Use of polyamine-containing wood materials to reduce formaldehyde content in ambient air
SUBSTANCE: wood materials (i) contain polyamine as binder or binder different from polyamine. The wood materials additionally have polyamine inside or on their outer layer and the polyamine has average molecular weight of not less than 500 g/mol and has at least 6 primary or secondary amino groups per molecule of polyamine.
EFFECT: reduction of formaldehyde in ambient air.
6 cl, 1 tbl, 5 ex
This invention relates to the use of wood materials for the manufacture of furniture parts, wall cladding, insulating materials and the like for reducing formaldehyde in ambient air, with wood materials
(i) contain as a binder polyamine or
(ii) contain a binder that is different from polyamine, and additionally have in the outer layer of wood materials or on their outer layer polyamine,
and polyamine has an average molecular weight of at least 500 g/mol and has at least 6 primary or secondary amino groups.
For the manufacture of wood-based materials have long been used condensation products on the basis of urea, if necessary, melamine, and formaldehyde. The latter are used mainly for production of fibrous or chipboard for furniture production. These resins along with their reasonable price, have the advantage of ease of processing and prolonged viability at a time when high reactivity. However, a serious disadvantage is that the resulting wood materials during processing and thereafter emit formaldehyde.
Also the wood itself can release into the environment of formaldehyde, especially after the heat treatment. In General, wood materials with what richiami have lower formaldehyde emissions compared to substrates without coating ("Holz als Roh und Werkstoff" "Wood as raw material and articles thereof", t, 1989, str).
Above certain boundary concentrations of formaldehyde can cause people allergies, skin irritation, respiratory tract or eyes. Therefore, the reduction of formaldehyde indoors or in the air of residential areas is an important wish.
In DE 4308089 A1 describes a binder for bonding wood, containing a) a polyamine, b) from 0.01 to 0.25 moles of sugar per mole of the amino group a), and (C) from 0.01 to 0.25 moles per mole of the amino group and one or more components from the group consisting of dicarboxylic acids, aldehydes having two or more carbon atoms and epoxides. As polyamine named, for example, polyethylenimine or N,N',N”-Tris(6-aminohexyl)melamine. In the examples described formaldehyde emission, equal to 0.04-0.1 mg NSNO/m2/PM
In EP 1192223 B1 describes a fibrous plate with polyamines or polyamine containing aminoplast resin as a binder. As the adhesive is called amongst the aqueous solution of aliphatic polyamine at least three functional groups selected from the group of primary and secondary amino groups; polyamine has an average molecular weight of from 600 to 1000000 g/mol and in addition to the tertiary amine groups of other functional groups in the main does not. Described that as the preferred polyamine used polyethylenimine is whether polyvinyliden. Also described that polyethylenimine has preferably an average molecular weight of from 800 to 100,000, and polyvinyliden preferably has an average molecular weight of from 5,000 to 200,000.
Therefore, in the prior art there is information about how you can replace the named binder containing formaldehyde. However, in the residential area there are other sources of formaldehyde such as, for example, fabric, chipboard, furniture, especially older furniture, and cigarette smoke.
In SA 1241524 described the use of polyamines as acceptors of formaldehyde. For example, the filters in the heating cover polyamines or polyamine added as additives to paints for the walls.
The objective of the invention is to provide wood materials that can absorb formaldehyde from the ambient air, and these wood materials are already used in a residential zone or useful to integrate into a residential area.
The objective of the invention is solved by use of wood materials for the manufacture of furniture parts, wall cladding, insulation materials, etc. for reducing formaldehyde in ambient air, with wood materials
(i) contain as a binder polyamine or
(ii) contain a binder that is different from polyamine, and additional is but have in the outer layer of wood materials or on their outer layer polyamine
and polyamine has an average molecular weight of at least 500 g/mol and has at least 6 primary or secondary amino groups.
Preferably used polyamine, which have an average molecular weight of at least 800 g/mol and at least 6, preferably at least 10, primary or secondary amino groups. Can be used only one specific polyamine or a mixture of several polyamines. As polyamines preferably choose polyethylenimine or polyvinyliden or mixtures thereof.
The average molecular weight of polyvinylidene is mainly 5000-500000 g/mol, preferably 5000-350000 g/mol, particularly preferably 5000-100000 g/mol. The average molecular weight of polyethylenimine is mainly 500-100000 g/mol, preferably 500-70000 g/mol, particularly preferably 500-50000 g/mol and most preferably 500-20000 g/mol.
