Two-component polyurethane adhesives are one of the most important categories of polyurethane adhesives, with a wide range of uses and large amounts. Usually consists of two components, A and B. The two components are packaged separately and can be prepared in a certain proportion before use. The A component (main agent) is a hydroxy component, and the B component (curing agent) is a component containing a free isocyanate group. Some of the main agents are polyurethane NCO-based prepolymers, the curing agent is a low molecular weight polyol or polyamine, and the A component and the B component are mixed at a certain ratio to form a polyurethane resin.
Two-component polyurethane adhesive has the following features.
(1) A reactive adhesive undergoes a cross-linking reaction after the two components are mixed to produce a cured product.
(2) During the preparation, the raw material composition and molecular weight of the two components can be adjusted to have a suitable viscosity at room temperature, and a high solid content or solvent-free two-component adhesive can be prepared.
(3) It can be cured at room temperature, and the curing speed can be set by selecting the raw material for preparing the adhesive or adding the catalyst. In general, two-component polyurethane adhesives have a large initial adhesion, which is called heat curing, and the final adhesive strength is larger than that of single-component adhesives and can meet the requirements of structural adhesives.
(4) The amount of the two components can be adjusted within a certain range, generally there is a certain degree of tolerance. The NCO/OH mole ratio of the two components is generally greater than or equal to 1, and when cured, part of the NCO groups participate in the curing reaction of the glue, resulting in a chemical adhesion force. When the excess NCO group is cured by heating, Produce allophanate, biuret, etc., increase the degree of cross-linking, improve the cohesive strength and heat resistance of the adhesive layer. For solvent-free two-component polyurethane adhesives, because the initial molecular weight of each component is not large, the NCO/OH molar ratio is generally equal to or slightly greater than l, which is conducive to complete curing, especially when bonding seals, pay attention to NCO The components should not be too much. For solvent-based two-component adhesives, the main agent has a larger molecular weight and better initial viscosity. The amount of the two components can be adjusted within a relatively large range, and the NCO/OH molar ratio can be less than 1 or greater than 1. Times. When there is a large excess of NCO component (curing agent), polyisocyanate self-polymerizes to form a tough adhesive layer, suitable for bonding of hard materials; in the case of a small amount of NCO component, the adhesive layer is soft and can be used Bonding of soft materials such as leather and fabrics.
Since the advent of two-component polyurethane adhesives, they have become the most widely used products in polyurethane adhesives because of their advantages of adjustable properties, high adhesive strength, and wide bonding range.
Universal two-component polyurethane adhesive
General-purpose polyurethane adhesive is based on polyethylene adipate as raw material, solvent-based polyurethane resin as the main component (component A), and trimethylolpropane-T1) I adduct as curing agent (component B). ) Two-component polyurethane adhesive. General-purpose two-component polyurethane adhesive, also known as 101-polyurethane adhesive, is the earliest industrialized production of Shanghai Xinguang Chemical Factory, and it is still the largest domestic production of polyurethane adhesives. There are more than 1,000 domestic users, mainly used for insulating materials and packaging materials. Bonding of composite membranes, porous materials, cryogenic protective materials, etc.
1. Product specifications
General-purpose two-component polyurethane adhesives are required to establish national standards and are currently drafting industry standards. The main technical indicators are shown in Table 1.
Table 1 Specification of Universal Two-component Polyurethane Adhesive Products
2. Storage of adhesives
General-purpose two-component polyurethane adhesive components contain organic solvents (acetone, ethyl acetate, etc.) and are stored and transported in accordance with flammable products regulations. Component B contains active isocyanate groups and should be protected from contact with water and other reactive groups. A component will crystallize or form a flocculent precipitate on a cold day. It is a normal physical change and only needs to be melted in warm water or with a suitable heating device (avoiding open flames). The storage time of components A and B is one year and six months respectively. There are two types of packaging: cans and glass bottles.
3. How to use
The use of two-component polyurethane adhesive directly affects the adhesive properties of the material. Before bonding, it is necessary to pay attention to whether the components of A and B are expired or not. In particular, the B component is deteriorated due to its tendency to undergo polycondensation reaction and should be stored under low-temperature sealing conditions. The application of polyurethane adhesives is generally divided into surface treatment, preparation and coating of adhesives, fixing and curing, and finishing procedures. All steps must strictly comply with the operating procedures, otherwise it will affect the quality of bonding.
1. Instructions
(1) Surface treatment The surface of the adhered material must be decontaminated, rust-removed, degreasing, etc. before the adhesive is applied. Generally, the surface is degreased by sandblasting, grinding wheel, sandpaper, etc., and deoiled with solvents such as toluene, acetone, and ethanol. Go to grease. After treatment, the surface should be dry and flat.
