Silicone pressure sensitive adhesive compositions, pressure sensitive adhesives and articles of manufacture useful for paper-based coating

Abstract

This invention relates to the field of silicone pressure-sensitive adhesive technology, and provides a silicone pressure-sensitive adhesive composition and product suitable for paper coating. The composition comprises 100 parts by weight of vinyl-terminated polydimethylsiloxane A, 42-165 parts by weight of vinyl-terminated polydimethylsiloxane B, 2.5-22 parts by weight of vinyl-terminated polydimethylsiloxane C, 57-150 parts by weight of methyl MQ resin, 4-11 parts by weight of crosslinking agent, 1.5-4 parts by weight of anchoring agent, 0.3-0.8 parts by weight of inhibitor, 3.5-8 parts by weight of catalyst, and 70-155 parts by weight of solvent. The pressure-sensitive adhesive formed by this silicone pressure-sensitive adhesive composition has good cohesive strength, moderate viscosity, is easy to peel off, can be applied using conventional coating methods, and requires a low drying temperature, making it suitable for direct paper coating.

Description

Technical Field

[0001] This invention relates to the field of silicone pressure-sensitive adhesive technology, specifically to a silicone pressure-sensitive adhesive composition, pressure-sensitive adhesive and its products that can be used for paper-based coating. Background Technology

[0002] Protective films are frequently used to protect the surface of consumer electronics products during manufacturing, shipping, and use to prevent dirt or scratches. These protective films typically employ a multi-layered structure with a paper base and double-sided AB adhesive. In this structure, the A side uses acrylic adhesive, which adheres to the paper base with high tack; the B side uses silicone adhesive, which adheres to the electronic product with low tack. Because these products have an embedded PET substrate layer to enhance structural strength, the overall structure has many layers, resulting in more manufacturing processes and higher material costs.

[0003] Conventional silicone pressure-sensitive adhesive formulations, whose main component is highly polymerized polydimethylsiloxane, require significant solvent dilution for easy coating. This results in a low adhesive solids content (typically <45%) during coating, making them suitable for coating non-paper substrates such as polyimide (PI), polyethylene terephthalate (PET), and polypropylene (PP). However, when the substrate is changed to paper, the introduction of excessive solvent can cause some solvent or even adhesive to penetrate into the paper fibers, leading to uneven coating thickness, glue seepage, and other defects that severely affect product quality and appearance. Furthermore, to allow the solvent to evaporate, the curing and drying temperatures are generally high (>120℃), which can cause the paper substrate to yellow, affecting product appearance and quality. Therefore, this type of silicone pressure-sensitive adhesive cannot be directly used for coating paper substrates. Summary of the Invention

[0004] The inventors of this invention have discovered that common silicone pressure-sensitive adhesives often use highly polymerized polydimethylsiloxane to improve the wettability of the adhesive. However, when bonded to steel plates or AF (Anti-fingerprint) screens, a high-speed peel force increase occurs. When such pressure-sensitive adhesives are used for direct coating on paper, paper tearing occurs under rapid peeling (e.g., 20,000 mm / min) due to the large peel force (>200 gf / in).

[0005] The purpose of this invention is to solve the problems existing in the prior art and provide an organosilicon pressure-sensitive adhesive composition, pressure-sensitive adhesive, and products thereof that can be used for paper-based coating. The pressure-sensitive adhesive prepared using the aforementioned organosilicon pressure-sensitive adhesive composition can be used for paper-based coating to obtain a paper-based direct-coating organosilicon pressure-sensitive adhesive protective film product. This pressure-sensitive adhesive has good cohesive strength, moderate viscosity, is easy to peel off, can be applied using conventional coating methods, and requires a low drying temperature, making the process simple.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] The first aspect of this invention provides an organosilicon 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 300–1,000 mPa·s;

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

[0011] The viscosity of the terminal vinyl polydimethylsiloxane C is 800–1,200 mPa·s.

[0012] In the silicone pressure-sensitive adhesive composition of this invention, the use of low-viscosity terminal vinyl polydimethylsiloxane A as the main component reduces solvent usage, preventing excessive solvent penetration into the paper fibers, which could lead to uneven adhesive thickness and glue seepage. It also lowers the viscosity of the pressure-sensitive adhesive composition, facilitating uniform coating. Adding a certain amount of high-viscosity terminal vinyl polydimethylsiloxane B strengthens the cohesion of the pressure-sensitive adhesive. Adding a certain amount of low-viscosity terminal vinyl polydimethylsiloxane C effectively adjusts the viscosity and cohesive strength of the pressure-sensitive adhesive to meet practical application requirements.