For use polyamine in accordance with the case (i):
Polyamine is used as a binder is preferably in the form of aqueous solutions containing solid particles polyamine from 1 to 95 wt.%, preferably from 5 to 80 wt.%. In the case of aqueous solutions of polyvinylidene the solids content is preferably 5-30 wt.%, most preferably 5-15 wt.%. In the case of aqueous solutions of polyethylenimine the solids content sostav the em preferably 10-60 wt.%, most preferably 30-50 wt.%.
The solution polyamine may contain conventional auxiliary substances and additives, such as tools, giving hydrophobicity, for example paraffins, protection of wood or fire-retardant means.
The solution polyamine is applied in the usual way on sawdust cellulose/fiber (cf., ".mdf Mitteldichte Faserplatten" = "MDF - fibrous plates of medium thickness" Hans-Joachim Deppe, Kurt Ernst, 1996, DRW-Verlag Weinbrenner GmbH & Co., 70771 Leifelden-Echterdingen, Chapter 4.3, p.81; see also EP 1192223 B1, paragraph ).
The solution polyamine is used as a binder mainly in such quantities that 100 g of absolutely dry fibers/sawdust is used 0.1 to 20 g, preferably 0.2 to 5 g, particularly preferably 0.5 to 2.5 g polyamine.
Then sawdust or cellulose fibers are pressed in the usual way at the plate. To do this, by Sands sawdust or cellulose fibers on a substrate to form a Mat of wood chips or fibers and the latter are pressed at a temperature of from 80 to 250°C. and at a pressure of from 5 to 50 bar in chipboard (particleboard or fibreboard (MDF) (cf. the above-cited book, Chapter 4.5, page 93 onwards).
Preferably fill cellulose fiber layer of such thickness that after hot pressing the resulting plate density from 100 to 1000 kg/m3p is edocfile from 450 to 900 kg/m 3and a thickness of 0.5 to 200 mm, preferably 1-40 mm, particularly preferably 1.5 to 20 mm
For use polyamine in accordance with the case (ii)
Polyamine or aqueous solutions of the polymers can be applied to the glued wood materials. As a binder can be applied to all known specialist binders for the production of wood-based materials, in particular aminoplast resin.
An aqueous solution of the polymer, in particular obtained by mixing, in each case based on the polymer solution -
(a) 1-99 wt.% polyamine;
(b) 0-5 wt.% additives to improve wettability;
(c) 0-30 wt.% additives to control pH;
(d) 0-30 wt.% other additives such as fungicides, tools,
increasing hydrophobicity, dyes, organic solvents;
(e) 0-20 wt.% urea
and water added up to 100 wt.%, moreover, these data refer to the beginning of the mixing.
An aqueous solution polyamine contains mainly from 5 to 90 wt.% polyamine, preferably 10-75 wt.% polyamine, particularly preferably 15-45 wt.% polyamine, most preferably 25-40 wt.% polyamine, respectively, based on the polymer solution.
As optional components (b) an aqueous solution of polymer can be used ionic and nonionic surfactants for improved what I wettability, such as described, for example, in the Handbook .Stache "Tensid-Taschenbuch", publisher Carl Hanser, Munich, Vienna, 1981, concentration mainly from 0 to 5 wt.%, preferably from 0 to 2 wt.%.
To adjust the pH value by using the following additives, such as the optional component (C): mineral or organic acids, such as, for example, sulfuric acid or formic acid. Component (C) may be added to aqueous solution of the polymer in an amount of from 0 to 30 wt.%, preferably from 0 to 20 wt.%.
As optional component (d) to aqueous solution of polymer may be added other additives, for example additives from the group that includes tools that enhance the hydrophobicity, for example, paraffin wax, and waxes, fungicides, organic solvents or dyes. Component (d) may be added to aqueous solution of the polymer in an amount of from 0 to 30 wt.%, preferably from 0 to 10 wt.%.
As an optional component (e) aqueous solution of the polymer can contain up to 20 wt.% urea based on the polymer solution. Predominantly aqueous solution of the polymer contains less than 15 wt.% urea, preferably less than 10 wt.% urea and particularly preferably less than 5 wt.% urea in each case based on the polymer solution. Most preferably the polymer solution does not contain urea.
