Polyurethane hot melt adhesive, method for producing the same, and care pad

Abstract

The application relates to the field of adhesives, and particularly discloses a polyurethane hot melt adhesive, a preparation method thereof and a nursing pad. The 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 a stabilizer, 10-25 parts of tackifying resin, 0.01-0.1 parts of a catalyst and 10-30 parts of isocyanate. The preparation method comprises the following steps: preparing the polyester polyol; mixing: mixing the polyester polyol, the polyether polyol, the stabilizer and the tackifying resin, heating, stirring and maintaining for 50-70 minutes under vacuum; preparing the product: after cooling and breaking the vacuum, adding the isocyanate and the catalyst, and then reacting under vacuum. The obtained polyurethane hot melt adhesive has excellent thermal stability and tensile strength, and is used between a water-absorbing cotton layer and a waterproof layer of the nursing pad, so that the nursing pad has excellent peeling strength and hot water washing resistance.

Description

TECHNICAL FIELD

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

[0002] The nursing pad is a kind of disposable sanitary product made of PE film, non-woven fabric, fluff pulp, high polymer and other materials, which is widely used in life, has the characteristics of simple use, sanitary and clean, soft and comfortable, etc. It not only ensures the user's body dry and comfortable, prevents the bed sheet and mattress from being dirty, and eliminates the possibility of cross infection between users and between users and nursing staff, but also reduces the work burden of medical staff and family members, and relieves them from the pain of changing bed sheets every day. It is an ideal product for hospital and family care. Generally, the nursing pad is composed of three layers, the surface layer is a water permeable fabric layer, the middle layer is a water absorbing cotton layer, and the bottom layer is a waterproof layer to prevent water from passing through. For some routine examinations, nursing pads are used, but the one-time use of nursing pads will cause a large amount of material waste and increase the cost. The ordinary polyvinyl alcohol adhesive is used for adhesive bonding between the water absorbing cotton layer and the waterproof layer of the general nursing pad, and the obtained nursing pad has poor composite strength and is very easy to open the adhesive when washed. SUMMARY

[0003] 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, is used for adhesive bonding between the water absorbing cotton layer and the waterproof layer of the nursing pad, and the obtained nursing pad has excellent peel strength and hot water washing resistance.

[0004] In the first aspect, the polyurethane hot melt adhesive provided by the present application adopts the following technical scheme:

[0005] A polyurethane hot melt adhesive, comprising the following raw materials 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 acid value of the polyester polyol is 0.2-2 mgKOH / g, and the hydroxyl value is 30-150 mgKOH / g; the -NCO content of the polyurethane hot melt adhesive is 2-5 wt%, and the viscosity at a temperature of 100-120℃ is 3000-10000 cps.

[0006] Further, the weight average molecular weight of the polyester polyol is 1000-5000.

[0007] Further, the catalyst is selected from one or more of dibutyltin dilaurate, stannous octoate, zinc isooctoate, bismuth isooctoate and dimorpholinyl diethyl ether.

[0008] Strictly controlling the acidity and hydroxyl value of the polyester polyol helps control 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 cohesive force of the hot melt adhesive will increase, but the wettability will decrease. If the hydroxyl value is too high and the molecular weight of the polyester polyol is low, the cohesive force of the hot melt adhesive will be weakened. Further strict control of the -NCO content in the polyurethane hot melt adhesive obtained from the reaction, as well as its viscosity at 100-120℃, helps improve the application temperature of the hot melt adhesive and ensures good fluidity. When coated between the absorbent cotton layer and the waterproof layer of the nursing pad, it gives the nursing pad excellent peel strength and hot water wash resistance.

[0009] Preferably, the polyether polyol is selected from at least one of polypropylene oxide diol, polytetrahydrofuran ether diol, and polytetrahydrofuran ether diol-propylene oxide diol.

[0010] Furthermore, the weight-average molecular weight of the polyether polyol is 400-2000.

[0011] By adopting the above technical solutions, the selection of components and weight-average molecular weight of polyether polyols are optimized, which is conducive to the formation of longer polymer chains, thereby improving the overall performance of hot melt adhesives.

[0012] Preferably, the tackifying resin is at least one selected from acrylic resin, terpene resin, polyester resin, and polyurethane resin.

[0013] By adopting the above technical solutions, the tackifying resin can not only adjust the viscosity of the system and help improve the viscosity of the hot melt adhesive, but also increase the initial tack of the hot melt adhesive.

[0014] Preferably, the stabilizer is a hindered phenolic antioxidant.

