A fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive and its preparation method

Abstract

The present invention discloses a fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive and a preparation method thereof. By regulating the soft and hard segment structures and the content of polar groups of the polyurethane, precise regulation of viscoelasticity, glass transition temperature and adhesive properties can be achieved. The soft segment is composed of a polyol with a low glass transition temperature and a highly polar polycarbonate diol, enabling the material to maintain appropriate viscoelasticity and adhesiveness; the hard segment is composed of a diisocyanate and a short-chain diol, endowing the hot melt pressure-sensitive adhesive with excellent mechanical strength and aging resistance. By adjusting the ratio of different diols, the initial adhesion and peel strength of the hot melt pressure-sensitive adhesive can be effectively controlled, so as to meet the application requirements in different fields. The polyurethane hot melt pressure-sensitive adhesive of the present invention uses carbon dioxide-based polycarbonate diol as a raw material, which not only reduces the dependence on petrochemical resources and realizes the efficient reuse of carbon dioxide, but also is easily biodegradable while achieving good bonding performance.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure-sensitive adhesives, and specifically, to a fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive and a preparation method thereof. Background Art

[0002] In recent years, with the enhancement of environmental awareness and the gradual implementation of various environmental protection regulations, the development and application of degradable materials have become a research hotspot. Traditional pressure-sensitive adhesive materials mostly use non-degradable polymers and a large amount of organic volatile solvents, resulting in the difficulty of degradation of the finished products and long-term environmental pollution after abandonment. At the same time, the organic solvents contained in these pressure-sensitive adhesives are volatile during production and use, generating volatile organic compounds, which have harmful effects on human health and air quality. Hot melt pressure-sensitive adhesives are a type of pressure-sensitive adhesive without organic solvents and with a solid content of 100%, having the advantages of being melt-coated when heated and achieving adhesion by pressing at room temperature. Existing hot melt pressure-sensitive adhesives mainly use materials based on non-degradable elastomers such as styrene block copolymers and polyacrylates. Although the pressure-sensitive adhesives prepared from these materials have good initial tack and peel strength, they are difficult to degrade naturally in the environment, and most of the raw materials are derived from petroleum resources.

[0003] Carbon dioxide, as a greenhouse gas with a large amount of emissions, has caused serious environmental pollution. In recent years, efforts have been made at home and abroad to study the ring-opening copolymerization of carbon dioxide and epoxy monomers to develop biodegradable carbon dioxide-based plastics such as polyurethanes. Due to the introduction of carbonate bonds, the prepared polycarbonate and polycarbonate polyol carbon dioxide-based raw materials are easy to biodegrade. Polyurethane is a polymer material formed by the reaction of poly(di)ols and poly(di)isocyanates to form urethane bonds. Among them, polyols with a low glass transition temperature are the soft segments, and small molecule isocyanates and diols are the hard segments. By adjusting the ratio of the soft and hard segments, the types and contents of polar groups, the viscoelasticity and adhesiveness of the material can be controlled. The adjustable nature of this structure makes polyurethane an ideal material for hot melt pressure-sensitive adhesives, capable of providing customized solutions according to the high-performance requirements of different application fields and industries.

[0004] Using biodegradable polycarbonate polyols (Chinese Patent CN116355195A) as the main raw material of polyurethane, strong polar and hydrolyzable carbonate bonds are introduced into the polymer main chain, making the synthesized polymer material biodegradable (Molecules, 2024, 29, 4364), and the adhesion performance will also be improved. Summary of the Invention

