Development of Polyurethane Emulsion Adhesive (I)

Abstract: The formulation, preparation process and properties of polyurethane emulsion adhesives based on castor oil and toluene diisocyanate as the main raw materials and tartaric acid as the hydrophilic monomers were reported. The synthesis process and properties of emulsion adhesives were discussed. factor.

Keywords: polyurethane emulsion adhesive castor oil toluene diisocyanate tartaric acid

Foreword:

Polyurethane adhesives have high adhesive strength, soft hardness and other properties can be adjusted, can bond metal, non-metallic materials and other materials, and have excellent resistance to low temperature, oil and other properties, and thus get more and more widely used. However, the currently used solvent-based polyurethane adhesives are volatile, have large odors, pollute the air, and are flammable. They may cause poisoning and harm to the human body. Since the 1970s, the development of water-based polyurethane adhesives has become a new area of ​​application, External research and development are important topics. China has less research on this field. Polyurethane emulsion adhesives are milky white stable mucilages with a particle size of 0.1-1 μm and with water as the dispersion medium. Since the isocyanate group (-NCO) easily reacts with water, the polyurethane resin containing urea bonds is rapidly formed to be hydrophobic and produces a gel in water and agglomerates, and it is technically difficult to obtain a uniform and stable polyurethane emulsion. The process we used was to form a polyurethane prepolymer under anhydrous conditions, introduce a hydrophilic gene into the resin structure, and then disperse it with water to make a self-emulsifying anionic polyurethane emulsion. The experiment used low-cost and rich-source castor oil. And commonly used toluene diisocyanate (TDI) as the main raw material, hydrophilic monomers available on the market easily available tartaric acid. The chain extender was diethylene glycol or 1,4-butanediol. The neutralizer used triethylamine, ammonia, and sodium hydroxide. After exploring the process conditions for preparing the polyurethane emulsion, the orthogonal test design method was used to determine the shear strength of the bonded steel plate as the index, and the ratio of NCO to OH of the prepolymer, the type of chain extender, and the amount of tartaric acid were optimized. temperature reflex.

1 Experimental section

1.1 The main raw materials

Name Specification Source Toluene-2,4-Diisocyanate (TDI) CP Shanghai Reagent Factory Castor Oil CP East China Reagent Supply & Sale Company Tartaric Acid AR Shanghai Reagent One Factory Diethylene Glycol CP Shanghai Reagent Three Factory 1,4-butanediol CP Military Medical Science Station Triethylamine AR Shanghai Reagent No. 3 Ammonia Water CP Shanghai Zhenxin Chemical No. 2 Sodium Hydroxide AR Yixing Water Diversion Aid Plant Butanone AR Shanghai Reagent No. 1

1.2 The main reaction mechanism

The main component of castor oil is the glyceride of 9-alkenyl-12-hydroxyoctadecanoic acid.

1. 3 experimental formula

1.4 Synthetic process

The castor oil was weighed into a reaction with a thermometer, stirrer and air guide. A trickle of nitrogen gas was passed until the end of the reaction and dehydration was carried out at 80 degrees Celsius under reduced pressure for 1 hour. After cooling to room temperature, toluene diisocyanate, chain extender and dried tartaric acid and a small amount of butanone were added, and the temperature was raised to about 55 degrees Celsius. The reaction was incubated for 3 hours. If the system was too viscous, a suitable amount of dibutyl was added during the reaction. Ketone regulation reduces viscosity. Cool to room temperature, add a good solution of triethylamine solution (1:100) with vigorous stirring, add a small amount of butanone, and change the solution from light yellow to transparent milky white. When the pH of the solution reaches 7-8, stop adding drops of triethylamine. The aqueous amine solution was vigorously stirred for about 10 minutes to obtain a uniformly dispersed white emulsion.

1.5 Emulsion performance test

1.5.1 Determination of Viscosity

Measurement of Emulsion Viscosity with Coating--4 Viscometer

1.5.2 Determination of solids content

Weigh 1. 0--1. 5G emulsion sample, weighed W0, placed in a 100-110 eating degree constant temperature oven dried for several hours, weighed to constant weight W, the following formula to calculate the solid content. Solid content% = W/W0*100 1.

5.3 Determination of Density

The relative density of the emulsion was measured using a pycnometer.

5.4 Determination of water resistance

The resulting emulsion was casted on a known weight, clean glass surface to form several pieces of a diameter of 50 MM and a thickness of about 0.2 MM, which was placed in a fume hood at room temperature for 24 hours and was 100-110. The food is dried for 2-3 hours and weighed to a constant weight. The weight obtained is the weight of the glass flake and the weight of the film is W1. The film slide is immersed in distilled water, and one piece is removed every other day, and the surface water is dried with filter paper. Weigh the wet film weight W2, then dry the wet film to a constant weight as described above, weigh the dry film weight W3 after dissolution, and calculate the water absorption and dissolution rate according to the following formula. Water absorption %=W2-W1/W1*100 Dissolution rate %=W2-W3/ W1*100 1.

5.5 Bond Strength Test

(1) Peel Strength The latex was bonded to canvas, cord fabric, PVC artificial leather, etc. and tested at a peel strength of 180°C. The sample size was 15025 (mm), and it was measured on a XL-20 tensile tester at 28°C. test.
(2) Shear strength Emulsion bond aluminum-aluminum plate, steel-steel plate and other test single-lap tensile shear strength, sample size and test method according to GB7124-86, temperature at room temperature 28 °C.