Process for the manufacture of paper substrates with high content of functional vinyl groups suitable for release liners and products and uses thereof

Abstract

The present invention relates to a method for manufacturing a paper substrate suitable for incorporating silicones in catalytic hydrosilylation reactions, and to the product thereof, the paper substrate comprising a cellulosic fiber-based paper and a polymeric primer layer, wherein the polymeric primer layer comprises a polymer containing an amount of functional vinyl groups equal to or higher than 0.5 millimoles per gram of polymer, so that the surface of the polymeric primer layer is hydrophobic. Advantageously, a high vinyl content polybutadiene, which can be obtained from the 1,2-addition polymerization of 1,3-butadiene, can be used in the polymeric primer layer.

Description

Technical Field

[0001] This invention relates to paper substrates containing high-vinyl-content polymers suitable for use in catalytic hydrosilylation reactions involving the binding of silicones. The invention also relates to methods for manufacturing such paper substrates. Furthermore, the invention relates to the use of high-vinyl-content polybutadiene in methods for manufacturing paper substrates containing high-vinyl-content polymers. Background Technology

[0002] A release liner refers to a product comprising a paper substrate and a release layer (i.e., a cured release coating) applied to at least one side of the paper substrate, said release layer being, for example, a silicone-based release layer. The release layer has a release surface facing away from the paper substrate, with a surface energy level typically in the range of 21 to 25 dynes / cm. The release surface of the release layer serves to protect the adhesive material in contact with it.

[0003] Paper used as the substrate for siliconization, such as glassine or supercalendered kraft paper, is typically made from bleached chemical pulp (e.g., bleached kraft pulp) to provide a dimensionally stable and dense paper surface that reduces surface penetration of the release coating when it is applied. Surface penetration can be further reduced by applying a coating (i.e., a base coat) to the paper surface and / or by calendering the paper before applying the release layer. The base coat typically applied to the paper surface is the surface coating. Conventional surface coatings, also known as "surfacesize," improve surface smoothness and reduce porosity, thus acting as a barrier between the release layer and the paper surface.

[0004] Release coatings based on silicone polymers are generally easy to apply and have good flowability. Unless the paper surface is sufficiently hydrophobic, uncured silicone polymers can easily penetrate into the paper's pores. Silicone curing refers to the thermally induced crosslinking reaction of the silicone polymer once applied to the substrate surface, resulting in a crosslinked surface coating adhering to the substrate. Release coatings have previously been cured by radiation, where the coating contains an initiator in its formulation (e.g., a photoinitiator sensitive to ultraviolet light), or curing relies on high-energy radiation (e.g., an electron beam) to generate sufficient energy to initiate the crosslinking reaction. Radiation-cured layers function by breaking chemical bonds and / or generating ions, resulting in a cured silicone polymer-based release layer without the need for additional heat.

[0005] Thermocurable release coatings refer to a specific type of release coating distinct from radiation-curable systems. Low-temperature curable silicone polymers, or "LTC" silicone polymers, are addition-curable polymers comprising a silicone base polymer with functional vinyl groups and a crosslinking agent compound with silane groups, configured to crosslink in a catalytic hydrosilylation reaction at low temperatures. In the presence of a noble metal catalyst such as a platinum or rhodium complex, the silane groups undergo an addition reaction with the vinyl groups. The addition reaction is typically catalyzed by a platinum catalyst. Platinum-catalyzed addition reactions are rapid, and the curing rate can be controlled by the curing temperature. Herein, low temperature refers to a catalytic hydrosilylation temperature below 120°C, preferably in the range of 55 to 110°C, in which the silane groups and functional vinyl groups form a covalently crosslinked structure within the release coating, thereby forming a cured release layer. Novel fast-curing silicone polymers are often further designed to function in conjunction with small amounts of platinum catalysts.

[0006] A problem with fast-curing silicone polymers is the relatively low anchoring strength of the release coating applied to paper substrates. Furthermore, due to the large volume of release liner materials produced, there has been a consistent goal of reducing the amount of platinum catalyst from the current 50-35 ppm level to even lower levels, such as 30 ppm or less. Since fast-curing silicone polymers are widely used in release liner materials, there is a continuous need to save costs by using less platinum. Platinum is a very expensive catalyst material. Additionally, the amounts of other reagents, such as the amount of silicone used for the release coating, are cost factors that need to be minimized. Another challenge is the curing temperature, which refers to the lowest temperature at which the silicone polymer begins to crosslink to obtain a fixed layer structure with release properties. The curing temperature should be kept relatively low to save on production costs incurred due to heating. However, very low curing temperatures, such as below 45°C, can cause problems because the silicone polymer may subsequently begin to crosslink prematurely, for example, before it is applied to the paper substrate surface. The importance of these parameters is emphasized as machine speeds increase.

[0007] To date, the anchoring properties of fast-curing silicone polymers on paper substrates have been improved by using a base coat containing a chemically post-treated polymer (e.g., water-soluble polyvinyl alcohol), which has been modified to include functional vinyl groups. In the chemical post-treatment of polyvinyl alcohol, the reaction typically occurs via highly reactive hydroxyl groups. Hydroxyl-containing polymers most commonly react with carbonyl-containing compounds. Carbonyl groups can be oxidized and can undergo addition reactions under alkaline or neutral conditions. Therefore, polymer modification is carried out by reacting carbonyl groups with one or more hydroxyl groups of the polymer, thereby providing a water-soluble polymer modified to include functional vinyl groups. Examples of carbonyl compounds are aldehydes, carboxylic acids, esters, acid anhydrides, and acyl halides. Examples of chemical post-treatment of polyvinyl alcohol via carbonyl reactions are disclosed in publications WO 2009 / 147283 and WO 2011 / 104427, which disclose methods for grafting PVA polymers with organic molecules to provide vinyl-functionalized PVA polymers.

