Polyurethane composite adhesive for waterproof abrasive paper and preparation method of polyurethane composite adhesive

Abstract

The invention relates to the technical field of adhesive synthesis, in particular to polyurethane composite adhesive for waterproof abrasive paper and a preparation method of the polyurethane composite adhesive. Wherein the main agent comprises macromolecular phthalic anhydride type polyester polyol, micromolecular phthalic anhydride type polyester polyol, a chain extender, diisocyanate, ethyl acetate (EAC) and dimethyl carbonate (DMC), and the phthalic anhydride type polyester polyol is selected to synthesize polyurethane, so that the heat resistance and the wear resistance of the product can be remarkably improved; meanwhile, phthalic anhydride type polyester polyols with different molecular weights are selected for compounding, so that the cost is properly reduced, and the brightness of a final product can be adjusted; according to the preparation method provided by the invention, the main agent is used for preparing the solvent-type OH-terminated polyurethane adhesive through a-NCO insufficient method, the polyurethane composite adhesive with high hardness, good wear resistance, good flexibility and high curing speed is formed through the cross-linking reaction of the main agent and the curing agent, and the preparation method is simple in technological process and easy to prepare.

Description

Technical Field

[0001] This invention relates to the field of adhesive synthesis technology, and in particular to a polyurethane adhesive for water-resistant sandpaper and its preparation method. Background Technology

[0002] Commercially available sheet sandpaper mainly consists of a base material, a base adhesive, abrasive particles, and a top adhesive. The base adhesive primarily uses epoxy resin or phenolic resin, while the top adhesive (composite adhesive) is mostly made of modified phenolic resin. Although phenolic resin has excellent bonding, heat resistance, and abrasion resistance, its cured film is brittle, has poor impact resistance, and low flexibility.

[0003] Patent CN110938399 describes a high-toughness phenolic resin composite material prepared using phenolic resin, polyurethane, multifunctional amine additives, and silane coupling agents, which significantly improves the flexibility and leveling properties of phenolic resin. However, its color darkens after curing, which still fails to meet the requirements for producing light-colored or brightly colored coated products.

[0004] Patent CN111234152 describes a series of phenolic resins for sandpaper prepared by improving the synthesis process. Although the problem of color darkening during storage has been improved, the products still have poor impact resistance and flexibility after curing. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a polyurethane composite for water-resistant sandpaper and its preparation method. It uses phthalic anhydride-type polyester polyol as the main component, combined with chain extenders and isocyanates to synthesize polyurethane. This method improves upon traditional phenolic resin-based sandpaper composites by ensuring both bonding and grinding performance, addressing the problems of long curing time (typically requiring 3 hours at 110°C), poor folding endurance, and dark cured color.

[0006] The technical solution adopted in this invention is:

[0007] A polyurethane adhesive for water-resistant sandpaper, characterized in that it comprises a main agent and a curing agent in a 1:1 weight ratio, wherein the main agent comprises the following components in parts by weight:

[0008]

[0009]

[0010] Furthermore, the macromolecular phthalic anhydride-type polyester polyol is a phthalic anhydride-type polyester polyol with a molecular weight of 1000-2000.

[0011] Furthermore, the phthalic anhydride-type polyester polyol is one or more of poly(diethylene terephthalate diol) (PDP), polyethylene terephthalate diol (PEP), and polyhexanediol terephthalate diol (PHP).

[0012] Furthermore, the small molecule phthalic anhydride polyester polyol is a poly(diethylene terephthalate) diol (PDP) with a molecular weight of 350-450.

[0013] Furthermore, the small molecule phthalic anhydride polyester polyol is PDP-350 or PDP-450.

[0014] Furthermore, the chain extender is ethylene glycol (EG).

[0015] Further, the diisocyanate is toluene diisocyanate (TDI) and / or diphenylmethane diisocyanate (MDI-50).

[0016] Furthermore, the curing agent is Wanhua's 8103 (NCO content is 20±0.3%).

