Paper product and topcoat paint thereof

Abstract

The invention provides a paper product and a top coating thereof. The top coating comprises china clay, styrene-acrylic latex, modified polyvinyl alcohol and a water-resistant agent, wherein the glass transition temperature of the styrene-acrylic latex is-5 to 3 DEG C. The topcoat paint of the release paper provided by the embodiment of the invention can be applied to a release paper coating, the coating weight and uniformity of silicone oil on the surface of the release paper can be optimized, and the problems that a glue layer bursts after the release paper is stored for a long time or under the condition of high temperature, the coating and the silicone oil are peeled off, the peeling is poor and the like are solved.

Description

Technical Field

[0001] The present application relates to the technical field of papermaking coating formulations, and in particular to a paper product and a surface coating thereof. Background Art

[0002] Release paper is a kind of anti-sticking paper, which is widely used as the base material of self-adhesive paper. It can isolate adhesives and ensure that the self-adhesive paper can be pasted on other products after being peeled off from the release paper. At present, the domestic release paper industry chain often uses plastic particles (such as polyethylene PE, polypropylene PP, etc.) to coat release paper to produce plastic release paper. Plastic release paper is difficult to degrade naturally during production and waste treatment, causing white pollution. Under the background of the plastic restriction order, the plastic-free release papers currently developed mainly include glassine and CCK release paper (CLAY COATED KRAFT PAPER). CCK release paper is produced by coating a layer of porcelain clay on the surface of base paper. It is a high value-added, energy-saving and environmentally friendly product. At present, its production technology has not yet been fully mastered in China. The important indicators of CCK release paper are mainly silicone oil coating amount, room temperature peeling force, aging peeling force and residual adhesion rate, all of which are related to the barrier ability of CCK release paper. Most of the research literature on CCK release paper in China focuses on the basic elements such as the beating degree, ash content, and latex content of the raw material slurry. A layer of porcelain clay is coated on the surface of the base paper to seal its surface, and latex is used to bond and fill the gaps of the porcelain clay. In the prior art, the porcelain clay coated on the surface of CCK release paper can easily destroy the silicone release agent, which will reduce its barrier properties. The surface silicone oil will penetrate into the interior of the paper, the surface brightness of the silicone coating will decrease, and after long-term storage or under high temperature, the glue layer will burst, the coating and silicone oil will peel off, and the adhesive will not be peeled off well. Summary of the invention

[0003] In a first aspect, an embodiment of the present application provides a top coating for release paper, wherein the top coating comprises: china clay, styrene acrylic latex, modified polyvinyl alcohol and a water-resisting agent; wherein the glass transition temperature of the styrene acrylic latex is -5 to 3°C.

[0004] In some optional embodiments, the added amount of the styrene acrylic latex is 35-40% of the solid content of the coating.

[0005] In some optional embodiments, the modified polyvinyl alcohol includes any one of silanol-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, and maleic anhydride-modified polyvinyl alcohol, or a combination of more than one thereof.

[0006] In some optional embodiments, the added amount of the modified polyvinyl alcohol is 0-5% of the solid content of the coating.

[0007] In some optional embodiments, the amount of the water resistance agent added is 0-2% of the solid content of the coating.

[0008] In some optional embodiments, the water resistance agent includes any one of polyamide polyurea resin, polyamide epichlorohydrin resin, and glyoxal, or a combination of more than one thereof.

[0009] In some optional embodiments, the particle size of the china clay is no greater than 3 microns.

[0010] In some optional embodiments, the top coating further includes carboxymethyl cellulose and a lubricant.

[0011] In a second aspect, an embodiment of the present application provides a paper product, comprising a base paper, wherein the base paper comprises a first surface and a second surface arranged opposite to each other, wherein the first surface is coated with two layers of top coating, wherein both layers of the top coating are made of the top coating material described in the above embodiment.

[0012] In some optional embodiments, the second surface of the base paper is coated with a back coating layer, and the coating of the back coating layer includes: heavy calcium carbonate, oxidized starch and styrene acrylic latex, and the glass transition temperature of the styrene acrylic latex is -5 to 3°C.

