HUT55452A - Method and coating agent for coating paper or cartoon and the produced paper - Google Patents

Abstract

The invention relates to a process for treating paper and cardboard to improve the water vapour- and aroma-proof qualities, the paper or cardboard being coated with a coating agent which contains one or more polymer dispersions, which is characterised in that the coating agent contains a mixture (A, D) of a paraffin dispersion (I) and an aqueous dispersion of carboxylated styrene/butadiene (II). The invention also relates to paper or cardboard produced by this process and to the coating agent.

Description

FIELD OF THE INVENTION The present invention relates to a process for treating paper and cardboard to increase their water vapor and aroma barrier properties, comprising coating the paper and cardboard with one or more polymer dispersions. The present invention relates to paper and board treated by this process.

For some applications, it is necessary to increase the water vapor barrier and aroma barrier properties of the carton, particularly in the packaging industry. For example, paper with a water vapor barrier capacity of 10 g / m 2/24 hours according to DIN 53122 Kiima D should be used for packaging copying papers. This requirement also applies to folded papers where the vapor barrier coating must be dry in accordance with DIN 53122. High water vapor barrier and aroma barrier properties are required, for example, in the packaging of spices.

It is known to coat papers and cartons with polyvinylidene chloride (PVDC) or PVDC blend polymerizates. The required water vapor barrier is achieved by applying PVDC of at least g / m in two work processes. The two workflows are needed to close the pores of the paper.

Due to their chemical composition, PVDC coated packaging materials have the disadvantages already known for chlorine compounds. When burned, hydrogen chloride is formed and there is a risk of the formation of dioxin, a highly toxic substance.

It is an object of the present invention to replace this PVDC with a chlorine-free polymer. It is known that paper is coated with polyethylene or aluminum-polyethylene combination. In addition, the use of polymeric dispersions such as polyvinyl acetate, PVC copolymers, polymethacrylate, polyethylene dispersions is known. However, these coatings do not meet the desired conditions. The coatings either have low water vapor barrier properties or an extremely thick multilayer coating with a total thickness of more than 20 g / m, and in most cases still do not achieve the required water vapor barrier properties, for example in the process described in German Patent Application Publication 27 41 824. They achieve a closing capacity of 15 to 20 g / m / 24 hours and were tested under drier test conditions at 65% humidity instead of the usual 85% humidity.

PVDC2 coatings have also long been used in the packaging of spices. For this purpose, very thick coatings of up to 60 g / m should be applied so that ground spices such as ground cloves can be packaged in an aroma-proof state. PVDC coatings can be replaced by multilayer paper / aluminum / polyethylene systems, but these are expensive.

It is therefore an object of the present invention to provide a coating for paper and board using chlorine-free polymers. The new coating must have the following properties: it must be food grade, non-sticky, odorless, heat-sealable, have good adhesion to hot melt, be completely water-repellent, non-greasy and it must be stable to plasticizers. In addition, flavor packs should not be permeable to oxygen.

In particular, the process according to the invention is characterized in that the coating material is a mixture of a paraffin dispersion and an aqueous dispersion of carboxylated styrene-butadiene. A further feature of the invention is that the coating material also comprises a polymer derived from acrylic acid. In order to increase the aroma barrier properties, the paper according to the invention is first coated with one or more polyvinyl alcohol coatings, after which the aforementioned coating material is applied.

Advantageous features of the invention will be described in the remainder of the specification and in the claims.

The inventive coatings of the present invention may optionally have different dry weight, fineness, porosity, etc. paper and cardboard. The coating is applied by conventional means such as a brush, smoothing knife or reverse engraving machine. The drying may be contact or floating.

The weight of the applied coating is preferably 8 g / m, so a lower water vapor barrier capacity of 10 g / m / 24 hours can be achieved according to DIN 53122 Kiima D.

The coating agent of the invention preferably comprises a mixture of two polymers, preferably a mixture of three polymers, which are in the form of an aqueous dispersion:

I paraffin dispersion

II carboxylated styrene butadiene

Polymer derived from acrylic acid III.

In one embodiment of the present invention, polymer dispersions I and II are commercially available blends containing 6% by weight of a paraffin dispersion I and 24% by weight of carboxylated styrene butadiene II.

This dispersion mixture directly affects the water vapor barrier properties of the treated paper.

The polymer derived from acrylic acid III may be a polyacrylate, thereby increasing the bending strength of the coating and increasing the water vapor barrier properties of folded and rolled papers and cartons. The wrapping materials are known to be folded or wound during packaging, but the wrapping must also be watertight and aroma-proof at these locations. Polyacrylate III may be a commercial product having a solids content of 50%.