[0013] Therefore, this invention uses low-viscosity terminal vinyl polydimethylsiloxane A as the main component, combined with a certain amount of high-viscosity terminal vinyl polydimethylsiloxane B and low-viscosity terminal vinyl polydimethylsiloxane C, which can reduce the overall viscosity of the pressure-sensitive adhesive, thereby enabling the direct coating of high-solids-content pressure-sensitive adhesive on the paper substrate surface.

[0014] It should be noted that:

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

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

[0017] In this invention, the subscripts a, (b+c), (d+e), f, and g in the general formula of the polymer structure represent average values, that is, the average number of repeating units contained in the polymer macromolecular chain, or the degree of polymerization of the polymer.

[0018] In some embodiments, the general structural formula of the terminal vinyl polydimethylsiloxane A is as follows: (ViMe2SiO)-(SiMe2O) a -(SiMe2Vi), the average value of a is 140 to 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 of the two points above.

[0019] In some embodiments, the vinyl mass fraction in the terminal vinyl polydimethylsiloxane A is 0.18 to 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 within the range of the two values ​​above.

[0020] In some embodiments, the viscosity of the terminal vinyl polydimethylsiloxane A is 300 to 1,000 mPa·s, for example, it can be any value within the range of 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 the range of the two values ​​mentioned above.

[0021] In some embodiments, the content of the terminal vinyl polydimethylsiloxane B is 42 to 165 parts by weight, for example, it can be 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 of the two points above, preferably 55 to 120 parts by weight, and more preferably 70 to 95 parts by weight.

[0022] In some embodiments, the weight ratio of the terminal vinyl polydimethylsiloxane B to the sum of the weights of the terminal vinyl polydimethylsiloxane A, B, and 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 extremes. The requirement that the weight ratio of the terminal vinyl polydimethylsiloxane B to the sum of the weights of the three terminal vinyl polydimethylsiloxanes A, B, and C meets the above range is to ensure that the overall cohesive strength and viscosity of the pressure-sensitive adhesive composition meet the actual usage requirements of the final pressure-sensitive adhesive product. When this ratio is too low, it indicates that the amount of high-viscosity end-vinyl polydimethylsiloxane B added is insufficient. The pressure-sensitive adhesive prepared with too much low-viscosity end-vinyl polydimethylsiloxane has poor cohesive strength and the surface of the adhesive is easily damaged. When this ratio is too high, it indicates that the amount of high-viscosity end-vinyl polydimethylsiloxane B added is excessive. The overall viscosity of the resulting pressure-sensitive adhesive is too high, which is not conducive to coating. More solvent needs to be added during coating to reduce the viscosity of the pressure-sensitive adhesive to a viscosity range that is easy to apply. Generally, the viscosity of the adhesive coating needs to be controlled below 3,500 mPa·s. However, adding too much solvent is not conducive to direct coating on paper, and it is easy to cause uneven coating thickness, glue seepage and other defects, which seriously affect the product quality and appearance.

[0023] In some embodiments, the general structural formula of the terminal vinyl polydimethylsiloxane B is as follows: (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 within the range of the two points mentioned above. The degree of polymerization of the control-end vinyl polydimethylsiloxane B (i.e., the average value of b+c) is 1,000 to 1,480. The degree of polymerization is relatively low, which will not cause the overall viscosity of the pressure-sensitive adhesive to be too high, and also reduces the use of solvents, which can increase the solid content of the pressure-sensitive adhesive and is beneficial for the direct coating of the pressure-sensitive adhesive on the paper base.

[0024] In some embodiments, the vinyl mass fraction in the terminal vinyl polydimethylsiloxane B is 0.2 to 0.4%, for example, it can be 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, or any value within the range of the two points mentioned above.

[0025] In some embodiments, the viscosity of the vinyl polydimethylsiloxane B is 30,000 to 60,000 mPa·s, for example, it can be any value within the range of 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 the range of the two values ​​above.

[0026] In some embodiments, the content of the terminal vinyl polydimethylsiloxane C is 2.5 to 22 parts by weight, for example, it can be 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 of the two points above, preferably 9 to 14 parts by weight, and more preferably 10 to 12.5 parts by weight.

