7. Adhesive process for polyurethane adhesives for shoes
Bonding technology is one of the key technologies in the production of shoes. The success or failure of bonding technology directly affects the quality of shoes and their wearing life. The quality of bonding depends mainly on the composition and preparation of the adhesive, and the bonding process cannot be ignored.
1. Preparation of glue
(1) Solvent composition The preparation of the glue solution should strictly select the appropriate solvent. The first consideration is the solubility of the polyurethane colloidal particles in the solvent and the volatility of the solvent itself. Solubility can be determined based on the principle of similar solubility parameters. The volatilization rate of the solvent is appropriate, depending on the adhesive process. The volatilization rate is too fast, it is easy to conjunctiva on the surface of the adherend and hinder the continuous evaporation of the internal solvent. When the humidity in the air is high, the volatilization of heat is absorbed, and the water droplets are easily condensed on the surface, which affects the bonding quality. Mixed solvents are generally used, because the first one is to increase the solubility of the polymer in the solvent, so that it is in the best state; the second is to adjust the usable time of the adhesive by means of a solvent with a combination of the evaporation rate and the boiling point. In practical use, the toxicity and price of the solvent must also be considered. The physical properties of organic solvents commonly used in the preparation of footwear polyurethane adhesives are shown in Table 8 below.
Table 8 Physical Properties of Common Organic Solvents Used in Formulating Footwear Polyurethane Emulsions
Solvent name
Solubility parameter, SP
Polarity score, P
Boiling point, °C
Volatilization rate, min
acetone
Ethyl acetate
Butanone
Toluene
Cyclohexanone
9.4
9.1
9.2
8.9
10.1
0.695
0.167
0.510
0.001
0.380
58.5
77.2
79.6
110.6
155.6
3.5
4.3
5.4
6.6
14.6
Note: The polyurethane solubility parameter is 10.
* Determination of the volatilization rate is the time (min) at which 5 g of solvent is completely volatilized at 58°C.
The composition of mixed solvents used in the preparation of footwear polyurethane adhesives (mass ratio) is as follows:
1 Toluene: Butanone: Acetone: 35:25:25
2 Toluene: Butanone: Cyclohexanone: 35:30:15
3 Toluene: Butanone: Ethyl Acetate: 5:2:3
4 Butanone: Acetone: l:1
5 Butanone: Acetone: Cyclohexanone: 50:33:2
6 Butanone: Acetone: Ethyl acetate two 25:30:30
7 Acetone: Ethyl acetate two 65:17
(2) Solid content About the solid content (%) in the glue, the manufacturers of polyurethane adhesives for shoes in China are generally controlled at about 15%, while the foreign manufacturers are generally controlled at about 18%. The solids in the glue, mainly polyurethane elastic rubber particles, in addition to other additives added. For example, 1% of white carbon black is added to the formulation recommended by Bayer in Germany (the above-mentioned No. 7 mixed solvent plus Desmocoll 54017 parts, fumed silica l parts).
(3) Viscosity The viscosity of footwear polyurethane adhesives is generally 1200-2000 mPa·s (25°C).
2. Bonding process
(1) Upper and sole treatment Uppers (shoe uppers) If the leather is to be mechanically roughened, PVC artificial leather and PU synthetic leather may be painted with a treatment agent, and then coated after being dried. Sole (outsole) can be treated with TCCA chlorination if it is rubber, TPR, imitation leather, or pork skin. PU, PVC, EVA soles are treated with a primer.
(2) PU coated uppers and shoe soles must be painted evenly with PU adhesive, and the general coating is 0.2-0.5mm. The amount of glue applied to each pair of shoes is 18-26g (18-26g/double shoe sole and 10-14g/double shoe upper). After the glue is allowed to dry naturally for 30 minutes or the infrared lamp is dried at 50°C for 20 minutes, then heat-activated by 70-80°C for a few minutes (the gel layer is transparent), the pressure can be applied, and the air pressure (the shoes require 0.5— 0.6 MPa pressure) 20 seconds, after finishing, inspection and storage.
Polyurethane paper plastic compound
Paper-plastic composite refers to the combination of printing color printing paper and plastic film to form a paper-plastic film. The plastic film used is a polypropylene film or a polyester film, and a general adhesive is difficult to bond, and a satisfactory result can be obtained with a polyurethane adhesive. General-purpose polyurethane adhesives are used in paper-plastic composite films with high quality requirements and can be used in hot and humid environments. Now we will introduce the preparation method for the paper-plastic composite polyurethane adhesive prepared by using TDI modified castor oil as the main agent (A component) and TMP-TDI adduct as the curing agent (Part B).
1. Preparation method
(1) Castor oil dehydration and finely-divided castor oil was dehydrated under vacuum at 12°C and 1.3 kPa for 2 hours, and the water content was determined to be 0.08%.