Polymer component Δ I is a paraffin with a melting range of 52-56 ° C and an average molecular weight of 1000 (determined by gel permeation chromatography, using polystyrene as a reference).

Component II is a carboxylated styrene-butadiene polymer containing 3 mol% of the carboxyl group, present predominantly as an ammonium salt, and containing 40 mol% of styrene and 57 mol% of butadiene. A special feature of the polymer is that the macromolecule attached to the second double bond of butadiene is spatially cross-linked so that the weight of a single dispersion drop of the compound is a single cross-linked macromolecule. The carboxyl groups are introduced into the polymer chain with acrylic acid. During the drying process, the free carboxyl groups are made available by cleaving the ammonium ion and further cross-linking can take place with the formation of anhydride.

Mixtures of components I and II are hereinafter designated as mixtures A and D.

The polyacrylate (component III) used in the present invention consists of 22 mol% methyl acrylate, 52 mol% ethyl acrylate and mol% butyl acrylate. It has an average molecular weight of 500,000 and is determined by gel permeation chromatography using polystyrene as a reference standard.

The aqueous dispersion of component III having a solids content of about 50% is hereinafter designated as mixture B.

The coating agent may be coated with conventional additives such as one or more volumes of isopropanol, paint, and the like. Isopropanol acts as an antifoam agent.

According to the present invention, a layer of polyvinyl alcohol is applied before the aforementioned coating to ensure aroma sealing. Preferably, the dry weight of the PVA coating is between 15 and 15 g / m. Preferably, the coating is applied in two layers. Different molecular weights can be used, including mixtures of 20,000 and 200,000 molecular weight types. Said polyvinyl alcohols are crosslinked with glyoxal, the aroma barrier is further improved, and it is also possible for the water vapor barrier coating (A + B mixture) to dry continuously. Preferably, the% saponified polyvinyl alcohol type (IV) having an average molecular weight of 23,000 and the 99% saponified type (V) having an average molecular weight of 88,000. Total amount of types (IV) and (V) in aqueous solution

15%, preferably 8%. Preferably, both types are used in the same amounts (hereinafter referred to as mixture (C)).

The aforementioned coating agent for increasing the water vapor barrier capacity is preferably 40 to 60 parts by weight of the mixture (A),

It consists of 3 to 15 parts by weight of mixture (B) and 5 to 60 parts by weight of water. Preferably about 50 parts by weight of mixture (A).

5 to 10 parts by weight of mixture (B) and about 50 parts by weight of water are used. Preferably, the coating is applied to the paper or board in an amount such that it has a dry weight of 8-25 g / m to achieve the aforementioned high water vapor barrier capability. If the requirements are less stringent, the amount of coating agent can be reduced accordingly. The coating may be carried out in a single step or in several steps, i.e. in several layers.

The dry weight of the polyvinyl alcohols is preferably about

2 to 15 g / m, in particular 8 g / m.

The following examples illustrate the invention.

Example 1

The mixture

Mixture B

Water

Dry coating

Example 2

The mixture

Mixture B

Water

Dry coating

Part weight

8-25 g / m ²

Part weight

5-50 ₉

- 25 g / rn

The paper so treated has a water vapor barrier capacity in accordance with DIN 53 122,

According Kiim D <(10 g / m ^z / 24 hours, this value reached is less than the quantity of dry matter.

Example 3

Pre-coating: Blend C, 4% aqueous solution of Type IV compound and 4% aqueous solution of Type V compound in volume% glyoxal 8-15 g / m (dry)

Top Coating: A + B mixture part by weight A part by weight B

5-50 parts by weight of water applied material 8-20 g / m (dry)

Example 4 Cover

Same as Example 3 with the exception of / coating, with the following composition:

parts by weight A parts by weight B

5-50 parts by weight of water applied material 8-20 g / m (dry)

In Examples 3 and 4, the water vapor barrier capacity is <10 g / m / 24 hours according to DIN 53122, Kiima D.

The aroma barrier ability is determined by comparing it with PVDC coated packages. In each case, several grams of spices, such as ground caraway seeds, ground cloves, are sealed in packages and tested for odor development in open air and hermetically sealed bottles using Merkblatt 52, Verpackungsrundschau 7/1986, Procedure A, by our sense organs. The sealed

- 9 samples were completely odorless after several weeks and were at least equivalent to PVDC-coated reference samples.

