MXPA99004987A - Dual packing material hornea - Google Patents

Abstract

A foodstuff packaging material, capable of producing seals caused by fiber tearing, when it is bonded with other parts of the package, is prepared from a C1S paperboard substrate by applying a base coat to the uncoated surface of the substrate, before applying on the base coat, a coating for contact with food, which serves as a barrier against moisture and which can be sealed. The pre-coating of the substrate improves the retention of the coating, reduces pores and intensifies the adhesion between the barrier coating and the substrate, to achieve the tear seals of the fibr

Description

BODY DUAL PACKING MATERIAL FIELD OF THE INVENTION The present invention relates, in general, to food packaging, and more particularly, to food packaging, which includes a coating that makes contact with the product, which serves as a moisture barrier and which can be sealed, and that it is capable of producing seals of tearing of the fibers, when they adhere together.

BACKGROUND OF THE INVENTION The packaging material of the type described herein preferably comprises a paperboard substrate having a first side to which a suitable coating has been applied to print high quality graphics. These substrates are known in the art as coated substrates on the one hand, or paperboard substrates C1S. It is also known in the art to employ for that packaging material a cardboard substrate to which suitable coatings have been applied in order to print high quality graphics on both sides. These substrates are known in the art as coated on both sides, or C2S paperboard substrates. Obviously, however, it is more expensive to use a C2S substrate than a C1S substrate for using a C2S substrate than a C1S substrate for packaging, such that there is a need in the art to develop a base packing material. to C1S cardboard for the intended purpose. In addition, it has been found that the use of a C2S substrate is less desirable to provide a tear seal of the fibers when the lids and trays prepared from that substrate are thermally sealed to each other, particularly with the use of some materials of barrier. In the case of food packaging, based on cardboard, at least one side of the cardboard substrate is preferably coated on the papermaking machine, with a coating suitable for the printing of high quality graphics. These coatings are usually applied in two steps. First a base coat is applied, and then a top or top coat is applied over the base coat. With reference to compositional analysis, coatings useful for printing high quality graphics generally include a fluidized mixture of minerals such as coating clay, calcium carbonate, and / or titanium dioxide, with a suitable binder such as starch, alcohol polyvinyl, polystyrene or a similar compound. These coatings are generally applied to paperboard in a papermaking machine, during the papermaking process, by typical coating devices, such as roller, bar, air knife, or sheetcovers. The successive densification and polishing of the coated surface, by means of the satin finish, gives a surface finish to a high degree of smoothness and brightness, to achieve a superior surface that allows a high quality printing. In addition, at least one side of the cardboard substrate is also coated with a coating that contacts the product and serves as a moisture barrier, which is capable of being sealed, either by thermal sealing or by the use of microwave energy, after the substrate is converted into food packages. Typical coatings used for this purpose in the past include resins that can be extruded, such as low density polyethylene (LDPE), polypropylene (PP), and polyethylene terephthalate (PET). However, the use of resins that can be extruded, for that purpose, must be done in a separate process that is generally far away from the papermaking machine, where most coatings are applied, resulting in costs increased and greater manipulation. In addition, the use of extruded resins, for the coatings that make contact with the product, generally requires a thick film to achieve the desired results in relation to the protection against moisture barrier and sealing. The coatings that make contact with the product, convenient and effective, can also be applied to a cardboard substrate, with the use of coatings prepared from emulsions such as acrylic emulsions, ethylene vinyl chloride (CLEV), polyvinylidene chloride (CPVD), and PET. However, the application of these coatings in a papermaking machine is not generally carried out due to the high costs associated with small orders and the high speed with which the papermaking machines work. To overcome these and other problems, the method described in U.S. Patent No. 5,418,008 was developed. In accordance with the teachings of the 5,418,008 patent, to a cardboard substrate that has previously been coated by a (C1S) or both (C2S) surfaces, a continuous film of a barrier material is applied which makes contact with the product, resistant to moisture, with a low weight of the coating, in a single step, in a single printing press, at the same time as the substrate is printed and converted into blanks to form food packaging. Unfortunately the practice of the invention described in the 5,418,008 patent has been discouraged due to the poor retention of the coating, drying problems and high coating consumption, particularly with the use of C1S paperboard, and the inability to achieve tear seals. of fibers, consistent, by using the C2S cardboard. Accordingly, the present invention was developed to overcome the problems with the practice of the invention described in the patent 5,418,008 and to improve the same.

