EP0801700B1 - Use of optically brightened plastics for optically brightening paper-coating compounds and paper-coating compounds optically brightened in this manner - Google Patents

Abstract

Paper coating slips having high whiteness, high greying limit and high lightfastness can be prepared with the aid of whitened finely divided plastics.

Description

The invention relates to white-tinted fine-particle plastics their use for tinting white of paper coating slips based on synthetic binders and paper coating slips, which contain such white-tinted plastics.

Coated papers and boxes are used on a very large scale aqueous coating slips based on polymeric binders used. Common binders for paper coating slips include, for example, butadiene / styrene, styrene / butyl acrylate, Acrylonitrile / butadiene / styrene, styrene / butadiene / acrylic acid alkyl ester, Acrylic acid alkyl ester, ethylene / vinyl chloride and ethylene / vinyl acetate copolymers as well as the homopolymers polyethylene, polyvinyl chloride, polyvinylidene chloride, Polyvinyl acetate and polyaddition compounds such as polyurethanes.

In addition to the usual white pigments - mainly contain china clay and calcium carbonate the coating slips for optical brightening are usually anionic white toners, e.g. those of the bis-triazinyl-aminostilbene-disulfonic acid type. These whites however, only lead to very unsatisfactory white effects and very low ones Graying limits (= white toner concentration at which a further white toner addition there is no increase or even a decrease in whiteness). About that in addition, the white toner types mentioned do not have one in the coating slips adequate lightfastness.

It has already been recommended to improve the white effect in coating slips by using hydrophilic cobinder or carrier ("Das Papier" 36 (1982) 66; DE-A-3 502 038, EP-A 4 37 90). However, the hydrophilicity of the added components increases the water sensitivity of the coated paper to an undesirable extent.

It has also been proposed to add dispersion brighteners in the presence of dispersants use (GB-A-1 294 173, GB-A-1 349 934). The attainable whiteness and the strong However, the degree of whiteness cannot depend on the drying temperature satisfy.

Water-soluble white toners have also been condensed with aminoplasts and these condensates are particularly recommended for whitening paper coating slips (DE-A-3 112 435). However, these suggestions have been due to insufficient lightfastness and cannot enforce rheological difficulties.

Furthermore, it is known for the optical brightening of paper to use plastics such as cellulose, polyester, polyamides and urea-formaldehyde in combination with whiteners (DE-B-1 108 560) or to see mahomolecular substances such as vinyl polymers or vinyl copolymers and whiteners (DE-B -1 149 244). Cellulose powders are also used in conjunction with white toners for whitening paper coating slips (EP-A-0 409 028).

The production of coated papers and boxes with high whiteness, high Graying limit and good light fastness is a difficult one, not yet satisfactorily solved task.

It has now surprisingly been found that white-tinted, finely divided plastics, which are not aminoplasts, paper coating slips very high degrees of whiteness, high Give graying limits and high light fastness.

The invention thus relates to white-tinted, finely divided plastics from the series Polyacrylonitrile and their use for whitening paper coating slips Basis of synthetic binders.

Another object of the invention are with the help of these white-tinted plastics white-colored paper coating slips.

The basis of the white-tinted plastics to be used according to the invention Plastics include polyacrylonitriles.

Preferred polyacrylonitriles have intrinsic viscosities (measured in dimethylformamide at 20 ° C) from 1.18 to 2.22 dl / g.

In the sense of the invention, "fine-particle" are plastic powders with a (as weight average determined) particle size of less than 1 micron.

