A solvent-based thermoplastic polyurethane adhesive material and preparation method thereof and adhesive composition

Abstract

The present invention discloses a solvent-based thermoplastic polyurethane adhesive material, the raw materials of which include polyester polyol and diisocyanate, and the isocyanate index R is 0.99-1.04; the diisocyanate includes meta-isomers and para-isomers, and the meta-isomer accounts for 2.5-5% of the total mass of the diisocyanate. The isomer content of the diisocyanate in the raw material of the solvent-based thermoplastic polyurethane adhesive material of the present invention is under a specific ratio, which can effectively shorten the dissolution rate of the adhesive material in the solvent after activation while having high peel strength and heat resistance, effectively save the time required for the solvent-based thermoplastic polyurethane adhesive material to dissolve in the actual production process, and the improvement of the dissolution rate will not significantly affect the final adhesive key properties such as viscosity, peel strength and heat resistance.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a solvent-based thermoplastic polyurethane adhesive material and a preparation method thereof, and a solvent-based thermoplastic polyurethane adhesive composition containing the adhesive material. Background Art

[0002] Polyurethane is a type of macromolecular polymer whose main chain contains carbamate groups, also known as polyurethanes. It is mainly divided into two categories: polyester polyurethanes and polyether polyurethanes. In the 1850s, Bayer developed the Desmondurs (diisocyanates and polyisocyanates) series and the Desmopens (low molecular weight hydroxyl-terminated polyester polyols) series of products, and configured them into two-component solvent-based polyurethane adhesives according to a certain ratio. Due to the excellent properties of good bonding strength, water resistance, solvent resistance, low temperature resistance, and low temperature curing, the adhesive became the most popular adhesive at the time. According to the composition of the reaction components, polyurethane adhesives can be divided into polyisocyanate adhesives, polyurethane adhesives containing isocyanate groups and polyurethane adhesives containing hydroxyl groups.

[0003] At present, the application of polyurethane adhesives in industry is relatively mature, and it is widely used in the fields of various materials such as foam plastics, wood, ceramics, metals, glass and rubber. In the field of shoe adhesives, traditional chloroprene adhesives have been gradually replaced by polyurethane adhesives due to their shortcomings such as inability to resist plasticizer penetration and poor adhesion to new shoe materials such as PU leather. Thermoplastic polyurethane (TPU) hot melt adhesives have become the fastest growing hot melt adhesive variety in the field of clothing and footwear due to their excellent mechanical properties and wide processing temperature range. The commonly used thermoplastic polyurethane hot melt adhesives on the market are solid at room temperature and need to be activated at high temperature before they can become liquid for coating. The processing temperature is high, and the material is easily degraded during processing. In the field of footwear, granular hot melt adhesive materials are difficult to use. Solvent-based thermoplastic polyurethane adhesives have the advantages of low processing temperature, easy access, and high bonding strength, and are becoming more and more popular.

[0004] Existing studies have mostly improved the viscosity and peel strength of solvent-based thermoplastic polyurethane adhesives by adding other substances or modifying the raw materials, or reducing their activation temperature and other properties. For example, Guo Mengjiao et al. obtained a single-component polyurethane adhesive with high peel strength by adjusting the type of raw materials, isocyanate index and synthetic solvent (Guo Mengjiao, Guan Zhongxiang. Solvent-based single-component polyurethane adhesive [J]. Adhesion, 1996, 17 (2): 3.). Chinese patent CN109852321A discloses a solvent-based polyurethane hot melt adhesive material and a preparation method thereof, which reduces the activation temperature of the polyurethane hot melt adhesive by compounding a chain extender, thereby enhancing the maximum solid content of the product in the solvent and the bonding force of the hot melt adhesive. However, solvent-based polyurethane adhesives need to be dissolved in a solvent when used, and their dissolution rate in the solvent has a great influence on the actual production efficiency. At present, there is a lack of a solvent-based thermoplastic polyurethane adhesive that dissolves quickly in the solvent and has excellent performance. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a solvent-based thermoplastic polyurethane adhesive material and a preparation method thereof, and a solvent-based thermoplastic polyurethane adhesive composition comprising the adhesive material. The solvent-based thermoplastic polyurethane adhesive material obtained by the present invention not only has high peel strength and heat resistance, but also has a significantly improved activation and dissolution rate in the solvent compared with the current solvent-based thermoplastic adhesive, which helps to shorten the product production time.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a solvent-based thermoplastic polyurethane adhesive material, whose raw materials include polyester polyol and diisocyanate, and the isocyanate index R is 0.99-1.04; the diisocyanate includes meta-isomers and para-isomers, and the meta-isomers account for 2.5-5% of the total mass of the diisocyanate.

