JP2009524747A - Method for producing fluorescent white paper - Google Patents

Abstract

  The present invention relates to a fluorescent whitening which results in a surprisingly high light resistance of the resulting paper by treatment with a pulp suspension having a fluorescent whitening filler composition comprising fluorescent whitened plastic fibers, preferably polyester fibers. Relates to a method for producing the finished paper.

Description

  The present invention relates to a method for producing fluorescent whitened paper by treating a pulp suspension with a fluorescent whitening filler composition.

  A high degree of whiteness is a desirable property of paper and cardboard articles. The most important raw material in the paper industry is pulp, which naturally absorbs blue light, thus giving the paper a yellowish and matte appearance. Optical brighteners supplement the absorption of blue light in the paper industry by absorbing UV light with the longest wavelength of 350-380 nm and converting the UV light into visible blue light with the longest wavelength of 440 nm. Used for.

  Triazinylaminostilbene type optical brighteners have been used almost exclusively to whiten paper, either by application to pulp or paper surfaces. However, the light fastness of this type of brightener is inferior to moderate, or “Blue Wool Scale” (F. Muller, D. Loewe and B. Hunke, “Optische Aufheller-neuerenkenssenzentien eigennsenzen energentzen energentze energentze energentzen eugenthen energentzen eigenfen gengen fensengen zien eigenngen energenten energenten energenten energentzen energentzen eugenhenchengen egentench It is well known that it is not better than 1 to about 3 in Wochenblat fur Papierfabrication 1991, 6, 191-203). Thus, there is a need to protect fluorescent whitened paper from yellowing with light.

  In order to provide a fluorescent whitening paper with high light fastness, whitening agents other than those of the triazinylaminostilbene type, i.e. typically of the benzoxazole, naphthalimide, triazoylcoumarin or triazinylpyrene type It is generally recognized that it is preferred to use a whitening agent used for fluorescent whitening of textile products such as goods. However, such brighteners are typically even more expensive and are possible only by difficult application to either pulp or paper surfaces.

  EP 801700 solves some of these problems by describing the use of fluorescent whitened polyacrylonitrile powder to prepare white coating slips for paper. Preferred optical brighteners are those typically used to provide high light resistance on textiles, such as triazoylcoumarin or benzoxazole types. Paper prepared using such a coating slip exhibits an excellent whitening effect with high light resistance. However, there is no suggestion that this approach can be used to prepare fluorescent whitening paper with more economical pulp application.

  The economical use of textile whitening agents to prepare fluorescent whitening paper is therefore a difficult problem for which no satisfactory solution has yet been found.

  Surprisingly, by treating the pulp suspension with a filler composition containing finely divided and fluorescent whitened plastic fibers, high light fast fluorescent white paper can be obtained in an economical manner. But now it has been found.

  Accordingly, an object of the present invention is a method for fluorescent whitening paper, wherein a filler composition comprising fluorescent whitened plastic fibers is added to a pulp suspension.

  The fibers can preferably be made of polyester, polyethylene, polypropylene or polyamide. Most preferably, the fibers are made of polyester.

  The fiber has a fineness of 1-10 dtex and is cut to a length of 0.1-1 mm, preferably the fiber has a fineness of 1-2 dtex and a length of 0.2-0.6 mm. Have.

  The preparation of polyester fibers is well known and described, for example, on page 18 of “Handbook of Fiber Chemistry” by Menachem Lewin published in 1998 by Marcel Dekker.

  The production of fluorescent whitened polyesters is equally well known and is described, for example, in GB 835,898 and EP 1379585.

  For the purposes of the present invention, the fibers are preferably fluorescent whitened with compounds of formulas (1) to (4).

In formula (1),
R _{1 to} R ₈ are independently of each other a group of hydrogen, C _{1 to} C ₂₀ alkyl or the formula —COOR ₉ , wherein R ₉ is hydrogen, C _{1 to} C ₂₀ alkyl or phenyl. Or R ₁ -R ₈ is a group of the formula —SO ₂ R ₁₀ , wherein R ₁₀ is hydrogen, C ₁ -C ₁₀ alkyl or C ₁ -C ₁₀ hydroxyalkyl, and A is Stilbene, naphthalene, phenylene, thiophenylene or biphenylene, or a mixture of the compounds.

