American AsHland Chemical Company first used two-component PU adhesives for industrial sanding. In 1965, 1968, and 1970, three kinds of two-component PU adhesives were developed for the first time. Its polyol component was the first. The species is alkyd resin made from linseed oil, pentaerythritol and isophthalic acid, and the second and third are phenolic resin polyols; the hardener component is PAPI. U.S. Reichold Chemical Industry Co., Ltd. began supplying a large amount of self-hardening sand polyurethane adhesives in 1979. According to reports, in the U.S. PU adhesive market in the United States, the amount of sanding adhesive was 34,000 tons, and the amount of PU glue used in carpet backings, construction, transportation, footwear, fabrics, tapes, etc. was only added. In 2005, the total amount of PU adhesives used for sandblasting exceeded 5.7 million tons (estimated components including phenolic resin).
China Minmetals Changzhou Organic Chemical Factory exclusively imported foundry chemicals production technology from AsHland Chemical Company of the United States. It was completed and put into production in 1989. It has phenolic type polyurethane cold box adhesives, polyurethane self-hardening sand adhesives, and thermosetting phenolic resins. Sand binder, furan resin
FGD resin, mold release agent, catalyst, paint, cleaning agent, etc., in which polyurethane type sand adhesive is the main product. Making sand moulds with two-component polyurethane adhesives has the following advantages:
(1) Curing at room temperature (even below 0°C) without baking, saving energy;
(2) The pot life can be adjusted within a relatively large range and it is easy to operate. The pot life can be controlled by controlling the amount of catalyst.
(3) The sand mold has high strength and good collapsibility, and it is easy to "mold release";
(4) Most of the phenolic resin-PAPI is used, and the price is low.
Phenolic polyurethane adhesive
This tumbling binder is composed of hydroxyl-containing phenolic resin as one component and polyisocyanate as another component. The two components of phenolic resin and polyisocyanate are mixed and rapidly solidified at room temperature. It is used for casting ferrous core castings. It has the advantages of long mixing period, good fluidity, suitable strength, good collapsibility, low gas emission, and can be produced. High-precision, smooth surface castings, and has the advantages of improving the labor environment and improving labor productivity. Phenolic resins are generally benzyl ether-containing resole resins:
The polyisocyanate component is generally a polymethylene polyphenyl polyisocyanate (ie, PAP1) which reacts polyols with isocyanates faster than polyether polyols.
Comparing Pepset urethane adhesive (composed of phenolic resin-polyisocyanate-catalyst) and furan resin-strong acid catalyst binder system, linseed oil modified alkyd resin-polyisocyanate-catalyst system (linocure) Application period and sand setting time. It can be seen that the phenolic adhesive has a similar pot life as the latter two adhesives, but the curing speed is fast.
Taking the phenolic urethane adhesive of Changzhou Organic Chemical Factory as an example, the properties and application of this kind of self-hardening sand adhesive are introduced. The phenolic urethane adhesives of the plant are general-purpose resin Cl308/608, moisture-resistant resin Cl308M/608 and C1903/904, cast aluminum resin Cl385/685, and their physical properties.
The main steps of making cores with adhesives are: mixing molding sand with binder resin, blending the resin with sand, and blowing the amine through the core, and the sand core is solidified immediately, blowing air to remove the amine catalyst, and then removing the core. At this time, the sand core has a very high instantaneous strength. Among the above three types of resins, general-purpose types are widely used in the core types of gray iron, ductile iron, aluminum, magnesium, copper mixtures, and steel castings. Comparison of Curing Speeds of Several Adhesives with Moisture-Resistant Resin Adhesives Mixtures are less sensitive to the moisture and environmental humidity of the raw sand, and the die-casting aluminum special cold box adhesive has excellent collapsibility and zero free aldehyde.
Polyurethane self-hardening sand adhesive
This type of adhesive is a polyether polyol, an alkyd polyol as a hydroxy component, and a polyisocyanate as a curing agent component. This kind of adhesive has special curing characteristics. The mixed sand has good fluidity until the curing time is reached. Once it reaches the curing time, it immediately cures. Even if the sand thickness can be uniformly cured, the available time and demolding time can be adjusted. The sand size is accurate, and the castings are also accurate. Usually, the amount of binder used is 1%-2% of sand to produce enough strength to get good castings.