Aluminium-aluminum alloy surface treatment can use zero emery cloth to fight hair and acetone degreasing, put people dipping in 65-70°C sodium dichromate solution for 30min, rinse with water and dry it at 70°C or below. The sodium dichromate solution can be prepared using the following formula: sodium dichromate: water: concentrated sulfuric acid = 7.5:65.2:27.3 or 30:176:50 (parts by mass). The surface of low-carbon steel was sanded with No. 1 emery cloth and then degreased with trichloroethylene to bond. PVC panels and foam are degreased with trichloroethylene, and laminates and fiberglass are trimmed with emery cloth. When the wood, paper and belt are not smooth and clean, they must be surface treated. The effect of the surface treatment method on the adhesive strength (shear strength) of the aluminum-aluminum material is shown in Table 2.
* Anchor-101 glue, A component: B component = 100:50 (mass fraction).
(2) Glue preparation The formulation of the adhesive depends on the requirements of the material to be adhered. Parts A and B have different ratios, and the adhesive can also be mixed with the adhesive. See Table 3 for the proportion of general-purpose two-component polyurethane adhesives A and B.
Table 3 Adhesion Ratio of Adhesive for Various Materials
To accelerate the curing time and increase the initial adhesion, 0.1% to 0.3% of triethanolamine or diethylaminoethanol may be added to the components.
The adhesive can be used after being formulated according to the ratio of A and B components. With a good adhesive can be stored under closed conditions from half a day to a day time (25 °C), if you press A: B = 100:50 preparation, the storage period will be shortened to 3-4h The higher the box temperature, the shorter the storage period; Group B The more points, the faster the curing speed; the higher the hardness of the glue layer, the better the heat resistance. The effect of the distribution ratio of adhesives A and B on the bond strength is shown in Table 4.
Effects of Distribution Ratios of Table 4 and Group B on Adhesive Strength*
* The adhesive material is aluminum-aluminum alloy.
Adding a certain amount of filler to the adhesive can increase the hardness and heat resistance of the adhesive layer, and can also reduce the cost of the adhesive. The amount of filler added is generally 10% to 20% (parts by mass). It is required that the filler particle size be fine and can be uniformly dispersed in the adhesive. And it requires the filler to be dry and easy to be wetted by the adhesive. The influence of the amount of filler added on the aluminum-aluminum bond strength is shown in Table 5.
Table 5 Effect of Filler Additive on Adhesion Strength of Aluminum-Aluminum
Quartz powder, aluminum powder, iron powder, asbestos powder, and talcum powder can be used as fillers for general-purpose polyurethane adhesives.
(3) Coating and Curing When using a good glue solution for coating, use a paintbrush to apply the glue to the surface of the treated material. Place the glue for 5-10 minutes after the first application of the glue, and then apply it for a second time. 10-20min. Then, the surfaces of the materials to be bonded are attached together, and a pressure of 0.03-0.05 MPa is allowed to cure, and the pressing time is several minutes to 10 h. The adhesive bonding parts can be bonded at room temperature for a day and night to achieve a greater bonding strength. It takes 3-5 days to reach maximum intensity. Heating and curing can shorten the curing time, such as 2 hours at 100°C and 1 hour at 130°C, and the adhesive layer can reach the basic curing. Adhesives have a certain amount of adhesion before they cure, but do not use them in hot and humid places.
When the area of ​​the adhered material is large, the paint brush or the spray coating method can be used for sizing. The effect of the curing temperature on the adhesive strength is shown in Table 6, and the adhesion conditions of various adhered materials are shown in Table 7.
Table 6 Effect of Curing Temperature on Adhesive Strength
Table 7 Bonding Conditions for Various Bonded Materials
4. Adhesive properties
The adhesive strength of general-purpose two-component polyurethane adhesives to various materials is shown in Table 8. The adhesive strength of the aluminum-aluminum alloy adhesive at various temperatures is shown in Table 9.
Table 8 Bonding Strength of Various Bonded Materials 1
1 A component: B component: 100: 100 (parts by mass).
2 Phenolic laminates.
Table 9 Adhesive Strength of Aluminum Alloy Adhesives at Various Temperatures
The hard PVC was bonded with a general-purpose two-component polyurethane adhesive and immersed in acid and alkaline solutions at different temperatures for 7 days respectively. The shear strength was measured as shown in the table. Immersed in sodium hydroxide solution, the adhesive film is in powder form, and immersed in hydrochloric acid is crisp.
