Organic silicon pressure-sensitive adhesive composition for paper-based coating, pressure-sensitive adhesive and product thereof

Abstract

The invention relates to the technical field of organic silicon pressure-sensitive adhesives, and provides an organic silicon pressure-sensitive adhesive composition for paper-based coating and a pressure-sensitive adhesive product. The composition is prepared from 100 parts by weight of vinyl-terminated polydimethylsiloxane A, 42 to 165 parts by weight of vinyl-terminated polydimethylsiloxane B, 2.5 to 22 parts by weight of vinyl-terminated polydimethylsiloxane C, 57 to 150 parts by weight of methyl MQ resin, 4 to 11 parts by weight of a cross-linking agent, 1.5 to 4 parts by weight of an anchoring agent, 0.3 to 0.8 part by weight of an inhibitor, 3.5 to 8 parts by weight of a catalyst and 70 to 155 parts by weight of a solvent. The pressure-sensitive adhesive formed by the organic silicon pressure-sensitive adhesive composition has better cohesive strength, moderate viscosity and easiness in stripping, can adopt a conventional coating mode, is lower in drying temperature, and can be directly used for paper base coating.

Description

Technical Field

[0001] The invention relates to the technical field of organic silicon pressure-sensitive adhesives, and in particular to an organic silicon pressure-sensitive adhesive composition that can be used for paper-based coating, a pressure-sensitive adhesive and a product thereof. Background Art

[0002] In the manufacturing, shipping or use of consumer electronic products, protective films are often used to protect the surface of electronic products to prevent dirt or scratches on the product surface. This type of protective film usually adopts a paper-based double-sided AB adhesive multi-layer structure, in which the A adhesive surface is made of acrylic adhesive, with the high-viscosity surface attached to the paper base; the B adhesive surface is made of silicone, with the low-viscosity surface attached to the electronic product. Since this type of product has a built-in PET substrate layer to enhance the structural strength, the overall structure has more layers, the corresponding production process steps are more, and the material cost is higher.

[0003] In the formula of conventional silicone pressure-sensitive adhesive, since its main component is polydimethylsiloxane with high polymerization degree, more solvent needs to be added for easy coating, resulting in low solid content of glue during coating (usually <45%). It can be applied to non-paper-based coating such as polyimide (PI), polyethylene terephthalate (PET), and polypropylene (PP); but when the substrate is switched to paper-based, more solvent introduction will cause part of the solvent or even glue to penetrate into the paper-based fiber, resulting in uneven glue thickness, glue seepage and other undesirable phenomena, seriously affecting product quality and appearance; and in order to volatilize the solvent, the curing and drying temperature is generally high (>120°C), and high temperature will cause the paper base to yellow, affecting the appearance and quality of the product. Therefore, this type of silicone pressure-sensitive adhesive cannot be directly used for paper-based coating. Summary of the invention

[0004] The inventors of the present invention have found that common silicone pressure-sensitive adhesives often use high-polymerization polydimethylsiloxane to improve the wettability of the pressure-sensitive adhesive, but when pasted with steel plates or AF (Anti-fingerprint) screens, a high-speed peeling force increase phenomenon will occur. When such pressure-sensitive adhesives are used for direct coating on paper substrates, under the condition of rapid peeling (for example, 20,000 mm / min), the paper will be torn due to the large peeling force (>200 gf / in).

[0005] The purpose of the present invention is to solve the problems existing in the prior art and provide an organosilicon pressure-sensitive adhesive composition, a pressure-sensitive adhesive and a product thereof that can be used for paper base coating. The pressure-sensitive adhesive prepared by using the organosilicon pressure-sensitive adhesive composition can be used for paper base coating to obtain a paper base direct-coated organosilicon pressure-sensitive adhesive protective film product, which has good cohesive strength, moderate viscosity, is easy to peel, can be coated in a conventional manner, has a low drying temperature, and is simple in process.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The first aspect of the present invention provides a silicone pressure-sensitive adhesive composition that can be used for paper-based coating, the composition comprising the following components:

[0008]

[0009] Wherein, the viscosity of the vinyl-terminated polydimethylsiloxane A is 300 to 1,000 mPa·s;

[0010] The viscosity of the vinyl-terminated polydimethylsiloxane B is 30,000 to 60,000 mPa·s;

[0011] The viscosity of the vinyl-terminated polydimethylsiloxane C is 800 to 1,200 mPa·s.

[0012] In the organosilicon pressure-sensitive adhesive composition of the present invention, by adopting low-viscosity vinyl-terminated polydimethylsiloxane A as the main body, the solvent usage can be reduced by using low-viscosity vinyl-terminated polydimethylsiloxane A as the main body, so as to avoid more solvents from penetrating into the paper-based fiber, resulting in uneven glue thickness and glue penetration problems, and reduce the viscosity of the pressure-sensitive adhesive composition, which is convenient for uniform coating. By adding a certain amount of high-viscosity vinyl-terminated polydimethylsiloxane B, the cohesion of the pressure-sensitive adhesive can be made stronger. By adding a certain amount of low-viscosity vinyl-terminated polydimethylsiloxane C, the viscosity and cohesion strength of the pressure-sensitive adhesive can be well adjusted to meet the actual application requirements.

[0013] Therefore, the present invention uses relatively low viscosity vinyl-terminated polydimethylsiloxane A as the main component, and combines a certain amount of high viscosity vinyl-terminated polydimethylsiloxane B and low viscosity vinyl-terminated polydimethylsiloxane C, so that the overall viscosity of the pressure-sensitive adhesive can be relatively low, thereby achieving direct coating of the high-solid content pressure-sensitive adhesive on the surface of the paper base.

