Hot melt adhesive for folding disposable hygienic products and preparation method of hot melt adhesive

Abstract

The invention discloses a hot melt adhesive for folding disposable hygienic products and a preparation method thereof, and relates to the technical field of adhesives, the hot melt adhesive for folding is prepared from the following components by mass: 3-15% of a semi-crystalline polypropylene polymer, 15-40% of an amorphous polymer, 10-25% of a viscosity modifier, 40-60% of tackifying resin, and 0.1-2% of an antioxidant, the sum of the mass percentages of the components is 100%, and the mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1: (2-5). The hot melt adhesive disclosed by the invention has the characteristic that the bonding force is controllably attenuated along with time, has extremely low surface initial viscosity, and can be applied to folding parts of disposable hygienic products such as baby diapers, training pants, female sanitary napkins, adult incontinence products and the like.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a hot melt adhesive for folding disposable hygiene products and its preparation method. Background Technology

[0002] In the production of disposable hygiene products, the products often need to be folded for ease of packaging, storage, and transportation. Examples include the sealing tape on individual hygiene product packaging bags and the adhesive at the folded edges of diaper back flaps. Figure 1 Folds require hot melt adhesive for bonding and securing to prevent them from coming undone during storage and transportation, thus maintaining the product's integrity. Existing hot melt adhesives for folding face a dilemma: if the initial adhesive strength is too low, effective and stable bonding cannot be achieved on high-speed production lines, and the folds may come unglued during storage and transportation due to vibration, pressure, or changes in temperature and humidity, leading to product failure; if the initial adhesive strength is too high, the force required to tear the folds when the consumer opens the product is excessive, easily tearing soft and thin substrates such as non-woven fabrics, PE films, or composite non-woven fabrics, producing debris or preventing complete and smooth unfolding, severely impacting user experience, product safety, and brand image. Furthermore, if the hot melt adhesive surface is too sticky, it may adhere to the user's skin or clothing, causing discomfort, pain, or even skin redness and swelling. Therefore, existing methods for solving the above problems typically involve simply adjusting the type and amount of tackifying resins and waxes in existing hot melt adhesive formulations, or changing to different types of base polymers (such as EVA) to balance the tack. However, this approach often sacrifices one aspect for another. The actual required hot melt adhesive exhibits a static equilibrium relationship with temporal changes in adhesive strength. Existing hot melt adhesives for folding struggle to achieve the dynamic temporal change in performance, characterized by "strong initial adhesion and easy peeling later." Therefore, developing a specialized hot melt adhesive that can intelligently respond to time changes, automatically decays adhesive strength (peel strength) over time, and has extremely low surface tack has become a pressing technical challenge in this field. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, one of the objectives of the present invention is to provide a hot melt adhesive for folding disposable hygiene products.

[0004] The second objective of this invention is to provide a method for preparing hot melt adhesive for folding disposable hygiene products.

[0005] One of the objectives of this invention is achieved by the following technical solution: a hot melt adhesive for folding disposable hygiene products, prepared from the following components by mass percentage:

[0006] Semi-crystalline polypropylene polymer 3-15%

[0007] Amorphous polymers 15-40%

[0008] Viscosity modifier 10-25%

[0009] 40-60% tackifying resin

[0010] Antioxidant 0.1-2%,

[0011] The sum of the mass percentages of the above components is 100%.

[0012] The mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5).

[0013] Furthermore, the hot melt adhesive for folding disposable hygiene products is prepared from the following components by mass percentage:

[0014] Semi-crystalline polypropylene polymer 8-12%

[0015] Amorphous polymers 25-35%

[0016] Viscosity modifier 12-20%

[0017] 45-55% tackifying resin

[0018] Antioxidant 0.3-1%,

[0019] The sum of the mass percentages of the above components is 100%.

[0020] The mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5).