(2) castor oil-TDI modified (main agent) 61.5kg of dehydrated castor oil was added to the reactor, the stirrer was started, the material was heated to 45-50°C, and 9.4kg of TDI was slowly added (80/ 20) After reacting at 70° C. for 3 hours, 23 kg of ethyl acetate and 34.5 kg of toluene are added, and the mixture is stirred for half an hour before discharging to obtain a castor oil-TDI modification (main agent or a component). The appearance is light yellow and transparent. The viscous liquid has a viscosity of 65-100 mPa·s (25°C) and a solids content of 55%.
(3) TMP-TDI adduct (curing agent) 35.3 kg of ethyl acetate (less than 0.1% moisture) and 52.2 kg of TDI (80/20) were added to the reactor, and the stirrer was turned on, and the temperature was raised to 50°C. , Slowly add 13.4kg of pre-melted trimethylolpropane (TMP), control the reaction temperature at 70°C, discharge at 70-75°C for 1h, and prepare the TMP-TDI adduct (curing agent or B Component), the appearance of light yellow or colorless transparent viscous liquid, viscosity 1000-1500mdPa · s (25 °C), solid content of 65%.
2. Adhesive formulation and performance
When the adhesive is used, it is prepared according to Part A: Part B = 4:1 (parts by mass), and then diluted with 3 parts by mass of toluene of the glue (working glue concentration is 15%). Paper-polypropylene film peel strength> 4N/cm.
Paper-plastic composite film is mainly used for book covers, packaging cartons, art calendars, maps, etc. The products are exquisite in appearance, but also have the advantages of waterproof, abrasion resistance, etc., and are widely used by users.
Polyurethane construction adhesive
Civil engineering adhesives can be divided into structural adhesives, universal adhesives, and sealants. There are many types of products used in civil construction. Here, we mainly introduce a series of adhesives for making water conservancy projects using castor oil and toluene isocyanate as raw materials.
In the construction of water conservancy projects, water conservancy projects such as dams, aqueducts, reservoirs, culverts, channels, and pipelines are filled with expansion joints during construction, joints of various pipelines are bonded, and leakage and leakage of water transmission projects are prevented. Hydraulic steel gate anti-corrosion, especially in the maintenance of water conservancy production cracks, leaks, repair, urgent need for a good performance, low-cost adhesive to meet the water conservancy project large-scale, large-scale promotion of use. The adhesives used over the years include petroleum asphalt and its modified products, coal tar and its modified products, epoxy resins and their modified products, as well as various waterproof ointment and some inorganic adhesives, but these products have some performance owed. Good, such as insufficient bonding strength, high and low temperature susceptibility to mutation, brittle cracking, aging, etc., are not ideal for use; some are expensive and difficult to promote in large areas in water conservancy projects. The low cost castor oil is used as the raw material, and the polyurethane adhesive obtained is applied in a number of water conservancy projects. It has the characteristics of good performance, low price, and is widely popularized and applied.
1. Concrete pipe anti-seepage adhesive
1. Preparation
Adhesive Formula A main agent: curing agent: coal tar: cement: toluene = l: 0.01-1: 0.2-1: 0.5-2.5: 0.4-2 (mass fraction).
A main agent formula castor oil: TDI: toluene = 25-45: 5-25: 30-70 (mass fraction).
The curing agent formula toluene diamine: acetone = 1: 5-20 (mass fraction).
According to the formula of a main agent, a certain amount of finely-divided castor oil is added into the reactor, heated and dehydrated, the temperature is 110-150° C., the vacuum degree is greater than 0.08 MPa (gauge pressure), the dehydration time is l-4 h, and then it is cooled to room temperature. Add toluene to the kettle, mix it with castor oil, add TDI, temperature
Controlled at 50-70 °C, reaction time 1-3h, made a main agent. According to the formulation amount of the adhesive, toluene, coal tar, and cement are successively mixed into the main agent of the type A, and the toluenediamine curing agent is added when used. This type of adhesive can be used to increase the impermeability by 10-18 times for the inner wall of a concrete pipe, and the concrete pipe cannot seep before breaking.
2. Adhesive for concrete pipe flexible joints
1. Preparation
Adhesive Formula A main agent: curing agent: coal tar: glass fiber cloth = l: 0.01-0.1: 5-3: around 2-3 layers of glass cloth (mass fraction).
A main agent formula castor oil: 9DI: toluene = 25-45: 5 ~ 25: 30-70 (parts by mass).
Toluene diamine curing agent formula: acetone = 1:5-20 (mass fraction).
The preparation method is the same as that for concrete pipe impermeability.
The curing agent formula toluene diamine: acetone = 1: 5-20 (mass fraction).
The preparation method is the same as that for concrete pipe impermeability.