The aluminum-aluminum bonded specimens were tested for oil resistance, hydrolysis resistance, and damp heat resistance. The changes in the adhesive properties are shown in the table. From the oil resistance test data, the gasoline soaked with the highest adhesion, cold water immersed second, therefore, can be used as a hydrolysis resistant adhesive, but not suitable for long-term use. However, after heat aging at 70°C, the adhesive strength was increased, which indicates that the polyurethane adhesive cures better under heating conditions.
Table 10 Corrosion Resistance Test of Hard PVC Hard PVC Bonds
Table 11 Oil-, water- and heat-and-moisture-aging tests of aluminum-aluminum alloy adhesives
5. Improved Universal Polyurethane Adhesive
In the production operation of the above-mentioned general-purpose two-component polyurethane adhesive, there is a problem that it is difficult to control the viscosity. If the index cannot be achieved, the initial adhesive strength of the adhesive is poor, which brings difficulties in use. In addition, general general purpose adhesives may produce crystals or floccules in winter, and may be used after being heated and melted, thus causing troubles for users. After the improvement of the preparation method and the adjustment of the structure of the polyester polyol, the above problems are solved, and a universal two-component polyurethane adhesive that is popular among users is obtained.
1. Chain extension method to prepare a component of glue
Polyethylene adipate - ethylene glycol after vacuum dehydration, the moisture content of 0.06% or less. The molar ratio (R index) of toluene diisocyanate (80/20) to polyester polyol can be equal to 2.5, and the charge amount of TDI and polyester polyol can be calculated. The reaction temperature between TDI and polyester polyol is 90-95°C, and the reaction time is 2 hours. The chain extension reaction of diethylene glycol (diethylene glycol) chain extender and dibutyltin dilaurate catalyst are carried out according to the calculation to increase the molecular weight. (Viscosity) is further increased, and the addition amount of the solvent and the addition method are performed with reference to the above-described production method. The viscosity index of the component A glue prepared by the chain extension method is stable, and the viscosity index of the component A glue liquid can be controlled by adding the amount of the chain extender (diethylene glycol).
2. Low-temperature non-crystallized A component glue
The a-component glue prepared by using polyethylene adipate-ethylene glycol-propylene glycol instead of polyethylene adipate can be stored at room temperature and at a low temperature of about zero without crystals and floccules. Will crystallize. The molar ratio of ethylene glycol to propylene glycol in the polyester is 8:2 or 9:1.
Applications
General-purpose two-component polyurethane adhesives can be used for bonding metals (such as aluminum, iron, steel, etc.), non-metals (such as ceramics, wood, leather, plastics, etc.) and bonding between different materials. General Purpose Two-component Polyurethane Adhesives are used in a large number of applications for the manufacture of insulating papers (polyester film-cyan shell paper composites), paper-plastic composites (printed paper-polypropylene films), iron-polyurethane foam composites, and brushes Other uses such as manufacturing have penetrated into various fields of the national economy.
1. Machine Tool Guide Maintenance
The plastic sheet is adhered to the cast iron guide rails by means of inlaid and glued plastic plates to form a plastic guide rail, which can solve the wear of the machine tool guide rails. Use iron anchor-10l polyurethane glue, according to A component: B component = 100:50 (mass part number) to prepare the glue solution, mix in the glue solution with a diameter of ∮ is 0.1mm, length is 20mm of thin copper wire, so that Keep enough space between the guide rail and the plastic plate to prevent the glue from extruding. The two adhesive surfaces of the plastic plate and the cast iron guide rails are required to be separately coated with the glue liquid twice. The first time the brush is applied for 5 minutes and then the second time is applied. After the plastic layer is sticky and has a wire drawing phenomenon for 15-20 minutes, the plastic is used again. The plate is superimposed with the guide rails, and it is pressurized by its own weight. Due to the large temperature difference between winter and summer, it will cause the plastic to expand or shrink, and the internal stress will be cracked. Therefore, the curing temperature
The best degree is maintained between 20-25 °C, curing time 1-2 days.
2. Speaker bonding
The vibration system of the speaker, that is, the paper box, the voice coil, and the positioning bracket, need to be stuck together. Especially when the high-power loudspeaker vibrates, the amplitude is relatively large, so it must be firmly bonded because it directly affects the service life of the loudspeaker. In particular, loudspeakers with ∮100mm or more are all bonded with polyurethane adhesive. Using anchor-101 polyurethane adhesive according to A component: B component = 100: 30-35 (mass fraction) with plastic, after use can achieve the desired effect. The voice coil of the speaker is glued, and the glue is prepared with A component: B component = 100:25 (mass fraction).
