FI85683C - FOERPACKNINGSEMBALLAGE, ETT FOERFARANDE FOER DESS TILLVERKNING SAMT EN I FOERFARANDET ANVAEND BELAEGGNINGSKOMPOSITION. - Google Patents

Description

85683

PACKAGING WRAP, METHOD OF PREPARATION AND COATING MIXTURE USED IN THE METHOD

The present invention relates to a packaging wrapper formed of a paper, paperboard or similar fibrous material coated with a moisture-forming coating composition 11a containing polyo-fine.

One packaging wrapper is used for large rolls of paper. The wrapper surrounding the roll acts as both a mechanical shield and a moisture shield that keeps the paper's moisture constant. The paper rolls are moved during storage and transport by forklift trucks11a, in which case the wrapper must withstand the mechanical stresses caused by the forceps of the truck pressing around the roll.

One material used in paper roll coatings is pure polyethylene film. Polyethylene provides good moisture protection while maintaining the original moisture level of the paper during storage, but its weakness is that it tears easily. Truck forceps that catch on the roller may cause tears, *. in addition to which they may arise when any other external • · · • · · * object hits the wrapper.

• · • · · · '··' Better mechanical protection is achieved by using polyethylene coated paper as a wrapper. The paper gives the wrapping strength while the polyethylene provides the necessary moisture protection. However, the disadvantage of this solution is that the polyethylene layer • 1j1 coming against the roll. the friction is low, so that the wrap tends to slip when the roll is lifted. It may also happen that a • · ··· 1 truck instead of a roller will lift the cover only.

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The disadvantage of polyethylene in the rolls of paper rolls has continued to be the difficulty in slicing the wrapper at the ends of the roll, as well as the fact that the polyethylene is easily heat sealed. As a result of the latter feature, the wrap is easily welded to the roll in connection with the attachment of the end caps of the roll. Another disadvantage in winter conditions is that the frost lowers the otherwise low coefficient of friction of the polyethylene and at the same time makes the polyethylene brittle.

In order to avoid the above-mentioned drawbacks, the coverings of the paper rolls have been provided with laminate-structured wrappers in which the two layers of paper are fastened to each other by means of a plastic material. The laminate structure prevents heat sealing, eliminates sliding problems due to low friction when handling the roll, but is heavy, difficult to creep and expensive due to its properties.

It is an object of the present invention to provide a novel packaging wrapper comprising a layer of paper, board or the like fibrous material provided with a coating layer of a suitable plastic material. The invention thus avoids the said disadvantages associated with laminated packaging wrappers. The wrapper m'm · according to the invention corresponds in structure to the known polyethylene-coated packaging wrapper, but the disadvantages of the latter are avoided in the invention. piva, a previously known coating mixture- »•• aa la.

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The invention thus relates to a packaging wrapper, characterized in that the coating composition belonging thereto contains isotactic polypropylene and atactic polypropylene or · ...: amorphous polycol-olefin so that the needle penetration of the mixture is in the range from 0.5 to 20 (0 , lmm / 5s). Most preferably, the needle penetration of the mixture is between 0.5 and 5 (0.1 mm / 5 s).

3 85683 that the needle penetration value obtained with pure, crystalline isotactic polypropylene is 0.

A packaging wrapper according to the invention is also characterized in that the coating composition contains at least 50% of an amorphous component which is atactic polypropylene or poly-o (-olefin).

The invention further relates to a method for producing a packaging wrapper, in which a polyolefin-containing coating composition forming a moisture barrier is applied to paper, cardboard or the like fibrous base material. The process is characterized in that the isotactic polypropylene is mixed with atactic polypropylene or amorphous poly-Al olefin so that the proportion of amophoric component in the coating composition becomes at least 50%, and that the resulting mixture is applied in a molten state to the wrapper base material.

The technique for making the packaging wrapper is preferably such that the components of the coating composition are first mixed together as granules, after which the mixture is melted and layered through a nozzle onto a moving material web of paper, board or similar base material.