[0021] Furthermore, the hot melt adhesive for folding disposable hygiene products is prepared from the following components by mass percentage:

[0022] Semi-crystalline polypropylene polymer 8-10%

[0023] Amorphous random polypropylene copolymer 28-30%

[0024] Viscosity modifier 12-15%

[0025] Tackifying resin 48-52%

[0026] Antioxidant 0.3-1%,

[0027] The sum of the mass percentages of the above components is 100%, wherein the mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5), the molecular weight of the semi-crystalline polypropylene polymer is 45,000-75,000, the softening point is 89℃-100℃, and the viscosity modifier is composed of Fischer-Tropsch wax and polyethylene wax in a mass ratio of (1-3):1.

[0028] Furthermore, the semi-crystalline polypropylene polymer is selected from propylene homopolymers under the L-MODU series of trade names from Idemitsu Kosan Co., Ltd. of Japan, including one or a mixture of two or more of L-MODU S400, L-MODU S410, and L-MODU S600.

[0029] Furthermore, the amorphous polymer is selected from one or more of the following: amorphous α-olefin copolymers, random polypropylene copolymers, ethylene-vinyl acetate copolymers, ethylene-butene copolymers, and ethylene-octene copolymers;

[0030] The amorphous α-olefin copolymer is selected from one or more of TB0802 and TB0403 from Liaoyang Liaohua Qida Chemical Co., Ltd.

[0031] The random polypropylene copolymer is selected from one or more of ExxonMobil's Vistamaxx™ Performance Polymer 8380 and Vistamaxx™ Performance Polymer 8880.

[0032] Furthermore, the viscosity modifier is selected from one or more of polyethylene wax, Fischer-Tropsch wax, and microcrystalline wax, and the polyethylene wax is selected from one or more of the polyethylene waxes with the grades Q-112 and Q-115 from Qingdao Zhongsu High-Tech Materials Co., Ltd.

[0033] The Fischer-Tropsch wax is selected from one or more of the following: Fischer-Tropsch wax with brand name SX105 from Shanghai Jiarong Trading Co., Ltd., or Fischer-Tropsch wax with brand names TP-76 and TP-80B from Nanjing Tianshi New Material Technology Co., Ltd.

[0034] The microcrystalline wax is selected from one or more of the grades M-70 and 600 from Qingdao Zhongsu High-Tech Materials Co., Ltd.

[0035] Furthermore, the tackifying resin is selected from one or a mixture of two or more of C5 petroleum resin, C9 petroleum resin, dicyclopentadiene DCPD resin, coumarone-indene resin, styrene series resins, condensation resins, hydrocarbon petroleum resins and hydrogenated petroleum resins.

[0036] Furthermore, the antioxidant is selected from one or a mixture of two or more of antioxidant 1010, antioxidant 168, and antioxidant AT-626.

[0037] Furthermore, the hot melt adhesive used for folding disposable hygiene products is used to bond the first substrate and the second substrate, wherein both the first substrate and the second substrate are hydrophilic nonwoven fabric and / or PE film. In the initial stage of the two substrates being bonded, the peel strength of the hot melt adhesive is greater than 55 gf / inch in 1h. After the two substrates are bonded, the peel strength gradually decreases to 20-40 gf / inch. After the hot melt adhesive cools and solidifies, the initial circumferential bond is 0-1 N / inch.

[0038] The second objective of this invention is achieved by the following technical solution: a method for preparing a hot melt adhesive for folding disposable hygiene products, comprising the following steps:

[0039] S1: Confirm that the bottom valve of the reactor is closed, turn on the steam heater, start the agitator, and add the viscosity modifier and antioxidant;

[0040] S2: Raise the temperature of the reactor in step S1 to 140-155℃, add the semi-crystalline polypropylene polymer and the non-crystalline polymer, and stir until the polymer melts;

[0041] S3: Add the thickening resin evenly to the reactor in step S2, and mix thoroughly after all the thickening resin has melted.

[0042] S4: After vacuuming and stirring continuously for 1 hour in step S3, filter the molten material in the reactor.