[0014] It should be noted that:

[0015] In the present invention, the viscosity of the vinyl-terminated polydimethylsiloxane A, the vinyl-terminated polydimethylsiloxane B and the vinyl-terminated polydimethylsiloxane C are all viscosities at 25°C;

[0016] In the present invention, in the general formula of the polymer structure involved, Vi represents a vinyl group, and Me represents a methyl group;

[0017] In the present invention, in the general formula of the polymer structure involved, the subscripts: a, (b+c), (d+e), f, and g represent average values, that is, the average value of the number of repeating units contained in the polymer macromolecular chain, which can also be expressed as the degree of polymerization of the polymer.

[0018] In some embodiments, the vinyl-terminated polydimethylsiloxane A has the following general structural formula: (ViMe2SiO)-(SiMe2O) a -(SiMe2Vi), the average value of a is 140-380, for example, it can be 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380 or any value in the range formed by the above two points.

[0019] In some embodiments, the vinyl mass fraction in the vinyl-terminated polydimethylsiloxane A is 0.18-0.45%, for example, it can be 0.18%, 0.22%, 0.26%, 0.30%, 0.34%, 0.38%, 0.42%, 0.45% or any value in the range of the above two values.

[0020] In some embodiments, the viscosity of the vinyl-terminated polydimethylsiloxane A is 300 to 1,000 mPa·s, for example, 300 mPa·s, 400 mPa·s, 500 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, 900 mPa·s, 1,000 mPa·s or any value in the range consisting of the above two values.

[0021] In some embodiments, the content of the vinyl-terminated polydimethylsiloxane B is 42 to 165 parts by weight, for example, 42 parts by weight, 55 parts by weight, 70 parts by weight, 95 parts by weight, 120 parts by weight, 130 parts by weight, 165 parts by weight or any value in the range consisting of the above two values, preferably 55 to 120 parts by weight, and more preferably 70 to 95 parts by weight.

[0022] In some embodiments, the ratio of the weight of the vinyl-terminated polydimethylsiloxane B to the weight of the vinyl-terminated polydimethylsiloxane A, the vinyl-terminated polydimethylsiloxane B and the vinyl-terminated polydimethylsiloxane C is 0.3 to 0.6; specifically, it can be 0.3, 0.4, 0.5, 0.6 or any value between the two end values. The ratio of the weight of the vinyl-terminated polydimethylsiloxane B to the weight of the vinyl-terminated polydimethylsiloxane A, the vinyl-terminated polydimethylsiloxane B and the vinyl-terminated polydimethylsiloxane C is limited to the above range in order to ensure that the overall cohesive strength and viscosity of the pressure-sensitive adhesive composition meet the actual use requirements of the final pressure-sensitive adhesive product. When the ratio is too low, it means that the amount of high-viscosity vinyl-terminated polydimethylsiloxane B added is small, and the cohesive strength of the pressure-sensitive adhesive obtained by configuring too much low-viscosity vinyl-terminated polydimethylsiloxane is poor, and the surface of the colloid is easily damaged; when the ratio is too high, it means that the amount of high-viscosity vinyl-terminated polydimethylsiloxane B added is large, and the overall viscosity of the obtained pressure-sensitive adhesive is too large, which is not conducive to coating. During coating, more solvent needs to be added to reduce the viscosity of the pressure-sensitive adhesive to a viscosity range that is convenient for coating operations. Generally, the glue coating viscosity needs to be controlled below 3,500 mPa·s. However, adding more solvent is not conducive to direct coating on the paper base, and it is easy to have undesirable phenomena such as uneven glue thickness and glue penetration, which seriously affects the product quality and appearance.

[0023] In some embodiments, the vinyl-terminated polydimethylsiloxane B has the following general structural formula: (ViMe2SiO)-(SiMe2O) b -(SiMeViO) c -(SiMe2Vi), the average value of b+c is 1,000 to 1,480, for example, it can be 1,000, 1,050, 1,100, 1,150, 1,200, 1,250, 1,300, 1,350, 1,400, 1,450, 1,480 or any value in the range of the above two values. The degree of polymerization of the vinyl-terminated polydimethylsiloxane B (i.e., the average value of b+c) is controlled to be 1,000 to 1,480, which is relatively low, will not cause the overall viscosity of the pressure-sensitive adhesive to be too high, and also reduces the use of solvents, can increase the solid content of the pressure-sensitive adhesive, and is conducive to the direct coating of the pressure-sensitive adhesive on the paper base.

[0024] In some embodiments, the vinyl mass fraction in the vinyl-terminated polydimethylsiloxane B is 0.2-0.4%, for example, 0.2%, 0.25%, 0.3%, 0.35%, 0.4% or any value in the range of the above two values.

[0025] In some embodiments, the viscosity of the vinyl polydimethylsiloxane B is 30,000 to 60,000 mPa·s, for example, 30,000 mPa·s, 35,000 mPa·s, 40,000 mPa·s, 45,000 mPa·s, 50,000 mPa·s, 55,000 mPa·s, 60,000 mPa·s or any value in the range consisting of the above two values.

[0026] In some embodiments, the content of the vinyl-terminated polydimethylsiloxane C is 2.5 to 22 parts by weight, for example, 2.5 parts by weight, 9 parts by weight, 10 parts by weight, 12.5 parts by weight, 14 parts by weight, 18 parts by weight, 22 parts by weight or any value in the range consisting of the above two parts, preferably 9 to 14 parts by weight, and more preferably 10 to 12.5 parts by weight.

[0027] In some embodiments, the ratio of the weight of the vinyl-terminated polydimethylsiloxane C to the weight of the vinyl-terminated polydimethylsiloxane A, the vinyl-terminated polydimethylsiloxane B and the vinyl-terminated polydimethylsiloxane C is 0.02 to 0.08; specifically, it can be 0.02, 0.04, 0.06, 0.08 or any value between the two values. The ratio is limited here to adjust the wettability of the pressure-sensitive adhesive composition as a whole within a suitable range. When the ratio is too low, it means that the amount of vinyl-terminated polydimethylsiloxane C added is small, and the wettability of the obtained pressure-sensitive adhesive product (such as a pressure-sensitive adhesive protective film) is still relatively good, but the relative peeling force is high during high-speed peeling, which may lead to the risk of paper breaking or even direct tearing of the paper base; when the ratio is too high, it means that the amount of vinyl-terminated polydimethylsiloxane C added is high, and the cross-linking density of the obtained pressure-sensitive adhesive product is too large, and the wettability is reduced, making it difficult to adhere to the surface of the adhered object. At the same time, the pressure-sensitive adhesive colloid is too hard and brittle, which may cause the colloid surface to be easily damaged by external stress, resulting in abnormal phenomena such as glue falling off and powder falling off.