[0005] To solve the problems that the main components in existing pressure-sensitive adhesive materials are non-degradable and organic solvents need to be used, which pollute the environment, the present invention provides a fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive and its preparation method. The hot melt pressure-sensitive adhesive uses carbon dioxide-based biodegradable polycarbonate diol as the main raw material, which not only reduces the dependence on petrochemical resources, but also realizes the efficient reuse of carbon dioxide in industrial waste gas. The obtained polyurethane hot melt pressure-sensitive adhesive has biodegradability under natural conditions, which helps to reduce environmental pollution.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive, whose chemical structural formula is shown in Formula (1), where m≥1, n≥1, y≥1, z≥1, w≥0; m, n, y, z, w are all integers; R1 is the side chain of an epoxy monomer, R2 is an aliphatic hydrocarbon group with 2 to 6 carbon atoms, R3 is the main chain of a polyether diol, R4 is the main chain of a diisocyanate, and R5 is the main chain of a chain extender; X is an -NH- group or an -O- group;

[0008]

[0009] The preparation method of the fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive includes the following steps:

[0010] (1) Heat and dry the polycarbonate diol and polyether diol under vacuum conditions. The drying temperature is 100~120 °C, and the drying time is 1~3 h;

[0011] (2) Cool down under nitrogen protection, dropwise add a mixture of diisocyanate, catalyst, polyether diol and chain extender and stir. During the reaction process, gradually increase the temperature according to the viscosity of the polymer. The stirring rate is 300~400 r / min, the reaction temperature is 60~120 °C, and the reaction time is 3~12 h to obtain a fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive; the mass percentages of each component are: polycarbonate diol 40~76%, polyether diol 10~50%, diisocyanate 8~20%, chain extender 0~3%, catalyst 0.05~0.5%.

[0012] Preferably, the chemical structural formula of the polycarbonate diol is shown in Formula (2), where m≥1, n≥1, m, n are all integers; R1 is the side chain of an epoxy monomer, R2 is an aliphatic hydrocarbon group with 2 to 6 carbon atoms, the number-average molecular weight is 600~6000 g / mol, and the polycarbonate content ≥95%;

[0013]

[0014] Preferably, the polyether diol is one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol.

[0015] Preferably, the diisocyanate is one or more of aliphatic diisocyanates, cycloaliphatic diisocyanates, or aromatic diisocyanates.

[0016] Preferably, the chain extender is one or more of ethylene glycol, 1,3 - propanediol, 1,2 - propanediol, 1,4 - butanediol, 1,6 - hexanediol, 1,4 - cyclohexanedimethanol, diethylene glycol, ethanolamine, triisopropanolamine, ethylenediamine, methylcyclohexanediamine, 3,5 - dimethylthiotoluenediamine, 3,5 - diethyltoluenediamine, and glycerol.

[0017] Preferably, the catalyst is one or more of stannous octoate, dibutyltin dilaurate, stannous oleate, tetrabutylammonium chloride, triethylamine, triethylenediamine, pentamethyldiethylenetriamine, and triethanolamine.

[0018] Compared with the existing technologies, the present invention has the following beneficial effects:

[0019] (1) The present invention provides a fully biodegradable polycarbonate - type polyurethane hot - melt pressure - sensitive adhesive for the first time. This polyurethane hot - melt pressure - sensitive adhesive mainly uses carbon dioxide - based polycarbonate diol as the raw material, which not only reduces the dependence on petrochemical resources and realizes the efficient reuse of carbon dioxide, but also the obtained polyurethane is easy to biodegrade while achieving good adhesion performance. As a green and degradable pressure - sensitive adhesive, it can reduce the burden on the environment caused by traditional non - degradable adhesives.

[0020] (2) By regulating the hard - and soft - segment structure and the content of polar groups of the polyurethane, the present invention can precisely control the viscoelasticity, glass transition temperature, and adhesion performance. The soft segment is composed of a polyol with a low glass transition temperature (T g <-20 °C) and a highly polar polycarbonate diol, enabling the material to maintain appropriate viscoelasticity and adhesiveness; the hard segment is composed of diisocyanate and short - chain diol, endowing the hot - melt pressure - sensitive adhesive with excellent mechanical strength and aging resistance. By adjusting the ratio of different diols, the initial adhesion and peel strength of the hot - melt pressure - sensitive adhesive can be effectively controlled, so as to meet the application requirements in different fields.

