Polyurethane elastic rubber and preparation method thereof

Abstract

The invention discloses a polyurethane elastic adhesive in the technical field of high polymer materials, which is prepared from the following raw materials in parts by weight: 60 to 80 parts of polyurethane prepolymer, 5 to 15 parts of chain extender, 10 to 30 parts of reflective microbead, 1 to 5 parts of coupling agent, 0.1 to 1 part of catalyst and 60 parts of solvent, the polyurethane prepolymer comprises a polyurethane prepolymer A: PT-1577, a polyurethane prepolymer B: PE-33M and a polyurethane prepolymer C: PE-5537, and the ratio of the polyurethane prepolymer A: the polyurethane prepolymer B: the polyurethane C is 5: 4: 1, or the ratio of the polyurethane prepolymer A: the polyurethane prepolymer B: the polyurethane C is 5: 5: 0, or the ratio of the polyurethane prepolymer A: the polyurethane prepolymer B: the polyurethane C is 5: 3: 2; according to the invention, by adjusting the proportion of each soft and hard block copolymer, the relatively excellent weather resistance can be maintained, and the water washing is not easy to hydrolyze and separate.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a polyurethane elastic adhesive and a preparation method thereof. Background Art

[0002] Polyurethane is a type of block copolymer with polyol (polyether or polyester polyol) as soft segment and polyisocyanate and small molecule chain extender as hard segment. Due to the unique structure, polyurethane has excellent low temperature resistance, shear strength and impact resistance. At the same time, the polyurethane molecular chain contains more polar groups, so polyurethane is widely used in the field of pressure-sensitive adhesives.

[0003] In the touch field, various protective films are used in the TP process (touch screen manufacturing process) and the shipping process, and various types of pressure-sensitive adhesives are required for the protective films. PU adhesive protective films based on polyurethane pressure-sensitive adhesives are widely used in the process and shipping protection of the touch screen industry because of their excellent exhaust properties, good die-cutting properties and low pollution.

[0004] At present, the commonly used polyurethane pressure-sensitive adhesives are mainly polyether-polyester polyurethanes obtained by reacting polyether polyols, polyester polyols and polyisocyanates. The polyether main chain contains ether bonds and is easy to rotate. The polyurethane pressure-sensitive adhesive prepared from it has good flexibility, excellent low temperature resistance and water resistance, but is not as good as the polyester type in terms of strength, hardness, adhesion and thermal oxidation resistance. The polyester main chain contains polar group ester groups, which can not only form hydrogen bonds between the hard segments, but also the polar groups on the soft segments can form hydrogen bonds with the polar groups on the hard segments, playing the role of physical cross-linking points, so its mechanical properties are stronger than polyethers, which can make up for the shortcomings of polyethers. However, the ester group is easy to hydrolyze under high temperature and high humidity environments, so conventional polyether-polyester polyurethane pressure-sensitive adhesives are prone to whitening and fogging when used for protective films. In response to the above problems, CN201410821734.6 discloses a method for preparing a polyurethane adhesive for a protective film, using polycarbonate polyols instead of conventional polyester polyols to solve the problem of white fog due to the inability of polyurethane adhesives to resist hydrolysis. However, polycarbonate polyols are relatively hard, and the low-viscosity polyurethane pressure-sensitive adhesive prepared has the risk of powder falling off during die-cutting. At the same time, experiments have found that the polyurethane pressure-sensitive adhesive synthesized using polycarbonate polyols will have poor product crystallization fluidity at low temperatures, limiting its construction application under low temperature conditions. At the same time, the polyurethane pressure-sensitive adhesive used for touch protective films needs to not turn yellow after aging. The method disclosed in the above patent mentions the use of TDI and HTDI trimers as curing agents when preparing the protective film, which will cause the polyurethane pressure-sensitive adhesive to have the risk of yellowing. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] Therefore, the object of the present invention is to provide a polyurethane elastic adhesive and a preparation method thereof, which can achieve both relatively excellent weather resistance and the satisfaction of not being easily hydrolyzed and detached by water washing by adjusting the ratio of each soft and hard block copolymer.