[0007] Preferably, the isocyanate index R is 1.0-1.03.

[0008] Preferably, the para-isomer of the diisocyanate includes one or more of 4,4'-diphenylmethane diisocyanate and 4,4'-dicyclohexylmethane diisocyanate.

[0009] Preferably, the meta-isomer of the diisocyanate includes one or more of 2,4'-diphenylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate and meta-xylylene diisocyanate.

[0010] Preferably, the polyester polyol is an aliphatic polyester polyol having a number average molecular weight of 2000-3500.

[0011] Preferably, the polyester polyol includes one or more of polyethylene adipate diol, polybutylene adipate diol, polyhexane adipate diol and polycaprolactone diol.

[0012] Further preferably, the solvent-based thermoplastic polyurethane adhesive material is made of the following raw materials in parts by weight:

[0013] Polyester polyol 80-90 parts

[0014] 8-18 parts of diisocyanate

[0015] Chain extender 1-2 parts.

[0016] More preferably, the chain extender includes one or more of 1,2-ethylene glycol, 1,3-propylene glycol, 1,4-butanediol and 1,6-hexanediol.

[0017] Further preferably, the raw material further comprises 0.2-0.4 parts by weight of a catalyst.

[0018] Further preferably, the catalyst includes one or more of an organic tin catalyst, a potassium hydroxylate catalyst, an organic heavy metal catalyst, a zinc hydroxylate catalyst and a titanate catalyst.

[0019] The second aspect of the present invention provides a method for preparing the solvent-based thermoplastic polyurethane adhesive material described in the above technical solution, comprising the following steps:

[0020] (1) Preheating diisocyanate to 40-70°C and preheating polyester polyol to 90-140°C;

[0021] (2) dispersing and mixing the raw materials preheated in step (1) respectively, and then pouring them into a screw extruder for reaction extrusion to obtain a first reactant;

[0022] (3) pelletizing the first reactant underwater, drying and aging to obtain a solvent-based thermoplastic polyurethane adhesive material.

[0023] Preferably, the preheating temperature of the diisocyanate in step (1) is 45-65°C.

[0024] Preferably, in step (1), the preheating temperature of the polyester polyol is 100-130°C.

[0025] Preferably, when the raw material further comprises a chain extender, step (1) further comprises preheating the chain extender to 40-70°C.

[0026] The third aspect of the present invention provides a solvent-based thermoplastic polyurethane adhesive composition, comprising the solvent-based thermoplastic polyurethane adhesive material described in the above technical solution or the solvent-based thermoplastic polyurethane adhesive material obtained by the preparation method described in the above technical solution, and a solvent.

[0027] Preferably, the solvent is selected from one or more of butanone, toluene, N,N-dimethylformamide and tetrahydrofuran.

[0028] The fourth aspect of the present invention provides the use of the solvent-based thermoplastic polyurethane adhesive material described in the aforementioned technical solution, the solvent-based thermoplastic polyurethane adhesive material obtained by the preparation method described in the aforementioned technical solution, or the solvent-based thermoplastic polyurethane adhesive composition described in the aforementioned technical solution in shoemaking.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The solvent-based thermoplastic polyurethane adhesive material provided by the present invention has an initial viscosity that can be controlled at 700-4000 (mpa.s / 23°C), an initial peel strength of 7-20N / mm, a viscosity retention rate after heat resistance of more than 60%, and a peel strength retention rate after heat resistance of more than 65%. The isomer content of diisocyanate in the raw material of the solvent-based thermoplastic polyurethane adhesive material of the present invention is under a specific ratio, which can effectively shorten the dissolution rate of the adhesive material in the solvent after activation while having high peel strength and heat resistance, effectively saving the time required for the solvent-based thermoplastic polyurethane adhesive material to dissolve in the actual production process, and the increase in the dissolution rate will not significantly affect the final viscosity, peel strength, heat resistance and other key properties of the adhesive material. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be described below in conjunction with embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments; and the structures or performances shown are only schematic and do not represent the entirety of the present invention. It should be noted that all other embodiments obtained by ordinary technicians in this field based on these embodiments of the present invention belong to the scope of protection of the present invention.

[0032] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions. In addition, any method and material similar to or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials described in the text are for demonstration purposes only.

