Thermal debonding type single-component moisture-curing polyurethane hot melt adhesive and preparation method thereof

Abstract

The invention provides a thermal debonding type single-component moisture-curing polyurethane hot melt adhesive and a preparation method thereof, and the thermal debonding type single-component moisture-curing polyurethane hot melt adhesive is mainly characterized in that thermal expansion microspheres with proper conditions and quantity ratio are introduced into a raw material system of a specific single-component moisture-curing polyurethane hot melt adhesive; in the bonding requirements of soft base materials such as leather and fabrics, a better bonding effect can be provided; in the recycling and reusing requirements of soft base materials such as leather and fabric, the adhesive layer can become fluffy under the specific temperature condition, and therefore the effects that the adhesive layer is damaged, and the base materials are effectively recycled are achieved. Meanwhile, the preparation method is simple, easy to control, mild in condition and suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of single-component moisture-curing polyurethane hot melt adhesives, and in particular relates to a thermally debondable single-component moisture-curing polyurethane hot melt adhesive and a preparation method thereof. Background Art

[0002] With the increasing development of the concept of environmental protection and low carbon, the recycling of various product substrates is becoming more and more important. Many socially responsible companies pursue the recycling of materials, which can save costs on the one hand and is conducive to environmental protection and low carbon on the other. In manufacturing, bonding processes are often used to combine different materials, such as using various adhesives to bond different substrates such as metals, plastics, and fabrics.

[0003] When recycling bonded substrates, it is often necessary to destroy the bonding interface first. For rigid bonded substrates, such as metals and plastic plates, the adhesive can be designed to be thermosetting. The adhesive layer will further cross-link at a certain temperature, the cohesive strength will increase, and the adhesive layer will be separated from the rigid bonded substrate, thereby achieving substrate recycling. For softer substrates, such as leather and fabrics, in addition to the intermolecular forces between the adhesive and the substrate, there are also more fiber bites, so it is more difficult to achieve substrate recycling. Summary of the invention

[0004] The purpose of the present invention is to provide a thermal debonding single-component moisture-curing polyurethane hot melt adhesive and a preparation method thereof in order to solve the above-mentioned technical problems, so that the adhesive prepared by the present invention is convenient for bonding soft substrates such as leather and fabrics, and is also convenient for recycling the substrates.

[0005] The technical solution adopted by the present invention is a thermal debonding type one-component moisture-curing polyurethane hot melt adhesive, the raw material composition of which, by weight, is specifically: 10-20 parts of amorphous polyester polyol; 25-45 parts of liquid polyester polyol; 15-25 parts of crystalline polyester polyol; 5-10 parts of heat-expandable microspheres; Isocyanate 20-25 parts; Stabilizer 0.01-0.1 parts; Antioxidant 0.1-0.5 parts; Catalyst 0.1-0.3 parts; In the present invention, amorphous polyester polyol, liquid polyester polyol, crystalline polyester polyol, heat-expandable microspheres, and isocyanate constitute the main materials of the system; stabilizer, antioxidant and catalyst constitute the auxiliary materials of the system.

[0006] The above-mentioned amorphous polyester polyol is an aromatic polyester polyol, whose glass transition temperature is greater than 10°C and whose hydroxyl value is 30mgKOH / g-120mgKOH / g; specifically, the polyacid of the amorphous polyester polyol is selected from at least one of terephthalic acid and phthalic anhydride, and the polyol is one or more of ethylene glycol, propylene glycol, 2-methyl-1,3-propanediol, 1,4-cyclohexanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol.

[0007] The above-mentioned liquid polyester polyol is an aromatic polyester polyol or an aliphatic polyester polyol, and its glass transition temperature is <-10°C and its hydroxyl value is 20mgKOH / g-56mgKOH / g; specifically, the polyacid of the liquid polyester polyol is selected from at least one of terephthalic acid, phthalic anhydride, isophthalic acid, adipic acid, and sebacic acid, and the polyol is one or more of diethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

[0008] The above-mentioned crystalline polyester polyol is an aliphatic polyester polyol, whose melting point is >30°C and whose hydroxyl value is 20mgKOH / g-56mgKOH / g; specifically, the polyacid of the crystalline polyester polyol is selected from at least one of sebacic acid, adipic acid, dodecanedioic acid, and tridecanedioic acid, and the polyol is one or more of 1,4-butanediol and 1,6-hexanediol.