[0021] (3) The present invention prepares the polyurethane hot - melt pressure - sensitive adhesive by melt bulk polymerization, completely avoiding the use of organic solvents, reducing the emission of volatile organic compounds, meeting the environmental protection requirements, and having a simple preparation process, which is suitable for large - scale industrial production. This process not only reduces the production cost but also reduces the energy consumption, making the prepared hot - melt pressure - sensitive adhesive more in line with the requirements of sustainable development and green manufacturing. Description of the Drawings

[0022] Figure 1 DSC schematic diagram of the polyurethane prepared in Example 2 of the present invention;

[0023] Figure 2 Thermal decomposition schematic diagram of the polyurethane prepared in Example 2 of the present invention;

[0024] Figure 3 180° peel test curve of the hot melt pressure-sensitive adhesive of the polyurethane prepared in Example 2 of the present invention;

[0025] Figure 4 180° peel strength curve of the Deli 30170 tape in the comparative example. Specific embodiments

[0026] The content of the present invention will be further described below in conjunction with specific embodiments, but it should not be construed as a limitation to the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0027] The test methods involved in the embodiments refer to the following standards: GB / T 31125-2014 "Test method for initial tack of pressure-sensitive adhesive tapes - Loop method", GB / T 2792-2014 "Test method for 180° peel strength of pressure-sensitive adhesive tapes". Example 1:

[0028] (1) Add 20 g of polycarbonate diol with a molecular weight of Mn = 2241 g / mol (hydroxyl value of 50.07 mgKOH / g) having the structure of formula (2) and 2 g of polypropylene glycol with a molecular weight of Mn = 2239 g / mol (hydroxyl value of 50.12 mgKOH / g) to a 250 mL round-bottom flask and evacuate water at 120 °C for 2 h. The raw materials are cooled to 90 °C under a nitrogen atmosphere, and 3.28 g of dicyclohexylmethane diisocyanate, 0.0273 g of catalyst stannous octoate, and 2.00 g of polypropylene glycol are slowly added dropwise. During the reaction process, the temperature is gradually increased according to the viscosity of the polymer, and the mixture is stirred and reacted at a stirring speed of 300 r / min for 6 h. Pour it into a mold and cool. The obtained polyurethane has two glass transition temperatures, T g = -53.4 °C, 39.2 °C. The mass ratio of each component is: polycarbonate diol 73.2%, polypropylene glycol 14.7%, dicyclohexylmethane diisocyanate 12.0%, stannous octoate 0.1%.

[0029] (2) Place the polyurethane in a flat vulcanizing machine and hot-press it at 120 °C and 1 MPa for 10 min to obtain a film with a thickness of 30 - 50 μm. According to the requirements of GB / T 31125-2014 "Test Method for Tack of Pressure-Sensitive Adhesive Tapes - Ring Method", use a PET film with a thickness of 50 μm as the substrate, and conduct the initial tack (GB / T 31125-2014) and 180° peel test (GB / T 2792-2014) on the prepared sample strips according to the national standard. The initial tack of the obtained polyurethane hot-melt pressure-sensitive adhesive is 0.61 N, and the 180° peel strength is 0.22 N / 25mm. Example 2:

[0030] (1) Add 20 g of polycarbonate diol with a structure as shown in formula (2) and a molecular weight of Mn = 2241 g / mol (hydroxyl value of 50.07 mgKOH / g) and 5 g of polypropylene glycol with a molecular weight of Mn = 2239 g / mol (hydroxyl value of 50.12 mgKOH / g) into a 250 mL round-bottom flask and evacuate to remove water at 120 °C for 2 h. The raw materials are cooled to 90 °C under a nitrogen atmosphere, and 4.37 g of dicyclohexylmethane diisocyanate, 0.0364 g of catalyst stannous octoate, and 7.00 g of polypropylene glycol are slowly added dropwise. During the reaction process, the temperature is gradually increased according to the viscosity of the polymer, and the mixture is stirred and reacted at a stirring speed of 300 r / min for 6 h. Pour it into a mold and cool. The obtained polyurethane has two glass transition temperatures, T g = -57.5 °C, 31.2 °C, and the mass ratio of each component is: polycarbonate diol 54.9%, polypropylene glycol 33.0%, dicyclohexylmethane diisocyanate 12.0%, stannous octoate 0.1%.