[0033] Herein, the term "viscosity" refers to the solution viscosity of a solvent-based thermoplastic polyurethane adhesive material dissolved in a solvent. The term "dissolution rate" refers to the dissolution time of a certain amount of solvent-based thermoplastic polyurethane adhesive material in a solvent (methyl ethyl ketone is used as the solvent in the test) under certain conditions after activation.

[0034] The present invention provides a solvent-based thermoplastic polyurethane adhesive material, the raw materials of which at least include polyester polyol and diisocyanate, and the isocyanate index R is 0.99-1.04; the diisocyanate includes meta-isomers and para-isomers, and the meta-isomer accounts for 2.5-5% of the total mass of the diisocyanate. The raw materials preferably include one or more of a chain extender and a catalyst, and may also include antioxidants (such as antioxidant 1010, phosphite antioxidants), hydrolyzing agents (such as carbodiimide hydrolyzing agents) and other auxiliary agents. When the solvent-based thermoplastic polyurethane adhesive material of the present invention is prepared by a solvent method, it may also include relevant solvents suitable for the solvent method; when the solvent-based thermoplastic polyurethane adhesive material of the present invention is prepared by a non-solvent preparation method such as a screw extrusion method, the raw materials may not contain a solvent.

[0035] In the present invention, the isocyanate index R value of the raw material of the solvent-based thermoplastic polyurethane adhesive material is adjusted in the range of 0.99-1.04; the isocyanate index R value in the raw material is preferably 1.0-1.03. The present invention finds that by adjusting the isocyanate index R value, the residual -NCO group content in the reaction process of the solvent-based thermoplastic polyurethane adhesive material of the present invention can be controlled, and then the viscosity of the product solvent-based thermoplastic polyurethane adhesive material can be controlled. Specifically, when the isocyanate index R value of the raw material is 0.99-1.04, the initial viscosity of the solvent-based thermoplastic polyurethane adhesive material is in the range of 700-4000mpa.s / 23℃, and the viscosity range after one week of heat resistance can also be maintained in the range of 650-3000mpa.s / 23℃. When the R value exceeds the range specified by the present invention, the viscosity of the adhesive material of the present invention will change significantly, which is not suitable for actual production and use. In some specific embodiments of the present invention, the adhesive material of the present invention with a gradient viscosity can be obtained by pre-adjusting the isocyanate index R value of the raw material, for example, the adhesive material of the present invention with an initial viscosity of 700-1200 mPa.s, 1700-2500 mPa.s, and 3000-4000 mPa.s.

[0036] In some specific embodiments of the present invention, the solvent-based thermoplastic polyurethane adhesive material is made of the following raw materials in parts by weight: 80-90 parts of polyester polyol, 8-18 parts of diisocyanate and 1-2 parts of chain extender; preferably, the raw materials further include 0.2-0.4 parts by weight of a catalyst.

[0037] The present invention unexpectedly discovered that the meta-isomer and para-isomer in the diisocyanate in the raw material of the solvent-based thermoplastic polyurethane adhesive material in a specific ratio can effectively shorten the dissolution time of the solvent-based thermoplastic polyurethane adhesive material in the solvent after activation, and does not affect other key properties. In the present invention, the "meta-isomer" or "para-isomer" refers to the meta or para relationship between the two -NCO groups in the diisocyanate. In the present invention, the weight parts of the diisocyanate in the raw material can be 8, 9, 10, 12, 14, 15, 16, 18, etc.; preferably 10-14 parts; in some specific embodiments of the present invention, the weight parts of the diisocyanate in the raw material are 11.2, 11.6 and 11.7.

[0038] The para-isomers of the diisocyanate of the present invention include, but are not limited to, one or more of 4,4'-diphenylmethane diisocyanate (4,4'-MDI) and 4,4'-dicyclohexylmethane diisocyanate; in some embodiments of the present invention, the para-isomer may be 4,4'-diphenylmethane diisocyanate. The meta-isomers of the diisocyanate of the present invention include, but are not limited to, one or more of 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 2,4'-dicyclohexylmethane diisocyanate and meta-xylylene diisocyanate. The meta-isomers or para-isomers may be a mixture of two or more. In the present invention, the meta-isomer content in the diisocyanate is 2.5-5%, which may be 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.; in some specific embodiments of the present invention, the meta-isomer content is 2.5%, 3%. In actual production, mixtures such as MDI-50 can be used as raw materials.

