Re-pulpable paper-based backing layer

Abstract

The present invention relates to a backing layer comprising a barrier coating comprising an inorganic filler and a polymer having a glass transition temperature of-35 DEG C to + 15 DEG C.

Description

Technical Field

[0001] The present disclosure relates to a paper-based backing layer. The backing layer includes multiple layers, in particular a paper layer and a barrier coating, and the barrier coating may include a polymer and an inorganic filler. Such a backing layer can be used for tapes, labels, and related products.

[0002] Background

[0003] Paper-based backing layers form the backbone of various tapes (sealing tapes, opening tapes (such as tear tapes), and reinforcing tapes), labels, and related products, and printing can be performed on the tape surface. Paper-based backing layers typically include multiple coatings in a layer applied to a paper carrier.

[0004] Since tapes, labels, and related products are attached to cardboard boxes, letters, envelopes, etc., these materials as a whole will enter the recycling process. During the recycling process, these materials are fed into a pulper and mechanically processed in water with a neutral to alkaline pH value to break down the paper into cellulose fibers. Subsequently, several purification steps, such as screening and flotation, are carried out, and finally a pulp containing cellulose fibers is obtained. This pulp needs to meet the feeding requirements of the paper machine.

[0005] During the process of a paper machine processing cellulose pulp from recycled paper, machine interruptions and shutdowns frequently occur. This reduces the efficiency of the recycling process.

[0006] These interruptions are caused by so-called "sticky substances". The sticky substances are aggregates or even lumps of sticky polymers, which originate from the coatings applied to the paper carrier and cannot be removed from the cellulose fibers during the purification process of the cellulose pulp. The sticky substances appear as oily spots on the recycled paper, causing the recycled papers to stick to each other. The sticky substances also adhere to the rollers, thereby affecting the quality of the paper web during the production process, thus reducing production efficiency and increasing production costs.

[0007] During the purification process, a certain proportion of aggregates and lumps of sticky polymers are separated from the pulp through screens, filters, and filters. However, this purification is not thorough. In addition, the separated aggregates and lumps of sticky polymers cannot be recycled, and they will ultimately enter the waste stream to be sent to landfill or incineration. From an environmental protection perspective, this situation should be avoided.

[0008] Therefore, even including paper-based backing layers, the recyclability of traditional tapes, labels, and related products is still not satisfactory.

[0009] Recyclability can be measured according to the "Voluntary Standard For Repulping and Recycling Corrugated Fiberboard Treated to Improve Its Performance in the Presence of Water and Water Vapor" (revised on August 16, 2013) issued by the Fiber Box Association (FBA) of the United States. This standard includes guidelines for measuring fiber recyclability and the proportion of tacky substances in recycled products. Based on the bone-dry fiber input into the pulper, this standard sets a requirement of at least 85% fiber recyclability, and the proportion of tacky substances should be 15 or lower.

[0010] Traditional paper-based backing layers have approximately % fiber recyclability and a proportion of tacky substances above about 100. From the perspectives of production efficiency and environmental pollution, these values are unfavorable.

[0011] Therefore, there is a need in the art to provide a paper-based backing layer with improved recyclability and production efficiency. As determined according to the aforementioned voluntary standard, such a paper-based backing layer is expected to exhibit at least 85% fiber recyclability and a proportion of tacky substances lower than 15, preferably lower than 5. Summary of the Invention

[0013] The present disclosure relates to a paper-based backing layer.

[0014] The present disclosure provides a backing layer, comprising:

[0015] A first layer, which is a paper layer;

[0016] A second layer applied on one or both sides of the first layer, which is a barrier coating,

[0017] Characterized in that the barrier coating comprises:

[0018] 30% to 70% inorganic filler by weight;

[0019] 70% to 30% polymer by weight, with a glass transition temperature (Tg) of -35°C to +15°C.

[0020] The present disclosure also provides a tape comprising the above-mentioned backing layer.

[0021] The backing layer of the present disclosure has passed the strict standards of the "Voluntary Standard for the Repulping and Recycling of Corrugated Fiberboard Treated to Improve Its Performance in Water and Water Vapor Environments" (revised on August 16, 2013) issued by the Fibre Box Association (FBA) of the United States. The backing layer exhibits excellent fiber recyclability and a very high stickies count for repulping. This backing layer improves production efficiency and reduces the ecological footprint. Therefore, it is advantageous and useful for improving the production efficiency and ecological footprint of traditional tapes, labels, and related products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Depicts a backing layer suitable for single-sided tape.

[0023] Figure 2 Depicts a backing layer suitable for double-sided tape. DETAILED DESCRIPTION OF THE INVENTION

[0025] Definition

[0026] Other aspects, features, and advantages of the exemplary embodiments will become apparent from the following detailed description.

[0027] The patents, published applications, and scientific literature cited herein embody the knowledge of those skilled in the art, and their entire contents are incorporated herein by reference as if each were specifically and individually indicated to be incorporated by reference.

[0028] In this document, whether in transitional phrases or in the body of the claims, the terms "comprising" and "including" shall be construed in an open-ended sense. That is, these terms shall be construed as synonymous with "having at least" or "including at least". When used in the context of a method, the term "comprising" means that the method includes at least the recited steps, but may also include other steps. When used in the context of a composition, the term "comprising" means that the composition includes at least the recited features or components, but may also include other features or components.

[0029] The terms "consisting essentially of" or "consisting essentially of" have a partially closed meaning, that is, they do not allow the inclusion of steps, features, or components that would substantially change the basic characteristics of the method or composition; for example, steps, features, or components that would seriously interfere with the desired performance of the compounds or compositions described herein, that is, the method or composition is limited to the specified steps or materials, and those steps or materials that do not substantially affect the basic and novel characteristics of the method or composition. "Consisting of" and "consisting of" are closed terms that only allow the inclusion of the recited steps, features, or components.