[0028] In some embodiments, the general structural formula of the vinyl-terminated polydimethylsiloxane C is as follows:

[0029] (ViMe2SiO)-(SiMe2O) d -(SiMeViO) e -(SiMe2Vi), the average value of d+e is 235-350, for example, it can be 235, 250, 280, 300, 320, 340, 350 or any value in the range consisting of the above two values.

[0030] In some embodiments, the vinyl mass fraction in the vinyl-terminated polydimethylsiloxane C is 2-3%, for example, it can be 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any value in the range of the above two values. The vinyl-terminated polydimethylsiloxane C contains more vinyl groups, which can greatly increase the overall cross-linking density of the pressure-sensitive adhesive and reduce the wettability of the pressure-sensitive adhesive protective film product.

[0031] In some embodiments, the viscosity of the vinyl-terminated polydimethylsiloxane C is 800 to 1,200 mPa·s, for example, 800 mPa·s, 850 mPa·s, 900 mPa·s, 950 mPa·s, 1,000 mPa·s, 1,050 mPa·s, 1,100 mPa·s, 1,150 mPa·s, 1,200 mPa·s or any value in the range consisting of the above two values.

[0032] The present invention adds vinyl-terminated polydimethylsiloxane C to the pressure-sensitive adhesive, and the vinyl-terminated polydimethylsiloxane C has a high vinyl content (the vinyl mass fraction is 2-3%), which can significantly increase the crosslinking point of the reaction and improve the hardness of the pressure-sensitive adhesive. The vinyl-terminated polydimethylsiloxane C is combined with the low-viscosity vinyl-terminated polydimethylsiloxane A and the high-viscosity vinyl-terminated polydimethylsiloxane B to effectively control the wettability of the pressure-sensitive adhesive, thereby avoiding the phenomenon of peeling force climbing and paper breaking under high-speed peeling.

[0033] In some embodiments, the content of the methyl MQ resin is 57 to 150 parts by weight, for example, it can be 57 parts by weight, 85 parts by weight, 90 parts by weight, 100 parts by weight, 115 parts by weight, 130 parts by weight, 150 parts by weight or any value in the range consisting of the above two points, preferably 90 to 130 parts by weight, and more preferably 100 to 115 parts by weight.

[0034] In some embodiments, the weight ratio of the methyl MQ resin to the vinyl-terminated polydimethylsiloxane A, the vinyl-terminated polydimethylsiloxane B and the vinyl-terminated polydimethylsiloxane C is 0.4 to 0.8, and can be specifically 0.4, 0.5, 0.6, 0.7, 0.8 or any value between the two end values. The ratio is limited to the above range here because the methyl MQ resin mainly plays a tackifying role. The amount of methyl MQ resin added determines the overall peeling force of the pressure-sensitive adhesive formula. When other components remain unchanged, if the amount of methyl MQ resin added is too low, the peeling force of the resulting pressure-sensitive adhesive product is low, and it cannot be firmly attached to the surface of the adhered object (such as AF screen, etc.). Weak adhesion will cause the pressure-sensitive adhesive product to fall off, bulge and other abnormal phenomena during use; if the amount of methyl MO resin added is too high, the peeling force of the resulting pressure-sensitive adhesive product is high, which causes the risk of paper breaking or even direct breaking of the paper base during high-speed peeling.

[0035] In some embodiments, the methyl MQ resin has the following general structural formula:

[0036] (Me3SiO 1 / 2 ) f -(SiO 4 / 2 ) g , the value range of f and g meets the following requirements: f>4, g>0, 0.6<(f / g)<1.0, and the value of (f / g) can be, for example, 0.7, 0.8, 0.9 or any value in the range formed by the above two points.

[0037] In some embodiments, the weight average molecular weight of the methyl MQ resin is 4,000 to 8,000, for example, 4,000, 5,000, 6,000, 7,000, 8,000 or any value in the range consisting of the above two values.

[0038] In the present invention, the methyl MQ resin is added to the pressure-sensitive adhesive composition. On the one hand, the molecular weight of the methyl MQ resin is small, and its addition does not cause a significant change in the viscosity of the glue. On the other hand, the peeling force of the pressure-sensitive adhesive can be adjusted by adjusting the amount of the methyl MQ resin added.

[0039] In some embodiments, the content of the cross-linking agent is 4 to 11 parts by weight, for example, 4 parts by weight, 6 parts by weight, 6.5 parts by weight, 8 parts by weight, 9 parts by weight, 11 parts by weight, or any value in the range of the above two values, preferably 6 to 9 parts by weight, and more preferably 6.5 to 8 parts by weight. The type of the cross-linking agent is not specifically limited, and the conventional cross-linking agent types in the art are all within the protection scope of the present invention.

[0040] In some embodiments, the cross-linking agent includes hydrogen-containing silicone oil.

[0041] In some embodiments, the viscosity of the hydrogen-containing silicone oil is 15 to 100 mPa·s, for example, 15 mPa·s, 20 mPa·s, 40 mPa·s, 60 mPa·s, 80 mPa·s, 100 mPa·s or any value in the range of the above two values.

[0042] In some embodiments, the mass fraction of active hydrogen groups in the hydrogen-containing silicone oil is 1.4-1.6%, for example, 1.4%, 1.5%, 1.6% or any value in the range of the above two values.

