CN100554358C - A kind of wood adhesive and preparation method thereof - Google Patents

Abstract

The invention relates to a wood adhesive and a preparation method thereof, belonging to the technical field of wood-based panel production. The adhesive is formed by polycondensation of formaldehyde, urea, melamine and phenol; the molar ratio of urea, melamine and phenol is 11.5:7.6:1; the molar ratio of formaldehyde/(urea+melamine+phenol) is 1-1.2:1. Its preparation method is to add melamine and phenol on the basis of synthesizing urea-formaldehyde resin, adjust the formaldehyde solution to be alkaline, add urea for the first time, react at a temperature of 80°C-90°C for a period of time, adjust the pH to be acidic, and add the second Secondary urea, after reacting for a period of time, add urea for the third time, add melamine and formaldehyde solution, adjust the pH to be alkaline, add phenol and formaldehyde at the time, react to the end, adjust the pH value to be alkaline, add the last urea, and finally Synthesize a high performance wood adhesive. The wood adhesive of the invention has the advantages of strong bonding force, low formaldehyde emission, high water resistance, etc., and is suitable for the production of outdoor-grade wood-based panels and moisture-proof wood-based panels.

Description

A kind of wood adhesive and preparation method thereof

Technical field:

The invention relates to a wood adhesive and a preparation method thereof, belonging to the technical field of wood-based panel production.

Background technique:

Urea-formaldehyde resin is a kind of adhesive with the largest consumption in my country's wood processing industry because of its abundant raw materials, low price and excellent performance. However, it also has the disadvantages of poor water resistance and large formaldehyde emission, which are limited in application. With the enhancement of people's awareness of environmental protection, the control requirements for the release of free formaldehyde are becoming more and more stringent, the molar ratio of urea-formaldehyde resin is getting lower and lower, and the reduction of the molar ratio of formaldehyde (F)/urea (U) will lead to the deterioration of the overall performance of the resin At the same time, the market has put forward higher requirements for the moisture-proof and water-resistant performance of wood-based panel products, which have put forward higher requirements for the performance of urea-formaldehyde resin. There are many ways to modify urea-formaldehyde resin (UF), and according to the needs of different products, the modification methods are also different. Among them, the realization of co-condensation resin is one of the best of these methods. It adds other compounds to the original resin to cause co-condensation reaction, endows the adhesive with new properties, and achieves the purpose of modifying the original resin. Now melamine is commonly used to modify urea-formaldehyde resin in production. The addition of melamine is helpful to improve the internal bonding strength, formaldehyde emission, thermal stability and other properties of the board. At the same time, melamine has a ring structure and has six active groups. , which largely promotes the cross-linking of UF resin to form a three-dimensional network structure, and at the same time blocks many water-absorbing groups, such as CH ₂ OH, etc., thereby greatly improving the water resistance of UF. However, MUF resin also has some disadvantages. For example, it has certain requirements for storage temperature. Generally speaking, storage temperature lower or higher than 25°C will reduce its storage period. In addition, since melamine is used in the resin, the cost of the resin increases with the amount of melamine used.

Through document search, do not see the public report identical with the present invention.

Invention content:

The purpose of the invention is to overcome the deficiencies of the prior art, modify the synthetic urea-formaldehyde resin, and provide a wood adhesive and a preparation method thereof.

Wood adhesive of the present invention is formed by polycondensation of formaldehyde, urea, melamine, and phenol; Wherein:

a. The molar ratio of urea, melamine and phenol is 11.5: 7.6: 1; the molar ratio of formaldehyde/(urea+melamine+phenol) is 1-1.2: 1;

b. The appearance of the wood adhesive is a transparent light yellow-brown emulsion, the solid content is 53-65%, the viscosity is Tu-4 cup 17-19s, the density is 1.26-1.27g/cm ³ , the pH is 8.2-8.8, and the gel time is 75 -95s, the storage period is 2-3 weeks.

