Polyurethane hot-melt adhesive, its production method and absorbent diaper

Abstract

The present application relates to the field of adhesives, and particularly discloses a polyurethane hot melt adhesive and a preparation method therefor, and a nursing pad. The polyurethane hot melt adhesive comprises the following raw materials in parts by weight: 20-40 parts of a polyester polyol, 30-60 parts of a polyether polyol, 0.05-0.2 parts of a stabilizer, 10-25 parts of a tackifying resin, 0.01-0.1 part of a catalyst, and 10-30 parts of isocyanate. The preparation method for the polyurethane hot melt adhesive comprises the following steps: preparation of the polyester polyol; mixing: mixing the polyester polyol, the polyether polyol, the stabilizer, and the tackifying resin, heating and stirring the mixture, and keeping the mixture under a vacuum condition for 50-70 minutes; preparation of a product: cooling the mixture to break the vacuum condition, then adding the isocyanate and the catalyst, and further carrying out a reaction under a vacuum condition. The obtained polyurethane hot melt adhesive has excellent thermal stability and tensile strength. The polyurethane hot melt adhesive is used between a water absorption cotton layer and a waterproof layer of the nursing pad, so that the nursing pad has excellent peel strength and hot water washing resistance.

Description

Polyurethane hot melt adhesive, preparation method thereof, and nursing pad Technical Field

[0001] The present application relates to the field of adhesives, and more specifically, to a polyurethane hot melt adhesive, a preparation method thereof, and a nursing pad. Background Art

[0002] Nursing pads are disposable sanitary products made of PE film, non-woven fabrics, fluff pulp, polymers and other materials. They are commonly used in daily life and have the characteristics of simple use, hygiene, cleanliness, softness and comfort. They can not only ensure that the user's body is dry and comfortable, prevent dirty sheets and mattresses, and eliminate the possibility of cross-infection between users and between users and caregivers, but also reduce the workload of medical staff and their families, and avoid the pain of changing sheets every day. They are ideal products for hospitals and home care. General nursing pads are made of three layers: the surface layer is a water-permeable fabric layer, the middle layer is a water-absorbent cotton layer, and the bottom layer is a waterproof layer to prevent water from passing through. Nursing pads are used for some routine examinations, but disposable nursing pads will cause a lot of material waste and increase costs. The water-absorbent cotton layer and the waterproof layer of general nursing pads are bonded with ordinary polyvinyl alcohol glue. The resulting nursing pad has poor composite strength and is very easy to debond when washed.

[0003] Summary of the Invention

[0004] The present application provides a polyurethane hot melt adhesive, a preparation method thereof, and a nursing pad. The obtained polyurethane hot melt adhesive has excellent thermal stability and tensile strength, good mechanical properties, and is used for bonding and laminating the absorbent cotton layer and the waterproof layer of the nursing pad. The obtained nursing pad has excellent peel strength and resistance to hot water washing.

[0005] In the first aspect, the polyurethane hot melt adhesive provided by the present application adopts the following technical solution:

[0006] A polyurethane hot melt adhesive comprises the following raw materials in parts by weight: 20-40 parts of polyester polyol, 30-60 parts of polyether polyol, 0.05-0.2 parts of stabilizer, 10-25 parts of tackifying resin, 0.01-0.1 parts of catalyst, and 10-30 parts of isocyanate; the polyester polyol has an acid value of 0.2-2 mgKOH / g and a hydroxyl value of 30-150 mgKOH / g; the polyurethane hot melt adhesive has an -NCO content of 2-5 wt% and a viscosity of 3000-10000 cps at a temperature of 100-120°C.

[0007] Furthermore, the weight average molecular weight of the polyester polyol is 1000-5000.

[0008] Furthermore, the catalyst is selected from one or more of dibutyltin dilaurate, stannous octoate, zinc isooctanoate, bismuth isooctanoate, and bismorpholinyl diethyl ether.

[0009] Strictly controlling the acidity and hydroxyl value of polyester polyols helps control the water sensitivity of polyurethane hot melt adhesives. The hydroxyl value determines the molecular weight of polyester polyols. If the hydroxyl value is low and the molecular weight of polyester polyols is high, the cohesion of the hot melt adhesive will increase, but the wettability will deteriorate. If the hydroxyl value is too high and the molecular weight of polyester polyols is low, the cohesion of the hot melt adhesive will be weakened. Furthermore, strict control of the -NCO content in the resulting polyurethane hot melt adhesive and its viscosity at 100-120°C helps improve the hot melt adhesive's operating temperature and improve its fluidity. Coating the adhesive between the absorbent cotton layer and the waterproof layer of the nursing pad gives the pad excellent peel strength and resistance to hot water washing.

