Difficult-to-adhere rubber base material primer and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, in particular to a hard-to-adhere rubber base material primer and a preparation method thereof. The glue synthesized by the invention belongs to a polyurethane prepolymer, and the bonding strength of the glue to various rubber substrates difficult to bond can be obviously improved. The formula of the polyurethane prepolymer comprises four polyester polyols, a curing agent and a chain extender. The primer prepared by the invention is matched with a polyurethane glue film for use, the gluing process is simple, convenient and rapid, and the bonding strength of the polyurethane glue film to fluororubber, ethylene propylene diene monomer (EPDM), synthetic rubber (TPE), thermoplastic rubber (TPR) and other base materials can be improved. The single-component primer has the advantages that the storage stability is good, the solvent is low in odor and easy to volatilize, the single-component primer can be quickly dried after being aired for about 10 minutes in a normal-temperature environment, the single-component primer does not contain toxic solvents such as benzene, the solid content is low, and the single-component primer can be used as a primer adhesion promoter of a rubber material difficult to adhere, and the bonding strength of a rubber base material can be obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, in particular to a primer for difficult-to-bond rubber substrates and a preparation method thereof. Background Art

[0002] In the production of wearable electronic consumer products, adhesives or films are required to bond the various modules of the wearable electronic device to the wearable electronic substrate. Traditional polyurethane adhesives require a long curing period after application to achieve the desired bond strength, which affects the production and assembly efficiency of wearable electronic products.

[0003] Polyurethane film is gaining increasing popularity in consumer electronics due to its ease of use, ability to quickly achieve high bond strength, excellent shock and drop resistance, and excellent resistance to aging and chemical corrosion. As consumer electronics become increasingly lightweight and compact, production demands for efficiency and quality continue to rise. While the bondable area of ​​adhesives used in electronic products continues to decrease, the demand for performance properties such as bonding strength in wearable electronics continues to increase.

[0004] To meet the higher bonding strength requirements for electronic wearable product assembly, a one-component primer is needed to reinforce the polyurethane adhesive films used to bond consumer electronics. Publication No. CN111849397B discloses a hot melt adhesive for difficult-to-bond substrates and its preparation method. The hot melt adhesive for difficult-to-bond substrates is prepared from the following components, calculated by weight: 10-30 parts naphthenic oil, 10-30 parts styrene elastomer, 7-20 parts solution-polymerized styrene-butadiene rubber, 3-20 parts polyolefin elastomer, 15-70 parts tackifying resin, 0.35-3 parts antioxidant, and 0.2-1 part UV absorber.

[0005] The hot melt adhesive prepared by the invention can well bond difficult-to-bond substrates to meet the bonding requirements of different difficult-to-bond fabrics.

[0006] However, for electronic wearable products, this invention cannot be adapted to the difficult-to-bond rubber substrates. Therefore, it is urgent to develop another adhesive to make its bonding strength to difficult-to-bond rubber materials higher, so as to effectively avoid the debonding between the substrates of electronic wearable consumer products, thereby improving the yield of electronic consumer products.

[0007] In order to solve the above problems, the present invention provides a primer for difficult-to-bond rubber materials and a preparation method thereof. Summary of the Invention

[0008] The object of the present invention is to provide a primer for difficult-to-bond rubber substrates and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0009] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0010] A primer for difficult-to-bond rubber substrates, comprising the following components by weight:

[0011]

[0012] More optimally, polyester polyols one to three are various combinations of XCP-1024, WSP-1000E, XCP-1000H, YTP-24-LA, 4030-TA, WSP-2000EBT-L2, XCP-2000H, WSP-3000E, WSP-3000EBT, XCP-3000H, WSP-4000E, and WSP-4000EBT.

[0013] More optimally, the polyether polyol tetrak is at least one of DE1000, DE2000, DP3000, DP4000, and DP4000E.

