Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H19/22—Polyalkenes, e.g. polystyrene
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/18—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising waxes

Definitions

• the invention relates to a method for treating paper or cardboard to increase the water vapor and aroma density, the paper or cardboard being coated with a coating agent which contains one or more polymer dispersions.
• the invention further relates to paper or cardboard treated by this method.
• PVDC polyvinylidene chloride
• the required water vapor density is achieved by applying at least 15 g / m2 PVDC in two work steps. The above two operations are necessary to close any pores in the paper material.
• the packaging materials mentioned with PVDC coating have the chemical composition Disadvantage of chlorine compounds. HCl is formed during combustion and there is also a risk of the formation of dioxin - a highly toxic substance.
• the object of the present invention was to replace this PVDC with chlorine-free polymers. It is already known to coat paper with polyethylene or aluminum-polyethylene composites. Furthermore, polymer dispersions, e.g. Polyvinyl acetate, PVC copolymers, polymethacrylate, polyethylene dispersions etc. have been used. However, all of these coatings cannot meet the requirements. Either the water vapor densities achieved are too low or a very thick multi-layer structure of a total of over 20 g / m2 of the coating is necessary, although the necessary water vapor density is usually not achieved. For example, the method according to DE-OS 27 41 824 only achieves a density of 15-20 g / m2 / 24 h, and this even with a drier test climate of 65% RH instead of the usual 85% RH.
• DE-OS 27 41 824 only achieves a density of 15-20 g / m2 / 24 h, and this even with a drier test climate of 65% R
• PVDC coatings have also been used for packaging spices for a long time. For this purpose, however, very high coat weights - up to 60 g / m2 - should be applied, e.g. to pack ground cloves aroma-tight.
• the previously mentioned multi-layer composites of paper / aluminum / polyethylene can replace the PVDC coating, but are very complex.
• the aim of the invention is to provide a coating for paper or cardboard in which the polymers used are chlorine-free.
• the new coating should also have the following properties: food-safe, non-sticky, non-blocking, odorless, heat sealable, good adhesion with hotmelts, completely water-repellent, greaseproof and stable against plasticizers.
• Aroma packaging also requires oxygen tightness.
• the coating composition contains a mixture of paraffin dispersion and an aqueous dispersion of carboxylated styrene butadiene.
• the coating composition additionally contains a polymer derived from acrylic acid.
• the paper according to the invention can first be given one or more lines with polyvinyl alcohol, to which the aforementioned coating agent is then applied.
• the new coatings according to the invention can be applied to any paper and cardboard of various grammages, smoothness, porosity, etc.
• the coating can be done by conventional means such as e.g. Air brush, squeegee or reverse engraving system. Contact or floating drying can be used for drying.
• the line weights are preferably 8 g / m2 or more in order to achieve the required water vapor density of ⁇ 10 g / m2 / 24h according to DIN 53122 Klima D.
• polymer dispersion I and II are already commercially available as a finished mixture, this mixture containing 6% by weight of paraffin dispersion I and 24% by weight of carboxylated styrene-butadiene II.
• This Dispersion mixture directly causes the water vapor density of the paper treated with it.
• the polymer (III) derived from acrylic acid can be a polyacrylate and serves to increase the kink resistance of the coating and thus improves the water vapor density of kinked or folded paper or cardboard samples.
• the packaging material is folded and folded during packaging, so that the required water vapor and aroma density must also be present at the points weakened in this way.
• the polyacrylate (III) is also commercially available with a solids content of 50%.
• the polymer component I mentioned is a paraffin with a melting range of 52-56 ° C. and an average molecular weight of 1000 (determined by gel permeation chromatography, polystyrene being used as the reference standard).
• Component II is a carboxylated styrene-butadiene polymer with 3 mol% carboxyl groups, most of which are in the form of the ammonium salt, and with 40 mol% styrene and 57 mol% butadiene.
• the macromolecule is spatially cross-linked via the second double bond of the butadiene, so that the mass of a single dispersion drop of this compound is present as a single cross-linked macromolecule.
• the carboxyl groups are introduced into the polymer chain by acrylic acid. After elimination of ammonium on drying, the free carboxyl groups are capable of causing further crosslinking via anhydride formation.
• mixture A and D The mixture of components I and II is referred to below as mixture A and D.
• the polyacrylate (component III) further used according to the invention is composed of 22 mol% methyl acrylate, 52 mol% ethyl acrylate and 26 mol% butyl acrylate.
• the average molecular weight is 500,000, determined by gel permeation chromatography with polystyrene as a comparison standard.
• aqueous dispersion of component III with a solids content of about 50% is also referred to below as mixture B.