SUMMARY OF THE INVENTION U.S. Patent No. 5,418,008 describes a method for manufacturing paperboard-based packaging material, for food products, using as a cardboard substrate, either C1S or C2S, coated with clay. Not surprisingly, the preferred substrate is C2S paperboard, since the amount of the barrier material that makes contact with the product, necessary to achieve adequate barrier properties, is less with the C2S paperboard than with the C1S paperboard. Unfortunately, C2S paperboard is more expensive than paperboard C1S, and in practice, it has been found that the seals between two coated, barrier surfaces made of C2S paperboard are highly dependent on the type of barrier coating used. For example, with the use of an acrylic barrier coating (styrene acrylate), fiber tear seals can be achieved with the use of a C2S substrate, but their use as a packaging material is otherwise unacceptable due to the use of a C2S substrate. because it lacks the flexibility to form trays that can have 180 degree folds. Meanwhile, the ECLV barrier coating, when applied to a C2S substrate, produces poor adhesion which results in the absence of fiber tearing seals, but when applied to the uncoated side of a C1S substrate, you can achieve fiber tear seals. Unfortunately, the combination of ECLV applied to the uncoated surface of a C1S substrate has an unacceptable VTVH (Wet Steam Transmission Rate). In this way, it would be desirable to modify the substrate C1S to solve the problem of the VTVH and at the same time to preserve the adhesion of tearing of the fibers, desired. In this regard, it has been found in accordance with the present invention, that the most cost effective substrate, the C1S board, can be modified to produce an acceptable VTVH and to retain its ability to achieve fiber tearing seals, without unduly increase its cost and without the need to perform additional steps that are not normally associated with the manufacture of the substrate in a papermaking machine or with the application of a barrier coating in a printing press. This result can be achieved by applying to the uncoated side of a C1S substrate, only a base coat, either on the papermaking machine or on the printing press, or on any other suitable coating apparatus, to achieve a surface that adheres well to a subsequently applied barrier coating and thus provides the desired fiber tear seals. It has been found that these seals are successful using either thermal or microwave energy. It is believed that the success of the present invention is based on the fact that by using only one base coat on the other uncoated side of the substrate C1S, a surface is produced which is much rougher than the surface of a C2S substrate. This rougher surface allows the barrier coating to become more firmly adhered to the surface that has applied the base coat, of the C1S substrate, and to achieve the desired fiber tear seals with a good VTVH. In a laboratory experiment, using a 30X magnification, the surface that has only the base coat applied, of a C1S substrate, appeared rougher than the surface, coated twice, of a C2S substrate, and still the VTVH of the substrate C1S, which had the base coat applied, was comparable to that of a C2S substrate. It is believed that the adhesion of the barrier coating to the substrate C1S, which has only the base coat applied, is purely mechanical, given that the surface having the rougher base coat applied, contains exposed fibers from the cardboard, which improves adhesion or mechanical union. In an effort to duplicate this same rougher surface, in a conventional C2S substrate, to improve adhesion with the barrier coating, both steam treatment and corona treatment were tested. However, the corona treatment was ineffective in improving adhesion, and although the steam treatment increased the roughness of the surface, no increase in adhesion to the barrier coating was observed.

DETAILED DESCRIPTION OF THE INVENTION A base coating can be applied to a C1S substrate by application, to the uncoated surface, of approximately 1.36 to 3.63 kg / 278.7 m2 (from 3 to 8 lb / ream, ream size of 278.7 m2 (3,000 ft. squares)) of a base coat. A barrier coating, such as an ethylene vinyl chloride copolymer, ECLV, can be applied over the base coat, applying from 1.36 to 4.08 kg / 278.2 m2 (3 to 9 lb / ream) of ECLV, over the coating of base. The method of the present invention was established in accordance with the following Example. It will be understood that the example is illustrative only and should not present any limitation for the practice of the invention, since it will be understood that various modifications to the invention can be made, substantially within the scope of the appended claims.

EXAMPLE A C1S substrate received a base coat, by application, to the uncoated surface, from approximately 2.27 to 3.63 kg / 278.7 m2 (5 to 8 lb / ream, ream size of 278.7 m2 (3,000 square feet)) , of a base coat. The base coat comprised a 50/50 mixture of coarse calcium carbonate and # 2 clay (such as Atomite PG-3 or Hydrasparse), with small additions of APV (Polyvinyl Acetate) and protein binders (eg NS) 1103 and the Procote 200). A barrier coating, based on ECLV, was applied on the base coat and the coated samples were subjected to a peel test or analysis to determine the degree of adhesion of the barrier coating to the substrate. For this purpose, a slip / detachment analysis apparatus manufactured by Instrumentors, Inc. was used. In the analysis, the barrier coating is stripped from strips of the coated substrate at a constant speed while the effort is measured. The device for measuring force, based on hydraulic and electric transducers, measures the force of detachment in grams. Other samples of a C2S substrate were coated with the same ECLV barrier coating to be used as a control. Samples of the C2S substrate were also treated with corona and vapor, to roughen the surface and perhaps to improve polymer adhesion. The results are shown in the following tables.