In another embodiment, the polymer dispersions are known per se. Accordingly, Blend D contains about 8% paraffin and about 39% carboxylated styrene butadiene (IV). Such a dispersion is a dispersion of Schill & Seilacher GmbH & Co. under the trade name UKADUR 9533. This dispersion contains about 45% solids, of which 16% is wax and about 29% is carboxylated styrene-butadiene. The dispersion alone forms only a waxy, waxy coating and is thus unusable. Surprisingly, a good coating agent is obtained by adding to this dispersion an additional dispersion containing a carboxylated styrene-butadiene polymer, such as the dispersion Papierdispersion 7, which is from Prochema Handelsgesellschaft m.b.H. company product.

The dispersion UKADUR 9533 is anionic in commercial product with a pH of about 7.

Papierdispersion 7 is a homogeneous white emulsion with a viscosity of 50-150 (mpa, s) and anionic. It has a styrene content of about 60% and a solid content of about 50%. The particle size is about 0.25 yum.

The following describes coatings of this type.

Example 5 UKADUR 9533 parts by weight Papierdispersion 7 0-50 parts by weight water applied 5-20 g / m (dry)

A polymer derived from acrylic acid is also preferred in the above-described embodiment. It is preferably a styrene acrylic ester polymer (V) in an amount of 0.5 to 2% by weight. Ukadur 3169 from Schill & Seilacher GmbH & Co. is a polymer dispersion consisting of 45% solids and about 16% paraffin, about 1.5% by weight of styrene acrylic ester polymer and the remainder being carboxylated styrene. butadiene. As in the embodiment described above, an additional dispersion containing about 50% by weight of carboxylated styrene-butadiene, Papierdispersion 7 (product of Prochema Handelsgesellschaft m.b.H.) can be added in this case. Such a coating agent is described in the following example.

Example 6 UKADUR 3169 parts by weight Papierdispersion 7 by weight

0-50 parts by weight of water applied material is 5-20 g / m 2

The polymer dispersion UKADUR 3169 has a viscosity of about 3200 cp (Brookfiled) and the product is anionic. The commercial product has a pH of about 9 and a solids content of 46%.

In the examples so far, both the water vapor barrier and the aroma barrier have been found to be advantageous, and the required amount of coating can be easily applied using conventional equipment. thus, coating is significantly cheaper.

According to the examples, the mixture (A, D) which contains about 5-10% by weight of a paraffin dispersion and about

- Contains 45% by weight of carboxylated styrene-butadiene.

Example 7

In the following, the polymer dispersion of the present invention having a higher hardness is described. This has the advantage, among other things, that the coating does not adhere to the back of the paper when the coated paper is wound. Higher coating hardness is preferred for printing and handling of paper.

Composition: 50 parts by weight UKADUR 9533 parts by weight Plextol DV571 parts by weight water applied material 10 - 15 g / m

The Plextol DV571 acrylate used by Röhm is a thermally crosslinked polyacrylate. UKADUR 9533 is a product of Schill & Seilacher GmbH & Co., a

Example 4.

Example 8

Aromatic sealing pre-coat and top coat are prepared with the following composition:

a) Pre-coating: 100% saponified polyvinyl alcohol, low viscosity such as AIRV0L-103 (manufactured by AIRVOL). Application rate: 10 - 25 g / m

b) Coating: 50 parts by weight UKADUR 9533 parts by weight Plextol DV571 parts by weight Papierdispersion 7 applied 10 - 15 g / m ^

The components of the mixture have already been defined above. The resulting coating has a high coating hardness and excellent aroma-

and waterproof.

Example 9

Aromatic and water vapor barrier coatings are prepared with the following composition:

(a) Pre-coating: 40 g water

- 4.5 g polyethylene glycol (manufactured by Höchst)

100 g of 16% polyvinyl alcohol (AIRVOL 103 manufactured by Air-Products)

- 10 g polyacrylate (ERDOSEAL 120, manufactured by Werder, Switzerland)

0.5 - 2 g Glyoxal (a product of BASF, 40% commercial product)

The coating is applied in quantities of 10 - 15 g / m (dry weight) two

layer is applied paper, and dried. b) Coating: 0 to 10 g water 75 g UKADUR 9533 0-10 g WERDOSEAL 120

The coating is applied in a single step in an amount of about 10-15 g / m (dry weight) and thoroughly dried.

