TWI296968B - Polymer-coated heat-sealable packaging material, its manufacturing method and a sealed package manufactured thereof - Google Patents

Description

1296968

The present invention relates to a method of making a heat sealable packaging material in which a polymeric heat seal layer is provided on both sides of a fibrous substrate. The present invention is further directed to a polymer coated packaging material obtained by the method and a package formed by folding and heat sealing thereof. In order to prevent premature deterioration of the product, it is especially necessary to seal the packaging materials used for packaging the food. Packaging for liquid foods (such as dairy products and juices) requires both airtight and water vapor tightness, while some dry foods require only a good seal of water vapor barrier. Unlike the oxygen-tight seal, the water-tight sealability is not only important for protecting the packaged product, but also for protecting the packaging material itself, its fibrous substrate and polymeric coating. Packaging materials in fiber substrates now include multiple layers of different coatings, with different layers performing different functions. Among such coatings, the polymer which forms a good oxygen barrier is especially ethylene-acetol copolymer (Εν〇Η)* polyamine. High density polyethylene (HDPE) provides good water vapor protection as a polymer. In multi-layer coatings, low density polyethylene (LDPE) is often used as a polymer for the uppermost heat seal layer, which also prevents water vapor transmission, although it is not as good as HDPE to prevent penetration. In addition, it may be desirable to have a polymeric binder in the coating of the multilayer packaging material to adhere the layers to each other and to the fibrous substrate depending on the polymer used. In practice, the polymer coated packaging material is always folded into a sealable package by joining to provide a multilayer coating having a bonded oxygen and water vapor barrier layer to the inner surface of the package. The opposite side of the material will be the outer surface of the package. The side has at most a heat-sealable LDPE or corresponding polymer layer that protects against external moisture and enables the packaging to overlap each other in the fold.

1296968 A7 ______B7 V. Description of invention (2) The opposite edges of the distant material are combined. In packaging for liquid products, it is particularly desirable to prevent the packaged product from wetting the fibrous substrate and leaving an outer surface that can be printed and patterned as freely as possible. It has now been noted that placing the polymeric oxygen and/or water vapor barrier layer on the inner surface of the package may result in the outer surface protection of the package remaining only in the heat seal layer. Especially in tropical countries with high temperatures and relative humidity, the most commonly used lDPE is not sufficient to prevent moisture infiltration. The provision of a barrier layer in current packaging materials is also deficient. This material hinders the penetration of water vapor and moisture in different directions and in different ways. A second drawback associated with the HDPE water vapor barrier layer formed by extrusion is the crimping of the coated cardboard, which is caused by post-HDPE crystallization that occurs after extrusion. It is an object of the present invention to solve the problems arising from the current insufficient water vapor barrier of the fibrous base packaging material and thus the combined packaging based on the above observations. The method of the present invention features the manufacture of a packaging material that extrudes a polymeric water vapor barrier layer containing high density polyethylene (HDPE) on both sides of the fibrous substrate to provide a fibrous substrate and an outer heat seal layer in the packaging material. A water vapor barrier layer is left between. The packaging material of the present invention is characterized in that it comprises a fibrous substrate and a high density polyethylene (HDPE), respectively, and serves as an internal extruded polymer layer and an external heat seal layer on both sides of the water vapor barrier layer. The water vapor barrier layer is disposed on both sides of the packaging material in accordance with the present invention to prevent the packaged product from wetting the substrate and preventing moisture from penetrating from the outside of the package. The added water vapor barrier also has such a function that moisture can not affect -5 - the paper size is suitable for the key (CNS) A specification ((10) 297 297 public treasure) 1296968 A7 ___ B7_ five, invention description (3) may be from any The directionally bonded oxygen barrier layer is positioned such that it remains between the two water vapor layers. In contrast to the technical description, the solution of the present invention enhances the prevention of moisture in the package from the outside, even in hot and humid environments, the inner barrier of the packaged substrate cardboard and possibly the package is protected under moisture, thus maintaining The end result is guaranteed to preserve the performance of the food in the package. The present invention also reduces or even completely eliminates the curling problem associated with packaging materials to eliminate the tendency of the HDPe water vapor barrier layer to be crimped on both sides of the fibrous substrate, respectively. When the HDpE layer on the opposite side of the fiber substrate is nearly the same thickness, this achieves at most the side material when the packaging material manufactured according to the present invention is folded into a package, which side material is the outer surface 'Which side material is the inner surface to the water vapor barrier or even What difference might be made. Accordingly, one embodiment of the present invention provides a polymeric heat seal layer on both sides of the fibrous substrate and a barrier layer that prevents water vapor permeation beneath it to make the material structure symmetrical. In this case, the material can be folded and packaged regardless of the barrier properties of the package or other needs. In addition, a significant advantage of the increase is that water vapor has the same permeability in different packaging directions (i.e., 'either entering the package from the outside or oozing out from the inside). The invention is preferably further applied to additionally provide at least one polymeric layer forming an oxygen barrier layer on one side of the fibrous substrate. The packaging material, particularly suitable for use in liquid food packaging, can be folded into a package such that the oxygen barrier layer remains inside the fibrous substrate of the package in a manner known per se. The inner multi-layer coating of the package then forms an oxygen and water vapor barrier layer that protects the product from the outside air. -6 - This paper scales the Common Chinese National Standard (CNS) A4 specification (210 X 297 mm) 1296968