[0027] In some embodiments, the weight ratio of the terminal vinyl polydimethylsiloxane C to the sum of the weights of the terminal vinyl polydimethylsiloxane A, the terminal vinyl polydimethylsiloxane B, and the terminal vinyl 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 extremes. This ratio is specified here to adjust the overall wettability of the pressure-sensitive adhesive composition within a suitable range. When this ratio is too low, it indicates that the amount of vinyl-terminated polydimethylsiloxane C added is small. The wettability of the pressure-sensitive adhesive product (such as pressure-sensitive adhesive protective film) is still good, but the relatively high peel force at high speed peeling may lead to paper breakage or even direct tearing of the paper base. When this ratio is too high, it indicates that the amount of vinyl-terminated polydimethylsiloxane C added is high. The cross-linking density of the pressure-sensitive adhesive product is too high, the wettability decreases and it is difficult to adhere to the surface of the object. At the same time, the pressure-sensitive adhesive is too hard and brittle, which may also cause the surface of the adhesive to be easily damaged by external stress, resulting in abnormal phenomena such as glue peeling and powdering.

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

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

[0030] In some embodiments, the vinyl content in the vinyl-terminated polydimethylsiloxane C is 2-3% by mass, 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 within the range of the two values ​​mentioned above. The vinyl content of the vinyl-terminated polydimethylsiloxane C can significantly increase the overall crosslinking 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 terminal vinyl polydimethylsiloxane C is 800 to 1,200 mPa·s, for example, it can be any value within the range of 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 the range of the two values ​​mentioned above.

[0032] This invention incorporates vinyl-terminated polydimethylsiloxane C into the pressure-sensitive adhesive. Vinyl-terminated polydimethylsiloxane C has a high vinyl content (vinyl mass fraction of 2-3%), which significantly increases the crosslinking points and improves the hardness of the pressure-sensitive adhesive. The combination of vinyl-terminated polydimethylsiloxane C with low-viscosity vinyl-terminated polydimethylsiloxane A and high-viscosity vinyl-terminated polydimethylsiloxane B effectively controls the wettability of the pressure-sensitive adhesive, thereby preventing peel force spikes and paper breakage 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 of the two points above, 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 sum of the weights of the terminal vinyl polydimethylsiloxane A, the terminal vinyl polydimethylsiloxane B, and the terminal vinyl polydimethylsiloxane C is 0.4 to 0.8, specifically 0.4, 0.5, 0.6, 0.7, 0.8, or any value between these two extremes. This ratio is limited to the above range because the methyl MQ resin primarily functions as an tackifier. The amount of methyl MQ resin added determines the overall peel strength of the pressure-sensitive adhesive formulation. If the amount of methyl MQ resin added is too low, the resulting pressure-sensitive adhesive product will have low peel strength and will not adhere firmly to the surface of the object being adhered to (such as an AF screen). Poor adhesion will lead to abnormal phenomena such as peeling and arching during use. Conversely, if the amount of methyl MQ resin added is too high, the resulting pressure-sensitive adhesive product will have high peel strength, increasing the risk of paper breakage or even direct paper breakage during high-speed peeling.

[0035] In some embodiments, the general structural formula of the methyl MQ resin is as follows:

[0036] (Me3SiO 1 / 2 ) f -(SiO 4 / 2 ) g The range of values ​​for f and g must satisfy 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 within the range of the two values ​​mentioned above.

[0037] In some embodiments, the weight-average molecular weight of the methyl MQ resin is 4,000 to 8,000, for example, it can be any value within the range of 4,000, 5,000, 6,000, 7,000, 8,000 or the range of the two values ​​mentioned above.

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

[0039] In some embodiments, the content of the crosslinking agent is 4 to 11 parts by weight, for example, it can be 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 within the range of the two values ​​above, preferably 6 to 9 parts by weight, and more preferably 6.5 to 8 parts by weight. The type of crosslinking agent is not specifically limited, and all conventional crosslinking agents in the art are within the scope of protection of this invention.

[0040] In some embodiments, the crosslinking 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, it can be 15 mPa·s, 20 mPa·s, 40 mPa·s, 60 mPa·s, 80 mPa·s, 100 mPa·s or any value within the range of the two values ​​mentioned above.

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

[0043] In this invention, hydrogen-containing silicone oil with a high content of active hydrogen groups is selected as a crosslinking agent. The Si-H bonds therein can undergo 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, it can be 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 within the range of the two values ​​above, preferably 2 to 3 parts by weight. The type of anchoring agent is not specifically limited; all conventional anchoring agents in the art are within the scope of protection of this invention.