The product obtained has excellent water vapor barrier, water vapor barrier capacity <1 g / m 2/24 h (DIN 53 122, Kiima C), oxygen density 1 ml / m 2/24 h (DIN 53 380, dry oxygen), CO ₂ - has a sealing capacity of <1 ml / m / 24 hours (DIN 53 380) and has good aroma-closing and hot sealing properties. Above 120 ° C melt temperature, we can seal 120 pieces of paper per minute.

When sealing, both the pre-coating and the top coating are closed simultaneously. Only a topcoat can be used (so pre-coating 9 «« «♦ ♦ ♦ ♦ ♦ ♦ 4 4 4 ♦ · · · · ·

- 13 nat) if the aroma barrier is not required on a large scale.

With respect to the aforementioned UKADUR 9533 polymer, it is noted that it exhibits good water vapor barrier properties, even when applied to paper at a dry weight of 10-15 g / m, according to DIN 53122. However, this has the disadvantage that the coating is smeared on the back of the other paper when the web is rolled. In addition, the coating is too bursting when applied to paper, for example, when used as wrapping paper. With stronger bending, the coating is damaged and thus the water vapor permeability of the entire package is increased, even though undamaged paper surfaces have the required water vapor permeability.

Also mentioned in the examples is Plextol DV571 acrylate, a

Rohm's product, when applied in large quantities to paper, gives only very poor vapor barrier properties. This is 50 to 100 times worse than the required water vapor barrier capability and is achieved in accordance with the present invention, which is less than 10 g / m. For example, according to DIN 53122, at a moisture content of 75%, only a water vapor barrier capacity of 600 g / m / 24 hours was measured with 18 g / m coating of Plextol DV571. In practice, such a vapor permeability corresponds to an uncoated paper.

It is surprising, therefore, that the acrylate, together with a polymer dispersion such as UKADUR 9533, results in high water vapor barrier properties for paper, even when the paper is folded vigorously. The positive properties of the blend are probably due to the thermal crosslinkability of Plextol DV 571 acrylate.

The mixture of paraffins and styrene-butadiene described at the beginning of this description and in the examples contains chemically cross-linked styrene-butadiene, and a drop of the dispersion behaves essentially like a polymer molecule. The same applies to mixtures with UKADUR 9533.

The above-described coatings not only exhibit beneficial properties with respect to water vapor barrier and / or aroma barrier properties, but are also advantageous in that there is no lubrication, the materials are well-bendable and at low temperatures such as -32 ° C. their flexibility. The cost of coatings is comparable to or better than the cost of PVDC coatings currently in use.

Claims (27)