[0039] In the present invention, the polyester polyol preferably has a number average molecular weight of 2000-3500, more preferably a polyester polyol with a number average molecular weight of 2500-3200, and further preferably a polyester polyol with a number average molecular weight of 3000. Within the number average molecular weight range of the polyester polyol described in the present invention, the resulting adhesive material has good wettability, cohesion and adhesion. The number average molecular weight of the polyester polyol has a significant effect on the molecular diffusion ability of the adhesive material before curing, the toughness of the cured product and the cross-linking density. The size of the number average molecular weight affects the molecular activity and the penetration and wetting ability of the glue, which is an important condition for forming good bonding; when it is lower than the number average molecular weight range of the polyester polyol described in the present invention, the molecular weight growth of the solvent-based thermoplastic polyurethane adhesive material is insufficient when it is cured, and the bonding strength is still poor; when it is higher than the number average molecular weight range of the polyester polyol described in the present invention, the wetting ability of the glue deteriorates. In the present invention, the polyester polyol includes but is not limited to one or more of polyethylene adipate glycol ester diol, polybutylene adipate glycol ester diol, polyhexane adipate glycol ester diol and polycaprolactone diol; in some specific embodiments of the present invention, the polyester polyol can be polybutylene adipate glycol ester diol. In the present invention, the weight parts of the polyester polyol in the raw material can be 80, 82, 83, 84, 85, 88, 90, etc.; preferably 84-88 parts; in some specific embodiments of the present invention, the weight parts of the polyester polyol in the raw material are 86.5, 86.3.

[0040] In the present invention, the chain extender includes but is not limited to one or more of 1,2-ethylene glycol (EG), 1,3-propylene glycol (PG), 1,4-butanediol (BG) and 1,6-hexanediol (HG); in some specific embodiments of the present invention, the chain extender can be 1,4-butanediol. In the present invention, the weight of the chain extender in the raw material can be 1, 1.2, 1.5, 1.6, 1.8, 2, etc.; preferably 1.4-1.6 parts; in some specific embodiments of the present invention, the weight of the chain extender in the raw material is 1.45, 1.5.

[0041] In the present invention, the catalyst includes but is not limited to one or more of an organic tin catalyst, a potassium hydroxy acid catalyst, an organic heavy metal catalyst, a zinc hydroxy acid catalyst and a titanate catalyst; in some specific embodiments of the present invention, the organic tin catalyst may be stannous octoate (T-9). In the present invention, the weight of the catalyst in the raw material is preferably 0.2-0.4; it may be 0.2, 0.25, 0.3, 0.35, 0.4, etc.; in some specific embodiments of the present invention, the weight of the catalyst in the raw material may be 0.3.

[0042] The second aspect of the present invention provides a method for preparing the solvent-based thermoplastic polyurethane adhesive material described in the above technical solution, comprising the following steps:

[0043] The present invention preheats the diisocyanate to 40-70°C and the polyester polyol to 90-140°C. In the present invention, the preheating temperature of the diisocyanate is preferably 45-65°C; the preheating temperature of the polyester polyol is preferably 100-130°C. When the raw materials of the adhesive material of the present invention also include a chain extender, the above steps also include preheating the chain extender to 40-70°C; the preheating temperature is preferably 45-65°C. It should be noted that the diisocyanate and the chain extender will react after being mixed and preheated, so when the raw materials of the adhesive material of the present invention contain both diisocyanate and chain extender, they need to be preheated separately. When the raw materials of the adhesive material of the present invention also include a catalyst, the catalyst does not need to be preheated.

[0044] After the raw materials are preheated, the present invention disperses and mixes the treated raw materials respectively and then pours them into a screw extruder for reaction extrusion to obtain a first reactant. In the present invention, the dispersed mixing can be performed using a mixing head. The present invention has no special restrictions on the order in which the raw materials enter the screw extruder, and all the raw materials can be poured into the screw extruder. In the present invention, the screw extruder preferably uses a twin-screw extruder.

[0045] After obtaining the first reactant, the present invention underwater pelletizes the first reactant, dries, and matures it to obtain a solvent-based thermoplastic polyurethane adhesive material. Specifically, after the first reactant is extruded from a twin-screw, it is underwater pelletized through a die head; the main purpose of the drying in the present invention is to remove water, and the drying temperature is preferably 55-70°C, more preferably 60°C; the maturation in the present invention can be carried out by hot air heating or the like, and the maturation temperature is preferably 45-60°C, more preferably 50°C.

[0046] According to the method provided by the present invention, a solvent-based thermoplastic polyurethane adhesive material with fast dissolution speed, strong bonding force and good peeling strength can be prepared.

