CN109929500B - Method for preparing polyurethane hot melt adhesive, polyurethane hot melt adhesive and processed product - Google Patents
Method for preparing polyurethane hot melt adhesive, polyurethane hot melt adhesive and processed product Download PDFInfo
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- CN109929500B CN109929500B CN201811625419.0A CN201811625419A CN109929500B CN 109929500 B CN109929500 B CN 109929500B CN 201811625419 A CN201811625419 A CN 201811625419A CN 109929500 B CN109929500 B CN 109929500B
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Abstract
The invention provides a method for preparing a polyurethane hot melt adhesive, the polyurethane hot melt adhesive and a processed product. The method comprises the following steps: (1) synthesis of a prepolymer: mixing isocyanate and polyester diol, and reacting for 1-3 hours at 70-90 ℃ in the presence of a catalyst to obtain a prepolymer, (2) chain extension reaction: cooling the prepolymer to 40-60 ℃, adding a chain extender, and reacting for 1-2 hours at 40-60 ℃ to obtain a polyurethane hot melt adhesive; wherein, in terms of molar ratio, the ester group in isocyanate: hydroxyl group in polyester diol: chain extender 1: 0.625-0.91: 0.045-0.1875; the dosage of the catalyst accounts for 0.05-0.2% of the total mass of the isocyanate, the polyester diol and the chain extender. The method improves the melt fluidity of the polyurethane hot melt adhesive, simultaneously keeps better mechanical property, and simultaneously has excellent properties of flexibility, water resistance, acid and alkali resistance and the like. In addition, the method has simple synthesis process and low cost.
Description
Technical Field
The invention relates to the technical field of hot melt adhesives, in particular to a method for preparing a polyurethane hot melt adhesive, the polyurethane hot melt adhesive and a processed product.
Background
The hot melt adhesive is a plastic adhesive, the physical state of which changes along with the change of temperature within a certain temperature range, and the chemical property of which is unchanged, is nontoxic and tasteless, and belongs to an environment-friendly chemical product. The product is solid, so the product is convenient to package, transport and store, and has no solvent, pollution and toxicity; and the production process is simple, the added value is high, the bonding strength is high, the speed is high, and the like. It is solid at normal temperature, and is heated to melt to certain temperature to become fluid liquid with certain viscosity.
Polyurethane hot melt adhesives are a common hot melt adhesive. In application, in order to ensure that the polyurethane hot melt adhesive has enough strength, aromatic polyester polyol is often adopted, but due to the structural characteristics of aromatic benzene rings, the viscosity of the polyurethane melt is very high, and the operation is difficult.
The chinese patent CN1760304 adopts hyperbranched polyester polyol to synthesize polyurethane, which reduces the viscosity of the system, but also increases the cost and the complexity of the process. The Chinese patent CN102492388 reduces the viscosity of the polyurethane hot melt adhesive system by adding fluorocarbon surfactant, but the residual fluorocarbon surfactant can cause adverse effect on the mechanical property or safety of the polyurethane hot melt adhesive.
Disclosure of Invention
Aiming at the problems, the invention also provides a method for preparing the polyurethane hot melt adhesive, which has simple process and low cost. The invention also provides the polyurethane hot melt adhesive prepared by the method, which has high melt flowability and high strength, and is safe and environment-friendly. The invention also provides a processed product adopting the polyurethane hot melt adhesive.
In order to achieve the above object, the present invention adopts the following technical solutions.
In one aspect, the present invention provides a method for preparing a polyurethane hot melt adhesive, comprising:
(1) synthesis of a prepolymer: mixing isocyanate and polyester dihydric alcohol, reacting for 1-3 hours at 70-90 ℃ in the presence of a catalyst to obtain a prepolymer,
(2) chain extension reaction: cooling the prepolymer to 40-60 ℃, adding a chain extender, and reacting for 1-2 hours at 40-60 ℃ to obtain a polyurethane hot melt adhesive;
wherein, in terms of molar ratio, the ester group in isocyanate: hydroxyl group in polyester diol: chain extender 1: 0.625-0.91: 0.045-0.1875; the dosage of the catalyst accounts for 0.05-0.2% of the total mass of the isocyanate, the polyester diol and the chain extender.