[0014] More optimally, the curing agent is at least one of the aromatic isocyanate curing agent toluene diisocyanate TDI, diphenylmethane diisocyanate MDI, diphenylmethane diisocyanate isomer MDI-50, aliphatic isocyanate curing agent hexamethylene diisocyanate HDI derivatives and polymers, and alicyclic isocyanate curing agent isophorone diisocyanate IPDI.

[0015] More optimally, the chain extender is at least one of the polyol chain extenders 1,4-butanediol, ethylene glycol, propylene glycol, neopentyl glycol, glycerol, and trimethylolpropane.

[0016] The present invention also provides a method for preparing a primer for a difficult-to-bond rubber substrate, which is used to prepare any of the above-mentioned primers for a difficult-to-bond rubber substrate, comprising the following steps:

[0017] S1, adding a certain amount of polyester polyol 1, polyester polyol 2, polyester polyol 3, and polyether polyol 4 into a dry four-necked reaction flask equipped with a vacuum device, a thermometer, and a separatory funnel, slowly heating to 120°C and stirring at a speed of 200 r / min to evacuate;

[0018] S2, the molten resin was stirred at 120°C at a speed of 200 r / min and vacuumed for 2 hours to remove moisture from the resin; the vacuum degree was maintained at -0.1 MPa;

[0019] S3, cooling the resin to 65°C, stirring and evacuating at a speed of 200 r / min, and maintaining the vacuum degree at -0.1 MPa;

[0020] S4, melt a predetermined amount of curing agent in an oven at 50°C, add the mixture to a separatory funnel, and then add the mixture dropwise to a four-necked reaction flask over 10 minutes. Stir and evacuate the mixture at a speed of 200 r / min. After the temperature of the reaction flask has fallen back from its highest point, adjust the temperature to 80°C and allow the reaction to proceed for 4 hours. Stir and evacuate the mixture over the entire reaction process at a speed of 200 r / min, maintaining a vacuum degree of -0.1 MPa.

[0021] S5, adding a quantitative chain extender to the separatory funnel and completing the addition dropwise within 30 minutes, and continuing the reaction at 80°C for 2 hours; during the entire reaction process, stirring at a speed of 200 r / min while evacuating the mixture, and the vacuum degree was maintained at -0.1 MPa;

[0022] In step S6, the reaction temperature is raised to 90°C and maintained at this temperature for 2 hours. Vacuum is applied at a rate of 200 r / min while stirring, and the vacuum is maintained at -0.1 MPa. The material is cooled and discharged to prepare a polyurethane prepolymer. Nitrogen is maintained throughout the reaction.

[0023] More optimally, the stirring rate in steps S1-S6 is 200 r / min.

[0024] More optimally, in steps S1-S6, nitrogen is passed through the entire reaction process for protection.

[0025] More optimally, in steps S1-S6, vacuum is applied while stirring during the entire reaction process, and the vacuum degree is maintained at -0.1 MPa.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention aims to propose a preparation method for a primer for difficult-to-bond rubber materials. The synthesized primer is a polyurethane prepolymer, which can achieve higher bonding strength performance within the increasingly smaller bonding area of ​​electronic wearable products.

[0028] (2) The polyurethane prepolymer prepared in the present invention is specifically designed for preparing a primer for difficult-to-bond rubbers. When used in conjunction with this primer, the polyurethane adhesive film can significantly improve the bonding strength to various difficult-to-bond rubber substrates. For PU leather and fluororubber substrates, the peel strength can reach 39.99 N / inch, increasing the bonding strength by at least 1.6 times. The polyurethane prepolymer formulation in the present invention is simple and the synthesis process is universal.

[0029] (3) In the present invention, this primer is used in conjunction with a polyurethane glue film. The sizing process is simple and quick, and can improve the bonding strength of the polyurethane glue film to substrates such as fluororubber, EPDM, TPE, and TPR. This one-component primer has good storage stability, low solvent odor, and is easily volatile. It dries after being left to air for about 10 minutes at room temperature. It does not contain toxic solvents such as benzene and has a low solid content. As a primer adhesion promoter for difficult-to-bond rubber materials, it can significantly improve the bonding strength of rubber substrates and prevent debonding between substrates of electronic wearable consumer products. DETAILED DESCRIPTION

[0030] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] The present invention first synthesizes a polyurethane prepolymer, and then dissolves the synthesized polyurethane prepolymer in a solvent containing a coupling agent in a certain proportion to prepare a primer for difficult-to-bond rubber materials. The specific method and formulation of synthesizing the polyurethane prepolymer in each embodiment are as follows.

