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Kuranska M.,Cracow University of Technology | Aleksander P.,Cracow University of Technology | Mikelis K.,Latvian State Institute of Wood Chemistry | Ugis C.,Latvian State Institute of Wood Chemistry
Composites Science and Technology | Year: 2013

The rigid polyurethane (PUR) composites with an apparent density of ca. 300kg/m3 were prepared using 4,4-diphenylmethane di-isocyanate, polyether polyols, an amine catalyst, silicone surfactant and water as a chemical blowing agent. This reference petrochemical formulation was modified with renewable components such as rapeseed oil-based polyols and flax fibers. The effects of the different contents of the two types of the bio-polyols and flax fibers on the mechanical and thermal properties, dimensional stability and water absorption of foamed PUR composites were investigated. The modification showed that the incorporation of bio-components may improve mechanical and thermal properties of final products. © 2012 Elsevier Ltd.

Zoldners J.,Latvian State Institute of Wood Chemistry | Kiseleva T.,Latvian State Institute of Wood Chemistry
Holzforschung | Year: 2013

Polycarboxylic acids (PCAs) aroused interest as crosslinking agents for natural polymers, such as cellulose, starch, chitosan, and hemicelluloses (HC), for improving their water resistance and imparting them new properties. Here, PCAs were studied for the crosslinking of HC films. HCs were isolated from gray alder (Alnus incana L.) wood as a water-soluble fraction by sawdust extraction with 7% potassium hydroxide. Citric acid (CA), maleic acid (MA), and butane tetracarboxylic acid (BTCA) served as crosslinking agents in the presence of sodium hypophosphite as a catalyst. The crosslinking reaction was followed by the analysis of free and esterified COOH groups in HC films. At temperatures below 100-110 C, the HC esterification process with BTCA proceeded very slowly. At 140 C, most of the acids' COOH groups reacted with HC during 1-1.5 h. BTCA had a higher esterification activity than CA and MA. The obtained films retained their form on immersing in water and subsequent drying in the open air. The water retention value of films followed the reaction kinetics, that is, decreased with increasing reaction time. Water-resistant films were obtained with no <10-11% of BTCA and 20% of CA based on the weight of HC. The water vapor sorption capacity of the films after modification with 10% BTCA decreased approximately twice in the whole range of the relative humidity of air compared with the case of unmodified HC films. © 2013 by Walter de Gruyter Berlin Boston 2013.

Meija-Feldmane A.,Latvian State Institute of Wood Chemistry
Research for Rural Development | Year: 2015

Scots pine (Pinus sylvestris L.) is the most common wood species in Latvia. It is classified as not durable, therefore additional protection against microorganisms is needed prior its use outdoors. Presently Cu-containing wood preservatives are commonly used, but the biggest drawback is the poor Cu fixation, therefore raising concerns about the impact on the environment. Three types of specimens were used to carry out the experiments - untreated, Latvian originated Scots pine; Scots pine commercially treated with preservatives that belong to a group of Cu-boron-triazole (CBA) products; and Scots pine, impregnated with micronized-Cu solution using a standard full cell process. In order to make sure that all of the specimens are equal in their components, elemental analysis was performed and content of nitrogen (1.2 - 2.5 g kg-1), carbon (485.5 g kg-1), oxygen (456.0 g kg-1) and hydrogen (55.6 g kg-1) was determined. The treated specimens were leached according to the European standard EN 84. For micronized-Cu impregnated Scots pine the total Cu content in leachates obtained by atomic absorption spectroscopy was 0.15 mg g-1 of wood, and 0.06 mg g-1 of absolute dry matter with CBA preservative impregnated Scots pine wood. Subsequently, according to the European standard EN 113, treated Scots pine blocks were exposed to brown-rot fungus Coniophora puteana and to white-rot fungus Trametes versicolor for 16 weeks. Mass loss for wood treated with micro-Cu was 48.4% (484 g kg-1) and 1.5% (15 g kg-1) respectively, but for CBA - 49.5 % (495 g kg-1) and 1.2% (12 g kg-1). Both samples proved to be inappropriate for outdoor use (use class 3).

Latvian State Institute of Wood Chemistry | Date: 2014-12-24

The present invention relates to the method for production of heat-insulating material based on rigid polyurethane foam. The method makes possible to expand the raw materials base for production of heat-insulating materials without using components obtained from petroleum and vegetable oils. In the method for production of heat-insulating materials based on rigid polyurethane foam, by combination of isocyanate component with the polyol component, a complex formed by an industrial lignin non-soluble in organic solvents, which is oxypropylated, and then is combined with unmodified lignin in the course of the reaction in ratio from 7:1 to 2.3:1, is used as polyol component. Before being oxypropylated, unmodified lignin is previously oxidized by using POM/ H_(2)O_(2) (polyoxometalates/hydrogen peroxide) system. The object of the present invention is achieved also by that unmodified lignin before combining with oxypropylated lignin is activated in an impact-type disintegrator increasing the total content of hydroxyl group and availability thereof to chemical interaction. The object of the present invention is also achieved by that unmodified lignin before being combined with the main component of polyol system - oxypropylated lignin, is oxidized in POM/ H_(2)O_(2) system. Thus, lignin, which has not been utilized earlier for production of heat-insulating material based on rigid polyurethane foam, is used as one of the main raw materials, furthermore, the characteristics of the obtained material correspond to similar commercially available materials.