The preparation method step of wood adhesive of the present invention is as follows: (the following parts are parts by weight)

a. Take 718-1096 parts of 37% formaldehyde, adjust the pH value to 8.5-9.5 with NaOH, add 259-330 parts of urea, raise the temperature to 80-90°C, keep it for 15-30 minutes, and adjust the pH value to 4.0-5.0 , until ice fog appears;

b. Use NaOH to adjust the pH value to 5.8-6.8, add 148-188 parts of urea, heat to 90°C, and keep for 10-20 minutes;

c. Add 106-134 parts of urea and keep for 5-15 minutes;

d. Adjust the pH value to 8.5-9.5 with NaOH, add 1793-2281 parts of melamine and 2148-3282 parts of formaldehyde;

e. After the temperature reaches 90°C, use NaOH to adjust the pH value to 8.0-8.8, keep it for 10-30 minutes, add 176-224 parts of phenol and 189-289 parts of 37% formaldehyde, react until the solution becomes clear, and adjust it with NaOH pH to 8.0-8.8;

f. Then lower the temperature to 80°C and add 890 parts of urea. When the temperature is lowered to 35°C, adjust the pH value to 8.0-8.8 with NaOH to obtain a wood adhesive.

The equipment used in this method is conventional equipment.

Compared with the prior art, the present invention has the advantages of high bonding strength, good water resistance, greatly reduced release of free formaldehyde, and lower production cost than MUF resin, and is especially suitable for the production of outdoor-grade wood-based panels and moisture-proof wood-based panels.

Detailed ways:

Embodiment 1: (every part is parts by weight, gram or kilogram)

The adhesive is formed by polycondensation of formaldehyde, urea, melamine and phenol; among them:

a. The molar ratio of urea, melamine and phenol is 11.5:7.6:1; the molar ratio of formaldehyde/(urea+melamine+phenol) is 1.0:1;

b. The appearance of the wood adhesive is a transparent light yellow-brown emulsion with a solid content of 53%, a viscosity of Tu-4 cups of 17s, a density of 1.26g/cm ³ , a pH of 8.2, a gel time of 75s, and a storage period of 3 weeks.

The preparation method step of wood adhesive is as follows:

a. Take 718 parts of 37% formaldehyde, adjust the pH value to 8.5 with NaOH, add 259 parts of urea, raise the temperature to 80°C, keep it for 15 minutes, adjust the pH value to 4.0, until ice fog appears;

b. Use NaOH to adjust the pH value to 5.8, add 148 parts of urea, heat to 90°C, and keep for 10 minutes;

c. Add 106 parts of urea and keep for 5 minutes;

d. adjust the pH value to 8.5 with NaOH, add 1793 parts of melamine and 2148 parts of formaldehyde;

e. After the temperature reaches 90°C, adjust the pH value to 8.0 with NaOH, keep it for 10 minutes, add 176 parts of phenol and 189 parts of 37% formaldehyde, react until the solution becomes clear, and adjust the pH value to 8.0 with NaOH;

f. Then cool down to 80°C and add 783 parts of urea. When the temperature is down to 35°C, adjust the pH value to 8.0 with NaOH to obtain a wood adhesive.

Embodiment 2: (every part is parts by weight, gram or kilogram)

The adhesive is formed by polycondensation of formaldehyde, urea, melamine and phenol; among them:

a. The molar ratio of urea, melamine and phenol is 11.5:7.6:1; the molar ratio of formaldehyde/(urea+melamine+phenol) is 1.1:1;

b. The appearance of the wood adhesive is a transparent light yellow-brown emulsion with a solid content of 65%, a viscosity of Tu-4 cups of 19s, a density of 1.27g/cm ³ , a pH of 8.8, a gel time of 90s, and a storage period of 2.5 weeks.

The preparation method step of wood adhesive is as follows:

a. Take 907 parts of 37% formaldehyde, adjust the pH value to 9.5 with NaOH, add 294 parts of urea, raise the temperature to 90°C, keep it for 30 minutes, adjust the pH value to 5.0, until ice fog appears;

b. Use NaOH to adjust the pH value to 6.8, add 168 parts of urea, heat to 90°C, and keep for 20 minutes;

c. Add 120 parts of urea and keep for 15 minutes;

d. adjust the pH value to 9.5 with NaOH, add 2037 parts of melamine and 2715 parts of formaldehyde;

e. After the temperature reaches 90°C, adjust the pH value to 8.8 with NaOH, keep it for 30 minutes, add 200 parts of phenol and 239 parts of 37% formaldehyde, react until the solution becomes clear, and adjust the pH value to 8.8 with NaOH;

f. Then lower the temperature to 80°C and add 890 parts of urea. When the temperature is lowered to 35°C, adjust the pH value to 8.8 with NaOH to obtain a wood adhesive.