[0008] However, a drawback associated with the chemical post-treatment of polyvinyl alcohol (PVA) is that the solution rapidly becomes highly viscous and its water solubility decreases as the amount of further vinyl-containing carbonyl compounds is increased in such post-treatment reactions. Therefore, the solubility of the compounds significantly limits the number of vinyl side groups that can be grafted onto the PVA polymer. Attempts to increase the aldehyde content in the reaction solution greatly increase the viscosity of the solution, causing the reactants to precipitate prematurely from the solution. For example, when grafting PVA with a degree of hydrolysis of 98-99% and a degree of polymerization of 1400 with undecenoal (an aldehyde containing 11 carbon atoms), the polymer typically already exhibits significantly reduced water solubility when undecenoal is added to the reaction mixture in amounts exceeding 2% by weight (expressed as grams of aldehyde compound per 100 grams of PVA). Consequently, the resulting reaction product becomes highly viscous and very difficult to apply as a coating to a substrate surface. Therefore, the amount of vinyl side chains in the modified PVA polymer remains relatively low, which is generally necessary for current high-speed peel-off lining applications.

[0009] Because the amount of functional vinyl groups that can be easily grafted into PVA polymers is very limited, previous solutions could not provide a substrate without defects in high-speed labeling applications. The higher the speed in the labeling process, the smaller the acceptable amount of silicone anchoring defects in the peel liner. Summary of the Invention

[0010] The silicone-based release layer comprises a base polymer containing functional vinyl groups (-CH=CH2) and a crosslinking agent compound containing silane (Si-H) groups. Novel fast-curing silicones can possess molecular structures with higher degrees of branching than previous generations. The branched molecular structure allows for faster reaction kinetics when the functional vinyl groups (-CH=CH2) and the crosslinking agent compound containing silane (Si-H) bonds are crosslinked. Therefore, the novel fast-curing silicone requires less time for the addition curing reaction.

[0011] According to one aspect of the invention, a selectively addition-polymerized diene can be used to provide an oleophilic primer, the primer comprising a polymer having a large number of functional vinyl groups but no styrene groups. Therefore, by providing a paper substrate having a primer surface containing a large number of functional vinyl groups throughout the entire primer surface plane, the anchoring of the release layer to the paper substrate can be improved. Primers comprising polymers with high vinyl content provide an unprecedented means of improving the anchoring properties of silicone-based release layers. In addition to the fast-curing silicone polymers already specifically mentioned, the covalent bonding of other silicone polymers based on addition-curable crosslinking agent compounds containing silane bonds can also be improved.

[0012] Methods for producing polymers with high vinyl content but without a large number of hydroxyl groups may include the selective polymerization of diene monomers. In particular, methods for producing polymers with high vinyl content may include reacting diene monomers having two or more vinyl groups in the presence of a catalyst selective for addition reactions. The percentage of repeating units in the vinyl-containing polymer can be adjusted by selecting polymerization conditions and a suitable catalyst. A suitable catalyst is, for example, butyllithium. 1,3-Butadiene monomers exhibit high selectivity for 1,2-addition reactions in the presence of butyllithium, thereby producing polybutadiene with high vinyl content and without a large number of hydroxyl groups. Polybutadiene with high vinyl content can have a vinyl content of up to 18.5 mmol / g, where the vinyl content represents the molar concentration of functional groups in the polymer formed.

[0013] The abundant functional vinyl groups on the dienes produced by selective addition polymerization provide compositions that can be coated onto cellulose fiber-based paper, thereby providing the substrate with improved anchoring properties to silanol groups. Another advantage of this oleophilic primer is the hydrophobicity of the surface. The hydrophobic primer can resist the penetration of various substances, such as water-based adhesives, that may come into contact with the hydrophobic polymer coating. The hydrophobic polymer also ensures uniform properties across the entire surface, despite the possible defects, such as pores, that may sometimes be present in the cellulose fiber-based paper.

[0014] Such hydrophobic polymer coatings exhibit poor adhesion to silicone. Furthermore, silicone adhesion to hydrophobic polymer coatings is inversely proportional to the coating speed. Higher coating and curing speeds result in lower silicone adhesion. However, when cellulose fiber-based paper is coated with a base coat containing a nonpolar polymer with a high vinyl content and low hydroxyl content, this polymer exhibits a hydrophobic tendency and avoids the hydrophilic surface of the cellulose fiber-based paper. Thus, despite the poor silicone adhesion of the hydrophobic polymer coating, catalytic hydrosilylation allows the silicone to chemically bond with the functional vinyl groups present in the polymer. The hydrophobic surface on the cellulose fiber-based paper has the advantage of reducing the amount of adhesive penetrating through the release layer into the underlying cellulose fiber-based paper when the paper substrate is used as a release liner substrate. This also reduces the minimum force required to separate labels or excess matrix material.