Use the : solution polyamine with pH from 3 to 12, preferably from 6 to 11, most preferably pH from 9 to 11.
Apply enough solution polyamine, so that the number polyamine 1 m2the surface of the wood material was 0.1-100 g, preferably 0.5 to 50 g, particularly preferably 1-10,
An aqueous solution of the polymer can be applied to wood materials of different, well-known specialist methods. These include, for example, spraying, rolling, dipping, applying a layer with a doctor blade, smearing or curtain coating. Preferably the amine solution is applied by spraying and rolling, especially by rolling.
Woody materials obtained by the methods (i) or (ii), can be processed further as usual and, in particular, suitable for the manufacture of furniture parts, linings for walls, insulation materials and the like, i.e. subjects/objects of wood, which are in direct contact with air or a source of formaldehyde. So manufactured wood materials preferably used for the manufacture of the rear wall of the furniture.
Preferably wood materials get in the way (i) and therefore do not contain formaldehyde.
Made so parts of furniture, tiles, insulation materials and tomopterna, are not only not containing formaldehyde items, but these items can also absorb formaldehyde from the ambient air and thus reduce the formaldehyde content, for example, in a residential area in a long time.
Was made MDF-plate (30×30 cm)which had a density of 850 kg/m3and a thickness of 4 mm, with the use of a binder consisting of 30 wt.% an aqueous solution of polyethyleneimine (average molecular weight polyethylenimine: 5000 g/mol), while the binder used in the amount of 1.5 grams of solids per 100 g of absolutely dry fibers. The pressing was carried out at the pressure of 4 N/mm2, the temperature pressing of 200°C and time compression 120 C.
Thickness and density MDF-plate selected in accordance with the usual form for the manufacture of the rear wall of the furniture.
Was made MDF-plate (30×30 cm)which had a density of 850 kg/m3and a thickness of 4 mm, with the use of a binder consisting of 30 wt.% an aqueous solution of polyethyleneimine (average molecular weight polyethylenimine: 5000 g/mol), while the binder used in the amount of 3 grams of solids per 100 g of absolutely dry fibers. The pressing was carried out analogously to example 1.
Was made MDF-plate (30×30 cm)which had a density of 85 kg/m 3and a thickness of 4 mm, with the use of condensing urea-formaldehyde resin (Kaurit Leim 340, the solids content of 68%), while the binder used in the amount of 12 g of solid resin per 100 g of absolutely dry fibers. The pressing was carried out analogously to example 1. Then the upper and lower sides of the plates were sprayed with 10 g/m230 wt.% solution polyethyleneimine (average molecular weight polyethylenimine: 1300 g/mol) (active substance: 3 g/m2) and were dried for 24 h at room temperature.
Was made MDF-plate D (30×30 cm)which had a density of 850 kg/m3and a thickness of 4 mm, without using a binder, while the wet fibrous Mat (blank plate) (moisture content 20%) was extruded in a loose plate at the pressure of 4 N/mm2, the temperature pressing of 200°C and time of pressing of 200 C.
Example 5. Particleboard (chipboard) trading as a source of formaldehyde
When it comes to wood-shaving plate E trading quality, which has a density of 670 kg/m3and thickness of 16 mm and a formaldehyde emission of 1.16 mg/l (executory method). Thickness and density particleboard selected in accordance with the usual form for the manufacture of the rear wall of the furniture.
Measurement of formaldehyde emission.
Formaldehyde emission was determined executory method (JIS And 5908). Love the e executone measurement took place on 10 test samples. Measured or 10 samples in the form of plates (plates A-D)or 5 samples (plate E) and 5 samples (plate a or b or C or D). Executory values are summarized in table 1.
|Review executory values|
|The test sample||Executone value [mg/l]|
|DSP E+MDF-plate D||0,80|
The examples show that the formaldehyde that emits in the surrounding air particleboard E, is captured through the use of MDF-plates a, b or C, and thus the possession of formaldehyde in indoor air are effectively reduced.
1. The use of wood materials for the manufacture of furniture parts, wall cladding, insulation materials, etc. for reducing formaldehyde in ambient air, with wood materials
(i) contain as a binder polyamine or
(ii) contain a binder that is different from polyamine, and additionally have in the outer layer of wood materials or on their outer layer polyamine and polyamine has an average molecular weight of at least 500 g/mol and has at least 6 primary or secondary amino groups per molecule polyamine.