[0043] In the present invention, hydrogen-containing silicone oil with a high content of active hydrogen groups is selected as a crosslinking agent, wherein the Si-H bonds can undergo a hydrosilylation reaction with the vinyl functional groups in the vinyl-terminated polydimethylsiloxane to form a three-dimensional network structure, thereby enhancing the mechanical properties and thermal stability of the colloid.

[0044] In some embodiments, the content of the anchoring agent is 1.5 to 4 parts by weight, for example, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 4 parts by weight, or any value in the range of the above two values, preferably 2 to 3 parts by weight. The type of anchoring agent is not specifically limited, and conventional anchoring agents in the art are within the scope of protection of the present invention.

[0045] In some embodiments, the anchoring agent includes a silane coupling agent; preferably, the silane coupling agent includes at least one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), γ-(2,3-epoxypropoxy)propyltriethoxysilane (WD-62), vinyltrimethoxysilane (A171), vinyltriethoxysilane (A151) and vinyltriacetoxysilane.

[0046] Silane coupling agents contain organic-inorganic hybrid bifunctional compounds, which react chemically with both the substrate and the pressure-sensitive adhesive. The organic functional groups are vinyl or epoxy groups, which can chemically bond with the organic functional groups in the pressure-sensitive adhesive to improve the cohesion of the pressure-sensitive adhesive. The organic functional groups also contain methoxy, ethoxy, acetoxy groups, which are easily hydrolyzed into silanols. After hydrolysis, these groups can react with oxides or hydroxyls on the surface of the paper base to form silicon-oxygen bonds. This dual chemical bonding allows the silane coupling agent (anchoring agent) to tightly bond the silicone pressure-sensitive adhesive to the substrate, thereby improving the bonding strength of the pressure-sensitive adhesive.

[0047] In some embodiments, the content of the catalyst is 3.5 to 8 parts by weight, for example, 3.5 parts by weight, 4.5 parts by weight, 5 parts by weight, 6 parts by weight, 6.5 parts by weight, 8 parts by weight, or any value in the range of the above two values, preferably 4.5 to 6.5 parts by weight, and more preferably 5 to 6 parts by weight. The type of catalyst is not specifically limited, and conventional catalyst types in the art are within the scope of protection of the present invention.

[0048] In some embodiments, the catalyst includes a platinum catalyst, preferably a platinum-olefin siloxane coordination compound. The platinum content in the platinum catalyst is 2,000 to 10,000 ppm, for example, 2,000 ppm, 4,000 ppm, 6,000 ppm, 8,000 ppm, 10,000 ppm or any value between the two end values; if the platinum content is lower than the above-defined range, the catalytic activity of the catalyst is insufficient; if it exceeds the above range, on the one hand, the platinum price is high, which will increase the cost of raw materials, and on the other hand, too high a platinum content will cause the pressure-sensitive adhesive to undergo a cross-linking reaction in advance, and the prepared pressure-sensitive adhesive will undergo a cross-linking reaction before entering the coating oven, and will be cured in advance, resulting in the inability to complete the preparation of subsequent pressure-sensitive adhesive products.

[0049] In some embodiments, the content of the inhibitor is 0.3 to 0.8 parts by weight, for example, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight or any value in the range of the above two values, preferably 0.4 to 0.6 parts by weight, and more preferably 0.5 to 0.6 parts by weight. The types of inhibitors are not specifically limited, and conventional inhibitors in the art are within the scope of protection of the present invention.

[0050] In some embodiments, the inhibitor includes at least one of maleic anhydride, 2-butyn-1-ol, 2-methyl-3-butyn-2-ol, 1-alkynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, tetramethyltetravinylcyclotetrasiloxane, tetramethyldivinyldisiloxane and phenylacetylene.

[0051] Since the pressure-sensitive adhesive composition will react immediately after adding a catalyst (such as a platinum catalyst), the pressure-sensitive adhesive will solidify before coating. The inhibitor can temporarily inhibit the catalytic activity of the catalyst. When the pressure-sensitive adhesive needs to be used, the inhibitor can be inactivated by heating, thereby releasing the catalytic activity of the catalyst and solidifying the pressure-sensitive adhesive, which makes it easier for the pressure-sensitive adhesive to remain stable during storage or transportation and prolong the storage period.

[0052] In some embodiments, the content of the solvent is 70 to 155 parts by weight, for example, 70 parts by weight, 80 parts by weight, 90 parts by weight, 100 parts by weight, 115 parts by weight, 120 parts by weight, 130 parts by weight, 140 parts by weight, 150 parts by weight, 155 parts by weight or any value in the range of the above two points, preferably 80 to 130 parts by weight, more preferably 90 to 115 parts by weight. The present invention does not specifically limit the type of solvent, and conventional solvents in the field are all within the scope of protection of the present invention.

[0053] In some embodiments, the boiling point of the solvent is not higher than 110°C; preferably, the solvent includes at least one of ethyl acetate, butanone, hexane, and n-heptane, preferably a combination of ethyl acetate and n-heptane, and further preferably a mass ratio of ethyl acetate to n-heptane of 1 to 1.1, specifically 1, 1.03, 1.04, 1.05, 1.06, 1.1 or any value between the two end values. The boiling point of ethyl acetate is 76.5 to 77.5°C, and the boiling point of n-heptane is 98°C. In the present invention, a combination of two solvents with different boiling points is used, so that the ethyl acetate with a low boiling point can be volatilized first, and then the n-heptane with a higher boiling point can be volatilized, and the solvent can be volatilized quickly in a shorter drying time, so as to avoid the solvent remaining on the paper base for too long, causing the glue to penetrate into the paper base, and causing undesirable phenomena such as uneven glue thickness and glue seepage.

