MXPA98006846A - Laminated wrapping paper and process for making my - Google Patents

Abstract

In accordance with the present invention, a wrapping paper comprising a first and a second layer or sheet of paper is provided. Each sheet has an internal surface coated with a barrier coating. The layers are laminated by hot rolling, wherein the barrier coatings are fused together, or by providing a bond between the coated internal surfaces. The amination can be achieved in a selective or discontinuous manner in order to form air pockets within the laminar structure to increase the insulation characteristics of the wrapping paper. A plasticizer is applied to the outer surface of the wrapping paper. Graphic designs or signs can be printed on the external surface to identify the wrapped product or for decoration purposes. The present invention is also directed to a process and apparatus for manufacturing the laminar wrapping paper described herein. The first and second sheet of paper are unrolled and passed through the apparatus to coat one side of each sheet with a barrier coating. An adhesive is applied to one of the coated sides of the sheets to laminate the sheets together, or alternatively, hot lamination is carried out using a hot roll. A plasticizer is then applied to the outer side of the first sheet

Description

LAMINATED WRAPPING PAPER AND PROCESS FOR MANUFACTURING THEREOF Technical Field The present invention generally relates to paper laminates and, more particularly, to laminate paper suitable for packaging food products. BACKGROUND OF THE INVENTION Laminated wrapping paper has a variety of uses in the packaging industry. Many cost effective processes have been developed to produce stable casings consisting of cellulose and metal foil based layers bonded or adhered to it. In the food wrapping industry, and particularly in the case of hot foods, several performance criteria must be met. The envelope must have superior insulation properties in order to keep the heat inside the package for an acceptable period of time. Superior moisture retention is also desirable. In addition, an important criterion is the characteristic of firm rolling - that is, the ability of the wrap once deformed about a food article to resist splitting or unwinding. This performance criterion has been met for the most part in foil and foil-to-paper casings. However, for many applications or situations, the Use of lamella is not desirable. One such circumstance is when microwave heating is contemplated, which is, of course, incompatible with the metal foil. In addition, the lamella is more expensive than paper and as a waste product it does not degrade satisfactorily. But, while paper wraps with paper are often favored, the properties of firm rolling, insulation and moisture retention of such products have been less than satisfactory. As previously indicated, the "natural memory" inherent in the paper tends to cause a laminate of paper with paper to unfold after being wrapped around a food product. With this background in mind, it is an object of the present invention to produce a paper laminate wrapping with paper which emulates the superior performance criteria of the foil wraps. SUMMARY OF THE INVENTION The aspects of the present invention can be summarized as follows. A laminar wrapping paper comprising a first and a second paper layer or sheet is provided. Each sheet has an internal surface coated with a barrier coating. The layers are laminated by hot rolling, wherein the barrier coatings are fused together, or by providing an adhesive between the coated internal surfaces. The lamination can be carried out in a selective or discontinuous manner in order to form air pockets within the laminar structure to increase the insulation characteristics of the wrapping paper. A plasticizer is applied to the outer surface of the first sheet. Graphic designs or signs can be printed on the external surface to identify the wrapped product or for decoration purposes. The present invention is also directed to a process for manufacturing the laminar wrapping paper described herein and the apparatus for carrying out the process. A first and second laminate of paper are unrolled and passed through a coating apparatus to coat one side of each laminate with a coating barrier. The laminates are then laminated either by hot rolling or adhesive application. In hot rolling, a hot roll is used to melt the barrier coatings. Alternately, an adhesive is applied to the winder coated with one of the sheets to laminate them together. A plasticizer is then applied to the outer side of the first laminate. Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view of one embodiment of the present invention illustrating the locations of the various layers and coatings. Figure 2 shows a pattern of adhesive applied to the laminates of the present invention. Figure 3 is a schematic illustrating a process for manufacturing the embodiment of Figure 1. Detailed description of the preferred embodiment While this invention is capable of materializing in many different forms, it is shown in the drawings and the detailed embodiments will be described in detail. Preferred embodiments of the invention in the understanding that the present disclosure is considered as an exemplification of the principles of the invention and is not intended to limit the invention to the illustrated embodiments. Figure 1 shows in cross-section a preferred embodiment of the finished laminar wrapping paper 10 of the present invention. The wrapping paper 10 generally comprises a top and bottom sheet 16, 22, a dual barrier coating consisting of the upper and lower barrier coating layers 28, 30, and a plasticizing layer or film 36. An interior surface 12 of the paper wrapper is exposed to the food product while an outer surface 14 is exposed to ambient conditions. The upper sheet 16 and the lower sheet 22 are paper material based on cellulose and constitute the major structural layers of the paper wrapper 10. The material The film is preferably a machine glaze or MG of basis weight 5.45-9.08 Kg (12-20 lb) with high density and opacity. The internal surfaces 18, 24 of each sheet 16, 22 are respectively coated with a coating barrier layer 28, 30. The preferred barrier coating material is a mixture of paraffin with a paraffin melting point in the range of 127-135. ° F, microcrislin with a melting point between 57 and 71 ° C (135 and 160 ° F, epolina and BHT) Individually, these constituents are known to those skilled in the art and are easily obtainable in the market. hydrocarbon-based wax that is malleable and that increases the property of firm lamination of the paper wrapper 10. Epolina is a polymer selected to increase moisture ntion BHT is an antioxidant that prevents the barrier coating layers from forming. 30 degrade or turn rancid In addition to providing enhanced firmness and ntion characteristics, the barrier coating layers 28, 30 prevent thickening, which and free oils migrate from the wrapped food product to the outer surface 14 of the wrapping paper 10. In effect, the fats and oils are attracted out of the wrapped food product through a capillary or wick action and captured in the lower sheet 22 without affect the outer appearance of the wrapping paper 10. As a result, the ntion capacity of The humidity of the wrapping paper 10 is higher than that of the fluorocarbon-treated laminates of the prior art. The upper and lower laminates 16, 22 are laminated together by means of two alternative techniques. In the first technique, an appropriately selected emulsion adhesive is employed. While in some applications it is advisable to apply the adhesive 31 to a full side of the sheets 16, 22. Figure 1 illustrates a preferred pattern of adhesive application that creates air pockets or dead zones 32. In the second technique, the laminates upper and lower 16, 22 are heat laminated without the use of a separate adhesive. Essentially, the second technique causes fusion of the waxes of the two barrier coatings 28, 30 together, as described below. Lamination with heat results in the creation of air pockets 32 as well. The use of air bags 32 greatly increases the insulation property of the wrapping paper 10. The resulting insulating property is still improved by using dual barrier layers 28, 30 described above, which greatly reduce the air permeability of the sheets 16. , 22 and assure that the air will be trapped within the dead zones 32 at a point not found in prior art structures having a single layer of polyethylene. Figure 2 shows a preferred pattern 34 for adhesive application or hot rolling, although it is understood that other patterns such as a graticule rectangular or other geometric pattern may be appropriate as well. Laminating film 36 is applied to an outer surface 20 of the topsheet 16 to fill voids in the sheet 16. The plasticizer 36 is essentially a wetting agent that contains both water and an evaporation inhibiting agent, and raises the level of humidity of the upper sheet 16 only. A plasticizer 36 comprising 55% water and 45% glycol or glycerin has been found suitable for the present embodiment. However, it is understood that many other kinds of plasticizer compounds can be found to have comparable efficacy without undue experimentation. The plasticizer 36 acts as a stabilizing agent and tends to fill the bricks or voids of the upper cellulosic sheet 16. In addition, the application of the plasticizer 36 essentially creates a tension between the upper and lower sheets 16, 22. These properties, together with those of the dual barrier coating 28, 30, operate to successfully terminate the natural inherent memory in the sheets 16, 22 a thereby dramatically improve the firm rolling property of the wrapping paper 10. In order to improve the appearance of the paper of wrapping 10 or identifying its content, the topsheet 16 may have designs or textual information printed thereon prior to the application of the plasticizer 36.