3. Application in brushing products
General-purpose two-component polyurethane adhesive is the ideal adhesive for brushing. The bonding of the bristles is to bind the bristles (pigs or nylon bristles, etc.), the wood chips (wood) and the brush shell (tinplate). The surface is closed to l-2mm, and the penetration of 6-9mm is required. The formula of commonly used glue is: 100 parts of A component, 35 parts of B component, and 30 parts of talcum powder (≥160 mesh). Put the prepared adhesive into the brush housing or use the brush and glue machine to pot the sealer. Shake the brush head after potting to make the adhesive even and place it into dry coagulation (transfer to hairy hair for not less than 24 hours). The adhesive strength after brushing with the adhesive is greater than 130N, which meets the SG236--8l standard for piglet paint brushes (98N). If it is not detached or loosened after soaking in acetone for 24 hours, it indicates that the glue meets the requirements.
4. Adhesion Repair of High Pressure Plastic Duct
Wire pulling machine is the introduction of equipment, high pressure plastic pipe rupture often leads to equipment defects, affecting production. The jointed and socketed composite joints designed with nylon sleeves can not only meet the requirements of 0.8MPa pressure, but also avoid the expansion problem of nylon sleeves. First, the lengthened 100mm, inner diameter ∮2mm nylon sleeve and inner wall ∮12mm (outer diameter) high-pressure plastic air duct ends (outer wall of 50mm length) were roughened with an emery cloth, cleaned with acetone, and dried to be adhered. The iron anchor-101 polyurethane adhesive is used, and the glue is prepared according to the A component: B component = 5:1 (mass fraction), and the broken high-pressure plastic wind pipe end is firstly glued with a glue layer thickness of 0.05-0.1 mm. Immediately insert the nylon sleeve into the plastic coating end of the high-pressure plastic air duct, and rotate the nylon sleeve around to ensure that the adhesive adheres evenly and fills the gap between the inner wall of the nylon sleeve and the high-pressure plastic air duct. The insertion depth is nylon sleeve. Half of the (50mm) high pressure plastic air duct on the other end, according to the above method for bonding, so that the two sections of high pressure plastic duct basically consistent, cured at room temperature for 48h, 100 °C to maintain 2h. The repaired steel wire lapping machine did not see adhesion abnormalities for half a year, which proved that the adhesive can meet the working conditions of 0.8 MPa pressure.
5. Tractor body crack adhesion repair
The cracking of the tractor body can be repaired with iron anchor-101 polyurethane adhesive, and no abnormal phenomenon was found after two years of adhesive repair. The bonding process is briefly described as follows.
(1) Clean the cracked surface Clean the oil around the crack with gasoline and a wire brush. To find the two ends of the crack, drill a hole in the two women's hands with a hand drill.
(2) Open the V-groove with a chisel. Open the V-notch at 60-70°C along the crack line until it stops. The depth of the groove is 2/5 of the thickness of the body.
(3) Cleaning of the V-shaped groove adhesive surface First, wipe the adhered surface with cotton yarn and alcohol, wipe about 2-3 times along the circumference of the V-shaped groove about 30mm, then wipe the adhered surface with cotton wool and acetone until the adhesive surface is reached. Thoroughly clean until now.
(4) The compounding agent is formulated according to the A component: B component = 2:1 (volume ratio), fully stirred and then the adhesive is poured along the V-shaped groove to make it slightly higher than the surface of the body to force the paint blade. Scrape, compact, compress.
(5) The curing bulb is heated or heated with an electric blower, and it is completely cured after 2 hours (the temperature is controlled at about 1 mC).
(6) Finishing Firstly use a guillotine knife, then use sandpaper to polish and remove the plastic stencil that is higher than the surface of the body to make it flat with the surface of the body.
6. Low-greenhouse electric light line bonding and installation
The low-temperature indoor walls and ceiling are iron skins with a paint coating. Indoor use temperature is -70-60 °C, sometimes for more than 10 consecutive days. After use, the temperature is 10-30°C and the relative humidity is 100%. The bonding process for installing the lamp circuit in a low temperature room is briefly described as follows.
(1) Adhesive surface treatment The blade and sandpaper will be roughened by the surface to be adhered and then cleaned with alcohol or acetone and dried.
(2) Mixing glue The iron anchor-101 polyurethane adhesive is formulated according to A component: B component = 100:20-30 (parts by mass), and an additional agent such as a coupling agent.