[0054] In order to avoid incomplete volatilization of the solvent after curing, which leads to a decrease in the bonding strength of the glue, the curing temperature of the glue needs to be greater than or equal to the boiling point of the solvent. When conventional silicone pressure-sensitive adhesive formulas are coated, the curing temperature is usually greater than 120°C due to the high solvent content and the possibility of containing high-boiling-point solvents. However, higher temperatures can easily cause the paper base to turn yellow in the oven, affecting the appearance of the finished product. In the present invention, since the pressure-sensitive adhesive has a small amount of solvent and a high solid content, the drying time and drying temperature can be reduced. The pressure-sensitive adhesive described in the present invention selects a low-boiling-point solvent, which can achieve low-temperature curing and avoid yellowing of the paper base due to high-temperature curing.

[0055] The second aspect of the present invention provides a pressure-sensitive adhesive, which includes the organic silicone pressure-sensitive adhesive composition described in the first aspect of the present invention.

[0056] The present invention also provides a method for preparing the pressure-sensitive adhesive, comprising the following steps:

[0057] (1) adding measured weight portions of vinyl-terminated polydimethylsiloxane A, vinyl-terminated polydimethylsiloxane B, and vinyl-terminated polydimethylsiloxane C to a reaction kettle, adding methyl MQ resin and a first solvent under stirring, heating the mixture to 75 to 85° C., stirring for 1.5 to 2.5 hours in a closed environment, then stopping heating and cooling naturally to room temperature;

[0058] (2) Then, add measured weight portions of a crosslinking agent, an anchoring agent, an inhibitor, a catalyst and a second solvent in sequence under stirring and mix them evenly to obtain the silicone pressure-sensitive adhesive to be coated.

[0059] The present invention also provides another method for preparing the pressure-sensitive adhesive, comprising the following steps:

[0060] (1) Adding measured weight portions of vinyl-terminated polydimethylsiloxane A to a reaction kettle, adding methyl MQ resin and a first solvent under stirring, heating the mixture to 75 to 85° C., stirring for 1.5 to 2.5 hours in a closed environment, then stopping heating and cooling naturally to room temperature;

[0061] (2) Then, vinyl-terminated polydimethylsiloxane B, vinyl-terminated polydimethylsiloxane C, a crosslinking agent, an anchoring agent, an inhibitor, a catalyst and a second solvent are added in measured weight parts in a stirring state, and mixed evenly to obtain a silicone pressure-sensitive adhesive to be coated.

[0062] In the above two methods, the total weight of the first solvent and the second solvent is the total weight of the solvent, and the mass ratio of the first solvent to the second solvent is 1 to 1.1, wherein the boiling point of the first solvent is lower than the boiling point of the second solvent.

[0063] The viscosity of the pressure-sensitive adhesive of the present invention at room temperature (25° C.) is 80 to 2,500 mPa·s, specifically 80 mPa·s, 200 mPa·s, 500 mPa·s, 750 mPa·s, 1,000 mPa·s, 1,500 mPa·s, 2,500 mPa·s or any value in between.

[0064] The pressure-sensitive adhesive of the present invention has a solid content of 75-90%, specifically 75%, 80%, 90% or any value between the two end values. The pressure-sensitive adhesive of the present invention has a high solid content and a small amount of solvent added, which facilitates the rapid volatilization of the solvent and avoids the solvent from being infiltrated into the paper base due to a long retention time, resulting in uneven adhesive thickness, adhesive seepage and other undesirable phenomena.

[0065] The third aspect of the present invention provides a pressure-sensitive adhesive product, which includes a substrate layer and an adhesive layer arranged on at least one side of the substrate layer, the adhesive layer includes the pressure-sensitive adhesive described in the second aspect of the present invention or contains the silicone pressure-sensitive adhesive composition described in the first aspect of the present invention, and the substrate layer is paper-based.

[0066] In the present invention, the pressure-sensitive adhesive product is obtained by directly coating the pressure-sensitive adhesive on a paper base.

[0067] In the present invention, the type of the pressure-sensitive adhesive product is not specifically limited, and any pressure-sensitive adhesive product in the art is within the protection scope of the present invention. Exemplarily, the pressure-sensitive adhesive product includes at least one of a tape, a label paper, a film, and a protective film.

[0068] In the present invention, the paper base includes at least one of coated paper, tissue paper, glassine paper and Minfeng paper.

[0069] In the present invention, the thickness of the adhesive layer is generally not particularly limited and can be adjusted according to actual needs, for example, it can be 5 to 30 μm, specifically 5 μm, 10 μm, 15 μm, 25 μm, 30 μm or any value between the two ends.

[0070] In the present invention, the thickness of the paper base is generally not particularly limited and can be adjusted according to actual needs. For example, it can be 40 to 150 μm, specifically 40 μm, 60 μm, 80 μm, 100 μm, 150 μm or any value between the two ends.

[0071] The pressure-sensitive adhesive product of the present invention can be provided as a single-sided or double-sided adhesive sheet. If it is coated only on one side of the substrate layer, it is a single-sided adhesive sheet; if it is coated on both sides of the substrate layer, it is a double-sided adhesive sheet. A release film can be covered on the surface of the adhesive sheet layer, and the release film can be peeled off during actual use. The release film can be made of conventional materials, such as PET release film, PE release film, OPP release film, single silicon release film, composite release film, etc. There is no particular limitation on the thickness of the release film, and generally different thicknesses can be used according to actual winding or cost requirements.

[0072] The present invention adopts the above technical solution to achieve the following beneficial effects:

[0073] (1) The organic silicone pressure-sensitive adhesive provided by the present invention has a high solid content and a low overall viscosity of the adhesive, and can be directly used for coating of paper substrates;

[0074] (2) The organic silicone pressure-sensitive adhesive provided by the present invention can achieve low-temperature curing, thus avoiding yellowing of the paper base caused by high curing temperature;

[0075] (3) The organic silicone pressure-sensitive adhesive provided by the present invention is added with a high vinyl content terminal vinyl polydimethylsiloxane C component, and has low high-speed peeling force and will not cause paper tearing. DETAILED DESCRIPTION

[0076] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0077] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention relates.

