FI79575B - SAMMANSATT KARTONGMATERIAL. - Google Patents

Description

1 79575

Multipart board material Technical field

The invention relates to a multi-part paperboard material which has a high rigidity, good extraction properties and which substantially does not impart an undesirable odor or taste to liquid foods and which consists of at least three layers. More specifically, the invention relates to a multi-part cardboard material for liquid packages, in particular so-called Gable-Top packages. Examples of Gable-Top packaging are packaging marketed under the trademarks TETRA REX® and PURE PAK

State of the art

Liquid packaging made of cardboard material is currently preferably made of bleached sulphate cellulose. This material 15 has excellent packaging properties but a high price due to the high consumption of raw materials. For packages other than liquid packages, it is common to use multipart materials in which the stiffness of the material has been increased by multilayer structures, corrugation or some other means, and also for liquid packages 20 these principles have been utilized in certain cases.

However, these types of materials have so far not been used for Gable-Top packages because they do not have the properties required for these applications. Such multiparticulate paperboard materials are also known, for example in the form of grooved paperboard 25 with a middle layer of wood chips and / or thermomechanical pulp (TMP) and a surface layer of bleached chemical pulp. However, these ingredients are also not acceptable for liquid foods, especially milk, mineral water and the like.

30 Description of the invention

The object of the invention is to provide a multi-part paperboard material which has the same good packaging properties as homogeneous fully bleached paperboard, but in which the fiber content of wood has been better utilized. In particular, it is an object of the invention 35 to provide a multi-part board material for so-called Gable-Top packages, which require good folding properties, flat surfaces, good light protection and the taste and odorlessness of the material.

These and other objects can be achieved by the means set forth in claim 1. The material has at least one middle layer of TMP-containing cellulosic material, which gives a high bulk density together with good embossing and folding properties. On both sides of the middle layer (s) there is a sulphate cellulose material with substantially higher mechanical properties than the surface layers of the middle layer (s). The primary function of the middle layer (s) is to keep both surface layers separate so that the multiparticulate board material obtains the desired combination of properties, especially for Gable-Top packages. More specifically, the middle layer (s) is made from a blend containing 30-70, preferably 40-60% by weight of CTMP, while the residue is substantially bleached long fiber sulphate cellulose. Preferably, in order to obtain product properties, e.g. to prevent the cracking of paperboard-20 g, the middle ply / middle ply sulphate cellulose contains at least some fraction ground to a higher degree of grinding than the surface ply sulphate cellulose to act as a reinforcement for the board pulp. This reinforcement fraction accounts for 5-20% of the total weight of the middle-25 layers / middle layers. Its degree of grinding is suitably at least 60 ° SR, most preferably 70-80 ° SR, while the degree of grinding of the surface layers of sulphate cellulose is between 20 and 30 ° SR, preferably 22-28 ° SR. Preferably, the surface layers are comprised of bleached sulfate cellulose, preferably long fiber sulfate cellulose. Long-fiber sulphate cellulose means softwood cellulose with a mean fiber length of at least 2 mm.

The density of the middle layer (s) is suitably between 550 and 700 kg / m 3, most preferably between 575 and 675 kg / m 3, with a density of the surface layers suitably between 640 and 750 kg / m 3, most preferably between 660 and 720 kg / m 3.

3,79575 while the degree of grinding of the sulfate cellulose in the surface layers is between 20 and 30 ° SR, preferably 22-28 ° SR.

The various pulps belonging to the layers also contain glue, starch and some retention aid and in amounts 5 known per se. The total basis weight of the material can vary between 200 and 400 g / m 2.

Further aspects and features of the invention will become apparent from the claims and from the following description of a preferred embodiment.

10 Description of a preferred embodiment

The multiparticulate board material was prepared using low cost applications. 2 with basis weights of 255 and 310 g / m 2. In both cases, the second surface layer (outer layer) had a basis weight of 70 g / m 2 and the second surface layer (inner layer) 2 had a basis weight of 50 g / m 2. The surface layers were made of bleached long-fiber sulphate cellulose with a degree of grinding of 24 ° SR (guideline) and a density of about 690 kg / m 2 (average). The middle layer consisted of about 45% CTMPi 55% bleached long-fiber sulphate cellulose with a mixture of 20 Nordic pines (Pinus silvestris) and spruce (Picea abies) as the fiber raw material. Subsequently, about 10% (based on the total weight of the middle layer) of a reinforcing mass with a degree of grinding of 75 ° SR (guideline) was formed. The density of the middle layer was about 625 kg / m 2 (average). The average sulphate cellulose in the middle layer and the degree of grinding were 30 ° SR (guideline). The fiber raw material for CTMP pulp was Nordic spruce (Picea abies).

Claims (3)

1. Laminated paperboard material for liquid packaging, which material has high rigidity, good extraction properties and does not impart undesirable odor and taste to liquid organ-5 materials, the material of which consists of at least three layers, comprising at least one middle layer of high cellulosic material , i.e. low density, and containing a chemically modified thermomechanical mass, the so-called CTMP, and the surface layers on either side of said middle layer (s) 10 of a cellulosic material having a higher strength and toughness than the middle layer (s), the surface layers being mainly sulphate cellulose and the middle layer (s) being preferred. separate the two surface layers, characterized in that the middle layer (s) is a mixture containing 30-70, preferably 40-60% by weight of CTMP, the remainder being mainly bleached long-fiber sulphate cellulose, the surface layers being mainly bleached long-fiber sulphate cellulose , and that the sulphate cellulose of the middle layer (s) contains a fraction corresponding to 5-20% of the total weight of the middle layer (s) and ground to a higher degree of grinding than the sulphate cellulose of the surface layers, acting as a reinforcement of the middle layer (s). 25 Cardboard material according to Claim 1, characterized in that the degree of grinding of the reinforcement fraction is at least 60 ° SR, preferably 70-80 ° SR, the degree of grinding of the sulphate cellulose of the surface layers being 20-30 ° SR, preferably 22-28 ° SR. 30 Cardboard material according to Claim 1, characterized in that the density of the middle layer (s) is between 550 and 700 kg / m 2, preferably between 575 and 675 kg / m 2, and that the density of the surface layers is between 640 and 750 kg / m 2. , preferably between 660 and 720 kg / m 2.