Method for manufacture of splint-slab plates

FIELD: production of building materials, applicable in the wood-working, furniture and building industries.

SUBSTANCE: the method consists in mixing together of wood particles with urea-formaldehyde resin, butadienstyrene methacrylic latex, ammonium chloride and Aerosil, forming of the mat, cold prepressing and hot pressing. The binder instead of ammonium chloride contains ammonium fluosilicate at the following relation of the components, mass percentage: urea-formaldehyde resin - 82.8 to 93.4, ammonium fluosilicate - 0.6 to 1.2, butadienstyrene methacrylic latex - 4.0 to 12.0, Aerosil - 2.0 to 4.0.

EFFECT: enhanced physico-mechanical and ecological characteristics.

2 tbl

 

The invention relates to the production of building materials and can be used in the woodworking, furniture and construction industries.

A known method of manufacturing Spending on the basis of modified latex composition of urea-formaldehyde resins, including the processing of the composite particles of the binder followed by hot pressing (Iossifov and other Properties of chipboard on the basis of modified latex composition of urea-formaldehyde resins. The highest isotech. Institute, Sofia, IX Symposium, 9, 1989, pp. 185-189).

The disadvantages of this method are the use of the best choice latex does not contain carboxyl groups, thickening additives in the form of a latex with a high content of methacrylic groups, and the absence of active filler capable of effectively sorbirovaniya residual formaldehyde. Emissions from ready-made plates of this compounds with carcinogenic and mutagenic properties complicates the use of plates in construction and virtually eliminates their use in the furniture industry.

A known method of manufacturing particleboard from waste wood processing industry, comprising a mixture of wood particles with a binder containing urea-formaldehyde resin, chlorite is th ammonium, mix the best choice carboxylate and methacrylate latexes, emulsifier OP-10, trinacria phosphate and Aerosil, the formation of the Mat, cold-pressing and hot pressing (RF patent No. 2074090, CL 27 N 3/04, 27.02.1997).

The disadvantages of this method are the low strength and water resistance of the plates, as well as technological difficulties associated with the complex composition of the binder.

The closest to the technical parameters is the method of manufacturing Spending (RF patent No. 2176186, CL 27 N 3/02, 08 L 97/02 // (C 08 L 97/2, 61:24) 27.11.2001, bull. No. 33), comprising a mixture of wood particles with urea-formaldehyde resin, the best choice methacrylate latex, ammonium chloride and Aerosil, the formation of the Mat, cold-pressing and hot pressing, binder contains these components in the following ratio, wt.%:

urea-formaldehyde resin - 76,4-93,2

ammonium chloride - 0,8-1,6

the best choice methacrylate latex - 4,0-12,0

Aerosil - 2,0-10,0

A significant drawback of this hardener is the following: when the hydrolysis of the ammonium chloride formed ammonium hydroxide and hydrogen chloride, which is now recognized as carcinogenic to humans. Formed during the hydrolysis of ammonium hydroxide and hydrogen chloride under conditions of high temperature is about (140-170° (C) curing pass into the vapor phase in the form of ammonia and hydrogen chloride, the concentration of which is reduced by removal together with gas environment through the edge of the compression plate material. The latter circumstance adversely affects the uniformity of the cured resin and thereby reduces the mechanical properties of the end plate material.

Object of the invention is the improvement of physico-mechanical properties of the plates, as well as improving the environmental properties of plate materials that expands the scope of their application.

To solve this problem in the method of manufacturing Spending, including the mixture of wood particles with a binder containing urea-formaldehyde resin, Aerosil and the best choice methacrylate latex content in the copolymer chains, wt.%: butadiene - 25, styrene - 20, the formation of the Mat and hot pressing, binder contains as a curing agent ammonium silicofluoride in the following ratio, wt.%:

urea-formaldehyde resin - 82,8-93,4

silicofluoride ammonium - 0,6-1,2

the best choice methacrylate latex (BSMC) - 4,0-12,0

Aerosil - 2,0-4,0

The resulting effect from use as a hardener silicofluoride ammonium can be explained as follows. Silicofluoride ammonium [(NH4)2SiF6] so the ammonium silicofluoride salt of the acid, which is well soluble in water and like ammonium chloride undergoes hydrolysis with the formation of the acidic environment necessary for curing urea-formaldehyde resin. While suggested in this composition, the curing agent has a complex action. Silicofluoride acid strength approaching sulfuric capable at lower concentrations of the curing agent to give required for curing the resin in an acidic environment, as well as possessing insecticidal properties, providing them with slab and materials that become wider range of application. The ammonium cation is contained in the connection twice more than the ammonium chloride, which is a curing agent for the resin in the prototype. This feature ammonium silicofluoride is an advantage, since the hydrolysis produces a greater amount of the weak base is ammonium hydroxide, easy to decompose with the formation of ammonia, which is the active acceptor of free formaldehyde and improves environmental performance of materials and expanding the scope of their application.

When this latex BSMC, requiring no additional thickening and stabilization, has a minimum size of colloidal particles (micelles) and is easily distributed in the urea-formaldehyde resin. In conditions that are characteristic of th is aciego pressing, i.e. at elevated temperatures up to 165°and the presence of an acidic catalyst (ammonium silicofluoride), is more intensive interaction of the carboxyl groups of the latex with methylamine or oxymethylene functional groups of the resin with the formation of three-dimensional - integral structure of the adhesive joint. Introduction BSMC resin in a certain interval allows you to adjust the frequency of "matching" (or Mwith- the molecular weight of the chain between nodes in a three-dimensional polymer) between macromolecules resin. Thus, latex BSMC, acting as auxiliary crosslinking agent for the resin, provides the formation of a more regular, ordered structure utverzhdenii resin, which is characterized by a smaller number of structural defects grid. The latter circumstance contributes to increase cohesive strength of the adhesive joint and the strength characteristics of the plate.