[0030] As used herein, the singular forms "a", "an" and "the" also specifically include the plural forms of the terms to which they refer, unless the context clearly dictates otherwise.

[0031] As used herein, the term "dissolved" or "substantially dissolved" means the dissolution of a solid in a solution. When the resulting solution is clear or substantially clear, the solid is considered to be "dissolved" or "substantially dissolved" in the solution.

[0032] The recitation of numerical ranges of variables used herein is intended to convey that the variable can be equal to any value within that range. Thus, for a variable that is inherently discrete, the variable can be equal to any integer value within the numerical range, including the endpoints of the range. Similarly, for a variable that is inherently continuous, the variable can be equal to any real value within the numerical range, including the endpoints of the range. For example, a variable described as having a value between 0 and 2 can be 0, 1, or 2 for a variable that is inherently discrete; and can be 0.0, 0.1, 0.01, 0.001, or any other real value for a variable that is inherently continuous.

[0033] In the specification and claims, unless the context clearly indicates otherwise, the singular forms include plural referents.

[0034] Unless otherwise defined, the technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art to which this specification pertains.

[0035] Description

[0036] The present disclosure provides a backing layer. This is a laminated body used as a support, on which multiple layers can be applied such that the resulting multi-layer stack respectively has specific properties and achieves specific functions, thereby making the multi-layer stack suitable for different fields.

[0037] The backing layer is a paper-based backing layer.

[0038] The backing layer of the present disclosure includes:

[0039] A first layer, which is a paper layer;

[0040] A second layer applied on one or both sides of the first layer, which is a barrier coating,

[0041] Characterized in that the barrier coating includes:

[0042] 30% to 70% by weight of an inorganic filler;

[0043] 70% to 30% by weight of a polymer having a glass transition temperature (Tg) of -35°C to +15°C.

[0044] The paper layer serves as a carrier layer or a support layer. In the prior art, it can be referred to as a paper carrier.

[0045] The barrier coating can be applied on both sides of the paper layer or only on one side of the paper layer. Preferably, it is applied on both sides of the paper layer. The barrier coating can be directly applied on the first layer which is the paper layer, preferably directly on both sides of the paper layer.

[0046] The backing layer can include a primer layer applied on the second layer (i.e., the barrier coating). The primer layer acts as an intermediate layer between the barrier coating and another layer, ensuring the stability of the laminate.

[0047] In one embodiment, the primer layer can be present only on one side of the backing layer. The primer layer can be directly applied on the barrier coating only on one side of the backing layer. The release coating can be applied on the second layer (i.e., the barrier coating) on the side of the backing layer opposite to the primer layer. The release coating can be directly applied on the second layer. Thus, the release coating is present only on one side of the backing layer. The release coating ensures that the backing layer can be rolled up during the production process and enables the required length of the backing layer to be unrolled before use.

[0048] Figure 1 A backing layer is depicted, which includes a paper layer (1), a barrier coating (2), a primer layer (3) and a release coating (4).

[0049] In one embodiment, the backing layer can include a first layer which is a paper layer; a second layer which is a barrier coating directly applied on both sides of the paper layer; a primer layer which is directly applied on the second layer only on one side of the backing layer; and a release coating which is directly applied on the second layer on the side of the backing layer opposite to the primer layer. In one embodiment, the backing layer can be composed of the above layer sequence and stacking.

[0050] The primer layer can receive a layer such as an adhesive layer. When the adhesive is applied only on one side, a single-sided tape can be formed.

[0051] Figure 2 A backing layer is depicted, which includes a paper layer (1), two barrier coatings (2) and two primer layers (3).

[0052] In one embodiment, the primer layer can be present on both sides of the second layer (i.e., the barrier coating). The primer layer can be directly applied on the barrier coatings located on both sides of the backing layer. Thus, in one embodiment, the backing layer can include: a first layer which is a paper layer; a second layer which is a barrier coating directly applied on both sides of the paper layer; and a primer layer directly applied on the second layer located on both sides of the backing layer. In one embodiment, the backing layer can be composed of the above layer sequence and stacking.

[0053] The two-layer base coat can receive a layer such as an adhesive layer. When the adhesive is applied on the two-layer base coat, a double-sided tape can be formed.

[0054] The second layer (i.e., the barrier coat) comprises 30% to 70% by weight of an inorganic filler. The barrier coat can comprise preferably 35 wt.% to 65 wt.%, more preferably 40 wt.% to 60 wt.%, most preferably 45 wt.% to 55 wt.% of an inorganic filler.

[0055] The inorganic filler can be a hydrophilic filler. The inorganic filler can be selected from the group consisting of kaolinite, calcined kaolinite, calcium carbonate, precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), talc, mica, clay, silica, precipitated silica, fumed silica, titanium dioxide, or a mixture thereof. The barrier coat preferably can comprise kaolinite. These hydrophilic fillers generally do not undergo any coating or chemical treatment.

[0056] The presence of the inorganic filler in the barrier coat in the above proportions has the advantage that the repulpability and sticky count of the backing layer are significantly improved. Without being bound by theory, it is believed that the presence of a large amount of inorganic filler (especially hydrophilic filler) in the barrier coat allows water to penetrate into the layer during the recycling process and suspends the polymer components in the layer in water.

[0057] The second layer (i.e., the barrier coat) comprises 70% to 30% by weight of a polymer having a glass transition temperature (Tg) of -35°C to +15°C. These weight percentages are calculated based on all components of the barrier coat in the dry, applied state. The barrier coat can comprise 65 wt.% to 35 wt.%, preferably 60 wt.% to 40 wt.%, more preferably 55 wt.% to 45 wt.% of a polymer having a glass transition temperature (Tg) of -35°C to +15°C.