[0013] The top coating of the release paper provided in the embodiment of the present application can be applied to the release paper coating, which can optimize the coating amount and uniformity of silicone oil on the release paper surface, and solve the problems of cracking of the glue layer, peeling of the coating and silicone oil, and poor peeling after the release paper is stored for a long time or under high temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0015] Figure 1 It is a schematic diagram of the structural stacking of an embodiment of the paper product of the present application. DETAILED DESCRIPTION

[0016] The present application is further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present application, but are not intended to limit the scope of the present application. Similarly, the following examples are only some embodiments of the present application rather than all embodiments, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0017] The terms "first", "second", and "third" in the embodiments of the present application are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second", and "third" can expressly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the embodiments of the present application, all directional indications (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. The terms "including" and "having" in the embodiments of the present application and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or components inherent to these processes, methods, products, or devices.

[0018] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0019] The embodiment of the present application first provides a top coating of a release paper, wherein the top coating comprises: china clay, styrene acrylic latex, modified polyvinyl alcohol and a water-resisting agent.

[0020] Conventional technical solutions do not consider the possible impact of paper surface pH value and metal ion content on the silicone oil coverage of CCK release paper. However, the topcoat coating in the embodiment of the present application uses porcelain clay with low heavy metal content and particle size ≤ 3 microns, which can solve the above problem.

[0021] Optionally, the top coating in the embodiment of the present application uses styrene acrylic latex with a low glass transition temperature, wherein the top coating in the embodiment of the present application uses a glass transition temperature of -5 to 3°C for styrene acrylic latex, specifically -5°C, -4.8°C, -4.5°C, -4°C, -2°C, -1.7°C, 0°C, 1.2°C, 2.6°C and 3°C. The coating in the conventional technical solution generally uses high Tg latex (about 13-16°C), which has high gloss and smoothness, enhances the anti-pulling strength of the coating, but its flexibility and bonding performance are lower than low Tg latex (-5-3°C). Optionally, the addition amount of styrene acrylic latex in the present embodiment is 35-40% of the solid content of the coating, specifically 35%, 35.5%, 36.4%, 37%, 38.8%, 39%, 40% and other values ​​of the solid content of the coating.

[0022] Wherein, the modified polyvinyl alcohol (PVA) may specifically include any one or a combination of silanol-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, and maleic anhydride-modified polyvinyl alcohol, and is not specifically limited here. Optionally, the amount of modified polyvinyl alcohol added is 0-5% of the solid content of the coating, and specifically can be 0.1%, 0.7%, 1%, 1.2%, 2.5%, 2.8%, 3%, 3.6%, 4%, 4.5%, 4.8%, 5% and other values.

[0023] The water-resistant agent may include any one or a combination of polyamide polyurea resin, polyamide epichlorohydrin resin, and glyoxal, which are not specifically limited here. Optionally, the amount of the water-resistant agent added is 0-2% of the solid content of the coating, specifically 0.1%, 0.3%, 0.7%, 0.82%, 0.9%, 1%, 1.3%, 1.6%, 1.73%, 1.9%, 1.95%, 2%, etc.

[0024] In addition, the topcoat in the embodiment of the present application also includes a dispersant and a defoamer, and the added amount of the two is about 0.15% of the solid content of the coating.

[0025] Optionally, the topcoat in the embodiment of the present application further includes carboxymethyl cellulose and a lubricant; wherein the carboxymethyl cellulose is added in an appropriate amount to control the viscosity, and the viscosity value of the topcoat is between 2500cps and 3000cps, and the viscosity value of the topcoat can be specifically 2500cps, 2600cps, 2750cps, 2800cps, 3000cps, etc. The amount of lubricant added can be about 2% of the solid content of the coating.

[0026] The top coating of the release paper provided in the embodiment of the present application can be applied to the release paper coating, which can optimize the coating amount and uniformity of silicone oil on the release paper surface, and solve the problems of cracking of the glue layer, peeling of the coating and silicone oil, and poor peeling after the release paper is stored for a long time or under high temperature conditions.