[0010] Preferably, the polyether polyol is selected from at least one of polyoxypropylene glycol, polytetramethylene ether glycol, and polytetramethylene ether glycol-oxypropylene glycol.

[0011] Furthermore, the weight average molecular weight of the polyether polyol is 400-2000.

[0012] By adopting the above technical solution, the component selection and weight-average molecular weight of the polyether polyol are optimized, which is conducive to the formation of longer polymer chains, thereby improving the overall performance of the hot melt adhesive.

[0013] Preferably, the tackifying resin is at least one of acrylic resin, terpene resin, polyester resin and polyurethane resin.

[0014] By adopting the above technical solution, the tackifying resin can not only adjust the viscosity of the system and assist in improving the viscosity of the hot melt adhesive, but also increase the initial viscosity of the hot melt adhesive.

[0015] Preferably, the stabilizer is a hindered phenol antioxidant.

[0016] In a second aspect, the present application provides a method for preparing a polyurethane hot melt adhesive using the following technical solution:

[0017] A method for preparing a polyurethane hot melt adhesive comprises the following steps:

[0018] Preparation of polyester polyols: reacting aromatic dibasic acid with diol at elevated temperature to obtain a product with an acid value of 0.5-1 mgKOH / g, then cooling to room temperature, adding aliphatic dibasic acid and diol, and reacting at elevated temperature in a vacuum, and cooling after completion of the reaction;

[0019] Mixing: Mix polyester polyol, polyether polyol, stabilizer and tackifying resin, heat, stir, and maintain under vacuum conditions for 50-70 minutes;

[0020] Preparation of the product: After cooling and breaking the vacuum, add isocyanate and catalyst, and then react under vacuum conditions to obtain polyurethane hot melt adhesive.

[0021] In the step of preparing polyester polyol, aromatic dibasic acid is first reacted with diol, and then with aliphatic dibasic acid and diol, which is conducive to obtaining longer polymer chains and corresponding molecular structures, so that when polyester polyol, polyether polyol and isocyanate react, a polyurethane hot melt adhesive with corresponding molecular weight and functional group structure can be obtained, which is coated between the absorbent cotton layer and the waterproof layer of the nursing pad. The obtained nursing pad has excellent peel strength and hot water washing resistance.

[0022] Preferably, in parts by weight, the polyester polyol comprises 25-35 parts of aromatic dibasic acid, 25-35 parts of aliphatic dibasic acid, and 15-50 parts of diol.

[0023] Furthermore, in the reaction of aromatic dibasic acid and diol, the temperature is raised to 210-240° C., and the amount of diol used is 10-35 parts. In the reaction of aliphatic dibasic acid and diol, the temperature is raised to 200-230° C., and the amount of diol used is 5-15 parts.

[0024] Optimize the dosage relationship of diols in different steps to ensure better quality of the obtained polyester polyols.

[0025] Preferably, the aromatic dibasic acid includes one of isophthalic acid, terephthalic acid, and phthalic anhydride, and the aliphatic dibasic acid includes one of adipic acid, suberic acid, sebacic acid, and 1,4-cyclohexanedicarboxylic acid.

[0026] Furthermore, the aromatic dibasic acid is preferably phthalic anhydride, and the aliphatic dibasic acid is preferably adipic acid.

[0027] Preferably, the diol includes one of diethylene glycol, 1,4-butanediol and propylene glycol.

[0028] Preferably, the vacuum pressure is from -0.1 MPa to -0.01 MPa.