Claims A process for treating paper and cardboard to achieve a higher water vapor and aroma barrier ability, wherein the paper or cardboard is coated with a coating agent containing one or more polymer dispersions, characterized in that the coating agent is a paraffin dispersion (I) and an aqueous carboxylated styrene. using a mixture (A, 0) of a butadine dispersion (II). The process of claim 1, wherein the mixture (A, D) comprises from about 5% to about 10% by weight of a paraffin dispersion (I) and from about 20% to about 45% by weight of carboxylated styrene-butadiene (II). Process according to claim 1 or 2, characterized in that the mixture (A) comprises about 6% by weight of a paraffin dispersion (I) and about 24% by weight of carboxylated styrene-butadiene (II). The process according to claim 1 or 2, wherein the mixture (D) comprises about 8% paraffin and about 39% carboxylated styrene butadiene. The process of claim 4, wherein the coating agent comprises about 50 parts by weight of a dispersion containing about 45% solids, comprising 16% paraffin (wax) and about 29% carboxylated styrene-butadiene (UKADUR 9533), and it also contains 50 parts by weight of a dispersion containing 50% by weight of carboxylated styrene-butadiene (Papierdispersion 7). · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ··· 6. Αζ 1-5. Process according to any one of claims 1 to 4, characterized in that the paraffin dispersion (I) has a concentration of about 52 to It has a melting range of 56 ° C and contains about 1000 molecular weight paraffin. 7. Process according to any one of claims 1 to 3, characterized in that the dispersion (II) contains a carboxylated styrene-butadiene polymer having a carboxyl group content of about 3 to 8%, predominantly in the form of an ammonium salt, styrene content 40 mole% and butadiene 57 mole% . 8. A process according to any one of claims 1 to 4, wherein the carboxylated styrene-butadiene polymer is spatially cross-linked on the second double bond of butadiene, so that the dispersion drop is preferably a cross-linked macromolecule and the carboxyl groups are introduced into the polymer via acrylic acid. 9. A process according to any one of claims 1 to 3, characterized in that the coating agent further comprises a polymer derived from acrylic acid. The process of claim 9, wherein the polyacrylate (III) is from about 22 mol% methacrylate, It consists of 52 mol% ethyl acrylate and about 26 mol% butyl acrylate, has an average molecular weight of about 500,000 and has a solids content of an aqueous dispersion of polyacrylate (mixture B) of 50%. 11. Process according to any one of claims 1 to 4, characterized in that the coating agent comprises 40 to 60 parts by weight of a mixture (A) consisting of a paraffin dispersion (I) and carboxylated styrene butadiene (II) and 3 to 15 parts by weight of a mixture (B). consisting of polyacrylate (III) and containing from 5 to 60 parts by weight of water. The process according to claim 11, wherein the coating agent comprises about 50 parts by weight of mixture (A) and 5-10 parts by weight of mixture (B) and about 50 parts by weight of water. 13. A process according to any one of claims 1 to 3, characterized in that the coating agent is applied to the paper in an amount of 8 to 25 g / m dry weight. 14. Process according to any one of claims 1 to 4, characterized in that the additives conventional for the coating agent, such as isopropanol, pigments, etc., are used. We are added. 15. A process according to any one of claims 1 to 14, wherein, in order to increase the aroma barrier properties of the paper, a coating comprising one or more polyvinyl alcohols is first applied and a coating agent according to any one of claims 1 to 14 is applied. The process according to claim 15, characterized in that the dry weight of the polyvinyl alcohol coating is between about 5 and 15 g / m, preferably 8 g / m. The process according to claim 15 or 16, characterized in that the polyvinyl alcohol coating is a mixture (C) of various types of fully saponified molecular weight in the range of 20,000 to 200,000, wherein the crosslinking agent is preferably glyoxal. 18. The process of claim 17, wherein the mixture contains 98% saponified polyvinyl alcohol type (IV) with an average molecular weight of about 23,000 and 99% saponified polyvinyl alcohol. type (V) with an average molecular weight of about 88,000. 19. The process according to any one of claims 1 to 3, wherein the polymer derived from acrylic acid is a styrene acrylic ester polymer (V) and is used in an amount of about 0.5 to 2% by weight. 20. The process of claim 19, wherein the coating agent comprises about 50 parts by weight of a dispersion containing about 45% solids. It consists of 16% by weight of paraffin, about 1.5% by weight of a styrene acrylic ester polymer and the remainder of a dispersion containing carboxylated styrene-butadiene (UKADUR 3169), containing 50 parts by weight of a 50% by weight dispersion of carboxylated styrene-butadiene (Papierdispersion 7). . 21. A process according to any one of claims 1 to 4, wherein the coating agent comprises about 50 parts by weight of a dispersion containing about 45% solids, comprising about 16% paraffin (wax) and about 29% carboxylated styrene-butadiene (UKADUR 9533) and 25% by weight of thermally crosslinkable polyacrylate (such as Plextol DV571) and about 40 parts by weight of water. 22. A process according to any one of claims 1 to 3, wherein the polyvinyl alcohol is coated with 100% saponified polyvinyl alcohol (such as AIRVOL 103) in an amount of 10 to 25 g / m ² to increase aroma barrier properties. 23. The method of claim 22, wherein the coating is a mixture of about 50 parts by weight of UKADAR 9533, about 25% by Plextol DV 571, and about 25 parts by weight of Papierdispersion 7. 24. A process according to any one of claims 1 to 4, wherein the precoat is about 40 g water, 3 to 4.5 g polyethylene glycol, about 100 g polyvinyl alcohol (16%), 5 to 10 g polyacrylate (WERDOSEAL 120) and 0.5 to 2 g glyoxal (40%) blend and 0 to 10 g water, about 75 g UKADUR 9533 and A mixture containing 0 to 10 g of WERDOSEAL 120 is applied. Paper or paperboard with enhanced waterproofing properties, preferably having a water permeability of less than 10 g / m / 24h, as measured according to DIN 53122, characterized in that the paper or paperboard is treated according to any one of claims 1 to 24. 26. Paper or paperboard with enhanced water vapor barrier capability and optionally enhanced aroma barrier capability, characterized in that the paper or cardboard according to any one of claims 1-14, 15-20 and 22-24. A process according to any one of claims 1 to 6. 27. A coating agent for increasing the water vapor barrier and aroma barrier properties of paper or cardboard, characterized in that the composition comprises a paraffin dispersion (I) and an aqueous carboxylated styrene-butadiene dispersion (II), (IV) and optionally an acrylic acid polymer (III, V). contains a standing mixture (A, D).