UDC 674.812

V.G. Dedyukhin, V.G. Buryndin, N.M. Mukhin, A.V. Artemov

PRODUCTION OF PRODUCTS BY PRESSING IN CLOSED PRESS FORMS FROM PHENOPLASTS WITHOUT ADDING BINDERS

The results of studies of the technological properties of a press composition made of wood particles without adding binders and the physical and mechanical properties of plastics from these compositions are presented; The influence of low molecular weight (organic and inorganic) modifiers, as well as water in the process of formation of plastics, was studied.

Key words: wood plastic, urea, Raschig fluidity, sanding dust, plywood.

The timber reserves in Russia are estimated at 80 billion m3. The degree of its use is 65...70%, and only 15...17% is processed using chemical and chemical-mechanical methods (the world level is 50...70%). At hydrolysis enterprises, 1.5 million tons per year of hydrolytic lignin are accumulated in terms of dry matter.

One of the rational directions effective use wood processing waste - obtaining from them press materials (wood pressing masses) based on phenol and urea-formaldehyde resins. However, the introduction of 11 to 35% synthetic binders into these compositions increases the cost of the boards and makes them environmentally unsafe.

Therefore, wood plastics obtained without the addition of binders are of great interest. The feedstock can be not only small wood particles, but also hydrolyzed lignin and plant residues annual plants(flax and hemp bonfire, cotton stalks, straw, etc.). In the work of A.N. Minin called this material piezothermoplastic.

At USFTU, work is underway to obtain materials from wood and other plant waste without adding binders: since 1961, in open molds (between heated plane-parallel plates) - lignocarbohydrate wood plastic, since 1996, in closed molds - wood plastic without binder (DP-BS).

The technology for producing boards and products from wood plastics without a binder is not widely used due to the long pressing cycle, since the plastic is cooled in a mold under pressure (low productivity of equipment and tooling, and high heat consumption). We have proposed a technology for pressing products based on the use of external molds and air as a heat and coolant. At the same time, productivity increases by 5 or more times compared to traditional technology for such press materials, heat consumption is significantly reduced.

One of the disadvantages of wood press compositions without the addition of binders is their low fluidity. For example, the fluidity of DP-BS from wood waste (fraction 0 ... 2 mm) using the method of pressing a flat disk sample at a humidity of 10% is 78 mm, and at 20% -95 mm; the Raschig fluidity of this press composition at a humidity of 10% is 9 mm, and at 20% - 29 mm.

The cheap raw material for the manufacture of DP-BS is sanding dust from the production of plywood (TTTP-F) and particle boards (ShP-DStP). So, with a chipboard production volume of 100 thousand m3/year, the amount of produced ShP-chipboard is 7.5 thousand tons. The work shows that ShP-DStP can be used in the production of phenoplast grade 03-010-02, which meets the requirements of GOST 5689-86 (see table).

Composition and properties of phenolics based on wood flour and ShP-DStP

Indicator Indicator value for filler

Wood flour ShP-DStP

Compound, %:

phenol-formaldehyde resin 42.8 37.5

wood filler 42.6 42.0

methenamine 6.5 7.0

mummy 4.4 -

lime (magnesium hydroxide) 0.9 0.7

stearin 0.7 0.6

kaolin - 4.4

nigrosin 1.1 -

Properties:

bending strength, MPa 69 66...69

impact strength, kJ/cm2 5.9 5.9...7.0

electrical strength, kV/cm 14.0 16.7.17.2

Dependence of the properties of the press material based on ShP-F without adding a binder on humidity (at a humidity of 13%, modification with urea was carried out): a - shear resistance; b - modulus of elasticity in bending; c - fluidity according to Raschig; g - fluidity on the disk

The purpose of this research is to develop a formulation of DP-BS based on ShP-F and to find optimal pressing modes for products with properties close to those of phenoplast 03-010-02.

In terms of fluidity, DP-BS based on ShP-F is significantly inferior to phenolic plastics, so products of simple configurations can be made from it. The fluidity of the material according to Raschig and on the disk, depending on its humidity, is shown in the figure.

It is known that modification of wood with ammonia significantly increases its ductility. Optimal quantity ammonia is 5%. It is proposed to use urea as a source of ammonia, which decomposes under pressing conditions:

1ЧН2 - С - 1ЧН2 + Н20 -> 2Шз + С02. ABOUT

The amount of ammonia and carbon dioxide, formed during the decomposition of urea, can be calculated using the formulas

there = tk /1.765; tug = 0.733 tk.

In our opinion, the use of urea is more advisable, since the resulting carbon dioxide creates a slightly acidic environment, which promotes the polycondensation of lignin and the easily hydrolyzed part of cellulose - hemicelluloses. This coincides with the opinion of the authors of the works.

In the process of producing wood plastic without adding a binder, water is necessary as a wood plasticizer and a chemical reagent involved in reactions with wood components.