[0045] In some embodiments, the anchoring agent comprises a silane coupling agent; preferably, the silane coupling agent comprises 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 both organic-inorganic hybrid bifunctional compounds, which chemically react 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, increasing its cohesiveness. These organic functional groups also contain methoxy, ethoxy, and acetoxy groups, which readily hydrolyze into silanols. After hydrolysis, these groups can react with oxides or hydroxyl groups on the paper substrate surface to form siloxane bonds. This dual chemical bonding effect allows the silane coupling agent (anchoring agent) to tightly bond the silicone pressure-sensitive adhesive to the substrate, improving the adhesive strength.

[0047] In some embodiments, the catalyst content is 3.5 to 8 parts by weight, for example, it can be 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 within the range of the two values ​​above, 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; conventional catalysts in the art are all within the scope of protection of this invention.

[0048] In some embodiments, the catalyst comprises 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 extremes; if the platinum content is below the above-defined range, the catalyst activity is insufficient; if it exceeds the above range, on the one hand, the price of platinum is high, which will increase the raw material cost, and on the other hand, the excessive platinum content will cause the pressure-sensitive adhesive to undergo a cross-linking reaction prematurely. The prepared pressure-sensitive adhesive will undergo a cross-linking reaction before entering the coating oven, and will cure prematurely, making it impossible to complete the subsequent preparation of pressure-sensitive adhesive products.

[0049] In some embodiments, the content of the inhibitor is 0.3 to 0.8 parts by weight, for example, it can be 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 within the range of the two values ​​above, preferably 0.4 to 0.6 parts by weight, and more preferably 0.5 to 0.6 parts by weight. The type of inhibitor is not specifically limited, and conventional inhibitors in the art are all within the scope of protection of this invention.

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

[0051] Because the addition of a catalyst (such as a platinum catalyst) to the pressure-sensitive adhesive composition causes an immediate reaction, the pressure-sensitive adhesive cures before coating. Inhibitors can temporarily suppress the catalytic activity of the catalyst. When the pressure-sensitive adhesive is needed, the inhibitor can be deactivated by heating, thereby releasing the catalytic activity of the catalyst and curing the pressure-sensitive adhesive. This facilitates the stability of the pressure-sensitive adhesive during storage or transportation, extending its shelf life.

[0052] In some embodiments, the solvent content is 70 to 155 parts by weight, for example, it can be 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 within the range of the two values ​​above, preferably 80 to 130 parts by weight, and more preferably 90 to 115 parts by weight. This invention does not specifically limit the type of solvent; conventional solvents in the art are all within the scope of protection of this 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, more preferably a combination of ethyl acetate and n-heptane, and more preferably the mass ratio of ethyl acetate to n-heptane is 1 to 1.1, specifically 1, 1.03, 1.04, 1.05, 1.06, 1.1, or any value between the two extremes. Ethyl acetate has a boiling point of 76.5 to 77.5°C, and n-heptane has a boiling point of 98°C. The use of a combination of two solvents with different boiling points in this invention allows the lower-boiling-point ethyl acetate to evaporate first, followed by the higher-boiling-point n-heptane, enabling rapid solvent evaporation within a shorter drying time. This avoids prolonged solvent retention on the paper base, which could lead to glue seepage into the paper base, resulting in uneven glue thickness, glue seepage, and other defects.

[0054] To avoid incomplete solvent evaporation after curing, which could reduce the adhesive strength, the curing temperature of the adhesive must be greater than or equal to the boiling point of the solvent. Conventional silicone pressure-sensitive adhesive formulations, due to their high solvent content and potential inclusion of high-boiling-point solvents, typically require curing temperatures exceeding 120°C during coating. However, these high temperatures can easily cause yellowing of the paper substrate in the oven, affecting the finished product's appearance. In this invention, the pressure-sensitive adhesive uses a smaller amount of solvent and has a higher solids content, reducing both drying time and temperature. The pressure-sensitive adhesive described in this invention uses a low-boiling-point solvent, enabling low-temperature curing and preventing yellowing of the paper substrate due to high-temperature curing.

[0055] A second aspect of the present invention provides a pressure-sensitive adhesive, the pressure-sensitive adhesive comprising the organosilicon pressure-sensitive adhesive composition described in the first aspect of the present invention.