[0009] The expansion temperature of the heat-expandable microspheres is 140°C-160°C, preferably 150°C. If the expansion temperature is too low, it will affect the normal use of the adhesive, and if it is too high, it will be unfavorable for the recovery of the substrate. At the same time, if the amount of the heat-expandable microspheres added is too low, it will not be enough to achieve debonding, and if it is too high, it will lead to high viscosity of the adhesive and low bonding strength, affecting the basic bonding effect. The shell of the heat-expandable microspheres is a copolymer of methacrylate and acrylonitrile, and the filler inside is a hydrocarbon; under the corresponding temperature conditions, the hydrocarbon inside quickly vaporizes and expands, and the polymer shell softens, thereby showing the expansion of the microspheres.

[0010] The isocyanate is one of diphenylmethane diisocyanate, isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate and dicyclohexylmethane diisocyanate.

[0011] The stabilizer is one of phosphoric acid, polyphosphoric acid, and p-toluenesulfonyl isocyanate; the antioxidant is a hindered phenol, such as antioxidants 1010, 1076, 264, etc.; the catalyst is one of dibutyltin dilaurate, stannous octoate, tetrabutyl titanate, triethylenediamine, 1,4-dimethylpiperazine, bismorpholinyl diethyl ether, bismorpholinyl triethyl ether, and dimorpholine polyoxyethylene ether.

[0012] The present invention also provides a method for preparing the above-mentioned thermal debonding type one-component moisture-curing polyurethane hot melt adhesive, which specifically comprises the following steps: (1) According to the preset ratio, amorphous polyester polyol, liquid polyester polyol, crystalline polyester polyol, heat-expandable microspheres, stabilizer and antioxidant are put into a vacuum reactor, heated to 115-125°C, mixed and stirred to melt, and dehydrated for 1h-2h under vacuum ≤200Pa; (2) Cool down to 100°C, add isocyanate, mix and stir evenly, then heat up to 120°C and react for 1 hour; (3) Adding a catalyst and conducting a vacuum degassing reaction for 0.5 h to 1 h; (4) After unloading, sealing and packaging, it is ready.

[0013] The innovation and beneficial effects of the present invention are as follows: in view of the recycling and reuse needs of soft substrates such as leather and fabrics, a thermal debonding type single-component moisture-curing polyurethane hot melt adhesive is specially designed. It mainly introduces heat-expandable microspheres with appropriate conditions and quantitative ratios into the raw material system of a specific single-component moisture-curing polyurethane hot melt adhesive, so that the product prepared by the present invention can provide a better bonding effect in the bonding needs of soft substrates such as leather and fabrics; in the recycling and reuse needs of soft substrates such as leather and fabrics, the adhesive layer can be made fluffy under specific temperature conditions, thereby achieving the effect of destroying the adhesive layer and effectively recycling the substrate. At the same time, the preparation method of the present invention is simple, easy to control, and has mild conditions, which is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0014] The technical solution of the present invention will be clearly and completely described below in conjunction with 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 creative work are within the scope of protection of the present invention.

[0015] Meanwhile, in each embodiment of the present invention, there is no special restriction on the source of each material, and commercially available products known to those skilled in the art and meeting the relevant property requirements may be used. Example

[0016] A thermal debonding reaction type polyurethane hot melt adhesive, the raw material composition of which, by weight parts, is shown in the following Table 1.

[0017] Table 1: Raw materials used in Example 1 Raw material type raw material Mass fraction Amorphous polyester polyol HDPOL 310P 10 Liquid polyester polyol Evonik 7230 35 Crystalline polyester polyol Evonik 7360 20 Heat Expandable Microspheres F-150D 10 Isocyanate MDI 25 Stabilizer Phosphoric acid 0.01 Antioxidants 1010 0.5 catalyst Bismorpholinyl diethyl ether 0.3 When preparing the thermal debonding reactive polyurethane hot melt adhesive, amorphous polyester polyol, liquid polyester polyol, crystalline polyester polyol, stabilizer, antioxidant, and heat-expandable microspheres are put into a vacuum reactor, heated to 115-125° C., mixed and stirred to melt, and dehydrated for 1h-2h under vacuum conditions of ≤200Pa until the water content is ≤500ppm; the system is cooled to 100° C., isocyanate is added, mixed and stirred evenly, and then heated to 120° C. and reacted for 1h; a catalyst is added, and a vacuum degassing reaction is carried out for 0.5h-1h until the viscosity and NCO% reach the preset targets; the product is obtained after discharging, sealing, and packaging. Example

[0018] Compared with Example 1, the difference lies in the raw material composition and ratio design, and the preparation steps are the same.