2. Applications
A layer of glass cloth is wrapped around a flexible joint of a concrete pipe, and a layer of the adhesive is evenly coated on it, and then a layer of 2 to 3 layers of glass fiber cloth is wrapped around. Brush 2-3 times with this adhesive. 800m long and 1m long concrete concrete water pipe 800m, one joint per meter, total 800 joints, the concrete pipe water volume is 150t/h, pressure is 0.08MPa, water pressure resistance is 0.25MPa, concrete pipe is not water seepage .
3. Adhesive for geotextiles
1. Preparation
Adhesive formula A or B main agent: curing agent: lime powder = 1:0.03-0.2:0.2-0.5 (mass fraction).
A main agent castor oil: TDI: toluene = 25-45: 5-25: 30-70 (parts by mass).
The main agent of castor oil: TDI: acetone = 25-45: 5-25: 30-70 (mass fraction).
Curing agent toluene diamine: acetone = 1:5-20 (parts by mass).
The method for preparation of a main agent is the same as that for the anti-permeability of concrete pipes in section 5.6.1. The main agent of type B is prepared by adding TDI dropwise to a mixed solution of castor oil and acetone and heating it to 40-50° C. for 3 hours. Then the quicklime powder and the curing agent are added to the above A main agent or the B main agent, and the resulting cement adhesive for geotextile has proved to have excellent adhesion effect through practical use.
2. Performance indicators
The adhesive strength of the above geotextile adhesive is shown in Table 9 below.
Table 9 Adhesive Strength of Geotextile Adhesives
batch number
Curing time, h
Destructive power, kg
Bonding area cm2
Shear strength MPa
Destruction
number 1
2.33
3.5
11.3
0.03
The adhesive surface is broken and the geotextile is intact
240.0
33.77
12.56
0.27
The adhesive surface is intact and the geotextile is broken
number 2
1.0
11.6
2.95
0.4
The adhesive surface is broken and the geotextile is intact
168.0
39.07
4.77
0.9
The adhesive surface is intact and the geotextile is broken
4. Fast plugging water adhesive
The ratio of the adhesive is: B type main agent: cement: foaming spirit=1:0.5-5:0.01-0.05. The preparation method of the main agent of the second kind is the same as the adhesive for geotextiles. The cement and the foaming spirit are added into the main agent of the B type, and the adhesive for rapid water plugging is prepared after being stirred evenly.
5. PVC plastic pipe adhesive
Adhesive formula A or B main agent: Epoxy resin = l: 0.05-0.6 (parts by mass).
A kind of main agent is prepared by the same method as the impermeability adhesive of concrete pipe, and the main agent of type B is prepared by the adhesive section of geotextile.
The PVC masterbatch or PVC masterbatch is mixed with the epoxy resin to obtain a PVC plastic pipe adhesive. The adhesive can also be used for bonding other plastic products.
6. Hydraulic seal elastic adhesive
Adhesive Formula A main agent: curing agent: coal tar: mineral wool = 1: 0.01-0.1: 0.5 - 5: 0.1-0.4 (mass fraction).
The preparation method of a main agent and curing agent is the same as that of concrete pipe impermeability. The coal tar and mineral wool are added into a main agent of the type A, and then the curing agent is added after mixing evenly, and the adhesive is prepared after uniformly mixing. The adhesive was used for U-type concrete anti-seepage channel joint seams 850, after two years of testing, many times through the water, so far the adhesive is intact, no shedding, cracks and other phenomena, played anti-seepage, antifreeze, anti-deformation, The effect is good.
Polyurethane structural adhesive
The definition of structural adhesives refers to adhesives that are used in the bonding of force structural parts and can withstand large dynamic loads, static loads, and long-term use. In layman's terms, structural adhesives are structural components that replace metal, plastic, glass, wood, etc. in the form of bolts, rivets, or welds, and are adhesives that can withstand heavy loads over a long period of time and can still be trusted.
People have already been familiar with epoxy adhesives for structural applications, but the use of structural polyurethane adhesives has been gradually recognized. Polyurethanes are block copolymers composed of hard and soft segments. The hard segment molecules provide shear, peel strength, and heat resistance, while the soft segment molecules have resistance to impact, fatigue, and fatigue. By adjusting the composition or structure of the hard and soft sections, a variety of structural polyurethane adhesives having a strength that meets the requirements can be obtained.
1. Development of structural adhesives
Structural Polyurethane Adhesives Since the beginning of FRP (Fiber Reinforced Plastics) for automobiles, great progress has been made over the past 20 years. In addition to its application in the automotive industry, it is also widely used in waterborne vehicles [for the bonding of FRP decks and hulls and the bonding of SMC (plate model composite) towers, SMC floodgates, etc. These adhesives have Excellent vibration resistance and impact resistance], elevators (bonding of elevator doors, wall panels), septic tanks (bonding of FRP flanges, partitions), baths (SMC-tiles, ceilings-tiles Bonding), as well as residential (adhesion between the exterior decorative material cement preforms) and other fields.
