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CN-122011998-A - High-initial-viscosity polyurethane hot melt adhesive and preparation method thereof

CN122011998ACN 122011998 ACN122011998 ACN 122011998ACN-122011998-A

Abstract

The invention discloses a high-initial-viscosity polyurethane hot melt adhesive and a preparation method thereof, and relates to the technical field of polyurethane hot melt adhesives. The modified composite tackifying system comprises 55-80 parts of compound polyester polyol, 3-8 parts of polyether polyol, 7-11 parts of isocyanate, 6-10 parts of modified composite tackifying system, 0.02-0.06 part of catalyst, 8-22 parts of ethylene-vinyl acetate copolymer and 0.3-1.5 parts of auxiliary agent, wherein the compound polyester polyol comprises crystalline polyester polyol, liquid polyester polyol and amorphous polyester polyol, and the modified composite tackifying system is a compound of silane coupling agent melt grafted modified rosin resin and hydroxylated nano composite filler. According to the invention, the core-shell type composite tackifying system of the silane coupling agent melt grafting modified rosin resin and the hydroxylated nano filler is arranged, so that the problems of most of modified tackifying systems in the prior art are simply mixed, the grafting rate is low and the nano filler is easy to agglomerate are solved, and the initial adhesion of the hot melt adhesive is obviously improved.

Inventors

  • Kang Chengwu

Assignees

  • 巢进化学(上海)有限公司

Dates

Publication Date
20260512
Application Date
20260304

Claims (9)

  1. 1. The high-initial-viscosity polyurethane hot melt adhesive is characterized by comprising, by weight, 55-80 parts of compound polyester polyol, 3-8 parts of polyether polyol, 7-11 parts of isocyanate, 6-10 parts of modified composite tackifying system, 0.02-0.06 part of catalyst, 8-22 parts of ethylene-vinyl acetate copolymer and 0.3-1.5 parts of auxiliary agent; The compound polyester polyol comprises crystalline polyester polyol, liquid polyester polyol and amorphous polyester polyol; The modified composite tackifying system is a compound of silane coupling agent melt grafting modified rosin resin and hydroxylated nano composite filler, the modification process is that the rosin resin reacts with the silane coupling agent for 30-40 minutes in a molten state at 80-90 ℃, the grafting rate is more than or equal to 90%, and then the rosin resin is compounded with the nano composite filler; The hydroxylated nano composite filler is selected from hydroxylated nano silicon dioxide with the particle size of 10-50 nm or hydroxylated graphene with the thickness of 1-5 nm, and the auxiliary agent at least comprises one of an antioxidant and a stabilizer; The hydroxyl-terminated group of the compound polyester polyol and the NCO group of isocyanate undergo an addition reaction to form a urea bond structure, a grafting functional group in the modified composite tackifying system and a VA unit of the ethylene-vinyl acetate copolymer form a hydrogen bond, and the nano composite filler constructs a three-dimensional supporting structure in the system, so that the initial adhesive force of the hot melt adhesive is more than or equal to 2.8N, and the cohesive strength retention rate of the hot melt adhesive after 60 hours of moisture and heat resistance is more than or equal to 98%.
  2. 2. The high initial adhesion polyurethane hot melt adhesive of claim 1, wherein the compounded polyester polyol comprises a crystalline polyester polyol, a liquid polyester polyol and an amorphous polyester polyol, wherein the crystalline polyester polyol has a weight average molecular weight of 3200 to 3800, the liquid polyester polyol has a weight average molecular weight of 3200 to 3800, and the amorphous polyester polyol has a weight average molecular weight of 1800 to 2200.
  3. 3. The high tack polyurethane hot melt adhesive of claim 1, wherein the polyether polyol comprises at least one of polytetrahydrofuran glycol, polyoxypropylene-oxyethylene copolymer glycol, and has a weight average molecular weight of 1800-2500.
  4. 4. The high initial adhesion polyurethane hot melt adhesive according to claim 1, wherein the isocyanate at least comprises one of isophorone diisocyanate, hexamethylene diisocyanate and 4, 4-diphenylmethane diisocyanate, and the NCO content is 30-45 wt%.
  5. 5. The high initial adhesion polyurethane hot melt adhesive according to claim 1, wherein the silane coupling agent in the modified composite adhesion system is selected from KH550 or KH560, the addition amount of the silane coupling agent is 3-8% of the mass of the rosin resin, and the addition amount of the hydroxylated nano-composite filler is 10-30% of the mass of the modified rosin resin.
  6. 6. The high initial adhesion polyurethane hot melt adhesive of claim 1, wherein the catalyst comprises at least one of dimorpholine diethyl ether, dibutyl tin dilaurate and stannous octoate, and the weight ratio of the organometallic catalyst to the amine catalyst is 1:1-2:1.
  7. 7. The high initial adhesion polyurethane hot melt adhesive according to claim 1, wherein the ethylene-vinyl acetate copolymer has a VA content of 55-85 wt%, and the VA content is adapted to the grafting ratio of the modified composite adhesion promoting system, so that the hydrogen bonding efficiency is not less than 85%.
  8. 8. A method for preparing a high initial adhesion polyurethane hot melt adhesive, which is used for preparing the high initial adhesion polyurethane hot melt adhesive according to any one of claims 1 to 7, and comprises the following steps: Firstly, putting the compound polyester polyol and polyether polyol into a reaction kettle, and drying and dehydrating for 40-70 min under the conditions of 125-135 ℃ and absolute pressure of less than or equal to 80Pa to obtain a dried material; Adding a modified composite tackifying system into the dried material, and pre-dispersing for 40-60 min at the temperature of 80-90 ℃ and the rotating speed of 900-1300 r/min to form a three-dimensional network precursor, wherein the pre-dispersing process needs to ensure that the hydroxylated nano composite filler is free from aggregation; Step three, adding an ethylene-vinyl acetate copolymer and an auxiliary agent into the three-dimensional network precursor, heating to 135-145 ℃, and carrying out vacuum dehydration for 80-110 min; And fourthly, cooling to 88-92 ℃, adding isocyanate and a catalyst, heating to 105-115 ℃, reacting for 50-80 min under the condition that absolute pressure is less than or equal to 80Pa, discharging, sealing and packaging to obtain the hot melt adhesive.
  9. 9. The preparation method of the high initial viscosity polyurethane hot melt adhesive according to claim 8, wherein the pre-dispersing process in the second step adopts the combination of mechanical stirring dispersion and ultrasonic auxiliary dispersion, the ultrasonic power is 300-500W, the ultrasonic time is 15-25 min, and the mono-dispersion proportion of the hydroxylation nano composite filler after dispersion is more than or equal to 90%.