[0015] Another effect of the hydrophobic surface on cellulose fiber-based paper is that, since the minimum force required to detach the label from the release liner depends on the thickness of the release layer, the hydrophobic surface can reduce the thickness of the release layer. Therefore, the hydrophobic surface helps to reduce the amount of silicone and platinum required to provide the release layer. A thinner release layer further enables lower high-speed peel values. The polymer does not contain a large number of hydroxyl groups, so when coated onto a hydrophilic surface such as cellulose fiber-based paper, the vinyls tend to oriented away from that surface. A particular advantage of the undercoat containing functional vinyls in the polymer at an amount equal to or greater than 0.3 mmol / g, preferably equal to or greater than 0.5 mmol / g, is that the large amount of functional vinyls allows the use of very fast-curing silicone compounds in the release coating. When the amount of functional vinyls contained in the polymer is equal to or greater than 0.5 mmol / g, this allows for the formation of a tightly closed paper substrate with an oleophilic surface. The cellulose fiber-based paper can be, for example, with a basis weight equal to or greater than 38 g / m². 2 For example, 38 to 160 g / m 2 Coated paper within a certain range. Therefore, the formed paper substrate can be arranged to have a tight, closed surface with oleophilic properties similar to those of synthetic paper substrate surfaces. Traditionally, synthetic materials such as polypropylene tend to have low surface energy levels, and the anchoring of silicone to the substrate surface is reduced. However, the anchoring properties of silicone polymers cured by addition polymerization are improved because a much higher amount of vinyl can be provided on the paper substrate surface than described in the prior art.

[0016] Although styrene-butadiene copolymer (SBR) emulsions are widely used in coated paper due to their low manufacturing cost, they are generally unsuitable for use as a base coat in release lining applications. Styrene-butadiene copolymers (also known as SBR or SB-latex) used for paper coatings are typically produced in the presence of emulsifiers (surfactants such as various soaps). Emulsifiers are used to control the molecular weight of the resulting copolymer product and thus its viscosity, but they do not remain attached during copolymer formation; instead, they readily separate and float to the surface during coating manufacturing.

[0017] The polymeric diene containing functionalized vinyl groups can be further configured to contain unsaturated dicarboxylic acids or their anhydrides or monoesters, such as maleic acid or maleic anhydride. Preferably, the polymeric undercoat with a large number of functionalized vinyl groups on top of the cellulose fiber-based paper is free of styrene groups. This results in a paper substrate having a surface (free of styrene groups). The lack of styrene groups in the polymeric undercoat is related to the theoretical amount of functionalized vinyl groups available on the polymer formed from monomers. Advantageously, the amount of functionalized vinyl groups in the polymer formed from monomers is maximized, which improves the hydrophobicity of the polymer, as is the case with polybutadiene, which can be obtained from 1,3-butadiene monomers via 1,2-addition polymerization. However, further introducing polar groups into the polymer structure, such as covalent grafting of unsaturated dicarboxylic acids, anhydrides, or their monoesters, will consume the functionalized vinyl groups of the polymer. Therefore, the polar groups of the vinyl groups covalently grafted into the polymer structure replace some of the functionalized vinyl groups of the polymer. However, the amount of polar groups covalently grafted onto the polymer structure can be used to control the hydrophobicity of the polymer, thereby selecting the properties exhibited by the polymer in water. The balance between the hydrophobicity and hydrophilicity of the polymer can be used to reduce problems typically associated with emulsifiers, which tend to easily separate and float to surfaces. Therefore, such polar groups in the polymer composition can be configured to alter the degree of hydrophobicity of the polymer composition. In particular, the polymerized diene can be configured to contain hydrophilic groups to improve the water solubility of the polymer composition, thereby facilitating the application of the polymer to cellulose fiber-based paper layers. That is, depending on the degree of polymerization and the amount of hydrophilic groups other than functional vinyl groups, the polymer composition can be water-soluble or can be applied in the form of an aqueous emulsion or aqueous dispersion. Advantageously, the amount of unsaturated dicarboxylic acid or its anhydride or monoester can be equal to or greater than 3 mol% of the polymer. An amount of unsaturated dicarboxylic acid or its anhydride or monoester in the range of 3 to 6 mol% is expected to provide suitable conditions for aqueous emulsions. A water-soluble polymer composition can be obtained when the amount of an unsaturated dicarboxylic acid or its anhydride or monoester is equal to or greater than 20 mol% and the solution has an alkaline pH, preferably greater than 8. Sodium salts can be used to improve the solubility and stability of the polymer composition. Therefore, methods for manufacturing polymers with high vinyl content can further include grafting an unsaturated dicarboxylic acid or its anhydride or monoester, such as maleic acid or maleic anhydride, onto the polymer with high vinyl content, thereby altering the hydrophobicity of the polymer.

[0018] According to one aspect of the invention, a paper substrate is provided that is suitable for incorporating silicone in a catalytic hydrosilylation reaction, the paper substrate comprising:

[0019] - Cellulose fiber-based paper, and

[0020] -Polymer base coating,

[0021] The polymer base coating comprises a polymer containing functional vinyl groups in an amount equal to or greater than 0.5 mmol / g, such that the surface of the base coating is hydrophobic. The functional vinyl groups present on the surface of the base coating are capable of forming covalent bonds with a silicone-based release layer, which can be applied on top of the hydrophobic base coating.

[0022] According to another aspect of the present invention, a method for manufacturing a paper substrate adapted to incorporate silicone in a catalytic hydrosilylation reaction is provided, the method comprising:

[0023] -Provide cellulose fiber-based paper, and

[0024] - A polymer primer is applied to the top of a cellulose fiber-based paper layer to form a paper substrate with a polymer primer coating.

[0025] The polymer base coating comprises a polymer containing functional vinyl groups in an amount equal to or greater than 0.5 mmol / g per gram of polymer, such that the surface of the base coating (PRIM1) is hydrophobic, and the functional vinyl groups are capable of forming covalent bonds with a silicone-based release layer (SIL1) that can be applied to the top of a paper substrate (SUBST1).