[0015] Secondly, the preparation method of the polyurethane hot melt adhesive provided in this application adopts the following technical solution:

[0016] A method for preparing a polyurethane hot melt adhesive includes the following steps:

[0017] Preparation of polyester polyol: Aromatic diacid and diol are heated to react, and a product with an acid value of 0.5-1 mg KOH / g is obtained. The product is then cooled to room temperature. Aliphatic diacid and diol are added, and the mixture is heated to react under vacuum. After the reaction is completed, the mixture is cooled.

[0018] Mixing: Mix polyester polyol, polyether polyol, stabilizer and tackifying resin, heat and stir, and maintain under vacuum for 50-70 minutes;

[0019] Product preparation: Isocyanate and catalyst are added after cooling and breaking the vacuum, and then reacted under vacuum conditions to obtain polyurethane hot melt adhesive.

[0020] In the preparation of polyester polyol, aromatic diacids are first reacted with diols, and then aliphatic diacids and diols are reacted. This process is beneficial for obtaining longer polymer chains and corresponding molecular structures. When polyester polyols, polyether polyols and isocyanates react, polyurethane hot melt adhesives with corresponding molecular weights and functional group structures can be obtained. When coated between the absorbent cotton layer and the waterproof layer of the nursing pad, the resulting nursing pad has excellent peel strength and hot water washing resistance.

[0021] Preferably, by weight, the polyester polyol comprises 25-35 parts of aromatic dicarboxylic acid, 25-35 parts of aliphatic dicarboxylic acid, and 15-50 parts of diol.

[0022] Furthermore, in the reaction of aromatic diacids with diols, the temperature is raised to 210-240℃, and the amount of diol used is 10-35 parts. In the reaction of aliphatic diacids with diols, the temperature is raised to 200-230℃, and the amount of diol used is 5-15 parts.

[0023] Optimize the dosage of diols in different steps to ensure better quality of the obtained polyester polyols.

[0024] Preferably, the aromatic dicarboxylic acid includes one of isophthalic acid, terephthalic acid, and phthalic anhydride, and the aliphatic dicarboxylic acid includes one of adipic acid, octanoic acid, sebacic acid, and 1,4-cyclohexanedicarboxylic acid.

[0025] Furthermore, phthalic anhydride is preferred among aromatic dicarboxylic acids, and adipic acid is preferred among aliphatic dicarboxylic acids.

[0026] Preferably, the diol includes one of diethylene glycol, 1,4-butanediol, and propylene glycol.

[0027] Preferably, the vacuum pressure is between -0.1 MPa and -0.01 MPa.

[0028] Thirdly, the nursing pad provided in this application adopts the following technical solution:

[0029] A nursing pad includes a permeable layer, an absorbent layer, and a waterproof layer, wherein the absorbent layer and the waterproof layer are coated with the polyurethane hot melt adhesive obtained above.

[0030] In summary, this application has the following beneficial effects:

[0031] 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 cohesive force of the hot melt adhesive will increase, but the wettability will decrease. If the hydroxyl value is too high and the molecular weight of the polyester polyol is low, the cohesive force of the hot melt adhesive will be weakened. Furthermore, strictly controlling the -NCO content in the polyurethane hot melt adhesive obtained from the reaction, as well as its viscosity at a temperature of 100-120℃, is beneficial for improving the application temperature of the hot melt adhesive and ensuring good fluidity. When coated between the absorbent cotton layer and the waterproof layer of the nursing pad, it gives the nursing pad excellent peel strength and hot water wash resistance.

[0032] 2. This application uses polyester polyol and polyether polyol as the main raw materials, combined with tackifying resin, and reacts with isocyanate under the action of a catalyst to obtain polyurethane hot melt adhesive. The polyurethane hot melt adhesive is used between the waterproof layer and the absorbent layer of the nursing pad. The resulting nursing pad can be reused, and its peel strength can reach 170N / 10cm. It can withstand more than 100 washes in hot water at 90℃ without delamination. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of the preparation method of the polyurethane hot melt adhesive of this application. Detailed Implementation

[0034] 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 for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0035] Example

[0036] Example 1

[0037] The polyurethane hot melt adhesive comprises the following raw materials: 20 parts polyester polyol, 30 parts polyether polyol, 0.2 parts stabilizer, 25 parts tackifying resin, 0.01 parts catalyst, and 10 parts isocyanate.

[0038] The polyether polyol selected is polypropylene glycol with a weight average molecular weight of 1000, the tackifying resin is acrylic resin, the stabilizer is hindered phenolic antioxidant 1010, and the catalyst is dibutyltin dilaurate.