[0078] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0079] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources. 1 g in the following examples means 1 part by weight.

[0080] The present invention is described in detail below in conjunction with specific embodiments, which are used to understand but not to limit the present invention.

[0081] The following Table 1 lists the sources and related properties of the raw materials used in the examples of the present invention. The vinyl-terminated polydimethylsiloxane A, vinyl-terminated polydimethylsiloxane B, vinyl-terminated polydimethylsiloxane C and hydrogen-containing silicone oil used in the examples of the present invention were purchased from Ningbo Runhe High-tech Materials Co., Ltd.

[0082] Table 1 Raw material sources

[0083]

[0084]

[0085] Among them, A2 / A4 / B1-B5 / C1 / C3 / C4 are specially supplied products by suppliers according to the required viscosity and vinyl content of vinyl silicone oil.

[0086] Examples 1-6

[0087] Preparation method of silicone pressure-sensitive adhesive:

[0088] The amount of each component is shown in Table 2. Vinyl-terminated polydimethylsiloxane A, vinyl-terminated polydimethylsiloxane B and vinyl-terminated polydimethylsiloxane C are added in parts by weight to the reaction kettle in sequence, and heated while stirring until the mixture is heated to 80°C; during the stirring process, methyl MQ resin is added in 4 equal portions, and then the solvent heptane is added and stirred in a closed manner for 2 hours. After mixing evenly, the heating is stopped. After the glue is cooled to below 30°C, a crosslinking agent (hydrogen-containing silicone oil), an anchoring agent (KH-560), an inhibitor (1-ethynylcyclohexanol), a platinum catalyst and a solvent ethyl acetate (EA) are added in sequence, and stirred evenly to obtain a silicone pressure-sensitive adhesive with a solid content of 75%.

[0089] Table 2

[0090]

[0091]

[0092] Note: m A represents the weight of vinyl-terminated polydimethylsiloxane A;

[0093] m B represents the weight of vinyl-terminated polydimethylsiloxane B;

[0094] m C represents the weight of vinyl-terminated polydimethylsiloxane C;

[0095] m A +m B +m C represents the sum of the masses of three vinyl-terminated polydimethylsiloxanes;

[0096] m Q Represents the weight of methyl MQ resin.

[0097] Example 7 Group

[0098] The preparation method of this group of examples is carried out in accordance with the above, the main difference being that the type of vinyl-terminated polydimethylsiloxane A in the silicone pressure-sensitive adhesive is different, and its amount and other components and composition are the same as those in Example 1, and the specific differences are as shown:

[0099] Example 7a: Vinyl-terminated polydimethylsiloxane A uses an equal amount of A1;

[0100] Example 7b: Vinyl-terminated polydimethylsiloxane A uses an equal amount of A3;

[0101] Example 7c: Vinyl-terminated polydimethylsiloxane A uses an equal amount of A4;

[0102] Example 7d: Vinyl-terminated polydimethylsiloxane A uses an equal amount of A5.

[0103] Example 8 Group

[0104] The preparation method of this group of examples is carried out with reference to the above, the main difference being that the type of the vinyl-terminated polydimethylsiloxane B in the silicone pressure-sensitive adhesive is different, and its amount and other components and composition are the same as those in Example 1, and the specific differences are as shown below:

[0105] Example 8a: Vinyl-terminated polydimethylsiloxane B uses an equal amount of B1;

[0106] Example 8b: Vinyl-terminated polydimethylsiloxane B uses an equal amount of B3;

[0107] Example 8c: Vinyl-terminated polydimethylsiloxane B uses an equal amount of B4;

[0108] Example 8d: Vinyl-terminated polydimethylsiloxane B uses an equal amount of B5.

[0109] Example 9 Group

[0110] The preparation method of this group of examples is carried out in accordance with the above, the main difference being that the type of the vinyl-terminated polydimethylsiloxane C in the silicone pressure-sensitive adhesive is different, and its amount and other components and composition are the same as those in Example 1, and the specific differences are as shown:

[0111] Example 9a: Vinyl-terminated polydimethylsiloxane C uses an equal amount of C1;

[0112] Example 9b: Vinyl-terminated polydimethylsiloxane C uses an equal amount of C3;

[0113] Example 9c: Vinyl-terminated polydimethylsiloxane C uses an equal amount of C4;

[0114] Example 9d: Vinyl-terminated polydimethylsiloxane C uses an equal amount of C5.

[0115] Comparative Example 1-3 Group

[0116] Comparative Examples 1-3 were prepared with reference to Example 1, with the main difference being that the components of the silicone pressure-sensitive adhesive were changed. The specific differences are shown in Table 3.

[0117] Table 3

[0118]

[0119] Comparative Example 4

[0120] This comparative example is carried out with reference to Example 1, except that a commercially available silica gel component is used to prepare a conventional pressure-sensitive adhesive, the main component of which is 100 g of DOWSIL TM 7647 (viscosity 7500mPa˙s) and 100g of DOWSIL TM 7657 (viscosity 22500mPa˙s), and the platinum catalyst uses SYL-OFF from Dow Chemical Company TM 4000 5.7 g, and mix them evenly to obtain a conventional pressure-sensitive adhesive.

[0121] Performance Testing

[0122] The silicone pressure-sensitive adhesive prepared in the above embodiments and comparative examples was directly coated on 115g of coated paper and cured in an oven at 110°C for 90s to obtain an adhesive layer with a theoretical thickness of 13μm, thereby obtaining a silicone pressure-sensitive adhesive protective film. The silicone pressure-sensitive adhesive protective film was subjected to the following performance tests, and the test results are recorded in Table 4.

