FI120904B - Use of alum in packaging material - Google Patents

Description

Use of alum in packaging material State of the art

The invention relates to the use of alum in a fiber-based packaging material to increase its resistance to autoclaving.

The use of fiber-based packaging materials in autoclavable packages is known. Ko. For this purpose, the fiber-based packaging material must typically be coated, for example with a polymer coating, to prevent the fiber base from wetting with the effects of the product and / or external moisture, particularly water vapor used in autoclave processing.

Many different coating polymers can be used to seal the packaging material against moisture or water vapor. In addition, the number and strength of the polymer layers may vary depending on e.g. the polymer used. Polyolefins such as Low Density Polyethylene (LDPE) or Polypropylene (PP) are commonly used as moisture barrier and, when imitated as the outermost coating layers, also serve as an effective heat seal polymer. further, polyesters such as polyethylene terephthalate (PET) may be used. Oxygen barrier polymers include, for example, ethylene vinyl alcohol lipolymer (EVOH) and polyamide (PA). Aluminum foil is also commonly used in fiber-based autoclave packages.

* 20 * Fiber-based autoclave packaging, eg can of cardboard, 2

WO01 / 49938, EP 1091043, EP 292975 and EP 275851 disclose crude edge suction in a packaging material which is subjected to sterilization under normal pressure (70 ° C) with hydrogen peroxide solution. Such conditions are substantially milder than autoclaving by pressurized steam.

5 WOO 1/4993 8 further describes e.g. aseptic packaging carton, which was subjected to the COBB test with hot coffee at 84 ° C. However, this test does not detect raw edge absorption as it measures the amount of fluid absorbed / material surface area. At the raw edges, the porosity of the material is multiple and the mechanism of fluid penetration is different from that of the horizontal surfaces of 10 materials.

GB 2,126,260 describes an alkenyl succinic composition which is a reaction product of olefin blends and succinic acid for use in the manufacture of paper as a hydrophobic adhesive. According to the publication, In addition to the adhesive, paper can be added e.g. a cationic agent for controlling the retention of adhesive li-15. Cationic agents include alum, cationic starch, aluminum chloride, long chain fatty amines, sodium aluminate, substituted polyacrylamide, chromium sulfate, animal glue, cationic thermosetting resins, and polyamide polymers.

Purpose of the Invention • ·: .v 20 The object of the invention is to provide a hydrophobic • 1 ϊ.ϊ.ϊ fiber-based material suitable for autoclave packages with excellent hydrophobic adhesion resistance to autoclave conditions.

DETAILED DESCRIPTION OF THE INVENTION • i · • * Φ ·

The invention is the use of alum with a hydrophobic adhesive and a wet bone adhesive to increase the autoclave resistance of fiber-based packaging material under pressure. ***. steam in autoclaving at 120-200 ° C.

In the experiments carried out in connection with the invention, it was found that the heat resistance of the fiber-based packaging was significantly improved by treatment with a hydrophobic adhesive ♦ “1. in addition, 1 to 10 parts by weight of alum was added to the fiber base per 1 part by weight of hydrophobic adhesive. The heat-improving effect of alum is surprising, ♦ · · 1 * · [; 'as it has been used in the paper and board industry in general, for example, to increase the retention of a hydrophobic adhesive in a fiber base.

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Further, the combination treatment of the invention with hydrophobic adhesive and alum was found to significantly reduce water / vapor absorption / penetration of the fiber-based packaging material from the raw edge of the fiber-based packaging (referred to herein as " Thus, the present invention is well suited for heat treatment in autoclave packages.

The terms used in the context of the present application have the following meaning: '' Fiber backing 'refers in particular to a blister pack or board made of bleached pulp, the manufacture of which is well known in the paper industry.

