Low solids content (generally solid content 18-20%), high moisture content (minimum 80%), high drying costs, and low speed.
High water content, especially in the production of sandwich panels in winter, is easy to deform.
The film is brittle and has low shear strength and is not suitable for making stress or secondary products. Biological resistance and moisture resistance are not good enough to make the field of application of this adhesive very limited.
Synthetic resin adhesives accounted for 70-80% of the adhesive bonding family in recent years. Because of its high bonding strength, the film is tough, moisture-proof and water-resistant, it has long been used by people, and it has an increasing share in the paper honeycomb market. Practice shows that improving the technological content and product quality of cellular products is the right way to innovation.
Section III Formulation and Application of Commonly Used Paper Honeycomb Adhesives 1. Formulation and Application of Modified Corn Starch Adhesives 1. Formulation
Corn starch hydrogen peroxide 30%
Sodium hydroxide
Tributyl phosphate
Boron-broken
Dispersant
Additive PVA Drier
Water Wt% 18-20 2.0
1.0-1.8
A small amount of 0.1-0.5
0.5
0.5
1.0
4-6 72.9-73.7
2, the process in the total amount of one-half of the water by adding PVA stirring heated to 98 ° C, so that it completely dissolved. Decompose to 60°C and add cornstarch to stir and heat to 60min for modification. Add hydrogen peroxide and sodium oxide to stir for half an hour. Add tributyl phosphate, borax, and disperse and complex for 40 minutes. Add the additives and driers to mix well.
3. Results and Discussion 3.1. Effects of PVA PVA and corn starch are polyhydroxyl (R-OH) macromolecule compounds. Partially oxidized corn starch also contains some hydroxyl groups (R'OH) which form dehydration under certain conditions. The (R'OR) network structure significantly improves the bonding strength. Drying speeds up.
Table 1 Effect of PVA Content on Initial Adhesion of Adhesive
0
1 2 3 Initial tack (%) Break rate 10min 45 65 85 90 93
Table 2 Effect of PVA Content on Drying Rate
Content Item 0 0.5 1 2 3 Initial tack: Initial tack 15 14 12 12 10 (min) Full tack 30 30 25 20 20 Viscosity (mpa·s) 80 90 90 95 100 Drying time (h) 3.0 2.7 2.3 2.0 2.0
From Tables 1 and 2, adding 1% PVA can increase the initial adhesion force from 45% to 85%, and the drying speed can be reduced from 3h to 2.3h. Increase the amount of PVA and increase the cost. It is better to consider adding 1.0% PVA.
3.2. Calcium-based soils are converted to calcium-based bentonite on the sodium base. The amount of water absorbed is small, and it is easy to delaminate. Sodium leather has a large amount of water absorption, good suspension, no precipitation, and stable quality.
It is important to use calcium-based soils first to convert them into sodium-based soils. Alteration method: 15 g of Na2Co3 was added to 150% calcium-based soil. The modification was carried out. The mixture was stirred well and water was added and allowed to stand for 24 hours before use.
3.3. The purpose of sodium-based bentonite modified corn starch glue added to the sodium base is to accelerate the drying of the glue layer, which can effectively block the pores of the surface of the paper fiber and prevent the moisture in the adhesive from penetrating into the interior of the paper to achieve the purpose of quick drying. After several experiments, the following table shows the relationship between sodium bentonite content and corn starch adhesive properties:
Table 3 Relationship between bentonite content and adhesive properties
content(%)
Item 0 2 4 5 6 Initial adhesion: Initial viscosity 15 10 8 8 8 (min) Total viscosity 30 25 17 15 15 Viscosity (mpa·s) 80 100 150 250 300 Drying time (h) 3.0 2.5 2.0 1.8 1.5
Based on the comprehensive analysis, the suitable amount of sodium bentonite is 4%.
Second, polyvinyl acetate emulsion modification and application of polyvinyl acetate in the thermoplastic resin occupies an important position, mainly for indoor furniture, wood products processing, paper, fiber, leather, books, decoration, etc., porous material sticky Paper and paper honeycomb structure production.
1. Composition 1.1, main agent vinyl acetate (VAC)
Vinyl acetate is vinyl acetate. Formula: CH3COOCH=CH2
Colorless flammable gas, sweet mellow, slightly soluble in water (25g/L). Easy to polymerize, gas has low toxicity.
1.2 Dispersants Deionized water or condensed water is usually used as a dispersion medium. The amount of water added is generally 60%-80% of the total mass.
1.3. Initiators are commonly used initiators peroxide, such as ammonium persulfate, potassium persulfate, hydrogen peroxide and so on.
The amount of monomer is 0.1%-1.0%. Industrial use of ammonium persulfate is high because the solubility at room temperature is high (20% or more).
1.4. Emulsifier The role of emulsifier: It can make the water-soluble monomer VAC and the water-insoluble PVAc evenly and stably dispersed in the water phase. Commonly used emulsifiers have an oxime-based compound as an emulsifier at one end of the molecule. Such as PVA, OP-10, etc., the amount of VAC