[0123] The theoretical thickness of the adhesive layer is calculated as follows: cut three pieces of 10cm×10cm coated paper, test the weight at room temperature (25℃), and calculate the average value as m1(g); then cut three pieces of 10cm×10cm coated coated paper, test the weight at room temperature (25℃), and calculate the average value as m2(g); the density of silicone pressure-sensitive adhesive is 1g / cm 3 , the ratio of the weight difference to the area is the theoretical thickness h (μm) of the adhesive layer, that is:

[0124] h=[(m2-m1) / 100×10 4 ](μm)=[(m2-m1)×100](μm).

[0125] Test items

[0126] 1. Adhesive layer thickness measurement: Test according to the national standard GB / T 7125-2014 "Test method for thickness of adhesive tape".

[0127] 2. AF screen 90° peel force test: The adhesive layer of the protective film is attached to the surface of the AF screen with a water drop angle greater than 115°. The test is performed using a Kejian 90° tensile testing machine in accordance with the international standard ASTM D3330 "Standard Test Method for Peel Adhesion Strength of Pressure-Sensitive Tapes". The test simulates the application scenario when the protective film is peeled off, and the peel force is recorded at peel speeds of 300 mm / min (minimum peel speed) and 20,000 mm / min (maximum peel speed).

[0128] 3. The criterion for judging whether the paper is torn is as follows: after the above 90° peeling force test, observe whether there are coated paper scraps remaining on the surface of the AF screen. If there are no coated paper scraps, record it as "No"; if there are, record it as "Yes"; if the paper base is pulled apart, record it as "Pulled apart".

[0129] 4. Simulate the adhesion after transportation: Use a simulated transportation vibration table (manufacturer: Guangdong Kejian Instrument Co., Ltd., model: KJ-8030) for simulation, set the time to 24 hours and the speed to 110km / h. When peeling at a low speed (300mm / min), if the peeling force of the protective film relative to the AF screen is less than 3.5gf / in, it can be inferred that there may be poor adhesion, film falling, arching and other undesirable phenomena during transportation, which are recorded as NG; on the contrary, if the peeling force is greater than or equal to 3.5gf / in, it is recorded as OK.

[0130] Adhesion surface cohesion test: Place the test piece on a flat plate with sufficient hardness, hold the handle of the gridding tool, make the multi-blade cutter perpendicular to the surface of the test piece, cut with uniform pressure, steady and motionless technique and 20-50mm / s cutting speed, then rotate the test piece 90°g and repeat the above operation on the cut to form a grid pattern. Use the 4D MY2G special test tape, stick the tape on the entire grid, roll it back and forth with a 2kg roller for 2 times, and leave it for 1 minute after rolling. Result judgment: "Excellent" means: the edge of the incision is completely smooth, and there is no peeling on the edge of the grid; "Good" means: there is small peeling at the intersection of the incision, and the actual damage in the grid area does not exceed 10%; "Medium" means: there is peeling on the edge and intersection of the incision, and the area is greater than 10% but less than 30%; "Poor" means: there is partial peeling or large peeling on the edge of the incision, or part of the grid is peeled off as a whole, and the peeling area exceeds 30%.

[0131] Viscosity determination: According to the national standard GB / T 2794-2022 "Determination of viscosity of adhesives", the viscosity of the pressure-sensitive adhesive (25°C) was measured using the rotational viscosity method (Brookfield viscometer, LV-2 rotor).

[0132] Coating effect determination: According to industry experience and the coating practice of the inventor of the present invention, the coating effect is better when the viscosity of the micro-concave coating glue is 25-350mPa·s, among which the film surface is flat when it is 50-250mPa·s, and the effect is recorded as excellent. In other intervals, the film surface has a little unevenness, and the effect is recorded as good; the coating effect is better when the viscosity of the scraper coating glue is 200-3,500mPa·s, among which the film surface is flat when it is 250-2,500mPa·s, and the effect is recorded as excellent. In other intervals, the film surface has a little unevenness, and the effect is recorded as good. If the viscosity exceeds the above range, the glue will not level well and cannot be evenly coated on the surface of the substrate, and the effect is poor.

[0133] Paper base yellowing test: A spectrophotometer (Konica Minolta CM-2500d) was used to test the b value of the coated paper used in the embodiment of the present invention after drying at different temperatures for 90 seconds, and the change in the b value Δb (the b value after baking minus the b value of the base paper) was calculated, where Δb represents the yellowing degree of the coated paper. The larger the Δb value, the more serious the yellowing. The recorded results are shown in Table 5.

[0134] Table 4 Performance test results

[0135]

[0136] Table 5 Paper base yellowing test results

[0137]

[0138] From the test results in Table 5, it can be seen that when the coated paper is placed in an environment of 120°C or less, the b value change Δb (b value after baking minus b value of base paper) <0.2, which can be basically regarded as a small color change; when the temperature reaches 130°C or above, Δb>0.2, the b value increases more, and the paper base turns yellow significantly. The pressure-sensitive adhesive of the present invention uses a solvent with a boiling point lower than 110°C, and the curing temperature is relatively low; and the pressure-sensitive adhesive has a high solid content, a small amount of solvent added, and a short curing time, which can effectively avoid the yellowing of the paper base caused by high curing temperature and long curing time.

[0139] From the test results of Examples 1-6 and Comparative Example 4 in Table 4, it can be seen that the pressure-sensitive adhesive prepared by the pressure-sensitive adhesive composition provided by the present invention can achieve high-solid content direct coating of the paper base without the need for transfer coating; the glue has good leveling properties and can be evenly coated, and no undesirable phenomena such as weak adhesion, falling off, and arching will occur during the simulated transportation process. By reasonably regulating the relative content of each component, a pressure-sensitive adhesive that meets the requirements of micro-dimpled coating or blade coating and whose adhesive properties and cohesive properties meet the requirements of use can be obtained, and after being coated with the paper base and attached to the AF screen, it can meet high-speed and low-speed peeling without paper breaking.

[0140] It can be seen from the test results of Example 7 that if the viscosity of the vinyl-terminated polydimethylsiloxane A is not within the specified range, the film cohesion will be unqualified, the simulated transportation adhesion will be NG, or there will be poor paper tearing.