According to , for flow chemical processes occurring during the formation of plastic from pine particles at a pressure of 2.5 MPa, the initial moisture content of the wood should be 7 ... 9%. Using hardwood(aspen, alder) the initial humidity should be slightly higher - 10 ... 12%. To give wood plasticity, the moisture content, which depends on the type of wood and pressing pressure, must be even higher.

In addition, when using urea as a modifier, additional water is required to decompose it (see diagram above). The amount of water for the reaction can be calculated using the formula TV = 0.53 there.

Consequently, during the formation of DP-BS based on ShP-F using urea as a modifier optimal content water should be about 13%.

To modify the press composition based on ShP-F, 9 wt.% was used. urea. This made it possible to significantly increase the viscous-heaping properties of the press material. For example, the Raschig fluidity, with a moisture content of the starting material of 13% wt., increased by 3.5 times, the fluidity on the disk - from 75 to 84 mm, the modulus of elasticity in bending - from 263 to 364 MPa, and the shear strength, determined according to, decreased from 2.6 to 1.5 MPa

Thus, the following conclusions can be drawn:

Using the method of mathematical planning of an experiment of the type Z2, the influence of SHP-F humidity (Х\ = 11 ± 5%) and pressing pressure (Х2 = 15 ± 10 MPa) on the properties of DP-BS (pressing temperature 170 °C) was studied;

When processing the experimental results, adequate regression equations were obtained in the form of a second-order polynomial:

¥,(ayug) = 34.9 + 6.6 X! + 16.9 X2 - 1.4 X? - 4.3 X22 - 3.0 Xx X2;

G2(D:,) = 34.5 - 21.8 X ~ 76.7 X2 + 26.3 X2 - 3.8 X22 + 75.5 X X2.

BIBLIOGRAPHY

1. Bazarnova N.G. The influence of urea on the properties of pressed materials from wood subjected to hydrothermal treatment / N.G. Bazarnova, A.I. Galochkin, V.S. Peasants // Chemistry of plant raw materials. -1997. - No. 1. -S. 17-21.

2. Buryndin V.G. Studying the possibility of using chipboard grinding dust to produce phenolic plastics / V.G. Buryndin [et al.] // Technology of wood boards and plastics: interuniversity. Sat. - Ekaterinburg, ULTI, 1994. - pp. 82-87.

3. Vigdorovich A.I. Wood composite materials in mechanical engineering (handbook) / A.I. Vigdorovich, G.V. Sagalaev, A.A. Pozdnyakov. - M.: Mechanical Engineering, 1991.- 152 p.

4. Dedyukhin V.G. Wood plastics without the addition of binders (DP-BS): collection. tr., dedicated to the 70th anniversary of the Faculty of Engineering and Ecology of the USFTU / V.G. Dedyukhin, N.M. Mukhin. - Ekaterinburg, 2000. - P. 200-205.

5. Dedyukhin V.G. Study of the fluidity of wood press mass without adding a binder / V.G. Dedyukhin, N.M. Mukhin // Technology of wood boards and plastics: interuniversity. Sat. - Ekaterinburg: UGLTA, 1999. - P. 96-101.

6. Dedyukhin V.G. Pressing facing tiles from pressing mass without adding a binder / V.G. Dedyukhin, L.V. Myasnikova, I.V. Pichugin // Technology of wood boards and plastics: interuniversity. Sat. - Ekaterinburg: UGLTA, 1997. -S. 94-97.

7. Dedyukhin V.G. Pressed fiberglass / V.G. Dedyukhin, V.P. Stav-rov. - M.: Chemistry, 1976. - 272 p.

8. Doronin Yu.G. Wood press materials / Yu.G. Doronin, S.N. Miroshnichenko, I.Ya. Shulepov. - M.: Lesn. industry, 1980.- 112 p.

9. Kononov G.V. Chemistry of wood and its main components / G.V. Kononov. - M.: MGUL, 1999. - 247 p.

10. Minin A.N. Technology of piezothermoplastics / A.N. Minin. - M.: Lesn. industry, 1965. - 296 p.

11. Otlev I.A. Handbook for the production of particle boards / I.A. Otlev [and others]. - M.: Lesn. industry, 1990. - 384 p.

12. Board materials and products made of wood and other lignified materials plant residues without adding binders /ed. V.N. Petri. - M.: Lesn. industry, 1976. - 360 p.

13. Preparation, properties and application of modified wood. - Riga: Zinatne, 1973. - 138 p.

14. Shcherbakov A.S. Technology of composite wood materials / A.S. Shcherbakov, I.A. Gamova, L.V. Melnikova. - M.: Ecology, 1992. - 192 p.

V. G. Dedyukhin, V. G. Buryndin, N.M. Mukhin, A. V. Artyomov Producing Items out of Phenoplasts by Pressing in Closed Press Molds without Adding Binding Agents

The research results of technological properties of press composition made of wood particles without adding binding agents and physical mechanical properties of plastics from these compositions are provided. The influence of low-molecular (organic and inorganic) modifiers and water in plastic formation process are studied.