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

[0057] (1) Add the measured weight parts of terminal vinyl polydimethylsiloxane A, terminal vinyl polydimethylsiloxane B, and terminal vinyl polydimethylsiloxane C to the reactor, add methyl MQ resin and the first solvent while stirring, heat the mixture to 75-85°C, stir for 1.5-2.5 hours in a closed environment, then stop heating and allow it to cool naturally to room temperature.

[0058] (2) Then, while stirring, add the crosslinking agent, anchoring agent, inhibitor, catalyst and second solvent in the measured weight parts, mix evenly, and the silicone pressure-sensitive adhesive to be coated is obtained.

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

[0060] (1) Add the measured weight of vinyl-terminated polydimethylsiloxane A to the reactor, add methyl MQ resin and the first solvent while stirring, heat the mixture to 75-85°C, stir for 1.5-2.5 hours in a closed environment, then stop heating and let it cool naturally to room temperature.

[0061] (2) Then, while stirring, add the measured weight parts of terminal vinyl polydimethylsiloxane B, terminal vinyl polydimethylsiloxane C, crosslinking agent, anchoring agent, inhibitor, catalyst and second solvent, mix evenly, and the silicone pressure-sensitive adhesive to be coated is obtained.

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

[0063] The pressure-sensitive adhesive of the present invention has a viscosity of 80 to 2,500 mPa·s at room temperature (25°C), 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 between the two extremes.

[0064] The pressure-sensitive adhesive of the present invention has a solid content of 75% to 90%, specifically 75%, 80%, 90%, or any value between these two extremes. The pressure-sensitive adhesive of the present invention has a high solid content and a low solvent content, facilitating rapid solvent evaporation and preventing solvent retention time that could lead to seepage into the paper base, resulting in uneven adhesive thickness, glue seepage, and other defects.

[0065] A third aspect of the present invention provides a pressure-sensitive adhesive product, the pressure-sensitive adhesive product comprising a substrate layer and an adhesive layer disposed on at least one side of the substrate layer, the adhesive layer comprising the pressure-sensitive adhesive described in the second aspect of the present invention or containing an organosilicon pressure-sensitive adhesive composition described in the first aspect of the present invention, the substrate layer being paper-based.

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

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

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

[0069] In this 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 this 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 this invention can be configured as a single-sided or double-sided adhesive sheet. If the adhesive is applied only to one side of the substrate layer, it is a single-sided adhesive sheet; if it is applied to both sides of the substrate layer, it is a double-sided adhesive sheet. A release film can be applied to the surface of the adhesive sheet layer, which 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-silicone release film, composite release film, etc. There is no particular limitation on the thickness of the release film; different thicknesses can generally be used according to actual winding or cost requirements.

[0072] The present invention, by adopting the above technical solution, has the following beneficial effects:

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

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

[0075] (3) The silicone pressure-sensitive adhesive provided by the present invention has added a high vinyl content end vinyl polydimethylsiloxane C component, which has low high-speed peel force and will not cause paper breakage. Detailed Implementation

[0076] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

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

[0078] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0079] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. In the following examples, 1g represents one part by weight.

[0080] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0081] Table 1 below lists the sources and related properties of the raw materials used in the embodiments 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 embodiments of the present invention were all 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 products specially supplied by the supplier according to the required viscosity and vinyl content of the vinyl silicone oil.

[0086] Examples 1-6

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

[0088] The amounts of each component are shown in Table 2. Vinyl-terminated polydimethylsiloxane A, vinyl-terminated polydimethylsiloxane B, and vinyl-terminated polydimethylsiloxane C were added sequentially to the reactor by weight, and the mixture was heated while stirring until it reached 80°C. Methyl MQ resin was added in four equal portions during stirring, followed by the addition of heptane solvent and stirring in a sealed container for 2 hours. After mixing evenly, heating was stopped. After the adhesive cooled to below 30°C, the crosslinking agent (hydrogen-containing silicone oil), anchoring agent (KH-560), inhibitor (1-ethynylcyclohexanol), platinum catalyst, and ethyl acetate solvent (EA) were added sequentially and stirred evenly to obtain an organosilicon pressure-sensitive adhesive with a solid content of 75%.