[0032] Example 1

[0033] 50 parts of XCP-1024 polyester polyol 1, 100 parts of YTP-24-LA polyester polyol 2, 90 parts of WSP-3000E polyester polyol 3, and 50 parts of DE1000 polyether polyol were added to a dry four-necked reaction flask equipped with a vacuum pump, a thermometer, and a separatory funnel. The mixture was slowly heated to 120°C and vacuumed at a speed of 200 r / min. The molten resin was stirred at 120°C and vacuumed at a speed of 200 r / min for 2 hours to remove moisture from the resin.

[0034] The resin was then cooled to 65°C and vacuumed at a speed of 200 r / min while stirring, and the vacuum degree was maintained at -0.1 MPa during vacuuming; 50 parts of diphenylmethane diisocyanate (MDI) were melted in a 50°C oven, added to a separatory funnel, and dropwise added to a four-necked reaction flask over 10 minutes, and vacuumed at a speed of 200 r / min. After the temperature of the reaction flask dropped from the highest temperature, the temperature was adjusted to 80°C and reacted for 4 hours; 5 parts of 1,4-butanediol were added to the separatory funnel and added dropwise within 30 minutes, and the reaction was continued at 80°C for 2 hours; the reaction temperature was raised to 90°C and kept for reaction for 2 hours.

[0035] The reaction was carried out at a speed of 200 r / min while stirring and evacuating the mixture. The vacuum was maintained at -0.1 MPa. Nitrogen was used for protection during the entire reaction.

[0036] The polyurethane prepolymer is prepared by cooling and discharging the material.

[0037] Example 2

[0038] 50 parts of XCP-1024 polyester polyol 1, 100 parts of 4030-TA polyester polyol 2, 90 parts of WSP-3000EBT polyester polyol 3, and 50 parts of DE1000 polyether polyol were added to a dry four-necked reaction flask equipped with a vacuum pump, a thermometer, and a separatory funnel. The mixture was slowly heated to 120°C and vacuumed at a speed of 200 r / min. The molten resin was stirred at 120°C and vacuumed at a speed of 200 r / min for 2 hours to remove moisture from the resin.

[0039] The resin was then cooled to 65°C and vacuumed at a speed of 200 r / min while stirring, and the vacuum degree was maintained at -0.1 MPa during vacuuming; 50 parts of diphenylmethane diisocyanate (MDI) were melted in a 50°C oven, added to a separatory funnel, and dropwise added to a four-necked reaction flask over 10 minutes, and vacuumed at a speed of 200 r / min. After the temperature of the reaction flask dropped from the highest temperature, the temperature was adjusted to 80°C and reacted for 4 hours; 5 parts of 1,4-butanediol were added to the separatory funnel and added dropwise within 30 minutes, and the reaction was continued at 80°C for 2 hours; the reaction temperature was raised to 90°C and kept for reaction for 2 hours.

[0040] The reaction was carried out at a speed of 200 r / min while stirring and evacuating the mixture. The vacuum was maintained at -0.1 MPa. Nitrogen was used for protection during the entire reaction.

[0041] The polyurethane prepolymer is prepared by cooling and discharging the material.

[0042] Example 3

[0043] 50 parts of WSP-1000E polyester polyol 1, 100 parts of 4030-TA polyester polyol 2, 90 parts of WSP-3000E polyester polyol 3, and 50 parts of DE1000 polyether polyol were added to a dry four-necked reaction flask equipped with a vacuum pump, a thermometer, and a separatory funnel. The mixture was slowly heated to 120°C and vacuumed at a speed of 200 r / min. The molten resin was stirred at 120°C and vacuumed at a speed of 200 r / min for 2 hours to remove moisture from the resin.