Description

High-initial-viscosity polyurethane hot melt adhesive and preparation method thereof Technical Field The invention relates to the technical field of polyurethane hot melt adhesives, in particular to a high-initial-viscosity polyurethane hot melt adhesive and a preparation method thereof. Background The reactive polyurethane hot melt adhesive is prepared by heating and melting into fluid under the condition of inhibiting chemical reaction so as to facilitate coating, bonding the two adherends, agglomerating the adhesive layer to play a role of bonding, and then generating high-molecular polymer with high cohesive force by means of reaction and chain extension of moisture existing in air or attached to the surface of the adherends, so that the adhesive force, the heat resistance and the like are obviously improved. The adhesive has the characteristics of no solvent, rapid positioning during assembly and the like, and has the performances of water resistance, temperature resistance, creep resistance, moisture resistance, medium resistance and the like of the reactive adhesive. The adhesive uses NCO end-group prepolymer as base material, and is matched with thermoplastic resin which does not react with isocyanate group and additives of catalyst and filler, etc. so as to ensure that the product has longer applicable period and storage period. The PUR has the characteristics of higher high and low temperature resistance, low temperature resistance and bonding strength, no solvent, no toxicity and the like, thereby having wide application prospect in the industrial fields of furniture, automobiles, clothing, electronics and the like. However, these conventional polyurethane hot melt adhesives have low initial tackiness, and particularly when applied to the woodworking field, the initial tackiness and other properties need to be improved, so a high initial tackiness polyurethane hot melt adhesive and a preparation method thereof are now proposed to solve the problems. Disclosure of Invention Technical problem to be solved Aiming at the defects of the prior art, the invention provides a high initial viscosity polyurethane hot melt adhesive and a preparation method thereof, and solves the problems in the prior art. Technical proposal The high-initial-viscosity polyurethane hot melt adhesive is prepared from 55-80 parts by weight of compound polyester polyol, 3-8 parts by weight of polyether polyol, 7-11 parts by weight of isocyanate, 6-10 parts by weight of modified composite tackifying system, 0.02-0.06 part by weight of catalyst, 8-22 parts by weight of ethylene-vinyl acetate copolymer and 0.3-1.5 parts by weight of auxiliary agent. The preparation process of the modified composite tackifying system comprises the steps of adding rosin resin into a reaction kettle, heating to 80-90 ℃ to melt the rosin resin, adding a silane coupling agent (KH 550 or KH 560) according to 3-8% of the mass of the rosin resin, stirring for 30-40 minutes at a rotating speed of 500-800 rpm, enabling the silane coupling agent to undergo a melt grafting reaction with the rosin resin, ensuring that the grafting rate is more than or equal to 90%, realizing deep chemical modification, then cooling to 60-70 ℃, adding a hydroxylated nano-composite filler, wherein the hydroxylated nano-composite filler is selected from hydroxylated nano-silica with a particle size of 10-50 nm or hydroxylated graphene with a sheet thickness of 1-5 nm, continuing stirring for 60-90 minutes, and simultaneously adopting 300-500W ultrasonic to assist in dispersing for 15-25 minutes, so as to ensure that the nano-filler is uniformly dispersed in the modified rosin resin, thereby forming a stable core-shell composite system. The preparation process forms a covalent bond with the carboxyl of the rosin resin through the active group of the silane coupling agent and then forms an interaction with the hydroxyl of the hydroxylated nano filler, so that the dispersion stability and interface binding force of the composite system are obviously improved, and the performance unevenness caused by nano filler agglomeration is avoided. The weight ratio of the hot melt adhesive achieves the comprehensive aims of high initial adhesion, excellent cohesive strength and stable adhesive property of the hot melt adhesive. The usage of the compound polyester polyol is the highest, a basic adhesive skeleton is provided for the hot melt adhesive, sufficient action space is reserved for other functional components, the proper addition of the polyether polyol balances the flexibility and adhesive adaptability of the system, the decrease of cohesive strength caused by excessive usage is avoided, the usage of isocyanate is matched with the hydroxyl end content of the polyol, the sufficient crosslinking reaction is ensured, the usage of the modified compound tackifying system is compatible with the system compatibility, the structural integrity of other components is not damaged, the micro additio