[0058] The glass transition temperature (Tg) of the polymer can be -30°C to +10°C, preferably -25°C to +5°C. The glass transition temperature is measured according to DIN ISO 53765 (1994-03). Polymers with a Tg below 0 degrees Celsius, especially well below 0 degrees Celsius, are considered hard polymers and tend to be sticky. Polymers with a Tg above 0 degrees Celsius tend not to be sticky. The backing layer provided by the present disclosure comprises a polymer with a Tg below 0 degrees Celsius, which is sticky but still has a sticky count of less than 5, and thus, according to the tests of Western Michigan University, they meet the above voluntary standards.

[0059] The polymer may be selected from the group consisting of carboxylated styrene-butadiene rubber, styrene-butadiene rubber, acrylate polymer, nitrile rubber, natural rubber, polyvinyl acetate, or a mixture thereof, wherein carboxylated styrene-butadiene rubber is preferred.

[0060] The barrier coating may include carboxylated styrene-butadiene rubber having a Tg of -27°C to -23°C, in a proportion of 65 wt.% to 35 wt.%, preferably 60 wt.% to 40 wt.%, more preferably 55 wt.% to 45 wt.%.

[0061] The barrier coating may include carboxylated styrene-butadiene rubber having a Tg of +3°C to +7°C, in a proportion of 65 wt.% to 35 wt.%, preferably 60 wt.% to 40 wt.%, more preferably 55 wt.% to 45 wt.%.

[0062] The barrier coating may include an antifoaming agent. The content of the antifoaming agent may be from 0 to 0.05 wt.%. If the antifoaming agent is present, its content is at most 0.05 wt.%, or from 0.01 wt.% to 0.03 wt.%. These proportions are calculated based on the total weight of the barrier coating such that the contents of the inorganic filler, polymer, and antifoaming agent add up to 100 wt.%. The antifoaming agent may be selected from the group consisting of mineral oil-based antifoaming agents, vegetable oil-based antifoaming agents, and silicone oil-based antifoaming agents.

[0063] In one embodiment, the barrier coating includes the inorganic filler in the given weight percentage, the polymer in the given weight percentage, and the antifoaming agent in the given percentage as described above. In one embodiment, the barrier coating may be composed of the components in the given weight percentage as described above.

[0064] The barrier coating may be substantially composed of the components in the given percentage as described above, where impurities due to processing parameters or raw material specifications are not excluded, nor is the presence of a small weight percentage of conventional additives, provided that there is no substantial change to the technical properties of the barrier coating, the expected effects described in the present disclosure, and the usability of the barrier coating. To achieve the expected effects, the combined proportion of the inorganic filler and polymer in the barrier coating is at least 93%, preferably at least 95%, and even at least 97%.

[0065] The barrier coating may include conventional additives such as crosslinking agents, dispersants, wetting agents, thickening agents, water repellents, or water attractants, and the dosage of the additives is a conventional dosage, for example, the minimum amount is 0.05 wt.%, 0.1 wt.%, or 0.25 wt.%, and the maximum is 3 wt.%, 4 wt.%, or 5 wt.%. When the additives are present, the combined proportion of the inorganic filler and polymer in the barrier coating is at least 93%, preferably at least 95%, and even at least 97%.

[0066] The barrier coating is applied at a coating weight of 1 to 10 gsm (grams per square meter), preferably 3 to 7 gsm.

[0067] The first layer of the backing layer in the present disclosure is a paper layer.

[0068] The elongation rate of the paper layer in the machine direction (MD) can be 3% to 10%, preferably 5% to 8%, where the elongation rate is measured according to DIN EN ISO 1924-2 (2008).

[0069] The elongation rate of the paper in the cross direction (CD) orthogonal to the machine direction (MD) can be 5% to 15%, preferably 8% to 12%, where the elongation rate is measured according to DIN EN ISO 1924-2 (2008). These elongation rate values, especially the values in the machine direction, enable the backing layer to be applied to tapes and related fields. This elongation rate allows the backing layer to be used in various forms of tapes for wrapping or fixing. Even after applying the layers described herein, the elongation rate is still maintained. Due to the application of these layers, the elongation rate of the final product can even exceed the above elongation rate.

[0070] In addition, the paper used as the paper layer can have a high density and a high sizing degree, so that the components of the barrier coating do not impregnate the paper layer or only to a very limited extent, maintaining its repulpability.

[0071] The air permeability of the paper layer (measured as air resistance (Gurley)) can be 5 to 25 Gurley, preferably 10 to 20 Gurley, and this value is measured according to ISO 5636-5 (2003).

[0072] The water absorbency (Cobb60) value of the paper layer can be 20 to 40 gsm, preferably 25 to 35 gsm, and this value is measured according to the Cobb60 test method ISO 535 (2014).

[0073] These air permeability and water absorbency values ensure that the components of the barrier coating do not impregnate the paper layer or only to a very limited extent, while the paper layer maintains its repulpability. The paper layer can be composed of paper that meets the above requirements and does not carry other coatings or has not undergone any treatment (such as coating), except for the treatment or coating for achieving the above technical properties.

[0074] The paper used as the paper layer can be selected from the group consisting of bleached or brown kraft paper, bleached or brown sack kraft paper, semi-stretched kraft paper, semi-stretched sack kraft paper, preferably semi-stretched sack kraft paper.

[0075] The paper meets the requirements for air resistance (Gurley) and water absorbency (Cobb60) described above, such that the components of the barrier coating do not or only to a very limited extent impregnate the paper layer, while the paper layer retains its repulpability.

[0076] These papers are not subjected to any additional treatment, such as additional coating. These papers are used as received.

[0077] The basis weight of the paper used as the paper layer can be from 40 to 100 gsm, or from 40 to 80 gsm, preferably from 50 to 70 gsm.