A person skilled in the art can opt for the selection of preferred white tones Orient brighteners that are used in white tones in the textile sector. Preferred White tones result in comparatively high light fastness on textile fibers - Measured in the Xenotest based on the guidelines for determining the Color fastness according to DIN 54004 - from at least 4, preferably from 5 to 7.

worin

R

Ethyl oder Phenyl bedeutet;

worin

X

für CH oder N,

R¹

für CH₃ oder CH₂-C₆H₅ und

R²

für H oder SO₂-CH₃ stehen;

und

worin

R³

für NH₂, CH₃, NH-C₃H₆-N(CH₃)₃ ⁺ An^-, C₂H₄-N(CH₃)₃ ⁺ An^-, CH₂-CH(CH₃)-N(CH₃)₃ ⁺ An^-, CH(CH₃)-CH₂-N(CH₃)₃ ⁺ An^-, C₂H₄-O-CH(CH₃)-CH₂-N(CH₃)₃ ⁺ An^- oder C₂H₄-CO-NH-C₃H₆-N(CH₃)₃ ⁺ An^-

und

An^-

das Anion einer Mineralsäure, Ameisensäure, Essigsäure, Milchsäure oder ^-O₃SOCH₃ bedeuten.

Preferred white toners for finely divided polyacrylonitriles are compounds of the formulas:

wherein

R

Means ethyl or phenyl;

wherein

X

for CH or N,

R ¹

for CH ₃ or CH ₂ -C ₆ H ₅ and

R ²

represent H or SO ₂ -CH ₃ ;

and

wherein

R ³

for NH ₂ , CH ₃ , NH-C ₃ H ₆ -N (CH ₃ ) ₃ ⁺ An ^- , C ₂ H ₄ -N (CH ₃ ) ₃ ⁺ An ^- , CH ₂ -CH (CH ₃ ) -N ( CH ₃ ) ₃ ⁺ An ^- , CH (CH ₃ ) -CH ₂ -N (CH ₃ ) ₃ ⁺ An ^- , C ₂ H ₄ -O-CH (CH ₃ ) -CH ₂ -N (CH ₃ ) ₃ ⁺ An ^- or C ₂ H ₄ -CO-NH-C ₃ H ₆ -N (CH ₃ ) ₃ ⁺ An ^-

and

On ^-

is the anion of a mineral acid, formic acid, acetic acid, lactic acid or ^- O ₃ SOCH ₃ .

The white-tinted plastics contain white-tinted polyacrylonitrile with white tones of the formulas (1) or (2).

The fine-particle white-tinted plastics can be powdered into the paper coating slips be incorporated. In most cases, however, it should be more convenient to use the finely divided plastics before or after the application of the whitener in aqueous Disperse phase and, if necessary, after the white toner is applied has been, the aqueous plastic dispersion obtained in the paper coating slips to incorporate.

These plastic dispersions can A) 1 to 30 wt .-%, preferably 5 to 25% by weight of the whitened polymers, B) 1 to 50% by weight, preferably 5 to 20% by weight of surface-active substances, C) 0 to 15% by weight of preservative and D) Contain 20 to 98 wt .-%, preferably 55 to 90 wt .-% water, with up to Half of the water from hydrotropic substances, e.g. Ethylene glycol or glycerin can be replaced and the percentages are based on the sum of A + B + D Respectively.

Anionic, cationic and / or nonionic can be used as surface-active substances surface-active substances are used, such as in methods of Organic Chemistry (Houben-Weyl), 4th ed., Vol. XIV / I, Georg Thieme Verlag, Stuttgart 1961, p. 190 f. and in DE-A-2 334 769, pages 8 to 10 (GB-A-1 417 071). Dispersions of the invention Fine-particle white-tinted plastics can be used, for example, as follows getting produced:

The powdery polymers are first treated with those for the selected one Suitable white toners in aqueous systems at temperatures from 60 ° C to to the cooking temperature until the whiteners are completely drawn onto the substrate. If necessary, additional aids are used.

However, the white tones can also be melted onto the corresponding ones Polymer materials are fixed.

The amount of white toner used on the substrate depends on the desired lightening effect; it is between 0.01 and 5% by weight of pure active substance, based on the plastic used (solid).

The isolated white-tinted plastic powder is then homogenized after the addition of a surface-active substance and, if appropriate, water, with vigorous stirring. The amount of the surface-active substance can then be increased, if necessary to the total amount required for the stability of the dispersion. The suspension obtained is then comminuted and ground wet. Pre-crushing can be done using stone or tooth colloid mills. The subsequent wet comminution can take place in colloid, vibratory, cone and vibromills as well as in dissolvers or in sub-micron dispersers. However, continuous agitator mills with grinding media, preferably those made of SiO ₂ with a diameter of 0.2 to 5 mm, are preferably used.