"Autoclaving" means the treatment of packaging, e.g., empty packaging or packaging containing a product (e.g., food), with pressurized steam at a temperature of 120 to 200 ° C, typically 120 to 130 ° C, and typically to a saturated vapor pressure. autoclaving treatment is well known, e.g., in the food and pharmaceutical industries, and, for example, treatment in an enclosed space at about 125 ° C for 20 minutes, 45 minutes or 60 minutes is commercially available. and autoclaving conditions for sterilizing the packaging product are generally known.

* · * A: 20 '' Autoclave Packaging 'means a packaging made of polymer coated fiber base material which is suitable for the autoclaving process described above, i. made water-repellent and heat-resistant, for example, by means of hydrophobic adhesive and coating layers such as polymer coatings: * · *:.

* "*" * T * ·· ** 25 "Hydrophobic Swim" refers to any adhesive that makes a fiber base water repellent or hydrophobic. This Swimwear Group is commonly known in the art as a "sizing agent".

One useful hydrophobic adhesive is a reaction product consisting of succinic anhydride and a mixture of hydrocarbyl or hydrocarbyls, e.g., more than 13 carbon olefins or olefin mixtures. Here yh-; y. teyse concerned. The float is known in the art as an ASA adhesive which is a reaction product of a mixture of succinic anhydride and 13-25 carbon, straight-chain or branched olefins. The olefin moiety may consist of a straight-chain and branched mixture of Cn-C25 alkenes. Preferably, ASA is a so-called.

A swimming pool consisting of 4 alkenyl succinic anhydride, e.g. Q3-C22 alkenyl succinic anhydride, e.g. a commercial ASA product.

A further useful hydrophobic adhesive is the so-called hydrophobic adhesive. an alkyl ketene dimer (AKD) adhesive which is well known in the art. Herein, is meant a hydrocarbyl ketene dimer product formed, for example, from an unsaturated or saturated, linear or branched fatty acid or from a mixture of such fatty acids, e.g. , such as C16, C18, C20 or C22, preferably C16 or C18, or a mixture thereof. In this yh-10 tex. the products are referred to as "alkyl ketene dimer" (AKD) in accordance with industry practice. A preferred AKD adhesive is a commercial product wherein the hydrocarbon chain of the ketene dimer is formed from a mixture of C16 and C16 fatty acids (C16 / C18 AKD).

Thus, both ASA and AKD adhesives can be used commercially available products, which may be in the form of an aqueous suspension or emulsion, and may optionally contain other additives.

Without being bound by any theory, the aluminum and / or calcium compound used in accordance with the invention, e.g. the heat-resistance effect of hydrophobic sizing is probably due to e.g. that the compound deactivates compounds in acid 20 form as impurity in the adhesive.

• · · • · • «!. V The present invention makes it possible to use hydrophobic adhesive in smaller amounts than the prior art to provide good autoclave resistance, thereby providing advantages in the board (or paper) manufacturing process and in the conversion process. For example, as a result of lowering the dosage level of the hydrophobic adhesive, the adhesion of the plastic coatings to the treated fiber base is also improved, which in turn advantageously affects the autoclave resistance of the package.

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The weight ratio of hydrophobic adhesive to alum is e.g. 1: 0.1-1: 7, preferably 1: 0.5-1: 5, * "* · *, more preferably 1: 1-1: 3. One specific example is said adhesive: alum, ·. ratio 1: 2;

* • · · * # 30 The amount of alum can be, for example, 0.1 to 20 kg / t dry fiber base, preferably 1.0 to 10 kg / t dry fiber base.

The amount of hydrophobic adhesive, preferably ASA, added to the fibrous base may be 0.3 to 4 kg / t of dry fibrous base, preferably 0.5 to 1.7 kg / t of dry fibrous base.

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In accordance with the invention, it has also been found that by adding a wet bone and glue to the fiber base, the raw edge absorption of the package can be further reduced. This is a surprising finding as wet bone adhesives have not been previously used in the art. but typically to increase the mechanical strength of the paper or board in its cascade 5 support. It will be known as the "wet strength improving agent".