(1) Adhesion of automotive components Originally successfully used as a polyurethane structural adhesive for automobiles was piogrip, Coodysr, USA, which is a solvent-free two-component reactive adhesive and used in 1967 for the bonding of 5MC engine covers for trucks. . Subsequently, companies such as GM, Ford, Mack, etc. successively bonded to SMC parts of large-sized trucks. Then it was widened to the FRP part.
Japan introduced technology from the United States and modified it. In 1984, Nissan Polyurethane Adhesive was used to bond Toyota's plastic structural parts with satisfactory results. It can produce adhesives with different morphologies, different viscosities, and different sag resistance properties depending on the structure and composition of the isocyanate-based guanlulu main agent and the polyol curing agent, and its adhesive strength is unchanged; The shear strength is comparable to that of the epoxy resin and at the same time shows a higher peel strength.
(2) Application of elevator paneling Panels used for walls, doors, and the like of elevators have been developed toward lightweight and high-grade in recent years. Among them, weight reduction is achieved through the use of highly rigid lightweight auxiliary materials and the thinning of surface materials. The material of the elevator panel is a steel plate with surface-attached PVC film (abbreviated as PVC steel plate), steel plate, galvanized steel plate, stainless steel plate and non-ferrous stainless steel plate, brass plate, and red copper plate. Panels are usually made of a reinforcing material such as galvanized steel sheet or steel plate bonded to the inner surface of the panel.
The requirements of the paneling on the adhesive are as follows: 1 It can be applied to various materials such as steel plate, PVC steel plate, stainless steel plate, galvanized steel plate, etc.; 2 Peeling strength> 150N/25mm; 3 Impact strength> 1.98j/cm2; 4 Shear strength > 15MPa; 5 destruction of the internal destruction of the adhesive; 6 moisture resistance, 60 °C, 90% RH environment after 60 days, its strength retention rate of 70% or more, and moisture absorption aging before drying, adhesive recovery Good; 7 Creep resistance, excellent fatigue resistance; 8 Even if the thin plate will not be caused by adhesive curing shrinkage and other deformation; 9 With baking paint baking temperature (up to 175 °C) heat resistance; 10 PVC The heat resistance of the steel plate is poor, so the curing temperature requirement is below 80°C; 10 the curing time is within 20min; 10 is suitable for automation.
Japan has successfully developed structural polyurethane adhesives and primers for elevator panels. First, a phosphate ester modifier was used as the main component, and a trace amount of PVC polymer was added (to improve moisture resistance) to make a solvent-type primer. A thin layer was sprayed on the material surface with a sprayer. After the solvent was dried, the coating was applied. Cloth adhesive for bonding. The structural polyurethane adhesive is a two-component adhesive composed of a polyether polyol and an MDI prepolymer.
Currently, structural polyurethane adhesives can not only be used to bond plastics and metals, but also widely used in the bonding of other materials; not only can be used for automotive assembly, and has been extended to the construction, machinery and other industrial fields. In order to make the structural polyurethane rubber more competitive, various countries are continuing to devote a great deal of improvement work, such as reducing the cost, changing the components into single components, further improving the heat resistance and strength, eliminating the direct use of the primer, and simplifying Mixing, extrusion and other construction operations, rich variety, crystal grade, to adapt to more types of sticky materials and more fields of application.
2. resolve resolution
Structural polyurethane adhesives are generally prepared by reacting a polyol with an excess of polyisocyanate to make an isocyanate-terminated prepolymer, and then adding a diamine for chain extension and cross-linking during chain extension and cross-linking. In fact, the urea chain and biuret structure are formed. Therefore, such polyurethane adhesives should be strictly called "polyurea" adhesives.
1. Polyurethane-polyurea adhesive
The main agent of this structural adhesive is a reaction product of TDI and polyoxypropylene glycol (molecular weight 2000 and 1000) to prepare an NCO-containing prepolymer. The curing agent is the reaction of an anhydride with an arylamine (arylamine acylation) to produce aromatic amides (curing agents).
The structural polyurethane adhesive is a solvent-free type, has the characteristics of simple use process, convenient storage and transportation, can be cured at room temperature or heat, and its adhesive layer has elasticity and high shear strength. Therefore, this structural adhesive has been used to achieve satisfactory results for the dolphin helicopter rotor wing tip seal, metal-carbon fiber composite material bonding and component repair.