[0031] (2) Prepare the pressure-sensitive adhesive sample strips according to the method of Example 1 and conduct the initial tack (GB / T31125-2014) and 180° peel test (GB / T 2792-2014) according to the national standard. The initial tack of the obtained polyurethane hot-melt pressure-sensitive adhesive is 12.44 N, and the 180° peel strength is 9.95 N / 25mm. Example 3:

[0032] (1) Add 20 g of polycarbonate diol with a molecular weight of Mn = 2241 g / mol (hydroxyl value of 50.07 mgKOH / g) having the structure of formula (2) and 5 g of polypropylene glycol with a molecular weight of Mn = 2239 g / mol (hydroxyl value of 50.12 mgKOH / g) into a 250 mL round-bottom flask, and evacuate and remove water at 120 °C for 2 h. The polyol raw material is cooled to 90 °C under a nitrogen atmosphere, and 5.19 g of dicyclohexylmethane diisocyanate, 0.0432 g of stannous octoate as a catalyst, and 13.00 g of polypropylene glycol are slowly added dropwise. During the reaction process, the temperature is gradually increased according to the polymer viscosity, and the mixture is stirred and reacted at a stirring speed of 300 r / min for 6 h. Pour it into a mold and cool. The obtained polyurethane has two glass transition temperatures, T g = -57.2 °C, 28.6 °C, and the mass percentage of each component is: polycarbonate diol 46.3%, polypropylene glycol 41.6%, dicyclohexylmethane diisocyanate 12.0%, stannous octoate 0.1%.

[0033] (2) Prepare the pressure-sensitive adhesive strip according to the method of Example 1 and conduct the initial tack (GB / T31125-2014) and 180° peel test (GB / T 2792-2014) according to the national standard respectively. The initial tack of the obtained polyurethane hot melt pressure-sensitive adhesive is 14.00 N, and the 180° peel strength is 6.71 N / 25mm. Example 4:

[0034] (1) Add 20 g of polycarbonate diol with a molecular weight of Mn = 2241 g / mol (hydroxyl value of 50.07 mgKOH / g) having the structure of formula (2) and 5 g of polyethylene glycol with a molecular weight of Mn = 2896 g / mol (hydroxyl value of 38.74 mgKOH / g) into a 250 mL round-bottom flask, and evacuate and remove water at 120 °C for 2 h. The raw material is cooled to 90 °C under a nitrogen atmosphere, and 4.00 g of dicyclohexylmethane diisocyanate, 0.0360 g of stannous octoate as a catalyst, and 7.00 g of molten polyethylene glycol are slowly added dropwise. During the reaction process, the temperature is gradually increased according to the polymer viscosity, and the mixture is stirred and reacted at a stirring speed of 300 r / min for 6 h. Pour it into a mold and cool. The obtained polyurethane has two glass transition temperatures, T g = -51.6 °C, 28.2 °C, and the mass percentage of each component is: polycarbonate diol 55.5%, polyethylene glycol 33.4%, dicyclohexylmethane diisocyanate 11.0%, stannous octoate 0.1%.