After the grinding treatment, further amounts of surface-active agents can optionally be added Substances or hydrotropic substances, preservatives, wetting agents, defoamers and / or water may be added, unless this is at an early stage Time, e.g. before grinding.

The isolated white-tinted plastic powder can also be used after dry grinding can be incorporated directly into the paper coating slips.

A particularly advantageous option is a dispersion of white-tinted plastic The combination of the whitening process and the grinding process represents:

For this purpose, the powdered plastic is comminuted wet together with the corresponding white toner, water and surface-active substances at temperatures from 60 ° C. to the boiling temperature, if appropriate after homogenization and pre-comminution, as described above. The complete brightening takes place during the grinding process in the grinder, preferably in a continuous agitator mill with SiO ₂ grinding media.

The amount of white toner used in the paper coating slip depends on the target White effect. In general, 0.01 to 0.5% by weight of pure white toner is sufficient (based on the solids of the paper coating slip to be lightened). A special The advantage is that, depending on the coating composition, the attainable graying limit is extremely high.

a) 100 bis 150 Gewichtsteile anorganisches Pigment,

b) 3 bis 25 Gewichtsteile Bindemittel, wovon gegebenenfalls bis zur Hälfte aus natürlichem (d.h. nicht-synthetischem) Cobinder (wie z.B. Stärke, Casein) bestehen,

c) bis zu 1 Gewichtsteil Verdicker und

d) bis zu 2 Gewichtsteile Naßfestmittel.

The paper coating slips generally have solids contents of 35 to 80, preferably 40 to 70% by weight. In addition to the white-tinted, fine-particle plastic to be used according to the invention, they generally contain (data in each case based on solids)

a) 100 to 150 parts by weight of inorganic pigment,

b) 3 to 25 parts by weight of binder, of which up to half may consist of natural (ie non-synthetic) cobinder (such as starch, casein),

c) up to 1 part by weight of thickener and

d) up to 2 parts by weight of wet strength agent.

The percentages in the following examples relate to the weight; Parts are parts by weight.

Examples Example 1 White tinted polyacrylonitrile

100 g of polyacrylonitrile powder (®Dralon RK, Bayer AG) are suspended in 11 demineralized water. It is adjusted to pH 2.5 with formic acid. At 60 ° C 0.2, 0.5, 1 or 1.5% whitener of the formula (1) (R = ethyl and An = ^- SO ₃ OCH ₃ ) are added and heated to boiling temperature. The mixture is then stirred at 98 ° C. for 20-40 minutes. It is suctioned off at 60 ° C and the white-tinted powder is dried in a vacuum drying cabinet at 40 ° C. The white tones show the following degrees of whiteness: example 1 WT conc. in % Whiteness Berger CIE a) 0.2 147.4 138.9 b) 0.5 157.4 145.2 c) 1 161.9 151.5 d) 1.5 169.3 151.5

Example 2 Dispersion of white tinted polyacrylonitrile

188 g of the white-tinted polyacrylonitrile powder prepared according to Example 1d (1.5% fixed white toner) together with 140 g dispersant (an ethoxylated Nonylphenol / cyclohexylamine adduct, ®Avolan ONP 100%; Bayer) and 672 g Homogenized water and pre-crushed with a tooth colloid mill. The suspension then gets wet in a bead mill at room temperature with 4 passes crushed. The resulting stable dispersion is easy in paper coating slips incorporate and shows excellent white effects with high light fastness, too even with high additional quantities.

Example 3: Paper coating slip (not according to the invention)

By stirring together 50 Share China Clay SPS, 50 Parts of calcium carbonate (chalk), 12th Parts of an anionic plastic dispersion of a copolymer containing acrylic acid ester with a solids content of 48% (®Acronal S 320 D from BASF), 0.5 Share polyvinyl alcohol and 80 Share water a paper coating slip with a solids content of approx. 55% is produced, the pH of which is adjusted to 9 with sodium hydroxide solution (coating slip 3).