For example, the formula for general-purpose polyurethane self-hardening sand adhesives used in Changzhou Organic Chemicals Factory is: the amount of polyol component CPI1600 is 1% by weight of sand, the amount of polyisocyanate component CPII2600 is 1% by weight of sand, and the catalyst CPIII3550 is multicomponent. 1% of the alcohol component. The method of use is to mix the pre-weighed catalyst with the polyol component, and then mix it evenly with the poured sand, and then pour the measured amount of polyisocyanate into the sand, time and mix, and start filling. Sand, 10-25min from the time at room temperature can be demoulded.
It is said that a kind of cast aluminum special-purpose polyurethane self-hardening sand adhesive has particularly good collapsible performance, and the falling sand is like running water. The method of use is: firstly mix the sand brown-black, polyol component CPI5140 with relative density of about 0.95 (the amount is 1% of the sand weight) with the sand, and then mix in the measured brownish black polyisocyanate with relative density of about 1.09. Component CPII5235 (amount of sand is 1%), start timing, fill the box immediately after mixing, at room temperature from the timing of 15-30min to release.
Only when the binder is bonded to the bulk, the strength of the sand depends on the cohesive strength of the cured binder. In order to achieve a certain degree of molecular weight of the cured binder, the molar ratio of NCO to OH should generally be controlled. Between 0.8-1.5.
Some people used polyoxypropylene ether polyol (N-220/N-330 mixture), polyisocyanate to prepare the self-hardening sand adhesive, and studied the ratio of glycol and triol, molar ratio of NCO to OH and other factors. For the effect of the strength of the self-hardening sand, it was found that when nNco/noH=1.1-1.2, the strength reached a maximum value, and when the polyol excess or the isocyanate greatly excessive, the strength of the sand mold will be affected.
Bonding of used rubber
Polyurethane prepolymers can be used for the recycling of used rubber. After the used rubber products such as used tires are crushed (eg, crushed by freezing method), the obtained powder, granules, and fiber scraps can be bonded together with a binder to form a composite material. Rubber granules are usually bonded with polyurethane adhesives to obtain elastic materials, which are mainly used for sports and entertainment venues, kindergartens' plastic flooring materials, floor tiles, etc., especially for sports grounds and school playgrounds. The general use of polyurethane is The main material, rubber particles are auxiliary materials, because polyurethane has excellent wear resistance, has been widely used in foreign countries, the domestic development is also very fast. For example, BaYer Co., Ltd. has earlier introduced paving materials, Rekonml, domestic Jiangsu Institute of Chemical Industry, and Nanjing Plastic Factory, a plastic track company, to introduce such products earlier. The crushed fiber particles in the waste rubber tires are sieved and bonded with foaming polyurethane adhesive to make sound insulation, heat insulation and other materials.
1. Paving materials
Polyurethane plastic paving materials used in sports grounds, playgrounds, entertainment venues, and indoor floors have the advantages of comfortable, wear-resistant, non-slip, waterproof, etc. The outdoor playgrounds covered with plastic can be protected from the rain, improving athletes' performance and reducing bruising. opportunity. The paving materials are all plastic type (mainly made of polyurethane, not containing rubber), mixed type, double type, folding type, etc., and mostly mixed type. The mixed type is a urethane rubber layer containing waste rubber particles, with a thickness of about 10 kilos, and a rubber particle as a non-slip friction layer on the surface. The double-layered-death layer is a polyurethane adhesive layer, and the lower layer is a rubber-coated polyurethane layer; the folding type is a portable rubber sheet, and the rubber sheet is a waste tire rubber 1 part, a polytetrahydrofuran-type polyurethane prepolymer. 1 part, 0.1 parts of MOCA is poured and cured in a mold after mixing.
Among these surfacing materials, a NCO-containing polyurethane prepolymer or a two-component liquid system composed of a cross-linking agent is a binder for waste rubber particles. Polyurethane prepolymers are generally made of raw materials such as polyoxypropylene glycols and triols and excess mI or MDI, and the NCO content is about 10%. The adhesive is based on a polyurethane adhesive. The amount of binder is 1/4 to 4 times that of rubber pellets. At present, the amount of adhesive used in domestic stadiums' plastic surfacing materials is approximately 4 times that of waste rubber pellets, and paving materials with a small amount of adhesive can be used in kindergarten hallways and playgrounds. In soft plastic floors, it is not easy to fall.