[0035] (2) Prepare the pressure-sensitive adhesive strips according to the method of Example 1 and conduct the initial adhesion (GB / T 31125-2014) and 180° peel test (GB / T 2792-2014) respectively according to the national standard. The initial adhesion of the obtained polyurethane hot-melt pressure-sensitive adhesive is 8.12 N, and the 180° peel strength is 7.64 N / 25 mm. Example 5:

[0036] (1) Add 20 g of polycarbonate diol with a molecular weight of Mn = 2241 g / mol (hydroxyl value of 50.07 mgKOH / g) and 5 g of polypropylene glycol with a molecular weight of Mn = 2239 g / mol (hydroxyl value of 50.12 mgKOH / g) having the structure shown in formula (2) to a 250 mL round-bottom flask and evacuate water at 120 °C for 2 h. The raw materials are cooled to 90 °C under a nitrogen atmosphere, and 2.82 g of hexamethylene diisocyanate, 0.0348 g of catalyst stannous octoate, and 7.00 g of polypropylene glycol are slowly added dropwise. During the reaction process, the temperature is gradually increased according to the polymer viscosity, and the mixture is stirred and reacted at a stirring speed of 300 r / min for 6 h. Pour into a mold and cool. The obtained polyurethane has two glass transition temperatures, T g = -58.1 °C, 32.5 °C, and the mass ratio of each component is: polycarbonate diol 57.4%, polypropylene glycol 34.4%, hexamethylene diisocyanate 8.1%, stannous octoate 0.1%.

[0037] (2) Prepare the pressure-sensitive adhesive strips according to the method of Example 1 and conduct the initial adhesion (GB / T 31125-2014) and 180° peel test (GB / T 2792-2014) respectively according to the national standard. The initial adhesion of the obtained polyurethane hot-melt pressure-sensitive adhesive is 10.39 N, and the 180° peel strength is 8.96 N / 25 mm. Example 6:

[0038] (1) Add 20 g of polycarbonate diol with a molecular weight of Mn = 2241 g / mol (hydroxyl value of 50.07 mgKOH / g) and 5 g of polypropylene glycol with a molecular weight of Mn = 2239 g / mol (hydroxyl value of 50.12 mgKOH / g) having the structure shown in formula (2) to a 250 mL round-bottom flask and evacuate water at 120 °C for 2 h. The raw materials are cooled to 90 °C under a nitrogen atmosphere, and 4.50 g of dicyclohexylmethane diisocyanate, 0.0364 g of catalyst stannous octoate, and 7.00 g of polypropylene glycol are slowly added dropwise. During the reaction process, the temperature is gradually increased according to the polymer viscosity, and 0.32 g of chain extender 1,4-butanediol is slowly added dropwise. The mixture is stirred and reacted at a stirring speed of 300 r / min for 6 h. Pour into a mold and cool. The obtained polyurethane has two glass transition temperatures, T g= -53.1 °C, 20.2 °C, and the mass percentages of each component are: polycarbonate diol 54.9%, polypropylene glycol 33.0%, dicyclohexylmethane diisocyanate 11.1%, 1,4-butanediol 0.9%, and stannous octoate 0.1%.

[0039] (2)Prepare the pressure-sensitive adhesive strips according to the method of Example 1 and conduct the initial tack (GB / T 31125-2014) and 180° peel test (GB / T 2792-2014) according to the national standard. The initial tack of the obtained polyurethane hot melt pressure-sensitive adhesive is 2.62 N, and the 180° peel strength is 3.01 N / 25 mm.

[0040] Comparative Example 1:

[0041] Add 20 g of polycarbonate diol with a molecular weight of Mn = 2241 kg / mol (hydroxyl value of 50.07 mgKOH / g) having the structure of formula (2) to a 250 mL round-bottom flask and evacuate water at 120 °C for 2 h. The raw materials are cooled to 90 °C under a nitrogen atmosphere, and 8.16 g of dicyclohexylmethane diisocyanate and 0.0235 g of the catalyst stannous octoate are slowly added dropwise, and the mixture is stirred and reacted at a stirring speed of 300 r / min for 3 h. Then, 0.26 g of the chain extender 1,4-butanediol is slowly added dropwise and reacted for 3 h. Pour it into a mold and cool. The glass transition temperature T of the obtained polyurethane g = 39.8 °C, and the mass percentages of each component are: polycarbonate diol 84.9%, polypropylene glycol 0%, dicyclohexylmethane diisocyanate 13.9%, 1,4-butanediol 1.1%, and stannous octoate 0.1%.