The gas is louder and the protective fiber substrate is not affected by the packaged product. At the same time, the outer barrier layer protects the fiber substrate and the oxygen white's 匕 透 , ,m, the early ritual does not ooze from the outside, therefore, the package is guaranteed Barriers and other properties that are obtained during the required storage period. The water vapor permeability of the intrinsic polyethyl hydrazine (HDPE) used as a water vapor permeable polymer in the octagonal vapor barrier layer is lower than that of the conventional heat sealant. The water vapority of the coating can also be controlled by means of the layer thickness. HDPE in combination with the most common heat sealable polymer LDPE is non-porous in heat sealing. According to the present invention, the weight of the HDPE layer forming the water vapor barrier may be, for example, 5 to 50 g/m2, preferably 7 to 30 g/ Meter 2, the best 1〇 to 20g/m2. The effective water vapor barrier polymer is Borstar-HDPE with a density close to 〇·963 g/m3. A pigment or, for example, a ferrous compound (e.g., FeO) can be held to the water vapor barrier layer to capture oxygen. The preferred polymer of the poly-smoke heat seal layer is a low density polyethylene hydride (LDPE) having a layer weight of, for example, 5 to 50 g/m 2 , preferably 5 to 30 g/m 2 , preferably 7 Up to 20 g / m2. If a second suitable polymer, such as polypropylene or polybutene, is added to the heat seal layer with ldpE, a connection that opens when pulled apart can be obtained. In the present invention, LDPE means a low-density polyethylene phthalate having a density of generally about 〇·92 g/cm 3 and a maximum of 94 g/cm 3 . Polyethylene having a higher density than this is a high density polyethylene (HDPE) associated with the present invention. The EVOH or PA oxygen barrier layer which may be incorporated into the packaging material of the present invention may have a weight of, for example, 3 to 15 g/m2, preferably 5 to 10 g/m2.