Wood plastics are plasticized wood materials with improved physical and mechanical properties, obtained by combined mechanical, thermal and chemical processing of raw materials. Wood plastics are divided into:

1) pressed wood (lignostone);

2) wood-laminated plastics (lignofol, delta wood, balinite, arctilite, etc.);

3) wood-plastic masses.

Pressed wood (plasticized) - natural wood (most often birch, less often beech, hornbeam, maple, etc.), compacted at a pressure of 15-30 Mn/m2 (150-300 kgf/cm2) and temperature up to 120°C. Compaction is carried out different ways: pressing the workpiece into a mold of smaller diameter, compressing the workpiece between plates of a hydraulic press or in a removable mold, pressing pre-bent wood plates. To increase the moisture resistance and shape stability of wood plastics, wood blanks are impregnated with synthetic resins before compaction. It is possible to obtain moisture-resistant pressed wood without impregnation with synthetic resins by intensifying the heat treatment of the workpiece at the plasticization stage; in this case, resin-like products of the alteration of lignin and hemicelluloses are formed in the wood.

Pressed wood is produced in the form of boards, bars, slabs, bushings, etc. This wood has high impact strength, ductility, a low coefficient of friction and increased moisture resistance. Pressed wood is used for the manufacture of machine parts operating under shock loads, as well as anti-friction parts.

Wood-laminated plastics are materials based on thin wood sheets (veneer) of hardwood. To obtain these plastics, birch (less often beech or linden) veneer is impregnated (sometimes coated) with solutions of thermosetting synthetic resins, dried, collected in bags and pressed on floors. hydraulic presses with heating at a pressure of 10-17.5 MN/m2 (100-175 kgf/cm2) and a temperature of 120-150°C. To increase the strength and elasticity of these plastics, they are reinforced metal mesh, foil, rubberized fabric, etc. Additives of graphite and oil improve the anti-friction properties of plastics. Wood-laminated plastic blanks are processed into products by mechanical processing (sawing, planing, etc.). These plastics have good mechanical, including anti-friction, and electrical insulating properties, and are resistant to many chemicals.

Wood laminates are used as construction material in mechanical engineering and shipbuilding, as an electrical insulating and structural material for the production of equipment parts high voltage. They are suitable for the manufacture of bending dies, mandrels, and, provided they are lubricated with water and at a friction temperature not exceeding 60°C, heavily loaded bearings.

Wood-plastic masses are solidly pressed profile products or tile materials made in molds by hot pressing of crushed wood (sawdust, shavings, fibers, veneer scraps), impregnated with solutions of synthetic resins and dried. In some cases, the wood is preliminarily subjected to partial hydrolysis with acid or steaming under pressure, or treatment with alkali. Wood-plastic masses have a high mechanical strength, antifriction and electrical insulating properties. These materials are used in the production of profile solid-pressed products (liners and bushings for bearings, gears, cable joints, electrical insulating parts, caps distillation columns etc.), as well as parquet tiles, etc.

Genel S.V., Wood plastics in technology, M., 1959;

Pressed wood and wood plastics in mechanical engineering. Handbook, ed. A. G. Rakina, M.-L., 1965.

Ecology of consumption. Science and technology: People have learned to transform processing waste natural materials into products that are superior to these materials in properties. From the article you will learn about a completely new material - wood-polymer composite or WPC.

The last 40 years of industrial development can easily be called the “era of combined materials.” Modern equipment and technologies make it possible to combine seemingly incompatible things: wood, concrete, plastic, paper, metal. They all mix, diffuse, fuse with one goal - to obtain New Product, combining the best properties of several starting materials. So, among other new products we saw “liquid wood”.

What is “liquid tree”

In technical terms, it is an extruded wood-polymer composite (WPC). This means that the wood component is preserved using plastic. In this combination, the material takes on the best properties:

1. From wood - compressive strength, impact resistance, elasticity. At the same time, the wood component is practically free - any waste ground into flour is used.
2. From plastic - corrosion resistance, flexibility, precision processing. The polymer envelops wood particles and eliminates the main disadvantage of wood - destructive reactions with water. The polymer in this technology is 90% recycled plastic, i.e. recycled waste.

Technological process easy to understand, but quite difficult to execute. The polymer (plastic) is mixed in a certain proportion with wood flour and heated so that it melts. Then it is molded in an extruder, on rollers or in molds and cooled. At different stages, about 10 different additives are mixed into the mass - plasticizers, catalysts, hardeners and others. All manufacturing details - type of wood and brand of plastic, mixture proportions, additives, temperature conditions, as a rule, constitute a trade secret. It is known that all ingredients can be purchased freely, and for wood flour they mainly choose bamboo, larch and other durable species of the middle price category.

For the manufacture of WPC, special multi-stage production lines are created. They consist of many devices and controllers. Unfortunately, it will not be possible to assemble such a machine with your own hands in the garage. But you can purchase a ready-made production line.