[0043] S5: The molten material filtered in step S4 is passed through a cooling system and a drying system in sequence, and finally packaged to obtain hot melt adhesive for folding disposable sanitary products.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] The hot melt adhesive for folding in this invention is based on delayed crystallization technology. It can provide sufficiently high adhesion in the initial stage of lamination (within minutes) to ensure high-speed production efficiency and folding stability. Subsequently, its adhesion gradually and controllably weakens over time (several hours to tens of hours), thereby ensuring that end users can easily, smoothly, and silently tear open the folded part when opening the product, without damaging the substrate. At the same time, the final cured surface of the adhesive is smooth and has extremely weak adhesion, fundamentally avoiding the problem of the substrate being torn or sticking to skin / clothing.

[0046] The hot melt adhesive of this invention employs a unique delayed crystallization technology (a specific ratio of semi-crystalline polymers and amorphous polymers) to achieve controllable decay of adhesive strength over time, while maintaining extremely low initial surface tack. The hot melt adhesive produced by this invention can be applied to the folded sections of disposable hygiene products such as baby diapers, training pants, feminine hygiene products, and adult incontinence products. Attached Figure Description

[0047] Figure 1 This is a schematic diagram illustrating the application scenarios of hot melt adhesive in hygiene products.

[0048] Figure 2 This is a diagram showing the state of existing hot melt adhesives when they fail on sanitary products.

[0049] Figure 3 A photograph of the nonwoven fabric substrate being torn during peeling, which is a preferred comparative example 1 of the present invention.

[0050] Figure 4 This is a photograph of the nonwoven fabric of the preferred embodiment 2 of the present invention, showing that the substrate was not torn during peeling. Detailed Implementation

[0051] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0052] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0053] This invention provides a hot melt adhesive for folding disposable hygiene products, prepared from the following components by weight percentage:

[0054] Semi-crystalline polypropylene polymer 3-15%

[0055] Amorphous polymers 15-40%

[0056] Viscosity modifier 10-25%

[0057] 40-60% tackifying resin

[0058] Antioxidant 0.1-2%,

[0059] The sum of the mass percentages of the above components is 100%.

[0060] The mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5).

[0061] As a further preferred embodiment, the hot melt adhesive is prepared from the following components by mass percentage:

[0062] Semi-crystalline polypropylene polymer 8-12%

[0063] Amorphous polymers 25-35%

[0064] Viscosity modifier 12-20%

[0065] 45-55% tackifying resin

[0066] Antioxidant 0.3-1%,

[0067] The sum of the mass percentages of the above components is 100%.

[0068] The mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5).

[0069] As a further preferred embodiment, the hot melt adhesive is prepared from the following components by mass percentage:

[0070] Semi-crystalline polypropylene polymer 8-10%

[0071] Amorphous random polypropylene copolymer 28-30%

[0072] Viscosity modifier 12-15%

[0073] Tackifying resin 48-52%

[0074] Antioxidant 0.3-1%,

[0075] The sum of the mass percentages of the above components is 100%.

[0076] The mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5), and in this invention, a further preferred ratio is 1:(3-4). The semi-crystalline polypropylene polymer has a molecular weight of 45,000-75,000 and a softening point of 89℃-100℃. The viscosity modifier is composed of Fischer-Tropsch wax and polyethylene wax in a mass ratio of (1-3):1.

[0077] As a further preferred embodiment, the hot melt adhesive for folding disposable hygiene products is used to bond the first substrate and the second substrate, wherein both the first substrate and the second substrate are hydrophilic nonwoven fabric and / or PE film. In the initial stage of the two substrates being bonded, the peel strength of the hot melt adhesive is greater than 55 gf / inch in 1h. After the two substrates are bonded, the peel strength gradually decreases to 20-40 gf / inch. After the hot melt adhesive cools and solidifies, the initial circumferential bond is 0-1 N / inch.

[0078] As a further preferred embodiment, the semi-crystalline polypropylene polymer is selected from propylene homopolymers under the L-MODU series trade names of Idemitsu Kosan Co., Ltd. of Japan, including one or a mixture of two or more of L-MODU S400 (molecular weight 45,000, softening point 93°C), L-MODU S410 (molecular weight 45,000, softening point 89°C), and L-MODU S600 (molecular weight 75,000, softening point 100°C). The use of polypropylene as the semi-crystalline polymer in this formulation can reduce surface tack to a certain extent.