[0078] The backing layer may include a primer coat, which may be present on one or both sides of the second layer (i.e., the barrier coating) as described above. The primer coat may include a polymer or a polymer composition selected from the group consisting of styrene-butadiene rubber, acrylate polymers, nitrile rubber, polyvinyl acetate, natural rubber, prevulcanized natural rubber, butyl acrylate; methacrylate-grafted natural rubber, carboxylated styrene-butadiene rubber, and polyurethane.

[0079] The primer coat may include one polymer or a mixture of two or more polymers. The primer coat may be a composition comprising prevulcanized natural rubber and butyl acrylate. The primer coat may also be a composition comprising methacrylate-grafted natural rubber and carboxylated styrene-butadiene rubber. The composition may include methacrylate-grafted natural rubber and carboxylated styrene-butadiene rubber mixed in a ratio of 80:20 to 95:05.

[0080] In some embodiments, the primer coat may include one or more of the same polymers as the barrier coating.

[0081] The primer coat may be present at a coating weight of 0.1 to 3 gsm, preferably 0.5 to 2 gsm.

[0082] As described above, a release coating may be applied over the primer coat. Compositions for release coatings are well known in the art. For example, the release coating may include a composition containing a polymer selected from the group consisting of hydrophilic acrylic or acrylate polymers; water-based vinyl acetate copolymer latexes.

[0083] A release coating may be applied over the primer coat to a coating weight of 0.1 to 5 gsm, preferably 0.5 to 4 gsm.

[0084] The total thickness of the backing layer including the layers described herein is from 60 to 150 microns. For example, the thickness of the 90 g / m 2 backing layer in the present disclosure is from 105 to 135 microns. The thickness of the 70 g / m 2 backing layer is from 70 to 100 microns.

[0085] Measured according to the above-mentioned voluntary standards and in accordance with the test methods for repulping and recycling of Western Michigan University, the repulpability of the backing layer of the present disclosure exceeds 85%. The amount of stickies formed during the papermaking process of the backing layer of the present disclosure is also less than 5. The test methods show that: a) cellulose fibers can be recycled at a high recovery rate to make paper; b) especially when paper recycling is carried out using tapes or other products including the backing layer of the present disclosure, the polymers used in the production of the backing layer can be easily separated from the cellulose fibers. Therefore, the backing layer of the present disclosure has a high degree of recyclability and repulpability.

[0086] The backing layer is suitable for a variety of applications, such as tapes for fixing and wrapping cardboard boxes, tapes applied to the inner side of envelope closures, and the construction industry.

[0087] The backing layer is also suitable for printing media, labels, strapping tapes, handle tapes, printed packaging tapes, promotional banderoles, industrial packaging materials for light, medium, and heavy applications, and paper adhesive foils.

[0088] The backing layer is particularly suitable for single-sided or double-sided tapes as shown in Figure 1 and Figure 2

[0089] The present disclosure also provides a tape that includes the backing layer of the present disclosure. The tape includes an adhesive layer on a single primer coat to provide a single-sided tape. The tape includes an adhesive layer on two primer coats to provide a double-sided tape. The adhesive layer is well-known in the art. Any adhesive layer known in the art can be used in combination with the backing layer of the present disclosure. Due to the excellent properties of the backing layer, the provided tape has a high degree of recyclability and repulpability.

[0090] The backing layer of the present disclosure is made by continuously coating each layer on a paper layer with the above-mentioned coating weights. The components of each layer can be applied in the form of a dispersion, solution, or dry coating using standard methods known in the art.

[0091] The barrier coating can be applied by an impregnation device, such as using a water bath containing a polymer dispersion in which the paper layer moves. Then the impregnated layer can be introduced into a pair of rollers to remove the excess coating on the paper layer. Then, it can be dried. Then, the primer coat and the release coat (if necessary) can be applied by an air knife device. Examples

[0092] Material

[0093] Paper layer:

[0094] ​Unbleached kraft paper for semi-stretched bags; grammage 60 g / m 2 , Tensile strength: (MD) 5.3, (CD) 4.0; Air permeability (air resistance, Gurley) 18 s / 100 ml; Water absorbency (Cobb60) 31 g / m 2 (60 s).

[0095] Barrier coating:

[0096] Used the carboxylated styrene-butadiene rubber (SBR) product "Exopal L7063" with a Tg of +5 °C from EOC Belgium N.V., providing an aqueous colloidal dispersion of a carboxylated styrene-butadiene copolymer (solid content 49%-51%).

[0097] Used the carboxylated styrene-butadiene rubber (SBR) product "LigodI4086Binder" with a Tg of -25 °C from Trinseo, providing an aqueous colloidal dispersion of a carboxylated styrene-butadiene copolymer (solid content 48%-50%).

[0098] For kaolinite, used the product named "Capim DG slurry", and the slurry provided has a solid content of 70.5 (wt.%).

[0099] Release coating:

[0100] Used the product "Primal R-253ER Emulsion" from Dow Chemical Company, providing a hydrophilic acrylic emulsion with a solid content of 40%. As an option, the product "OrgalKR250" from Organikkimya (solid content 40%) can also be used.

[0101] Base coating:

[0102] 90% methacrylate-grafted natural rubber and 10% carboxylated styrene-butadiene rubber.

[0103] Method

[0104] The glass transition temperature was measured according to DIN ISO 53765 (1994-03).

[0105] The elongation at break was measured according to DIN EN ISO 1924-2 (2008).

[0106] The air permeability of the paper was measured as air resistance (Gurley) according to ISO 5636-5 (2003).

[0107] The water absorbency (Cobb 60) of the paper is measured according to the Cobb 60 test method ISO 535 (2014).