WPC products

Currently, the product range is incomplete, since the material is relatively new and its properties have not been fully studied. However, several of the most popular positions can be mentioned now.

Terrace board or decking

It accounts for up to 70% of all demanded WPC products today. Most of the supplied production lines are focused on the production of just such a board, since this is the only one available this moment alternative to wood. The board consists of a perimeter frame, internal stiffening ribs and has a tongue-and-groove fastening system. Various colors available.

Advantages over traditional material: WPC boards are distinguished from wood by continuous painting and better physical characteristics (strength, flexibility, processing accuracy). Many types of WPC boards are produced double-sided - with solid wood reliefs and ribbed cutting.

WPC terrace board on video

Facade facing panels or planken

By by and large, they can be compared with vinyl siding - the installation principle and panel structure are very similar. But the WPC panel is much thicker and stiffer, and accordingly has greater weight and better physical properties.

Advantages over traditional material: a stronger and more durable facade, cavities in the panels and thick walls retain heat better and absorb noise.

Fences, railings, railings, balustrades

Small architecture forms made from “liquid wood” for decorative finishing exterior and landscape. have good bearing capacity and are suitable for intensive use (in crowded places).

It was customary to make such products from wood (short-lived and requiring maintenance) or concrete (heavy, cold and not always reliable). Wood-composite forms are made prefabricated, and all parts are designed in advance. All that remains to do on site is to assemble them using a grinder and a screwdriver. Such a fence does not require a strong foundation or constant painting. If a section or structural element is damaged, it can be easily replaced by making an additional required quantity details.

The general advantage is absolute insensitivity to atmospheric wear (moisture, frost, overheating in the sun), insects, fungi and abrasion.

A common disadvantage is the relatively large fluctuations during heating and cooling. The expansion of WPC terrace boards can be up to 6 mm per 1 m (with gradual heating to +40 ° C).

Prices for facade panels made of “liquid wood”

Name	Manufacturer	Characteristics	Price 1 m 2, cu. e.
Duo Fuse FPS-22	Belgium	2800x220x22 mm, PVC	35
"MultiPlast"	Russia	3000x166x18 mm, PE	20
RINDEK	Russia	3400x190x28 mm, PVC	22
MultiDeck Chalet	China	2900x185x18 mm, PE	17
C.M. Cladding	Sweden	2200x150x11 mm, PVC	28
ITP (Intechplast)	Russia	3000x250x22 mm, PVC	26
DORTMAX	Russia	4000x142x16 mm, PE	18

How to choose a WPC decking board

Any type of “liquid wood” is made from wood flour, the composition of which is not so important. But the composition of the polymer that is added to it can be critical:

1. Polyethylene based polymer. Easier and cheaper to produce. Contains a larger amount of sawdust, due to which it is cheaper than analogues. Susceptible to UV radiation (without additives).
2. PVC based polymer. More resistant to temperature changes, ultraviolet radiation, greater fire safety. 2 times more durable compared to other compounds.

Based on the type of profile, terrace boards are divided into two types:

1. Full-bodied. Withstands significant shock loads. Well suited for places with high traffic - summer cafes and verandas, ship decks, embankments and piers.
2. Hollow. They are light in weight. Suitable for terraces of private houses.

Based on the type of connection, WPC boards are divided into:

1. Suture. They are mounted with a gap of 3–5 mm and provide good water drainage. Fastened with metal or plastic clamps.
2. Seamless. They create a continuous, durable surface due to mutual adhesion. Fastened with self-tapping screws, no clamps required. Suitable for summer areas of cafes - small things, heels, etc. do not get into the gaps.

By type of anti-slip coating or treatment:

1. Treated with brushes (“brushing” from the English brush - brush, brush). Surface created with a metal brush (artificial aging).
2. Polished. The surface is treated with emery cloth.
3. Embossed. As a rule, they are executed in a wood structure. It has a good decorative appearance, but in high-traffic areas the design wears away and this becomes noticeable.
4. Co-extrusion. The top layer is made of a high-strength composition and is structured during the extrusion of the board itself.
5. Co-extrusion with deep embossing (from the English embossing - embossing). Embossing on the top layer imitates valuable species tree.

What to pay attention to, regardless of the type of board you choose:

1. Height of ribs. The strength of the board depends on it.
2. Number of stiffeners. Affects bending strength - the more there are, the higher the strength.
3. Wall thickness. Thin walls (2–3 mm) do not withstand shock loads well.
4. Board width. The wider the board or panel, the faster and easier installation and less fastenings are required.

Video - how to choose WPC decking board

It is absolutely fair to take these tips in relation to façade panels and other WPC products for surface cladding.

