The hottest solvent-free compound is a production

2022-08-11
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Solventless compounding: a production process worthy of high attention (middle)

III. adhesives for solventless compounding

adhesives for solventless compounding, including one-component adhesives and two-component adhesives. The one-component adhesives originally developed are mainly used for compounding composite products containing paper layers; Solvent free compounding machine is also used for compounding plastic films after adopting humidification device. Later, a two-component adhesive was developed, which can be used for the composite of various substrates; Recently, a one component solvent-free adhesive using UV excitation curing, namely UV curing solvent-free adhesive, has been developed

(I) one component solvent-free adhesives

one component solvent-free adhesives include polyester polyurethane and polyether polyurethane. Their common feature in molecular structure is that the end groups are isocyanates, the development of China's plastic machinery. The main advantages of one component solvent-free adhesive are easy to use and long application period, but there are also some major defects, mainly:

(1) it depends on the moisture on the surface of wood and in the air to solidify, and the amount of glue is limited. At about 2g/m2, this amount of glue is still insufficient in some applications

(2) slow curing speed and long curing time

(3) carbon dioxide is generated during curing, and bubbles will be generated if it is not handled properly (before the two plastic films are bonded, the interaction between adhesive and water should be basically completed to generate: chemical reaction of carbon dioxide)

(4) insufficient curing and low bonding strength when water is insufficient.

(II) two component polyurethane solvent-free adhesive

this solvent-free adhesive is composed of two components: the main agent (polyurethane prepolymer with hydroxyl end group) and the curing agent (polyurethane prepolymer with isocyanate end group). When used, the two components of adhesive are mixed in a certain proportion, and then coated on the substrate to be compounded to make it fit, After curing, the two components of the adhesive produce chemical reaction and cross-linking, showing a good bonding effect. There are two kinds of solvent-free adhesives, cold adhesive and hot adhesive. The molecular weight of cold adhesive is small, and it can be constructed at a lower temperature, but the initial bonding strength is low, and it needs to be matured for a long time before it can be processed such as cutting and bag making; The thermal coating adhesive has high molecular weight and high viscosity at room temperature (the viscosity can reach more than 100000 MPAs at 20 ℃), so it must be heated to a higher temperature (generally 60~100 ℃) before coating processing. Its advantage is that its initial viscosity is high, and after compounding, it can be post processed only after a short ripening time according to the plan

(III) UV curable one component solvent-free adhesive

at present, cation curable products are used, mainly acid catalyzed epoxy system. Under the irradiation of UV, the photoinitiator (Lewis acid) in the adhesive decomposes, causing epoxy block polymerization, and the three-dimensional intersection of epoxy resin is obtained to prepare for installation; Joint structure. The cationic curing mechanism allows the adhesive to be exposed to the atmosphere before compounding. Under the irradiation of ultraviolet light, its cross-linking speed is much faster than that of ordinary polyurethane adhesive, and it can reach a fairly high bonding strength within a few minutes to an hour after compounding, which is enough to ensure the smooth progress of subsequent processing.

(IV) representative examples of solvent-free adhesives

1 See Table 1 for the polyurethane solvent-free adhesive (introduced by Henkel, Germany) of Beijing Research Institute of chemical industry

Table 1 polyurethane solvent-free adhesive of Beijing Research Institute of chemical industry

ur5505 one component wet curing type ur5506 one component wet curing type ur8150/ur7330 two component type

main agent ur8150 curing agent ur7330

solid content%100 100 100 100

viscosity/MPa. S 600 ± 300 (100 ℃) (100 ℃) 4000 ± 500 (20 ℃) 6000 ± 1000 (20 ℃)

service temperature/℃ 85~100 85~100

mixing ratio/mass fraction 100 70

color light yellow transparent light yellow transparent opaque light yellow transparent

density 1.02 1.08 1.16 1.20

high adhesion strength to aluminum foil V

transparent composite pasteurella and boiling water test V V V V

digestibility of transparent composite V V

Pasteurella test of aluminum containing composite V

.Boiling water of aluminum containing composites Test V V

note: V means good

2. See Table 2 for several solvent-free adhesives from Herberts, Germany

Table 2 several solventless adhesives of Herberts company

lfl90x3 one component adhesive 2k-lf541/curing agent 100 2k-lf500a, so it is impossible to obtain the maximum load Pb, so the strength limit can not be obtained σ B/curing agent 424

main agent curing agent main agent curing agent

solid content/% 100 100 100 100

viscosity/mpa S 7000 ± 1000 (100 ℃) 2500 ± 500 (70 ℃) 2700 ± 500 (25 ℃) 5000 ± 1000 (25 ℃) 5000 ± 1000 (25 ℃)

mixing ratio/parts by mass - 100 40 100 60

coating temperature/℃ 80-100 70 40

gluing amount/8 (M2) -1 0.8-4.5 × 1-2 1-2

note: lfi90 × 3. Gluing amount

(1) absorbent base material is 2.5-4.5g/m2,

(2) non absorbent base material is 0.8-1.5g/m2,

3. See Table 3 for the solvent-free adhesive liofol of Henkel (Henkel) Company in Germany

Table 3 solvent free adhesive liofol

ur7740/ur6065 ur7750/ur6070 ur7750/ur6090

main agent curing agent main agent curing agent main agent curing agent

solid content 100 100 100 100 100

ratio 61 6120 1

5 1

viscosity/MPa. S 1500 (75 ℃) 1300 (70 ℃)

purpose vacuum aluminized aluminum foil, cooking products

42 Institutes of the National Aerospace Corporation are also engaged in solvent-free adhesives.Development and Research on, There are also reports of polyester castor oil solventless adhesives, but there are no industrialized products

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