This paper scale is applicable to China National Standard (CNS) A4 specification (210X297 mm) A7 B7 1296968 V. Invention Description (5) The packaging material according to the present invention can be formed from packaging cardboard, and the fiber base weight can be 130 to 500 g / The variation between meters 2 is optimal between 170 and 300 g/m2. For example, a three-layer cardboard commonly used, for example, in polymer coated packaging cardboard is suitable for use as a fibrous substrate; in a three-layer cardboard, a thicker layer of chemical thermomechanical pulp (CTMP) is positioned in two layers. Between thin kraft pulp. Further, the present invention includes a wrapper wherein the fiber substrate usually has a weight of from 20 to 120 g/m2, preferably from 40 to 1 g/m2. The sealed package of the present invention is characterized in that the package is formed by folding and heat sealing a packaging material comprising a fibrous substrate and a polymeric heat seal layer on both sides, in which the under the external heat seal layer The fibrous substrate on both sides has a layer of extruded polymer comprising high density polyethylene oxide (HDPE) and acting as a water vapor barrier. The package of the present invention also advantageously includes a polymeric oxygen barrier layer that is retained inside the fibrous substrate of the packaging material (e.g., packaging cardboard or paper). Accordingly, the package includes an oxygen barrier layer, a HDPE water vapor barrier layer, and a heat seal layer that additionally forms the inner surface of the package on its inner surface. The outer surface of the package includes a HDPE water vapor barrier layer and a heat seal layer, and the outer surface of the package may optionally have an oxygen barrier layer. Suitable oxygen barrier polymers are EVOH and PA, and suitable heat sealable polymers are LDPE. The package of the present invention may especially be a can or box package formed from a polymer coated cardboard or a bag formed from a polymer coated paper. In particular, dry and liquid foods can be used as products to be packaged. In the following, the invention will be described in detail by way of examples with reference to the accompanying drawings in which Figures 1 to 9 show the invention as nine different alternative embodiments -8 ** This paper scale applies to the Chinese National Standard (CNS) Α 4 specification (210X297 Love) A7 B7 1296968 V. Description of invention (6) Layer structure of packaging materials. Fig. 1 shows the can package of the present invention which is formed by folding and heat sealing of a cardboard package, and Fig. 11 shows the result of bending measurement in a bar graph. The polymer coated packaging cardboard shown in Figure 1 comprises, in order, an LDPE heat seal layer 1, a HDPE water vapor barrier layer 2, a fiber substrate 5 (for example, consisting of two layers of sulfuric acid pulp layer and a CTMP layer therebetween) The three-layer cardboard), the HDPE water vapor barrier layer 9 and the LDPE heat seal layer 10. LDPE and HDPE 1, 2, 9, and 10 superposed on both sides of the fiber substrate 5 are formed by co-extrusion. The weight of the fibrous substrate 5 is, for example, 250 g/m2, and the weight of both HDPE layers 2 and 9 is, for example, 15 g/m2, while the weight of both LDPE layers 1 and 10 is (for example) ) 1 5 g / m 2 . Therefore, the cardboard has a completely symmetrical structure, in which case one of the LDPE layers 1 and 10 may be the outer surface of the package to be folded from the cardboard, and the other layer may be the inner surface. This cardboard is especially suitable for packaging dry foods in countries where the climate is warm and humid. The packaging cardboard shown in Fig. 2 comprises, in order, an LDPE heat seal layer 1, an HDPE water vapor barrier layer 2, a fiber substrate 5, an EVOH oxygen barrier layer 7, an adhesive layer 8 (for example, grafted polyethylene), HDPE water. Vapor barrier layer 9 and LDPE heat seal layer 10. The polymer layers on both sides of the fibrous substrate 5 are produced by co-extrusion. The weight of the LDPE, HDPE and fibrous layers 1, 2, 5, 9 and 10 may correspond to the cardboard of Figure 1, respectively. The weight of the EVOH layer 7 can be, for example, 5 g/m2, and the weight of the adhesive layer 8 can be, for example, 5 g/m2. Cardboard means that it will be folded into a package such that the first mentioned LDPE layer 1 is the outer surface of the package, and the latter mentioned LDPE layer 10 is the inner surface of the package, in which case -9 - the paper size applies to China National Standard (CNS) A4 Specification (210 X 297 mm)