[0029] In a third aspect, the present application provides a nursing pad that adopts the following technical solution:

[0030] A nursing pad comprises a water-permeable layer, a water-absorbing layer and a waterproof layer, wherein the polyurethane hot-melt adhesive obtained above is coated between the water-absorbing layer and the waterproof layer.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. Strictly controlling the acidity and hydroxyl value of the polyester polyol is beneficial for controlling the water sensitivity of the polyurethane hot melt adhesive. The hydroxyl value determines the molecular weight of the polyester polyol. If the hydroxyl value is low and the molecular weight of the polyester polyol is high, the cohesion of the hot melt adhesive will increase, but the wettability will deteriorate. If the hydroxyl value is too high and the molecular weight of the polyester polyol is low, the cohesion of the hot melt adhesive will be weakened. Furthermore, strictly controlling the -NCO content of the polyurethane hot melt adhesive obtained by the reaction and its viscosity at a temperature of 100-120°C will help improve the operating temperature of the hot melt adhesive and improve its fluidity. Coating it between the absorbent cotton layer and the waterproof layer of the nursing pad will give the nursing pad excellent peel strength and hot water wash resistance.

[0033] 2. This application uses polyester polyol and polyether polyol as the main raw materials, combined with a tackifying resin, and reacts with isocyanate under the action of a catalyst to obtain a polyurethane hot melt adhesive. The polyurethane hot melt adhesive is used between the waterproof layer and the water-absorbing layer of the nursing pad. The obtained nursing pad can be reused, and its peel strength can reach 170N / 10cm. It can be repeatedly washed in hot water at 90°C and can withstand water washing for more than 100 times without delamination. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a process flow chart of the preparation method of the polyurethane hot melt adhesive of the present application. DETAILED DESCRIPTION

[0035] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0036] Example

[0037] Example 1

[0038] Polyurethane hot melt adhesive includes the following raw materials: 20 parts of polyester polyol, 30 parts of polyether polyol, 0.2 parts of stabilizer, 25 parts of tackifying resin, 0.01 parts of catalyst, and 10 parts of isocyanate;

[0039] The polyether polyol is polyoxypropylene glycol with a weight average molecular weight of 1000, the tackifying resin is acrylic resin, the stabilizer is hindered phenol antioxidant 1010, and the catalyst is dibutyltin dilaurate.

[0040] The preparation method of polyurethane hot melt adhesive comprises the following steps:

[0041] Preparation of polyester polyol: 25 parts of terephthalic acid and 10 parts of 1,4-butanediol were added to a reactor, heated to 210°C for reaction to obtain a product with an acid value of 0.5 mgKOH / g, and the reactor temperature was cooled to room temperature. 25 parts of suberic acid and 5 parts of diethylene glycol were then added to the reactor, heated to 225°C for reaction, and vacuum pressure was 0.09±0.01 MPa. After the reaction was completed, the temperature was cooled; the obtained polyester polyol had a weight-average molecular weight of 1000, a hydroxyl value of 30 mgKOH / g, and an acid value of 0.2 mgKOH / g;

[0042] Mixing: First, put the polyester polyol, polyether polyol and stabilizer into a sealed reactor and mix them. Heat to 120°C, stir at a stirring speed of 100 rpm for 10 minutes, and maintain under vacuum for 50-70 minutes. Then, add the tackifying resin, adjust the stirring speed to 150 rpm, and continue stirring for 30 minutes to obtain a mixture.

[0043] Preparation of the product: Cool the mixture to 80°C, break the vacuum, adjust the stirring speed to 100 rpm, quickly add the isocyanate and catalyst, then control the stirring speed to 150 rpm, evacuate the mixture, and react under a vacuum pressure of -0.09 MPa±0.01 to obtain a polyurethane hot melt adhesive. The obtained polyurethane hot melt adhesive has an -NCO content of 2 wt% and a viscosity of 3000 cps at a temperature of 120°C.

[0044] Example 2

[0045] Polyurethane hot melt adhesive includes the following raw materials: 40 parts of polyester polyol, 60 parts of polyether polyol, 0.05 parts of stabilizer, 10 parts of tackifying resin, 0.1 parts of catalyst, and 30 parts of isocyanate;

[0046] The polyether polyol is polytetramethylene ether glycol-propylene oxide glycol with a weight average molecular weight of 400, the tackifying resin is polyester resin, the stabilizer is hindered phenol antioxidant 1010, and the catalyst is stannous octoate.