[0017] Based on the same inventive concept, this application also provides a method for preparing the above-mentioned polyurethane adhesive for water-resistant sandpaper, comprising the following preparation steps:

[0018] Main agent synthesis:

[0019] Mix 50-100 parts of macromolecular phthalic anhydride-type polyester polyol, 15-30 parts of small molecule phthalic anhydride-type polyester polyol, 0.31-1.24 parts of chain extender and 14-24 parts of EAC at 50-60℃ for 10-20 minutes.

[0020] Then add 7-14 parts of diisocyanate, slowly raise the temperature to 70-80℃, and react for 0.5 h;

[0021] Then add the remaining 3-6 parts of diisocyanate in multiple batches, and at the same time add the remaining 6-16 parts of EAC depending on the viscosity, and continue the reaction for 3-4 hours;

[0022] Take samples to test for NCO. Once no NCO residue is found, add 14-24 parts of DMC, stir for 10-15 minutes, cool and collect the material to obtain a main material with a solid content of 70±2% and a viscosity of 2000-4000 mpa.s / 25℃.

[0023] Prepare glue

[0024] Take 100 parts each of the main agent and curing agent mentioned above, add 40 parts of 1200 mesh light calcium carbonate, and dilute with an appropriate amount of xylene to form a 30-40% solution to form a composite adhesive.

[0025] Furthermore, the solid content of the prepared main material is 70±2%, and the viscosity is 2000-4000 mpa.s / 25℃.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. The polyurethane composite adhesive provided in this application includes a main agent and a curing agent. The main agent includes macromolecular phthalic anhydride-type polyester polyol, small molecule phthalic anhydride-type polyester polyol, chain extender, diisocyanate, ethyl acetate (EAC) and dimethyl carbonate (DMC). By selecting phthalic anhydride-type polyester polyol to synthesize polyurethane, the heat resistance and wear resistance of the product can be significantly improved.

[0028] 2. The polyurethane composite adhesive provided in this application, by selecting phthalic anhydride-type polyester polyols of different molecular weights for compounding, can appropriately reduce costs and also adjust the gloss of the final product.

[0029] 3. The preparation method provided in this application involves preparing a solvent-based OH-terminated polyurethane adhesive by using the -NCO under-addition method. Through the cross-linking reaction between the main agent and the curing agent, a polyurethane composite adhesive with high hardness, good wear resistance, good flexibility, and fast curing rate is formed. The process is simple and easy to prepare. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation process of the present invention. Detailed Implementation

[0031] To facilitate understanding of the present invention, it will be described more fully below through embodiments, and preferred embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Any other implementation schemes obtained by modifying or equivalently substituting the technical solutions of the present invention without inventive step are all within the protection scope of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0033] The numerical values ​​disclosed in the embodiments of this invention are approximate values, not definitive values. Where error or experimental conditions permit, all values ​​within the error range may be included, and the specific numerical values ​​disclosed in the embodiments of this invention are not limited to those specified.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] Example 1:

[0036] This embodiment provides a method for preparing polyurethane adhesive for water-resistant sandpaper, and the preparation steps are as follows:

[0037] (1) Synthesis of main agent

[0038] Mix 100 parts of PDP-2000, 17.5 parts of PDP-350, 1.24 parts of EG, and 19.93 parts of ethyl acetate at 50-60℃ for 10-20 minutes.

[0039] Then add 7.31 parts of TDI-80, slowly raise the temperature to 70-80℃, and react for 0.5 hours;

[0040] Then add the remaining 3.13 parts of TDI-80 in multiple batches, and at the same time add the remaining 13.29 parts of EAC depending on the viscosity, and continue to react for 3-4 hours;

[0041] Take samples to test for NCO. Once no NCO residue is found, add 22.15 parts of DMC, stir for 10-15 minutes, and then cool and collect the material.

[0042] The final product has a solid content of 70±2% and a viscosity of 1500-2500 mpa.s / 25℃.

[0043] (2) Adhesive preparation

[0044] Take 100 parts each of the main agent and curing agent (Wanhua's 8103) and add 40 parts of 1200 mesh light calcium carbonate. Dilute with an appropriate amount of xylene to make a 30-40% solution and prepare a composite adhesive.