The invention further relates to a coating composition for use in the process described above, characterized in that it contains isotactic polypropylene mixed with atactic polypropylene or amorphous poly-O (-olefin) such that the proportion of amorphous component in the mixture is at least 50%. the mixture according to the invention contains 50 to 95%, suitably 60 to 80% of atactic polypropylene and 5 to 50%, suitably 20 to 40% of isotactic polypropylene, and optionally waxes and / or resins as additives.

According to the above, the coating composition according to the invention contains, as one component, isotactic polypropylene, which is crystalline polypropylene having a melt index measured according to ASTMD-4 85683 1238 / L of 2 to 200 g / 10 min. In addition to isotactic polypropylene, the blend contains an amorphous polyolefin component, which may be an atactic polypropylene having a melt viscosity of 100 to 500,000 mPa.s, measured as a brookf 1d viscometer at 180 ° C according to ASTMD-3236. The atactic polypropylene is a polypropylene is generally less than 5% and which is separated from the resulting isotactic polypropylene by dissolution. Alternatively, the amorphous component of the coating composition according to the invention may be a poly-α-olefin, suitably -ethylene, -propylene or -butene having a melt viscosity in said range.

The purpose of the wax which may be present in the coating composition according to the invention, which may be e.g. about 10 to 15%, is to control the hardness, tack and friction of the composition. The purpose of any natural resin or synthetic resin present, which may be e.g. about 5%, is again to improve the adhesion of the mixture to the fibrous base material.

One advantage of the packaging wrapper provided in accordance with the invention is that the coating composition has friction which prevents sliding between the paper roll and the coating layer against it when the roll is lifted. With the wrap around the roll. also as several layers between these layers; slip cannot occur. The coating mixture 11e is also characterized in that it is said to be neither brittle nor to lose friction in the cold.

A further advantage of the invention is that the coating composition does not heat seal when attaching the end tags to the ends of the roll of paper to be packaged. In addition, the packaging wrapper according to the invention. is easily whipped, which makes it easier for the end patches to seal tightly to the ends of the roll.

A particular advantage of the method of manufacturing the packaging wrapper according to the invention is that the base material does not require flame or corona treatment prior to application of the coating composition, as is the case when using polyethylene as a coating. The coating composition in the molten state can be led to a slit nozzle with a rotating rod against a moving material web, which presses the coating composition onto the fibrous base material, providing sufficient adhesion without any pretreatment of the base material. A sufficient amount of coating mixture is generally about 15 g / m to achieve a water vapor permeability of less than 25 g / m / 24h measured at 23 ° C at 50% RH according to standards P 448 om-84 and SCAN-P 22, 68 .

By way of comparison, in known laminate-wrapped paper roll packaging wrappers, a coating of 20 to 30 g / m 2 is required to provide a corresponding water vapor barrier.

In addition to wrapping paper or cardboard rolls, the packaging wrapper according to the invention is also suitable for other packaging purposes, such as, for example, rice wrapping for copy papers. Due to its tightness, the wrapper according to the invention prevents the paper from drying out, whereby its moisture level remains unchanged from the paper machine to the user.

In order to illustrate the invention, a method for preparing a packaging wrapper according to the invention is described in more detail below. In this connection, reference is made to the accompanying drawing, which shows the apparatus used in the method.

The apparatus according to the drawing comprises a mixing tank 1 provided with a rotary mixer 2 and a feed opening 3 at the upper end. The components of the coating mixture are fed in granular form from the feed chute 4 through the opening 3 to the tank 1. The coating mixture may consist of e.g. 70% atactic polypropylene and 30% isotactic polypropylene . In the tank 1, the mixer 2 mixes the components together, and at the same time the mixture 5 melts under the effect of the heating resistors arranged in the tank. A suitable melting temperature is about 170 ° C.