[0026] Advantageously, the polymer base coating is made of or contains a polymeric diene compound that includes functional vinyl functional groups, such as polybutadiene with a high vinyl content obtained by 1,2-addition polymerization of 1,3-butadiene.

[0027] This paper substrate can be used in a method for manufacturing a peelable liner, the method comprising:

[0028] -Provide cellulose fiber-based paper, and

[0029] - A polymer primer is coated on top of cellulose fiber-based paper. The polymer primer contains functional vinyl groups in an amount equal to or greater than 0.5 mmol / g per gram of polymer, thereby forming a paper substrate having a hydrophobic surface layer containing functional vinyl groups.

[0030] - A hydrophobic surface layer is applied using a silicone-based release layer containing silanol groups, and

[0031] - The silicone-based release layer is cured by addition polymerization, thereby anchoring the silicone-based release layer containing silanol groups to a hydrophobic surface layer containing functional vinyl groups, thereby forming a release liner.

[0032] Therefore, a peelable liner is also provided, comprising:

[0033] - Cellulose fiber-based paper

[0034] - A hydrophobic surface layer comprising a polymerized diene, such as 1,2-addition polymerized polybutadiene, and

[0035] - A silicone-based release layer applied on top of the hydrophobic surface layer.

[0036] Among them, the silicone-based release layer has been covalently anchored to the hydrophobic surface layer through a catalytic hydrosilylation reaction.

[0037] High-vinyl-content polybutadiene, obtainable via 1,2-addition polymerization, can be used in undercoating compositions for paper substrates, which are suitable for incorporating silicones in a catalytic hydrosilylation reaction. The polymerized diene compound may further comprise an unsaturated dicarboxylic acid or its anhydride or monoester, such as maleic acid or maleic anhydride.

[0038] Advantageously, the polymer undercoat comprises a polymer containing functional vinyl groups in an amount equal to or greater than 2 mmol / g, preferably equal to or greater than 4 mmol / g, and most preferably equal to or greater than 8 mmol / g. A higher amount of functional vinyl groups is directly related to the hydrophobicity of the surface, thereby reducing the surface energy while still allowing the silicone polymer to cure via addition polymerization. Experimental results show that a maximum of 18.5 mmol / g of functional vinyl groups can be obtained on a undercoat applied over a cellulose fiber-based paper layer. Therefore, the amount of functional vinyl groups can range from 0.5 to 18.5 mmol / g of polymer, which represents the molar concentration of vinyl groups in the polymer.

[0039] The invention is further described in the independent and dependent claims. Brief description of the attached figures

[0040] Figure 1 The addition polymerization reaction of rapidly curing silicone polymers in the presence of a platinum catalyst is illustrated by way of example.

[0041] Figure 2 An illustrative example is shown of a face material laminate attached to a release liner, the face material laminate comprising a face layer and an adhesive layer.

[0042] Figure 3 An illustrative example is shown of a base coating comprising a polymer with a high vinyl content, applied to the surface of a cellulose fiber-based paper.

[0043] Figure 4 An illustrative method is shown for producing high vinyl content polymers from 1,3-butadiene monomers via 1,2-addition polymerization in the presence of a selective catalyst.

[0044] Figure 5The method of modifying the hydrophobicity of polymers containing a large number of functional vinyl groups by grafting the polymer with unsaturated dicarboxylic acids, their anhydrides, or monoesters is illustrated by way of example.

[0045] Figure 6a An illustrative example is shown of a product comprising a cellulose fiber-based paper surface coated with a primer containing a high vinyl content polymer, prior to a silicone crosslinking reaction occurring between the high vinyl content polymer and a fast-curing silicone polymer applied on top of the functional vinyl-containing primer.

[0046] Figure 6b An illustrative example is shown of a product comprising a cellulose fiber-based paper surface coated with a base coat containing a polymer with a high vinyl content, which has undergone at least some degree of silicone crosslinking reaction between the high vinyl content polymer and a fast-curing silicone polymer applied on top of the functional vinyl-containing base coat.

[0047] The attached diagram is illustrative.

[0048] In the diagram, S X and S Z Indicates orthogonal directions.

[0049] Detailed description

[0050] refer to Figure 1 and Figure 2 Rapidly curable silicone polymers are typically cured via addition polymerization. A silicone-based release layer SIL1 (such as...) can be formed in the addition polymerization of a silicone base polymer containing a functional vinyl group (VIN1) and a crosslinking agent compound (SH1) containing silicon-hydrogen bonds. Figure 2 (As shown). The functional vinyl group VIN1 can be an end group or can be located at other positions in the silicone base polymer. Addition polymerization refers to a silicone crosslinking reaction in which the silicone base polymer containing the functional vinyl group VIN1 is configured to form a covalent bond with the crosslinking agent compound SH1 in the presence of a catalyst compound. The catalyst compound is typically a metal catalyst, such as a platinum catalyst abbreviated as Pt. Fast-curing silicone polymers are typically crosslinked at or below 100°C, for example, at temperatures in the range of 60 to 100°C. The activation temperature range and reaction kinetics can be adjusted by selecting the chemical composition of the silicone base polymer containing the functional vinyl group VIN1 and the chemical composition of the crosslinking agent compound SH1. Compositions with crosslinking temperatures close to room temperature (around 25°C) are not preferred, as this increases the risk of premature crosslinking of the silicone before the compound is applied to the substrate surface.

