SK128399A3 - Valve sack - Google Patents

Abstract

The invention relates to paper sacks and applies to the closing of a valve sack mouth. The valve has a valve tube (12) which can be closed by heatsealing after the filling of the sack, and/or the valve has a closing flap (14) which after the filling of the sack can be folded over the valve mouth and attached to the bottom by heatsealing. Both the valve tube and the closing flap are of material suitable for defibration. The sack is thus made completely tight and can therefore be used for storing both material that must be protected from the outside environment and material that is harmful to the environment. The sack can also be made to be refiberable.

Description

The invention relates to paper bags and is applied to a valve bag equipped with a barrier film. Such bags according to the invention may in particular be used for the storage of products which require as close packaging as possible. The material of the bag may be rewrapped.

BACKGROUND OF THE INVENTION

In the manufacture of paper valve bags, a tube of paper is formed, cut into pieces of the desired length, the ends are closed to form the bottom by first folding the thicker end flaps inwards, and on their surface are wider side flaps. At all ends, except for the valve end, the flaps are connected to the flap tips. The valve end may be supplemented with a separate valve piece made of paper. Additionally, the valve may comprise a shut-off flap which, when the bag is filled, is folded over the valve opening and attached to the bottom of the bag.

The moisture resistant valve bags are made of paper coated with a plastic film. The preferred plastic film is polyethylene. This type of bag material is unsuitable for the production of recyclable paper. In defibrating, plastics tend to form quite large particles, and separating these particles from fiber is very complex. In the manufacture of paper, these particles melt upon thermal drying of the paper web. Molten and sticky plastic material causes processing problems. Furthermore, holes are formed in the region of the molten particles.

The publication FI-C-92922 discloses a moisture-resistant paper bag also applicable to the production of recyclable paper. In this case, the moisture barrier layer comprises modified starch and a synthetic polymer. The starch may be treated by cleaving the polymer into it. The cleavage can be carried out by emulsion polymerization of the monomer solution in the presence of starch. The starch used may be degraded starch. The synthetic polymer may comprise a butadiene-styrene copolymer or a vinyl acetate-acrylate copolymer.

l

12742

SUMMARY OF THE INVENTION

According to claim 1, there is provided a paper bag. Preferred embodiments of the invention are presented in the other claims.

The outer layer of the bag comprises a barrier layer to prevent the penetration of, for example, moisture and grease. This barrier layer is degradable, allowing re-fibrillation of the bag. Preferably, the barrier layer is also capable of being reheated.

When the bag material is refibrated, the barrier layer is dispersed on the fiber and no harmful plastic particles are formed. Another advantage is that the biodegradability of the barrier layer is faster than that of fully synthetic plastics.

Since the layers of the bag form a defibratable material, the bag is also suitable for making recyclable paper. The barrier layer may preferably comprise a modified starch and a synthetic polymer. The starch may preferably be modified by grafting the synthetic polymer. The cleavage can be carried out by emulsion polymerization of the monomer solution in the presence of starch. The starch used may be degraded starch. The synthetic polymer may comprise a butadiene-styrene copolymer or a vinyl acetate-acrylate copolymer.

The bag contains a heat sealable valve. The valve is closed either by closing the inside of the valve channel by heat sealing, or by folding the shutter over the valve opening and attaching the damper to the bottom by thermal sealing. This operation also ensures perfect sealing of the valve.

Overview of the figures in the drawing

The attached drawings form part of the detailed description of the invention. In the drawings, FIG. 1 shows the bottom of the bag gap to be closed and on which the bottom of the folds is marked with torn lines. Fig. 2 shows a bottom with partially folded flaps, and FIG. 3 shows the bottom after the bag is filled.

DETAILED DESCRIPTION OF THE INVENTION

Production of barrier material

The barrier layer is formed from a mixture comprising a modified starch and a synthetic polymer. For example, the modified starch may be grafted

12742 is a copolymer whose polymer chains are formed of synthetic polymers linked by covalent bonds to starch meat. The polymer may contain, for example, styrene and alkyl acrylate or copolymers of various alkyl methacrylates or alkyl acrylates. The starch may preferably be micromolecular, e.g. degraded by oxidation. The degradation may be performed as the first step in conjunction with the cleavage reaction. In this case, attempts should be made to maintain a constant degree of degradation. Of the dispersing monomers, both synthetic polymer and cleaved starch are best produced by emulsion polymerization in the presence of starch. Conventional equipment such as initiators and surfactants can be used in the polymerization.