A preferred method for making the paper 10 will now be described with reference to Fig. 3, which is a simplified diagram representing an apparatus 50 used to process the wrapping paper 10. The upper and lower paper sheets 52, 54 are unrolled from rollers 56, 58. Each sheet 52, 54 has at least one degree of smooth machining or glazed side. Each of the sheets 52, 54 then passes through a respective barrier coating station 60, 62. Each barrier station 60, 62 has a series of cylinders 64 which conduct the coating material from the container trays 66 to the machined-grade side of each laminate 52, 54. The laminates are preferably coated at a rate of 2-4 lb / ream. The coated laminates 52, 54 then pass through a lamination cover 68. The lamination cover 68 applies the pattern of adhesive using a flexographic process are air-entraining die. As an alternative to using the adhesive pattern application, heat lamination can be used where the rolls of the lamination cover 68 is a hot pattern roll 69. The heat of the hot pattern roll 69 melts the barrier coatings 28, 30 between yes according to a pattern 34 similar to that achieved by the application of adhesive, as shown in figure 2. The laminated structure 70 is then sent to a printing unit 72 which contains a number of printing stations 74, wherein the printed material is inked onto the upper laminate 52 of the lamination 70. The lamination 70 passes through a series of dryers 76 and then into a wetting unit 78 where the plasticizer 36 is applied. At this point, the The resulting wrapping paper 10 is ready to be cut, stored or shipped as appropriate. While the specific embodiments have been illustrated and described, numerous modifications come to mind without departing significantly from the spirit of the invention, and the scope of protection is limited only by the scope of the accompanying claims.