[0089] Table 2

[0090]

[0091]

[0092] Note: m A The weight of terminal vinyl polydimethylsiloxane A;

[0093] m B The weight of terminal vinyl polydimethylsiloxane B;

[0094] m C The weight of the terminal vinyl polydimethylsiloxane C;

[0095] m A +m B +m C This represents the total mass of the three vinyl-terminated polydimethylsiloxanes;

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

[0097] Example 7 group

[0098] The preparation methods for this set of examples are the same as those described above. The main difference is that the type of vinyl-terminated polydimethylsiloxane A in the silicone pressure-sensitive adhesive is different. Its dosage and other components and compositions are the same as in Example 1. The specific differences are as follows:

[0099] Example 7a: Vinyl-terminated polydimethylsiloxane A was used in equal amounts of Al;

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

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

[0102] Example 7d: The vinyl-terminated polydimethylsiloxane A was replaced with an equal amount of A5.

[0103] Example 8 group

[0104] The preparation methods for this set of examples are the same as those described above. The main difference is that the type of vinyl-terminated polydimethylsiloxane B in the silicone pressure-sensitive adhesive is different. Its dosage and other components and compositions are the same as in Example 1. The specific differences are as follows:

[0105] Example 8a: Vinyl-terminated polydimethylsiloxane B was used in equal amounts with B1;

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

[0107] Example 8c: The vinyl-terminated polydimethylsiloxane B was replaced with an equal amount of B4;

[0108] Example 8d: The vinyl-terminated polydimethylsiloxane B was replaced with an equal amount of B5.

[0109] Example 9 group

[0110] The preparation methods for this set of examples are the same as those described above. The main difference is that the type of vinyl-terminated polydimethylsiloxane C in the silicone pressure-sensitive adhesive is different. Its dosage and other components and compositions are the same as in Example 1. The specific differences are as follows:

[0111] Example 9a: The vinyl-terminated polydimethylsiloxane C used was an equal amount of C1;

[0112] Example 9b: The vinyl-terminated polydimethylsiloxane C used was an equal amount of C3;

[0113] Example 9c: The vinyl-terminated polydimethylsiloxane C used was an equal amount of C4;

[0114] Example 9d: The vinyl-terminated polydimethylsiloxane C used was an equal amount of C5.

[0115] Comparative Examples 1-3

[0116] Comparative Examples 1-3 were carried out in accordance with Example 1, with the main difference being that the components of the silicone pressure-sensitive adhesive were changed, as shown in Table 3.

[0117] Table 3

[0118]

[0119] Comparative Example 4

[0120] This comparative example is based on Example 1, except that a commercially available silicone component is used to prepare a conventional pressure-sensitive adhesive, the main component of which is 100g of DOWSIL from Dow Chemical Company. TM 7647 (viscosity 7500 mPa·s) and 100g of DOWSIL TM The combination of 7657 (viscosity 22500 mPa·s) and the platinum catalyst using Dow Chemical's SYL-OFF TM Mix 4000 5.7g of the mixture thoroughly to obtain a conventional pressure-sensitive adhesive.

[0121] Performance testing

[0122] The silicone pressure-sensitive adhesives prepared in the above embodiments and comparative examples were directly coated onto 115g coated paper and cured in an oven at 110℃ for 90s to obtain an adhesive layer with a theoretical thickness of 13μm, thus 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 10cm×10cm pieces of coated paper, test their weight at room temperature (25℃), and record the average value as m1 (g); then cut three more 10cm×10cm pieces of coated paper after applying the adhesive, test their weight at room temperature (25℃), and record the average value as m2 (g); the density of the silicone pressure-sensitive adhesive is calculated as 1g / cm³. 3 The ratio of the weight difference to the area is the theoretical thickness h (μm) of the adhesive layer, i.e.:

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

[0125] Test Project

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

[0127] II. 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 droplet angle greater than 115°. The test is conducted using a Kejian 90° tensile tester according to the international standard ASTM D3330 "Standard Test Method for Peel Adhesion Strength of Pressure Sensitive Adhesive Tapes". The application scenario of the protective film being peeled off is simulated. The peel force is recorded at peel speeds of 300 mm / min (minimum peel speed) and 20,000 mm / min (maximum peel speed).

[0128] III. The criteria for determining whether the paper is broken are as follows: After the above 90° peel force test, observe whether there are any coated paper fragments remaining on the AF screen surface. If there are no coated paper fragments, record it as "No"; if there are, record it as "Yes"; if the paper base is broken, record it as "Broken".