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From the mixing unit 1, the molten, homogeneously mixed coating mixture 5 is led via a line 7 with a pump 6 to the hopper 8 of the coating device. The coating device comprises a rotating roll 9 guiding the paper web 10 forming the base material of the packaging wrapper to the nozzle end 11. The molten coating composition 5 is pressed from the hopper 8 by means of toothed rods 12 into a nozzle head feed slot 13 having a width substantially equal to the width of the paper web 10. The nozzle head 11 is provided with a rotating rod 14 over which the coating composition flows into a uniform layer on the paper web 10. The result is a packaging wrapper 15 coated on one side with the coating composition, in which the amount of coating composition is suitably about 15 g / m 2.

The above-mentioned composition of the coating mixture of 70% atactic polypropylene and 30% isotactic polypropylene has been found to be practically good. Other examples of coatings include a coating composition comprising 50% atactic polypropylene, 35% isotactic polypropylene and 15% wax, and a coating composition comprising 70% atactic polypropylene, 15% isotactic polypropylene, 10% wax and 5% resin. However, the composition of the coating composition may vary within the scope set forth in the appended claims.

It will further be apparent to those skilled in the art that the various embodiments of the invention may vary in other respects within the scope of the claims. Thus, according to the invention, the base material of the packaging wrapper can be not only paper, but also any other suitable fiber-based material, such as, for example, cardboard or liner. Also, the coating process is not limited to the procedure according to the example above, but may also be a two-step process, in the first step of which a homogeneous coating mixture is formed, e.g. granulated or blocked, and in the second step of coating, the mixture is granulated or blended. for the base material.

Claims (10)

A packaging wrapper consisting of paper, paperboard or the like fibrous material coated with a moisture-protective coating composition containing polyoxyphin, i.e., the coating composition comprising isotactic polypropylene or polypropylene and an emollient atactivating it. poly-OC-olefin a such that the needle penetration of the mixture is in the range of 0.5 to 20 (0.1 mm / 5 s). Packaging wrapper according to Claim 1, characterized in that the needle penetration of the coating mixture is in the range from 0.5 to 5 (0.1 mm / 5 s). Packaging wrapper according to Claim 1, characterized in that the coating composition contains at least 50% of an amorphous component which is atactic polypropylene or poly-α-olefin. Packaging wrapper according to Claim 3, characterized in that the coating composition contains 50 to 95%, suitably 60 to 80% of atactic polypropylene and 5 to 50%, suitably 20 to 40% of isotactic polypropylene. Packaging wrapper according to one of the preceding claims, characterized in that the coating composition additionally contains wax and / or resin. A method of making a packaging wrapper, wherein a moisture-protective polyolefin-containing coating composition is applied to paper, board or the like fibrous base material, characterized in that atactic polypropylene or amorphous poly-OC-olefin is mixed with isotactic polypropylene or amorphous poly-OC olefin. the proportion of the component in the coating composition becomes at least 50%, and that the resulting mixture is applied in the molten state to the base material of the wrapper. Process according to Claim 6, characterized in that 50 to 95%, suitably 60 to 80% of atactic polypropylene and 5 to 50%, suitably 20 to 40% of isotactic polypropylene are mixed together and applied in the molten state to the base material of the wrapper. 7 85683 Method according to Claim 6 or 7, characterized in that the components of the coating composition are mixed together in the form of granules, after which the mixture is melted and layered via a nozzle onto a moving material web of paper, cardboard or similar base material. Coating mixture for use in a process according to one of Claims 6 to 8, characterized in that the mixture contains isotactic polypropylene mixed with atactic polypropylene or amorphous poly-OC olefin so that the proportion of amorphous component in the mixture is at least 50%. Process according to Claim 9, characterized in that the mixture contains 50 to 95%, suitably 60 to 80% of atactic polypropylene and 5 to 50%, suitably 20 to 40% of isotactic polypropylene, and optionally waxes and / or resins as additives. 9 PATENTKRAV 85683