FI109290B - valve Sack - Google Patents

Description

109290

TECHNICAL FIELD

The invention relates to paper bags and relates to a valve bag with a sealing film.

The sacks according to the invention can be used in particular for storing products which need to be packaged as tightly as possible. The bag material can be re-woven.

TECHNICAL BACKGROUND

10 In the manufacture of paper valve bags, the paper web is formed into a hose, the desired lengths are cut from the hose, and its mouths closed by first folding inwardly narrower end tabs and wider side tabs over them. Other than the valve ends, the side strips are attached to the end strips. A separate paper shaped valve body can be added to the valve end. Further, the valve 15 may have a sealing tag which, after filling the bag, is pivoted and secured over the mouth of the valve to the bottom of the bag.

Moisture-proof valve sacks are made of plastic film-coated paper, ···. variant. In particular, polyethylene has been used as the plastic. Such a bag material is unsuitable for making recycled paper. Namely, when repenting, the plastics remain large particles and it is very difficult to separate them from the pulp. In paper making, these particles melt when the paper web is dried by heating.

Molten, sticky plastic anes will cause difficulties in the process. In addition, holes in the paper are formed at the melted beads.

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FI-C-90520 discloses a valve bag with a valve mouth closure. ·. After filling, the mouthpiece is turned over to prevent the inside. leakage of crack material through the periphery of the valve.

. j · Patent publication FI-C-92922 discloses a moisture-proof sacking paper which is suitable for application. also for recycled paper. Its moisture barrier layer contains modified; Starch and a synthetic polymer. The starch can be modified so that 1 ·. · '30 synthetic polymer is grafted onto it. The grafting can be carried out by emulsifying the monomer solution in the presence of starch. Chopped starch can be used as starch. The synthetic polymer may contain a styrene-butadiene copolymer or a vinyl acetate-acrylate copolymer.

2 109290

GENERAL DESCRIPTION OF THE INVENTION

A paper bag according to claim 1 has now been invented. Preferred embodiments of the invention are set forth in the other claims.

5 The outer layer of the bag has a barrier layer that prevents, for example, moisture or grease from penetrating. This barrier layer is degradable, allowing the bag to be re-fiberized. The sealing layer is also best heat-sealable.

When the bag material is re-fiberized, the barrier layer is dispersed in its fibrous mass, and no harmful plastic particles are formed. A further advantage is that the barrier layer ha-10 is also bioavailable faster than fully synthetic plastics.

When the layers of the bag are of pulpable material, the bag is also suitable for the production of recycled paper. The barrier layer may contain, in particular, modified starch and a synthetic polymer. In particular, the starch may be modified by grafting a synthetic polymer thereon. The grafting can be carried out, in particular, by polymerizing the monomer solution in the presence of starch with emulsion 15. Particularly chopped starch can be used as starch. In particular, the synthetic polymer may comprise a styrene-acrylate copolymer or an acrylate copolymer.

j The bag has a heat sealable valve. The valve is closed with a hot valve! on land, the inside of the valve channel closed or by folding the valve over the mouth. '· 20 patch that is heat sealed to the bottom. This also makes the valve completely sealed.

• · The sacks can be manufactured with conventional bag making line hose and bottom machines without additional units. No additional material is required.

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25 DRAWINGS

: '' The accompanying drawings are a part of the specific description of the invention. In the drawings, v · - Fig. 1 shows the closure bottom of the sack blank, which is marked with dotted lines, • · ·. Fig. 2 shows the bottom with the strips folded in part and * · '30 - Fig. 3 shows the bottom after filling the sack.

3 109290 DETAILED DESCRIPTION Manufacture of barrier material

The barrier layer is composed of a mixture of modified starch and synthetic polymer. The modified starch may be, for example, a graft polymer having polymer chains formed of synthetic polymers covalently attached to the starch backbone. For example, the polymer may contain styrene and alkyl acrylate or copolymers of various alkyl methacrylates or alkyl acrylates.

In particular, starch may be of small molecule, for example, cleaved by oxidation. Cleavage can also be performed as a first step in the grafting reaction. The aim is to keep the degree of cleavage as constant as possible.

The dispersion is best prepared by emulsion polymerization of monomers in the presence of starch to form both a synthetic polymer and grafted starch. Conventional auxiliaries such as initiation and surfactant may be used in the polymerization.