Cambodia

1296968 A7 B7 V. INSTRUCTION DESCRIPTION (7) The EVOH oxygen barrier layer 7 appears in the interior of the fibrous substrate 5 in the package. The cardboard is particularly suitable for packaging liquid foods such that the HDPE layers 2 and 9 on either side of the fibrous substrate impart the necessary protection to the other layers of the cardboard, while the EVOH layer 7 forms an oxygen barrier layer that protects the product. The packaging board according to Fig. 3 differs from that shown in Fig. 2 only in that a PA layer 6 is provided instead of EVOH as an oxygen barrier. The suitable weight of the PA layer 6 is, for example, 7 g/m2. A further embodiment of the cardboard of the present invention is further illustrated in Figure 4, wherein the oxygen barrier layer is formed by superimposed PA and EVOH layers 6 and 7. The weight of the two layers 6 and 7 can each be 5 g/m2. In the cardboard according to Fig. 5, the oxygen barrier layer 7' is a mixture of EVOH and PA. Figure 6 shows a package cardboard comprising, in order, an LDPE heat seal layer 1, a HDPE water vapor barrier layer 2, an adhesive layer 3, an EVOH oxygen barrier layer 4, and a fiber substrate 5 (this layer is similar to Figure 1 The three-layer cardboard of the specific embodiment), the EVOH oxygen barrier layer 7, the adhesive layer 8, the HDPE water vapor barrier layer 9, and the LDPE heat seal layer 10. The polymer layers on both sides of the fibrous substrate 5 are preferably produced by co-extrusion. The weight of each layer is, for example, the following: fiber base 250 g / m 2 , LDPE layer 15 g / m 2 , HDPE layer 15 g / m 2 , EVOH layer 5 g / m 2 , adhesive layer 5 g / m 2 . Therefore, the cardboard is a symmetrical structure, and when folded into a package, either side may be the outer surface of the package and the other side is the inner surface. The packaging material shown in Figures 7 to 9 is a material variant according to Figure 1. Therefore, in the heat seal layers 10 and 10' of Fig. 7, the LDPE has been replaced by a mixture thereof with polypropylene (PP). In the water vapor barrier layers 2' and 9' of Figure 8, a Chinese standard (CNS) A4 specification (210 X 297 mm) is applied to a paper scale of -10 - 1296968 A7. The second component is blended with HDPE. For example, an oxygen scavenger such as iron (II) oxide or some other ferrite compound. In Fig. 9, it is shown that a wrapping paper is used in place of the packaging board, and the fiber substrate 5 has a weight of, for example, 8 g/cm. When a polymeric coating is involved, the wrapper is similar to the cardboard shown in Figure 。. An example of a package of the present invention is shown in Fig. 10, which is formed by folding and heat sealing a package blank made of the package cardboard according to Fig. 2. The cardboard is configured in the package 11 such that the outer surface of the outer side of the fibrous substrate 5 has superposed HDPE and LDPE layers 2 and 1, in which case four layers of coatings 7, 8, 9 comprising the EVOH layer 7 And 10 are held inside the fiber substrate 5. At the joint 12 of the package 11, the edges of the blank have been overlapped, and the LDPE layers 1 and 1 of the opposite surfaces of the cardboard are tightly heat-sealed to each other. The package 11 according to Fig. 10 is also highly suitable for packaging liquid foods (such as dairy products and juices) as well as dry foods (such as flour, flakes and cereals, etc.). According to the invention, by means of the water vapour barrier layer 2 outside the fibrous substrate, the packaged product and the fibrous substrate 5 can be protected substantially in the package 11 from moisture which permeates from the outside. The inspection by the new packaging cardboard according to the present invention is further explained in the following examples. Example 1 An extrusion-coated packaging cardboard having a layer structure of: LDPE layer, weight 5 g/m 2 ; HDPE layer, weight 15 g/m 2 ; base cardboard, weight 190 g/m 2 ; HDPE layer, weight 15 g / m 2 ; LDPE layer, weight 5 g / m. At 90% relative humidity to 3 8 . (: Temperature detection, the cardboard -11 - The paper scale applies to the Chinese National Standard (CNS) A4 specification (210X 297 mm) 1296968 A7 B7 V. Description of the invention (9 Water vapor permeation is 6.4 g / m 2 / day. Cardboard curl is significantly small. Example 2