[0051] refer to Figure 2 and Figure 3The release liner REL1 may include a cellulose fiber base paper PAP1, which may be cellulose fiber-based; a release layer SIL1 formed of silicone resin; and an oleophilic undercoat PRIM1 between the cellulose fiber base paper PAP1 and the release layer SIL1. The release liner REL1 may be used as a backing material for a face sheet laminate FILM1. The face sheet laminate FILM1 is used to manufacture adhesive labels. In such manufacturing, portions of the face sheet laminate FILM1 may be manufactured, for example, by cutting discrete labels LAB1 from the face sheet laminate FILM1. The adhesive labels LAB1 may be, for example, self-adhesive labels or pressure-sensitive labels formed from the face sheet laminate FILM1. The release liner REL1 is provided with a release surface to facilitate the separation of the face sheet laminate FILM1 containing the adhesive layer ADH1 from the release liner REL1.

[0052] The paper substrate SUBST1 used for the release liner REL1 represents a combination of at least a cellulose fiber base paper PAP1 and a base coating PRIM1 applied to at least one side of the cellulose fiber base paper PAP1. The base coating PRIM1 is typically applied to one or more sides on which a silicone-based release layer SIL1 is intended to be coated. Advantageously, the base coating PRIM1 is an oleophilic base coating comprising a polymeric diene PBUT1 having vinyl functional groups, said polymeric diene PBUT1 being present in the composition of the oleophilic base coating PRIM1. When the release liner REL1 is formed, the base coating PRIM1 is formed between the cellulose fiber base paper PAP1 and the silicone-based release layer SIL1.

[0053] Methods for manufacturing release liner REL 1 may include providing cellulose fiber base paper PAP1. Examples of commodities commonly used as the substrate for release liner paper SUBST1 are coated paper, vegetable parchment paper, glassine paper, and greaseproof paper. Typical examples of coated paper are supercalendered kraft paper (SCK) and glassine paper. Glassine paper generally refers to paper made from chemical pulp with a coating weight (grammage) typically between 50 and 150 g / m². 2 Within a certain range. Glassine paper has a good level of transparency; for example, when measured with visible light (ISO 2469:1994), 60 g / m² 2 Glassine paper typically has a transparency level of at least 45%. Other examples of coated paper are clay-coated kraft paper (CCK), machined kraft paper (MFK), and machine-made glossy paper (MG). The basis weight of coated paper can be equal to or greater than 38 g / m². 2 For example, in the range of 38 to 160 g / m 2 Within the range.

[0054] The method for manufacturing the release liner REL1 can further include applying a base coating PRIM1 to the surface of the cellulose fiber base paper PAP1. The base coating PRIM1 may comprise a high-vinyl content polymer PBUT1, such as a polymer diene containing functional vinyl groups (VIN1), which is applied as a coating onto the top of the cellulose fiber base paper PAP1 to form the paper substrate SUBST1. Paper manufacturers typically supply the cellulose fiber base paper PAP1 as the paper substrate SUBST1 including the base coating PRIM1.

[0055] The surface of the base coating PRIM1 can be configured to be hydrophobic. When the base coating PRIM1 is configured to contain a polymer having a chain-like carbon structure (e.g., a linear chain of carbon without hydroxyl groups), the nonpolar properties of the polymer are enhanced. Therefore, when such a polymer is applied to the surface of the base coating, it provides hydrophobicity and is thus likely oleophilic. The surface of the hydrophobic base coating PRIM1 can improve the orientation of the functional vinyl VIN1 toward the surface of the base coating PRIM1, thereby promoting the formation of covalent bonds with the silicone-based release layer SIL1 after the release coating is applied on top of the hydrophobic base coating PRIM1. Thus, the paper substrate SUBST1 can be configured to have an oleophilic base coating PRIM1 applied on top of the cellulose fiber-based paper PAP1, and covalent bonds will be formed during silicone crosslinking, wherein the silanol groups of the crosslinking agent react with the vinyl VIN1 of the high vinyl content polymer PBUT1.

[0056] The method for manufacturing the release liner REL1 may further include coating an oleophilic primer PRIM1 with a silicone-based release layer SIL1. The silicone-based release layer SIL1 may comprise a fast-curing silicone polymer comprising a crosslinking agent compound having silanol groups. The silicone-based release layer SIL1 can be cured by an addition polymerization reaction in the presence of a catalyst, thereby anchoring the polymer diene of the oleophilic primer to the silicone-based release layer SIL1, thus forming the release liner REL1. The hydrophobicity of the primer PRIM1 improves the spreading of the silicone polymer applied to the paper substrate SUBST1, thereby enabling a reduction in the amount of silicone polymer required to form the silicone-based release layer SIL1. The silicone-based release layer SIL1 can be applied some time after manufacturing the paper substrate SUBST1 or immediately thereafter, for example, during the manufacturing of the face material FILM1. Alternatively, the silicone-based release layer SIL1 can be applied to the paper substrate SUBST1 during the manufacturing process, or immediately after the manufacturing of the paper substrate SUBST1, for example, in the same production process and / or production line. Another advantage of hydrophobicity is that a thinner release layer SIL1 can be provided, thereby reducing the amount of silicone polymer required to form the silicone-based release layer SIL1. Subsequently, this will reduce the amount of platinum catalyst required. Therefore, the silicone-based release layer can remain thin, for example, less than 1 micrometer in thickness. Thus, the hydrophobic (i.e., oleophilic) paper substrate surface promotes the uniform spreading of the uncured silicone polymer applied to that surface. When the release liner paper substrate contains a polymer and the amount of functional vinyls contained in that polymer is equal to or greater than 0.5 mmol per gram of polymer, the release layer SIL1 bonds more firmly to the paper substrate. A hydrophobic undercoat can be used to resist the penetration of water-based or hot-melt adhesive materials used in the manufacture of the face stock FILM1 and thus in contact with the surface of the paper substrate SUBST1. The hydrophobic polymer also makes the properties of the entire surface, such as peel properties, uniform, despite the possible defects, such as pores, which may sometimes be present in the cellulose fiber base paper.