[0079] As a further preferred embodiment, the amorphous polymer is selected from one or more of the following: amorphous α-olefin copolymers, random polypropylene copolymers, ethylene-vinyl acetate copolymers, ethylene-butene copolymers, and ethylene-octene copolymers;

[0080] The amorphous polymer in the formulation of this invention can be an amorphous α-olefin copolymer, a random polypropylene copolymer, an ethylene-vinyl acetate copolymer, an ethylene-butene copolymer, or an ethylene-octene copolymer, preferably an amorphous α-olefin copolymer or a random polypropylene copolymer. It has a low molecular weight and an amorphous structure, exhibiting characteristics such as cold resistance and fluidity, and can provide adhesive strength in the initial stage of bonding (within minutes). Simultaneously, the addition of the amorphous polymer can delay the crystallization of the hot melt adhesive.

[0081] The amorphous α-olefin copolymer is selected from one or more of TB0802 and TB0403 from Liaoyang Liaohua Qida Chemical Co., Ltd.

[0082] The random polypropylene copolymer is selected from one or more of ExxonMobil's Vistamaxx™ Performance Polymer 8380 and Vistamaxx™ Performance Polymer 8880.

[0083] As a further preferred embodiment, the viscosity modifier is selected from one or a mixture of two or more of polyethylene wax, Fischer-Tropsch wax, and microcrystalline wax. The viscosity modifier is used to enhance the fluidity of the colloid and regulate the solidification rate, while also reducing surface tack in this formulation. As the most preferred embodiment, a 2:1 ratio of Fischer-Tropsch wax to polyethylene wax is optimal. Practical experience has shown that if only polyethylene wax is used without Fischer-Tropsch wax, the surface tack will increase; conversely, if only Fischer-Tropsch wax is used without polyethylene wax, the hardness will increase.

[0084] The polyethylene wax is selected from one or a mixture of two or more polyethylene waxes with the grades Q-112 and Q-115 from Qingdao Zhongsu High-tech Materials Co., Ltd.

[0085] The Fischer-Tropsch wax is selected from one or more of the following: Fischer-Tropsch wax with brand name SX105 from Shanghai Jiarong Trading Co., Ltd., or Fischer-Tropsch wax with brand names TP-76 and TP-80B from Nanjing Tianshi New Material Technology Co., Ltd.

[0086] The microcrystalline wax is selected from one or more of the grades M-70 and 600 from Qingdao Zhongsu High-Tech Materials Co., Ltd.

[0087] As a further preferred embodiment, the tackifying resin is selected from one or a mixture of two or more of C5 petroleum resin, C9 petroleum resin, dicyclopentadiene DCPD resin, coumarone-indene resin, styrene series resins, condensation resins, hydrocarbon petroleum resins, and hydrogenated petroleum resins. The tackifying resin in the formulation of this invention is preferably a hydrogenated petroleum resin, and more preferably a hydrogenated C9 petroleum resin, which can improve the peel strength of the hot melt adhesive and also impart a certain initial tack to the hot melt adhesive.

[0088] As a further preferred embodiment, the antioxidant is selected from one or a mixture of two or more of antioxidants 1010, 168, and AT-626. The role of the antioxidant in the formulation of this invention is to prevent polymer oxidation, which leads to macromolecular chain breakage, cross-linking, and performance degradation.

[0089] The method for preparing the hot melt adhesive for folding disposable hygiene products of the present invention includes the following steps:

[0090] S1: Confirm that the bottom valve of the reactor is closed, turn on the steam heater, start the agitator, and add the viscosity modifier and antioxidant;

[0091] S2: Raise the temperature of the reactor in step S1 to 140-155℃, add the semi-crystalline polypropylene polymer and the non-crystalline polymer, and stir until the polymer melts;

[0092] S3: Add the thickening resin evenly to the reactor in step S2, and mix thoroughly after all the thickening resin has melted.