'' Wet Bread Adhesive '' refers to a well-known swim group known in the art, and thus used to increase / improve wet paper or cardboard strength ("wet strength improving agent"). Such adhesives include e.g. polyamide epichlorohydrin resin (PAAE), urea formaldehyde resin (UF), melamine formaldehyde resin 10 (MF), polyacrylamide / glyoxal condensate, polyvinylamine, polyurethane, polyisocyanate. Preferred adhesives include, for example, PAAE and isocyanate, especially PAAE.

The wet bone adhesive, preferably PAAE adhesive, may be added to the fiber base at 0.2 to 12 kg / t dry fiber base, preferably 0.5 to 6 kg / t dry fiber base, more preferably 1 to 3 to 15 kg / t dry fiber base.

According to the invention, 0.1-5 parts by weight, e.g. 0.5-3 parts by weight, preferably 1-2.5 parts by weight, such as 2 parts by weight, of the hydrophobic adhesive can be used in the packaging material for autoclave packaging. A preferred combination is a combination of PAAE glue and ASA glue used in the weight ratio shown above, for example PAAE.ASA 1: 1.

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In a further preferred embodiment of the invention, the autoclave pack has one or more, possibly pigmented, polymeric layers on the inside and outside of the dry base, as is known in the art. In one embodiment, the packaging mat- ·· · * *,! the rial comprises, respectively, a polymeric heat sealing layer, a white pigmented polymeric layer, a black pigmented polymeric layer, a treated fiber base, one or more polymeric acid barrier layers, a binder layer, a gray pigmented polymeric layer, and a ... .

: * ·]: Materials generally known in the art may be used as polymeric material · ***; 30 pounds. For example, the material of the heat sealing layer is preferably polypropylene (PP), · »·. ·. polyethylene (PE) or a copolymer thereof. The material of the oxygen barrier layer is preferably ethylene vinyl alcohol polymer (EVOH) or polyamide (PA), most preferably EVOH.

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Due to improved autoclave resistance, the proportion of polymer coatings in the packaging material may also be reduced if desired.

The autoclave resistance of the treated fiber base can be further improved by adjusting and / or optimizing its structure during manufacture. The autoclave resistance 5 can thus be increased, e.g., by the degree of refining of the raw material, such as high-consistency refining; fiber bed web calendering / wet pressing; and / or by drying the web, such as Condebelt drying. Furthermore, a filler such as titanium dioxide may be added to the treated fiber base to provide a fiber base which is very resistant to hot, e.g. autoclaving conditions.

Typically, the treatment of a fiber base according to the invention means that the fiber-based packaging material has been treated throughout, i. across the width of the web, with a combination of hydrophobic adhesive, wet bone adhesive and alum. However, the invention also encompasses the ability to perform processing on only a portion of the material, e.g., cutting edges.

The hydrophobic adhesive and alum are preferably added in the amounts indicated above. The addition may be carried out, for example, in a manner known pertaining to the production of paper and board at any stage of the manufacturing process prior to the final drying step of the fibrous base web, however preferably in connection with the fibrous base pulping. before placing the fiber pulp onto the wire, the combination is obtained by including-. . 20 work evenly on the fiber base web formed over the wire. Alternative- *; In particular, the fiber stock can first be formed into a wire base web, followed by a hydrophobic adhesive and alum to be applied to the fiber base rab, e.g., by spraying onto the web. Hydrophobic adhesive and alum can be added at the same or different stages in the fiber base manufacturing process. Thus, alum can be added prior to the addition of hydrophobic glue, at the same time for the v. or after the addition of hydrophobic glue. The total amount of hydrophobic glue used and alum can be added in one process step, e.g., during the formation of the slurry, but it is also possible that one or both of the hydrophobic adhesives used can be added. ** \ of adhesive and compound are added in more than one fiber base manufacturing step. According to a preferred embodiment, a portion of the alum is added prior to the addition of hydrophobic glue and the remainder of the alum. after adding glue.