[0057] A removable facesheet FILM1 can be attached to the release liner REL1. The facesheet FILM1 may comprise a face layer FACE1 and an adhesive layer ADH1 for attaching the facesheet FILM1 to the surface of the release liner REL1. The facesheet FILM1 can be used, for example, to manufacture label stock. Here, the release liner REL1 carrying multiple adhesive labels is referred to as a label stock. Label stocks are typically wound on a roll and used in the labeling process, during which the label stock is unfolded as a label as needed.

[0058] Figure 3A base coating PRIM1 is shown, comprising a high-vinyl-content polymer PBUT1, applied to the surface SURF1 of a cellulose fiber base paper PAP1. The high-vinyl-content polymer PBUT1 refers to a polymer containing a functional vinyl group (VIN1) of equal to or greater than 0.5 mmol / g. Advantageously, the base coating comprises a polymer containing a functional vinyl group of equal to or greater than 1 mmol / g, preferably equal to or greater than 2 mmol / g, most preferably equal to or greater than 4 mmol / g, for example equal to or greater than 8 mmol / g. The amount of functional vinyl groups can, for example, range from 0.5 to 18.5 mmol / g of polymer. The base coating PRIM1 comprising the high-vinyl-content polymer PBUT1 is hydrophobic because most of the functional vinyl group (VIN1) is present on the surface of the base coating PRIM1. A greater number of chains terminal to functional vinyl groups are directly related to the hydrophobicity of the surface, thereby reducing the surface energy. The functional vinyl group VIN1 present on the top surface of the base coating PRIM1 (i.e., the surface facing away from the cellulose fiber base paper PAP1) can form covalent bonds with the silicone-based release layer SIL1 that can be applied to the base coating PRIM1. The base coating PRIM1 may contain a polymer PBUT1 with a high vinyl content, such as a polymer diene.

[0059] refer to Figure 4 It shows an example of the addition polymerization of 1,3-butadiene monomer.

[0060] Polymeric dienes can be formed from diene monomers containing two or more functional vinyl groups (VIN1 -CH=CH2) via catalytic addition polymerization. By using selective catalysts, the polymeric dienes can be configured to contain a very large amount of functional vinyl groups (VIN1).

[0061] Typically, the chemical structure of a diene can be represented by the following formula:

[0062] CH2=CH-R-CH=CH2

[0063] Where R refers to an optional carbon chain, which can be a straight chain, a branched chain, or a cyclic carbon chain, and may also contain heteroatoms.

[0064] A specific example of a suitable diene monomer is 1,3-butadiene, whose chemical structure is as follows:

[0065] CH2=CH-CH=CH2

[0066] 1,3-Butadiene can be polymerized in three different ways, referred to as cis, trans, and vinyl addition, to form different forms of polybutadiene. The cis and trans forms can be obtained in a 1,4-addition reaction. When the polymerization is a 1,2-addition reaction of 1,3-butadiene, high-vinyl-content polybutadiene can be obtained from 1,3-butadiene through selective polymerization.

[0067] 1,3-Butadiene can undergo 1,2-addition polymerization in the presence of selective catalysts such as metallocene catalysts. Thus, butyllithium initiators can be used to provide 80-90% of the 1,4-addition product, as demonstrated by Samotsvetov et al. (“Butadiene polymerization in the presence of butyl lithium modified with sodium butylate”, Polymer Science USSR 23 (1981) 100-107).

[0068] However, when the reaction is carried out in the presence of 1,2-bis(piperidinyl)ethane, the selectivity for the 1,2-addition product can be as high as 100%, as demonstrated by Halasa, Lohr and Hall (“Anionic polymerization to high vinyl polybutadiene”, JPolym Sci Part A: Polym Chem 19(1981) 1357-1360).

[0069] Figure 4 The letter 'n' in this figure refers to the amount of monomer units used to form the polymer. The reference designation CAT1 refers to the catalyst used in the polymerization reaction. 'n' can be, for example, in the range of 10 to 10,000, thus providing polybutadiene with a molecular weight in the range of 110 to 540,000 g / mol.

[0070] refer to Figure 5 and Figure 6a and 6bThe oleophilic undercoat PRIM1 between the cellulose fiber base paper PAP1 and the release layer SIL1 may also contain a solubilizer between 3 mol% and 20 mol% of the polymer, such that the high vinyl content polymer PBUT1 containing functional vinyl groups is water-dispersible or water-emulsifiable when applied on top of the cellulose fiber base paper PAP1. Furthermore, the high vinyl content polymer PBUT1 may contain a solubilizer in an amount equal to or greater than 20 mol% of the polymer, so that it is water-soluble when the functional vinyl-containing polymer is applied to the cellulose fiber base paper PAP1. The solubilizer may be, for example, an unsaturated dicarboxylic acid or its anhydride or monoester, such as maleic acid or maleic anhydride, which has been grafted into the high vinyl content polymer PBUT1 containing functional vinyl groups, as shown below. Figure 5 As shown. Alternatively, unsaturated carboxylic acids or unsaturated acrylics containing functional vinyl groups can be used. The improved water solubility of the polymer composition containing the high vinyl content polymer PBUT1 promotes the uniform application of the polymer composition to the surface of cellulose fiber-based paper PAP1. The silicone layer and excess crosslinking agent compound SH1 are thus covalently and more firmly bonded to the substrate surface.