[0044] The resin was then cooled to 65°C and vacuumed at a speed of 200 r / min while stirring, and the vacuum degree was maintained at -0.1 MPa during vacuuming; 50 parts of diphenylmethane diisocyanate (MDI) were melted in a 50°C oven, added to a separatory funnel, and dropwise added to a four-necked reaction flask over 10 minutes, and vacuumed at a speed of 200 r / min. After the temperature of the reaction flask dropped from the highest temperature, the temperature was adjusted to 80°C and reacted for 4 hours; 5 parts of trimethylolpropane were added to the separatory funnel and added dropwise within 30 minutes, and the reaction was continued at 80°C for 2 hours; the reaction temperature was raised to 90°C and kept for reaction for 2 hours.

[0045] The reaction was carried out at a speed of 200 r / min while stirring and evacuating the mixture. The vacuum was maintained at -0.1 MPa. Nitrogen was used for protection during the entire reaction.

[0046] The polyurethane prepolymer is prepared by cooling and discharging the material.

[0047] Example 4

[0048] 50 parts of XCP-1000H polyester polyol 1, 100 parts of XCP-2000H polyester polyol 2, 90 parts of WSP-3000E polyester polyol 3, and 50 parts of DE1000 polyether polyol were added to a dry four-necked reaction flask equipped with a vacuum pump, a thermometer, and a separatory funnel. The mixture was slowly heated to 120°C and vacuumed at a speed of 200 r / min. The molten resin was stirred at 120°C and vacuumed at a speed of 200 r / min for 2 hours to remove moisture from the resin.

[0049] The resin was cooled to 65°C and vacuumed at a speed of 200 r / min while stirring, and the vacuum degree was maintained at -0.1 MPa during vacuuming; 50 parts of diphenylmethane diisocyanate MDI-50 were melted in a 50°C oven, added to a separatory funnel, and dropwise added to a four-necked reaction flask over 10 minutes, and vacuumed at a speed of 200 r / min. After the temperature of the reaction flask fell back from the highest temperature, the temperature was adjusted to 80°C and reacted for 4 hours; 5 parts of trimethylolpropane were added to the separatory funnel and added dropwise within 30 minutes, and the reaction was continued at 80°C for 2 hours; the reaction temperature was raised to 90°C and kept for reaction for 2 hours.

[0050] The reaction was carried out at a speed of 200 r / min while stirring and evacuating the mixture. The vacuum was maintained at -0.1 MPa. Nitrogen was used for protection during the entire reaction.

[0051] The polyurethane prepolymer is prepared by cooling and discharging the material.

[0052] Example 5

[0053] 50 parts of WSP-1000E polyester polyol 1, 100 parts of WSP-2000EBT-L2 polyester polyol 2, 90 parts of XCP-3000H polyester polyol 3 and 50 parts of DE1000 polyether polyol were added into a dry four-necked reaction flask equipped with a vacuum pump, a thermometer and a separatory funnel, and slowly heated to 120°C and stirred at a speed of 200 r / min to evacuate; the molten resin was stirred at 120°C at a speed of 200 r / min and evacuated for 2 hours to remove moisture from the resin; the resin was cooled to 65°C and stirred at 200 r / min. r / min while stirring and evacuating, and the vacuum degree is maintained at -0.1MPa during evacuation; 50 parts of diphenylmethane diisocyanate MDI are melted in a 50°C oven, added to a separatory funnel, and then dropwise added to a four-necked reaction flask over 10 minutes, and then stirred and evacuated at a speed of 200r / min. After the temperature of the reaction flask has fallen back from the highest temperature, the temperature is adjusted to 80°C and reacted for 4 hours; 5 parts of 1,4-butanediol are added to the separatory funnel and added dropwise over 30 minutes, and the reaction is continued at 80°C for 2 hours; the reaction temperature is raised to 90°C and kept for reaction for 2 hours.

[0054] The reaction was carried out at a speed of 200 r / min while stirring and evacuating the mixture. The vacuum was maintained at -0.1 MPa. Nitrogen was used for protection during the entire reaction.