[0108] The repulpability and recyclability are measured according to the "Voluntary Standard for Repulping and Recycling of Corrugated Fiberboard Treated to Improve Its Performance in Water and Water Vapor Environments" (revised on August 16, 2013) issued by the Fiber Box Association (FBA) of the United States. The test is conducted by Western Michigan University in its papermaking pilot plant. This test method aims to evaluate the repulpability and recyclability of moisture-proof treatments or coatings applied to liner or composite corrugated board to determine the minimum thresholds for corrugated board treated with moisture-proof treatment or coating, which are expected and marked as recyclable into new boxboard and other paper products. The following is a description of the test. In this test, the following terms have the following meanings:

[0109] - Fiber-to-fiber yield refers to the amount of fiber remaining after processing, expressed as a percentage of the fiber present in the material to be tested.

[0110] - Recyclable means that used paper, including in-plant and post-consumer waste paper and cardboard, can be processed into new paper or cardboard using the processes specified in this standard.

[0111] - Repulpable means that the test material can be rewetted and fibrillated using the processes specified in this standard for subsequent paper formation.

[0112] - Handmade paper is paper made from a suspension of fibers in water during operation, where each sheet is formed individually by draining the pulp suspension on a fixed paper mold.

[0113] Preliminary analysis: Before starting the test protocol, the moisture content of the treated corrugated sample is determined.

[0114] Part 1: Repulpability

[0115] According to the process outlined in the following repulpability test procedure, 100% of the treated corrugated paper is repulped in a Modified Waring Blender and a British Disintegrator in water at a pH of 7 (±0.5 pH) and a temperature maintained at 125°F (±10°). The repulped material is separated through a screen with a screen slot of 0.010 inches or less to determine the fiber recovery rate, expressed as a percentage of the input fiber amount.

[0116] The fiber yield in the repulpability test must be at least 80% of the total weight or 85% of the oven-dry fiber amount fed into the pulper.

[0117] Part 2: Recyclability

[0118] Mix at least 20% of the processed corrugated paper with the remaining same unprocessed corrugated paper in a laboratory-scale pulper at pH 7 (±0.5 pH) and 125°F (±10°F). This is the recyclability test sample. As a control, under the same conditions, pulp 100% of the same unprocessed corrugated paper. Each pulped material is passed (sequentially) through a pressure screen equipped with a 0.062-inch aperture screen basket, the same screen, or a similar screen equipped with a 0.010-inch slot screen basket, and a reverse centrifugal separator under the conditions specified in the following recyclability test procedure.

[0119] Make a handsheet (3.0 grams) from the qualified pulp in the final (clean) stage. For each batch of test samples, press and thermally dry the handsheet and test the product performance characteristics. The appearance test should be carried out according to the procedure outlined in Appendix B. The number of spots on the final paper (average of 3 sheets, single spot area ≥ 0.4 mm 2 ) shall not exceed 15, or not exceed 30% of the control group. The detailed process of recyclability is given in the following recyclability test procedure.

[0120] Repulpability test procedure

[0121] Purpose

[0122] To determine the repulpability of corrugated board. (Note that the repulpability test must be carried out on the processed corrugated board at least twice. The sample must pass two of the three tests).

[0123] Equipment

[0124] · Sample cutting device

[0125] · Balance (accurate to 0.01 grams)

[0126] · Waring blender (with special blades, see Figure 1 )

[0127] · Hot water at 125°F ± 10°F (52°C ± 5°C)

[0128] · British pulper (Paper Pulp Evaluation Standard Equipment No. 270)

[0129] · 10-mesh (0.010-inch) open flat screen, such as Valley screen or Somerville screen

[0130] · Aluminum weighing pan

[0131] · Laboratory oven at 221°F (105°C)

[0132] Sample Test

[0133] 1. Cut the corrugated board into strips that are 1 1 / 4 inches (31.8 mm) × 4 inches (102 mm).

[0134] 2. Weigh 0.055 pounds (25 grams) of corrugated board.

[0135] 3. Place the sample in 1500 ml of water at 125°F ± 10°F (52°C ± 3°C).

[0136] 4. Preheat the blender and the Beater Hollander to 125°F ± 10°F.

[0137] 5. Stir in a one-gallon capacity Waring blender (equipped with special blades) at low speed (15,000 rpm) for 4 minutes.

[0138] 6. Rinse all the fibers in the blender with 500 ml of hot water.

[0139] 7. Defiberize in a Beater Hollander (total volume 2000 ml) at 3000 rpm for 5 minutes.

[0140] 8. Run on an open flat screen with a 0.010-inch (0.254 mm) screen slot for 20 minutes, maintaining a 1-inch head; collect the acceptable pulp and the rejects in an aluminum weighing pan.

[0141] 9. Dry in a laboratory oven at 221°F (105°C) for 12 hours (±4 hours).

[0142] 10. Weigh the weighing pan and record the net weight of the acceptable pulp, the net weight of the rejects, and the total weight of the acceptable pulp and the rejects.

[0143] Calculation

[0144] Percentage of rejects = (Net weight of rejects × 100) / (Net weight of acceptable pulp + Net weight of rejects)

[0145] The value obtained represents the percentage of fiber repulpability.

[0146] Recyclability test procedure

[0147] Note: The control sample and the samples of the treated and untreated test materials must be tested at least twice and must pass two out of three tests.

[0148] 1. Obtain a processed corrugated paper sample to be evaluated. Select a sufficient amount of material from the sample for testing. The selected material should be as representative of the overall material as possible. Also obtain a sufficient amount of unprocessed corrugated paper to perform the test protocol. The choice of feed rate will depend on the capacity of the pilot pulper used. Pulping should be carried out at a consistency of 3% or at the consistency recommended by the pulping equipment manufacturer.

[0149] 2. Determine the moisture content [TAPPI T 412]. Perform Steps 3 to 9 twice, once using the unprocessed "control" sample and once using the "recyclability test sample".

[0150] 3. Use the selected sample material of any suitable size, but not less than 1×1 square inch. Preheat the equipment to 125°F (±10°). Adjust the pH of the feed so that the pH reaches 7 (±0.5 pH) after pulping. Raise the temperature of the pulper to 125°F (±10°). Feed the material into the pulper and pulp for 15 minutes while maintaining the temperature at 125°F (±10°).