[0093] S4: After vacuuming and stirring continuously for 1 hour in step S3, filter the molten material in the reactor.

[0094] S5: The molten material filtered in step S4 is passed through a cooling system and a drying system in sequence, and finally packaged to obtain hot melt adhesive for folding disposable sanitary products.

[0095] The following are specific embodiments of the present invention. Unless otherwise specified, the raw materials, equipment, etc. used in the following embodiments can all be obtained by purchase.

[0096] Examples 1-3 and Comparative Examples 1-9

[0097] Weigh the raw materials according to the proportions in Table 1, and prepare the pressure-sensitive adhesive according to the preparation method in Table 1 to obtain pressure-sensitive adhesives for different embodiments. See Table 1 for details:

[0098] Table 1 Raw material ratio table for Examples 1-3

[0099]

[0100] The hot melt adhesives in Examples 1-3 were prepared by the following steps:

[0101] S1: Confirm that the bottom valve of the reactor is closed, turn on the steam heater, start the agitator, and add the prescribed amount of viscosity modifier and antioxidant;

[0102] S2: Raise the temperature of the reactor in step S1 to 140-155℃, add the amount of semi-crystalline polypropylene polymer and non-crystalline polymer as specified in the formula, and stir until the polymer melts;

[0103] S3: Evenly add the formulated amount of thickening resin to the reactor of step S2, and mix thoroughly after all the thickening resin has melted;

[0104] S4: After vacuuming and continuous stirring for 1 hour, filter the molten material in the reactor.

[0105] S5: The molten material filtered in step S4 is passed through a cooling system and a drying system in sequence, and finally packaged to obtain hot melt adhesive for folding disposable sanitary products.

[0106] Comparative Example 1

[0107] Comparative Example 1 is a structural adhesive used in existing hygiene products, belonging to the SBC type hot melt pressure-sensitive adhesive. Its formulation is prepared from the following components by mass percentage: 6% of grade 1220 styrene-isoprene-styrene SIS, 12% of grade 791 styrene-butadiene-styrene SBS, 24% naphthenic oil, 59.6% hydrogenated DCPD petroleum resin, and 0.4% oxidant 1010.

[0108] Comparative Example 2

[0109] Comparative Example 2 is an existing EVA adhesive (non-crystalline material) used in hygiene products, which is formulated from the following components by mass percentage: 35% ethylene-vinyl acetate copolymer (EVA) of grade 28400, 15% paraffin wax, 49.6% hydrogenated DCPD petroleum resin, and 0.4% oxidant 1010.

[0110] Comparative Example 3

[0111] Compared with Example 2, the difference in Comparative Example 3 is that a highly crystalline polymer (high-density polyethylene) is used instead of the semi-crystalline polypropylene polymer S400, while the remaining formulation amounts and hot melt adhesive preparation methods are the same as in Example 2.

[0112] Comparative Example 4

[0113] Compared with Example 2, the difference in Comparative Example 4 is that the amount of amorphous polymer added is too large, that is, the mass ratio of semi-crystalline polypropylene polymer to amorphous polymer is 1:1. The other formulation amounts and hot melt adhesive preparation methods are the same as in Example 2.

[0114] Comparative Example 5

[0115] Compared with Example 2, the difference in Comparative Example 5 is that the amount of amorphous polymer added is too small, that is, the mass ratio of semi-crystalline polypropylene polymer to amorphous polymer is 1:6. The other formulation amounts and hot melt adhesive preparation methods are the same as in Example 2.

[0116] Comparative Example 6

[0117] Compared with Example 2, the difference in Comparative Example 6 is that the amount of viscosity modifier added is too large, that is, the viscosity modifier is 30% (the amount in the formulation is 10-25%), and the polymer content is reduced accordingly. The remaining formulation amounts and hot melt adhesive preparation methods are the same as in Example 2.