Prepolymers, colorants, catalysts, rubber particles → paving compounds.
Here are a few examples of patent formulations.
A patent from Bayer Company reported that 2000 g of PPG (Mw2000) and 2,4-TD1696g were used to prepare a polyurethane prepolymer with an NCO content of about 3.6%. 2,4'-/4,4' was added to the 2348 g of the prepolymer. - MDI (60/40) 637 g, a binder having a free NCO content of 10% and a viscosity of 1800 MPa·s was prepared. The ground tire particles (1 to 4 mm in diameter), 640 parts, 160 parts of the above binder and 0.32 parts of zinc octylate were uniformly mixed and paved into a rubber layer of 11 to 12 mm in thickness and cured at room temperature for several days. The resulting rubber layer was obtained. The tensile strength is 0.6-0.8 MPa, the elongation is 50%-70%, and the 20% compressive strength is 0.5-0.7 MPa. The material is used for laying the stadium floor.
Japan Mitsui Risoo Polyurethane Co., Ltd. reported that urethane adhesive was prepared from 660 parts of PPC (Mw3000) and MDl340 parts, and benzoyl chloride with 5% of binder quality was added to improve the pot life of the adhesive. 1 part of binder is used for every 4 parts of used tire particles (1-3mm), and there is a pot life of 3h at 35°C and RH 70%. After complete curing, the tensile strength was 1.57 MPa, the elongation was 100%, and the tear strength was 157 N/cm.
Japan's Sanyo Chemicals Co., Ltd. reported that 80 parts of rubber crumbs (2-5mm) were first sprayed with 1% Dabco ethyl acetate solution, dried, mixed with 20 parts of polyurethane adhesive, and poured into a thin layer of 8mm without catalyst treatment. The mixture cures very slowly.
2. Other floor materials
A floor tile is composed of a lower concrete/middle elastic foam layer/surface layer (polyurethane adhesive bonded granular waste rubber). The floor material is wear-resistant and weather-resistant, and can be used for paving on playgrounds, swimming pools, and patios.
One type of mattress consists of rubberized (-25mm) 83% and polyurethane adhesive 17%. The polyurethane binder is two-component, the main agent is PPG-MDI prepolymer (molar ratio of MDI to PPG is 2:1), and the curing cross-linking agent is a mixture of triethanolamine and polyoxypropylene triol (mass ratio l/2), the mass ratio of the main agent to the cross-linking agent is 90:7.5, is molded at 80° C. under a pressure of 3 MPa, and is maturated at room temperature, and has a tensile strength of 3.1 MPa.
3. Sound insulation material
According to several patents, the waste tire fiber was mixed with a polyurethane adhesive and foamed and cured to produce a sound-insulating composite material. For example, Nitto Tire Co., Ltd. of Japan reported that 100 parts of waste tire fibers (0.1-20 mm), PPGI 0 parts, TDI 5 parts, and water 0.5 parts were vigorously stirred in a mixer for 2 minutes and molded at 150° C. and 1 MPa for 10 minutes to obtain a thickness of 10 mm and a density of 0.3. The g/cm3 sheet can be used for the sound insulation layer. An inorganic filler such as iron oxide powder is added to the above system, and a sheet having a density of 1.8 g/cm3 molded by hot pressing can also be used for sound insulation.
Bonding of foam scraps
In the production of polyurethane soft foam, some froth and unqualified waste foams are often generated from foam cutting, and even a considerable amount of used foam is required to be disposed of when used vehicles such as old automobiles are recycled. Incineration produces toxic gases that pollute the environment and is generally not used. There are many methods for recycling waste foams, such as alcoholylated renewable polyols used to make polyurethane rigid foams. However, the most direct method of reuse is to bond the crushed foam to a foamed adhesive and mold it to make a mat or a sound-insulating, heat-insulating material.
Recycled used foam used for bonding should be processed into smaller debris by a crusher. The size of the crushed foam should be as stable as possible and their size has an effect on the properties of the finished product. With the same adhesive, the smaller the debris, the stiffer and more uniform the finished material is for soft foam. Hard foam is usually brittle and breaks more easily than soft foam.
