The use of zola silica as a component of wood boards on the basis of urea-formaldehyde binder

 

(57) Abstract:

The invention relates to technology of a polymeric binder and wood boards. Describe the use of a Sol of silica as a component of wood boards on the basis of urea-formaldehyde binder for increasing the strength and water resistance of the plates and significantly reduce their toxicity. 3 table.

The invention relates to technology of a polymeric binder and wood boards.

Chipboard (Spending) is made mainly on the basis of urea-formaldehyde resin (UFR). Their main disadvantage is the presence of formaldehyde, above the permitted values (0.012 mg/m3air). To reduce the toxicity of FSC and Spending use formaldehyde acceptors [U.S. Pat. 2059456 Russia, MKI6B 27 K 3/52; publ. 10.8.96; bull. N 13; "Timber industry", 1995. -N 15.- C. 9-10], the urea-modified wax emulsion [A. S. 1698334, MKI5D 21 J 3/12; Publ. 15.12.91; bull. N 46], modified lignosulfonates [A. S. 1237433, MKI5B 27 N 3/02; Publ. 15.06.86; bull. N 22]. Numerous additives to reduce the toxicity of Spending given E. Raffaele [formaldehyde emissions from particleboard. -M.: Ecology, 1991. -C. 90-95]. However the ve acceptor formaldehyde it is possible to use a silica Sol.

The Sol of silica (SiO2)nis a colloidal solution, where the silicon atom coordinated by 4 oxygen atom. Concentrated silica sols stabilized hydroxides of alkali metals or ammonium. Sol (SiO2)nget, for example, by decationization of liquid glass using ion-exchange resin /TU 105-ST.PS-01-89. Production of silica in the shop preparing the compositions. Cherepovets steel mill/.

It is known the use of crematoria for the preparation of refractory coatings rail cars (see GOST 105-ST.PS-01-89). In contrast to the alkali metal silicates (water glass) for Zola typical polymer structure with SP above 50000, while in the liquid glass are monomers and oligomers silica /Korneev C. I. Danilov centuries the Production and use of soluble glass (water glass). -L., Stroiizdat.- 1991./ The silica content of alkali metals does not exceed, as a rule, from 0.5 wt.%, whereas in the liquid glass content of alkaline oxides above 9 wt.%. In the process of gelation Zola silica formed a solid siloxane bond /P. Ailer. The chemistry of silica. M World: 1982, so 2.-712 C./.

Usage Zola silica is hydrated effect when using Kremenets in composition with the FSC in accordance with the FSC: the silica Sol 10: (1...3) to obtain chipboard (Spending).

The invention is illustrated by examples (formulations is given in tab.1, the properties of the binder - table.2, the properties of the Spending - in table.3).

As the hardener compositions of the binder used ammonium chloride in the amount of 2% by weight of the abs. dry binder.

Analysis of the results of the test are given binder compositions (table. 2) showed a positive effect of the introduction of Zola silica in the composition FSC: increased the degree of cure of the binder, which was assessed by the amount of residual formaldehyde and the content of water-soluble substances, as well as increased 1.5 times the bond strength of wood. Binder containing silica Sol, had high viability over 24 hours, was distinguished by the uniformity of structure, the introduction of liquid glass (sodium silicate) and FSC in the same conditions resulted in coagulation of the polymer. Even a small amount of glass worsen the polycondensation of urea-formaldehyde binder.

The positive effect of the introduction of Zola silica in CFS may be associated with the formation of hydrogen bonds between groups and the reactive centers FSC (nitrogen, methylol or carbonyl groups of the polymer). Increasing the strength of the glue connection perform in the polymer role of strengthening and reinforcing agent. When the content of Zola in the composition of the FSC more than 30 wt.% the pH of the binder increases to 8.5...9,0 that slows down and complicates the process of polycondensation polymer.

Chipboard as a binder contained urea-formaldehyde resin and the silica Sol (PL.3). The temperature of the pressing 1605oC, the maximum specific pressure of 2.0 MPa. Used birch wood, dried to a moisture content of 2%. Another batch of plates was made of wood, the pre-treated silica Sol in an amount of 1% by weight of the abs. dry wood and dried to the final moisture content of 2%.

The data presented demonstrate that the introduction of polysilicon acid - Zola (SiO2)nin the composition of the FSC and/or wood in these quantities increases the strength and resistance of the plates and substantially reduces from toxicity, which was evaluated according to GOST 27678-88. Punch method for the determination of formaldehyde content.

As studies have shown that this effect is associated with a decrease in sorption of formaldehyde wood particles using Sol of silica for the modification of wood particles, in addition, noted the fact that the binding Sol (SiO2)nas a component of the urea-formaldehyde binder and as a modifier of wood particles in the production of chipboards reduces toxicity and increases the strength of the plates.

The use of Zola silica as a component of wood boards on the basis of urea-formaldehyde binder.

 

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