The industry provides the average person with the opportunity to make their choice - to use a new natural material that is used Natural resources(wood, stone) or use recycled products. Today people have learned to transform waste from processing natural materials into products that have superior properties to these materials. However, the choice remains with the person - either to dispose of waste by purchasing WPC, or to create more and more of it, giving preference to natural materials. published

22.05.2015

Plastics from pressed wood (WMP) are produced by piezothermal processing in molds that provide parts of the required configuration.
Materials. For the production of wood press mixtures of various types, piece veneer with a thickness of 0.5-1.8 mm, humidity up to 12%, wood laminated plastic waste, wood processing waste - shavings and sawdust - are used. Wood waste should not contain bark and rot, and chipboard waste should be cut into pieces up to 120 mm long so that they can be loaded into a crusher.
Bakelite varnishes SBS-1 and LBS-3, phenol-formaldehyde resin SFZh-3011 and phenol alcohols B and V are used as binders in the manufacture of press mixtures. The concentration of bakelite varnish before impregnation should be 43-45%, and phenol-formaldehyde resin 28-35%. Mineral oil, oleic acid, dyes, aluminum powder, silver graphite, copper powder, etc. are used as additives that improve the properties of MDP products.
Technological process of MDP production. The technological process for the production of MDP consists of the following operations: preparing conditioned wood particles, preparing a working solution of the binder, dosing and mixing wood particles with the binder and modifier, and drying the mass.
Features of the technological process for the production of MDP are associated with the type of wood waste used; when making press mass from sawdust (Fig. 106, a), they are sifted on a vibrating sieve with cells measuring 10x10 mm for the coarse fraction and 2x2 mm for the fine fraction. Standard particles enter the dryer, where they are dried at 80-90 ° C to a moisture content of 3-8%. Drum, belt and air fountain dryers are used for drying.
When using piece veneer and chipboard waste as raw materials, the technological process includes the operation of grinding wood in crushers (Fig. 106, b). Hammer crushers, for example DKU-M, are used to grind veneer. The veneer is crushed using knives and hammers mounted on the machine rotor. As the particles are crushed to the desired fraction, they are ejected through a replaceable sieve and removed by pneumatic transport into a hopper. As a result, needle-shaped wood particles 5-60 mm long, 0.5-5 mm wide, and 0.3-2 mm thick are formed. To grind chipboard waste, a hammer crusher S-218 is used, which crushes and sorts wood particles. The length of the particles after crushing is 12-36 mm, width 2-7 mm, thickness 0.5-1.2 mm. Particle sizes depend on the purpose of the MDP.
Wood particles with a binder are mixed in worm-blade mixers, and sawdust is mixed in runner mixers. Rollers of runners, when moving over a layer of sawdust, crush them into fibers, which further ensures increased physical and mechanical properties of MDP products. Wood particles and binder are dosed by weight. They are mixed by feeding wood particles in portions of 80-100 kg. The temperature of the impregnating solution, depending on its viscosity, is 20-45 °C. The duration of mixing in worm mixers depends on the type of particles. Sawdust, shavings and veneer particles are mixed for 10-30 minutes, and chipboard particles - 15-20 minutes. The amount of dry resin in MDP should be 25-30% and 12-15%, respectively). The mixing time in running mixers is 30-40 minutes, and the dry resin content in the press mixture is 25-35%.
Modifiers are supplied to the mixers after loading the impregnating solution in the following quantities, %: oleic acid 0.8-1.5, methenamine 1-3, dyes 2-5, graphite 2.5-10, aluminum powder or copper powder 1.5- 3, mineral oil 10-20.
Drying of the press mass is carried out at 40-50 °C for 30-60 minutes to a humidity of 5-7%. For this, the same units are used as for drying raw wood particles.
Technological process for the production of products from MDP. For the manufacture of products, MDP can be used in the form of a loose mass or in the form of a briquette obtained as a result of its preliminary compaction. The use of briquettes allows you to dose MDP more accurately, reduce the volume of the loading chamber of the mold by 2-3 times, and speed up the preheating process. Briquettes of a shape corresponding to the shape of the product (cylinders, parallelepipeds, etc.) are produced in special briquetting presses or molds. Briquetting is carried out under a pressure of 20 MPa. At temperatures up to 25 °C, the duration of holding under pressure is 1 minute, at 50-60 °C - 0.5 minutes.
To shorten the pressing cycle of products made from MDF, it is preheated. At 60-70 °C, heating takes 30-60 minutes, and at 140 °C - up to 5 minutes. The most uniform heating is achieved in the HDTV field. Convective, induction and other types of heating are also used.
MDP products are made by hot pressing in hydraulic presses in closed steel molds. Pressing is carried out by direct and injection methods (Fig. 107). In direct pressing, pressure acts directly on the mass located in the mold cavity. During injection molding, MDP flows under pressure from the loading cavity into the mold; direct pressing is used in the manufacture of simple and large-sized products. The injection molding method produces products with thin walls and complex configurations. During the pressing process, MDP is heated, softened, compacted, spreading into the cavity of the mold, and cured.