In the temperature-resistant moisture-resistant barrier layer, the ratio of starch in the coating composition is about 40% at most, for example in the range of 10 to 40%, preferably 20-30%.

A filler such as a powder, calcium carbonate or kaolin may also be used in the mixture. The fill ratio in the composition is at most 40%, for example in the range of 10 to 40%, preferably 20-30%. The use of the filler decreases mainly for bonding the coated paper to the rolls.

Example 1. Styrene-butyl acrylate-starch copolymer.

118.3 g of pure starch (16% moisture content) are washed in 220 g of water. Alphaamylase (activity 984 U / ml) was added to a solution of 0.05 U / starch, gram of B. licheniformis at a constant temperature. Gradually, the temperature of the solution was raised to 90 ° C with vigorous stirring and maintained for an additional 30 minutes. Subsequently, 0.5 ml of 30% hydroperoxide is added and the temperature is lowered to 60 ° C. A nitrogen stream of 0.2 g of CuSCl and 50.8 g of styrene, 101.6 g of butyl acrylate and 6 g of a 30% hydroperoxide solution is added dropwise to the mixture over a period of 1.5 hours. The reaction may be continued for an additional two hours, after which time the white dispersion obtained is cooled to room temperature. The dispersion viscosity at 25 ° C is 1600 mPas and the solids content is 51%.

Example 2: Methyl methacrylate-butyl acrylate-starch copolymer

The polymer was prepared according to Example 1 using methyl methacrylate (50.8 g) and butyl acrylate (101.6 g) as monomers. A pale yellow dispersion is obtained having a viscosity of 1650 mPas and a solids content of 51%.

Manufacture of coated sachet paper

12742

The required amount of dispersion is applied to the paper surface and dried to form a barrier layer. Layer properties, such as vapor permeability, can be controlled, for example, by changing the layer layout and thickness. A suitable complement is, for example, a wax dispersion. The value of a suitable vapor permeability for a conventional bag material may be, for example, 20 g / m ² / d.

The coating may preferably be applied as presented in FI-C-92922.

Preferably, the barrier layer is formed on only one side of the paper. Consequently, in order to prevent the paper from curling, it is recommended to fold the film mechanically (eg by breaking) rather than by industrial processing.

Production of valve bag

The valve bags of the invention may be made of paper coated as described above with conventional industrial manufacturing technology. In the case of multilayer bags, the barrier layer may be placed between the layers of paper. A two-layer bag in which the moisture-resistant barrier layer is placed on the inner surface of the surface layer is particularly suitable.

The following describes the production of a two-layer bag as an example, with reference to the accompanying drawings.

The two-layer bag is made of an inner layer which is made of a conventional, relatively porous bag paper and an outer layer of paper which is provided with a barrier layer. The barrier layer is located on the inner surface of the outer layer.

The paper fabrics overlap each other at their edges and form a tube by gluing. The end of the gap cut from the paper tube by the tube machine is closed at the bottom of the machine. Here, too, diagonal folds 3 are formed which extend from the edges 1 to the end 2 of the gap and the transverse central fold 4, the end flaps 5 at the bottom fold inward along the diagonal folds 4 and thereby create transverse side folds 6.

A cut 7 extending vertically from the end 2 of the gap to the diagonal fold 3 is formed at the end flap 5 of the gap. The extra flaps 8 thus formed on the end flaps 5 are folded open. On the inner surfaces of the side flaps 9 and 91 and on the outer surface of the end flaps 5, an end glue line 10 is formed extending from the side edge of the extra flap 8 to the diagonal fold 6. On the side of the side flap 91

The adhesive lines 10 and 11 on the side of the side flap 91 form a rigid zone. A separate valve 12 is adhered to the top of the side valve end flap 5.

When folding the side flaps 9 and 91, the end glue line 10 secures the side flaps to the end flap 5 or the corresponding valve 12 tightening the structure also in the area of the side folds 6. Further, the adhesive coated on the surface of the end glue line closes the edges of the cut 7 pressing between folds The layers wrapped in the bag do not have access between the layers. Additionally, the extra folds 8 make the bag more stable and thicker.

The valve 12 is actually a flattened paper tube wide by its bottom. It is made of paper that is provided with the thermally heatable coating described above so that the coating is placed inside the tube. The outer edge is folded from two sides, with the paint side on the outside. At the inner edge, if desired, cuts can be made on the side which is placed from the inside of the bottom so that the flaps 13 can be formed.

After the bag has been filled, the valve 12 can be sealed by heat sealing.