Table 1 Laboratory Decay - ECLV Coating Substrate Sample Release Force (grams) C2S 164 C2S (steam treated) 176 C1S (with base coat) - 3.63 kg / 278.7 m2 205 (8 lb / ream) (Release Force - Average of 5 Determinations) Table 2 Press Application - ECLV Coating Substrate Sample Release Force (grams) C2S 207 C2S (treated with 197 crown effect) C1S (with base coating) - 3.63 kg / 278.7 m2 309 (8 lb / ream) (Release Force - Average of 5 Determinations) Table 3 Press Application - ECLV Coating Substrate Sample Release Force (grams) C2S 192 C1S (with 325 base coating) - 3.63 kg / 278.7 m2 (8 Ib / ream) C1S (with base coat) - 2.27 kg / 278.7 m2 Tear Fibers (5 lb / ream) (Release Force - Average of 5 Determinations) (Tear Fibers - Abandoned Test) Table 4 Press Application - ECLV Coating Substrate Sample Release Force (grams) C2S 163 C1S (base coat) - 2.27 kg / 278.7 m2 Tear Fibers (5 lb / ream) C1S Tear Fibers (Release Force - Average of 5 Determinations) (Tear Fibers - Abandoned Test) Table 5 Press Application - ECLV Coating Substrate samples VTVH g / 254 cmz / day (g / 100 plcrVdla) C2S (bar # 18) 6.7 C1S (bar # 18 - with 8.7 base coating) Table 5 (Continued) Press Application - ECLV Coating Substrate samples VTVH q / 254 cm2 / day (g / 100 in2 / day) C2S (bar # 10) 11.6 C1S (bar # 10 - with 14.1 base coating) C1S (bar # 18) over 40 (No pores are shown except for sample C1S - bar # 18) (Analysis performed at 38 ° C, 90% Relative Humidity (RH)) From the above it will be noted that the force required to detach the ECLV coating from the substrate was greater for the C1S substrates that had a base coat applied than for the C2S substrates (treated or untreated). It will also be noted that for the substrate C1S, which has a base coat applied, in Table 3, the tearing of the fibers can be achieved with a base coat of 2.27 Kg / 278.7 2 (5 lb / ream). Finally, as shown in Table 5, satisfactory VTVH values can be obtained with both a C2S substrate and a C1S product with an applied base coat. Although the above description is directed primarily to applications in food packaging, it should be understood that the present invention could also be applied to other packaging applications with cardboard, where barrier properties and / or properties that allow thermal sealing are required. The advantage of the present invention is that the packaging material of the present invention can be manufactured without the use of expensive applications in other types of machines, particularly coating applications obtained by extrusion.

Claims (6)

NOVELTY OF THE INVENTION Having described the above invention, it is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS

1. A packaging material, cardboard, capable of producing seals by tearing fibers, when two surfaces adhere to each other, characterized in that it comprises: (a) a cardboard substrate having two sides; (b) a finishing coating, on one side, to provide a smooth, printable exterior surface; (c) a base coat on the other side, to provide a surface that accepts a top coat that serves as a moisture barrier and that can be sealed; and, (d) an upper coating that serves as a moisture barrier and that can be sealed, on the base coat, to provide a surface that contacts the internal product.

2. The packaging material according to claim 1, characterized in that the base coating comprises from 1.36 to 3.63 kg / 278.7 m2 (from 3 to 8 lb / ream - ream size of 278.7 m2 (3,000 ft2)) of a mixture 50/50 coarse calcium carbonate and No. 2 clay.

3. The packaging material according to claim 2, characterized in that the coating that serves as a moisture barrier, and that can be sealed, comprises 1.36 to 4.08 kg / 278.7 m2 (3 to 9 lb / ream) of a copolymer of ethylene vinyl chloride containing a colored coating.

4. The method of manufacturing a packaging material, cardboard, capable of producing seals by tearing fibers, characterized in that it comprises: (a) selecting a cardboard substrate having two sides; (b) applying a finishing coating on one side, to provide a smooth, printable exterior surface; (c) applying a base coat to the other side, to provide a surface that accepts a final or top coat that serves as a moisture barrier and that can be sealed; and, (d) applying an upper coating that serves as a moisture barrier and that can be sealed, on the base coat, to provide a surface that contacts the internal product.

5. The method according to claim 4, characterized in that the upper coating that serves as a moisture barrier and that can be sealed, is applied to the packaging material in a printing press, at the same time as graphics of the product are printed on the smooth, finished outer surface of the packaging material,

6. The method in accordance with the claim 5, characterized in that the base coating comprises from 1.36 to 3.63 kg / 278.7 m2 (from 3 to 8 lb / ream - ream size of 278.7 m2 (3,000 ft2)) of a 50/50 mixture of coarse calcium carbonate and Clay No. 2.