(3) Bonding Brush Apply the glue to the surface to be bonded, and let it stand for 30-40 minutes. Put the aluminum sheet of the electric lamp line to be connected with the wall and ceiling together, and gently press with a finger or other tool. Several times, make it firmly bonded. A layer of rubber protective primer is then applied to the bonding area of ​​the aluminum sheet. In addition, the glue is applied to the wall and the ceiling cement girder to which the electric lamp base is to be mounted and then the electric lamp base is adhered to the adhesive surface of the wall and the cement girder, and an appropriate pressure is applied thereto. In particular, the cement on the roof cement girder should be tightly supported with wooden rods and other objects.
(4) Curing at room temperature for more than 48 hours. The practice of using this method to bond light lines installed over the years has proven normal use.
Magnetic material glue
The binder resin for magnetic recording media and its performance evaluation are shown in the table. The use of these resins alone is not common, and they are generally used in combination with good overall performance. Generally, the resin composition consists of three components: (1) hydroxyl-containing components such as epoxy resins, acrylic resins, polyester resins, chloroacetic resins, nitrocellulose, etc.; (2) Amino-esterification with the above resins The polyisocyanate components, such as biuret type, trimer type polyisocyanate, polyol isocyanate adduct; (3) modified elastomer components, such as thermoplastic polyurethane, nitrile rubber.
Table 12 Selection of Resins for Tape Adhesives
Note: A audio; V audio; D digital; ○ excellent; △ in; ※ poor.
Tape adhesives require the following features:
(1) The magnetic coating can be well bonded to the base film; (2) The magnetic powder is well dispersed in the adhesive; (3) The coating has good abrasion resistance; (4) Has moderate softness; (5 ) Low coefficient of friction; (6) Low electrical resistance; (7) Good resistance to chemicals; (8) No stickiness after curing of the coating; (9) Wide temperature range for coating application; (10) Long-term preservation without aging .
Polyurethane resin has good adhesiveness to many substrates, and is excellent in abrasion resistance and durability. It is the main resin in magnetic coatings. Most magnetic coatings contain PU resins. Nowadays, the development trend of magnetic coatings is the formulation simplification. In some cases, the binder resin only includes vinyl resin and thermoplastic polyurethane “TPUâ€. It was reported recently in a video tape magnetic coating formulation. Use TPU only.
The PU resin used for the magnetic recording medium is generally polybutylene adipate, polyhexylene adipate, polycaprolactone or phthalate polyester polyols, and polyisocyanates such as MDI, TDI, HDI, and IPDI. The synthesized TPU resin has a molecular weight of 1 to 10 thousand. The adhesives are of single-component and two-component type. TPUs for tape adhesives generally have the following properties:
(1) Very good solubility in solvents;
(2) Good dispersion of magnetic powder, good adhesion to magnetic powder and base film;
(3) No tackiness in the contact layer (surface layer);
(4) has particular physicochemical properties such as relatively high hardness, abrasion resistance, elasticity and gloss, very good molecular weight A/-/d4. distributed.
Formula example
The use of PU in magnetic coatings for adhesives can be said to have two aspects.
One is a polyurethane resin (usually a TPU, or a mixture of an oligomer polyol such as polyester and a diisocyanate), alone or in combination with other resins, dissolved in a solvent as a main component of a tape adhesive. Due to the good blending property of PU adhesive and various resins, the magnetic powder can be well dispersed in the resin solution, has excellent adhesion to various substrates, and the obtained magnetic coating has excellent wear resistance and durability. Excellent flexibility, so most magnetic coating formulations contain PU.
Second, most magnetic coating formulations use polyisocyanate as the cross-linking component of the adhesive, which constitutes a two-component magnetic coating. The use of a two-component magnetic coating has a limited pot life, but the resulting magnetic recording material is superior in heat resistance and durability to a single component without a cross-linking agent.
Here are some magnetic coating formulations.
1. Main component of resin made of TPU elastomer as adhesive Most PU adhesives used for magnetic coating are thermoplastic polyurethane, which makes TPU
Has excellent mechanical strength, elastic modulus. TPU resins for magnetic coating adhesives are not completely versatile with TyU resins used as shoe covers and the like and generally require special preparation. TyU made from polyester containing pendant methyl groups has better performance.
One of TDK's patented formulas is as follows:
The insufficiency of the dispersibility of the ordinary crystalline polyester hepatic U powder can be improved by introducing an SQ3M, a CO2M plasma group into the molecular chain. One such magnetic coating formulation is as follows:
* PU resin formula: the use of HOCH2CH2C (SO3Na) (CH3) CH2CH2OH as a starter poly-caprolactone (Mw200) 100 parts by mass; poly (ethylene adipate diol) (Mw200) 100 parts; MDl 24.8 parts; 0.02 parts of Dabco catalyst. The resin contains an ionic group, which improves the dispersibility of the magnetic powder.