[0151] 4. Repeat Step 3 until sufficient material for the subsequent steps is obtained. Keep the pulp temperature at 125°F (±10°) until it is used in Step 5.

[0152] 5. If necessary, mix multiple batches of pulp and dilute it with water heated to 125°F (±10°) to the consistency recommended by the equipment manufacturer. Adjust the pH to 7 (±0.5 pH). Preheat the screen with 0.0625-inch holes to 125°F (±10°) and maintain this temperature throughout the screening step. Pass the pulp sample through the preheated screen at a screen reject rate of 10% of the feed rate or at an appropriate screen reject rate according to the manufacturer's technical specifications or recommendations.

[0153] 6. For the acceptable pulp obtained in Step 5, use a screen basket with a screen slot of 0.010 inch and repeat the procedure in Step 5 while maintaining the temperature, consistency, and a 10% screen reject rate or at the rate according to the manufacturer's technical specifications.

[0154] 7. Pass the acceptable pulp obtained in Step 6 through a light reverse centrifugal cleaner, maintaining the temperature of 125°F (±10°), the consistency, and the pressure differential specified for the cleaner used. Determine the reject volume rate and record and report it.

[0155] 8. According to TAPPI T 205, form a hand sheet with the acceptable pulp obtained in Step 7 under the following conditions:

[0156] - The pulp should be vigorously agitated (without causing a change in the fiber distribution in the pulp), and the temperature should be maintained at 125°F (±10°) and the pH at 7 (±0.5 pH).

[0157] - Constrain and dry the paper on a surface dryer with the temperature maintained at 250 to 275°F until the moisture content is 7%.

[0158] - Readjust to TAPPI standard conditions before testing.

[0159] Handsheet preparation for stickies / speck counts test:

[0160] 1. Turn on the power of the Carver press and preheat the upper and lower platens to 350°F.

[0161] 2. Dilute the test material to a concentration of approximately 1%.

[0162] 3. Prepare and dry 500 ml of the check paper.

[0163] · Extrude the excess moisture with two pieces of blotting paper, a circular metal plate, and a roller.

[0164] · Dry on new blotting paper in a quick dryer.

[0165] 4. Weigh the handsheet and mark its identification and dry weight on the front (not the wire side) of the handsheet.

[0166] 5. Calculate the amount of slurry for the test paper using the following formula:

[0167] · 2.00 grams ÷ dry weight of the paper × 500 = milliliters of slurry for the test paper.

[0168] 6. Make 3 test handsheets using the calculated amount of slurry.

[0169] 7. Place the paper on blotting paper, dry it with a quick dryer, and then mark its identification on the front of each sheet.

[0170] 8. Remove the test paper from the quick dryer (drying time is 3 - 5 minutes).

[0171] 9. Place each test paper between filter paper and blotting paper in the following layout (from bottom to top):

[0172] Blotting paper

[0173] Filter paper

[0174] Sticky paper

[0175] Filter paper

[0176] Blotting paper

[0177] 10. Stack the test papers together and press them in a preheated Carver press at 350°F and a pressure of 500 psi (pounds per square inch) for 5 minutes. Observe the pressure gauge carefully to keep it at 500 psi.

[0178] 11. Remove the test papers from the Carver press and weigh each paper.

[0179] · Record the dry weight of each paper.

[0180] 12. Use any suitable analysis tool, such as the dirt evaluator in TAPPI T-537, or the image analysis system mentioned in TAPPI T-277 and TAPPI T-563, to count the number of spots with an area ≥ 0.4 mm 2 on the hand-sheet paper.

[0181] This number is the spot count, also known as the "stickiness count" or "stickies count".

[0182] Example

[0183] The backing layer according to the present disclosure is prepared as follows:

[0184] Apply the barrier coating on the paper layer through a water bath containing a polymer dispersion. The paper layer will move in the water bath. The temperature of the water bath is usually ambient temperature (15 to 40 degrees Celsius). Then, the impregnated layer can be introduced into a pair of rollers to remove the excess coating on the paper. Subsequently, the paper can be dried at a temperature of 50 to 220 degrees Celsius. Then, the primer coat and the release coating (if necessary) can be applied using an air knife device at ambient temperature.

[0185] Example 1

[0186] Use unbleached semi-extensible kraft paper with a basis weight of 60 gsm as described above as the paper layer.

[0187] Coat both sides of the paper layer with a composition comprising 50% carboxylated styrene-butadiene rubber (SBR) with a Tg of -25 degrees Celsius and 50% kaolinite to provide the barrier coating. The coating weight is 5 gsm. In this example, soft SBR is used.

[0188] Coat one side of the resulting laminate with a hydrophilic acrylic dispersion (Primal R253 / Orgal KR250) with a coating weight of 2 gsm to provide the release coating.

[0189] When the obtained backing layer was tested using the repulping and recycling test method of Western Michigan University, fiber recoveries of 92.5% and 94.1% (two tests) were obtained. Since these values are higher than 85%, the sample passed this test method.

[0190] Regarding the stickies test, 1 sticky was observed per hand sheet. Since it is lower than the target value of 5 stickies, the sample passed this test method.

[0191] Example 2

[0192] An unbleached semi-extensible sack kraft paper with a basis weight of 60 gsm was used as the paper layer.

[0193] The composition, which included 50% carboxylated styrene-butadiene rubber (SBR) with a Tg of +5 °C and 50% kaolinite, was coated on both sides of the paper layer to provide a barrier coating. The coating weight was 5 gsm. In this example, hard SBR was used.

[0194] A hydrophilic acrylic dispersion (Primal R253 / Orgal KR250) was coated on one side of the obtained laminate with a coating weight of 2 gsm to provide a release coating.