[0042] Comparative Example 2:

[0043] Add 20 g of polypropylene glycol with a molecular weight of Mn = 2239 g / mol (hydroxyl value of 50.12 mgKOH / g) to a 250 mL round-bottom flask and evacuate water at 120 °C for 2 h. The raw materials are cooled to 90 °C under a nitrogen atmosphere, and 3.27 g of dicyclohexylmethane diisocyanate and 0.0235 g of the catalyst stannous octoate are slowly added dropwise, and the mixture is stirred and reacted at a stirring speed of 300 r / min for 3 h. Then, 0.26 g of the chain extender 1,4-butanediol is slowly added dropwise and reacted for 3 h. Pour it into a mold and cool. The glass transition temperature T of the obtained polyurethane g = -53.7 °C, and the mass percentages of each component are: polycarbonate diol 0%, polypropylene glycol 84.9%, dicyclohexylmethane diisocyanate 13.9%, 1,4-butanediol 1.1%, and stannous octoate 0.1%.

[0044] Comparative Example 3:

[0045] The commercially available Deli 30170 tape has a main component of water-based polyacrylate, is non-degradable, has an unpleasant smell during use, an initial adhesion of 4.54 N, and a 180° peel strength of 5.35 N / 25mm.

[0046] Through the above examples, by adjusting the ratio and types of polycarbonate diol and polyether diol, the initial adhesion and peel strength of the hot melt pressure-sensitive adhesive can be effectively controlled, so as to meet the application requirements in different fields. The comparison of the bonding test results is shown in Table 1.

[0047]

Claims

1. A fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive, whose chemical structural formula is shown in Formula (1), where m≥1, n≥1, y≥1, z≥1; m, n, y, z are all integers; R1 is the side chain of an epoxy monomer, R2 is an aliphatic hydrocarbon group with 2 to 6 carbon atoms, R3 is the main chain of a polyether diol, R4 is the main chain of a diisocyanate; X is -NH- group or -O- group; The preparation method comprises the following steps: (1) Heat and dry the polycarbonate diol and the polyether diol under vacuum conditions. The drying temperature is 100~120 °C, and the drying time is 1~3 h; (2) Cool down under nitrogen protection, dropwise add a mixture of diisocyanate, catalyst and polyether diol and stir. During the reaction process, gradually increase the temperature according to the viscosity of the polymer. The stirring rate is 300~400 r / min, the reaction temperature is 60~120 °C, and the reaction time is 3~12 h to obtain a fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive; The mass percentages of each component are: polycarbonate diol 40~57.4%, polyether diol 33~50%, diisocyanate 8~20%, catalyst 0.05~0.5%; The chemical structural formula of the polycarbonate diol is shown in Formula (2), wherein, m≥1, n≥1, m and n are both integers; R1 is the side chain of an epoxy monomer, R2 is an aliphatic hydrocarbon group with 2 to 6 carbon atoms, the number average molecular weight is 600~6000 g / mol, and the polycarbonate content ≥95%; 。 2. The fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive according to claim 1, wherein The polyether diol is one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran diol.

3. The fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive according to claim 1, characterized in that, The diisocyanate is one or more of di-aliphatic diisocyanates, cycloaliphatic diisocyanates, or aromatic diisocyanates.

4. The fully biodegradable polycarbonate-based polyurethane hot melt pressure-sensitive adhesive according to claim 1, wherein The catalyst is one or more of stannous octoate, dibutyltin dilaurate, stannous oleate, tetrabutylammonium chloride, triethylamine, triethylenediamine, pentamethyldiethylenetriamine, and triethanolamine.

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