[0071] Example 1 – Preparation of polybutadiene with high vinyl content

[0072] In the experiment, 400 g (7.4 mol) of 1,3-butadiene was weighed and dissolved in 1600 g of cyclohexane under a nitrogen atmosphere to obtain a clear solution containing the 1,3-butadiene monomer. The temperature of the solution containing the 1,3-butadiene monomer was then adjusted to 30 °C, and an initiator system containing 0.17 g (2.65 mmol) of butyllithium and 5.2 g (26.5 mmol) of 1,2-bis(piperidinyl)ethane was added to provide a reaction mixture and reaction conditions selective for the 1,2-addition reaction of 1,3-butadiene. The reaction mixture was then stirred with a mechanical stirrer for 120 minutes, and 2000 g of ethanol was added to terminate the reaction and precipitate the polymer. The reaction product was purified by vacuum evaporation of the solvent and monomer residues at 50 °C. Analysis by size exclusion chromatography (SEC) showed that the purified polybutadiene had a number average molecular weight of 150,000 g / mol, and analysis by nuclear magnetic resonance (NMR) showed that it contained 99 mol% of 1,2-addition products.

[0073] Example 2 – Experimental data on polybutadiene with high vinyl content

[0074] Table 1 (shown below) shows the correlation between the vinyl percentage (i.e., the percentage of polymer repeating units containing vinyl groups) and the vinyl content (mmol / g). As can be seen from Table 1, very high vinyl contents can be obtained when 1,3-butadiene undergoes 1,2-addition polymerization in the presence of a selective catalyst. A higher amount of functional vinyl groups in polybutadiene has been observed to correlate with higher hydrophobicity on coated cellulose fiber-based paper, indicating that a higher amount of functional vinyl groups on the surface reduces surface energy. When the vinyl content is very high, for example above 60% of the amount of polymer repeating units, reaction conditions can be selected to produce polybutadiene with a lower molecular weight. Lower molecular weight polybutadiene may be advantageous in reducing the risk of premature crosslinking of polybutadiene repeating units.

[0075] Table 1. Comparison of vinyl molar concentration (mmol / g) as a function of polymer vinyl percentage among grades of polymerized butadiene (polybutadiene). In this paper, "vinyl percentage of polybutadiene" refers to the percentage of polymer repeating units containing vinyl groups. In this paper, "vinyl content" refers to the classification of polybutadiene with respect to vinyl content. Conventional (common) catalysts and reaction routes typically result in butadiene with a vinyl content of 1–2% of the polymer repeating unit amount. Polybutadiene with an increased vinyl content can be obtained on a butyllithium catalyst and a 1,2-bis(piperidinyl)ethane initiator system.

[0076]

[0077]

[0078] Comparative Example 3 – Vinyl Content Obtainable After Polyvinyl Alcohol Grafting

[0079] Comparative experiments were conducted to demonstrate the vinyl content levels achievable by grafting polyvinyl alcohol (PVA) with an organic molecule containing functional vinyl groups during the acetalization reaction. When undecenoal (an aldehyde containing 11 carbon atoms) was grafted onto PVA with a degree of hydrolysis of 98-99% and a degree of polymerization of 1400, the water solubility of the polymer was significantly reduced when undecenoal was added at a rate of 3% by weight (expressed as grams of the aldehyde compound per 100 grams of PVA). The resulting reaction product also became highly viscous, making it impossible to apply as a coating to the substrate surface using conventional coating methods. The results of the comparative experiments are listed in Table 2 (as shown below).

[0080] Table 2. Comparison of vinyl content in modified polyvinyl alcohol samples with aldehyde reactant content (10-undecenal, molecular weight 168 g / mol). "Degree of modification (wt%)" refers to the percentage of reacted aldehyde reactant per 100 g of polyvinyl alcohol. "Copyability" refers to the ability of the reaction product to coat cellulose fiber-based paper, wherein the formed polymer product is easily coatable ("1"), resulting in a sufficiently low viscosity for application by conventional coating methods, or the polymer is difficult to coat ("2"), causing the reaction product to form a viscous gel that is difficult to apply by conventional coating methods, or the polymer loses its coatability ("3") to the point that the reaction product can no longer be used as a coating.

[0081]

[0082]

[0083] NMR method for assessing the amount of functional vinyl groups

[0084] Proton nuclear magnetic resonance (NMR) 1 ¹H-NMR analysis can be used to identify chemical structures based on the chemical shift value δ of individual hydrogen atoms. 1 Samples for H-NMR analysis can be prepared by dissolving PBD in a suitable solvent (e.g., deuterated chloroform).

[0085] also, 1 The integral of the H-NMR spectrum can be used to estimate the vinyl content of the PBD sample. This can be achieved by comparing the peak areas representing the terminal vinyl protons in the 1,2-addition product (δ = 4.8 ppm) and the olefinic protons in the 1,4-addition product (δ = 5.4 ppm). The molar concentration (mmol / g) of vinyl in the product can be calculated according to Equation 1.

[0086]

[0087] Among them, b 1,2 A represents the molar concentration of vinyl groups (millomoles / g). 1,2 and A 1,4 M represents the integrated area of ​​the peaks representing the terminal vinyl proton and the 1,4-olefin proton, respectively. BD This represents the molecular weight of butadiene.