[0047] The third aspect of the present invention provides a solvent-based thermoplastic polyurethane adhesive composition, comprising the solvent-based thermoplastic polyurethane adhesive material described in the above technical solution or the solvent-based thermoplastic polyurethane adhesive material obtained by the preparation method described in the above technical solution, and a solvent. The solvent-based thermoplastic polyurethane adhesive material described in the present invention needs to be used in conjunction with a solvent when used. The adhesive material and the solvent in the solvent-based thermoplastic polyurethane adhesive composition described in the present invention are usually independent of each other, and the two are mixed when used. In the present invention, the solvent includes but is not limited to one or more of butanone, toluene, N,N-dimethylformamide and tetrahydrofuran.

[0048] The fourth aspect of the present invention provides the use of the solvent-based thermoplastic polyurethane adhesive material described in the aforementioned technical solution, the solvent-based thermoplastic polyurethane adhesive material obtained by the preparation method described in the aforementioned technical solution, or the solvent-based thermoplastic polyurethane adhesive composition described in the aforementioned technical solution in shoemaking.

[0049] The technical solutions provided by the present invention are described in detail below in conjunction with the examples, but they should not be construed as limiting the scope of protection of the present invention. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0050] Example 1 Solvent-based thermoplastic polyurethane adhesive material 1

[0051] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.0:

[0052] 11.2 parts of diisocyanate, of which 10.864 parts are 4,4'-MDI and 0.336 parts are 2,4'-MDI, and 2,4'-MDI accounts for 3% of the total mass of diisocyanate;

[0053] Polybutylene adipate diol (number average molecular weight: 3000) 86.5 parts

[0054] 1,4-Butanediol (BG) 1.45 parts

[0055] 0.3 parts of stannous octoate.

[0056] Diisocyanate and 1,4-butanediol were preheated to 60°C, polybutylene adipate diol was preheated to 90°C, and stannous octoate was not preheated; the treated raw materials were dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 1.

[0057] Example 2 Solvent-based thermoplastic polyurethane adhesive material 2

[0058] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.02:

[0059] 11.6 parts of diisocyanate, of which 11.252 parts are 4,4'-MDI and 0.348 parts are 2,4'-MDI, and 2,4'-MDI accounts for 3% of the total mass of diisocyanate;

[0060] Polybutylene adipate diol (number average molecular weight: 3000) 86.3 parts

[0061] 1.5 parts of 1,4-butanediol

[0062] 0.3 parts of stannous octoate.

[0063] Diisocyanate and 1,4-butanediol were preheated to 60°C, polybutylene adipate diol was preheated to 90°C, and stannous octoate was not preheated; the treated raw materials were dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 2.

[0064] Example 3 Solvent-based thermoplastic polyurethane adhesive material 3

[0065] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.03:

[0066] 11.7 parts of diisocyanate, of which 11.349 parts are 4,4'-MDI and 0.351 parts are 2,4'-MDI, and 2,4'-MDI accounts for 3% of the total mass of diisocyanate;

[0067] Polybutylene adipate diol (number average molecular weight: 3000) 86.3 parts

[0068] 1.5 parts of 1,4-butanediol

[0069] 0.3 parts of stannous octoate.

[0070] Diisocyanate and 1,4-butanediol were preheated to 60°C, polybutylene adipate diol was preheated to 90°C, and stannous octoate was not preheated; the treated raw materials were dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 3.

[0071] Example 4 Solvent-based thermoplastic polyurethane adhesive material 4

[0072] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.02:

[0073] 11.6 parts of diisocyanate, of which 11.31 parts are 4,4'-MDI and 0.29 parts are 2,4'-MDI, and 2,4'-MDI accounts for 2.5% of the total mass of diisocyanate;

[0074] Poly(hexamethylene adipate diol) (number average molecular weight: 3000) 86.3 parts

[0075] 1.5 parts of 1,4-butanediol

[0076] 0.3 parts of stannous octoate.

[0077] Diisocyanate and 1,4-butanediol were preheated to 60°C, poly(hexanediol adipate) glycol was preheated to 90°C, and stannous octoate was not preheated; the treated raw materials were dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 4.

[0078] Example 5 Solvent-based thermoplastic polyurethane adhesive material 5

[0079] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.02:

[0080] 11.6 parts of diisocyanate, of which 11.02 parts are 4,4'-MDI and 0.58 parts are 2,4'-MDI, and 2,4'-MDI accounts for 5% of the total mass of diisocyanate;

[0081] Poly(hexamethylene adipate diol) (number average molecular weight: 3000) 86.3 parts

[0082] 1.5 parts of 1,4-butanediol

[0083] 0.3 parts of stannous octoate.