[0007] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:

[0008] A polyurethane elastic adhesive is composed of the following raw materials in parts by weight: polyurethane prepolymer: 60-80 parts, chain extender: 5-15 parts, reflective microbeads: 10-30 parts, coupling agent: 1-5 parts, catalyst: 0.1-1 parts, solvent: 60 parts;

[0009] Among them, the polyurethane prepolymer includes polyurethane prepolymer A: PT-1577, polyurethane prepolymer B: PE-33M and polyurethane prepolymer C: PE-5537, and polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C = 5:4:1 or polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C = 5:5:0 or polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C = 5:3:2.

[0010] As a preferred embodiment of the polyurethane elastic adhesive described in the present invention, the polyurethane prepolymer is prepared by reacting polyester polyol or polyether polyol with polyisocyanate.

[0011] As a preferred embodiment of the polyurethane elastic adhesive described in the present invention, the chain extender is a diol or diamine compound.

[0012] As a preferred embodiment of the polyurethane elastic adhesive described in the present invention, the model of the reflective microbeads is KH-550, KH-560, or KH-602.

[0013] A method for preparing polyurethane elastic adhesive, the specific steps are as follows:

[0014] S1. Mix the chain extender, reflective microbeads, coupling agent and remaining solvent in a formula ratio to form a mixed solution, slowly add the polyurethane prepolymer to the mixed solution, stirring while adding to ensure that all raw materials are fully mixed, and control the stirring speed and time during the stirring process to avoid bubbles and lumps;

[0015] S2, placing the mixed materials in a reactor, and carrying out a polymerization reaction at a suitable temperature and pressure, closely monitoring the reaction temperature and pressure during the reaction to ensure that the reaction proceeds smoothly, and after the reaction is completed, treating the reactants by cooling and reducing pressure to make them reach a stable state;

[0016] S3, filtering the reacted material to remove impurities and particulate matter therein, placing the filtered material in a vacuum exhauster for vacuum defoaming treatment to remove bubbles therein and water vapor in the air;

[0017] S4. Pack the polyurethane elastic adhesive that has been vacuum defoamed into appropriate packaging containers and store them in a sealed manner. The storage environment should be kept cool, dry, and well ventilated, avoiding direct sunlight and high temperature.

[0018] As a preferred embodiment of the method for preparing a polyurethane elastic adhesive according to the present invention, the polyether polyol or polyester polyol is heated to a suitable temperature and dehydrated under vacuum or inert gas protection to remove moisture and impurities therein;

[0019] The dehydrated polyether polyol or polyester polyol is mixed with isocyanate in a certain proportion, a catalyst is added, and the reaction is carried out at a suitable temperature.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the present invention optimizes the tolerance to various chemicals such as acids, alkalis, solvents, etc., and maintains stable bonding performance. The polyurethane elastic adhesive can maintain its bonding performance under different climatic conditions, and can work stably in high temperature, low temperature or humid environment, and will not lose its bonding force due to climate change. In a series of subsequent tests, it also showed good performance in terms of tolerance to industrial detergents. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below in combination with the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0022] Figure 1 This is a flow chart of a method for preparing a polyurethane elastic adhesive according to the present invention;

[0023] Figure 2 This is a schematic diagram of the performance test of the polyurethane elastic adhesive in Examples 1-4 and Comparative Examples 1-2 provided by the present invention. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0025] Secondly, the present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] The invention provides a polyurethane elastic adhesive, which is composed of the following raw materials in parts by weight: 60-80 parts of polyurethane prepolymer, 5-15 parts of chain extender, 10-30 parts of reflective microbeads, 1-5 parts of coupling agent, 0.1-1 parts of catalyst, and 60 parts of solvent; wherein the polyurethane prepolymer includes polyurethane prepolymer A: PT-1577, polyurethane prepolymer B: PE-33M and polyurethane prepolymer C: PE-5537, and polyurethane prepolymer A: polyurethane prepolymer Polyurethane prepolymer B: polyurethane C = 5:4:1 or polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C = 5:5:0 or polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C = 5:3:2. In this embodiment, the polyurethane prepolymer is prepared by reacting polyester polyol or polyether polyol with polyisocyanate, the chain extender is a diol or a diamine compound, the catalyst is organic zinc-organic bismuth, and the model of the reflective microbeads is KH-550, KH-560, or KH-602.