The preparation method comprises the steps of firstly synthesizing a prepolymer, then carrying out chain extension reaction to obtain the polyurethane hot melt adhesive, and selecting a specific reaction system and suitable reaction conditions, so that the prepared polyurethane hot melt adhesive has high melt flowability and high strength, and is safe and environment-friendly.
According to the above process, preferably, the molar ratio of ester groups in the isocyanate: hydroxyl group in polyester diol: the chain extender is 1: 0.7-0.9: 0.05-0.15, more preferably 1: 0.7-0.85: 0.075-0.15, and most preferably 1:0.8: 0.1.
According to the above method, preferably, the catalyst is used in an amount of 0.05% to 0.15%, more preferably 0.05% to 0.1%, further preferably 0.05% to 0.08%, most preferably 0.075% to 0.08%, of the total mass of the isocyanate, the polyester diol and the chain extender. Isocyanates which may be used in the process of the present invention include one or more of diphenylmethane diisocyanate, 1, 5-naphthalene diisocyanate, tetramethyl diisocyanate, p-phenylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dimethylene phenyl diisocyanate and polymethylene polyphenyl polyisocyanates. Wherein the polymethylene polyphenyl polyisocyanate has the formula [ C6H3(NCO)CH2]n(n>2)。
Polyester diols useful in the process of the present invention include: one or more of polyethylene adipate glycol, polybutylene adipate glycol, polyhexamethylene adipate glycol, polyethylene glycol phthalate glycol, poly-epsilon-caprolactone glycol, and polycarbonate glycol.
Chain extenders useful in the process of the present invention include one or more of dimethylglyoxime, 1, 2-benzenediol, 1, 3-benzenediol and 1, 4-benzenediol. The inventors have surprisingly found that when the above compound or the compound having the function of a blocking agent is further selected as a chain extender based on the above method, when the temperature is raised to the melting temperature of the hot melt adhesive (for example, 110-. When the temperature is reduced to room temperature, the free isocyanate groups and the active hydrogen in the chain extender can easily react to generate macromolecular polyurethane, so that the polyurethane can keep stronger mechanical property at the normal temperature.
Catalysts useful in the process of the present invention include one or more of dibutyltin dilaurate, stannous octoate, triethylene diamine, or triethanolamine.
It is to be understood that the specific selections of the isocyanates, polyester diols, chain extenders and catalysts listed above may be used in the present invention in any possible combination.
In one embodiment, the isocyanate is 4, 4-diphenylmethane diisocyanate, the polyester diol is polyethylene adipate diol (e.g., having a molecular weight of 2000), the chain extender is dimethylglyoxime, and the catalyst is dibutyltin dilaurate.
In another embodiment, the isocyanate is 4, 4-diphenylmethane diisocyanate, the polyester diol is a polycarbonate diol (e.g., having a molecular weight of 3000), the chain extender is dimethylglyoxime, and the catalyst is dibutyltin dilaurate.
In another embodiment, the isocyanate is 4, 4-diphenylmethane diisocyanate, the polyester diol is polybutylene adipate diol (e.g., having a molecular weight of 2000), the chain extender is dimethylglyoxime, and the catalyst is stannous octoate.
In another embodiment, the isocyanate is 4, 4-diphenylmethane diisocyanate, the polyester diol is polybutylene adipate diol (e.g., having a molecular weight of 2000), the chain extender is 1, 4-benzenediol, and the catalyst is stannous octoate.