[0047] The preparation method of polyurethane hot melt adhesive comprises the following steps:

[0048] Preparation of polyester polyol: 35 parts of isophthalic acid and 35 parts of propylene glycol were added to a reactor, heated to 240°C for reaction to obtain a product with an acid value of 1 mgKOH / g, and the reactor temperature was cooled to room temperature. 35 parts of sebacic acid and 15 parts of diethylene glycol were then added to the reactor, heated to 215°C for reaction, and vacuum pressure of 0.09±0.01 MPa was applied. After completion of the reaction, the temperature was cooled; the resulting polyester polyol had a weight-average molecular weight of 5000, a hydroxyl value of 150 mgKOH / g, and an acid value of 2 mgKOH / g;

[0049] Mixing: First, put the polyester polyol, polyether polyol and stabilizer into a sealed reactor and mix them. Heat to 120°C, stir at a stirring speed of 100 rpm for 10 minutes, and maintain under vacuum for 50-70 minutes. Then, add the tackifying resin, adjust the stirring speed to 150 rpm, and continue stirring for 30 minutes to obtain a mixture.

[0050] Preparation of the product: Cool the mixture to 100°C, break the vacuum, adjust the stirring speed to 100 rpm, quickly add the isocyanate and the catalyst, then control the stirring speed to 150 rpm, evacuate the mixture, and react under a vacuum pressure of -0.09 MPa±0.01 to obtain a polyurethane hot melt adhesive. The obtained polyurethane hot melt adhesive has an -NCO content of 5wt% and a viscosity of 7000cps at a temperature of 100°C.

[0051] Example 3

[0052] The difference from Example 1 is that, in preparing polyester polyol, 30 parts of terephthalic acid and 20 parts of diethylene glycol were put into a reactor, the temperature was raised to 220°C for reaction to obtain a product with an acid value of 0.8 mgKOH / g, and the temperature of the reactor was cooled to room temperature, and then 30 parts of 1,4-cyclohexanedicarboxylic acid and 10 parts of 1,4-butanediol were added to the reactor, the temperature was raised to 220°C for reaction, and the vacuum pressure was 0.09±0.01 MPa. After the reaction was completed, the temperature was cooled; the weight-average molecular weight of the obtained polyester polyol was 2000, the hydroxyl value was 100 mgKOH / g, and the acid value was 1 mgKOH / g; the rest was the same as Example 1.

[0053] Example 4

[0054] The difference from Example 3 is that in the step of preparing the polyester polyol, the aromatic dibasic acid is phthalic anhydride, the aliphatic dibasic acid is adipic acid, and the obtained polyester polyol has a weight-average molecular weight of 4000, a hydroxyl value of 80 mgKOH / g, and an acid value of 1.5 mgKOH / g; the rest is the same as Example 3.

[0055] Example 5

[0056] The difference from Example 4 is that the polyurethane hot melt adhesive includes the following raw materials: 30 parts of polyester polyol, 50 parts of polyether polyol, 0.1 part of stabilizer, 22 parts of tackifying resin, 0.07 part of catalyst, and 20 parts of isocyanate; the obtained polyurethane hot melt adhesive has an -NCO content of 3.5 wt % and a viscosity of 5000 cps at 120° C.; the rest is the same as Example 4.

[0057] Example 6

[0058] The difference from Example 5 is that the tackifying resin is a terpene resin and a polyester resin with a mass ratio of 1:1, and the polyether polyol is polytetramethylene ether glycol with a weight average molecular weight of 1500. The rest is the same as Example 5.

[0059] Application Examples

[0060] Application Example 1

[0061] A nursing pad comprises a water-permeable layer, a water-absorbing layer and a waterproof layer, wherein the polyurethane hot-melt adhesive prepared in Example 1 is coated between the water-absorbing layer and the waterproof layer.

[0062] Application Example 2

[0063] A nursing pad comprises a water-permeable layer, a water-absorbing layer and a waterproof layer, wherein the polyurethane hot-melt adhesive prepared in Example 2 is coated between the water-absorbing layer and the waterproof layer.

[0064] Application Example 3

[0065] A nursing pad comprises a water-permeable layer, a water-absorbing layer and a waterproof layer, wherein the polyurethane hot-melt adhesive prepared in Example 3 is coated between the water-absorbing layer and the waterproof layer.

[0066] Application Example 4

[0067] A nursing pad comprises a water-permeable layer, a water-absorbing layer and a waterproof layer, wherein the polyurethane hot-melt adhesive prepared in Example 4 is coated between the water-absorbing layer and the waterproof layer.