[0195] When the obtained backing layer was tested using the repulping and recycling test method of Western Michigan University, fiber recoveries of 95.8% and 97.5% (two tests) were obtained. Since these values are higher than 85%, the sample passed this test method.

[0196] Regarding the stickies test, 1.67 stickies were observed per hand sheet. Since it is lower than the target value of 5 stickies, the sample passed this test method.

[0197] Comparative example

[0198] An unbleached semi-extensible sack kraft paper with a basis weight of 60 gsm was used as the paper layer.

[0199] The composition, which included 50% carboxylated styrene-butadiene rubber (SBR) with a Tg of -25 °C, was coated on both sides of the paper layer to provide a barrier coating. The coating weight was 5 gsm.

[0200] A hydrophilic acrylic dispersion (Primal R253 / Orgal KR250) was coated on one side of the obtained laminate with a coating weight of 2 gsm to provide a release coating.

[0201] Apply a dispersion on the other side of the laminate, the dispersion comprising 90% methacrylate-grafted natural rubber and 10% carboxylated styrene-butadiene rubber, with a coating weight of 1 gsm, to provide a primer coat.

[0202] When the resulting backing layer was tested using the repulping and recycling test method of Western Michigan University, fiber recoveries of 65.9% and 69.2% (two tests) were obtained. Since the values were both below 85%, the sample failed this test method.

[0203] Regarding the stickies test, 100 stickies were observed per hand sheet. Since it was higher than the target value of 5 stickies, the sample failed this test method.

[0204] Embodiment part

[0205] 1. A backing layer, comprising:

[0206] A first layer, which is a paper layer;

[0207] A second layer applied on one or both sides of the first layer, which is a barrier coating,

[0208] Characterized in that the barrier coating comprises:

[0209] 30% to 70% by weight of an inorganic filler;

[0210] 70% to 30% by weight of a polymer having a glass transition temperature (Tg) of -35°C to +15°C.

[0211] 2. The backing layer according to claim 1, comprising a primer coat applied on the second layer, the second layer being a barrier coating, wherein the primer coat is present only on one side of the backing layer.

[0212] 3. The backing layer according to claim 1, comprising a primer coat applied on the second layer, the second layer being a barrier coating, wherein the primer coat is present on both sides of the backing layer.

[0213] 4. The backing layer according to claim 2, comprising a release coating applied on the second layer, the second layer being a barrier coating, wherein the release coating is present only on one side of the backing layer.

[0214] 5. The backing layer according to any one of claims 1 to 4, characterized in that the barrier coating comprises 35 wt.% to 65 wt.%, preferably 40 wt.% to 60 wt.%, more preferably 45 wt.% to 55 wt.% of an inorganic filler.

[0215] 6. The backing layer according to any one of claims 1 to 5, characterized in that the barrier coating comprises 65 wt.% to 35 wt.%, preferably 60 wt.% to 40 wt.%, more preferably 55 wt.% to 45 wt.% of a polymer having a glass transition temperature (Tg) of -35 °C to +15 °C.

[0216] 7. The backing layer according to any one of claims 1 to 6, characterized in that the polymer has a glass transition temperature (Tg) of -30 °C to +10 °C, preferably -25 °C to +5 °C.

[0217] 8. The backing layer according to any one of claims 1 to 7, characterized in that the barrier coating comprises 0 to 0.05 wt.% of an antifoaming agent.

[0218] 9. The backing layer according to claim 8, characterized in that the barrier coating comprises 0.01 wt.% to 0.03 wt.% of an antifoaming agent.

[0219] 10. The backing layer according to claim 8 or 9, characterized in that the antifoaming agent is selected from the group consisting of mineral oil-based antifoaming agents, vegetable oil-based antifoaming agents, and silicone oil-based antifoaming agents.

[0220] 11. The backing layer according to any one of claims 1 to 10, characterized in that the first layer is a paper layer having an elongation rate in the machine direction (MD) of 3% to 10%, preferably 5% to 8%, wherein the elongation rate is measured according to DIN EN ISO 1924-2.

[0221] 12. The backing layer according to any one of claims 1 to 11, characterized in that the first layer is a paper layer having an elongation rate in the cross direction (CD) orthogonal to the machine direction (MD) of 5% to 15%, preferably 8% to 12%.

[0222] 13. The backing layer according to any one of claims 1 to 12, characterized in that the first layer is a paper layer having an air resistance (Gurley) permeability of 5 to 25 Gurley, preferably 10 to 20 Gurley, and the permeability is measured according to ISO 5636-5.

[0223] 14. The backing layer according to any one of claims 1 to 13, characterized in that the first layer is a paper layer having a water absorbency (Cobb60) value of 20 to 40 gsm, preferably 25 to 35 gsm, and the water absorbency is measured according to the Cobb60 test method ISO535.

[0224] 15. The backing layer according to any one of claims 1 to 14, wherein the first layer is a paper layer comprising paper selected from the group consisting of bleached or brown kraft paper, bleached or brown sack kraft paper, semi-stretched kraft paper, semi-stretched sack kraft paper, and the paper is preferably semi-stretched sack kraft paper.

[0225] 16. The backing layer according to any one of claims 1 to 15, wherein the first layer is a paper layer comprising paper having a basis weight of 40 to 80 gsm, preferably 50 to 70 gsm.

[0226] 17. The backing layer according to any one of claims 1 to 16, wherein the second layer is a barrier coating comprising an inorganic filler selected from the group consisting of kaolinite, calcined kaolinite, calcium carbonate, precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), talc, mica, clay, silica, precipitated silica, fumed silica, titanium dioxide, or a mixture thereof.

[0227] 18. The backing layer according to any one of claims 1 to 16, wherein the second layer is a barrier coating comprising kaolinite.