[0129] IV. Simulated Adhesion After Transportation: A simulated transportation vibration table (manufacturer: Guangdong Kejian Instrument Co., Ltd., model: KJ-8030) was used for simulation, with a time of 24 hours and a vehicle speed of 110 km / h. When peeling at low speed (300 mm / min), if the peel force of the protective film relative to the AF screen is less than 3.5 gf / in, it can be inferred that poor adhesion, film falling off, arching, and other defects may occur during transportation, and this is recorded as NG; conversely, if the peel force is greater than or equal to 3.5 gf / in, it is recorded as OK.

[0130] Cohesion determination of adhesive surface: Place the test piece on a sufficiently hard flat plate. Hold the handle of the cross-cutting tool, keeping the multi-blade cutter perpendicular to the test piece surface. Cut the surface with uniform pressure, a steady and stationary motion, and a cutting speed of 20-50 mm / s. Then rotate the test piece 90° and repeat the above operation on the cut surfaces to form a grid pattern. Use 4D MY2G special test tape, apply the tape to the entire grid, and roll it back and forth twice with a 2 kg roller. After rolling, allow it to rest for 1 minute. Result Judgment: "Excellent" indicates that the edges of the cut are completely smooth and there is no peeling at the edges of the grid; "Good" indicates that there is small peeling at the intersection of the cuts, and the actual damage in the grid area does not exceed 10%; "Medium" indicates that there is peeling at the edges and intersections of the cuts, and the area is greater than 10% but less than 30%; "Poor" indicates that there is partial or large-scale peeling at the edges of the cuts, or some grids are peeled off in whole, and the peeling area exceeds 30%.

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

[0132] Coating effect assessment: Based on industry experience and the inventor's coating practice, the microgravure coating adhesive viscosity is best when it is between 25 and 350 mPa·s. Within this range, the film surface is smooth and the effect is rated as excellent. In other ranges, the film surface has slight unevenness and the effect is rated as good. For blade coating, the adhesive viscosity is best when it is between 200 and 3,500 mPa·s. Within this range, the film surface is smooth and the effect is rated as excellent. In other ranges, the film surface has slight unevenness and the effect is rated as good. Viscosities exceeding these ranges will result in poor adhesive leveling, preventing uniform coating on the substrate surface, and thus a poor effect.

[0133] Paper yellowing test: The b value of the coated paper used in this embodiment of the invention was tested using a spectrophotometer (Konica Minolta CM-2500d) after drying at different temperatures for 90s. The change in b value Δb (b value after baking minus the b value of the original paper) was calculated. Δb represents the degree of yellowing of the coated paper. The larger the value of Δb, the more severe the yellowing. The results are shown in Table 5.

[0134] Table 4 Performance Test Results

[0135]

[0136] Table 5 Results of Yellowing Test on Paper Base

[0137]

[0138] As shown in Table 5, when coated paper is placed in an environment of 120°C or lower, the change in b-value Δb (b-value after baking minus the b-value of the original paper) is less than 0.2, which can be considered as a very small color change. When the temperature reaches 130°C or higher, Δb > 0.2, the b-value increases significantly, and the paper base undergoes obvious yellowing. The pressure-sensitive adhesive of this invention uses a solvent with a boiling point below 110°C, resulting in a low curing temperature. Furthermore, the pressure-sensitive adhesive has a high solids content, requires less solvent, and has a short curing time, effectively avoiding the yellowing of the paper base caused by high curing temperature and long curing time.

[0139] As shown in Table 4, the test results of Examples 1-6 and Comparative Example 4 indicate that the pressure-sensitive adhesive prepared by the pressure-sensitive adhesive composition provided by the present invention can achieve direct coating of paper substrates with high solids content without the need for transfer coating. The adhesive has good leveling properties, can be coated evenly, and does not exhibit poor adhesion, peeling, or arching during simulated transportation. By reasonably controlling the relative content of each component, a pressure-sensitive adhesive that meets the requirements for microgravure coating or doctor blade coating, and whose adhesion and cohesive properties also meet the application requirements, can be obtained. After being coated with paper substrates and bonded to AF screens, it can meet both high-speed and low-speed peeling requirements without paper breakage.

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

[0141] The test results of Example 8 show that if the viscosity of vinyl-terminated polydimethylsiloxane B is not within the specified range, there will be unqualified cohesion of the film or uneven coating.

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

[0143] The test results of Comparative Example 1 show that if the content of vinyl-terminated polydimethylsiloxane B is low or absent, the cohesion of the adhesive surface is poor; if the content is high, it will lead to a higher viscosity of the pressure-sensitive adhesive, which is not conducive to coating.