In the heat-sealing moisture barrier layer, the starch is present in an amount of up to about 40% of the dry weight of the coating composition, such as 10 to 40%, in particular 20 to 30%.

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An excipient such as talc, calcium carbonate or a filler may also be used in the mixture. 1> 20 kaolin. The filler content of the mixture is up to 40%, such as 10-40%, special. 20-30%. In particular, the filler is used to reduce the adhesion of the coated paper wrapped.

Example 1. Styrene Butyl Acrylate Starch Copolymer 1 · 118 * g of native starch (moisture content 16%) is slurried in 220 g of water. To the suspension is added 0.05 U / g of B. licheniformis heat-stable alpha-1 'amylase (activity 984 U / ml). At the same time, the temperature of the suspension is raised well with stirring gradually to 90 ° C and maintained at 30 mion. Add 0.5 ml of 30% by volume. of hydrogen peroxide solution and lower the temperature to 60 ° C. The mixture is fed to '· · ·. nitrogen stream, add 0.2 g of CUSO4 and add 50.8 g of styrene, 30 101.6 g of butyl acrylate and 6 g of 30% hydrogen peroxide solution over 1.5 hours. The reaction is allowed to proceed for a further 2 hours, after which time the white dispersion obtained is cooled to 4109290 at room temperature. The dispersion has a viscosity at 25 ° C of 1600 mPas and a solids content of 51%.

Example 2. Methyl Methacrylate Butyl Acrylate Starch Copolymer

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

Manufacture of coated sack paper

The desired amount of dispersion is applied to the surface of the paper and dried to form a barrier layer. The properties of the layer, such as vapor permeability, can be adjusted by changing the composition and thickness of the layer 10. For example, a wax dispersion may be used as an additive. Suitable water vapor permeability for conventional sack material may be, for example, about 20 g / m 2 / day.

The coating may be carried out in particular as disclosed in FI-C-92922.

The barrier layer is best formed only on one side of the paper. In this case, it is good to mechanically bend (i.e., break) the film before making the sack to prevent curling.

Manufacture of valve sacks . The valve bags according to the invention may be made as described above from coated paper using conventional manufacturing techniques. : ..: 20 the barrier layer can be left between the paper layers. Particularly suitable is a double layer ....: sack with a moisture barrier layer on the inner surface of the top layer.

! The following describes, by way of example, in particular, the manufacture of a double-layered sack with reference to the accompanying drawings.

Prepare a double layer sack with a conventional inner layer of relatively high degree of care. 25 sizes of sack paper and outer layer of barrier paper. The barrier layer is on the inner surface of the outer layer.

'· · -. The paper webs are folded inside each other and glued together as a hose. The end of the blank cut from the paper hose 'i' by a hose machine is closed by a bottom machine. It forms ::: diagonal extrusions 3 extending from the edges 1 to the end 2 of the blank, transversal central 10929290 4, folding the bottom end strips 5 inwardly along the diagonal extrusions and forming transverse lateral extrusions 6.

The end strip 5 of the blank has a cut 7 extending from the end 2 of the blank 2 to the diagonal opening 3 perpendicularly to the diagonal opening 3. An inner adhesive strip 10 is formed on the inner surface of the side strips 9 and 9 'and on the outer surface of the end strips 5 extending from the side edge of the additional strip 8 to the side opening 6. In addition, the side strip 9' form a coherent area. A separate valve 12 is glued to the end strip 5 on the valve side

When the side strips 9 and 9 'are folded, the end strip 10 attaches the side strips to the end strip 5 or the valve 12 respectively, also sealing the structure well at the side joint 6. In addition, the adhesive applied to the surface of the end adhesive strip seals the edge of the cut 7 by penetrating between the fold layers in the compression direction, thereby preventing material packed in sack 15 from penetrating between the layers. The additional tabs 8 also support and win the sack.

Valve 12 is a bottom wide flattened paper hose. It is made of the heat-sealing paper described above with the coating on the inside of the hose. Its outward facing edge is folded twice by the coating side i | 20 outwards. The inner edge is incised, if desired, on the side facing the inside of the base to form strips 13.

Once the sack is filled, the valve 12 can be closed by heat sealing.