[0039] A method for preparing polyurethane hot melt adhesive includes the following steps:

[0040] Preparation of polyester polyol: 25 parts of terephthalic acid and 10 parts of 1,4-butanediol were added to a reaction vessel and heated to 210℃ to obtain a product with an acid value of 0.5 mg KOH / g. The reaction vessel temperature was then cooled to room temperature. 25 parts of octanoic acid and 5 parts of diethylene glycol were then added to the reaction vessel and heated to 225℃ to react. The vacuum pressure was 0.09±0.01 MPa. After the reaction was completed, the temperature was lowered. The obtained polyester polyol had a weight-average molecular weight of 1000, a hydroxyl value of 30 mg KOH / g, and an acid value of 0.2 mg KOH / g.

[0041] Mixing: First, put the polyester polyol, polyether polyol, and stabilizer into a sealed reactor and mix them. Heat the mixture to 120°C and stir for 10 minutes at a stirring speed of 100 rpm, and maintain the mixture under vacuum for 50-70 minutes. Then add the tackifying resin, adjust the stirring speed to 150 rpm, and stir continuously for 30 minutes to obtain the mixture.

[0042] Product preparation: The mixture was cooled to 80°C, the vacuum was broken, the stirring speed was adjusted to 100 rpm, the isocyanate and catalyst were quickly added, the stirring speed was then controlled at 150 rpm, the vacuum was drawn, and the reaction was carried out under a vacuum pressure of -0.09 MPa ± 0.01 to obtain polyurethane hot melt adhesive. The -NCO content of the obtained polyurethane hot melt adhesive reached 2 wt%, and its viscosity at 120°C was 3000 cps.

[0043] Example 2

[0044] The polyurethane hot melt adhesive comprises the following raw materials: 40 parts polyester polyol, 60 parts polyether polyol, 0.05 parts stabilizer, 10 parts tackifying resin, 0.1 parts catalyst, and 30 parts isocyanate.

[0045] The polyether polyol selected is polytetrahydrofuran ether diol-propylene oxide diol with a weight average molecular weight of 400. The tackifying resin is polyester resin, the stabilizer is hindered phenolic antioxidant 1010, and the catalyst is stannous octoate.

[0046] A method for preparing polyurethane hot melt adhesive includes the following steps:

[0047] Preparation of polyester polyol: 35 parts of isophthalic acid and 35 parts of propylene glycol were added to a reaction vessel and heated to 240℃ to obtain a product with an acid value of 1 mgKOH / g. The temperature of the reaction vessel was then cooled to room temperature. 35 parts of sebacic acid and 15 parts of diethylene glycol were then added to the reaction vessel and heated to 215℃ to react. The vacuum pressure was 0.09±0.01MPa. After the reaction was completed, the temperature was lowered. The obtained 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.

[0048] Mixing: First, put the polyester polyol, polyether polyol, and stabilizer into a sealed reactor and mix them. Heat the mixture to 120°C and stir for 10 minutes at a stirring speed of 100 rpm, and maintain the mixture under vacuum for 50-70 minutes. Then add the tackifying resin, adjust the stirring speed to 150 rpm, and stir continuously for 30 minutes to obtain the mixture.

[0049] Product preparation: The mixture was cooled to 100℃, the vacuum was broken, the stirring speed was adjusted to 100 rpm, the isocyanate and catalyst were quickly added, the stirring speed was then controlled at 150 rpm, the vacuum was drawn, and the reaction was carried out under a vacuum pressure of -0.09MPa±0.01 to obtain polyurethane hot melt adhesive. The -NCO content of the obtained polyurethane hot melt adhesive reached 5wt%, and its viscosity at 100℃ was 7000cps.

[0050] Example 3

[0051] The difference from Example 1 lies in the preparation of the polyester polyol: 30 parts of terephthalic acid and 20 parts of diethylene glycol were added to a reaction vessel, heated to 220°C, and reacted to obtain a product with an acid value of 0.8 mg KOH / g. The reaction vessel temperature was then cooled to room temperature. 30 parts of 1,4-cyclohexanedicarboxylic acid and 10 parts of 1,4-butanediol were then added to the reaction vessel, heated to 220°C, and reacted under a vacuum pressure of 0.09 ± 0.01 MPa. After the reaction was completed, the temperature was lowered. The resulting polyester polyol had a weight-average molecular weight of 2000, a hydroxyl value of 100 mg KOH / g, and an acid value of 1 mg KOH / g; all other aspects were the same as in Example 1.