2. Polyurethane - Epoxy Resin - Polyurea Adhesive
Epoxy adhesives have the characteristics of low flexibility, high hardness, high chemical resistance and high shear strength. If combined with polyurethane adhesives, they can take advantage of both: complementary disadvantages, can be turned out to have certain Softness, but also a good structural adhesive adhesive strength. Therefore, a great deal of research work has been done on epoxy-modified polyurethane adhesives abroad. The synthesis principle is that the polyurethane prepolymer containing NCO end groups is reacted with an alcohol containing an epoxy group to produce an epoxy-terminated polyurethane, the latter skeleton has polyurethane properties; the cross-linking cures through epoxy groups and amines The reaction is completed, generally using a polyurea containing an amino functional group. The resulting adhesive layer was a polyurethane-epoxy-polyurea structure.
3. Adhesive properties
The adhesive properties of the two-component structural polyurethane adhesives to various materials are shown in Table 9 below.
Table 9 Adhesion properties of two-component structural polyurethane adhesives to various materials
Project \ Material
glass fiber
Reinforced plastic
(plate molding compound)
Glass fiber paper
Reinforced plastic
(high fiber content)
Glass fiber paper
Reinforced plastic
(orientation)
Cold rolled steel
Aluminum alloy
Shear strength, MPa
-40°C
22°C
82°C
137°C
Heat aging at 88°C for 14 days
22°C flooding for 14 days
38°C, 00%RH, 14 days
Accelerate atmospheric aging 500h
Bending fatigue 2 plus cuts
Destructive form
4.5
5.2
3.71
2. O1
6.0
5.8
4.3
5.6
4*16
Unbreakable
6.7
8.6
3.31
2.1
6.7
8.1
7.5
8.8
2*106
Cracked material
17.51
19.21
4.81
2.11
18.31
13.71
13.61
19.21
2*105
Cracked material
21.21
17.91
5.61
3.71
17.61
16.81
15.21
17.91
1*106
Cracked material
11.51
7.41
4.91
4.11
11.61
11.41
11.21
7.31
---
---
1 cohesive failure (the rest are destroyed by the adhered material).
Polyurethane ultra-low temperature adhesive
Polyurethane materials are particularly excellent at low temperature resistance, and low temperature and ultra low temperature polyurethane adhesives made using this feature have been widely used in civil and defense industries.
1. Low temperature resistance of polyurethane adhesive
One of the characteristics of the two-component polyurethane adhesive is particularly excellent low temperature performance, which is not available in other adhesives. It can be seen from the table that the shear strength of polyurethane adhesive at low temperature is much higher than that of other adhesives, and the lower the temperature, the higher the strength.
Table 11 Shear Strength of Room Temperature Curing Ultralow Temperature Adhesive (MPa)
Adhesive name
test temperature,
-253
-196
-100
Room temperature
82
121
Polyamide Epoxy
Flexible epoxy
Polyurethane
16
17
70
18
19
49
twenty two
20
40
26
16
10
4
4
3
2
3
3
It can also be seen from Table 11 that the two-component polyurethane adhesives are resistant to fatigue at low temperatures and can withstand long-term vibrations in liquid nitrogen (-196°C). The number of vibrations can exceed 1 million times without Damaged, the latter can only withstand 600,000 times compared to the polyamide epoxy adhesive.
Table 12 Fatigue test of cryogenic adhesives
Adhesive name
Room temperature test
-196°C test
Polyamide Epoxy
Flexible epoxy
Polyurethane
3000 times, all destroyed
280 times, all destroyed
1800 times, no damage was found
600,000 times, damage to metal parts
130 times, all destroyed
1 million times, no damage was found
2. Features and requirements
The characteristics of cryogenic adhesives applied on spacecraft and requirements for adhesives are as follows.
1. Features
(1) Work at liquid oxygen temperature and liquid hydrogen temperature.
(2) The bonding area is large, often the outer surface (or inner surface) of the entire tank.
(3) It can work under the dual effects of thermal stress generated by cold and heat shocks (filling and release of propellant) and pneumatic flushing during flight.
(4) According to the requirements of the manufacturing process of the vehicle itself, it is better to cure at room temperature or at a lower temperature.
2. Requirements
(1) Sufficient ultra-low temperature toughness and elongation are required to ensure that no debonding occurs due to the difference in the linear expansion coefficient between the metal shell and the non-metallic polymer material during the process of receiving the thermal shock.
(2) It must have sufficient ultra-low temperature strength to prevent the outer insulation layer from falling off.
(3) There must be sufficient antisepsis. When it is waiting for the flight, after the propellant is added, serious suction will occur, and the medium in the air will be adsorbed on the interface of the joint to cause corrosion.
(4) It is required to be able to construct a large area on the surface of a complex carrier.
(5) It is required that no low molecular volatiles be generated during the curing process.
According to these characteristics, when the large area of ​​thermal insulation layer is bonded, the spray coating process is used to apply the adhesive layer. The spraying process first requires that the glue must have a low viscosity and be easy to film.