Polyurethane adhesives for foam chip bonding can be either end NCO based prepolymers made of polyether polyols, excess TDI or PAPI, or two-component polyurethane combinations, or both A mixture of raw materials. The binder used for the waste polyurethane foam is generally a polyether polyol and TDI system, and the rigid foam adhesive is preferably an MDI polyisocyanate system. The amount of binder is based on the performance requirements of the product, and is generally between 5% and 50%, with 10%-25% common. The binder can be mixed directly with the foam crumbs or sprayed onto the foam crumbs (the adhesive can contain solvents to reduce the viscosity and control the amount of binder solids, if necessary). It is generally necessary to use a blender to mix the binder and the crushed material (the crumb is glued to the crumb). The foam scrap containing the binder is heated, pressurized and molded into a mold.
For hard foam debris, the crushed foam mixed with the adhesive can be made into a loose slab and heated and pressed into a molded part. Molding temperature is generally above 120°C. Molding pressure can be selected within a relatively large range according to the density of the slab and the required density of the product. The molding time depends on the molding temperature, the thermal conductivity of the raw material, and the thickness of the product. Mold release agent shall be applied to the inner side of the upper and lower plates of the mold. To meet the special requirements of surface quality or bending strength of the product, paper materials or other decorative materials may be applied between the mold plate and the surface of the product and molded together.
The performance of the article depends on the type of crumb, the amount of adhesive, and the density of the article. For example, using the same adhesives and scraps to produce products of different densities, the properties can be varied within a certain range.
The adhesive formulation for crushed foam can be varied, and several representative formulations are shown below.
Example 1: A polyurethane prepolymer having an NCO content of 31.1% was prepared from polyoxypropylene glycol and excess TDI as a binder and sprayed onto polyurethane rigid foam chips. 100 parts of Polyurethane Hard Foam Debris Use 15 parts of the polyurethane adhesive, mix evenly, spray a small amount of triethylamine aqueous solution, press at 120°C for 2 minutes, and then leave for a period of time, the obtained heat insulation sheet has a compressive strength of 0.11-0.13 MPa.
Example 2: A polyurethane binder having a NCO content of 13.5% was prepared from 100 parts of polyoxypropylene glycol (Mw2000) and 108 parts of PAPI and diluted to 50% concentration with toluene. 70 kg of flexible polyurethane foam chips were sprayed with 7 tons of the above adhesive solution and stirred well, pressed in a mold and heated with steam to obtain a mat having a density of 0.06 g/cm3.
Example 3: 12.1 parts of toluenediamine polyether (hydroxyl value 400 mgKOH/g), 2.2 parts of polyoxyethylene glycol (PEG, Mw200), 12.1 parts of PEG (Mw400), polyether polyol (hydroxyl value 39 mgKOH/g) 4.5 parts, 2.0 parts of silicone surfactant, 0.2 parts of PEG solution of 50% potassium acetate, and CFC-1136 parts of one part of the adhesive, PAPI1 part of the other part of the adhesive, after the two parts are mixed The adhesive was sprayed onto 280 g of crushed polyurethane rigid foam (d=0.045 g/cm3, size ≈10 mm), immediately covered with a release paper, and hot-pressed at 100° C. for 10 min to obtain a molding with a density of 0.085 g/cm3. Coefficient 0.021W/(m·K), 150°C, 72h size change <0.1%, water absorption ≤ 1%. The isocyanate-containing trimerization catalyst of the adhesive forms a heat-resistant isocyanurate after curing. The resulting product is a heat and water resistant thermal insulation material.
It is also possible to use a polyurethane foam composition as a binder to bond the corresponding soft or hard waste foam scraps. Due to the short cream time of polyurethane rigid foam and high-rebound combinations, these foam-based adhesives have a short pot life, and machine operations are generally required to bond foam chips.
Waste foams of other materials such as PS foam and polyolefin foam can also be bonded with polyurethane adhesives, such as a fast cure consisting of polyether polyols, organotin/amine catalysts, pigment pastes, methylene chloride and PA shells. 1000g of polyurethane foam adhesive and 5200g of waste PVC foam particles with a particle size of about 8mm were mixed and molded at room temperature for 45min to obtain a soundproof material.