Manufacture of an extrusion-coated packaging cardboard having a layer structure of: LDPE layer, weight 10 g/m 2 ; hDPE layer, weight 10 g/m 2 ; base cardboard, weight 255 g/m 2 ; HDPE layer , weight 20 g / m 2 ; LDPE layer, weight 25 g / m 2 〇 at 90% relative humidity at 38 ° C temperature detection, the water vapor permeation of the cardboard is 4.6 g / m 2 / day. The result is the average of the permeations detected in different directions. Example 3 (Reference) For ease of reference, an extruded coated cardboard was constructed having a layer structure of LDPE layer 'weight 20 g/m 2 ; base cardboard, weight 255 g/m 2 ; HDPE layer, Weight 20 g / m 2 ; LDPE layer, weight 25 g / m 2 . The paperboard has an average water vapor permeation of 5 · 5 g / m 2 / day. The cardboard was significantly more curled than the cardboard in Examples 1 and 2. Order

Figure 11 of the crimp test includes the result of a crimp test in which the test strip is cut from an extruded coated cardboard having a size of 250 x 15 mm and is freely suspended at 50 t relative humidity at 23 t: temperature. For testing the environment. The strip is cut so that the result is displayed as being transverse to the machine direction. Graphs 1 to 5 show the results of the reference test series 'the LDPE layer coated on the side of the substrate cardboard having a weight of 230 g/m 2 and having a layer weight of 15, 25, 35, 45 or 55 g/m 2 . In addition, patterns 6 through 8 are reference tests for coating cardboard from only one side, with the inner layer being HDPE' and the outer layer being LDPE. Figure 6 relates to the following structure: base cardboard ‘heavy 295 g/m, HDPE layer, weight 35 g/m 2 · -12 -

Ι29β9^5)&118214 Patent Application Chinese Manual Replacement Page (October 95) Α7 Β7 9ΓΙαΙΤ Year Month Day 5. Invention Description (10) Layer, weight 15 g/m2. Figure 7 relates to the following structure: base cardboard, weight 230 g/m2; HDPE layer, weight 40 g/m2; LDPE layer, weight 15 g/m2. Figure 8 relates to the following structure: base cardboard, weight 295 g/m2; HDPE layer, weight 15 g/m2; LDPE layer, weight 5 g/m2. Comparing Figures 6-8 and 1-5, it can be noted that HDPE tends to curl the cardboard. Figures 9-11 relate to extruded coated cardboard on both sides such that, in addition to the LDPE layer, the coating is still on the cardboard side (Figure 9) or on both sides (Figures 10 and 11) including the HDPE layer. Figures 10 and 11 represent structures in accordance with the present invention. The fully symmetrical structure shown in Figure 11 has a minimum crimp in the machine direction with a base cardboard weight of 190 g/m2, a HDPE inner layer weight on both sides of the base cardboard of 15 g/m2, and an LDPE outer weight of 5 g/m 2. The cardboard discussed is the cardboard described in Example 1. Component symbol comparison table

1,10 LDPE Γ LDPE+PP 10' LDPE+PP 2? 9 HDPE 2, HDPE-mixture 9f HDPE - Mixture 3, 8 Adhesive 4, 7 EVOH T EVOH+PA 5 Cardboard 5f Paper 6 PA -13 Paper The scale applies to the Chinese National Standard (CNS) A4 specification (210 X 297 mm)

Claims (1)