[0068] Application Example 5

[0069] A nursing pad comprises a water-permeable layer, a water-absorbing layer and a waterproof layer, wherein the polyurethane hot-melt adhesive prepared in Example 5 is coated between the water-absorbing layer and the waterproof layer.

[0070] Application Example 6

[0071] A nursing pad comprises a water-permeable layer, a water-absorbing layer and a waterproof layer, wherein the polyurethane hot-melt adhesive prepared in Example 6 is coated between the water-absorbing layer and the waterproof layer.

[0072] Comparative Example

[0073] Comparative Example 1

[0074] The difference from Example 6 is that an equal amount of polyester polyol is replaced by polyethylene glycol, and the remaining raw material components and amounts are the same as those in Example 6.

[0075] Comparative Example 2

[0076] The difference from Example 6 is that the polyester polyol is prepared by the following steps: 25 parts of terephthalic acid and 10 parts of 1,4-butanediol are added to a reactor, and the temperature is raised to 210°C for reaction to obtain a polyester polyol having an acid value of 3 mgKOH / g, a hydroxyl value of 20 mgKOH / g, and a weight-average molecular weight of 800. The remaining raw material components and amounts are the same as those in Example 6.

[0077] Comparative Example 3

[0078] The difference from Example 6 is that no polyether polyol is added, and the remaining raw material components and amounts are the same as those in Example 6.

[0079] Comparative Example 4

[0080] The difference from Example 6 is that no tackifying resin is added, and the amounts of other raw material components are the same as those in Example 6.

[0081] Application comparison

[0082] Comparative Application Example 1

[0083] The difference from Example 6 is that the polyurethane hot melt adhesive prepared in Comparative Example 1 is coated between the water-absorbing layer and the waterproof layer.

[0084] Application Comparative Example 2

[0085] The difference from Application Example 6 is that the polyurethane hot melt adhesive prepared in Comparative Example 2 is coated between the water-absorbing layer and the waterproof layer.

[0086] Application Comparative Example 3

[0087] The difference from Application Example 6 is that the polyurethane hot melt adhesive prepared in Comparative Example 3 is coated between the water-absorbing layer and the waterproof layer.

[0088] Comparative Application Example 4

[0089] The difference from Application Example 6 is that the polyurethane hot melt adhesive prepared in Comparative Example 4 is coated between the water-absorbing layer and the waterproof layer.

[0090] Performance testing

[0091] The nursing pads prepared in Application Examples 1-6 and Comparative Application Examples 1-4 were subjected to peel strength tests and the number of times they could withstand washing in 90° C. hot water without debonding. The results are recorded in Table 1.

[0092] The peel strength test method is as follows: 1. Cut the nursing pad into 10*20cm size, select 10 pieces in each group, apply an equal amount of polyurethane hot melt adhesive between the waterproof layer and the water-absorbing layer of the nursing pad, and label them. Use a tensile testing machine to perform a peel test and record the average value of the data.

[0093] The water-washing resistance test method is as follows: place nursing pads coated with polyurethane hot-melt adhesive in groups of 10, soak them in 90°C water and stir them at a speed of 100 r / min for 20 minutes, take out the samples to observe and evaluate their appearance, and check whether there is any debonding phenomenon. Repeat the above water-washing test until all samples have debonding phenomenon, and record the number of water washes when debonding phenomenon occurs for each sample, and take the final average value for record.

[0094] In combination with Application Examples 1-6 and Table 1, it can be seen that the hot melt adhesive prepared by Examples 1-6 of the present application is used for nursing pads, which can effectively improve the peel strength of the nursing pads, has good mechanical properties, and is excellent in resistance to hot water washing. It can be repeatedly washed in hot water at 90°C for more than 100 times without debonding, resulting in a reusable nursing pad, which can effectively reduce the cost of using the nursing pads.