2. The use according to claim 1, and polyamine has an average molecular weight of at least 800 g/mol and at least 10 primary or secondary amine groups per molecule polyamine.
3. The use according to claim 1, and as polyamine used polyvinyliden and/or polyethylenimine.
4. The use according to claim 3, and polyvinyliden has an average molecular weight of from 5,000 to 500,000 g/mol, and polyethylenimine has an average molecular weight of from 500 to 100,000 g/mol.
5. The use according to claim 3, and polyvinyliden has an average molecular weight of from 5,000 to 100,000 g/mol, and polyethylenimine has an average molecular weight of from 500 to 20,000 g/mol.
6. The use of wood materials according to one of claims 1 to 5 for the manufacture of the rear wall of the furniture.
FIELD: woodworking industry.
SUBSTANCE: formula of chip and glue composition for an internal layer in production of woodchip boards includes up to 40% of chips from wastes of rotting blanks with application of a binder based on a low-molar urea formaldehyde resin.
EFFECT: reduced material intensity of woodchip boards production, energy intensity of pressing process, increased efficiency of pressing equipment and reduced toxicity of produced boards.
3 tbl, 3 ex
SUBSTANCE: described is a composition for obtaining a binding agent for soaking cellulose fibres. The composition contains polyolefin resin which reacts with 1.6-4.0% maleic anhydride. The composition has less than 1500 ppm free maleic anhydride. The resin has melt flow index at 190°C and 2.16 kg ranging from approximately 0.1 to 500 g/10 min. The composition has yellowing index of 20-70. The polyolefin is polyethylene. Described also is a cellulose composite containing 10-90% cellulose fibre; a first polyolefin resin having melt flow index from 0.1 to 100 g/10 min; 0.1-10 wt % composition for obtaining the binding agent. The maleic anhydride is grafted on the polyethylene.
EFFECT: high binding efficiency of the binder.
12 cl, 8 tbl, 20 ex
FIELD: process engineering.
SUBSTANCE: invention relates to pulp of organic stuff particles for production of ligno-carbohydrate plastic. Said pulp comprises minced particles of conifer needle, coniferous branch bast peeling, timber and wastes of Siberian pine cones in various versions. Said pulp features improved extraction of active natural substances from said components to produced binder.
EFFECT: pulp of organic stuff particles for production of ligno-carbohydrate plastic at reduced temperature of thermal compaction.
11 cl, 11 tbl
SUBSTANCE: polyvinyl chloride-based wood-polymer composition for profiled-trim moulding articles contains polyvinyl chloride, wood flour, a complex stabiliser, an acrylic modifier, polyethylene wax and a metal-containing lubricant. The metal-containing lubricant used in the composition is obtained by reacting higher monocarboxylic acids with glycerin at 130-230°C at molar ratio 1:(1-2) in the presence of oxides of divalent metals Ca, Zn, Mg or their two-component mixtures in weight ratio 0.25-1.0:0.5-1.0 in amount of 0.5-2.0 wt % of the overall reaction mass, where the higher monocarboxylic acids used are VIK, oleic and stearic acid. The composition also uses polyethylene wax with melting point not higher than 100°C. The complex stabiliser used is selected from: BAEROPAN R 9003 (produced by Baerlocher GmbH, Germany) or Naftosafe PEK 922 B (produced by Chemson, Austria). The acrylic modifier used is impact-resistant modifiers selected from: MB-87, DURASTRENGTH D320, DURASTRENGTH D300S (produced by Arkema, France), Metablen P-5500S (produced by Dangdong), Paraloid BTA 736H-S OS (produced by Rohm & Haac), Kane ACE F50 (produced by Kalek), Lariks on TU 2216-235-05757533-2000.
EFFECT: high quality of profiled-trim moulding articles, which is expressed by improved operational and technological parameters, specifically melt flow index, thermal stability, impact viscosity, low water absorption and environmental safety of the composition.