The above process of the present invention further comprises a step of removing water from the polyester diol to purify the polyester diol raw material. Any method capable of effecting water removal may be used in the present invention, the most common method being vacuum dewatering. For example, the polyester diol starting material is dehydrated under vacuum at 100 ℃ and 120 ℃ for 1 to 3 hours.
In another aspect, the invention also provides a polyurethane hot melt adhesive prepared according to the method. The hot melt adhesive can be heated in use, for example, to temperatures of 110 ℃ and 140 ℃ or higher, at which the hot melt adhesive melt has a high flowability.
The invention also provides a processed product obtained by adopting the polyurethane hot melt adhesive. The article of manufacture comprises: leather, textile, and ceramic products, among others.
The method improves the melt fluidity of the polyurethane hot melt adhesive, simultaneously keeps better mechanical property, and simultaneously has excellent properties of flexibility, water resistance, acid and alkali resistance and the like. In addition, the method has simple synthesis process and low cost, and particularly has great application value in the aspects of leather, textile, ceramic and other materials.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
the raw material molar ratio of the hot melt adhesive prepared in this example was: isocyanate group: hydroxyl group in polyester diol: chain extender 1:0.8: 0.1; the amount of the catalyst is 0.05% of the total mass of the raw materials.
Wherein the isocyanate is 4, 4-diphenylmethane diisocyanate; the polyester dihydric alcohol is polyethylene glycol adipate glycol, and the molecular weight is 2000; the chain extender is dimethylglyoxime; the catalyst was dibutyltin dilaurate.
The preparation process comprises the following steps:
(1) synthesis of a prepolymer: the polyethylene glycol adipate glycol is placed at 120 ℃ for vacuum dehydration for 2 hours and cooled to room temperature. Mixing 4, 4-diphenylmethane diisocyanate and dehydrated polyethylene glycol adipate glycol according to the molar ratio of isocyanate groups to hydroxyl groups of 1:0.8, charging into a reactor, introducing nitrogen while stirring, heating to 80 ℃, adding dibutyltin dilaurate with the total reaction mass of 0.05%, and reacting for 2 hours to obtain the prepolymer.
(2) Chain extension reaction: and (2) cooling the prepolymer generated in the step (1) to 40 ℃, adding dimethylglyoxime, and keeping the temperature at 40 ℃ for reacting for 1 hour to obtain the polyurethane hot melt adhesive.
Example 2: the raw material molar ratio of the hot melt adhesive prepared in this example was: isocyanate group: hydroxyl group in polyester diol: chain extender 1:0.8: 0.1; the amount of catalyst used was 0.1% of the total mass.
Wherein the isocyanate is 4, 4-diphenylmethane diisocyanate; the polyester dihydric alcohol is polycarbonate diol, and the molecular weight is 3000; the chain extender is dimethylglyoxime; the catalyst was dibutyltin dilaurate.
The preparation process comprises the following steps:
(1) synthesis of a prepolymer: the polycarbonate diol was dehydrated in vacuo at 120 ℃ for 2 hours and cooled to room temperature. Mixing 4, 4-diphenylmethane diisocyanate and dehydrated polycarbonate diol according to the molar ratio of isocyanate groups to hydroxyl groups of 1:0.8, charging into a reactor, introducing nitrogen while stirring, heating to 90 ℃, adding dibutyltin dilaurate with the total reaction mass of 0.05%, and reacting for 2 hours to obtain the prepolymer.
(2) Chain extension reaction: and (2) cooling the prepolymer generated in the step (1) to 40 ℃, adding dimethylglyoxime, and keeping the temperature at 40 ℃ for reacting for 1 hour to obtain the polyurethane hot melt adhesive.
Example 3:
the raw material molar ratio of the hot melt adhesive prepared in this example was: isocyanate group: hydroxyl group in polyester diol: chain extender 1: 0.7: 0.15; the amount of the catalyst is 0.08% of the total mass of the raw materials.