[0088] For example, when the integrated area of ​​the NMR spectrum of the 1,4-olefin protons in the tested polybutadiene sample is 36 and the integrated area of ​​the NMR spectrum of the terminal vinyl protons is 1, and the molecular weight of the tested polybutadiene sample is 54.09 g / mol, the tested polybutadiene sample has a vinyl molar concentration of 0.5 mmol / g, as shown in Equation 1 below:

[0089]

[0090] It will be apparent to those skilled in the art that modifications and variations of the products and methods according to the present invention are conceived. The accompanying drawings are illustrative. Any specific examples described above with reference to the accompanying drawings are merely exemplary and are not intended to limit the scope of the invention, which is defined by the appended claims.

Claims

1. A paper substrate (SUBST1) suitable for incorporating silicone in a catalytic hydrosilylation reaction, said paper substrate (SUBST1) comprising: - Cellulose fiber-based paper (PAP1), and - Polymer base coat (PRIM1), in, The polymer base coating (PRIM1) comprises a polymer containing functional vinyl groups in an amount equal to or greater than 0.5 mmol per gram of polymer, such that the surface of the polymer base coating (PRIM1) is hydrophobic, wherein the polymer containing functional vinyl groups is a high-vinyl-content polybutadiene, which is an isomer of polybutadiene that can be obtained from 1,3-butadiene monomers via a 1,2-addition polymerization reaction.

2. The paper substrate (SUBST1) as described in claim 1, wherein, The polymer base coat (PRIM1) comprises a polymer containing a functional vinyl group in an amount equal to or greater than 2 millimoles per gram of polymer.

3. The paper substrate (SUBST1) as described in claim 1, wherein, The cellulose fiber base paper (PAP1) has a basis weight equal to or greater than 38 g / m². 2 Coated paper.

4. The paper substrate (SUBST1) as described in claim 1, wherein, A polymer undercoat (PRIM1) is applied to the top of cellulose fiber-based paper (PAP1) at a concentration of 0.1 to 20 g / m. 2 The amount applied.

5. The paper substrate (SUBST1) as described in claim 1, wherein, The polymer undercoat (PRIM1) applied on top of the cellulose fiber base paper (PAP1) contains a polymer that comprises 1% by weight of functional vinyl groups equal to or greater than the weight of the polymer undercoat (PRIM1).

6. The paper substrate (SUBST1) as described in claim 1, wherein, The polymer undercoat (PRIM1) applied to the top of the cellulose fiber base paper (PAP1) is styrene-free.

7. A method for manufacturing a paper substrate (SUBST1) suitable for incorporating silicone in a catalytic hydrosilylation reaction, the method comprising: - Provides cellulose fiber-based paper (PAP1), and - A polymer undercoat (PRIM1) is coated on top of a cellulose fiber-based paper (PAP1) to form a paper substrate (SUBST1). The polymer base coat (PRIM1) comprises a polymer containing functional vinyl groups in an amount equal to or greater than 0.5 mmol per gram of polymer, such that the surface of the base coat (PRIM1) is hydrophobic, and the functional vinyl groups are capable of forming covalent bonds with a silicone-based release layer (SIL1) that can be applied to the top of a paper substrate (SUBST1). The polymer containing the functional vinyl groups is a high-vinyl-content polybutadiene, which is an isomer of polybutadiene that can be obtained from 1,3-butadiene monomers via 1,2-addition polymerization.

8. The method of claim 7, wherein, - This addition polymerization reaction was carried out via butyllithium catalysis in the presence of a 1,2-bis(piperidinyl)ethane initiator system.

9. The method according to any one of claims 7-8, wherein, The functional vinyl polymer also contains 3 mol% to 20 mol% of a solubilizer, such that when the functional vinyl polymer is applied on top of cellulose fiber base paper (PAP1), it is water-dispersible or water-emulsifiable.

10. The method according to any one of claims 7-8, wherein, The functional vinyl polymer also contains a solubilizer in an amount equal to or greater than 20 mol% of the polymer, such that when the functional vinyl polymer is applied on top of cellulose fiber base paper (PAP1), it is water-soluble.

11. The method of claim 9, wherein, The solubilizer is an unsaturated dicarboxylic acid or its anhydride or monoester, which has been grafted into the functionalized vinyl polymer.

12. The method according to any one of claims 7-8, wherein, The polymer base coat (PRIM1) comprises a polymer containing a functional vinyl group in an amount equal to or greater than 2 millimoles per gram of polymer.

13. The method according to any one of claims 7-8, wherein, The cellulose fiber base paper (PAP1) has a basis weight equal to or greater than 38 g / m². 2 Coated paper.

14. The method according to any one of claims 7-8, wherein, A polymer undercoat (PRIM1) is applied to the top of cellulose fiber-based paper (PAP1) at a concentration of 0.1 to 20 g / m. 2 The amount applied.

15. The method according to any one of claims 7-8, wherein, The polymer undercoat (PRIM1) applied on top of the cellulose fiber base paper (PAP1) contains a polymer that comprises 1% by weight of functional vinyl groups equal to or greater than the weight of the polymer undercoat (PRIM1).

16. The method according to any one of claims 7-8, wherein, The polymer undercoat (PRIM1) applied to the top of the cellulose fiber base paper (PAP1) is styrene-free.

17. Use of high-vinyl-content polybutadiene containing functional vinyl groups in a base coating composition suitable for bonding silicone to a paper substrate in a catalytic hydrosilylation reaction, said high-vinyl-content polybutadiene being an isomer of polybutadiene obtainable from 1,3-butadiene monomers via 1,2-addition polymerization, said high-vinyl-content polybutadiene containing functional vinyl groups in an amount equal to or greater than 0.5 mmol per gram of said high-vinyl-content polybutadiene.

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