The pressure when pressing MDF, which has low fluidity, depends on the configuration of the parts and the pressing method. When directly pressing parts with a straight contour, it is 40-50 MPa. When injection molding parts with a shaped contour, during the process of pressing the press mixture into the mold, the pressure is 80-100 MPa, during pressing - 40-50 MPa.
The temperature of the mold during direct pressing is 145 ± 5 °C. The duration of pressing depends on the thickness of the walls of the product. For products with a wall thickness of up to 10 mm, when heating the matrix and punch, it is equal to 1 min/mm, when heating only the matrix - 1.5-2 min/mm, for products with a wall thickness of more than 10 mm - 0.5 and 1 min, respectively. /mm.
during injection molding, MDP is first compacted at a mold temperature of 120-125 ° C for 1-2 minutes. The mass is pressed into the mold at the same temperature. The end of this pressing period is determined by the moment the pressure begins to drop. Pressing is carried out at 145-165 °C for 4 minutes. After finishing the pressing, the products are cooled.
Products with a large contact surface with the mold are cooled together with it to 40-60 °C. Thin-walled products are cooled in a clamped state in special devices under pressure 0.2-0.3 MPa. Parts of simple configurations and parts whose dimensions do not have high requirements are cooled in a free state.
Mechanical processing of MDP products consists mainly of removing flash and sprues. Additional mechanical processing to change the shape and size of parts is carried out on metal-cutting machines.
The production of 1 ton of MDP consumes: dry wood 1.8-2 m3, resin 600 kg, ethyl alcohol 340 l, steam 2 tons, electricity 70 kWh.

480 rub. | 150 UAH | $7.5 ", MOUSEOFF, FGCOLOR, "#FFFFCC",BGCOLOR, "#393939");" onMouseOut="return nd();"> Dissertation - 480 RUR, delivery 10 minutes, around the clock, seven days a week and holidays

Savinovskikh Andrey Viktorovich. Obtaining plastics from wood and plant waste in closed molds: dissertation... Candidate of Technical Sciences: 05.21.03 / Savinovskikh Andrey Viktorovich; [Place of defense: Ural State Forestry University]. - Ekaterinburg, 2016. - 107 p.

Introduction

CHAPTER 1. Analytical review 6

1.1 Wood composite materials with synthetic binders 6

1.2 Lignocarbohydrate and piezothermoplastics 11

1.3 Methods for modifying wood particles 14

1.4 Lignin and lignocarbohydrate complex 19

1.5 Cavitation. Cavitation processing of plant raw materials 27

1.6 Bioactivation of wood and plant particles with enzymes.. 33

1.7 Selection and justification of the direction of research 35

CHAPTER 2. Methodological part 36

2.1 Characteristics of starting substances 36

2.2 Measurement techniques 41

2.3 Preparation of bioactivated press raw materials 41

2.4 Production of DP-BS 41 samples

2.5 Preparation of a sample of press raw materials for plastic 42

CHAPTER 3. Obtaining and studying the properties of wood plastics without a binder using modifiers 43

CHAPTER 4. The influence of chemical modification of wheat husk on the properties of RP-BS 57

CHAPTER 5. Preparation and study of the properties of wood plastics without a binder using bioactivated press raw materials 73

CHAPTER 6. Technology for obtaining DP-BS 89

6.1 Calculation of extruder performance 89

6.2 Description of the production process 93

6.3 Estimation of the cost of finished products 95

Conclusion 97

Bibliography

Introduction to the work

Relevance of the research topic. The volume of production of processed wood and plant raw materials is constantly increasing. At the same time, the amount of various waste from wood processing (sawdust, shavings, lignin) and agricultural plants (straw and cereal seed shells) also increases.

In many countries, there is production of wood composite materials using synthetic thermosetting and thermoplastic organic and mineral binders as a polymer matrix, and crushed plant waste as fillers.

It is known that it is possible to produce wood composite materials by flat hot pressing from wood processing waste without the addition of synthetic binders, which are called piezothermoplastics (PTP), lignocarbohydrate wood plastics (LUDP). It is noted that the initial press compositions have low plastic-viscosity properties, and the resulting composites have low physical and mechanical properties, especially water resistance. And this requires finding new ways to activate the lignin-carbohydrate complex.

Thus, work aimed at using wood and plant waste without the use of synthetic binders to create products is relevant.

The work was carried out on the instructions of the Ministry of Education and Science of the Russian Federation, project No. 2830 “Obtaining wood plastics from wood and agricultural plant biomass waste” for 2013-2016.

The purpose and objectives of the work. The goal of the work is to obtain plastics from wood (DP-BS) and agricultural waste (RP-BS) without adding synthetic binders with high performance properties.

To achieve this goal, it is necessary to solve the following tasks:

To study the process of formation of DP-BS and RP-BS based on wood (pine sawdust) and plant (wheat husk) waste.

To study the influence of chemical modifiers, as well as technological parameters (temperature, humidity) on the physical and mechanical properties of DP-BS and RP-BS.

Determine rational conditions for obtaining DP-BS and RP-BS from wood and plant waste.

To establish the effect of bioactivation of press raw materials with activated sludge on the physical

co-mechanical properties of DP-BS.