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

[0145] The test results of the three groups show that if the content of methyl MQ resin is too low, there will be NG in simulated transportation adhesion; if the content is too high, the high-speed peel force will be too high, resulting in paper breakage.

[0146] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A silicone pressure-sensitive adhesive composition suitable for paper-based coating, characterized in that, The composition comprises the following components: Vinyl-terminated polydimethylsiloxane A 100 parts by weight Vinyl-terminated polydimethylsiloxane B 42~165 parts by weight Vinyl-terminated polydimethylsiloxane C 2.5~22 parts by weight 57-150 parts by weight of methyl MQ resin 4-11 parts by weight of crosslinking agent 1.5 to 4 parts by weight of anchoring agent Inhibitor 0.3~0.8 parts by weight 3.5 to 8 parts by weight of catalyst Solvent 70~155 parts by weight Wherein, the viscosity of the vinyl-terminated polydimethylsiloxane A is 300~1,000 mPa·s; The general structural formula of the vinyl-terminated polydimethylsiloxane A is as follows: (ViMe2SiO)-(SiMe2O) a -(SiMe2Vi), wherein the average value of a is 140~380, and the vinyl mass fraction in the terminal vinyl polydimethylsiloxane A is 0.18~0.45%; The viscosity of the vinyl-terminated polydimethylsiloxane B is 30,000~60,000 mPa·s; 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 1,000~1,480, and the vinyl mass fraction in the terminal vinyl polydimethylsiloxane B is 0.2~0.4%; The viscosity of the vinyl-terminated polydimethylsiloxane C is 800~1,200 mPa·s; 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 vinyl mass fraction in the end-vinyl polydimethylsiloxane C is 2~3%.

2. The organosilicon pressure-sensitive adhesive composition according to claim 1, characterized in that, The composition comprises the following components: Vinyl-terminated polydimethylsiloxane A 100 parts by weight Vinyl-terminated polydimethylsiloxane B 55~120 parts by weight Vinyl-terminated polydimethylsiloxane C 9-14 parts by weight 90-130 parts by weight of methyl MQ resin 6-9 parts by weight of crosslinking agent 2-3 parts by weight of anchoring agent Inhibitor 0.4~0.6 parts by weight Catalyst 4.5~6.5 parts by weight Solvent: 80-130 parts by weight.

3. The organosilicon pressure-sensitive adhesive composition according to claim 2, characterized in that, The composition comprises the following components: Vinyl-terminated polydimethylsiloxane A 100 parts by weight Vinyl-terminated polydimethylsiloxane B 70-95 parts by weight Vinyl-terminated polydimethylsiloxane C 10~12.5 parts by weight 100-115 parts by weight of methyl MQ resin Crosslinking agent 6.5~8 parts by weight 2-3 parts by weight of anchoring agent Inhibitor 0.5~0.6 parts by weight 5-6 parts by weight of catalyst Solvent 90~115 parts by weight.

4. The organosilicon pressure-sensitive adhesive composition according to any one of claims 1-3, characterized in that, The weight ratio of the terminal vinyl polydimethylsiloxane B to the sum of the weights of the terminal vinyl polydimethylsiloxane A, the terminal vinyl polydimethylsiloxane B, and the terminal vinyl polydimethylsiloxane C is 0.3 to 0.

6. And / or, the weight ratio of the terminal vinyl polydimethylsiloxane C to the sum of the weights of the terminal vinyl polydimethylsiloxane A, the terminal vinyl polydimethylsiloxane B, and the terminal vinyl 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 terminal vinyl polydimethylsiloxane A, the terminal vinyl polydimethylsiloxane B, and the terminal vinyl 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 methyl MQ resin is as follows: (Me3SiO) 1 / 2 ) f -(SiO 4 / 2 ) g The values ​​of f and g must satisfy the following requirements: f>4, g>0, 0.6<(f / g)<1.

0.

6. The organosilicon pressure-sensitive adhesive composition according to claim 1, characterized in that, The weight-average molecular weight of the methyl MQ resin is 4,000 to 8,000.

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

8. The silicone pressure-sensitive adhesive composition according to claim 7, characterized in that, The viscosity of the hydrogen-containing silicone oil is 15~100 mPa·s, and the mass fraction of active hydrogen groups in the hydrogen-containing silicone oil is 1.4~1.6%. And / or, the silane coupling agent comprises 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 includes the silicone pressure-sensitive adhesive composition according to any one of claims 1-8.

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

Images