Further preferred optical brighteners are those of formula (1) wherein R ₁ -R ₈ are independently of one another hydrogen or C ₁ -C ₄ alkyl, and A is stilbene, naphthalene, phenylene, thio Phenylene or biphenylene).

The most preferred optical brightener is a compound of formula (1), wherein R ₁ -R ₈ are independently of each other hydrogen or methyl and A is stilbene.

  The fluorescent whitened plastic fiber contains 10 to 500 ppm, preferably 20 to 250 ppm of fluorescent whitening agent.

  The pulp may be any conventional pulp used to produce paper, such as stone groundwood pulp, thermomechanical pulp, chemithermomechanical pulp, semi-chemical pulp, sulfite pulp or kraft pulp, or mixtures thereof. Good.

  Generally, the pulp suspension is treated with an instant filler composition of 2-60%, preferably 10-40 wt%, based on the weight of the dry pulp.

  The filler composition can be added to the pulp suspension either in dry form or preferably in the form of an aqueous dispersion. It can be useful to add a dispersant, in particular a suitable dispersant of the type described in EP 964,015. Finally, the paper is formed on a conventional paper machine wire screen, pressed and dried.

  The present invention also provides a fluorescent whitening paper produced by an immediate process, and this paper contains 2-60%, preferably 10-40 wt% of the filler composition of the present invention, based on the weight of dry pulp. Including.

  Fluorescent white paper can also contain other additives used in the common paper industry. Examples of such additives include sizing agents (eg, pine, starch, alkyl ketene dimer, alkenyl succinic anhydride), wet strength resins (eg, polyaminoamide epichlorohydrin resin), retention and drainage aids (eg, polyaluminum). Chloride, polydiallyldimethylammonium chloride), and a shading dye.

  The following examples serve to illustrate the present invention. All parts and all percentages are by weight unless otherwise indicated.

  Made by the known method of fineness 1.7 decitex containing a mixture of optical brighteners of structure 5a-c in a ratio of approximately 30:50:20 and cut to 0.5 mm Stir 5 parts of polyester fiber, 0.025 part of dispersant (Cartaspers ™ PSM commercially available from Clariant) and 1000 parts of water for 5 minutes to achieve 0.5% dispersion of the fluorescent whitened fiber Generate a body.

  Stirring a 50:50 mixture of bleached firewood and spruce wood pulp, beaten 0.5 parts of a 0.5% dispersion of fluorescent whitened fibers, then beaten to a 35 ° shopper rigger beating degree Add to a portion of the prepared 0.5% aqueous suspension (1000-X). A paper sheet is then produced by drawing out the dispersed suspension through the wire mesh. After pressing and drying, the fluorescent whitening paper contains 5% (X = 50) -30% (X = 300) fluorescent whitened polyester fibers, equivalent to a fluorescent whitening agent content of 7 ppm to 42 ppm.

  Each paper sheet was measured at R457 whiteness on a calibrated Minolta 3270D spectrophotometer.

  Accelerated aging experiments are performed by exposing the paper to the Xenotest apparatus. R457 whiteness measurements are taken at 70,140 and 280 hour intervals. The results are shown below in the form of a table (Table 1) and a graph (FIG. 1).

Table 1

図１：５〜３０％の蛍光増白されたポリエステル繊維を含有する紙のＲ４５７白色度への、２８０時間以上の光への曝露の効果。

FIG. 1: Effect of exposure to light over 280 hours on R457 whiteness of paper containing 5-30% fluorescent whitened polyester fibers.

  The present invention provides a high light fast fluorescent whitening paper that has the additional advantage that a surprisingly low concentration (7-42 ppm) of fluorescent whitening agent is necessary to achieve a high degree of whiteness. It is clear from the results.

Comparative example
Comparative Example 1: A paper sheet is prepared as in an example containing fluorescent whitened polyester fibers of 25% whitened polyester fibers (X = 250).

Comparative Example 2: Non-whitened pulp A paper sheet is prepared as in the example except that no fluorescent whitened polyester fiber is added.

Comparative Example 3: Unwhitened polyester fiber A paper sheet as in Example, except that it contains 25% (X = 250) unwhitened polyester fiber instead of fluorescent whitened polyester fiber Is made.