Microcapsules
The microcapsules are composed of a capsule wall and contained liquid or solid materials, and are widely used in carbonless paper, medicines, and agricultural chemicals. Carbonless copy paper made of gelatin or gum arabic as a wall material is the most widely used. The materials used for microcapsule wall membranes include natural resins such as gelatin, as well as synthetic resins such as polyamides, cellulose derivatives, PVA, polyurethane, and polystyrene. The preparation methods and uses are various.
The microcapsules of polyurethane outer wall materials are mainly prepared by chemical methods such as interfacial polymerization and in-situ polymerization. Can be used for the protection and isolation of dyes, spices, pesticides, adhesives and other substances. The concave microcapsules are generally obtained by dispersing a polyisocyanate in a hydrophilic liquid, and can be prepared by adding a polyamine or a polyhydric alcohol that can react with NCO, in combination with a human capsule wall. The smaller the polyisocyanate molecule used, the easier it is to disperse, and the easier it is to adjust the particle size. For example, with the HDI/TMP adduct, microcapsules with very good particle size can be obtained.
Recently, Nippon Daiichi Pharmaceutical Co., Ltd. has introduced a series of water-dispersible PU resin micro-encapsulated microcapsule formulations using vegetable oil spirits, pesticides, and spices as core materials and can function as blankets, wallpapers, and seat cushions. Sexual processing agents, such as mosquito repellent, deodorant, and fragrance, contain 20% of active ingredient, pH 3-5, viscosity of 500-1500mPa·s, and emulsion particle size of 5mm. The main characteristics of this type of PU microcapsules are: no yellowness, microcapsule wall thickness can be adjusted, can be volatile in water or air, and can be used with various adhesives.
Polyurethane adhesive
1. Films for food flexible packaging
The thickness and characteristics of the substrate film for food flexible packaging are shown in Table 14.
2. Dry compound adhesive
Dry compounding refers to the use of an adhesive to bond two kinds of film substrates together. After the adhesive is applied to the substrate film, it is dried by heating to remove the solvent and undergo a chemical reaction and compounded (pressed). Therefore, the dry compound is called Process. In wet compounding, the adhesive is applied to a substrate film. Before the adhesive is dried, the other substrate film is affixed and then the cured film is dried or dried. This process is called Wet compound. There are at least one material with good moisture permeability, such as paper, wood, and woven fabric, among the wet film base films. If the composite substrate has poor moisture permeability, such as plastic film and aluminum foil, the solvent will always vaporize, and defects such as air bubbles, peeling, etc. will occur when the substrate is not penetrated. Therefore, the wet compounding is limited by the substrate film, and only relatively low-grade composite packaging materials can be manufactured, such as cigarette packaging paper in which paper and aluminum foil are compounded.
1. Advantages and disadvantages of dry compounding process
(1) Advantages The substrate film has a wide range of choices, and can be made into two-layer, three-layer, four-layer and multi-layer composite films, which have high composite fastness and can achieve peel strength of up to 9.8N/15mm. Therefore, a high-strength, high-performance composite product such as a high-temperature cooking bag can be produced. Compounding speed is relatively fast, generally 150-180m/min, up to 250m/min. Composite films can be printed on the surface or reversed. In addition, the composite film produced has high dimensional accuracy and excellent heat sealing properties.
(2) Disadvantages Adhesives are used, so there are residual organic solvent residues and contamination of the ring diameter. The base film having a low softening point tends to contract when passing through the hot air passage, and is easily deformed. The thickness of the substrate film requires higher precision.
2. Adhesives for composite packaging films have properties
In the dry compound process, the adhesive is a key factor affecting the film quality performance, so the adhesive for food packaging composite film should have the following properties.
(1) Adhesive Composite packaging films are made of a variety of different materials and are bonded together with an adhesive. Therefore, the adhesive must have good adhesion to various films. If only one of them sticks firmly, and the other film does not, it cannot be operated. Substrates used in composite packaging films include plastics, aluminum foils, papers, and the like, while plastics come in various types and their surface characteristics are different. Facing so many complex materials, adhesives must have the ability to bond two different materials at the same time.
(2) The flexibility of composite packaging materials has been widely welcomed, and light and flexible is very important. Nowadays, plastic-based composite materials are called soft packaging materials. In addition to being soft and collapsible, the adhesive itself must have this property. If the film is hard, brittle and unfoldable, it loses the meaning of packaging.