»» * • ·· • ·. · **. As stated above, wet fiber adhesive is added to the fiber base in the amounts indicated above, whereby the strength of the fiber base under autoclaving conditions can be further improved. The addition can be carried out in a manner known in the art, e.g., in the stock preparation step before the stock is wired. The use of the wet bone adhesive according to the invention makes it possible to produce an autoclave board having a density and porosity gradient that differs from that of a board made with hydrophobic glue alone. The invention thus provides various alternatives to the ones used now for autoclave packaging material. Can be used e.g. lower density board, i.e.. better stiffness is obtained.

Further, the formation of impurities from the hydrophobic adhesive, such as ASA adhesive, which may adversely affect the heat resistance of the packaging material, e.g. first-pass retention.

If desired, the autoclave resistance of the fiber base can be further improved by adjusting the fiber base structure, e.g., by the degree of refining of the raw material (e.g., by high consistency milling), by calendering / wet pressing and / or drying (e.g., Condebelt drying). Furthermore, a filler such as titanium dioxide, e.g. 0.1 to 5% by weight based on dry fiber base, may be added to the treated fiber base to provide a fiber base which is very resistant to autoclaving conditions.

The invention will now be described in more detail by way of examples.

. , Example Section • · · • * · *: * · *: 20 In the examples, the effects of various factors on the raw edge absorption of paperboard were studied. in autoclave.

Autoclave tests were performed on water vapor sterilizing autoclave using: V at about 125 ° C. '' Normal '' autoclaving conditions were performed approx.

O at 125 ° C, 45 min, 100% RH, and '' hard 'at 125 ° C, 60 min, 100% RH. RH = 25 relative humidity. The autoclave treatment also included a step of heating the '' * '· space (about 15 min) and a lowering step (about 20 min).

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In the test, the samples to be tested were coated with a polymer coating on both sides so that only the raw edge was visible from the board. As the raw edge penetration (REP) of autoclave testing, the amount of water f ··. · Was measured. 30 was absorbed into the carton through the edges of the sample. Infiltration was reported per • · · ~ area of the raw edge (kg / m2).

• · • · ·· * 8

The crude edge absorption REP 80 ° C means that the samples were kept in 80 ° C water for three hours, followed by measurement.

SR is the mass drainage resistance according to the Schopper-Riegler method.

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In the examples and comparative examples of the invention, samples of 150 g / m <RTI ID = 0.0> carbon-5 </RTI> made from dry birch sulfate pulp (pulverized with SR to 22) were used on a paper machine using conventional chemicals for board production. The press section was a conventional 3-nip duplex pressed section. The drying section was conventional with steam cylinders. Calendering was performed with a hard nip calender (15 kN / m). For each of the 10 comparative tests, the carton samples to be compared were prepared in the same manner, but differing only in the differences required to compare the composition or manufacturing conditions. Ko. deviations in the sample preparation step and / or composition are mentioned separately for each comparative example. A possible addition of hydrophobic glue, Al / Ca compound, and wet bone adhesive was performed on the stock prior to placing the stock on a wire. Relationships are weight ratios.

Example 1. Effect of the use of alum under autoclave conditions

The pulp board was glued with ASA glue (2.5 kg / t) and PAAE wet bone glue (2 kg / t).

• ·: .v Autoclave Conditions Hard Normal - t »• · · • · ·

20 Raw edge absorption (kg / m2) REP REP REPvesi80C

• · t ASA adhesive: alum ratio 1: 0 9.9 8.1 2.2 ·· · • · · •!! ···. ASA adhesive: alum ratio 1: 1 3.8 1.6 1.3 · · »» · ASA adhesive: alum ratio 1: 2 2.4 1.6 1.4 ··· • · · ·

The test points clearly show a significant * * 25 effect of alum reduction in crude edge absorption. Increasing the amount of alum reduced the autoclave crude: *. * Maturation under '' severe 'conditions even after no improvement was observed under' normal 'autoclaving conditions and conventional tests (REP 80C):; ·. raw edge absorption.