[0027] Optionally, the present application embodiment also provides a paper product, see Figure 1 , Figure 1 1 is a schematic diagram of the structural stacking of an embodiment of a paper product of the present application, wherein the paper product includes a base paper 100, wherein the base paper 100 includes a first surface 110 and a second surface 120 disposed opposite to each other, and the first surface is coated with two layers (coated twice) of topcoat 200, wherein both layers of topcoat 200 use the topcoat coating in the aforementioned embodiment. For the specific topcoat coating formula, please refer to the relevant description of the aforementioned embodiment, which will not be repeated here.

[0028] Among them, the second surface 120 of the base paper 100 is coated with a back coating layer 300, and the back coating layer 300 is a single coating. The coating of the back coating layer includes: heavy calcium carbonate, oxidized starch and styrene-acrylic latex. Among them, the pigment of the back coating layer is heavy calcium carbonate, and the styrene-acrylic latex also uses styrene-acrylic latex with a low glass transition temperature (Tg). In this embodiment, the glass transition temperature of the styrene-acrylic latex is -5 to 3°C, and specifically can be -5°C, -4.8°C, -4.5°C, -4°C, -2°C, -1.7°C, 0°C, 1.2°C, 2.6°C and 3°C.

[0029] Among them, the formulas of the top coating and back coating are shown in the following table.

[0030] Topcoat Back coating Calcium carbonate (grade 65) 0 100％ Calcium carbonate (grade 98) 0 0 Calcium carbonate (grade 99) 0 0 porcelain clay 100％ 0 Oxidized starch 0 2-6％ Low Tg Latex 35-40％ About 10% Modified PVA 0-5％ 0 Water resistant agent 0-2％ 0 Lubricants 2％ 0 Carboxymethyl cellulose Appropriate amount, adjust viscosity Appropriate amount, adjust viscosity

[0031] Research on coating formula to improve the barrier properties of CCK release paper. PVA can increase the viscosity and adhesion of the coating and base paper, and improve the fluidity of the coating. Silanol-modified PVA forms Si-OC bonds between PVA and sodium silicate, and has a cross-linked structure, which improves its water resistance and thermal stability. Carboxyl-modified PVA and maleic anhydride-modified PVA can effectively improve their water resistance and thermal stability, and also have excellent cross-linking properties, giving the coating better adhesion and rheology. Water-resistant agents can reduce the water solubility of the coating after drying and film formation, and can also reduce the occurrence of hair loss and powder loss during the printing process. Modified PVA and water-resistant agents can effectively improve the absorbency of CCK release paper, improve the barrier properties of silicone oil, and avoid the difficulty of peeling when the paper is stored for a long time. The use of low Tg latex can give the coating better flexibility, so that the CCK release paper can adapt to folding and curling during the peeling process. Low Tg latex has better adhesion and can well bond porcelain clay and fix porcelain clay on the surface of paper. The pH value of the paper surface and the metal ion content in the coating will affect the activity of the platinum catalyst in the silicone oil curing system. The coating method is used to improve the barrier properties of CCK release paper. Compared with the single-side coating / primer + topcoat method, the double-coating of porcelain clay can give the paper a double silicone oil barrier layer and make the paper highly smooth. A smaller amount of silicone oil can give the paper stronger silicone oil barrier properties. In addition, due to the addition of a large amount of latex, the calendering temperature and pressure should be controlled within an appropriate range to avoid calendering sticking to the roller. The calendering temperature should be controlled within 50°C and the calendering pressure should be controlled at 60kN / m.

[0032] Several specific implementation methods are introduced below.

[0033] Embodiment 1

[0034] 1. Coating preparation

[0035] Back coating: first add 100% GCC and stir at high speed, then add dispersant and defoamer in order, controlling the content at 0.15%; oxidized starch, controlling the content at 5% (coating solid content); low Tg latex, controlling the content at 10%; finally, add appropriate amount of carboxymethyl cellulose and water to adjust the viscosity to prepare a back coating with a solid content of 58% and a viscosity of 2800cps.

[0036] Top coating: first add 100% of porcelain clay and stir at high speed, then add dispersant and defoamer in order, controlled at 0.15%; low Tg latex, controlled at 35%; modified PVA, controlled at 3%, water-resistant agent, controlled at 2%; appropriate amount of carboxymethyl cellulose and water to adjust the viscosity, prepare a top coating with a solid content of 62% and a viscosity of 2800cps; finally add lubricant, controlled at 2%.