Ι29^(6β18214 Patent Application Chinese Patent Application Scope Replacement (October 95;) • Patent Application Fan Park 1) A method of manufacturing a heat sealable packaging material, wherein the fiber has a heat of polymerization on both sides a sealing layer characterized in that the polymerized water of the intercalated, two-density polyethylene (HDPE) is present on both sides of the fibrous substrate (5) such that the coating is pressed against the fiber. Substrate and external heat seal layer 7 = screen heat seal layer (1, Η» direct contact. (, 1G) 1' and with outer and outer heat seal layer (1,1 〇) mL dimension substrate (5). 10) is characterized in that the superimposed 10) is co-extruded to the fiber as a symmetry. The layer of the coating material 4 is a heat-sealing method according to the method of any of the above-mentioned claims. The layer (1, 10) comprises a low density polyethylene (Ldpe). The method according to any one of claims 1 to 3, characterized in that at least one layer of extruded polymer which will form an oxygen barrier Layer = incorporated into the packaging material. s ' , ) . Ί Clause is used in accordance with the scope of patent application No. 1 to 3 _ ^ ^ The method of making a grave, and comprising a fibrous substrate (5), and a polymer comprising a high density polyethylene (HDPE) on both sides of the fibrous substrate and acting as a water vapor barrier layer A heat sealable packaging material characterized by an extruded polymer layer (2, 9), and an external heat seal layer (1, 91 〇) and an external heat seal layer (1, 1 〇) and internal water vapor The barrier layer is in direct contact with 79969-951019.doc This paper scale applies to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) 1296968 It is characterized by heat sealing which is characterized in that the packaging material layer (1, 10) according to item 6 of the patent application contains low density polyethylene (LDPE). 8. The packaging material according to item 7 of the scope of patent application consists of multiple layers, the order of which is... LDPE heat sealing layer (1): - HDPE water vapor barrier layer (2); - fiber substrate; - HDPE water vapor Barrier layer and -LDPE heat seal layer (1〇). 9. According to the scope of patent application No. 6 to 8 - = the amount of water vapor two layers on both sides of the fiber substrate (5) is the same, so that the layer structure of the packaging material ') The special step of the sixth or seventh aspect of the patent includes a polymer layer of at least one layer forming an oxygen barrier (:, (1) according to the packaging material of claim 10, the barrier layer (4, 6, 7) comprises ethylene - 浠妓 口 mouth, 羊 (PA) or a mixture of these... EV 〇 H, 聚 聚 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 To: Replacement - LDPE heat seal layer (1): _ HDPE water vapor barrier layer (2); - Fiber substrate (5); 79969-951019.doc -2 - 1296968 1296968 VI. Application for Patent Park 21. According to the packaging material of Article 20 of the patent application scope, the weight of the direct vapor barrier layer (2, 9) is 1〇2〇2米/m/, and the water is 22. According to any one of items 6 to 8 of the scope of the patent application, the heat seal layer (1, 10) has a weight of 5 to 5 g/m, which is 23 according to the scope of the patent application. The packaging material has a characteristic sealing layer (1, 10) having a weight of 5 to 30 g/m2. ', ', ',,,, is characterized by the heat characterized by the oxygen 24. The weight of the packaging material seal (1, 10) according to claim 23 of the patent application range is 7 to 20 g/m 2 . · The barrier layer (4, 6, 7) of the packaging material according to the scope of claim 1 is 3 to 15 g/m2. It is characterized by the oxygen 26. The packaging material barrier according to the scope of claim 25 The layer (4, 6, 7) has a weight of 5 to 1 g/m2. 27. A sealed package which is borrowed from a packaging material manufactured according to the method of any one of claims 5 to 5. Made of folding and heat sealing, characterized in that in the material, a layer of extruded polymer (2, 9) is present on both sides of the fibrous substrate (5) under the outer heat seal layer (1, 1 〇). The polymer layer comprises high density polyethylene (HDPE) and acts as a water vapor barrier, and the external heat seal layer (1, 10) is in direct contact with the water vapor barrier layer. 28. According to the scope of claim 27th. a package characterized by further having at least one polymer layer forming an oxygen barrier between the substrate and the water vapor barrier layer on the inner side of the fibrous substrate (5) (7) 29. A package according to claim 27 or 28, characterized in that it is a can package for liquid food and formed by polymer coated cardboard. 4 - 79969-951019.doc Paper scale applies to China National Standards (CNS) A4 specification (210 X 297 public) 1296968 έβ8 C8 D8 VI. Patent application scope 30. According to the package of claim 27 or 28, it is characterized by The food product is dried and packaged from a polymer-coated cardboard. The package according to claim 27 or 28 is characterized in that it is a pouch package formed from polymer coated paper. 79969-9510i9.doc - 5 - This paper size applies to China National Standard (CNS) A4 specification (210X297 mm)