In this case, along with the cohesive strength is provided by the high adhesion of the binder to the surface of the wood particles. A significant role is played by active filler Aerosil (TU 14-922-77), representing a specially made fine silica developed gidroksilirovanii surface. Filling the micropores of wood particles, Aerosil thereby increases the effective area of the bonding of the trees the s particles together. Introducing an oxygen-containing polar substance, Aerosil provides a high degree of saturation by hydrogen bonds between the wood and the polar groups of the composite binder. Physico-chemical properties of Aerosil have a significant impact on the content of free formaldehyde. Probably, Aerosil along with latex actively involved in the process of curing the resin, preventing the formation of vapor-gas bubbles, thus concentrating the residual formaldehyde, and provides the chemisorption last due to the contact of micropores and uneven saturation of the chemical bonds gidroksilirovanii the surface of particles of Aerosil. However, the use as a hardener silicofluoride ammonium reducing the concentration of Aerosil effect observed increased ability silicofluoride ammonium link free formaldehyde. The important fact is that the chemisorption of formaldehyde by Aerosil is carried out at a temperature below the temperature of the pressing Spending. Therefore, in conditions of high-temperature pressing Aerosil no significant effect on the rate of polycondensation processes and thereby decreases the efficiency of the process.

Emission reduction of residual formaldehyde can also be achieved by the ability and formaldehyde to join in the acidic environment of the double bond methacrylate latex.

The method is as follows.

Dried sawdust-sawdust mass in a laboratory drying chamber convective type to a moisture content of 2-4%. Preparing a binder by mixing urea-formaldehyde resin latex composition, aerosol and ammonium silicofluoride.

The concentration of the binder is 57-67 wt.%, viscosity B3-4-150-170 sec. The binder consumption 12% on dry residue to the weight of absolutely dry wood particles. The ratio of chips to filings by weight of 65:35.

Wood particles mixed with binder composition using pneumonocytes in a laboratory mixer. Form a carpet of glued wood pulp with a wooden frame, podpisovat in a cold press and pressed in a hot press at a temperature of plates 150°C, pressure of 2.5-3.0 MPa and a duration of 0.5 min/mm single layer Made of a plate thickness of 12 mm After pressing each plate is cooled in an upright position without blowing at room temperature. Test plates held not earlier than 5 days after production.

In accordance with the present technology has received Board prototype (example 1) and the proposed method, by changing the composition of the binder (examples 2-6 table 1).

Table 1
ComponentsContent, wt.% for example
123456
 (prototype)     
Urea-formaldehyde resin86,896,6for 93.487,282,877,6
Ammonium chloride1,2-----
Silicofluoride ammonium-0,40,60,81,21,4
The best choice methacrylate latex8,02,04,08,0to 12.016,0
(BSMC)      
Aerosil4,01,02,03,04,05,0

Plates with different binder composition produced by the above technologies were subjected to tests on the physico-mechanical properties and its content is one of formaldehyde. The parameters of the tested slabs are shown in table 2.

The content of free formaldehyde, mg/100 g plate
Table 2
IndicatorsExamples
123456
 (prototype)     
The tensile strength in bending, MPa23,9to 19.924,726,925,820,1
The ultimate tensile stress perpendicular to the plate, MPa0,780,760,810,850,820,77
Swelling in thickness, %      
2 hours10,714,39,58,79,218,4
24 hours16,323,214,713,315,122,5
Density, kg/m3731740742731750745
9,211,78,87,28,510,3

As shown in table 2, data plate, obtained by the proposed method have higher strength properties and water resistance, and the emission of free formaldehyde is lower than in the prototype.

A method of manufacturing particleboard from waste wood processing industry, comprising a mixture of wood particles with a binder containing urea-formaldehyde resin, butadiene-styrene methacrylate latex BSMC content in the copolymer chains, wt.%: butadiene 25, styrene 20, methyl methacrylate 20, methacrylic acid 35, and Aerosil, the formation of the Mat, cold-pressing and hot pressing, characterized in that the binder as a hardener contains ammonium silicofluoride in the following ratio, wt.%:

urea-formaldehyde resin 82,8-93,4

silicofluoride ammonium 0,6-1,2

butadiene-styrene methacrylate latex (BSMC) 4,0-12,0

Aerosil 2,0-4,0



 

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SUBSTANCE: the method consists in processing of husk particles by a binder containing urea-formaldehyde resin, ammonium chloride, Aerosil butadienstyrene methacrylic latex, forming of the mat, cold prepressing and hot pressing. The binder instead of ammonium chloride contains ammonium fluosilicate at the following relation of the components, mass percentage: urea-formaldehyde resin - 82.8 to 93.4, ammonium fluosilicate - 0.6 to 1.2; butadienstyrene methacrylic latex - 4.0 to 12.0, Aerosil - 2.0 to 4.0.

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2 tbl, 1 ex

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SUBSTANCE: the method consists in processing of husk particles by a binder containing urea-formaldehyde resin, ammonium chloride, Aerosil butadienstyrene methacrylic latex, forming of the mat, cold prepressing and hot pressing. The binder instead of ammonium chloride contains ammonium fluosilicate at the following relation of the components, mass percentage: urea-formaldehyde resin - 82.8 to 93.4, ammonium fluosilicate - 0.6 to 1.2; butadienstyrene methacrylic latex - 4.0 to 12.0, Aerosil - 2.0 to 4.0.

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2 tbl

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8 cl, 1 tbl

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