[0052] Example 4

[0053] The difference from Example 3 is that in the step of preparing polyester polyol, the aromatic dicarboxylic acid is phthalic anhydride and the aliphatic dicarboxylic acid is adipic acid. The resulting 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 are the same as in Example 3.

[0054] Example 5

[0055] The difference from Example 4 is that the polyurethane hot melt adhesive includes the following raw materials: 30 parts polyester polyol, 50 parts polyether polyol, 0.1 parts stabilizer, 22 parts tackifying resin, 0.07 parts catalyst, and 20 parts 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 are the same as in Example 4.

[0056] Example 6

[0057] 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 polytetrahydrofuran ether diol with a weight average molecular weight of 1500. All other aspects are the same as in Example 5.

[0058] Application examples

[0059] Application Example 1

[0060] A nursing pad includes a permeable layer, an absorbent layer, and a waterproof layer, wherein the absorbent layer and the waterproof layer are coated with a polyurethane hot melt adhesive prepared in Example 1.

[0061] Application Example 2

[0062] A nursing pad includes a permeable layer, an absorbent layer, and a waterproof layer, wherein the absorbent layer and the waterproof layer are coated with a polyurethane hot melt adhesive prepared in Example 2.

[0063] Application Example 3

[0064] A nursing pad includes a permeable layer, an absorbent layer, and a waterproof layer, wherein the absorbent layer and the waterproof layer are coated with a polyurethane hot melt adhesive prepared in Example 3.

[0065] Application Example 4

[0066] A nursing pad includes a permeable layer, an absorbent layer, and a waterproof layer, wherein the absorbent layer and the waterproof layer are coated with a polyurethane hot melt adhesive prepared in Example 4.

[0067] Application Example 5

[0068] A nursing pad includes a permeable layer, an absorbent layer, and a waterproof layer, wherein the absorbent layer and the waterproof layer are coated with a polyurethane hot melt adhesive prepared in Example 5.

[0069] Application Example 6

[0070] A nursing pad includes a permeable layer, an absorbent layer, and a waterproof layer, wherein the absorbent layer and the waterproof layer are coated with a polyurethane hot melt adhesive prepared in Example 6.

[0071] Comparative Example

[0072] Comparative Example 1

[0073] The difference from Example 6 is that the polyester polyol is replaced with polyethylene glycol in equal amounts, while the other raw material components and amounts are the same as in Example 6.

[0074] Comparative Example 2

[0075] 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 reaction vessel and heated to 210°C to react, resulting in a polyester polyol with an acid value of 3 mgKOH / g, a hydroxyl value of 20 mgKOH / g, and a weight-average molecular weight of 800. The other raw material components and amounts are the same as in Example 6.

[0076] Comparative Example 3

[0077] The difference from Example 6 is that no polyether polyol is added, while the other raw material components and amounts are the same as in Example 6.

[0078] Comparative Example 4

[0079] The difference from Example 6 is that no tackifying resin is added, while the amounts of the other raw material components are the same as in Example 6.

[0080] Application of comparative examples

[0081] Application Comparative Example 1

[0082] The difference from Example 6 is that the water-absorbing layer and the waterproof layer are coated with the polyurethane hot melt adhesive prepared in Comparative Example 1.

[0083] Application Comparative Example 2

[0084] The difference from Application Example 6 is that the water-absorbing layer and the waterproof layer are coated with the polyurethane hot melt adhesive prepared in Comparative Example 2.

[0085] Application Comparative Example 3

[0086] The difference from Application Example 6 is that the water-absorbing layer and the waterproof layer are coated with the polyurethane hot melt adhesive prepared in Comparative Example 3.

[0087] Application Comparative Example 4

[0088] The difference from Application Example 6 is that the water-absorbing layer and the waterproof layer are coated with the polyurethane hot melt adhesive prepared in Comparative Example 4.

[0089] Performance testing

[0090] 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 hot water at 90°C without delamination. The results are recorded in Table 1.

[0091] The peel strength test method is as follows: 1. Cut the nursing pad into 10*20cm pieces, select 10 pieces for each group, apply an equal amount of polyurethane hot melt adhesive between the waterproof layer and the absorbent layer of the nursing pad, and mark them. Use a tensile testing machine to perform the peel test, and record the average data.

[0092] The water wash resistance test method is as follows: Ten nursing pads coated with polyurethane hot melt adhesive are placed in a group, immersed in water at 90℃ and stirred at 100r / min for 20min. The samples are taken out and their appearance is observed and evaluated to check for any glue separation. The above water wash test is repeated until all samples show glue separation. The number of water washes when glue separation occurs for each sample is recorded, and the final average value is recorded.