[0045] Example 2:

[0046] This embodiment provides a method for preparing polyurethane adhesive for water-resistant sandpaper, and the preparation steps are as follows:

[0047] (1) Synthesis of main agent

[0048] Mix 50 parts of PEP-1000, 17.5 parts of PDP-350, 0.62 parts of EG, and 13.21 parts of EAC at 50-60℃ for 10-20 minutes.

[0049] Then add 12.25 parts of MDI-50, slowly raise the temperature to 70-80℃, and react for 0.5 hours;

[0050] Then add the remaining 5.25 parts of MDI-50 in multiple batches, and at the same time add the remaining 8.81 parts of EAC depending on the viscosity, and continue to react for 3-4 hours;

[0051] Take samples to test for NCO. Once no NCO residue is found, add 14.68 parts of DMC, stir for 10-15 minutes, and then cool and collect the material.

[0052] The final product has a solid content of 70±2% and a viscosity of 2000-3000 mpa.s / 25℃.

[0053] (2) Adhesive preparation

[0054] Take 100 parts each of the main agent and curing agent (Wanhua's 8103) and add 40 parts of 1200 mesh light calcium carbonate. Dilute with an appropriate amount of xylene to make a 30-40% solution and prepare a composite adhesive.

[0055] Example 3:

[0056] This embodiment provides a method for preparing polyurethane adhesive for water-resistant sandpaper, and the preparation steps are as follows:

[0057] (1) Synthesis of main agent

[0058] Mix 80 parts of PHP-2000, 27 parts of PDP-450, 0.93 parts of EG, and 18.97 parts of EAC at 50-60℃ for 10-20 minutes.

[0059] Next, add 10.5 parts of MDI-50, slowly raise the temperature to 70-80℃, and react for 0.5 hours;

[0060] Then add the remaining 4.50 parts of MDI-50 in multiple batches, and at the same time add the remaining 12.64 parts of EAC depending on the viscosity, and continue to react for 3-4 hours;

[0061] Take samples to test for NCO. Once no NCO residue is found, add 21.07 parts of DMC, stir for 10-15 minutes, and then cool and collect the material.

[0062] The final product has a solid content of 70±2% and a viscosity of 3000-4000 mpa.s / 25℃.

[0063] (2) Adhesive preparation

[0064] Take 100 parts each of the main agent and curing agent (Wanhua's 8103) and add 40 parts of 1200 mesh light calcium carbonate. Dilute with an appropriate amount of xylene to make a 30-40% solution and prepare a composite adhesive.

[0065] Comparative example:

[0066] The difference between this comparative case and implementation cases 1-3 is that phenolic resin (Jinan Shengquan PF-2431) is used for the lamination, while the rest of the process is the same as in implementation cases 1-3.

[0067] The composite adhesives prepared in Examples 1-3 and the comparative examples were coated as follows for performance testing:

[0068] Coating is done in two steps

[0069] 1. Coating with adhesive: Heat the sandpaper semi-finished product A (the base adhesive is epoxy resin mixed with polyamide 650) to 110-130℃ and pre-dry for 30-60 minutes. Then coat the above adhesive onto the upper surface of the semi-finished product A and heat it to 100-120℃ to dry for 0.5 hours to obtain the sandpaper semi-finished product B.

[0070] 2. Apply dehumidifying agent: Spray the dehumidifying agent (MJ-302) evenly onto the upper surface of the sandpaper semi-finished product B.

[0071] Then, it was tested after being left at room temperature for 48 hours.

[0072] The prepared samples were then subjected to the following tests:

[0073] 1. Appearance test: Observe whether the sample is transparent and shiny;

[0074] 2. Folding endurance: Cut sandpaper into 150mm*120mm pieces, then fold it in both directions until it breaks. The number of times the sandpaper breaks is the folding endurance (the more folding endurance, the better the flexibility).

[0075] 3. Grinding amount test: Soak sandpaper in water for 2 hours, then grind 304 stainless steel with a sander for 0.5 hours. Record the reduction in mass of 304 stainless steel, which is the grinding amount (the higher the grinding amount, the better the adhesion performance of the adhesive to the abrasive).