Wherein the isocyanate is 4, 4-diphenylmethane diisocyanate; the polyester dihydric alcohol is poly butylene adipate glycol, and the molecular weight is 2000; the chain extender is dimethylglyoxime; the catalyst is stannous octoate.
The preparation process comprises the following steps:
(1) synthesis of a prepolymer: the poly (butylene adipate) glycol is placed at 120 ℃ for vacuum dehydration for 2 hours and cooled to room temperature. Mixing 4, 4-diphenylmethane diisocyanate and dehydrated polybutylene adipate glycol according to the molar ratio of isocyanate groups to hydroxyl groups of 1:0.7, charging into a reactor, introducing nitrogen while stirring, heating to 80 ℃, adding stannous octoate with the total reactant mass of 0.08%, and reacting for 2 hours to obtain the prepolymer.
(2) Chain extension reaction: and (2) cooling the prepolymer generated in the step (1) to 60 ℃, adding dimethylglyoxime, and keeping the temperature of 60 ℃ for reaction for 1 hour to obtain the polyurethane hot melt adhesive.
Example 4:
the invention provides a hot melt adhesive which comprises the following raw materials in molar ratio: isocyanate group: hydroxyl group in polyester diol: chain extender 1: 0.9: 0.05; the amount of catalyst used was 0.08% of the total mass.
Wherein the isocyanate is 4, 4-diphenylmethane diisocyanate; the polyester dihydric alcohol is poly butylene adipate glycol, and the molecular weight is 2000; the chain extender is 1, 4-benzenediol; the catalyst is stannous octoate.
The preparation process comprises the following steps:
(1) synthesis of a prepolymer: the poly (butylene adipate) glycol is placed at 120 ℃ for vacuum dehydration for 2 hours and cooled to room temperature. Mixing 4, 4-diphenylmethane diisocyanate and dehydrated polybutylene adipate glycol according to the molar ratio of isocyanate groups to hydroxyl groups of 1: 0.9, mixing, loading into a reactor, introducing nitrogen while stirring, heating to 80 ℃, adding stannous octoate with the total reactant mass of 0.08 percent, and reacting for 2 hours to obtain the prepolymer.
(2) Chain extension reaction: and (2) cooling the prepolymer generated in the step (1) to 40 ℃, adding 1, 4-benzenediol, and reacting for 1 hour at 40 ℃ to obtain the polyurethane hot melt adhesive.
Example 5
Example 5 differs from example 1 in that the chain extender is 1, 4-butanediol. Other conditions and procedures were the same except for this.
Example 6:
the difference between the present example and example 1 is that the molar ratio of the raw materials is: isocyanate group: hydroxyl group in polyester diol: chain extender 1: 0.65: 0.16. other conditions and procedures were the same except for this.
Comparative example 1
Comparative example 1 differs from example 1 in that the molar ratio of ester groups in the isocyanate: hydroxyl group in polyester diol: chain extender 1: 0.5: 0.2; the amount of the catalyst is 0.5% of the total mass of the isocyanate, the polyester diol and the chain extender. Other conditions and procedures were the same except for this.
The products obtained in examples 1 to 6 and comparative example 1 were tested according to the present invention, and the results of the tests are shown in table 1.
Peel strength: the strength of the bonded PVC plastic is tested by adopting a T-type peel strength test method according to GB/T2791-1995. Peel strength is the hot melt adhesive data after melt index testing.
Melt index: the sample was cut into small particles, approximately four grams or so, the melt flow rate instrument temperature was raised to 190 degrees, the sample was placed in a feed cylinder, an iron pan was placed, and the sample was melted. Cut at the point when the sample extruded about 5 cm (the time taken was noted) and weighed. It was then converted to a weight of 10 minutes. The average value is obtained by taking the average value for three times, and the method is carried out according to GB 3682-2000.