[0084] Diisocyanate and 1,4-butanediol were preheated to 60°C, poly(hexanediol adipate) glycol was preheated to 90°C, and stannous octoate was not preheated; the treated raw materials were dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 5.

[0085] Example 6 Solvent-based thermoplastic polyurethane adhesive material 6

[0086] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.01:

[0087] 8.6 parts of diisocyanate, of which 8.17 parts are 4,4'-MDI, 0.43 parts are MDI-50, and 2,4'-MDI accounts for 2.5% of the total mass of diisocyanate;

[0088] Polycaprolactone diol (number average molecular weight: 3500) 80 parts

[0089] 1 part 1,4-Butanediol

[0090] 0.3 parts of stannous octoate.

[0091] Diisocyanate and 1,4-butanediol were preheated to 60°C, polycaprolactone diol was preheated to 90°C, and stannous octoate was not preheated; the treated raw materials were dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 6.

[0092] Example 7 Solvent-based thermoplastic polyurethane adhesive material 7

[0093] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.0:

[0094] 11.2 parts of diisocyanate, of which 9.65 parts are 4,4'-dicyclohexylmethane diisocyanate and 7.35 parts are 2,3'-MDI, with 2,4'-MDI accounting for 3.5% of the total mass of diisocyanate;

[0095] Polyethylene adipate glycol (number average molecular weight: 3000) 86.5 parts

[0096] 1.45 parts of 1,4-butanediol

[0097] 0.3 parts of stannous octoate.

[0098] Diisocyanate and 1,4-butanediol were preheated to 60°C, polyethylene adipate glycol was preheated to 90°C, and stannous octoate was not preheated; the treated raw materials were dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 7.

[0099] Example 8 Solvent-based thermoplastic polyurethane adhesive material 8

[0100] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.03:

[0101] 12.6 parts of diisocyanate, including 6.5 parts of 4,4'-MDI, 5.596 parts of 4,4'-dicyclohexylmethane diisocyanate, and 0.504 parts of 2,4'-MDI, with 2,4'-MDI accounting for 4% of the total mass of diisocyanate;

[0102] 48 parts of polybutylene adipate diol (number average molecular weight: 2500), 41 parts of polyethylene adipate diol (number average molecular weight: 3200)

[0103] 2 parts of 1,6-hexanediol

[0104] 0.3 parts of stannous octoate.

[0105] The diisocyanate was preheated to 55°C, 1,6-hexanediol was preheated to 65°C, polybutylene adipate diol and polyethylene adipate diol were preheated to 120°C, but stannous octoate was not preheated. The treated raw materials were dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 8.

[0106] Example 9 Solvent-based thermoplastic polyurethane adhesive material 9

[0107] Take the following raw materials in parts by weight, the isocyanate index of the raw materials is R≈1.0:

[0108] 14.8 parts of diisocyanate, of which 14.356 parts are 4,4'-MDI and 0.444 parts are 2,4'-MDI, and 2,4'-MDI accounts for 3% of the total mass of diisocyanate;

[0109] Polybutylene adipate diol (number average molecular weight: 2000) 86.5 parts

[0110] 1.45 parts of 1,4-butanediol

[0111] 0.3 parts of stannous octoate.

[0112] Diisocyanate and 1,4-butanediol are preheated to 60°C, polybutylene adipate diol is preheated to 90°C, and stannous octoate is not preheated; the treated raw materials are dispersed and mixed in a stirring mixing head, poured into a twin-screw reaction extruder for reaction extrusion, and then pelletized underwater, dehydrated, dried and aged to obtain a solvent-based thermoplastic polyurethane adhesive material 9.

[0113] Comparative Example 1 Comparative Adhesive Material 1

[0114] Except that all diisocyanates were 4,4'-MDI, other raw materials and preparation methods were the same as those in Example 2, and a comparative adhesive material 1 was obtained.

[0115] Comparative Example 2 Comparative Adhesive Material 2

[0116] Except that all diisocyanates were 2,4'-MDI, other raw materials and preparation methods were the same as those in Example 2, and a comparative adhesive material 2 was obtained.

[0117] Comparative Example 3 Comparative Adhesive Material 3

[0118] Except that the diisocyanate is composed of 4,4'-MDI and 2,4'-MDI in a mass ratio of 90:10, other raw materials and preparation methods are the same as those in Example 4, and a comparative adhesive material 3 is obtained.

