by introducing the fibers of the insulation type is advantageously compared.

  according to the invention to that corresponding to microfibers.

  For 10% of these, the improvement of the hand remains lower than that obtained with only 2% of fibers

insulation.

  It is still observed in these tests that the improvement of the hand is not uniform; fast for the contents

  weaker, it progresses more slowly when the

  neur increases above 5% by weight.

  At the same time, burst measures, deter-

  the resistance of the sheets prepared and conducted according to standard NF Q 03-053 (ISO 2758), show that the sheets incorporating the insulation fibers are substantially

  better than those containing microfibers.

  There is still an improvement in the dimensional stability of the farms incorporating the fibers of

  glass (DIN 53130 and NF C 26131 standards).

EXAMPLE 2

  Another series of tests is carried out with a printing paste type without mineral filler The dough is a mixture of whitened Kraft pulp (66% Socel, 34% Iggesund) refined at 2805 R.

  The leaves are drawn in 80 g / m 2 on No-

ble and Wood.

  The fibers used are the same as in example 1: microfibres (3), insulation fibers (4), insulating fibers with polyvinyl alcohol sizing at 0.8% (5), fibers

  insulation with 0.8% starch sizing (6).

  The measurements of the hand for these various tests are 11 - grouped in the following table:% glass fibers: O: 5 10 to ::

: 3 1.5 1.65 1.72

: 4 1.5 1.94 2.14

: 1.5 1.81 2.08

to: at :::

6 1.5 1.88 2.20

  The trends observed on the samples of Example 1 are confirmed on these sheets of another nature. The increase of hand is strong in all the samples corresponding to the invention (4, 5, 6) and remains

very modest for microfibres.

  As previously also, dimensional stability

  It is improved mainly for the higher grades and the lowering of the mechanical strength.

  is less sensitive for leaves obtained with

insulation.

  The dimensional stability measurement results at

  95% relative humidity, as a percentage of elongation

  are:% glass fibers: O 10

: 0.44% 0.32%:

::

0.44% 0.3%:

0.44 0.29:

5: 0.44%: 0.29%

: 6: 0.44%: 0.29%:

EXAMPLE 3

  The tests of Example 2 are renewed with a mineral filler consisting of calcium carbonate.

  (marketed as Hydrocarb 60) The mineral load

  It represents 10% of the mass of the dough.

  The results of the measurements of hand and stability di-

  are listed in the following tables The samples are listed respectively 3 c, 4 c, 5 c and 6 c: Hand measurement::% glass fiber: O: 5: 10:

:: :::

: 3: 1.57: 1.66: 1.8:

:: ::

  : 4 c: 1.57: 1.85: 1.98: t 5: 5 c: 1.57: 1.93: 1.91:

::: ::

  : 6 c: 1.57: 2.03: 2.02: Dimensional stability::% glass fibers: O: 10:

:: ::

: 3 c: 0.36%: 0.36%:

:: ::

: 4c: 0.36%: 0.29%:

* ::::

: 5c: 0.36%: 0.28%:

:::

: 6 C: 0.36%: 0.29%:

EXAMPLE 4

  A series of tests is carried out with a dough type "impressionécriture" without mineral filler The dough is a

  bleached Kraft pulp mix (60% beech, 40%

neux) refined to 40 SR.

  The leaves are drawn in 70 g / m 2 on the Pope line.

  pilot at a speed of 20 m / mm.

  The fibers used are: microfibers with a mean diameter of 1 μm (n 7), 13 - insulation fibers with a mean diameter of 4 μm (n O 8), textile fibers with a diameter of 11 μm and cut at 5 mm

(No. 9)

  The hand measurements and dimensional stability are grouped in the following table: n test: control: 7: 8 9::% glass fiber O: 5: 5: 5

to:

  hand (cm 3 / g): 1.69 1.78 1.84: 1.67:

to: to :: ::

dimensional stability

between 20 and 80% of

  Relative dyed: Run direction (%): 0.35: 0.33: 0.25: 0.32 Cross direction (%): 0.83: 0.80: 0.64: 0.69 These tests show that the results obtained under the conditions of the invention (test NO 8) are better,

  both in the hand and in the stability of the

  This improvement is observed vis-à-vis

  microfibers (test No. 7) and with respect to textile fibers

tiles (test No. 9).

  Moreover, these tests confirm on pilot line,

  therefore in conditions close to industrial conditions

  trielles, the results highlighted on formette.

14 -

Claims (7)

REVENDI CATI ONS   1 Paper pulp made from cellulosic fibers   holding mineral fibers, characterized in that the mineral fibers have the characteristics of the fibers intended for thermal insulation, namely: have an average diameter of between 3 and 8 micrometers and are under shape of a wool.   2 Papermaking pulp according to claim 1 in the   which mineral fibers are introduced at the rate of 2   25% by weight of the dry matter.   Papermaking pulp according to claim 1 or   in which the mineral fibers have, for at least 80% by weight of these fibers, a diameter between 3 and 5 micrometers.   4 Paper pulp according to claim 1 or   claim 2 in which the mineral fibers have a   average diameter between 4 and 6 micrometers.   Papermaking pulp according to one of the preceding claims   in which the mineral fiber content is   between 2 and 15% by weight of dry matter.   6 Papermaking pulp according to claim 1 in the   which fibers in the form of wool are introduced into nodules 0.5 to 5 mm.   Papermaking pulp according to one of the preceding claims   cedentes, characterized in that the mineral fibers   troductions are glass fibers obtained by means of   centrifugation and gas stretching.   8 Leaf obtained from a paste according to one of the   preceding claims, characterized in that the fi-   minerals it contains have an average length between 0.2 and 0.6 mm.