In the two-component magnetic coating, no catalyst is generally added, but in order to shorten the curing time and guarantee a certain applicator, the formulation with a small amount of catalyst has been studied:
2. Radiation curable modified PU adhesive
Some patents have reported radiation-curable magnetic coatings. Modified PU adhesives containing unsaturated bonds are coated on the base film into a thin layer suitable for electron beam radiation curing. In most cases, the acrylic resin is modified with a urethane resin to form a binder resin component, and sometimes a polyfunctional cross-linking agent is added. TPU resin is generally polyester type, there are a small amount of polyether used as raw materials.
One available electron beam cured magnetic coating formulation is:
The preparation formula of acrylic modified polyurethane resin is:
3. Other types of tape with PU adhesive
BASF and other companies in Germany have developed emulsion-based PU adhesives for magnetic coatings, including a formulation example for the preparation of PU emulsion adhesives.
The preparation method comprises the following steps: heating reaction of polyester, small molecule diol and triol, epoxy acrylate and MDI in tetrahydrofuran, and dropping the catalyst, then adding the mixture of mercaptopropionic acid and triethylamine in acetone, and dispersing in water after 45 minutes The solvent was distilled off to obtain a concave emulsion adhesive.
The emulsion was added with 1.5% silicone oil, added to the aqueous dispersion of r-Fe2O3, mixed well, coated on a P1 film, and dried to obtain a magnetic recording tape. Some people use polyurethane adhesive to apply a coating on the back of a magnetically coated tape to improve the tape's abrasion resistance and obtain a good coefficient of friction. This coating consists of a PU binder and a non-magnetic powder. A coating for this application consists of polyurethane resin (Nippo-ran 2301), polyisocyanate (Coronate L), calcium carbonate powder and methyl ethyl ketone.
Ink glue
Polyurethane resin is excellent in flexibility, adhesiveness, and dispersibility of pigments, and can be used as a binder for photogravure and screen printing inks on plastic or metal surfaces.
Different from the PU resins used in other fields, the PU used in ink should have the following requirements: (1) The most basic is soluble, taking into account the compatibility with pigments, other resins, and adapting inks. For solvent volatility and other aspects, alcohol mixed solvent; (2) dry resin surface without stickiness; (3) PU resin dissolved in mixed solvent PU adhesive viscosity should be lower + film After its intensity should be higher;
(4) Adhesives should have good adhesion to smooth-surfaced substrates, so crystalline TPU resins generally cannot be used.
The PU resin used in the ink binder is generally prepared from a polyester or polyether polyol, an alicyclic diisocyanate, and a diamine/diol chain extender and has a molecular weight of about tens of thousands. In order to be soluble in alcohol, and to improve film strength, adhesion to plastics or other substrates, and dispersibility of pigments, urea bonds are generally introduced into PU resins to form polyurethane-urea resins (PUU). The polyurethane adhesives for inks are mostly one-component.
A Japanese patent of Dainippon Ink & Chemical Industry Co., Ltd. gives a method for producing a PU ink adhesive (I): a solid content of 80 is obtained by reacting polybutylene terephthalate diol with methyl ethyl ketone % of the prepolymer solution, 1350 parts of the prepolymer solution was reacted with 68 parts of isophoronediamine PD and 12.9 parts of diisobutylamine in 1470 parts of methyl ethyl ketone at 40° C. for 1 hour to obtain a solid content of about 40%. The PUU solution has a PUU molecular weight of 19,200. This solution was further treated with 77 parts of 75% HDI/P-adduct (NCO content 12%) at 80°C for 3 hours, and a mixture of methyl ethyl ketone and isopropyl alcohol was added and stirring was continued to prepare a 30%-concentration resin solution adhesive. The viscosity is 1050 MPa·s at 25°C.
An ink composition comprising 30 parts of the above-mentioned PU adhesive, 30 parts of titanium dioxide pigment, 10 parts of isopropyl alcohol and 30 parts of methyl ethyl ketone, and printing on PE, PP and PET films, and performing an adhesive tape peeling test and discovering the ink The print layer has a retention of > 90%. This ink, when mixed with a polyisocyanate crosslinker, has a longer pot life. For example, adding 3% of the cross-linking agent, 40 bar after 24h storage viscosity increase rate of less than 10%.
A PU resin for ink binders (developers) developed by Sanyo Chemicals Co., Ltd. is made of PBA polyester (Mw1500), IPDI, IPDA, and diethanolamine. The softening point is 120°C and A4-27600. 100% modulus is 3MPa. Due to the introduction of urea bonds and amine groups, the intermolecular hydrogen bonding force is greatly increased, and the cohesive strength of the resin and the adhesion to the film are improved. The plastic film printing ink prepared from 30 parts of the resin, 50 parts of titanium dioxide and several parts of the mixed solvent has good printing effect on PP, PET and nylon film, and the printing layer has heat-resistant grease and anti-adhesion.