[0037] 2. Paint coating

[0038] Base paper selection: Basis weight controlled at 62±4g / m 2 , folding resistance ≥15, interlacing ≥35. Scraper coating is performed on the selected base paper, and the total coating amount is controlled at 20g / m 2 The coating weight of the double-layer coating on the front side is (9+9) g / m 2 , reverse side back coating 2g / m 2 The speed of the coating machine is controlled by the drying speed of the coating, and the oven temperature after each coating is controlled at 150℃.

[0039] 3. Calendering

[0040] The calendering temperature is controlled within 50℃, and the calendering pressure is controlled at 60kN / m to prevent the roller from sticking during the paper-making process, and obtain CCK release paper with high flatness and high barrier properties, with a basis weight of 80g / m 2 .

[0041] Embodiment 2

[0042] 1. Coating preparation

[0043] Back coating: first add 100% GCC and stir at high speed, then add dispersant and defoamer in order, controlling the content at 0.15%; oxidized starch, controlling the content at 5%; low Tg latex, controlling the content at 10%; finally, add appropriate amount of carboxymethyl cellulose and water to adjust the viscosity, and prepare a back coating with a solid content of 58% and a viscosity of 2800cps.

[0044] Top coating: first add 100% of porcelain clay and stir at high speed, then add dispersant and defoamer in order, controlled at 0.15%; low Tg latex, controlled at 35%; modified PVA, controlled at 5%, water-resistant agent, controlled at 2%; appropriate amount of carboxymethyl cellulose and water to adjust the viscosity, prepare a top coating with a solid content of 62% and a viscosity of 2800cps; finally add lubricant, controlled at 2%.

[0045] 2. Paint coating

[0046] Base paper selection: Basis weight controlled at 90±4g / m 2 , folding resistance ≥15, interlacing ≥40. Apply the coating by scraper coating on the selected base paper, and the total coating amount is controlled at 20g / m 2 The coating weight of the double-layer coating on the front side is (9+9) g / m 2 , reverse side back coating 2g / m 2 The speed of the coating machine is controlled by the drying speed of the coating, and the oven temperature after each coating is controlled at 150℃.

[0047] 3. Calendering

[0048] The calendering temperature is controlled within 50℃, and the calendering pressure is controlled at 60kN / m to prevent the roller from sticking during the paper-making process. The CCK release paper with high flatness and high barrier properties is obtained, and the basis weight is 110g / m 2 .

[0049] Embodiment 3

[0050] 1. Coating preparation

[0051] Back coating: first add 100% GCC and stir at high speed, then add dispersant and defoamer in order, controlled at 0.15% content; oxidized starch, controlled at 5% content; low Tg latex, controlled at 10% content; finally add appropriate amount of carboxymethyl cellulose and water to adjust the viscosity, and prepare a back coating with a solid content of 58% and a viscosity of 2800cps;

[0052] Top coating: first add 100% of porcelain clay and stir at high speed, then add dispersant and defoamer in order, controlled at 0.15%; low Tg latex, controlled at 35%; modified PVA, controlled at 5%, water-resistant agent, controlled at 2%; appropriate amount of carboxymethyl cellulose and water to adjust the viscosity, prepare a top coating with a solid content of 62% and a viscosity of 2800cps; finally add lubricant, controlled at 2%.

[0053] 2. Paint coating

[0054] Base paper selection: Basis weight controlled at 118±4g / m 2 , folding resistance ≥15, interlacing ≥45. Apply the coating by scraper coating on the selected base paper, and the total coating amount is controlled at 20g / m 2 The coating weight of the double-layer coating on the front side is (9+9) g / m 2 , reverse side back coating 2g / m 2 The speed of the coating machine is controlled by the drying speed of the coating, and the oven temperature after each coating is controlled at 150℃.

[0055] 3. Calendering

[0056] The calendering temperature is controlled within 50℃, and the calendering pressure is controlled at 60kN / m to prevent the roller from sticking during the paper-making process. The CCK release paper with high flatness and high barrier properties is obtained, and its basis weight is 140g / m 2 .