[0141] It can be seen from the test results of Example 8 that if the viscosity of the vinyl-terminated polydimethylsiloxane B is not within the specified range, the film cohesion may be unqualified or the coating may be uneven.

[0142] The test results of Example 9 show that if the viscosity of the vinyl-terminated polydimethylsiloxane C is not within the specified range, a large high-speed peeling force may result in paper breakage or NG in the simulated transport adhesion.

[0143] The test results of comparative example 1 show that if the vinyl-terminated polydimethylsiloxane B is not present or its content is low, the cohesion of the adhesive surface is poor; if its content is high, the viscosity of the pressure-sensitive adhesive will be high, which is not conducive to coating.

[0144] The test results of comparative example 2 show that if terminal vinyl polydimethylsiloxane C is not present or its content is low, there will be serious or slight paper breakage; if its content is high, it will lead to poor cohesion and the simulated transport adhesion will be NG.

[0145] The test results of comparative example 3 show that when the content of methyl MQ resin is too low, the simulated transport adhesion condition will be NG; when the content is too high, the high-speed peeling force will be too high, resulting in paper breakage.

[0146] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An organosilicon pressure-sensitive adhesive composition for paper-based coating, characterized in that: The composition comprises the following components: Wherein, the viscosity of the vinyl-terminated polydimethylsiloxane A is 300 to 1,000 mPa·s; The viscosity of the vinyl-terminated polydimethylsiloxane B is 30,000 to 60,000 mPa·s; The viscosity of the vinyl-terminated polydimethylsiloxane C is 800 to 1,200 mPa·s.

2. The organic silicone pressure-sensitive adhesive composition according to claim 1, characterized in that: The composition comprises the following components:

3. The organic silicone pressure-sensitive adhesive composition according to claim 2, characterized in that: The composition comprises the following components:

4. The organic silicone pressure-sensitive adhesive composition according to any one of claims 1 to 3, characterized in that: The ratio of the weight of the vinyl-terminated polydimethylsiloxane B to the weight of the vinyl-terminated polydimethylsiloxane A, the vinyl-terminated polydimethylsiloxane B and the vinyl-terminated polydimethylsiloxane C is 0.3 to 0.6; And / or, the ratio of the weight of the vinyl-terminated polydimethylsiloxane C to the weight of the vinyl-terminated polydimethylsiloxane A, the vinyl-terminated polydimethylsiloxane B and the vinyl-terminated polydimethylsiloxane C is 0.02 to 0.08; And / or, the weight ratio of the methyl MQ resin to the sum of the weights of the vinyl-terminated polydimethylsiloxane A, the vinyl-terminated polydimethylsiloxane B and the vinyl-terminated polydimethylsiloxane C is 0.4 to 0.

8.

5. The organosilicon pressure-sensitive adhesive composition according to claim 4, characterized in that: The general structural formula of the vinyl-terminated polydimethylsiloxane A is as follows: (ViMe2SiO)-(SiMe2O) a -(SiMe2Vi), wherein the average value of a is 140 to 380, and the mass fraction of vinyl in the vinyl-terminated polydimethylsiloxane A is 0.18 to 0.45%; And / or, the general structural formula of the vinyl-terminated polydimethylsiloxane B is as follows: (ViMe2SiO)-(SiMe2O) b -(SiMeViO) c -(SiMe2Vi), wherein the average value of b+c is 1,000 to 1,480, and the mass fraction of vinyl in the vinyl-terminated polydimethylsiloxane B is 0.2 to 0.4%; And / or, the general structural formula of the vinyl-terminated polydimethylsiloxane C is as follows: (ViMe2SiO)-(SiMe2O) d -(SiMeViO) e -(SiMe2Vi), wherein the average value of d+e is 235-350, and the mass fraction of vinyl in the vinyl-terminated polydimethylsiloxane C is 2-3%.

6. The organosilicon pressure-sensitive adhesive composition according to claim 4, characterized in that: The general structural formula of the methyl MQ resin is as follows: (Me3SiO 1 / 2 ) f -(SiO 4 / 2 ) g , where the value ranges of f and g meet the following requirements: f>4, g>0, 0.6<(f / g)<1.0; Preferably, the weight average molecular weight of the methyl MQ resin is 4,000 to 8,000.

7. The organic silicone pressure-sensitive adhesive composition according to any one of claims 1 to 3, characterized in that: The cross-linking agent includes hydrogen-containing silicone oil; and / or, the anchoring agent comprises a silane coupling agent; and / or, the inhibitor is a monomer containing an unsaturated bond; And / or, the catalyst comprises a platinum catalyst.

8. The organosilicon pressure-sensitive adhesive composition according to claim 7, characterized in that: The viscosity of the hydrogen-containing silicone oil is 15 to 100 mPa·s, and the mass fraction of active hydrogen groups in the hydrogen-containing silicone oil is 1.4 to 1.6%; And / or, the silane coupling agent includes at least one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltriacetoxysilane; and / or, the inhibitor comprises at least one of maleic anhydride, 2-butyn-1-ol, 2-methyl-3-butyn-2-ol, 1-ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, tetramethyltetravinylcyclotetrasiloxane, tetramethyldivinyldisiloxane, and phenylacetylene; And / or, the platinum content in the platinum catalyst is 2,000 to 10,000 ppm.

9. A pressure-sensitive adhesive, characterized in that: The pressure-sensitive adhesive comprises the organic silicone pressure-sensitive adhesive composition according to any one of claims 1 to 8.

10. A pressure-sensitive adhesive product, characterized in that: The pressure-sensitive adhesive product comprises a substrate layer and an adhesive layer disposed on at least one side of the substrate layer, the adhesive layer comprises the pressure-sensitive adhesive of claim 9 or the organosilicon pressure-sensitive adhesive composition of any one of claims 1 to 8, and the substrate layer is paper-based.

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