[0028] In order to verify the performance of the polyurethane elastic adhesive of the present invention, the following Examples 1-3 and Comparative Examples 1-2 are provided.

[0029] Example 1

[0030] Add 10 parts of solvent to the split four-necked flask 1, and accurately weigh 60 parts of polyurethane prepolymer A, polyurethane prepolymer B, and polyurethane prepolymer C, wherein the ratio of the three is A:B:C=5:4:1, slowly heat up to 120°C and turn on the vacuum equipment, vacuum for 60 minutes (the time here can be determined by the temperature and humidity of the day), and the insulation time starts when the pressure reaches -0.1 Pa and the temperature reaches 120°C;

[0031] After the holding time is reached, the temperature is lowered to below 70°C, and then 5 parts of chain extender, 0.8 parts of catalyst, and 3 parts of coupling agent are added. During the addition process, the surrounding environment is kept dry and the humidity fluctuation should not be too large. After the addition is completed, the temperature is continued to rise to 80°C to start the reaction. During this period, the stirring rate is ensured to gradually increase with the change of viscosity to improve the reaction efficiency. During the reaction at 80°C for 3 hours, reflux will occur, and reflux cooling must be done well, and the temperature fluctuation must be within ±2°C;

[0032] After the reaction is completed, 50 parts of solvent are added and stirred evenly, and the temperature is lowered to below 60° C. and filtered through a 300-mesh nylon filter to obtain a finished polyurethane elastic adhesive.

[0033] Example 2

[0034] Add 10 parts of solvent to the split four-necked flask 1, and accurately weigh 60 parts of polyurethane prepolymer A, polyurethane prepolymer B, and polyurethane prepolymer C, the ratio of which is A:B:C=5:5:0, slowly heat up to 120°C and turn on the vacuum equipment, vacuum for 60 minutes (the time here can be determined by the temperature and humidity of the day) and the insulation time starts when the pressure reaches -0.1 Pa and the temperature reaches 120°C;

[0035] After the holding time is reached, the temperature is lowered to below 70°C, and then 5 parts of chain extender, 0.8 parts of catalyst, and 3 parts of coupling agent are added. During the addition process, the surrounding environment is kept dry and the humidity fluctuation should not be too large. After the addition is completed, the temperature is continued to rise to 80°C to start the reaction. During this period, the stirring rate is ensured to gradually increase with the change of viscosity to improve the reaction efficiency. During the reaction at 80°C for 3 hours, reflux will occur, and reflux cooling must be done well, and the temperature fluctuation must be within ±2°C;

[0036] After the reaction is completed, 50 parts of solvent are added and stirred evenly, and the temperature is lowered to below 60° C. and filtered through a 300-mesh nylon filter to obtain a finished polyurethane elastic adhesive.

[0037] Example 3

[0038] Add 10 parts of solvent to the split four-necked flask 1, and accurately weigh 60 parts of polyurethane prepolymer A, polyurethane prepolymer B, and polyurethane prepolymer C, wherein the ratio of the three is A:B:C=5:3:2, slowly heat up to 120°C and turn on the vacuum equipment, vacuum for 60 minutes (the time here can be determined by the temperature and humidity of the day), and the insulation time starts when the pressure reaches -0.1 Pa and the temperature reaches 120°C;

[0039] After the holding time is reached, the temperature is lowered to below 70°C, and then 5 parts of chain extender, 0.8 parts of catalyst, and 3 parts of coupling agent are added. During the addition process, the surrounding environment is kept dry and the humidity fluctuation should not be too large. After the addition is completed, the temperature is continued to rise to 80°C to start the reaction. During this period, the stirring rate is ensured to gradually increase with the change of viscosity to improve the reaction efficiency. During the reaction at 80°C for 3 hours, reflux will occur, and reflux cooling must be done well, and the temperature fluctuation must be within ±2°C;

[0040] After the reaction is completed, 50 parts of solvent are added and stirred evenly, and the temperature is lowered to below 60° C. and filtered through a 300-mesh nylon filter to obtain a finished polyurethane elastic adhesive.