[0228] 19. The backing layer according to any one of claims 1 to 18, wherein the second layer is a barrier coating comprising a polymer selected from the group consisting of carboxylated styrene-butadiene rubber, styrene-butadiene rubber, acrylate-based polymer, nitrile rubber, natural rubber, polyvinyl acetate, or a mixture thereof.

[0229] 20. The backing layer according to any one of claims 1 to 18, wherein the second layer is a barrier coating comprising carboxylated styrene-butadiene rubber having a Tg of -27 °C to -23 °C.

[0230] 21. The backing layer according to any one of claims 1 to 18, wherein the second layer is a barrier coating comprising carboxylated styrene-butadiene rubber having a Tg of +3 °C to +7 °C.

[0231] 22. The backing layer according to any one of claims 1 to 21, wherein the second layer is a barrier coating present at a coating weight of 1 to 10 gsm, preferably 3 to 7 gsm.

[0232] 23. The backing layer according to any one of claims 2 to 22, wherein the primer coat comprises a polymer or polymer composition selected from the group consisting of styrene-butadiene rubber, acrylate-based polymer, nitrile rubber, polyvinyl acetate, natural rubber, prevulcanized natural rubber, butyl acrylate; methacrylate-grafted natural rubber, carboxylated styrene-butadiene rubber, and polyurethane.

[0233] 24. The backing layer according to claim 23, characterized in that the primer coat comprises a composition of methacrylate grafted natural rubber and carboxylated styrene butadiene rubber in a ratio of 80:20 to 95:05.

[0234] 25. The backing layer according to any one of claims 2 to 14, characterized in that the primer coat is present at a coat weight of 0.1 to 3 gsm, preferably 0.5 to 2 gsm.

[0235] 26. The backing layer according to any one of claims 4 to 25, characterized in that the release coat comprises a composition containing a polymer selected from the group consisting of hydrophilic acrylic or acrylate polymers; water-based vinyl acetate copolymer latexes.

[0236] 27. The backing layer according to any one of claims 4 to 26, characterized in that the release coat is present at a coat weight of 0.1 to 5 gsm, preferably 0.5 to 4 gsm.

[0237] 28. The backing layer according to any one of claims 1 to 27, characterized in that its repulpability rate exceeds 85% as measured according to the test method for repulping and recycling of Western Michigan University.

[0238] 29. The backing layer according to any one of claims 1 to 28, characterized in that the amount of stickies formed during the papermaking process is less than 5.

[0239] 30. The backing layer according to any one of claims 1 to 29, characterized in that it is suitable for use in tapes.

[0240] 31. A tape comprising a backing layer according to any one of claims 1 to 30.

Claims

1. A backing layer, comprising: A first layer, which is a paper layer; A second layer applied on one or both sides of the first layer, which is a barrier coating, Characterized in that the barrier coating comprises 30% to 70% by weight of an inorganic filler; 70% to 30% by weight of a polymer, the glass transition temperature (Tg) of the polymer being -35°C to +15°C.

2. The backing layer according to claim 1, comprising a primer layer applied to the second layer, the second layer being a barrier coating, wherein, The primer layer is only present on one side of the backing layer.

3. The backing layer according to claim 1, comprising a primer layer applied to the second layer, the second layer being a barrier coating, wherein, The primer layer is present on both sides of the backing layer.

4. The backing layer according to claim 2, comprising a release coating applied to the second layer, the second layer being a barrier coating, wherein, The release coating is only present on one side of the backing layer.

5. The backing layer according to any one of claims 1 to 4, characterized in that, The barrier coating comprises 35 wt.% to 65 wt.%, preferably 40 wt.% to 60 wt.%, more preferably 45 wt.% to 55 wt.% of an inorganic filler.

6. The backing layer according to any one of claims 1 to 5, characterized in that, The barrier coating comprises 65 wt.% to 35 wt.%, preferably 60 wt.% to 40 wt.%, more preferably 55 wt.% to 45 wt.% of a polymer having a glass transition temperature (Tg) of -35°C to +15°C.

7. The backing layer according to any one of claims 1 to 6, characterized in that, The first layer is a paper layer, and its elongation rate in the machine direction (MD) is 3% to 10%, preferably 5% to 8%, where the elongation rate is measured according to DIN EN ISO1924-2.

8. The backing layer according to any one of claims 1 to 7, characterized in that, The first layer is a paper layer, and its elongation rate in the cross direction (CD) orthogonal to the machine direction (MD) is 5% to 15%, preferably 8% to 12%.

9. The backing layer according to any one of claims 1 to 8, characterized in that, The first layer is a paper layer, which comprises paper with a basis weight of 40 to 80 gsm, preferably 50 to 70 gsm.

10. The backing layer according to any one of claims 1 to 9, characterized in that, The second layer is a barrier coating, which comprises an inorganic filler selected from the group consisting of kaolinite, calcined kaolinite, calcium carbonate, precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), talc, mica, clay, silica, precipitated silica, fumed silica, titanium dioxide, or a mixture thereof.

11. The backing layer according to any one of claims 1 to 10, characterized in that, The second layer is a barrier coating, which is present at a coating weight of 1 to 10 gsm, preferably 3 to 7 gsm.

12. The backing layer according to any one of claims 1 to 11, characterized in that, Measured according to the test method of Western Michigan University for repulping and recycling, its repulpability exceeds 85%.

13. The backing layer according to any one of claims 1 to 12, characterized in that, The amount of stickies formed during the papermaking process is less than 15 (further requirements:

1. less than 10, 2. less than 5).

14. The backing layer according to claim 13, characterized in that, The amount of stickies formed during the papermaking process is less than 10.

15. The backing layer according to claim 13, characterized in that, The amount of stickies formed during the papermaking process is less than 5.

16. The backing layer according to any one of claims 1 to 15, characterized in that, It is suitable for tapes.

17. A tape, which comprises the backing layer according to any one of claims 1 to 16.

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