[0095] Combining Application Example 6 and Comparative Application Examples 1-4 with Table 1, it can be seen that in Comparative Example 1, the polyester polyol is replaced with polyethylene glycol in equal amounts, in Comparative Example 2, some preparation steps in the polyester polyol are omitted, in Comparative Example 3, no polyether polyol is added, and in Comparative Example 4, there is a lack of a tackifying resin. The obtained polyurethane hot melt adhesive has undergone significant changes in both molecular structure and viscosity, and the overall performance of the obtained hot melt adhesive is poor. The peel strength of the corresponding product is reduced, and the number of hot water washes is also significantly reduced. This is because the polyester polyol is obtained by adopting the specific preparation steps of this application, and the acidity and hydroxyl value of the polyester polyol are strictly controlled, which is beneficial to controlling the sensitivity of the polyurethane hot melt adhesive to water. In addition, polyether polyol is used as the main raw material, combined with a tackifying resin, and reacted with isocyanate under the action of a catalyst to obtain a polyurethane hot melt adhesive. The -NCO content in the polyurethane hot melt adhesive obtained by the reaction and the viscosity at a temperature of 100-120°C are strictly controlled, which is beneficial to improving the use temperature of the hot melt adhesive and having good fluidity. It is coated between the absorbent cotton layer and the waterproof layer of the nursing pad, giving the nursing pad excellent peel strength and hot water wash resistance.

[0096] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A polyurethane hot-melt adhesive, characterized in that it contains the following raw materials in parts by weight: 20-40 parts of a polyester polyol, 30-60 parts of a polyether polyol, 0.05-0.2 parts of a stabilizer, 10-25 parts of a tackifying resin, 0.01-0.1 parts of a catalyst and 10-30 parts of an isocyanate; wherein the acid number of the polyester polyol is 0.2-2 mg KOH / g, and the hydroxyl number of the polyester polyol is 30-150 mg KOH / g; the content of -NCO groups in the polyurethane hot-melt adhesive is 2-5 wt.%, and the viscosity of the polyurethane hot-melt adhesive is 3000-10000 cP at a temperature of 100-120°C.

2. The polyurethane hot-melt adhesive according to claim 1, wherein the polyether polyol is at least one of polyoxypropylene glycol, polytetramethylene ether glycol, or polytetramethylene ether glycol-oxypropylene glycol.

3. The polyurethane hot melt adhesive according to claim 1, characterized in that the tack-increasing resin is at least one of an acrylic resin, a terpene resin, a polyester resin, or a polyurethane resin.

4. A polyurethane hot-melt adhesive according to claim 1, characterized in that the stabilizer is a sterically hindered phenolic antioxidant.

5. A method for producing a polyurethane hot-melt adhesive according to any one of claims 1 to 4, characterized in that it includes the following steps: obtaining a polyester polyol: an aromatic diacid and a diol are heated to carry out a reaction, a product with an acid number of 0.5-1 mg KOH / g is obtained and the product is cooled to room temperature, then an aliphatic diacid and a diol are added, heated to 200-230 ° C to carry out a reaction and after completion of the reaction, cooled to obtain a polyester polyol; mixing: a polyester polyol, a polyether polyol, a stabilizer and a tackifier resin are mixed to obtain a mixture, the mixture is heated and stirred, and then kept under vacuum for 50-70 minutes; Product production: The mixture is cooled and the vacuum is released, then isocyanate and catalyst are added to the mixture and the reaction is carried out under vacuum conditions to obtain a polyurethane hot-melt adhesive.

6. A method for producing a polyurethane hot-melt adhesive according to claim 5, characterized in that, based on the total weight of the polyester polyol, the polyester polyol contains the following starting materials in parts by weight: 25-35 parts of an aromatic diacid, 25-35 parts of an aliphatic diacid, and 15-50 parts of a diol.

7. A method for producing a polyurethane hot-melt adhesive according to claim 5 or 6, characterized in that the aromatic dibasic acid comprises one of isophthalic acid, terephthalic acid, or phthalic anhydride, and the aliphatic dibasic acid comprises one of adipic acid, suberic acid, sebacic acid, or 1,4-cyclohexanedicarboxylic acid.

8. A method for producing a polyurethane hot-melt adhesive according to claim 5 or 6, characterized in that the diol comprises one of diethylene glycol, 1,4-butanediol or propylene glycol.

9. A method for producing a polyurethane hot-melt adhesive according to paragraph 5, characterized in that the vacuum pressure is from -0.1 MPa to -0.01 MPa.

10. An absorbent diaper comprising a water-permeable layer, an absorbent cotton layer and a waterproof layer, characterized in that a polyurethane hot-melt adhesive according to any of paragraphs 1-4 or a polyurethane hot-melt adhesive obtained by the method according to any of paragraphs 5-9 is applied between the absorbent cotton layer and the waterproof layer.