[0118] Comparative Example 7

[0119] Compared with Example 2, the difference in Comparative Example 7 is that the amount of viscosity modifier added is too small, that is, the viscosity modifier is 8% (the amount of formulation is 10-25%), and the polymer content is increased accordingly. The other formulation amounts and hot melt adhesive preparation methods are the same as in Example 2.

[0120] Comparative Example 8

[0121] Compared with Example 2, the difference in Comparative Example 8 is that the temperature of the reactor is too low in processing step S2, i.e., 130°C. The remaining formulation amounts and hot melt adhesive preparation methods are the same as in Example 2.

[0122] Comparative Example 9

[0123] Compared with Example 2, the difference in Comparative Example 9 is that the temperature of the reactor is too high in processing step S2, i.e., 160°C. The remaining formulation amounts and hot melt adhesive preparation methods are the same as in Example 2.

[0124] Effect evaluation and performance testing

[0125] The performance of the hot melt adhesives in Examples 1-3 and Comparative Examples 1-9 was tested. The test items and results are shown in Table 2.

[0126] 1. Viscosity testing methods

[0127] Viscosity was determined according to GB / T 2794 using a DV2TRVT viscometer and a No. 27 rotor from Bollefeld, USA. Results were recorded in centipoises (cps).

[0128] 2. Softening point test method

[0129] The softening point was tested according to GB / T 15332 using the SD-0606T automatic softening point tester from the Shanghai Institute of Geosciences Instrumentation. Results were recorded in degrees Celsius (°C).

[0130] 3. Shore A Hardness Test Method

[0131] Perform the test according to GB / T2411-2008. Press the hardness tester smoothly onto the sample, keeping the indenter parallel to the sample surface, and press the indenter vertically into the sample. The applied force should be just sufficient to make full contact between the indenter and the sample, and the reading should be taken within 1 second after the indenter and sample are in full contact.

[0132] 4. Peel strength test method

[0133] Hot melt adhesive was sprayed onto the hydrophilic nonwoven fabric at a rate of 3 g / m². 2 The sample was then laminated with a hydrophilic nonwoven fabric, and a 2-inch wide and 10-cm long sample was cut. The peel strength was tested at 1 hour and 24 hours. The results were recorded in gf / inch.

[0134] 5. Aging resistance test

[0135] The coated sample was placed at a constant temperature of 60℃ for 72 hours, and then removed to test its peel strength. This test used high-temperature accelerated aging, with time-temperature equivalence; placing it at 60℃ for 72 hours is equivalent to simulating six months of storage at room temperature.

[0136] 6. Circular Initial Tack Test Method

[0137] The ring tack was tested according to the specific provisions of the national standard GB / T31125—2014. The prepared hot melt adhesive was applied to the surface of a 30-micron thick high-transparency PET film using a coating applicator, a release film was attached, and the film was left at room temperature for 24 hours before the ring tack was tested. The results were recorded in N / inch.

[0138] Table 2 shows the hot melt adhesive performance test data for each embodiment.

[0139]

[0140] As shown in the table above, the hot melt adhesive for folding prepared in this invention is used to bond a first substrate and a second substrate, both of which are hydrophilic nonwoven fabrics and / or PE films. In practical applications, this hot melt adhesive exhibits the characteristics of strong initial adhesion and easy peeling later. Specifically, it provides sufficiently high adhesion (peel strength greater than 55 gf / inch after 1 hour) in the initial stage of the two substrate lamination process (within minutes), thereby ensuring high-speed production efficiency and folding stability. After the two substrates are laminated, their adhesion gradually and controllably weakens over time (from several hours to tens of hours) (i.e., the peel strength shows a decreasing trend after 24 hours, approximately 20-40 gf / inch), thus ensuring that end users can easily, smoothly, and silently tear open the folded portion when opening the product, without damaging the substrate. After the hot melt adhesive in the final product cures, the surface remains smooth and the tack is extremely weak (initial tack of the ring is 0-1 N / inch), fundamentally avoiding tearing during peeling (see...). Figure 4 It avoids the problem of sticking to skin or clothing, and its softness and hardness are moderate, which can meet the requirements of the softness and hardness of hygiene products.