2 cl, 1 tbl
SUBSTANCE: product contains the following in wt %: 1-50 modified hybrid resin based on natural fatty acids and 99-50 natural material selected from cellulose, wood, wood fibre, flax, hemp, starch and another natural fibre or combinations thereof. The product can contain 20-80 wt % thermoplastic, 30-70 wt % binder or natural adhesive. The hybrid resin is obtained via water-emulsion polymerisation of an acrylate monomer - butylacrylate, methyl methacrylate or butylacrylate, on an alkyde resin based on fatty acids in the presence of a radical initiator at 30-100°C. Fatty acids are selected from tall oil, suberin fatty acids, cutin fatty acids, vegetable oils and mixtures thereof. The composite product is obtained by mixing acrylate hybrid and natural material or combination thereof. Further, the product is moulded and hardened under heat at 120-200°C until a composite product of the given type is obtained.
EFFECT: invention enables to obtain composite plates with improved properties, good biodegradability and low toxicity; such properties of the plates are achieved by using modified hybrid resins in form of a stable aqueous emulsion as binding materials and compatibilisers.
22 cl, 1 tbl, 1 dwg, 9 ex
SUBSTANCE: moulding composition contains an aggregate made from carbon-containing crushed plant and/or synthetic fibre material, binder made from inorganic polymers and a target additive. The inorganic polymers used in the composition are metal phosphates with aluminium, chromium, boron and magnesium cations and anions РО4 --- or metal silicates with sodium, potassium and lithium cations and with anions SiO3 --, pre-modified with solutions of organic bases with an amide bond and/or oxides or trihydrates of aluminium oxide or mixtures thereof. The target additive is a water repellent or hardener or surfactant. The aggregate, working solution of the binder and target additive are prepared first. The aggregate is treated with the working solution, dried and moulded into briquettes.
EFFECT: ecologically clean, non-toxic, non-combustible slab materials which are resistant to aggressive media are obtained.
41 cl, 3 tbl
SUBSTANCE: composition contains the following, wt %: 0.05-6.9 (a) bisamide of saturated fatty acid with the structure: , where R1 and R2 are saturated hydrocarbyl groups with C11-C35; 0.14-7.6 (b) bisamide of unsaturated fatty acid with the structure: , where R3 and R4 are unsaturated hydrocarbyl groups with C11-C35; (c) dispersed cellulose material such as wood flour; (d) thermoplastic resin - flakes fractionated from molten high-density polyethylene (HDPE); (e) a finishing agent for finishing the cellulose material (c) with thermoplastic resin (d). The composition also contains an optional (f) inorganic dispersed material selected from pumice and talc and (g) a lubricant, separately or in a combination, selected from zinc stearate, sodium stearate, potassium stearate, paraffin wax or polyethylene wax.
EFFECT: invention enables to obtain composites with improved operational properties, ultimate bending strength and resistance to water absorption.
11 cl, 10 tbl, 31 ex
SUBSTANCE: invention relates to composite products, particularly a composite panel containing hybrid resins based on natural acids, as well as a method of producing a composite product. The product contains the following in wt %: 1-50 modified hybrid resin based on natural fatty acids and 99-50 natural material selected from cellulose, wood, wood fibre, flax, hemp, starch and another natural fibre or combinations thereof. The product can optionally contain 20-80 thermoplastics, 30-70 binder or natural adhesive. The hybrid resin is obtained via condensation of a mixture of natural C12-C20 fatty acids modified with maleic acid or anhydride, and an alkyde resin based on fatty acids of tall oil, suberin fatty acids, cutin fatty acids, plant oil or mixtures thereof. Properties of the panel are achieved using modified hybrid resins in form of a stable aqueous emulsion as binding materials and compatibilisers.
EFFECT: invention enables to obtain composite panels with improved properties, specifically good biodegradability and low toxicity.
17 cl, 1 tbl, 27 ex
SUBSTANCE: wood-polymer composition for articles contains polyvinyl chloride, wood flour, calcium-zinc complex stabiliser and the composition can additionally contain a metal-containing lubricant obtained via reaction of higher monocarboxylic acids with glycerine at 130-230°C in molar ratio 1:(1-2) in the presence of oxides of divalent metals Ca, Zn, Mg or other two-component mixtures in weight ratio 0.25-1.0:0.5-1.0 and polyethylene wax.
EFFECT: high quality of ready articles owing to improved technological parameters of the compositions, thermal stability, melt fluidity, water absorption and environmental safety.
2 cl, 1 tbl
FIELD: wood industry.