Embodiment 3: (every part is parts by weight, gram or kilogram)

The adhesive is formed by polycondensation of formaldehyde, urea, melamine and phenol; among them:

a. The molar ratio of urea, melamine and phenol is 11.5:7.6:1; the molar ratio of formaldehyde/(urea+melamine+phenol) is 1.2:1;

b. The appearance of the wood adhesive is a transparent light yellowish-brown emulsion with a solid content of 60%, a viscosity of 18s for 4 cups, a density of 1.265g/cm ³ , a pH of 8.5, a gel time of 95s, and a storage period of 2 weeks.

The preparation method step of wood adhesive is as follows:

a. Take 1096 parts of 37% formaldehyde, adjust the pH value to 9.0 with NaOH, add 330 parts of urea, raise the temperature to 85°C, keep it for 20 minutes, adjust the pH value to 4.5, until ice fog appears;

b. Use NaOH to adjust the pH value to 6.0, add 188 parts of urea, heat to 90°C, and keep for 15 minutes;

c. Add 134 parts of urea and keep for 10 minutes;

d. adjust the pH value to 9.0 with NaOH, add 2281 parts of melamine and 3282 parts of formaldehyde;

e. After the temperature reaches 90°C, adjust the pH value to 8.4 with NaOH, keep it for 20 minutes, add 224 parts of phenol and 289 parts of 37% formaldehyde, react until the solution becomes clear, and adjust the pH value to 8.4 with NaOH;

f. Then lower the temperature to 80°C and add 997 parts of urea. When the temperature is lowered to 35°C, adjust the pH value to 8.4 with NaOH to obtain a wood adhesive.

The inventor obtained wood adhesives by using the above examples, which were respectively used in the production of wood-based panels such as plywood, particle board, medium density fiberboard, building formwork, etc., and proved that the adhesive has high bonding strength, good water resistance, can greatly reduce the release of free formaldehyde, production The cost is lower than that of MUF resin.

Claims (2)

1, a kind of wood adhesive is characterized in that this tackiness agent by formaldehyde, urea, and trimeric cyanamide, the phenol copolycondensation forms, wherein:

A. the mol ratio of urea, trimeric cyanamide, phenol is 11.5: 7.6: 1; The mol ratio of formaldehyde/(urea+trimeric cyanamide+phenol) is 1-1.2: 1;

B. the wood adhesive outward appearance is transparent khaki emulsion, and solid content is 53-65%, and viscosity is to be coated with-4 glasss of 17-19s, density 1.26-1.27g/cm ³, pH is 8.2-8.8, and gel time is 75-95s, and the shelf lives is 2-3 week.

2, the preparation method of the described wood adhesive of claim 1 is characterized in that preparation method's step is as follows:

A. get the formaldehyde of 718-1096 part 37%, every part is weight part, down together, to 8.5-9.5, adds the urea of 259-330 part with the NaOH adjust pH, is warmed up to 80-90 ℃, keeps 15-30 minute, and adjust pH is to 4.0-5.0, up to ice fog occurring;

B. use the NaOH adjust pH to 5.8-6.8, add the urea of 148-188 part, be heated to 90 ℃, kept 10-20 minute;

C. add 106-134 part urea, kept 5-15 minute;

D. use the NaOH adjust pH to 8.5-9.5, add the formaldehyde of 1793-2281 part trimeric cyanamide and 2148-3282 part;

E. after the temperature to 90 ℃, to 8.0-8.8, kept 10-30 minute with the NaOH adjust pH, phenol of adding 176-224 part and the formaldehyde of 189-289 part 37%, it is clear to be reacted to solution becomes, with NaOH accent pH to 8.0-8.8;

F. cool to 80 ℃ subsequently and add 783-997 part urea, when cooling to 35 ℃, adjust the pH value to 8.0-8.8, obtain wood adhesive with NaOH.