[0019] Table 2: Raw materials used in Example 2 Raw material type raw material Mass fraction Amorphous polyester polyol HDPOL-320P 15 Liquid polyester polyol Evonik 7230 40 Crystalline polyester polyol 3000H 15 Heat Expandable Microspheres 951DU120 5 Isocyanate MDI 25 Stabilizer Phosphoric acid 0.05 Antioxidants 1010 0.2 catalyst Bismorpholinyl diethyl ether 0.1 Example

[0020] Compared with Example 1, the difference lies in the raw material composition and ratio design, and the preparation steps are the same.

[0021] Table 3: Raw materials used in Example 3 Raw material type raw material Mass fraction Amorphous polyester polyol P-511 20 Liquid polyester polyol HDPOL-322 25 Crystalline polyester polyol Evonik 7360 25 Heat Expandable Microspheres 951DU120 5 Isocyanate MDI 25 Stabilizer Phosphoric acid 0.01 Antioxidants 1010 0.1 catalyst Bismorpholinyl diethyl ether 0.2 Example

[0022] Compared with Example 1, the difference lies in the raw material composition and ratio design, and the preparation steps are the same.

[0023] Table 4: Raw materials used in Example 4 Raw material type raw material Mass fraction Amorphous polyester polyol FLP-PA1000N 15 Liquid polyester polyol Evonik 7230 30 Crystalline polyester polyol Evonik 7360 25 Heat Expandable Microspheres F-150D 10 Isocyanate MDI 20 Stabilizer Phosphoric acid 0.1 Antioxidants 1076 0.2 catalyst Bismorpholinyl diethyl ether 0.3 Example

[0024] Compared with Example 1, the difference lies in the raw material composition and ratio design, and the preparation steps are the same.

[0025] Table 5: Raw materials used in Example 5 Raw material type raw material Mass fraction Amorphous polyester polyol FLP-PA1000N 10 Liquid polyester polyol HDPOL-322 45 Crystalline polyester polyol 3000H 15 Heat Expandable Microspheres 951DU120 5 Isocyanate MDI 25 Stabilizer Phosphoric acid 0.1 Antioxidants 1076 0.2 catalyst Bismorpholinyl diethyl ether 0.2 Example

[0026] Compared with Example 1, the difference lies in the raw material composition and ratio design, and the preparation steps are the same.

[0027] Table 6: Raw materials used in Example 6 Raw material type raw material Mass fraction Amorphous polyester polyol HDPOL-320P 20 Liquid polyester polyol HDPOL-322 32 Crystalline polyester polyol 3000H 20 Heat Expandable Microspheres F-150D 8 Isocyanate MDI 20 Stabilizer Phosphoric acid 0.05 Antioxidants 1010 0.5 catalyst Bismorpholinyl diethyl ether 0.1 Example

[0028] Compared with Example 1, the difference lies in the raw material composition and ratio design, and the preparation steps are the same.

[0029] Table 7: Raw materials used in Example 7 Raw material type raw material Mass fraction Amorphous polyester polyol HDPOL-320P 20 Liquid polyester polyol Evonik 7230 30 Crystalline polyester polyol 3000H 20 Heat Expandable Microspheres F-150D 10 Isocyanate MDI 20 Stabilizer Phosphoric acid 0.05 Antioxidants 1010 0.2 catalyst Bismorpholinyl diethyl ether 0.1 Comparative Example 1 Compared with Example 1, the difference lies in the raw material composition and ratio design, and the preparation steps are the same.

[0030] Table 8: Raw materials used in Comparative Example 1 Raw material type raw material Mass fraction Amorphous polyester polyol HDPOL-320P 20 Liquid polyester polyol Evonik 7230 40 Crystalline polyester polyol 3000H 20 Heat Expandable Microspheres F-150D 0 Isocyanate MDI 20 Stabilizer Phosphoric acid 0.05 Antioxidants 1076 0.2 catalyst Bismorpholinyl diethyl ether 0.2 Comparative Example 2 Compared with Example 1, the difference lies in the raw material composition and ratio design, and the preparation steps are the same.