Latvian State Institute of Wood Chemistry | Date: 2014-10-01

Invention relates to processing cellulose-containing raw material and namely obtaining levoglucosan from wood. The raw material is treated by 10-40 % sulphuric acid, hydrolysed with superheated steam at a temperature of 110-140C and a pressure of 0.2- 0.5 MPa. Then the product obtained is washed with demineralised water till pH 3.5. This method yields up to 30.9 % of cellulose.

Latvian State Institute of Wood Chemistry | Date: 2015-04-29

Disclosed is a method for producing spray applied polyurethane coatings on metal constructions. The polyurethane coating is obtained by mixing isocyanate component with polyol component wherein the polyol component contains catalytically active vegetable oil polyol that is synthesized by transesterification of vegetable oil with triethanolamine at molar ratio 1.0:2.0 to 3.0. Moreover the polyol component also comprises chain extender, thixotropic agent, molecular sieves, antifoaming agent and nanoparticles. The volume ratio of isocyanate and polyol component is 1.0 to 1.0. The method provides the production of smooth polyurethane coatings on metal constructions in upright position, and on the inside walls of potable water tanks.

Latvian State Institute of Wood Chemistry | Date: 2015-03-04

The invention relates to methods and apparatus, designed for the chemical processing of outer birch bark for obtaining triterpene compounds - betulin and lupeol as well as suberinic acids, used in the chemical and pharmaceutical, food and cosmetic industries. The technical task to be solved with this invention is to develop a simple and efficient method for the chemical processing of outer birch bark for obtaining betulin, lupeol and suberinic acid salts in one apparatus and one outer birch bark processing cycle. According to the present invention, the advanced technical task is attained by a method for chemical processing of outer birch bark, wherein the betulin from the previously ground outer birch bark is isolated with organic solvents in a closed extraction technological complex with the solvents recovery and the return of the condensate in the recycle, the extract flow is passed through a crystalliser, and then the extract is passed to an evaporator, a heater and a condenser, and the condensed Solution is introduced to the extractor again. In the crystalliser, the crystalline betulin is settled, but lupeol is isolated by crystallisation from the precipitate in the evaporator. After accomplishing the extraction process, the outer birch bark in the extractor is depolymerised, using KOH. The proposed method and apparatus enabled realising the complex obtaining of betulin and lupeol, as well as suberin derivatives in the continuous process with the solvent recycle, wherein the yield of betulin and lupeol is enhanced, in comparison with the known methods. Besides, this method made it possible to shorten many times the extraction time, simultaneously enhancing the efficiency

University of Latvia and Latvian State Institute of Wood Chemistry | Date: 2015-01-14

The present invention relates to the technology of plant raw material treatment for obtaining fuel. An object of this invention is to enhance the heating value of the fuel, simultaneously decreasing the energy costs. According to the present invention, the object is achieved by exposure plant raw material pellets to a high-frequency electromagnetic field at frequency in a range of 13.5 MHz to 2.45 GHz during 120-200 s, until the temperature of surface of pellets reaches 410-450K. In the proposed method, the treatment of pellets is carried out at relatively low temperatures (up to 450K), when a thermal decomposition of hemicelluloses and celluloses still does not occur, but the moisture content in the pellets decreases, while increasing the rate of thermal decomposition of pellets, and increasing a heating value thereof, intensifying the burnout of volatile compounds and providing more complete combustion in a domestic heating boiler The activation of the thermal decomposition of pellets and the enhancement of heating value due to microwave pre-treatment may be used also to increase the gasifier capacity and the amount of the energy generated by the integrated gasifier and internal combustion engine

Latvian State Institute of Wood Chemistry | Date: 2015-07-01

The present invention relates to a woodworking industry and may be used for hydrothermal treatment of wood, wood materials, and woodware The object of the present invention is to increase hydrophobicity of wood. According to the present invention the object is achieved by that wood is heated up to 120-160C in a steam atmosphere, in which it is seasoned, and then wood is cooled up to room temperature, and heated during the first stage at a rate 0.16-0.22/min up to 100C, and then the heating rate of obtained steam is decreased up to 0.11-0.13 /min until the temperature of 160C is reached, and wood is seasoned at the temperature of 160C during 1-3 hours at a steam pressure 0.6-0.7 MPa, and cooled up to the temperature of 20C during 6-8 hours. the method of hydrothermal treatment of wood according to the present invention allows increasing hydropphobicity of wood by several times along with saving energy costs. Moreover, hydrophobicity values of treated wood are higher than those of impregnated wood.

Latvian State Institute of Wood Chemistry and University of Latvia | Date: 2015-05-20

The present invention relates to a method for production of fuel pellets from lignocellulosic materials, namely, grass, straw, wood, sawdust, bark and agricultural residues. According to the present invention the object of this invention is achieved by a method for obtaining fuel pellets by mixing preliminary ground lignocellulosic raw material with a binding agent with the further pelletization of obtained mixture, wood bark is used as the binding agent in the amount of 10-20.% by weight of mixture, from which biologically active compounds are extracted with the use of organic solvents. The object of the present invention is achieved by that birch outer bark is used as bark, from which lupeol and betulenol are preliminary extracted, as well as bark of white alder, from which lipophilic compounds, diarylheptanoids and condensed tannins are preliminary extracted. The use of extracted bark of alder and extracted birch outer bark as the additive for pelletization of ground straw:Increases heating value of pelletsIncreases bulk density of pelletsDecreases ash-content of pelletsIncreases energy density of pelletsIncreases parameters of attrition resistance of pelletsDecreases the yield of fine unpelletized biomassPellets on the basis of extracted bark of white alder differ from pellets on the basis of raw bark by higher heating value, higher energy density and higher attrition resistance.

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