[0041] Example 4

[0042] Add 10 parts of solvent to the split four-necked flask 1, and accurately weigh 60 parts of polyurethane prepolymer A, polyurethane prepolymer B, and polyurethane prepolymer C, wherein the ratio of the three is 1:1:1, and the cyanate ester is HTDI. Slowly heat to 120°C and turn on the vacuum equipment. Vacuum for 60 minutes (the time here can be determined by the temperature and humidity of the day). The insulation time starts when the pressure reaches -0.1 Pa and the temperature reaches 120°C;

[0043] After the holding time is reached, the temperature is lowered to below 70°C, and 5 parts of chain extender, 0.8 parts of catalyst, and 3 parts of coupling agent are added. During the addition process, the surrounding environment is kept dry and the humidity fluctuation should not be too large. After the addition is completed, the temperature is continued to rise to 80°C to start the reaction. During this period, the stirring rate is ensured to gradually increase with the change of viscosity to improve the reaction efficiency. During the reaction at 80°C for 3 hours, reflux will occur, and reflux cooling must be done well, and the temperature fluctuation must be within ±2°C;

[0044] After the reaction is completed, 50 parts of solvent are added and stirred evenly, and the temperature is lowered to below 60° C. and filtered through a 300-mesh nylon filter to obtain a finished polyurethane elastic adhesive.

[0045] Comparative Example 1

[0046] Add 10 parts of solvent to the split four-necked flask 1, and accurately weigh 60 parts of polyurethane prepolymer A, polyurethane prepolymer B, and polyurethane prepolymer C, wherein the ratio of the three is A:B:C=1:1:1, slowly heat up to 120°C and turn on the vacuum equipment, vacuum for 60 minutes (the time here can be determined by the temperature and humidity of the day), and the insulation time starts when the pressure reaches -0.1 Pa and the temperature reaches 120°C;

[0047] After the holding time is reached, the temperature is lowered to below 70°C, and then 5 parts of chain extender, 0.8 parts of catalyst, and 3 parts of coupling agent are added. During the addition process, the surrounding environment is kept dry and the humidity fluctuation should not be too large. After the addition is completed, the temperature is continued to rise to 80°C to start the reaction. During this period, the stirring rate is ensured to gradually increase with the change of viscosity to improve the reaction efficiency. During the reaction at 80°C for 3 hours, reflux will occur, and reflux cooling must be done well, and the temperature fluctuation must be within ±2°C;

[0048] After the reaction is completed, 50 parts of solvent are added and stirred evenly, and the temperature is lowered to below 60° C. and filtered through a 300-mesh nylon filter to obtain a finished polyurethane elastic adhesive.

[0049] Comparative Example 2

[0050] Add 10 parts of solvent to the split four-necked flask 1, and accurately weigh 60 parts of polyurethane prepolymer A, polyurethane prepolymer B, and polyurethane prepolymer C, wherein the ratio of the three is A:B:C=2:1:0, slowly heat up to 120°C and turn on the vacuum equipment, vacuum for 60 minutes (the time here can be determined by the temperature and humidity of the day), and the insulation time starts when the pressure reaches -0.1 Pa and the temperature reaches 120°C;

[0051] After the holding time is reached, the temperature is lowered to below 70°C, and then 5 parts of chain extender, 0.8 parts of catalyst, and 3 parts of coupling agent are added. During the addition process, the surrounding environment is kept dry and the humidity fluctuation should not be too large. After the addition is completed, the temperature is continued to rise to 80°C to start the reaction. During this period, the stirring rate is ensured to gradually increase with the change of viscosity to improve the reaction efficiency. During the reaction at 80°C for 3 hours, reflux will occur, and reflux cooling must be done well, and the temperature fluctuation must be within ±2°C;

[0052] After the reaction is completed, 50 parts of solvent are added and stirred evenly, and the temperature is lowered to below 60° C. and filtered through a 300-mesh nylon filter to obtain a finished polyurethane elastic adhesive.