(3) Heat Resistance Many food packagings are subjected to high temperatures (180-220°C) during manufacturing operations. For example, when heat sealing a bag, the temperature of the hot knife sometimes reaches 220°C to make the composite film into a bag. In addition, after many food composite films are packaged, they must be subjected to high-temperature sterilization and sterilization. For example, steamed foods are subjected to high-temperature cooking and sterilization at 121 to 135°C/30 minutes, and yoghurts and jams are also subjected to high temperatures of 80 to 100°C. . This not only requires that a variety of substrate films withstand the test of high temperatures, the adhesive used must also withstand the test of high temperatures. If the adhesive can only be used at room temperature, but not high temperature, after the high temperature treatment, the original composite substrate film to peel off, it is not a composite packaging film. This must be carefully considered when choosing adhesives.
(4) Cold resistance Many foods are cold-stored or frozen after being packaged, which requires the packaging film itself to withstand low temperatures. If the adhesive hardens at a low temperature, brittle, delamination, peeling, degumming and other phenomena are not acceptable. Sometimes it is possible to require heat-resistant and cold-resistant packaging at the same time. The type of adhesive must meet the requirements.
(5) The anti-media food itself is a very complex composition of substances, water, oil, salt, wine, as well as spicy, spices, and even acetic acid, citric acid, lactic acid, sugar, sulfides, oxides and so on. In the face of these complex components, after being packaged, they are subjected to high-low temperature treatment and long-term storage tests. To maintain the integrity of the packaging film, in addition to the excellent resistance to media erosion of the substrate film itself, the stability of the adhesive is also important. To be able to teach the erosion of various media, otherwise it will cause layered peeling of the composite film, losing the packaging effect.
(6) Safe and hygienic food packaging Composite film protects and the life of the package is people's direct population. In order to be responsible for the health and safety of consumers, not only the substrate film is tasteless, odorless, and non-toxic, but also used. Adhesives must also have the same performance, and safety and sanitation are major issues that countries around the world are paying attention to. China has already formulated a hygiene standard for multi-packaging materials (GB9683-88).
In addition, there are certain requirements for the appearance, transparency, flowability, cold resistance (non-freezing), initial tack, and sizing operations of the adhesive.
3. Composite film adhesive for ordinary packaging
Ordinary packaging composite film polyurethane adhesive generally includes dried food (also called light product) packaging glue and 70-100°C boiling-sterilized distillery packaging adhesive. Such adhesives are two-component solvent-based polyurethane adhesives. The home agent is a polyurethane or polyurethane polyol containing hydroxyl groups (called a component) modified by an aromatic isocyanate. The solids are aromatic isocyanates and trihydroxyls. Methyl propane adducts (called the B component). When used, the A component and the B component are mixed in a certain proportion, and then diluted with ethyl acetate to a certain concentration for sizing coating.
Instructions
Adhesive use method is reasonable to directly affect the quality of the composite film, each brand of adhesive has its own characteristics, must be detailed before using the manufacturer's instructions for use. The basic methods for compounding, coating, and compounding and curing are briefly described here (for details, see Dry Composite Film Preparation Process).
(1) Glue preparation According to the adhesive product specification, determine the ratio of the A and B components (see the table). Working concentration of the adhesive used is 25% - 40%, the diluted solvent is ethyl acetate, the content of ethyl acetate is ≥99.8%, the water content is not more than 300*10-6, the content of ethanol is ≤0.02%, the content of acetic acid Less than 0.005%. When diluting, it is required to add ethyl acetate to the main agent, stir it well, add the curing agent to the diluted main agent, and stir it evenly. The generally prepared adhesive is stored in a closed container and can be used for 1-2 days without significantly affecting the quality of the composite film.
(2) The amount of glue applied (g/m2 calculated from the amount of dry glue) is one of the important factors affecting the bond strength of the composite film. The amount of glue must be determined according to the purpose of the composite film and the material of the film. See Table 15 for the amount of rubber compounded film.
(3) Composite and curing The adhesive coated film is dried in a drying tunnel at 50-80°C. The composite roll temperature is controlled at 50-90°C and the composite pressure is 0.25-0.4 MPa. The composite film usually needs to be left at room temperature (not less than 20°C) for more than 8 days to fully cure. In order to shorten the curing time, the aging temperature can be performed at 40-65°C and the aging time is 24-48h.