Underneath the mouth of the valve 12, a bottom-wide closure plate 14, which extends beyond the mouth of the valve, is glued to a part of the valve structure. The closure tag 14 is intended to be pivotable over and around the mouth of the filled sack valve 12 against the bottom. Also, the closure sheet is made of the above-described heat sealable paper and is affixed under the valve mouth with the coating side facing up. After filling, the tag is folded over the mouth of the valve and heat-sealed to the bottom.

30 After filling, the bag can thus be completely closed. Heat sealing is easier, more secure and tidy in operating conditions than bonding with a separate glue and gluing device. In addition, the proposed closure technique is more reliable.

6 109290 The strength of the sack can be increased by gluing the layers at certain points together as disclosed in FI-A-945727. Critical points are in particular the end edge and corners of the bottom of the filled bag. Figure 1 shows the adhesive strips 15 and 16 added between the layers to reinforce these areas.

5 The so-called "glue" is usually glued to the bottom. bottom pad 17. The bottom pad 17 here has the best folded edges that come inside.

The multilayer bag can be made permeable to air, particularly as disclosed in FI-A-945831. In this case, the inner layer is a strong air permeable sack paper. Air ducts are formed between the layers so that air entrained inside the sack can escape from the layers when the sack is filled. Air can be removed especially from the edge of the layers in the bottom region, whereby the air channels are preferably longitudinal grooves in the sack. The potential end tag is then glued with separate, particularly longitudinal, strips of adhesive, whereby air entrained by the layers between the layers under the end tag is still well discharged from the bottom 15 at its ends.

All necessary bonding is carried out using degradable, non-woven, non-interfering adhesive, in particular starch adhesive.

Preferably, the sack consists of two layers, but there may be more layers if required.

. If desired, the ends of the layers may be suitably overlapped to further improve the sealing '·':

The sacks according to the invention may be manufactured using conventional sack lines. The required cut 7 can easily be accomplished with conventional modi-fied tools on a base machine in connection with the nailing. · 25 11 is easy to apply as desired with conventional dispensers. No additional material is needed in the manufacturing process and the production is substantially slowed down.

'.. The bags are particularly suited to the packaging of materials which must be as completely isolated as possible from the outside air. The material is then completely protected, for example, from moisture or impurities in the outdoor air. Thus, the sack is well suited for example for storing and transporting foodstuffs. On the other hand, the sack also does not '' turn the material out so it can also be used to store environmentally harmful substances.

Claims (9)

A valve bag comprising a paper-based sheath provided with a degradable closure film and closed bottoms, one of which has a valve through which one can be filled, the bag having a valve which can be closed after the bag has been filled. with heat seal 10 and having - a valve hose (12) which can be sealed with heat seal and consists of defibreable material, or - a sealing flap (14) which, after filling in the bag, can be turned up over the mouth of the bag and secured to the bottom by heat sealing, the closure tab being of defibratable material. f The bag according to claim 1, characterized in that the valve hose (12) or the sealing flap (14) is paper with a heat-sealable coating. 'I t «·» ·. Sack according to claim 2, characterized in that the coating contains starch modified by grafting synthetic polymer and synthetic polymer, and that the starch is at most about 40%, such as 10-40%, especially 20%. 30% of the weight of the coating. , ·. *. Sack according to claim 3, characterized in that cleaved starch is used as •. It's not starch. ::; 5. A bag according to any one of claims 2-4, characterized in that it is synthetic. '·. The polymer contains styrene and acrylate or alkyl methacrylate polymer or alkyl acrylate copolymer. A bag according to any one of claims 1-5, characterized in that the inner layer is of light air-permeable paper and air ducts are formed between the layers so that the air which, when filling the bag inside the bag, can be removed between the layers. . 109290 Bag according to any one of claims 1-6, characterized in that it has a glue-closed bottom with end flaps (5) folded all the way to the diagonal groove (3), and side flaps (9, 9 ') on these folded ends to the transverse lateral groove, that the end flap has a cut (7) extending from the lateral groove (6) to the diagonal groove, and that the additional tab (8) thus formed is folded up before the side flap is folded against the end flap. Sack according to any of claims 1-7, characterized in that the sack's layer is additionally glued together at the bottom edge (15) or hem (16) of the bag. Use of a sack according to any of claims 1-8 for the storage of materials to be protected from the environment or harmful to the environment. > t · ♦ · * «• IMI I« • '* · «·» * · * * * »t k t>« «s l | * • »» «(*! I ·> ·» f f · M M t