[0053] Coating and performance testing of polyurethane elastic adhesive in Examples 1-4 and Comparative Examples 1-2:

[0054] The polyurethane elastic adhesive prepared in Example 1-4 was evenly coated on the release paper using a 60um thick wire rod, and the thickness of the final dry adhesive film was controlled to be 20-30um. It was placed in a blast oven at 80-100°C and dried for 90-120 seconds. After drying, it was transferred to a tissue paper substrate. After the coating was completed, it was placed in a 40°C oven for 24 hours to stabilize, and then the room temperature performance was tested.

[0055] GB / T 2792-2014 tests the 180° peel strength of pressure-sensitive adhesives.

[0056] The stickiness performance refers to method A in GB / T 4851-2014, and the sample is placed at room temperature and the drop time is recorded.

[0057] like Figure 2 As shown, by adjusting the proportions of polyurethane prepolymer A, polyurethane prepolymer B and polyurethane prepolymer C, polyurethane elastic adhesive samples with different peeling force performances can be obtained. There are different amounts of benzene ring structure content in the three polyurethane prepolymers, and the benzene ring structure has an impact on weather resistance and acid and alkali resistance. Therefore, by adjusting the proportion of polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C, the research and development purpose of the present invention is achieved, and the test data in Example 4 more show that HEDI has better anti-yellowing performance than TDI.

[0058] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A polyurethane elastic adhesive, characterized in that: The invention is composed of the following raw materials in parts by weight: polyurethane prepolymer: 60-80 parts, chain extender: 5-15 parts, reflective microbeads: 10-30 parts, coupling agent: 1-5 parts, catalyst: 0.1-1 parts, solvent: 60 parts; Among them, the polyurethane prepolymer includes polyurethane prepolymer A: PT-1577, polyurethane prepolymer B: PE-33M and polyurethane prepolymer C: PE-5537, and polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C = 5:4:1 or polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C = 5:5:0 or polyurethane prepolymer A: polyurethane prepolymer B: polyurethane C = 5:3:

2.

2. The polyurethane elastic adhesive according to claim 1, characterized in that: Polyurethane prepolymers are prepared by the reaction of polyester polyols or polyether polyols with polyisocyanates.

3. The polyurethane elastic adhesive according to claim 1, characterized in that: The chain extender is a diol or diamine compound.

4. The polyurethane elastic adhesive according to claim 1, characterized in that: The catalyst is organic zinc-organic bismuth.

5. The polyurethane elastic adhesive according to claim 1, characterized in that: The models of the reflective microbeads are KH-550, KH-560, and KH-602.

6. A method for preparing the polyurethane elastic adhesive according to any one of claims 1 to 5, characterized in that: The specific steps are as follows: S1. Mix the chain extender, reflective microbeads, coupling agent and remaining solvent in a formula ratio to form a mixed solution, slowly add the polyurethane prepolymer to the mixed solution, stirring while adding to ensure that all raw materials are fully mixed, and control the stirring speed and time during the stirring process to avoid bubbles and lumps; S2, placing the mixed materials in a reactor, and carrying out a polymerization reaction at a suitable temperature and pressure, closely monitoring the reaction temperature and pressure during the reaction to ensure that the reaction proceeds smoothly, and after the reaction is completed, treating the reactants by cooling and reducing pressure to make them reach a stable state; S3, filtering the reacted material to remove impurities and particulate matter therein, placing the filtered material in a vacuum exhauster for vacuum defoaming treatment to remove bubbles therein and water vapor in the air; S4. Pack the polyurethane elastic adhesive that has been vacuum defoamed into appropriate packaging containers and store them in a sealed manner. The storage environment should be kept cool, dry, and well ventilated, avoiding direct sunlight and high temperature.

7. The method for preparing the polyurethane elastic adhesive according to claim 6, characterized in that: The polyether polyol or polyester polyol is heated to a suitable temperature, and dehydrated under vacuum or inert gas protection to remove moisture and impurities therein; The dehydrated polyether polyol or polyester polyol is mixed with isocyanate in a certain proportion, a catalyst is added, and the reaction is carried out at a suitable temperature.

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