Claims (35)

1. CLAIMS 1. A laminar wrapping paper characterized in that it comprises: a first sheet of paper having an outer surface and an inner surface and a first barrier coating on the first inner surface; a plasticizer on the outer surface of the first sheet of paper; and a second sheet of paper having a second inner surface and a second barrier coating on the second inner surface; wherein the first and second internal surfaces are laminated together. The wrapping paper according to claim 1, characterized in that the first and second internal surfaces are laminated by hot rolling. 3. The wrapping paper according to claim 1, characterized in that the first and second internal surfaces are laminated by the application of an adhesive. The wrapping paper according to claim 1, characterized in that the first and second internal surfaces are laminated in a pattern defining a plurality of air pockets between the first and second internal surfaces. 5. The wrapping paper according to the claim 1, characterized in that the plasticizer is a wetting agent that includes water and an evaporation inhibiting agent. 6. The wrapping paper according to claim 5, characterized in that the evaporation inhibiting agent is glycol. The wrapping paper according to claim 5, characterized in that the plasticizer is composed of 55% water and 45% glycol. 8. The wrapping paper according to claim 5, characterized in that the evaporation inhibiting agent is glycerin. 9. The wrapping paper according to claim 8, characterized in that the plasticizer is composed of 55% water and 45% glycol. 10. The wrapping paper according to claim 1, characterized in that each of the first and second laminate has a machine-glazed side. The wrapping paper according to claim 1, characterized in that each of the first and second laminate has a basis weight of 5.45 -9.08 Kg. 12. The wrapping paper according to claim 1, characterized in that the coating of Barrier is a mixture of a wax, a polymer, and an anti-oxidant. 13. The wrapping paper according to claim 12, characterized in that the barrier coating mixture includes microcrislin. 14. The wrapping paper according to claim 12, characterized in that the barrier coating mixture includes paraffin. 15. The wrapping paper according to claim 12, characterized in that the coating mixture includes BHT. 16. The wrapping paper according to claim 12, characterized in that the coating barrier includes BHT. 17. The wrapping paper according to claim 1, characterized in that it also includes dead zones between the first and the second barrier coating. A process for the manufacture of a laminar wrap paper, characterized in that it includes the steps of: driving a first sheet of paper through a first coating apparatus for applying a first barrier coating to a first side of said sheet, - driving a second sheet of paper through a second coating apparatus to apply a second barrier coating to a second side of the sheet; laminate the first and second sides together; and apply a plasticizer to an outer side of the first laminate. The process according to claim 18, characterized in that the laminating step includes employing a hot roll to melt together the first and second barrier coatings. The process according to claim 18, characterized in that the selective lamination is carried out by employing a hot master roll to create a plurality of air pockets between the first and second sides. 21. The process according to claim 18, characterized in that the laminating step includes applying an adhesive to one of the sides. 22. The process according to claim 21, characterized in that the selective lamination is performed by applying a pattern of adhesive to create a plurality of air pockets between the first and second sides. 23. The process according to claim 21, characterized in that the step of applying an adhesive includes a flexographic process using a die design that entraps the air. 24. The process according to claim 18, characterized in that it also includes the step of driving the laminated sheets through at least one dryer. 25. The process according to claim 18, characterized in that it also includes the step of printing ink on the external surface of the first laminate to create an image. 26. The process according to claim 18, characterized in that the printing step is performed using flexographic equipment. 27. The process according to claim 18, characterized in that the barrier coatings applied are a mixture of a wax, a polymer, and an anti-oxidant. 28. The process according to claim 27, characterized in that the applied barrier coating mezcal includes paraffin, microcrislin, epolina and BHT. 29. The process according to claim 18, characterized in that the plasticizer includes water and an evaporation inhibiting agent. 30. The process according to claim 18, characterized in that the plasticizer includes glycol. 31. The process according to claim 18, characterized in that the plasticizer includes glycerin. 32. An apparatus for manufacturing a wrapping paper characterized in that it comprises: a first barrier coating station for applying a first barrier coating to a first sheet of paper; a second barrier coating station for applying a second barrier coating to a second sheet of paper; a lamination cover for laminating the first and second lamina in a laminar structure; a wetting unit for applying a plasticizing film to an outer side of the laminar structure; means for transporting the first and second sheets respectively to the first and second barrier coating stations and to the lamination cover and to transport the laminar structure to the wetting unit. 33. The apparatus according to claim 32, characterized by further includes a printing station for applying ink to the outer side of the laminar structure. 34. The apparatus according to claim 32, characterized in that the lamination cover includes a roller for hot rolling of the first and second sheets. 35. The apparatus according to claim 32, characterized in that the lamination cover is adapted to apply an adhesive between the first and second sheets.