As another example, a PUU resin prepared from poly(ethylene adipate-(3-methyl-1,5-pentanediol))diol 0.5 mol, poly(tetrahydrofuran ether glycol) (Mw 2000) 0.5 mol, HwMD 2.5 mol, and IPD 11.5 mol Used for ink adhesives, which can make the dispersion of pigments in the ink more uniform and have better adhesion to the substrate.
Polyurethane inks are high-grade inks, which are widely used but are generally used as special inks.
A typical example is that polyamide ink is commonly used for domestic plastic film printing inks. This universal ink has better printing performance and tape peeling test is also acceptable. However, if the printing surface is to be post-sequentially compounded, it is covered with a transparent plastic film. The printing surface, to protect the printing layer, and the laminating film for composite flexible packaging, have found that the composite fastness is greatly reduced compared with unprinted plastic film. The reason is that the flexible packaging composite film composite process
The polyurethane adhesive used has an influence on the ink layer. In the composite film peeling test, the ink layer is easily peeled off from the plastic base film, and the ink layer and the adhesive layer are combined firmly, and the adhesive layer is substantially not damaged. The ideal peeling damage should be that the small part of the ink layer is peeled off and the adhesive layer is damaged. Therefore, this type of reverse printing should use special anti-printing inks such as polyurethane inks, chlorosulfonated polyethylene inks, and chlorinated polypropylene inks. From the viewpoint of resin preparation, as long as isophorone diisocyanate, isophoronediamine and other raw materials can be obtained, PU ink can be easily prepared on a small scale, and the preparation of chlorinated polypropylene resin and the like requires a chlorination process. Produce environmental pollution and have certain risks. It is said that some high-performance inks and ink resins need to be imported.
Broken wood glue
The various properties of the regenerated boards such as particle board are mainly related to the scrap and the adhesive used, and are more dependent on the properties of the adhesive. Regenerated boards such as chipboard made with binders and wood chips, with PF,. Compared with regenerated boards made of binders such as UF, they have better performance.
Germany's Roffael et al. compared the water absorption of MDI-based adhesives, UP-adhesives, and PP-adhesive-bonded particleboards at different relative humidity (nU) at 20°C. It was found that particleboard manufactured from MDl-based adhesives is high. Low water absorption in RH environment
Germany's Roffael has experimentally concluded that compared with PF rubber, the use of rough MDl as particleboard binder has some advantages. For example, the density of the plate made of crude MDI can be reduced by 10%-15%, but still has higher strength. At the same time, the pressing time is shortened. Deppe points out production conditions for the use of trialdehyde binders
The use of different adhesive particleboards at 20°C imposes stringent requirements on the moisture content of the raw materials. Comparison of the water absorbency at different relative humidity even if the moisture content exceeds 0.5% is likely to cause cracks in the plate. The heating and molding process produces excessive vapor pressure.
The use of PU adhesives does not present this problem. He also reported that isocyanate-bonded particleboard has similar weather resistance to that of PP panels. Tests have shown that the use of coarse MDI with a mass of wood chips of 5% to 6% as binder can produce satisfactory performance. The adhesive needs 10%, which reduces the cost difference between using PP adhesive and isocyanate adhesive. As for crop straws and flax stalk scraps, in general, PP or UP adhesives are used to treat the boards. The properties of the resulting boards are not satisfactory, while the use of coarse MDI adhesives is more appropriate.
Sachs used coarse MDI and commercially available PF resin as binders to produce particleboard samples with the same amount of binder, 1% of paraffin wax, 170°C molding temperature, and 16mm particleboard thickness. Kind of sheet properties.
It has been found through practice that MDI-based adhesives (including crude MDI, ie, PAP1) are more suitable as woodworking adhesives and adhesives than TDI systems. Sachs used the same amount of these two types of adhesives to make three-layer test particleboards. The performances are shown in Table 13.
Table 13 Particleboard properties of different types of PU adhesives
Note: The amount of binder is 6% of the dry wood quality.
Broken wood polyurethane adhesive
The PU adhesives used for the bonding of broken wood and other agricultural and forestry product scraps are one-component moisture-curing PU adhesives (including PU prepolymers, polyisocyanate adhesives), two-component reactive adhesives, and waterborne Several kinds of vinyl isocyanate adhesives.