Table 1: EXAMPLES 1-6 Performance testing of products
As can be seen from Table 1, the hot melt adhesive in the examples of the present invention has significantly better melt flowability, the melt index is significantly higher than that of the hot melt adhesive in comparative example 1, and the hot melt adhesive can maintain better peel strength after high temperature cooling, and has excellent mechanical properties.
The product in the embodiment of the invention has better melt fluidity at high temperature, is convenient to operate, and recovers better mechanical property after cooling at the temperature, thereby effectively solving the problem that the melt fluidity and the mechanical property of the polyurethane hot melt adhesive are contradictory. In addition, the polyurethane hot melt adhesive also has good acid resistance, alkali resistance and low temperature resistance.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A method for preparing a polyurethane hot melt adhesive comprising:
(1) synthesis of a prepolymer: mixing isocyanate and polyester dihydric alcohol, reacting for 1-3 hours at 70-90 ℃ in the presence of a catalyst to obtain a prepolymer,
(2) chain extension reaction: cooling the prepolymer to 40-60 ℃, adding a chain extender, and reacting for 1-2 hours at 40-60 ℃ to obtain a polyurethane hot melt adhesive;
wherein, in terms of molar ratio, the ester group in isocyanate: hydroxyl group in polyester diol: chain extender 1: 0.625-0.91: 0.045-0.1875; the amount of the catalyst accounts for 0.05-0.2% of the total mass of the isocyanate, the polyester diol and the chain extender; the chain extender comprises one or more of dimethylglyoxime, 1, 2-benzenediol, 1, 3-benzenediol and 1, 4-benzenediol.
2. The process of claim 1, wherein the molar ratio of ester groups in the isocyanate: hydroxyl group in polyester diol: the chain extender is 1: 0.7-0.9: 0.05-0.15.
3. A process according to claim 1 or 2, wherein the catalyst is used in an amount of from 0.075 to 0.15% by weight of the total amount of isocyanate, polyester diol and chain extender.
4. The method of claim 1 or 2, wherein the isocyanate comprises one or more of diphenylmethane diisocyanate, 1, 5-naphthalene diisocyanate, tetramethyl diisocyanate, p-phenylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dimethylene phenyl diisocyanate, and polymethylene polyphenyl polyisocyanate.
5. The method of claim 1 or 2, wherein the polyester diol comprises: one or more of polyethylene adipate glycol, polybutylene adipate glycol, polyhexamethylene adipate glycol, polyethylene glycol phthalate glycol, poly-epsilon-caprolactone glycol, and polycarbonate glycol.
6. The method of claim 1 or 2, wherein the catalyst comprises one or more of dibutyltin dilaurate, stannous octoate, triethylenediamine, or triethanolamine.
7. The method of claim 1 or 2, further comprising the step of removing water from the polyester diol.
8. A polyurethane hot melt adhesive prepared according to the method of any one of claims 1-7.
9. An article of manufacture obtained using the polyurethane hot melt adhesive of claim 8.
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| CN114409921B (en) * | 2022-02-22 | 2022-11-18 | 华南农业大学 | Modified lignin polyol and preparation method of polyurethane hot melt adhesive thereof |
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| CN106893307A (en) * | 2017-01-18 | 2017-06-27 | 福建师范大学泉港石化研究院 | A kind of low melting point high-strength polyurethane 3D printing material and preparation method thereof |
| CN108641662A (en) * | 2018-05-11 | 2018-10-12 | 美瑞新材料股份有限公司 | A kind of low softening point Waterproof Breathable TPU hot melt adhesive and preparation method thereof |
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| CN106893307A (en) * | 2017-01-18 | 2017-06-27 | 福建师范大学泉港石化研究院 | A kind of low melting point high-strength polyurethane 3D printing material and preparation method thereof |
| CN108641662A (en) * | 2018-05-11 | 2018-10-12 | 美瑞新材料股份有限公司 | A kind of low softening point Waterproof Breathable TPU hot melt adhesive and preparation method thereof |
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