[0141] The hot melt adhesive produced by this invention exhibits the aforementioned properties and can be applied to the folding parts of disposable hygiene products such as baby diapers, training pants, feminine hygiene products, and adult incontinence products. It effectively solves the dilemma of existing hot melt adhesives for folding and balances the performance requirements of hot melt adhesive processing with those of end-user applications.

[0142] Comparative Example 1 uses an existing structural adhesive formulation, whose polymer is mainly a rubber system. While the hardness and initial peel strength of Comparative Example 1 meet the application requirements, its strong surface adhesion makes it prone to tearing during peeling (see...). Figure 3 It can easily stick to skin or clothing.

[0143] Comparative Example 2 uses an existing EVA adhesive formula with a hardness of 85. This hardness is too high, affecting the feel of the diaper and making it unsuitable for skin-contact hygiene products. In contrast, the hot melt adhesive of this invention has a hardness of less than 70, meeting the requirements of current application scenarios.

[0144] Compared with Example 2, the formulation of Comparative Example 3 uses a highly crystalline polymer instead of the semi-crystalline polypropylene polymer S400. Although the hot melt adhesive obtained meets the glass strength or ring initial tack test, its hardness is greater than 85. The hot melt adhesive is too hard, which affects the end user's user experience and may even scratch the skin. It is also not suitable for skin-friendly hygiene products.

[0145] Compared to Example 2, the formulation of Comparative Example 4 contained an excessive amount of the amorphous polymer, resulting in a peel strength of 50-60 gf / inch after aging, which could lead to a risk of substrate damage in the product.

[0146] Compared with Example 2, the amount of amorphous polymer added in the formulation of Comparative Example 5 was too small, resulting in a peel strength of less than 55 gf / inch, which led to poor substrate adhesion during product processing.

[0147] Compared with Example 2, the viscosity modifier added in the formulation of Comparative Example 6 was too large, resulting in increased hardness and making it unsuitable for skin-friendly sanitary products.

[0148] Compared with Example 2, the amount of viscosity modifier added in the formulation of Comparative Example 7 was too small, resulting in increased surface stickiness and easy adhesion to skin or clothing.

[0149] Compared with Example 2, in Comparative Example 8, the temperature of the reactor was too low in processing step S2, which could not guarantee that the polymer would melt completely, seriously affecting the product performance indicators.

[0150] Compared to Example 2, in Comparative Example 9, the reactor temperature was too high in processing step S2, causing the polymer to degrade and the surface viscosity to increase.

[0151] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A hot melt adhesive for folding disposable sanitary products, characterized in that, It is prepared from the following components by mass percentage: Semi-crystalline polypropylene polymer 3-15% Amorphous polymers 15-40% Viscosity modifier 10-25% 40-60% tackifying resin Antioxidant 0.1-2%, The sum of the mass percentages of the above components is 100%. The mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5).

2. The hot melt adhesive for folding disposable sanitary products as described in claim 1, characterized in that, This hot melt adhesive is prepared from the following components by mass percentage: Semi-crystalline polypropylene polymer 8-12% Amorphous polymers 25-35% Viscosity modifier 12-20% 45-55% tackifying resin Antioxidant 0.3-1%, The sum of the mass percentages of the above components is 100%. The mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5).

3. The hot melt adhesive for folding disposable sanitary products as described in claim 1, characterized in that, This hot melt adhesive is prepared from the following components by mass percentage: Semi-crystalline polypropylene polymer 8-10% Amorphous random polypropylene copolymer 28-30% Viscosity modifier 12-15% Tackifying resin 48-52% Antioxidant 0.3-1%, The sum of the mass percentages of the above components is 100%, wherein the mass ratio of the semi-crystalline polypropylene polymer to the amorphous polymer is 1:(2-5), the molecular weight of the semi-crystalline polypropylene polymer is 45,000-75,000, the softening point is 89℃-100℃, and the viscosity modifier is composed of Fischer-Tropsch wax and polyethylene wax in a mass ratio of (1-3):

1.