[0031] Table 9: Raw materials used in Comparative Example 2 Raw material type raw material Mass fraction Amorphous polyester polyol HDPOL-320P 20 Liquid polyester polyol Evonik 7230 25 Crystalline polyester polyol 3000H 20 Heat Expandable Microspheres F-150D 15 Isocyanate MDI 20 Stabilizer Phosphoric acid 0.05 Antioxidants 1010 0.2 catalyst Bismorpholinyl diethyl ether 0.2

[0032] The products obtained in the above-mentioned Examples 1-7 and the products obtained in Comparative Examples 1-2 were laminated and compounded with leather from the same batch, and the specific results are shown in Table 10 below.

[0033] Table 10: Performance test results From Table 10 above, it can be clearly seen that the reactive polyurethane hot melt adhesive prepared by Examples 1-7, when applied to leather bonding, has excellent bonding strength. After the adhesive is baked at 150°C for 20 minutes, the adhesive layer foams and expands, the strength drops sharply, the bonding interface is destroyed, and the appearance of the leather substrate is intact, indicating that the scheme has achieved the effect of thermal debonding and recycling the substrate. Comparative Example 1 does not add heat-expandable microspheres, and has excellent bonding strength. After the adhesive is baked at 150°C for 20 minutes, the adhesive layer is not damaged; after the adhesive is baked at 170°C for 20 minutes, the leather substrate changes color and deforms, but the adhesive layer is still not damaged, and the substrate cannot be recycled. Comparative Example 2 adds 15 parts of heat-expandable microspheres and is applied to leather bonding. The bonding force is significantly reduced. After the adhesive is baked at 150°C for 20 minutes, the adhesive layer foams and expands, the strength drops sharply, and the bonding interface is destroyed. Although the effect of thermal debonding is achieved, the bonding force in application is not good.

Claims

1. A thermal debonding type one-component moisture-curing polyurethane hot melt adhesive, characterized in that: The raw material composition of the thermal debonding type one-component moisture-curing polyurethane hot melt adhesive is specifically as follows, by weight: 10-20 parts of amorphous polyester polyol; 25-45 parts of liquid polyester polyol; 15-25 parts of crystalline polyester polyol; 5-10 parts of heat-expandable microspheres; Isocyanate 20-25 parts; Stabilizer 0.01-0.1 parts; Antioxidant 0.1-0.5 parts; Catalyst 0.1-0.3 parts; The expansion temperature of the heat-expandable microspheres is 140° C.-160° C., the outer shell is a copolymer of methacrylate and acrylonitrile, and the inner filler is hydrocarbon.

2. The thermal debonding one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: The expansion temperature of the heat-expandable microspheres is 150°C.

3. The thermal debonding one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: Amorphous polyester polyol is an aromatic polyester polyol, and its glass transition temperature is greater than 10°C, and its hydroxyl value is 30mgKOH / g-120mgKOH / g.

4. The thermal debonding one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: The liquid polyester polyol is an aromatic polyester polyol or an aliphatic polyester polyol, and has a glass transition temperature of <-10°C and a hydroxyl value of 20 mgKOH / g-56 mgKOH / g.

5. The thermal debonding one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: The crystalline polyester polyol is an aliphatic polyester polyol, and its melting point is>30°C, and the hydroxyl value is 20mgKOH / g-56mgKOH / g.

6. The thermal debonding type one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: The isocyanate is one of diphenylmethane diisocyanate, isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate and dicyclohexylmethane diisocyanate.

7. The thermal debonding one-component moisture-curing polyurethane hot melt adhesive according to claim 1, characterized in that: The stabilizer is one of phosphoric acid, polyphosphoric acid, and p-toluenesulfonyl isocyanate; the antioxidant is a hindered phenol antioxidant; and the catalyst is one of dibutyltin dilaurate, stannous octoate, tetrabutyl titanate, triethylenediamine, 1,4-dimethylpiperazine, bismorpholinyl diethyl ether, bismorpholinyl triethyl ether, and dimorpholine polyoxyethylene ether.

8. The method for preparing a thermal debonding type one-component moisture-curing polyurethane hot melt adhesive according to any one of claims 1 to 7, characterized in that: (1) According to the preset ratio, amorphous polyester polyol, liquid polyester polyol, crystalline polyester polyol, heat-expandable microspheres, stabilizer and antioxidant are put into a vacuum reactor, heated to 115-125°C, mixed and stirred to melt, and dehydrated for 1h-2h under vacuum ≤200Pa; (2) Cool down to 100°C, add isocyanate, mix and stir evenly, then heat up to 120°C and react for 1 hour; (3) Adding a catalyst and conducting a vacuum degassing reaction for 0.5 h to 1 h; (4) After unloading, sealing and packaging, it is ready.