At the bottom of the valve opening 12, a shutter flap 14 is glued with a bottom width as part of the valve structure extending outward from the valve opening. The shutter 14 has to be folded over the opening of the filled bag valve 12 by pressing against the bottom and attaching thereto. The shut-off flap is also made of paper provided with the thermal seal coating described above and attached at the bottom of the valve opening with the paint side facing upwards. After filling, the flap is folded over the valve opening and connected to the bottom by a heat seal.

In this way, the bag can be completely closed after filling. Under operating conditions, temperature sealing is much simpler, more reliable than bonding with a single adhesive and gluing device. Additionally, the closing technique presented herein is more reliable.

The strength of the bag can be improved by gluing the layers together in certain zones as presented in the user publication FI-A-945727, especially the end edges and corners of the bottom of the filled bag are critical zones. In FIG. 1, adhesive lines 15 and 16 are added between the layers to strengthen the areas.

Typically, the so-called lower packaging surface 17 is further adhered to the bottom surface. The lower wrapping surface 17 preferably has folded edges positioned inwards.

12742

The multilayer bag may be made airtight during filling, preferably as presented in user publication FI-A-945831. Then, the inner layer is formed of a thick bag paper with good airtightness. Air ducts are formed between the layers, so that air from inside the bag, which becomes trapped between the layers during filling of the bag, can escape. The air may preferably be discharged from the edges of the layers in the bottom zone in which the air channels preferably have the shape of the grooves of the longitudinal bag. In this case, the end flap, if used, is adhered by separate adhesive lines, preferably longitudinal bottoms, thereby ensuring that air coming to the bottom below the end flap from the layers can simply escape from the bottom through the lower tips.

All necessary adhesives are carried out using a degradation adhesive which is suitable for fiberizing, preferably a starch adhesive.

The bags preferably consist of two layers, but multiple layers may be used if desired.

If desired, the ends of the layers may be adapted by a suitable overlapping method for further improved sealing.

The bags according to the invention can be produced on conventional bag lines which are already in use. The desired cut 7 can be easily made by conventional modified tools on the lower machine in conjunction with the bending. The end gluing line 11 is also simply spread in the desired shape by conventional measuring devices. No additional material is needed during production and production does not slow down significantly.

The bags are particularly suitable for packaging such materials that must be insulated from the outside air as perfectly as possible. The material is then completely protected, for example, from being moistened or contaminated by external air. Therefore, the bag is very suitable, for example, for storing and transporting food. On the other hand, since no material will leak from the bag, it can also be used to store agents that are harmful to the environment.

Claims (10)

PATENT CLAIMS A valve bag with a paper jacket as a base, provided with a degradation barrier film and closed bottoms, one of which has a valve at the end through which the valve bag can be filled, characterized in that the bag comprises a heat sealable valve after filling bag. A bag according to claim 1, characterized in that the bag has a valve tube (12) which can be sealed by a heat seal and the valve tube consists of a material suitable for defibrating (fibrillation) or a shut-off flap (14) which the filling of the bag can be folded over the valve opening and attached to the bottom by a heat seal and the valve flap material is suitable for defibrating. A bag according to claim 1, characterized in that the valve tube (12) or the valve flap (14) is in fact a paper having a thermal seal coating. Bag according to claim 3, characterized in that the coating comprises starch, which can be modified by cleaving the synthetic polymer therein, and in that the proportion of starch in the coating weight is at most 40%, in the range of 10 to 40%, preferably 20-30 %. Bag according to claim 4, characterized in that the starch used is degraded starch. Bag according to one of claims 3 to 5, characterized in that the synthetic polymer comprises styrene and acrylate, or an alkyl methacrylate copolymer or an alkyl acrylate copolymer. The bag according to one of the claims 1 to 15, characterized in that the inner layer is a paper having good airtightness and has air channels formed between the layers so that air can form inside the bag, which can escape during the filling. A bag according to any one of claims 1 to 7, characterized in that it has an adhesive-sealed bottom comprising end flaps (S) folded inwardly along the diagonal fold (3) and side flaps (9, 9 ') stacked on the surface of said end flaps. the flaps along the transverse side fold, by having a cut (7) extending from the side fold (6) to the fold at the end flap 12742 diagonal and in that the extra flap (8) so formed on the side flap is folded openly before the side flap is folded against the end flap. Bag according to one of claims 1 to 8, characterized in that the layers of the bag are also glued together in the zone of the end edge (15) or in the bottom corner (16). Use of the bag according to one of claims 1 to 9 for storage material which must be protected from the environment or which may be harmful to the environment.