[0076] The performance test results of Examples 1-3 and the comparative examples are shown in the table below:

[0077]

[0078] As shown in the table above, the polyurethane composites prepared in Examples 1-3 all exhibit excellent rapid curing, flexural strength, and abrasion resistance. Furthermore, the composites prepared in Examples 1-3 are all transparent and highly glossy, demonstrating significantly better performance than the phenolic resin composites in the comparative examples.

[0079] Specifically, the polyurethane composite provided in this application uses phthalic anhydride-type polyester polyols to synthesize polyurethane, which can significantly improve the heat resistance and wear resistance of the product. At the same time, by using phthalic anhydride-type polyester polyols with different molecular weights for compounding, the cost can be reduced, and the gloss of the final product can be adjusted to better meet application requirements.

[0080] The preparation method provided in this application involves preparing a solvent-based OH-terminated polyurethane adhesive by using the -NCO under-addition method. Through the cross-linking reaction between the main agent and the curing agent, a polyurethane composite adhesive with high hardness, good wear resistance, good flexibility, and fast curing rate is formed. The process is simple and easy to prepare.

[0081] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A polyurethane adhesive for water-resistant sandpaper, characterized in that, It comprises a base agent and a curing agent in a 1:1 weight ratio, wherein the base agent comprises the following components in parts by weight:

2. The polyurethane-coated waterproof sandpaper according to claim 1, characterized in that, The macromolecular phthalic anhydride-type polyester polyol is a phthalic anhydride-type polyester polyol with a molecular weight of 1000-2000.

3. The polyurethane coating for water-resistant sandpaper according to claim 2, characterized in that, The phthalic anhydride-type polyester polyol is one or more of poly(diethylene terephthalate diol), poly(ethylene terephthalate diol), and poly(hexanediol terephthalate diol).

4. The polyurethane coating for water-resistant sandpaper according to claim 1, characterized in that, The small molecule phthalic anhydride polyester polyol is a poly(diethylene terephthalate) diol with a molecular weight of 350-450.

5. The polyurethane coating for water-resistant sandpaper according to claim 1, characterized in that, The small molecule phthalic anhydride polyester polyol is PDP-350 or PDP-450.

6. The polyurethane-coated waterproof sandpaper according to claim 1, characterized in that, The chain extender is ethylene glycol.

7. The polyurethane-coated waterproof sandpaper according to claim 1, characterized in that, The diisocyanate is toluene diisocyanate and / or diphenylmethane diisocyanate.

8. The polyurethane-coated waterproof sandpaper according to claim 1, characterized in that, The curing agent mentioned is Wanhua's 8103.

9. A method for preparing a polyurethane adhesive for water-resistant sandpaper as described in any one of claims 1-8, characterized in that, The preparation steps include the following: Main agent synthesis: Mix 50-100 parts of macromolecular phthalic anhydride-type polyester polyol, 15-30 parts of small molecule phthalic anhydride-type polyester polyol, 0.31-1.24 parts of chain extender and 14-24 parts of EAC at 50-60℃ for 10-20 minutes. Then add 7-14 parts of diisocyanate, slowly raise the temperature to 70-80℃, and react for 0.5 h; Then add the remaining 3-6 parts of diisocyanate in multiple batches, and at the same time add the remaining 6-16 parts of EAC depending on the viscosity, and continue the reaction for 3-4 hours; Take samples to test for NCO. Once no NCO residue is found, add 14-24 parts of DMC, stir for 10-15 minutes, cool and collect the material to obtain a main material with a solid content of 70±2% and a viscosity of 2000-4000 mpa.s / 25℃. Prepare glue Take 100 parts each of the main agent and curing agent mentioned above, add 40 parts of 1200 mesh light calcium carbonate, and dilute with an appropriate amount of xylene to form a 30-40% solution to form a composite adhesive.

10. The method for preparing polyurethane adhesive for water-resistant sandpaper according to claim 9, characterized in that, The solid content of the prepared main material is 70±2%, and the viscosity is 2000-4000 mpa.s / 25℃.

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