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Example 2. Effectiveness of ASA vs. AKD bonding under autoclaving conditions

The pulp board was glued with equal amounts of AKD and ASA. The ratio of alum to hydrophobic glue at both points was 1: 1. The wet bone adhesive: hydrophobic adhesive ratio was 1: 1. Raw edge absorption was determined under three different test conditions: by immersing the carton samples in water at 80 ° C for three hours and by autoclaving under "normal" and "severe" conditions as described above.

Raw edge absorption REP (kg / m2), 3h, 80 ° C after water treatment AKD bonding (2.5 kg / h) 2.0 ASA bonding (2.5 kg / h) 1.4 10

Autoclave conditions normal tough

Raw Edge Absorption (REP) after Autoclaving (kg / m2) AKD Bonding (2.5 kg / t) 2.3 6.2 ASA Bonding (2.5 kg / t) 1.8 2.3 15 The quantities absorbed into the paperboard through the sample (REP, raw edge penetration) were quite close AKD and ASA glued to each other under "normal" autoclave conditions. In "rough" autoclave conditions, a clearer difference was found in favor of ASA glued board.

Example 3 and 4. Effect of Wet Bond Adhesive (PAAE) on ASA and AKD bonding: In Example 3 and 4, the carton was mass glued with two different amounts of hydrophobic adhesive. The amount of wet glue was constant at all test points.

·· I f · • · / ··. Example 3. Effect of Wet Bone Adhesive (PAAE) on ASA Bonding • · ·· 1

Autoclaving under "normal" conditions Raw edge suction, REP (kg / m2) • · 1 • · *** \ 25 Low ASA level (1 kg / h) 15.7 • ·

Low ASA Adhesive Level (1 kg / t) + Wet Bone Adhesive (2 kg / t) 4.8

Normal ASA bonding level (3 kg / t) 5.4 • · · 30

Normal ASA Adhesive Level (3 kg / t) + Wet Wet Bonding (2 kg / t) 2.7

Example 4. Effect of Wet Bone Adhesive (PAAE) on AKD bonding

Autoclaving under '' normal 'conditions Raw edge suction, REP (kg / m2)

Normal AKD adhesive level (2 kg / h) 9.6

Normal AKD Adhesive Level (2 kg / t) + Wet Wet Bonding (2 kg / h) 5.0 5 Powerful AKD Adhesive Level (3 kg / h) 3.5

Powerful AKD glue level (3 kg / h) + wet glue glue (2 kg / h) 2.0

The results of Examples 3 and 4 also demonstrate the beneficial effect of wet bone adhesive on the autoclave packaging material.

Example 5. Effect of pulping on whole pulp 10 Pulp cone samples were prepared using pulp milling at 25 SR and 30 SR, respectively. ASA glue (2.5 kg / t), alum (2 kg / t) and PAAE (2 kg / t) were used in the board production.

Autoclave conditions tough normal -

Raw edge absorption (kg / m2) REP REP REPvesi80C

15 Pulp Grinding Ratio 25 SR 3.8 1.6 1.3 • · • *! .V Pulp Grinding Degree 30 SR 2.0 1.6 1.4 ··· • · · • *. ·· *. Example 6. Part of the pulp milled further SR to 80 * In the example, low consistency milling was applied to the whole pulp and to the longer pulverized portion. Pulp board samples were prepared using different amounts of pulp having a pulverization rate of 80 SR ('' further pulp pulp '). For board production: * * * used ASA glue (2.5 kg / t), alum (2 kg / t) and PAAE resin (2 kg / t).

• • • • • · · · · · · · · · · · · · · · · · · · · · · · ···

Autoclave conditions tough normal -

Raw edge absorption (kg / m2) REP REP REPvesi80C

Proportion of pulverized powder 0% 3.8 1.6 1.3

Percentage of further ground pulp 5% 2.7 1.7 1.6 5 Percentage of ground pulp 15% 2.3 1.8 1.4

Example 7. Effect of Calendering

Pulp board samples were prepared by compacting the samples at the dry end of the board machine with a machine calender at normal and elevated nip pressure (15 and 30 kN / m). Sealing could also be accomplished by other types of web sealing method 10 (e.g., wet pressing, shoe calendering). ASA glue (2.5 kg / t), alum (2 kg / t) and PAAE (2 kg / t) were used in the board production.