[0055] The polyurethane prepolymer is prepared by cooling and discharging the material.

[0056] Primer preparation

[0057] After the polyurethane prepolymer is prepared, a primer for difficult-to-bond rubber materials is prepared according to the ratio of 8 parts coupling agent to 20 parts solvent (10 parts ethyl acetate and 10 parts butanone solvent):

[0058] The polyurethane prepolymers synthesized in Examples 1-5 were tested for their solid content and molecular weight. A lower solid content results in faster drying, which can achieve a quick-drying effect. The molecular weight directly affects the adhesive strength, cohesive strength, and mechanical properties of the glue.

[0059] The specific solids content test method is to weigh W1g (approximately 1g) of polyurethane prepolymer using an electronic balance with a precision of 0.1%, place it in a W2g aluminum foil dish, bake it in a 120°C oven for 2 hours, remove the aluminum foil dish containing the prepolymer, and weigh W3. The specific solids content = (W3 - W2) / W1 * 100%.

[0060] The molecular weight of the polyurethane prepolymer was tested by gel chromatography permeameter, with polystyrene as the standard sample and tetrahydrofuran as the mobile phase. The number average relative molecular weight of the synthesized polyurethane prepolymers 1-5 was measured to be between 700,000 and 1,500,000. The primers with molecular weights within this range have greater bonding strength and better mechanical properties.

[0061] The polyurethane prepolymers synthesized in Examples 1-5 were dissolved in ethyl acetate and butanone solvents containing a coupling agent at a ratio of 8% to 12% by weight to prepare a primer for difficult-to-bond rubber materials.

[0062] After the finished primer was prepared, a peel strength test was performed. The specific method was as follows: the primer was applied to the target substrate, then bonded to the target substrate with a standard polyurethane film to form a test sample. The T-type peel test was then performed. The peel strength of the prepared sample was measured according to the GB / T2790 test method for adhesive tape peel strength. The peel strength test was performed using an Instron mechanical testing machine at 25±2°C and a speed of 300 mm / min. The performance test results are shown in Table 1.

[0063] The physical properties of the primers obtained in the examples were tested, and the test results are shown in Table 2.

[0064] Table 1 Peel strength performance of substrates after treatment with primers prepared in various examples (unit: N / inch)

[0065] Substrate / peel strength Example 1 Example 2 Example 3 Example 4 Example 5 No primer added PU leather / fluororubber 38.19 38.78 39.66 39.06 39.99 18.67 PU leather / EPDM 25.09 24.78 26.77 24.89 25.18 15.86 PU leather / TPE 30.78 31.80 30.82 29.85 29.97 17.73 PU leather / TPR 29.90 29.74 29.10 28.89 30.29 16.87

[0066] The experimental results in Table 1 indicate that treatment with the polyurethane one-component primer of the present invention increases the bonding strength of the polyurethane film to substrates such as fluororubber, EPDM, TPE, and TPR by at least 1.6 times, significantly improving bonding performance. This significant improvement in bonding strength between the polyurethane film and substrates such as fluororubber, EPDM, TPE, and TPR can significantly increase the yield of the film during product application.

[0067] The primer for difficult-to-bond rubber materials disclosed by the invention has the advantages of simple preparation process, good storage stability of components, simple sizing process, use of environmentally friendly solvents, and the like.

[0068] Table 2 Physical properties of primers prepared in various embodiments

[0069] Primer type Example 1 Example 2 Example 3 Example 4 Example 5 Solid content (%) 8 8 8 8 8 Surface drying time (min) 5-10 5-10 5-10 5-10 5-10 Opening time (50℃) 3D stabilization 3D stabilization 3D stabilization 3D stabilization 3D stabilization Storage stability 6 months 6 months 6 months 6 months 6 months

[0070] The data in Table 2 indicate that the primer for difficult-to-bond rubber materials prepared by the present invention has a low solids content, is easy to dry, and can significantly reduce production costs. Furthermore, the primer can be applied by spraying or hand coating, making the sizing process flexible and simple.

