RU2381895C2 - Method for production of modified wood - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method for production of modified wood includes impregnation of wood with modifier and further thermal treatment, besides modifier used is represented by product of emulsion copolymerisation of ethyl acrylate with sterol Emucryl S or product of emulsion copolymerisation of acryl monomers Emucryl M, impregnation of wood with Emucryl S or Emucryl M is carried out at the temperature of 18-22°C for 3 days, and thermal treatment is carried out at the temperature of 80°C for 10 hours.

EFFECT: improved water resistance of wood with preservation of its strength and durability.

3 dwg, 2 tbl

Description

The invention is used in construction to increase the water resistance of wood while maintaining its strength and durability.

For the analogue, wood was modified with a composition based on alkyd resin with the addition of styrene (RF patent No. 4895489).

The disadvantage of this invention is the toxicity of the modifier.

As a prototype, wood modified with a composition based on urea-formaldehyde resin was adopted (RF patent No. 5055017).

The disadvantages of this material are its low biostability and water resistance.

Technical task: to increase the water resistance of wood while maintaining its strength and durability.

This technical problem is achieved by modifying natural wood with emucryl M or C. Emucryl M (TU 6-36-5800146-264-91) is an aqueous dispersion of a copolymer of ethyl acrylate with methyl acrylate and ethylene glycol dimethacrylic ether and is used as a component of hardening and coloring compositions in the production of paper and textile (e.g. silk fabrics) materials. Emucril C (TU 6-36-05800142-265-92) is a product of emulsion copolymerization of ethyl acrylate with styrene, obtained by the interaction of ethyl acrylate, styrene, emulsifier, soda, ammonium persulfate and is used for hard finishing of cotton fabric and its mixture with polyester fibers . Table 1 presents the technical requirements for these polymeric substances.

Modification of wood (pine of the 2nd grade) was carried out as follows: it was impregnated with emucril at a temperature of 18 ÷ 22 ° C for 3 days, and then heat treatment at a temperature of 80 ° C for 10 hours.

The duration of technological operations was determined by the results of short-term compression tests (Fig. 1).

Table 1 Technical requirements for emucril No. p.p. Name of indicator Emucril M Emucril C one Appearance milky white liquid milky white liquid 2 Mass fraction of nonvolatile substances,% 40 ± 1 40 ± 2 3 Mass fraction of volatile monomers,% no more 0.005 - four Mass fraction of volatile monomers (ethyl acrylate + styrene),%, no more - 0.005 5 The activity indicator of hydrogen ions, units pH 7.0 ÷ 8.5 7.0-8.5 6 Mass fraction of iron,%, no more 0.01 0.005 7 Density, g / cm ³ 1,055 ± 0,004 1.04 ± 0.005 8 Resistance to electrolytes (aqueous solution with a mass fraction of MgCl ₂ · 6H ₂ O 3% and an aqueous solution with a mass fraction of NH ₄ CI 11%) - steady

When wood samples are impregnated with emucryl M or C, a sharp increase in their mass is observed. For emucril C, it reaches its maximum value after 72 hours, and emucril M after 168 hours. The impregnation process is accompanied by an increase in the size of wooden samples, which indicates that not only voids are filled with emucril, but also its penetration into the walls of wood cells.

When wood is saturated with emucril in the first 24 hours, its strength drops sharply, after which it rises again and reaches its maximum value for 3 days: 100% of the strength of natural wood for emucril M and 72% for emucril C (Fig. 1, a )

To improve the properties, the impregnated wood samples were subjected to heat treatment at a temperature of 80 ° C. As a result, the monomer is polymerized and crosslinked with wood substance molecules. In the first 2 hours, a decrease in strength is observed, which is caused by softening of the polymer, and then its sharp increase. Maximum strength reaches after 10 hours of heating.

The study of the physicomechanical characteristics was carried out for wood modified with emucril according to the optimal regime, i.e. impregnated with monomer for 3 days at a temperature of 20 ° C and subjected to heat treatment at a temperature of 80 ° C for 10 hours. The results are presented in table 2

table 2 Physico-mechanical characteristics of wood modified with emucryl M or C No. p / p Indicator Natural wood Modified wood Emucril M Emucril C one Density, kg / m ³ 550 600 600 2 Destructive stress, MPa: - during compression 57.6 50.53 55.6 - when chipping 4.84 2.65 - - with transverse bending 82.97 101.1 109 3 The deformation modulus in compression, MPa: - along the fibers 10,000 13065 - - across the fibers 5000 5305 - four Water absorption by weight,%, per - 2 hours 37 8 fourteen - 24 h 51 22 - - 30 days 114 81 - 5 Thickness swelling,%, per - - 2 hours 4.2 2 - - 24 h 4.2 - - - 30 days 4.8 4.8 - 6 Residual compressive strength,%, after exposure to water for - 2 hours twenty 25 -

- 24 h twenty 23 - - 30 days twenty 22 - 7 The coefficient of linear thermal expansion α × 10 ^-6 , 1 / ° C 2.83 0.84 - 8 UV resistance coefficient during - 100 h 1.14 1,07 1.24 - 200 h 1.19 0.78 - - 300 h 1.30 0.87 - 9 Frost resistance after 50 freeze-thaw cycles 0.75 0.78 - 10 Durability (time to failure) at a temperature of 16 ° C and a stress of 70 MPa with transverse bending 9 years - > 100 years eleven Durability at a temperature of 16 ° C and a hardness of 20 MPa 3.2 g - > 100 years

As can be seen from table 2, the use of emucryl C and M as a modifier can significantly increase the water resistance of wood while maintaining its frost resistance. So, its water absorption in 2 hours is reduced by 3-4.5 times, in 24 hours - by 2.5 times, and the residual strength increases by 1.1 ÷ 1.25 times. The use of these modifiers can also increase transverse bending strength (1.3 times), hardness (1.3 times) and wood durability (tens of times) (Fig. 2).

It should also be noted that, in contrast to existing modifiers (methyl methacrylate, styrene, phenol-formaldehyde resins, etc.), emucril is environmentally friendly.

The authors propose the following technology for wood modification with emucryl M and C:

- wood impregnation with monomer at a temperature of 20 ° C for 3 days: in this case, emucril C is absorbed 6.5% of the mass of wood, and emucril M-7.5%;

- heat treatment of impregnated wood at 80 ° C for 10 hours

Modified wood of the proposed monomer has:

- increased water resistance and frost resistance;

- increased strength in lateral bending;

- increased hardness;

- environmental safety.

Claims (1)

A method of producing modified wood, including impregnating wood with a modifier followed by heat treatment, characterized in that the emulsion copolymerization product of ethyl acrylate with styrene Emucril C or the product of emulsion copolymerization of acrylic monomers Emucril M is used as a modifier, wood is impregnated with Emucril C or Emucril M at temperature 22 ° C for 3 days, and heat treatment at a temperature of 80 ° C for 10 hours