SUBSTANCE: invention may be used to extract, recycle and process wood wastes in process of fibreboards production. The method includes supplying waste waters downstream pouring-forming machine into an accumulating-balancing reservoir, its pumping along a bypass pipeline into a disperser with simultaneous air supply from atmosphere into the bypass pipeline, formation of air and water mixture passing through the disperser, supply of air and water mixture into a dynamic absorber to create floating complexes, their supply into a receiving chamber of a flotation plant, separation into foam sent to the pouring-forming machine and treated water supplied to the accumulator. The system for method realisation comprises an accumulating-balancing reservoir for collection of waste waters, a bypass pipeline and a disperser to create air and water mixture, a dynamic absorber to form floating complexes, a floatation plant with a receiving chamber, a foam-producing mechanism and a foam-collecting pocket to separate caught fibre in the form of foam and an accumulator of treated water.
EFFECT: inventions ensure simple and cheap technology for extraction, recycling and processing of internal fibreboard production wastes with the possibility of secondary wood fibre catching and return directly into the process cycle without its additional treatment.
2 cl, 1 dwg, 2 tbl, 1 ex
SUBSTANCE: invention relates to a method of producing frictional polymer materials and can be used in making brake shoes of railway wagons and locomotives, for motor transport, cranes, clutch plates and other articles. The method is realised by processing butadiene or butadiene-nitrile rubber on plastification equipment and mixing the rubber with curing agents, with fibre and powdered filling materials. Aromatic polyamine is simultaneously added with curing additives. The aromatic polyamine is an aniline-formaldehyde condensate consisting of 75% isomers of diaminodiphenylmethane and 3-4 benzene-nuclear primary amines bound by methylene bridges. The fibre filler is pre-saturated for 15 minutes with aqueous solution of epoxy resin which is a product of reacting a mixture of diane and aliphatic epoxy resins with glycols or derivatives thereof, in ratio A:B between 95:5 and 60:40, and then dried to moisture not higher than 1%. The composition of the material contains the following in pts. wt: rubber 100, aromatic polyamine 2-20, sulphur 1-15, thiuram 0.04-2.0, 2-mercaptobenzothiazole 0.3-4.0, fibre filler 15-100, powdered filler 10-100.
EFFECT: invention improves strength characteristics of frictional polymer materials and increases labour safety.
2 tbl, 7 ex
SUBSTANCE: butadiene copolymer latex with methyl(meth)acrylate links or butylacrylate is modified by mixing the latex with 0.8-3.0 wt % polyethylenepolyamine in terms of dry latex after mixing latex and polyethylenepolyamine. A polyester cord is impregnated with the latex composition and bonding strength with SKI-3 based rubber is checked.
EFFECT: improved adhesion properties of latex for impregnating reinforcement textile materials.
1 tbl, 10 ex
FIELD: construction materials production.
SUBSTANCE: invention relates to the production of the construction materials from waists of the wood processing industry; the method comprises filler fractionating and filler processing by the water solution of copolymer vinylcyclohexene with maleic anhydride followed by drying, adjustment of the modified wooden particles with polyethylene by means of mixing and heating followed by rolling on the laboratory rollers with the roller diameter of 180 mm and gapping between them of 1 mm, pressing of the received mass in the press-mould of the hydraulic pressing unit with the mark of origin ПГ-60 at the temperature of 180-210°C and pressure of MPa; the wood-polymer composites (WPC) is induced as an ingredient increasing the mechanical and physical characteristics of the compound and resistibility to UV irradiation, and thereafter the secondary polyethyleneterephthalate in the following proportions (%, mass): secondary polyethylen: 20.0-50.0; secondary polyethyleneterephthalate: 35.0-20.0; wooden particles: 37.5-22.5; CVMA: 2.5-7.5.
EFFECT: implementation of this method allows to increase physical, mechanical and ecological characteristics of the WPC plates.
2 tbl, 1 dwg
FIELD: process engineering.
SUBSTANCE: proposed fiber board is pollution-free material due to use of hardening agent instead of phenol resin. In producing said fiber board by wet process, acrylate and epoxy resins are used instead of phenol resin that do not contain bisphenol - A. Both hardening agents are thermosetting resins, in fact, not reacting at 100°C or lower, but readily reacts to cause hardening at temperature over 140°C.
EFFECT: optimum hardening agents and optimised use of circulation water.
5 cl, 2 dwg, 7 tbl