[0119] Comparative Example 4 Comparative Adhesive Material 4

[0120] Except that the diisocyanate is composed of 4,4'-MDI and 2,4'-MDI in a mass ratio of 99:1, other raw materials and preparation methods are the same as those in Example 4, and a comparative adhesive material 4 is obtained.

[0121] Experimental Example 1

[0122] 1. Experimental objects: solvent-based thermoplastic polyurethane adhesive material 2, comparative adhesive material 1 and comparative adhesive material 4 obtained in Example 2.

[0123] 2. Experimental methods:

[0124] The hardness of the test object is directly tested according to the following test standards without dissolving. The test object is dissolved in butanone to a solid content of 15% to obtain the test solution, and the minimum activation temperature, dissolution rate after activation, initial viscosity, viscosity after 70°C heat resistance for one week, and viscosity retention rate after heat resistance are tested. The test temperature for the above tests is 23°C. With PVC / PVC as the bonding substrate, the initial peel strength, peel strength after heat resistance, and peel strength retention rate of the test object are tested. The test results are shown in Table 1.

[0125] (1) Material hardness test method: ASTM D2240 standard is used for testing.

[0126] (2) Minimum activation temperature detection method: Determine and record the lowest temperature at which each experimental object changes from a solid state to a molten state.

[0127] (3) Dissolution rate detection method after activation: After activation at the lowest activation temperature, record the time required for each experimental object to dissolve naturally at 23°C.

[0128] (4) Initial viscosity detection method: The viscosity of each experimental object at 23°C was tested using a rotational viscometer.

[0129] (5) Viscosity testing method after one week of heat treatment at 70°C: After each test object is placed at 70°C for one week, the viscosity of each test object after heat treatment at 23°C is tested using a rotational viscometer.

[0130] (6) Initial peel strength test method: ASTM D1876 standard is used for testing.

[0131] (7) Post-heat-resistant peel strength retention rate test method: After each test object is placed at 70° C. for one week, each test object after heat treatment is tested using the ASTM D1876 standard.

[0132] 3. Experimental results

[0133] Table 1

[0134]

[0135]

[0136] It can be seen from the data in Table 1 that the dissolution rate after activation is too slow when the diisocyanate does not contain the meta-isomer 2,4'-MDI or contains only a small amount of the meta-isomer 2,4'-MDI. In addition, the initial viscosity and the viscosity after heat resistance of the adhesive materials of Comparative Examples 1 and 4 are too high. The high viscosity is difficult to control, which is not conducive to the subsequent sizing and coating of the product. Therefore, it is not suitable for practical use.

[0137] Experimental Example 2

[0138] 1. Experimental objects: solvent-based thermoplastic polyurethane adhesive material 2, comparative adhesive material 2 and comparative adhesive material 3 obtained in Example 2.

[0139] 2. Experimental methods:

[0140] The experimental objects were tested according to the method of Experimental Example 1, and the test results are shown in Table 2.

[0141] 3. Experimental results

[0142] Table 2

[0143]

[0144]

[0145] It can be seen from the data in Table 2 that when the proportion of the meta-isomer in the diisocyanate exceeds the proportion of the present invention, although the dissolution rate is high, the obtained adhesive materials 2 and 3 have low viscosity retention rates and peel strength retention rates after heat resistance, and the heat resistance is poor, which cannot meet the actual application requirements in the field of shoemaking.

[0146] Experimental Example 3

[0147] 1. Experimental object: solvent-based thermoplastic polyurethane adhesive materials 1-3 obtained in Examples 1-3 (the isocyanate indexes of Examples 1-3 are different, that is, the amount of polyester polyol used is the same, and only the amount of diisocyanate used is different).

[0148] 2. Experimental methods:

[0149] The experimental objects were tested according to the method of Experimental Example 1, and the test results are shown in Table 3.

[0150] 3. Experimental results

[0151] Table 3

[0152]

[0153]

[0154] It can be seen from the data in Table 3 that with the increase of the isocyanate index, the initial viscosity of the solvent-based thermoplastic polyurethane adhesive 1-3 shows a gradient upward trend, and there is no significant change in its dissolution rate, heat resistance, peel strength, etc. In actual production, the viscosity of the final product can be controlled by adjusting the isocyanate index of the raw material to achieve viscosity control.

[0155] Experimental Example 4

[0156] 1. Experimental object: solvent-based thermoplastic polyurethane adhesive material obtained in Examples 4-9.