3.DW series ultra-low temperature adhesive
1 glue solution
(1) Formulation of DW-1 Adhesive (mass fraction)
Main agent (prepolymer made of trihydroxy polyoxypropylene polyol and isocyanic acid) 100 parts
(2) Formulation of DW-3 adhesive (mass fraction)
Main agent (tetrahydrofuran polyether polyol-epoxy resin-isocyanate prepolymer) 100 parts
20 parts of curing agent 590 resin
KH-550 (silicon coupling agent) 4 parts
Surfactant 2-5 servings
Acetone 35-55
(3) DW-4 adhesive formula (mass fraction)
Main agent (epoxy resin modified polyurethane prepolymer) 100 parts
Curing agent (MOCA) 25 parts
2. Spraying process
The adhered material was surface-treated, and sprayed with the glue according to the above formula, and allowed to stand at room temperature, followed by heating to 60° C. for 2 hours. The open-air phase can fully evaporate the added solvents and other additives, and can also make the film initially gel at room temperature, which can effectively avoid the flow phenomenon that accompanies the heating process.
3. Adhesive layer performance
The properties of DW series ultra-low temperature polyurethane adhesives are shown in Table 13.
Table 13 Performance of DW Series Ultra-Low Temperature Polyurethane Adhesives
project
Temperature (°C)
DW-1 glue
DW-3 glue
DW-4 glue
Shear strength, MPa
Uneven tear strength, kN/m
Elongation,%
Room temperature
-196
Room temperature
Room temperature
9.3
20.9
20.6
45.6
18.5
24.5
17.4
50
13.0
20.0
--
--
* The material 1010 is aluminum alloy gold.
4. application
Ultra-low temperature polyurethane adhesives have been widely used in civil and aerospace industries, such as bonding materials for various oxygen production and cooling equipment for civil use, bonding of materials in superconducting research, thermal protection layers on modern astronautics, and adhesion of thermal insulation layers. Wait.
Apollo spacecraft, as well as space shuttles, fuel tanks and thermal insulation structures are all glued structurally. The liquid oxygen fuel tank (boiling point -183°C), liquid hydrogen fuel tank (-253°C), liquid nitrogen tank (-196°C ) Ultra-low temperature polyurethane adhesives are used in manufacturing.
Polyurethane flocking adhesive
In recent years, China imported a number of electrostatic flocking production lines from abroad. The flocking products have been widely used in the industries such as service towns, packaging, decoration, and shoemaking. The flocking products with PVC soft film and PVC artificial leather as the base material have a large amount and have developed rapidly. Currently on the market, electrostatic flocking adhesives are mainly used for acrylate adhesives, but the adhesive fastness is poor, and the general dry and wet rubbing fastness is about 2000-4000 times, and the polyurethane type electrostatic flocking adhesives dry and wet wipes. Fastness is generally more than 10,000 times.
1. Solvent type flocking adhesive
1. Preparation
Polytetramethylene adipate-1,4-butanediol (molecular weight 2000) was dehydrated under vacuum at 110°C and 0.06 MPa (gauge pressure) for 1 hour, and a 1,4-butanediol chain extender was added (molar ratio of alcohol ester was 2). : 1) and MDI, when the reaction viscosity increases and starts to tangled in the stirring, ethyl acetate is added to dissolve, and the stirring is evenly the main agent of the glue liquid. Curing agent for TMP-TDI oral products. Glue is formulated according to the main agent: curing agent = 100:8-10 (mass fraction). The main agent viscosity is 1500-3000mPa. s, Solid content 25%-30%, storage period 1 year.
2. Flocking properties
The glue opening time test was performed at 20°C, a relative humidity of 85%, and a curing temperature of 80°C. The properties of its flocking adhesive: opening time 1.5 min, curing time 2.2 min, initial peel strength 10 N/cm, and final peel strength 60 N/cm (material was destroyed). PVC flocking soft film made of the polyurethane flocking adhesive (bonded with nylon fluff or viscose fluff and PVC soft film) has a dry rubbing fastness> 3500 times (without exposed bottom) and wet rubbing fastness> 1000 times (without exposed bottom) ).
2. Solvent-free flocking adhesive
1. Preparation
(1) Preparation of a component A four-necked flask equipped with a stirrer, a wet excavator, and a thermometer was charged with polytetramethylene adipate-1,4-butanediol and TDI and reacted at 80-90°C for 2 hours. NCO is a terminal-based prepolymer. After the determination of NCO content, the chain extender 1,4-butanediol was added to obtain hydroxyl-terminated polyurethane. After adding aminosilicone oil, it was a component (SBG-NS-TDI-BD).
(2) Preparation of Part B Polyester polyols (SEG or SBG) and work TDI were used to prepare NCO-terminated polyurethane prepolymers.