In the early days, PAPI was used as a wood chip binder and later modified with polyols to improve the bending strength of boards. Milota et al. modified PAPI with ethylene glycol (EG), polyethylene glycol (PEG), and polyether triol Isonol93. When PEGMW 1000 was added to PAPI, the internal bond strength and fracture strength of the manufactured panels were increased by 35% and 13.5%, respectively, compared to the panel strengths produced by pure PAPI. When the molar ratio of PAyI to PKG is from 6:1 to 12:1, the performance of PEG on the board is the most improved. With the increase of the molecular weight of the polyol, the cohesive strength of the binder resin is improved and the performance of the board is improved. For example, when the molar ratio of PAPI to diol is 12:1, the internal bond strength and breaking strength of the PEG-modified plate are respectively 30% and 29% higher than those of the EG modification, but when the PAPI is modified with Isonol93 , The flexibility of the board decreases. The particle board made of PU adhesive consisting of PAPI and Isonol93 had 72.5% higher breaking strength after boiling for 2h than unmodified PAPI.
The following are examples of bonding of PU adhesives.
Example 1: Chips (thickness 0.5mm) 100
PAP18
The wood chips and the binder were mixed and hot-pressed to obtain a particle board having a density of 0.4 g/cm3. The bending strength was 12.7 MPa in the dry state and 8.8 MPa in the wet state.
Example 2: Sawdust (3% to 4%) 100
PAPl3
PPG1
The above materials were mixed and hot-molded at 160° C. for 10 minutes to obtain a particle plate having a bending strength of 18.1 MPa and a tensile strength of 0.54 MPa.
The polyurethane foam system can be used as a binder for wood chips. Example 3 is a formulation of a PU foam adhesive.
Example 3: Polymer polyol (hydroxyl value 28 mg KOH/g) 45 triethylamine 0.45
Polyether triol (Mw5000) 45 color paste 2
Ethylene glycol 10CFC-1111
Water 0.3PAPI58.3
This binder had an initial viscosity of 300 mPa·s.
Because of its low viscosity and easy operation, waterborne vinyl urethane adhesives have become the mainstream of wood processing adhesives in foreign countries. Water-based vinyl PU adhesive is composed of an MDI-type PU prepolymer or PAPI-based isocyanate dispersed in a water-soluble polymer solution or an aqueous polymer dispersion, containing active groups, and has a certain pot life. The amount of water-based adhesive is related to the size of the wood, molding pressure, etc., generally between 6% and 30%. Compared with the "trialdehyde" binder, the use of an aqueous PU binder to make a regeneration plate has a short molding time, a small amount, and good water resistance.
Example 4:
PEG(MW300)5.7PAPI94.3
Nonionic Surfactant 3.5 Water 240
In the literature, the method for preparing a plate using the above adhesive is: immersing chips in 4% of the above-mentioned PU dispersion, taking out the chips, drying, flattening, and covering a layer of wood chips coated with PP adhesive, and hot pressing at 170° C. After 8 min, the resulting particleboard has a wet bending strength of 11.4 MPa and a water swelling rate of 6%.
Sand adhesive
1 Overview
In the manufacture of metal parts, a widely used method is to use a sand mold, cast the molten metal therein, and cool the mold. If the casting is hollow, the core must also be placed in a sand mold to prevent the molten metal from flowing into the hollow part (cavity). In order to prepare sand molds and core molds with sufficient strength, a small amount of binder must be mixed in the sand. This process of combining the dry and fine sands is called "foundry-sand". Nowadays, the “cold box method†has been commonly used for sandblasting, that is, without baking, it is solidified into a sand type and a core type at room temperature. The flipping adhesives that can be used in the cold box method include water glass-carbon dioxide system, phenolic resin solution-polyisocyanate-triethylamine (aerosol) system (this system is mainly used for making core type), furan resin-strong acid catalyst system, Oil modified alkyd resin-polyisocyanate-catalyst, phenolic resin solution-polyisocyanate-organic base catalyst, resole-resin-p-toluenesulfonic acid catalyst system and the like. This room-temperature shaped sand mold is also known as "self-hardening sand." The entire casting process can be roughly divided into the following steps.
(1) Cast "mold" (sand or core type) by using the shape of the desired casting as a model. Generally, a model (mother type) box can be made of a material such as a wood board or a plastic material, and the binder is mixed in the sand, and the sand is put into the mother model, and compacted.
(2) The molding sand mixed with the binder is allowed to stand and solidify at room temperature until the sand mold has a certain strength (in the United States, the compressive strength is specified to be 137 kPh or more, and the strength of the sand mold and the core mold is not easily deformed), and the mold is released.
(3) Using a sand mold (or core mold) as a mold, pouring molten metal, cooling and solidifying.
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