[0071] The above descriptions are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by utilizing the contents of the present invention specification under the inventive concept of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A primer for hard-to-bond rubber substrates, characterized in that: Contains the following components by weight:

2. The primer for hard-to-bond rubber substrates according to claim 1, characterized in that: The polyester polyols one to three are various combinations of XCP-1024, WSP-1000E, XCP-1000H, YTP-24-LA, 4030-TA, WSP-2000EBT-L2, XCP-2000H, WSP-3000E, WSP-3000EBT, XCP-3000H, WSP-4000E, and WSP-4000EBT.

3. The primer for difficult-to-bond rubber substrates according to claim 1, characterized in that: The polyether polyol tetrak is at least one of DE1000, DE2000, DP3000, DP4000, and DP4000E.

4. The primer for difficult-to-bond rubber substrates according to claim 1, characterized in that: The curing agent is at least one of aromatic isocyanate curing agent toluene diisocyanate TDI, diphenylmethane diisocyanate MDI, diphenylmethane diisocyanate isomer MDI-50, aliphatic isocyanate curing agent hexamethylene diisocyanate HDI derivatives and polymers, and alicyclic isocyanate curing agent isophorone diisocyanate IPDI.

5. The primer for difficult-to-bond rubber substrate according to claim 1, characterized in that: The chain extender is at least one of the polyol chain extenders 1,4-butanediol, ethylene glycol, propylene glycol, neopentyl glycol, glycerol, and trimethylolpropane.

6. A method for preparing a primer for difficult-to-bond rubber substrates, characterized in that: The method for preparing a primer for a difficult-to-bond rubber substrate according to any one of claims 1 to 5 comprises the following steps: S1, adding a certain amount of polyester polyol 1, polyester polyol 2, polyester polyol 3, and polyether polyol 4 into a dry four-necked reaction flask equipped with a vacuum device, a thermometer, and a separatory funnel, slowly heating to 120°C and stirring at a speed of 200 r / min to evacuate; S2, the molten resin was stirred at 120°C at a speed of 200 r / min and vacuumed for 2 hours to remove moisture from the resin; the vacuum degree was maintained at -0.1 MPa; S3, cooling the resin to 65°C, stirring and evacuating at a speed of 200 r / min, and maintaining the vacuum degree at -0.1 MPa; S4, melt a predetermined amount of curing agent in an oven at 50°C, add the mixture to a separatory funnel, and then add the mixture dropwise to a four-necked reaction flask over 10 minutes. Stir and evacuate the mixture at a speed of 200 r / min. After the temperature of the reaction flask has fallen back from its highest point, adjust the temperature to 80°C and allow the reaction to proceed for 4 hours. Stir and evacuate the mixture over the entire reaction process at a speed of 200 r / min, maintaining a vacuum degree of -0.1 MPa. S5, adding a quantitative chain extender to the separatory funnel and completing the addition dropwise within 30 minutes, and continuing the reaction at 80°C for 2 hours; during the entire reaction process, stirring at a speed of 200 r / min while evacuating the mixture, and the vacuum degree was maintained at -0.1 MPa; S6, raising the reaction temperature to 90°C and keeping the temperature for 2 hours. During the entire reaction process, stirring and vacuuming were carried out at a speed of 200 r / min, and the vacuum degree was maintained at -0.1 MPa; cooling and discharging the material to prepare a polyurethane prepolymer. Nitrogen protection was required during the entire reaction process.

7. The method for preparing a primer for difficult-to-bond rubber substrates according to claim 6, characterized in that: The stirring rate in steps S1-S6 is 200 r / min.

8. The method for preparing a primer for difficult-to-bond rubber substrates according to claim 6, characterized in that: In the steps S1-S6, nitrogen is passed through the entire reaction process for protection.

9. The method for preparing a primer for difficult-to-bond rubber substrates according to claim 6, characterized in that: In the steps S1-S6, the mixture is stirred and vacuumed during the entire reaction process, and the vacuum degree is maintained at -0.1 MPa.

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