(3) Preparation of C component The curing agent accelerator is compounded. According to A component: B component: C component = 100:10-15:1-2 (mass fraction) to prepare the glue solution.
2. Coating process and properties
A polyurethane glue formulated with a component of Part A, Part B and a component of Propylene = 100:12:2 (mass fraction), with a coating weight of 200 g/m2, using a red viscose fiber on a soft PVC base leather Villi flocking, pre-baking at 100 °C 2min, 160 °C curing 1min, at room temperature for 48h, tested on the abrasion machine, resistance to dry rub more than 10,000 times. Wet rub resistance was measured 2181 times while maintaining water infiltration conditions. Tolerance to toluene abrasion was measured 678 times while maintaining toluene soaking conditions.
Polyurethane anaerobic adhesive
Anaerobic adhesive is defined as an adhesive that inhibits curing in the presence of oxygen and cures itself when oxygen is cut off.
1. Composition of anaerobic adhesive
Most anaerobic adhesives are based on acrylate or methacrylate monomers. Typical anaerobic adhesives are tetraethylene glycol dimethacrylate and ethylene glycol dimethacrylate monomers. As the main component, it is additionally prepared by adding peroxide as a catalyst, hydroquinone as a polymerization inhibitor, and o-sulfobenzimide (saccharin) as an accelerating agent, and is a room-temperature curing adhesive that is stable in the air. . This kind of anaerobic adhesive has been used in various mechanical products, especially products used under vibration conditions, such as fixing of screws and bolts used in automobiles, tractors, ships, machine tools, etc., assembly of shaft sleeves, and sealing of pipe joints.
The above two kinds of anaerobic adhesives have a relatively large brittleness, so their application range is limited to a certain extent. However, if an appropriate polyurethane segment is introduced into the skeleton of the acrylic resin, the impact and shear strength of the anaerobic adhesive can be improved, and its low temperature resistance and hydrolysis resistance are also improved to some extent. The modification of anaerobic adhesives is generally achieved by the reaction of hydroxy-containing methacrylate or acrylate monomers with isocyanates or polyurethane prepolymers containing free isocyanate groups.
2. Preparation and properties
1. Preparation of hydroxypropyl methacrylate-work I resin In a three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, 5 ml of hydroxypropyl methacrylate, 27 mg, hydroquinone 3 g, ice was added. Acetic acid 30g. Start the stirrer, add, TDI1210g, at room temperature, the temperature will rise to above 100 °C, pay attention to appropriate cooling, but do not let the temperature below 95 °C, when the reaction temperature is no longer rise, then in the 95-100 The reaction was started at a temperature of 1.5 °C for 1.5 h and samples were taken to determine the isocyanate group content. The contents were measured every half hour until the isocyanate group content dropped below 0.5%. The reaction was stopped, and the resulting resin (a type of resin) was poured while hot, and stored in a dark polyethylene barrel for use.
2. Preparation of hydroxypropyl methacrylate-polyether-TDI resin
The device is as before. Polyoxypropylene glycol (molecular weight 2000) 2500 g TDI 430 g was put in a 5 L three-necked flask. The stirrer was turned on and the temperature was raised to 80-85°C. The reaction was carried out for 3 hours. Then 770 g of hydroxypropyl methacrylate was added, 37 g of glacial acetic acid (catalyst) and 3 g of hydroquinone were heated to 100° C. and 200° C. The isocyanate group was measured after 2 hours of reaction. The content was measured every half an hour until the isocyanate group content dropped below 0.5% to stop the reaction. The resulting resin (B type resin) was poured while hot and stored in a dark polyethylene barrel.
3. Adhesive formulation and performance
A type of resin is a rigid segment structure resin, and B type resin is a resin having a rigid-flexible mixed segment structure. When adjusting the amount of A and B resins, the properties of the adhesive layer after the glue is cured have certain changes. Therefore, the formulation can be adjusted according to the needs of the adhered material so as to achieve the desired effect. The anaerobic adhesive formulation is shown in the table; the shear strength of polyurethane anaerobic adhesive prepared by the formulation is shown in Table 14.
Table 14 Polyurethane anaerobic adhesive formulations (parts by mass)
Raw material name\recipe number
1
2
3
4
Hydroxypropyl methacrylate
30
26
30
30
A kind of resin
20
30
36
45
B type resin
50
40
36
25
Cumene peroxide
3
3
3
3
N,N-Dimethylaniline
0.5
1.5
0.5
0.5
O-benzoylsulfonimide
1
1
1
1
acrylic acid
2
2
2
2
Quinol
0.02
0.02
0.02
0.02
From Table 14 and Table 15, it can be seen that when the resin of type A increases, its shear strength at room temperature and high temperature increases accordingly, and the shear strength at low temperature decreases accordingly. When the amount of B resin is increased, the shear strength at room temperature and low temperature increases as the number of soft segments increases, and the high temperature shear strength decreases. Due to the increase of the amount of B resin, the low-temperature performance of anaerobic adhesive is improved, reflecting the characteristics of polyether polyurethane. That is, acrylate adhesives can be used with polyurethane resins to change the shortcomings of poor low temperature resistance.