4.121 °C retort sterilization composite film adhesive
The resistance to 121 °C retort sterilization composite film adhesive for the preparation of medium temperature cooking bag (121 °C sterilization 30min). Japan's resistance to 121 °C retort sterilization packaging composite film polyurethane adhesive varieties and technical indicators in Table 16 below.
1 Toyo Ink Manufacturing Company of Japan.
2 Dainippon Ink Chemical Industry Company products.
5.135 °C high temperature cooking sterilization film adhesive
The 135°C high temperature resistant composite film is mainly used in the manufacture of high temperature cooking bags. The high temperature steaming bag was developed in the United States in the 1960s and used for astronauts food packaging. It is placed at room temperature for long life. When it is eaten, it can be eaten cold and can be hot food. It is convenient to use and saves saved energy. Therefore, it is very popular among people. In 1964, Japan's Otsuka Food Co., Ltd. succeeded in using high-temperature cooking bags (transparent) to package curry foods. In 1970, Japan sold 70 million high-temperature cooking bags, but sold 100 million in 1971. Until now, sales of high-temperature cooking bags have continued to grow at an annual rate of 15%.
The characteristics of high-temperature cooking bag are: 1 can kill all bacteria, long shelf life, transparent like more than 1 year application period, opaque aluminum foil (middle) bags have 2 years of food preservation period; 2 oxygen permeability and transparency Very low wetness, no spoilage of the contents; 3 Can use canned food production technology and equipment, so high-temperature cooking bags are also called soft cans; 4 sealing is reliable, easy to operate; 5 bags leave a crack, easy to open, with hand One tear or unsealing; 6 decoration printing beautiful; 7 can be heated within 3min; 8 waste is easy to handle; 9 can be stored at room temperature.
Usually, all pathogenic bacteria will be killed at a temperature of 85°C, but botulinum and spore bacteria with a high risk of toxicity will be killed at 135°C for 10 minutes. Therefore, polyurethane adhesives for forging composite films are required to be cured. Resistant to 135 °C.
Example 1: (Main agent: Poly terephthalic acid - isophthalic acid - azelaic acid - ethylene glycol - epoxy resin)
Dimethyl terephthalate (194.2 g), ethylene glycol (248.3 g), and zinc acetate (0.2 g) were passed through a transesterification reaction at 160-220°C. After methanol was distilled off, 83.1 g of isophthalic acid was added. The esterification reaction is carried out at 200-220° C., the water formed by the reaction is distilled off, and then 282.3 g of sebacic acid is added, and the esterification reaction is carried out at 220-230° C., and the pressure is slowly reduced, and the mixture is condensed at 220-230° C. for 60 min and then reduced. Pressing to 133 Pa and condensing at 220-230°C for 4 hours produced a polyester polyol having a number average molecular weight of 50,000.
The polyester polyol prepared above was dissolved in 67 g of ethyl acetate, 2 g of phthalic anhydride, 0.1 g of phosphoric acid, and 15 g of epoxy resin (Epikote 1002) were added and heated and stirred at 60° C. for 4 hours to obtain a solid content of 50% viscous. Liquid (main agent).
The curing agent was an IPDI trimer containing 17.3% NCO% and a solution with a solids content of 50% using ethyl acetate.
According to the main agent: curing agent = 100: 7.5 (parts by mass) formulated into an adhesive.
The composite film was structured as a polyester film (12/um)/adhesive/aluminum foil (9um)/adhesive/unstretched polypropylene (70um), and the bonded film was cured at 50°C for 3 days. The composite film was cut into test pieces of a size of 360 mm*15 mm, and the peel strength was measured on a tensile machine. The peel strength of the aluminum foil and unstretched polypropylene film was 1250 g/15 mm.
The composite film was made into a food bag of 13cm*l7cm in size, and contained vinegar with a concentration of 4.2%. After being sterilized by hot water at 135°C for 30 minutes and 0.45 MPa pressure, the composite film was not found for 7 days at 60°C. Separation phenomenon. After the heat and acid resistance test, the peel strength of aluminum foil and polypropylene film is 1000g/15mm.
In the adhesive component, a 1% Y-glycidoxypropyltrimethoxysilane (KH-560) coupling agent is added, which is superior in heat and hydrolysis resistance.