The degree of development of the research topic. Analysis of scientific, technical and patent literature has shown a very low degree of development of issues related to the patterns of formation of the structure and properties of wood plastic without a synthetic binder.

Scientific novelty

The kinetic laws of the process of formation of DP-BS and RP-BS (activation energy, pre-exponential factor, reaction order) were established using the DSC method.

The influence of chemical modifiers (hydrogen peroxide, urotropine, isomethyltetrahydrophthalic anhydride, cavitation lignin, hydrolytic lignin) on the rate of formation of DP-BS and RP-BS has been established.

The kinetic patterns for the production of DP-BS using bioactivated wood waste were obtained.

Theoretical significance The work is to establish the patterns of influence of a number of modifiers and the humidity of press raw materials from wood and agricultural waste on the physical and mechanical properties of DP-BS and RP-BS.

Practical significance The work consists of using waste renewable raw materials and experimentally proving the possibility of obtaining DP-BS and RP-BS with improved physical and mechanical properties. A recipe for producing DP-BS and RP-BS has been proposed. Products made from DP-BS have low formaldehyde emissions.

Methodology and research methods. The work used traditional scientific research methodology and modern research methods (differential scanning calorimetry, Fourier transform infrared spectroscopy, 1H PMR).

Submitted for defense

Results of a study of the thermokinetics of the formation of DP-BS, RP-BS and the influence of modifiers and humidity on this process.

Patterns of formation of the properties of DP-BS and RP-BS in closed molds under the influence of temperature, humidity of press raw materials and its chemical modification.

Degree of reliability of research results is ensured by repeated repetition of experiments and the use of methods for statistical processing of the obtained measurement results.

Approbation of work. The results of the work were reported and discussed at the VIII International Scientific and Technical Conference “Scientific Creativity of Youth for the Forestry Complex” (Ekaterinburg, 2012), IX International Scientific and Technical Conference “Scientific Creativity of Youth for the Forestry Complex” (Ekaterinburg, 2013), International Conference “Compositional materials based on wood and other fillers" (Mytishchi, 2014).

Publications. Based on the dissertation materials, 12 articles were published, including 4 articles in publications recommended by the Higher Attestation Commission.

Workload

The dissertation is presented on 107 pages of typewritten text, contains 40 tables and 51 figures. The work consists of an introduction, 6 chapters, a conclusion, and a list of references, including 91 references to domestic and foreign works.

Lignocarbohydrate and piezothermoplastics

Lignocarbohydrate and piezothermoplastics. These materials are made from sawdust or other plant raw materials by high-temperature processing of the press mass without the introduction of special synthetic binders. The technological process for the production of lignocarbohydrate wood plastics consists of the following operations: preparation, drying and dosing of wood particles; carpet formation, cold pressing, hot pressing and cooling without releasing pressure. When preparing the press mass, wood particles are sorted, then the fraction with a particle size of more than 0.5 mm is further crushed, the quality sawdust goes into the dryer, and then into the spreading machine. The carpet is formed on pallets coated with a layer of talc or anti-adhesive liquid. First, the finished carpet is fed into a press for cold pressing, which lasts for 1.5 minutes at a pressure of 1-1.5 MPa, after which it is sent for hot pressing at a pressure of 1.5-5 MPa and a temperature of 160-180 C. Pressing the boards 10 mm thick lasts 40 minutes.

Under the influence of temperature, partial hydrolysis of wood polysaccharides and the formation of organic acids occur, which are catalysts that contribute to the destruction of the lignocarbohydrate complex. The resulting chemically active products (lignin and carbohydrates) interact with each other during pressing. The result is a denser and stronger material than wood.

Raw materials for the production of lignocarbohydrate wood plastic are obtained by processing coniferous and deciduous wood. Along with sawdust, machine shavings, crushed wood, bark mixed with wood, crushed logging waste and some lignified agricultural waste can be used to produce plastic. Impurities in the raw materials of partially rotten wood improve the physical and mechanical properties of lignocarbohydrate plastics.

Compared to particle boards, lignocarbohydrate plastics have a number of advantages: they are not subject to aging due to the destruction of the organic binder and their strength indicators do not decrease over time; There are no toxic emissions during operation environment. Significant disadvantages of the production of lignocarbohydrate plastics are the need for powerful pressing equipment and the duration of the pressing cycle.

It is noted that under the influence of pressure and temperature, crushed plant materials acquire the ability to form a durable and hard material of a dark color that can be molded. This material is called piezothermoplastic (PTP).

The starting raw materials, along with sawdust, can be crushed coniferous and deciduous wood, flax and hemp fire, reeds, hydrolyzed lignin, and odubin.

There are several methods for obtaining PTP, which have been thoroughly studied and introduced into production, but have not found further application due to high energy costs: 1) a one-stage method for obtaining PTP (A.N. Minin. Belarusian Institute of Technology); 2) a two-stage method for producing plastics from hydrolyzed sawdust (N.Ya. Solechnik, Leningrad LTA); 3) technology for the production of lignocarbohydrate wood plastics (LUDP) (VN. Petri, Ural LTI); 4) steam explosion technology (J.A. Gravitis, Institute of Wood Chemistry, Latvian Academy of Sciences). Piezothermoplastics are divided into insulating, semi-solid, hard and super-hard.