Example 4:

In each 1 kg of the coating color according to Example 3, a) 150 g, b) 300 g and c) 450 g of dispersion according to Example 2 are incorporated.

To produce the coated papers, the coating slips 3 and 4 a) -c) are applied to paper with the aid of a hand-held squeegee or an experimental coating system and dried at 80.degree. Table 2 shows the degree of whiteness CIE of the papers after production and after exposure (1 week in daylight). example White tone usage control in % Whiteness CIE Whiteness drop due to exposure before exposure after exposure 3) without WT 71.4 71 0.4 4 a) 0.037 94.4 93.2 1.5 4 b) 0.065 101.8 100.8 1 4 c) 0.088 107.4 106.1 1.3

The papers according to the invention show a very low concentration of white toner both an increased degree of whiteness and a significantly improved light fastness.

Corresponding amounts can also be produced in the same way as the dispersions white-tinted polyacrylonitrile powder according to Example 1 directly into this coating slip incorporate.

Example 5: White tinted polyacrylonitrile

If the procedure is as described in Example 1, instead of the white toner of the formula (1) (R = ethyl and An = ^- SO ₃ OCH ₃ ), 1% of the white toner of the formula (2) is added (X = CH, R ¹ = methyl, R) ² = SO ₂ -CH ₃ and An ^- = ^- SO ₃ OCH ₃ ) and works as described, you also get polyacrylonitrile powder (whiteness Berger 156, CIE 147.6), which is suitable for the lightening of paper coating slips, in the same way , as described in Example 2, results in a stable dispersion which can easily be incorporated into paper coating slips and which provides excellent white effects with high lightfastness and a high graying limit.

Claims (6)

1. Whitened, finely divided polyacrylonitriles having a particle size of less than 1 µm, the whitener being selected from the series consisting of

   

      in which

   R

   denotes ethyl or phenyl,

   

   in which

   X

   represents CH or N,

   R¹

   represents CH₃ or CH₂-C₆H₅ and

   R²

   represents H or SO₂-CH₃;

      and

   

      in which

   R³

   denotes NH₂, CH₃, NH-C₃H₆-N(CH₃)₃ ⁺An^-, C₂H₄-N(CH₃)₃ ⁺An^-, CH₂-CH(CH₃)-N(CH₃)₃ ⁺An^-, CH(CH₃)-CH₂-N(CH₃)₃ ⁺An^-, C₂H₄-O- CH(CH₃)-CH₂-N(CH₃)₃ ⁺An^- or C₂H₄-CO-NH-C₃H₆-N(CH₃)₃ ⁺An^- and

   An^-

   denotes the anion of a mineral acid, formic acid, acetic acid, lactic acid or ^-O₃SOCH₃.

2. Plastics dispersion containing

   A) from 1 to 30% by weight of a whitened, finely divided plastic according to Claim 1,

   B) from 1 to 50% by weight of surface-active substances,

   C) from 0 to 15% by weight of preservatives and

   D) from 20 to 98% by weight of water, it being possible to replace up to half the water by hydrotropic substances and the stated percentages being relative to the sum A + B + D in each case.
3. Plastics dispersion according to Claim 2, containing

   from 5 to 25% by weight of the component A),

   from 5 to 20% by weight of the component B) and

   from 55 to 90% by weight of the component D).
4. Process for the preparation of the plastics dispersion according to Claim 2, characterized in that the pulverulent plastic, together with the corresponding whitener, water and surface-active substances, is wet-comminuted at temperatures from 60°C to the boiling point, optionally after homogenization and precomminution.
5. Use of the whitened, finely divided plastics according to Claim 1 for whitening paper coating slips based on synthetic binders.
6. Paper coating slips based on synthetic binders, containing whitened, finely divided plastics according to Claim 1.