[0157] 2. Experimental methods:

[0158] The experimental objects were tested according to the method of Experimental Example 1, and the test results are shown in Table 4.

[0159] 3. Experimental results

[0160] Table 4

[0161]

[0162]

[0163] Example 10

[0164] An adhesive composition comprises independently packaged solvent-based thermoplastic polyurethane adhesive material 2 and butanone.

[0165] Embodiment 11

[0166] An adhesive composition comprises independently packaged solvent-based thermoplastic polyurethane adhesive material 3 and tetrahydrofuran.

[0167] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A solvent-based thermoplastic polyurethane adhesive material, characterized in that: Its raw materials include polyester polyol and diisocyanate, and the isocyanate index R is 0.99-1.04; The diisocyanate includes meta-isomers and para-isomers, and the meta-isomer accounts for 2.5-5% of the total mass of the diisocyanate; The para-isomer of the diisocyanate includes one or more of 4,4'-diphenylmethane diisocyanate and 4,4'-dicyclohexylmethane diisocyanate; The meta-isomer of the diisocyanate includes one or more of 2,4'-diphenylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate and meta-xylylene diisocyanate; The polyester polyol is an aliphatic polyester polyol with a number average molecular weight of 2500-3500.

2. The solvent-based thermoplastic polyurethane adhesive material according to claim 1, characterized in that: The isocyanate index R is 1.0-1.

03.

3. The solvent-based thermoplastic polyurethane adhesive material according to claim 1, characterized in that: The polyester polyol includes one or more of polyethylene adipate diol, polypropylene adipate diol, polybutylene adipate diol, polyhexane adipate diol and polycaprolactone diol.

4. The solvent-based thermoplastic polyurethane adhesive material according to any one of claims 1 to 3, characterized in that: Made from the following raw materials in parts by weight: Polyester polyol 80-90 parts 8-18 parts of diisocyanate Chain extender 1-2 parts.

5. The solvent-based thermoplastic polyurethane adhesive material according to claim 4, characterized in that: The chain extender includes one or more of 1,2-ethylene glycol, 1,3-propylene glycol, 1,4-butanediol and 1,6-hexanediol.

6. The solvent-based thermoplastic polyurethane adhesive material according to claim 4, characterized in that: The raw materials also include 0.2-0.4 parts by weight of a catalyst.

7. The solvent-based thermoplastic polyurethane adhesive material according to claim 6, characterized in that: The catalyst includes one or more of an organic tin catalyst, a potassium hydroxylate catalyst, a zinc hydroxylate catalyst and a titanate catalyst.

8. A method for preparing the solvent-based thermoplastic polyurethane adhesive material according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Preheat diisocyanate to 40-70°C and preheat polyester polyol to 90-140°C; (2) the raw materials preheated in step (1) are dispersed and mixed respectively, and then poured into a screw extruder for reaction extrusion to obtain a first reactant; (3) Underwater pelletizing the first reactant, drying and aging it to obtain a solvent-based thermoplastic polyurethane adhesive material.

9. A method for preparing the solvent-based thermoplastic polyurethane adhesive material according to claim 8, characterized in that: In step (1), the preheating temperature of the diisocyanate is 45-65°C.

10. A method for preparing the solvent-based thermoplastic polyurethane adhesive material according to claim 8, characterized in that: In step (1), the preheating temperature of the polyester polyol is 100-130°C.

11. A method for preparing the solvent-based thermoplastic polyurethane adhesive material according to claim 8, characterized in that: When the raw materials further include a chain extender, step (1) further includes preheating the chain extender to 40-70°C.

12. A solvent-based thermoplastic polyurethane adhesive composition, characterized in that: The invention comprises the solvent-based thermoplastic polyurethane adhesive material according to any one of claims 1 to 7 or the solvent-based thermoplastic polyurethane adhesive material obtained by the preparation method according to any one of claims 8 to 11, and a solvent.

13. A solvent-based thermoplastic polyurethane adhesive composition according to claim 12, characterized in that: The solvent is selected from one or more of butanone, toluene, N,N-dimethylformamide and tetrahydrofuran.

14. Use of the solvent-based thermoplastic polyurethane adhesive material according to any one of claims 1 to 7, the solvent-based thermoplastic polyurethane adhesive material obtained by the preparation method according to any one of claims 8 to 11, or the solvent-based thermoplastic polyurethane adhesive composition according to any one of claims 12 to 13 in shoemaking.

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