Table 15 Shear Strength of Polyurethane Anaerobic Adhesives
Stick material and its surface treatment
Curing condition °C/h
Test Conditions
Shear strength, MPa
Formula 1
Formula 2
Recipe 3
Formula 4
45 # steel
Sandblasting
25-27
Room temperature
+50°C bonding, after 45 minutes
Determination
After bonding at -4°C for 45 minutes
Determination
17
12
twenty three
19
14
16
26
17
12
29
twenty one
9
Polyurethane conductive adhesive
Conductive adhesive (electric conductive) is a composite (adhesive) composed of a conductive filler such as metal powder or graphite, and a synthetic resin, which has 106-10-6 Ω·cm conductivity and excellent physical properties of a polyurethane binder. Performance: Electrical and electronic components, due to high temperature welding will cause deformation or lead to changes in the performance of components, while computers and instruments are in the direction of miniaturization and lightweight, so the conductive adhesive has been widely used, and polyurethane conductive adhesive It is flexible and resistant to vibration and is more popular with users.
1. Conductive mechanism
The conductive mechanism of the conductive adhesive lies in the contact between the conductive fillers. The mutual contact between the fillers and the filler is formed after the adhesive is cured and dried. Thus, it can be seen that before the adhesive is cured and dried, the conductive materials in the adhesive and the solvent are conductive. The fillers are independent of each other and do not exhibit continuous contact with each other and are therefore in an insulated state. After the adhesive material is cured and dried, the conductive fillers are interlocked with each other as a result of the evaporation of the solvent and the curing of the adhesive material, thereby exhibiting conductivity. At this time, if the amount of adhesive is much larger than that of the conductive filler, even after the adhesive is cured, the conductive filler cannot be connected in a chain-like shape, so that either no conductivity is exhibited at all, or even if there is conductivity, It is also very unstable. Conversely, if the amount of conductive filler is significantly greater than that of the binder, the physicochemical stability of the adhesive film, which is determined by the binder, will be lost, and a firm connection between the conductive fillers will not be obtained, resulting in unstable conductivity. . For this reason, it is important that the conductive filler is mixed with the binder in a proper ratio.
The content of silver powder is closely related to the volume resistivity. The content of silver powder is preferably 70%-90% (parts by mass) and the volume fraction is 20%-50%. When the silver content is below 70% (mass fraction), the resistance value changes significantly and is very unstable. When the silver content is more than 90% (mass fraction), the resistance value increases again.
The connection state of the conductive fillers varies depending on the shape of the filler, and accordingly, different conductance values ​​are also exhibited. Taking silver powder as an example, it has spherulitic, scaly, dendritic, acicular, and flat shapes. Among these shapes, the contact electrical conductivity formed like a scale-like sheet is superior to the point contact electrical conductivity formed by the spherical particles. In addition, the size of the conductive filler has a great influence on the electrical conductivity. When silver powder is used, if the particles of 10 μm or less are properly distributed, the densest filled state can be formed, and the electrical conductivity is good.
2. How to use
1. Substrate
The substrate should be compatible with the type of adhesive used in the adhesive, and the conductive adhesive can be applied to a variety of substrates. The conductive adhesive using a thermosetting resin can be used for metal, glass, ceramics, carbon, crystal, epoxy resin laminates, phenolic resin laminates, and other thermosetting resin laminates. The conductive adhesive using a room-temperature curing resin can be used not only in the above-mentioned substrates but also in a substrate having poor heat resistance such as ABS resin, styrene resin, and paper.
2. Sizing method
The sizing method depends on the nature of the adhesive and solvent in the conductive adhesive, and can be applied by various methods such as brushing, dipping, spraying, screen printing, and microdispenser. In particular, conductive adhesives using conductive fillers such as gold and silver are required to have a low-loss sizing method because of their high cost. In addition, in terms of electronic components, it is required to apply a correct and small amount of glue to very fine parts. In this regard, screen printing, microdispensers, etc. should be used.
3. Curing and drying methods
The curing and drying conditions of the conductive adhesive vary depending on the adhesive and solvent used, and its electrical conductivity, adhesive strength, and various characteristics will exhibit different values ​​depending on the curing drying temperature and time. With the progress of the film curing process, the adhesive strength increases, and accordingly, the volume resistivity decreases, which is due to the progress of the resin agglomeration process, and the chain-like interlocking of the conductive filler is more robust.
Drying equipment uses electric ovens, infrared lamps, far-infrared, etc. It is best to use a heater that can be heated evenly and hot air circulating.