[0057] Embodiment 4

[0058] 1. Coating preparation

[0059] Back coating: first add 100% GCC and stir at high speed, then add dispersant and defoamer in order, controlling the content at 0.15%; oxidized starch, controlling the content at 5%; low Tg latex, controlling the content at 10%; finally, add appropriate amount of carboxymethyl cellulose and water to adjust the viscosity, and prepare a back coating with a solid content of 58% and a viscosity of 2800cps.

[0060] Top coating: first add 100% of porcelain clay and stir at high speed, then add dispersant and defoamer in order, controlled at 0.15% content; low Tg latex, controlled at 40% content; modified PVA, controlled at 5% content; appropriate amount of carboxymethyl cellulose and water to adjust the viscosity, prepare a top coating with a solid content of 57% and a viscosity of 3200cps; finally add lubricant, controlled at 2% content.

[0061] 2. Paint coating

[0062] Base paper selection: Basis weight controlled at 118±4g / m 2 , folding resistance ≥15, interlacing ≥45. Apply the coating by scraper coating on the selected base paper, and the total coating amount is controlled at 20g / m 2 , where the front double-layer coating controlled coating amount is (9+9) g / m 2 , reverse side back coating 2g / m 2 The speed of the coating machine is controlled by the drying speed of the coating, and the oven temperature after each coating is controlled at 150℃.

[0063] 3. Calendering

[0064] The calendering temperature is controlled within 50℃, and the calendering pressure is controlled at 60kN / m to prevent the roller from sticking during the paper-making process. The CCK release paper with high flatness and high barrier properties is obtained, and its basis weight is 140g / m 2 .

[0065] Coating test items: including water retention and high shear. Paper physical property test items: including gloss, PPS roughness, BEKK smoothness, air permeability, oil COBB, water COBB.

[0066] The detection parameters of the comparative example are shown in the following table.

[0067]

[0068] After double-sided coating, the oil COBB of the paper is controlled at 0.5g / m 2The results show that the CCK release paper prepared by double coating has a high barrier effect on oil. The low heavy metal content porcelain clay and low Tg latex formula can bring better flatness, anti-penetration and silicone oil curing performance to the CCK release paper, and can optimize the coating amount and uniformity of silicone oil on the release paper surface, and solve the problems of glue layer bursting, coating and silicone oil peeling, and poor peeling after long-term storage or at high temperature.

[0069] The above descriptions are only some embodiments of the present application, and do not limit the protection scope of the present application. Any equivalent device or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A surface coating for release paper, characterized in that: The top coating comprises: china clay, styrene acrylic latex, modified polyvinyl alcohol and a water-resisting agent; wherein the glass transition temperature of the styrene acrylic latex is -5 to 3°C.

2. The topcoat according to claim 1, characterized in that: The added amount of the styrene acrylic latex is 35-40% of the solid content of the coating.

3. The topcoat according to claim 1, characterized in that: The modified polyvinyl alcohol includes any one of silanol-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, and maleic anhydride-modified polyvinyl alcohol, or a combination of multiple thereof.

4. The topcoat according to claim 3, characterized in that: The added amount of the modified polyvinyl alcohol is 0-5% of the solid content of the coating.

5. The top coating according to claim 1, characterized in that: The amount of the water-resistant agent added is 0-2% of the solid content of the coating.

6. The topcoat according to claim 5, characterized in that: The water resistance agent includes any one of polyamide polyurea resin, polyamide epichlorohydrin resin and glyoxal or a combination of multiple thereof.

7. The topcoat according to claim 1, characterized in that: The particle size of the porcelain clay is no greater than 3 microns.

8. The topcoat according to claim 1, characterized in that: The top coating also includes carboxymethyl cellulose and a lubricant.

9. A paper product, characterized in that: The paper product comprises base paper, wherein the base paper comprises a first surface and a second surface arranged opposite to each other, wherein the first surface is coated with two layers of top coating, wherein the two layers of top coating are both made of the top coating material according to any one of claims 1 to 8.

10. The paper product according to claim 9, characterized in that: The second surface of the base paper is coated with a back coating layer, wherein the coating of the back coating layer comprises: heavy calcium carbonate, oxidized starch and styrene acrylic latex, and the glass transition temperature of the styrene acrylic latex is -5 to 3°C.

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