Comparative Example 4: Unwhitened polyester fiber and fluorescent whitening agent (5a-c)
Instead of all fluorescently whitened polyester fibers, it contains 25% (X = 250) unwhitened polyester fibers and approximately 1000 parts of 1000 parts of a 0.5% aqueous suspension of fibers. A paper sheet is prepared as in the example except that 0.0075 part of a mixture of optical brighteners of structure (5a-c) in the ratio of 50:20 and 0.0075 parts are added separately.

Comparative Example 5: Non-whitened polyester fiber and fluorescent whitening agent (6)

  Instead of all fluorescent whitened polyester fibers, it contains 25% (X = 250) non-whitened polyester fibers, and 1000 parts of a 0.5% aqueous suspension of fibers is made into structure (6) A paper sheet is prepared as in the example except that 0.004 parts of the optical brightener and ## STR4 ## are added separately.

  An accelerated aging experiment is performed as an example. A result is shown with the following table | surface (Table 2) and a graph (FIG. 2) form.

Table 2

図２：紙のＲ４５７白色度への、２８０時間以上の光への曝露の効果。

Figure 2: Effect of exposure to light over 280 hours on R457 whiteness of paper.

  The comparative example shows the advantage of the present invention to provide white paper with excellent light resistance.

  It is clear that the addition of fluorescent whitened polyester fiber (Comparative Example 1) gives a much whiter paper than the addition of unwhitened polyester fiber (Comparative Example 3). Similarly, it is clear that the fluorescent whitening agent is incorporated into the polyester fiber, when added separately (Comparative Example 4). The separate addition of the triazinylaminostilbene type optical brightener (6) in particular gives a whitening paper, but the light resistance of this paper is inferior (Comparative Example 5).

Claims (14)

  A method for fluorescent whitening paper, wherein a filler composition comprising fluorescent whitened plastic fibers is added to a pulp suspension.   The method of claim 1, wherein the fibers are made of polyester, polyethylene, polypropylene or polyamide.   The method of claim 2 wherein the fibers are made of polyester.   4. A method according to claim 3, wherein the fibers have a fineness of 1-10 dtex and are cut to a length of 0.1-1 mm.   The method according to claim 4, wherein the fibers have a fineness of 1-2 dtex and are cut to a length of 0.2-0.6 mm. The fibers are fluorescently whitened with compounds of formulas (1) to (4);

And in Formula (1),
R _{1 to} R ₈ are independently of each other hydrogen, C _{1 to} C ₂₀ alkyl or a group of formula —COOR ₉ ;
R ₉ is hydrogen, C ₁ -C ₂₀ alkyl or phenyl, or
R _{i to} R ₈ are of the formula —SO ₂ R ₁₀ ,
_{Wherein, R 10} is _hydrogen, C 1 _{-C 1O} alkyl or _C 1 _{-C 10} hydroxyalkyl al kills and
A is stilbene, naphthalene, phenylene, thiophenylene or biphenylene, or a mixture of the compounds,
The method according to any one of claims 1 to 5. The fiber is fluorescently whitened with a compound of formula (1),
In which R _{1 to} R ₈ , independently of one another, are hydrogen or C ₁ -C ₄ alkyl, and
A is stilbene, naphthalene, phenylene, thiophenylene or biphenylene.
The method of claim 6. In which R _{1 to} R ₈ are, independently of one another, hydrogen or methyl, and
A is stilbene,
The method of claim 7.   9. A method according to any one of claims 2 to 8, wherein the optically brightened plastic fiber comprises 10 to 500 ppm of optical brightener.   10. The method of claim 9, wherein the optically brightened plastic fiber comprises 20 to 250 ppm of optical brightener.   11. A method according to any one of the preceding claims, wherein 2 to 60 wt% of the fluorescent whitening filler composition is added to the pulp suspension based on the weight of the dried pulp.   12. The method of claim 11, wherein 10-40 wt% of the fluorescent whitening filler composition is added to the pulp suspension based on the weight of the dry pulp.   13. A method according to claim 11 or 12, wherein the fluorescent whitening filler composition is added to the pulp suspension in the form of an aqueous dispersion.   Fluorescent white paper produced by the method according to any one of claims 1-13.