• the coating agent can be provided with customary agents and additives for application, such as one to several vol.% Isopropanol, pigments etc.
• the isopropanol serves as a defoamer.
• a line with polyvinyl alcohol is applied according to the present invention under the coating described above.
• the line grammage of this PVA line is preferably between 8 and 15 g / m 2.
• the line is preferably applied in two layers. Mixtures of different fully saponified types with molecular weights between 20,000 and 200,000 can be used. Crosslinking of these polyvinyl alcohols with glyoxal brings about a further improvement in aroma tightness and additionally causes the water vapor-tight top coat (mixtures A + B) to dry without cracks.
• a 98% saponified polyvinyl alcohol type (IV) with an average molecular weight of 23,000 and 99% saponified type (V) with an average molecular weight of 88,000 are preferably used.
• the total concentration of both types IV + V in aqueous solution is 5-15% and is preferably 8%. Both types are preferably provided in equal proportions (in the following mixture C).
• the coating agent described above for increasing the water vapor density preferably consists of 40-60 parts by weight of mixture A, 3-15 parts by weight of mixture B and 5-60 parts by weight of water. About 50 parts by weight of mixture A, 5-10 parts by weight of mixture B and about 50 parts by weight of water are preferably used.
• This coating is preferably applied to the paper or cardboard in such an amount that a dry amount of 8-25 g / m 2 results if the above-mentioned high water vapor density is to be achieved. With lower requirements, the amount of coating agent can be reduced accordingly.
• the coating can be applied in one step or with several layers.
• the line grammage of the polyvinyl alcohol is preferably between about 5 and 15 g / m2 (dry weight) and preferably about 8 g / m2.
• the water vapor density in these examples 3 and 4 is ⁇ 10 g / m2 / 24h according to DIN 53 122, climate D.
• polymer dispersions are used which are known per se.
• Mixture (D) then contains about 8% paraffin and about 39% carboxylated styrene butadiene (IV).
• a dispersion is available from Schill & Seilacher GmbH & Co. under the name UKADUR 9533. This dispersion contains about 45% solids, of which about 16% wax and about 29% carboxylated styrene butadiene. However, this dispersion - taken alone - leads to a greasy, waxy stroke character and is therefore unusable.
• a well-suited coating agent is obtained if a further dispersion containing carboxylated styrene-butadiene polymer is added, such as that e.g. under the name "Papierdispersion 7" from Prochema bottlesgesellschaft m.b.H. is available.
• the UKADUR 9533 dispersion mentioned is a commercial product of anionic ionogenicity.
• the pH is around 7.
• the "paper dispersion 7" is a homogeneous white emulsion with a viscosity of 50 - 150 (mpa, s) with an anionic character.
• the styrene content is approximately 60% and the solids content is approximately 50%.
• the grain size is specified at approx. 0.25 ⁇ m.
• the aforementioned UKADUR 3169 polymer dispersion has a viscosity of approximately 3200 cp (Brookfield) and is of anionic ionogenicity.
• the pH value of the merchandise is approximately 9 and the solids content is 46%.
• the mixture (A, D) contains about 5-10% by weight of paraffin dispersion and about 20-45% by weight of carboxylated styrene butadiene.
• the following is a polymer dispersion according to the invention which has an increased coating hardness. This advantageously has the effect, inter alia, that the line does not smear onto the opposite side when the coated paper is being wound.
• the increased line hardness is also advantageous when printing and handling the paper.
• Composition 50 GT UKADUR 9533 25 GT Plextol DV571 40 GT water Line application 10 - 15 g / m2
• the Plextol DV571 from Röhm used here is a thermally cross-linkable polyacrylate.
• UKADUR 9533 is a dispersion from Schill & Seilacher GmbH & Co. with the composition described in Example 4.
• This line gives excellent aroma and water vapor density with increased line hardness.
• the product thus obtained had an excellent water vapor density of ⁇ 1 g / m2 / 24 h (DIN 53 122, climate C), O2 density ⁇ 1 ml / m2 / 24 h (DIN 53 380, dry O2) CO2 density ⁇ 1 ml / m2 / 24 h (DIN 53 380) as well as good aroma density and heat sealability.
• the paper was heat sealable from 120 ° C sealing temperature with cycle times of more than 120 per minute. This heat sealability was provided by the primer together with the top coat.
• the top coat alone i.e. without a primer) can be used advantageously if flavor density is not required to a high degree.
• water vapor density ⁇ 10 g / m2.
• a water vapor density of only 600 g / m2 / 24h was measured, with 18 g / m2 Plextol DV571 being spread.
• Such water vapor permeability corresponds practically to that of a completely uncoated paper.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)

Applications Claiming Priority (6)

Publications (1)

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Cited By (15)

• 1990
  • 1990-04-07 EP EP90106701A patent/EP0393451A1/fr not_active Ceased
  • 1990-04-17 FI FI901928A patent/FI901928A0/fi not_active IP Right Cessation
  • 1990-04-18 HU HU247390A patent/HUT55452A/hu unknown

Non-Patent Citations (1)

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