4. The hot melt adhesive for folding disposable sanitary products as described in any one of claims 1-3, characterized in that, The semi-crystalline polypropylene polymer is selected from propylene homopolymers under the L-MODU series of trade names from Idemitsu Kosan Co., Ltd. of Japan, including one or a mixture of two or more of L-MODU S400, L-MODU S410, and L-MODU S600.

5. The hot melt adhesive for folding disposable sanitary products as described in any one of claims 1-3, characterized in that, The amorphous polymer is selected from one or more of the following: amorphous α-olefin copolymers, random polypropylene copolymers, ethylene-vinyl acetate copolymers, ethylene-butene copolymers, and ethylene-octene copolymers; The amorphous α-olefin copolymer is selected from one or more of TB0802 and TB0403 from Liaoyang Liaohua Qida Chemical Co., Ltd. The random polypropylene copolymer is selected from one or more of ExxonMobil's Vistamaxx™ Performance Polymer 8380 and Vistamaxx™ Performance Polymer 8880.

6. The hot melt adhesive for folding disposable sanitary products as described in any one of claims 1-3, characterized in that, The viscosity modifier is selected from one or more of polyethylene wax, Fischer-Tropsch wax, and microcrystalline wax. The polyethylene wax is selected from one or a mixture of two or more polyethylene waxes with the grades Q-112 and Q-115 from Qingdao Zhongsu High-tech Materials Co., Ltd. The Fischer-Tropsch wax is selected from one or more of the following: Fischer-Tropsch wax with brand name SX105 from Shanghai Jiarong Trading Co., Ltd., or Fischer-Tropsch wax with brand names TP-76 and TP-80B from Nanjing Tianshi New Material Technology Co., Ltd. The microcrystalline wax is selected from one or more of the grades M-70 and 600 from Qingdao Zhongsu High-Tech Materials Co., Ltd.

7. The hot melt adhesive for folding disposable sanitary products as described in any one of claims 1-3, characterized in that, The tackifying resin is selected from one or a mixture of two or more of the following: C5 petroleum resin, C9 petroleum resin, dicyclopentadiene DCPD resin, coumarone-indene resin, styrene series resins, condensation resins, hydrocarbon petroleum resins, and hydrogenated petroleum resins.

8. The hot melt adhesive for folding disposable sanitary products as described in any one of claims 1-3, characterized in that, The antioxidant is selected from one or a mixture of two or more of antioxidants 1010, antioxidant 168, and antioxidant AT-626.

9. The hot melt adhesive for folding disposable sanitary products as described in any one of claims 1-3, characterized in that, The hot melt adhesive used for folding disposable hygiene products is used to bond the first substrate and the second substrate. Both the first substrate and the second substrate are hydrophilic nonwoven fabric and / or PE film. In the initial stage of the two substrates being bonded, the peel strength of the hot melt adhesive is greater than 55 gf / inch in 1h. After the two substrates are bonded, the peel strength gradually decreases to 20-40 gf / inch. After the hot melt adhesive cools and solidifies, the initial circumferential bond is 0-1 N / inch.

10. A method for preparing a hot melt adhesive for folding disposable sanitary products as described in any one of claims 1-9, characterized in that, Includes the following steps: S1: Confirm that the bottom valve of the reactor is closed, turn on the steam heater, start the agitator, and add the viscosity modifier and antioxidant; S2: Raise the temperature of the reactor in step S1 to 140-155℃, add the semi-crystalline polypropylene polymer and the non-crystalline polymer, and stir until the polymer melts; S3: Add the thickening resin evenly to the reactor in step S2, and mix thoroughly after all the thickening resin has melted. S4: After vacuuming and stirring continuously for 1 hour in step S3, filter the molten material in the reactor. S5: The molten material filtered in step S4 is passed through a cooling system and a drying system in sequence, and finally packaged to obtain hot melt adhesive for folding disposable sanitary products.

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