Autoclave conditions tough normal -

Raw edge absorption (kg / m2) REP REP REPvesi80C

Calendering with normal nip pressure 3.8 1.6 1.3 15 Calendering with increased nip pressure 2.8 1.7 1.3. . Example 8. Effect of finely divided filler • · · • · ϊ, ί ,. ' The board used AKD glue (1.5 kg / t) and PAAE resin (1 kg / t).

·· · • · i • * ·

Normal autoclave conditions • ·

: 1: Raw edge absorption (kg / m2) REP REPvesi80C

··· * ·. · ’20 Ti02 dosage 0 kg / t 6.4 1.6 ···, Ti02 dosage 2 kg / t 3.9 1.5 ♦ · * *: ··: Ti02 dosage 4 kg / t 3.4 1.5 • · V · : In pulp board samples, titanium oxide was used as the mineral fines, but other types of fines (eg other papermaking fillers) can be used instead.

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Ml • f • * ··· 12

Example 9. Comparison of autoclave cartons of a condebelt drying machine and a conventional cylinder dryer

Autoclave conditions are normal

Raw edge absorption (kg / m2) REP

5 Normal drying section 1.4-1.6

Condebelt drying section 1.0 -1.2

The Condebelt drying section can also be used to compact the board structure to withstand autoclaving conditions.

The results of the Examples above show that the use of a wet-glue adhesive in the manufacture of au-10 toclaw board can compromise the pulp density and / or porosity requirement.

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Claims (10)

Use of alum with hydrophobic adhesive and wet bone adhesive to enhance autoclave resistance of fiber-based packaging material in autoclaving at 120-200 ° C under pressurized steam. Use of alum according to claim 1, characterized in that one or more layers of polymer are present on the outside and / or inside of the fibrous base and the fibrous base is treated with alum to increase the heat resistance of the packaging material to a weight ratio of hydrophobic adhesive to alum. 1-1: 10. Use of alum according to claim 2, characterized in that the weight ratio of hydrophobic adhesive to alum is 1: 0.1 to 1: 7, preferably 1: 0.5 to 1: 5, more preferably 1: 1 to 1: 3. Use of alum according to Claim 2 or 3, characterized in that the hydrophobic adhesive is an adhesive consisting of an alkylene succinic anhydride (ASA) and / or an alkyl ketene dimer (AKD). Use of alum according to any one of claims 2 to 4, characterized in that the hydrophobic adhesive is an ASA adhesive used in an amount of 0.3 to 4 kg / t dry fiber base, preferably 0.5 to 1.7 kg / t dry fiber base. • V. Use of alum according to any one of claims 2 to 5, characterized in that 1.0 to 20 kg / t of dry fibrous base, preferably 1.0 to 10 kg / t of dry fibrous base are used. • * · · * # S..1 Use of alum according to any one of claims 2 to 6, characterized in that the wet wet glue contains polyamidoamine michlorohydrin resin (PAAE glue), which is used in an amount of 0.2 to 12 kg / t of dry fiber base, preferably 0.5 - 6 kg / t of dry fiber base, more preferably 1 - 3 kg / t of dry fiber base. ··· • * '* ··] 25 Use of alum according to any one of claims 2 to 7, characterized in that the packaging material comprises, in said order, a polymeric heat sealing layer, a white pigmented polymer layer, containing a black pigment. a polymeric layer, a treated fiber base, one or more polymeric oxygen barrier layers, a binder layer, a gray pigmented polymeric layer, and a polymeric heat seal layer. • · • ♦ · * · Use of alum according to any one of claims 2 to 8, characterized in that a filler is added to the fiber layer to increase the heat resistance of the package. Use of alum according to any one of claims 2 to 9, characterized in that the fibrous base is packaging paper or paperboard.