[0093] Peeling strength (N / 10 cm) Water resistance number / number Application Example 1 157 108 Application Example 2 150 102 Application Example 3 166 113 Application Example 4 169 116 Application Example 5 170 117 Application Example 6 174 120 Comparative Application Example 1 134 95 Comparative Application Example 2 141 90 Comparative Application Example 3 138 97 Comparative Application Example 4 147 100

[0094] As can be seen from Application Examples 1-6 and Table 1, the hot melt adhesive prepared in Examples 1-6 of this application can effectively improve the peel strength of the nursing pad, which has excellent mechanical properties and excellent resistance to hot water washing. It can withstand more than 100 washes in hot water at 90°C without delamination, resulting in a reusable nursing pad, which can effectively reduce the cost of using the nursing pad.

[0095] Combining Application Example 6 and Comparative Application Examples 1-4 with Table 1, it can be seen that in Comparative Example 1, polyester polyol was replaced with polyethylene glycol in equal amounts; in Comparative Example 2, some preparation steps of polyester polyol were omitted; in Comparative Example 3, polyether polyol was not added; and in Comparative Example 4, tackifying resin was missing. The resulting polyurethane hot melt adhesives underwent significant changes in both molecular structure and viscosity, resulting in poor overall performance of the hot melt adhesives. Consequently, the peel strength of the corresponding products decreased, and the number of hot water washes was significantly reduced. This is because the polyester polyol obtained by the specific preparation steps of this application is strictly controlled, which helps to control the sensitivity of polyurethane hot melt adhesive to water. In addition, polyether polyol is used as the main raw material, combined with tackifying resin, and reacts with isocyanate under the action of a catalyst to obtain polyurethane hot melt adhesive. Strict control of the -NCO content in the polyurethane hot melt adhesive obtained by the reaction and the viscosity at a temperature of 100-120℃ helps to improve the service temperature of the hot melt adhesive and has good fluidity. When coated between the absorbent cotton layer and the waterproof layer of the nursing pad, it gives the nursing pad excellent peel strength and hot water washing resistance.

[0096] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A polyurethane hot melt adhesive, characterized in that, The raw materials include the following parts by weight: 20-40 parts polyester polyol, 30-60 parts polyether polyol, 0.05-0.2 parts stabilizer, 10-25 parts tackifying resin, 0.01-0.1 parts catalyst, and 10-30 parts isocyanate; the polyester polyol has a weight-average molecular weight of 2000-4000, an acid value of 1-1.5 mgKOH / g, and a hydroxyl value of 80-100 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℃; The tackifying resin is selected from terpene resin and polyester resin in a mass ratio of 1:1, and the polyether polyol is selected from polytetrahydrofuran ether diol with a weight average molecular weight of 1500. The preparation method of the polyurethane hot melt adhesive includes the following steps: Preparation of polyester polyol: Aromatic diacid and diol are heated to react, yielding a product with an acid value of 0.5-1 mg KOH / g, which is then cooled to room temperature. Aliphatic diacid and diol are added, and the mixture is heated to 200-230℃ to react. After the reaction is complete, the mixture is cooled. Mixing: Polyester polyol, polyether polyol, stabilizer, and tackifying resin are mixed, heated, stirred, and maintained under vacuum for 50-70 minutes. Product preparation: After cooling and breaking the vacuum, isocyanate and catalyst are added, and the mixture is reacted under vacuum to obtain the polyurethane hot melt adhesive. By weight, the polyester polyol comprises 25-35 parts of aromatic dicarboxylic acid, 25-35 parts of aliphatic dicarboxylic acid, and 15-50 parts of diol. Aromatic dicarboxylic acids are phthalic anhydride and aliphatic dicarboxylic acids are adipic acid.

2. The polyurethane hot melt adhesive according to claim 1, characterized in that: The stabilizer is a hindered phenolic antioxidant.

3. The polyurethane hot melt adhesive according to claim 1, characterized in that: The diol includes one of diethylene glycol, 1,4-butanediol, and propylene glycol.

4. The polyurethane hot melt adhesive according to claim 1, characterized in that: The vacuum pressure is from -0.1 MPa to -0.01 MPa.

5. A nursing pad, comprising a permeable layer, an absorbent layer, and a waterproof layer, characterized in that, The absorbent layer and the waterproof layer are coated with a polyurethane hot melt adhesive obtained according to any one of claims 1-4.

Images