With an average density of 700-1100 kg/m3, piezothermal plastics made from birch sawdust have a static bending strength of 8-11 MPa. When the average density increases to 1350-1430 kg/m3, the tensile strength during static bending reaches 25-40 MPa.

The high physical and mechanical properties of piezothermoplastics allow them to be used for the manufacture of floors, doors, and also as finishing material. A type of wood plastic is vibrolite, technological features which consists of partially grinding sawdust and small shavings on a vibrating mill, mixing the finely ground mass with water and then obtaining sludge. From a mixture of sludge with particles 0.5-2 mm in size, a carpet is formed in a casting machine, which is dewatered by a vacuum pump. The resulting press mass is supplied for cold and hot pressing. The finished slabs are transported to a hardening chamber, where they are subjected to heat treatment for 3-5 hours at a temperature of 120-160 C, as a result of which their water absorption is reduced by almost 3 times and swelling by more than 2 times.

Vibrolite is used for laying subfloors, installing partitions, cladding wall panels in public buildings, manufacturing of built-in furniture and panel doors.

Since the 30s in the USSR, many researchers have been involved in the production of slab materials by piezothermal processing of plant raw materials without the use of traditional binders. The work was carried out in the following directions: 1) pressing natural, untreated sawdust; 2) pressing of sawdust pre-autoclaved with water steam (pre-hydrolysis) or steam with a catalyst (mineral acid); 3) pressing of sawdust pre-treated with chemical reagents: a) gelatinization of the press mass (chlorine, ammonia, sulfuric acid and other substances) for its partial hydrolysis and enrichment with substances with binding properties; b) chemical polycondensation of the press mass with the participation of others chemical substances(furfural, phenol, formaldehyde, acetone, alkaline and hydrolytic lignins, etc.).

Preparation of bioactivated press raw materials

The endothermic minimum corresponds to the process of hydrolysis of lignin - a carbohydrate complex and the easily hydrolyzed part of cellulose (polysaccharides).

The exothermic maximum corresponds to polycondensation processes, which determine the process of formation of DP-BS. Since the process is catalyzed by acids that are formed during the pyrolysis of wood, as well as due to the presence of resin acids contained in extractive substances, this is an n-order reaction with autocatalysis.

For wood waste with modifying additives (hydrogen peroxide, urotropine, IMTHF), the peak maxima on the DSC curves shift to the left, which indicates that these compounds act as catalysts for the above processes (T1 100-120 0C, T2 180-220 0C), accelerating the process of hydrolysis of wood polysaccharides, as well as the lignin-carbohydrate complex.

From Table 3.2 it is clear that at the first stage, with increasing humidity of the press raw material, the effective activation energy increases (from 66.7 to 147.3 kJ/mol), which indicates a greater degree of hydrolytic destruction of wood. The use of modifiers leads to a decrease in the effective activation energy, which indicates their catalytic effect.

The values ​​of the effective activation energy at the second stage of the process for modified press raw materials change slightly with increasing humidity.

The use of modifiers leads to a decrease in the effective activation energy at the second stage of the process. Analysis of kinetic equations showed that the best model at the first stage of the process it is an n-order reaction, at the second stage it is an n-order reaction with auto-acceleration: A 1 B 2 C.

Using the kinetic parameters of the process, t50 and t90 (the time required to achieve a conversion degree of 50 and 90%) were calculated for unmodified and modified press raw materials (Table 3.3), and conversion curves were also presented (Fig. 3.4-3.6) .

Dependence of the degree of conversion on time at different temperatures (pine, initial humidity of press raw materials - 8%) Figure 3.5 - Dependence of the degree of conversion on time at different temperatures (pine, modifier - urotropine, initial humidity of press raw materials - 12%)

Dependence of the degree of conversion on time at different temperatures (pine, modifier - hydrogen peroxide, initial humidity of press raw materials - 12%) Table 3.3 - Time values ​​​​for reaching the degree of conversion of 50% and 90% at different temperatures No. Degree of conversion Press raw materials with a humidity of 8% Press raw materials with a moisture content of 12% (modifier - 1.8% H2O2, %) Press raw materials with a moisture content of 12% (modifier - 4% C6H12N4, %)

The use of hydrogen peroxide speeds up the process at the first stage by more than 4 times than when modifying press raw materials with hexamine. A similar pattern is observed at the second stage of the process. Based on the total time of formation of DP-BS, the activity of the press raw materials can be arranged in the following row: (unmodified press raw materials) (press raw materials modified with urotropine) (press raw materials modified with hydrogen peroxide). In order to establish the influence of humidity and the content of the amount of modifier in the press raw materials on the operational properties of DP-BS, mathematical planning of the experiment was carried out. A preliminary study was carried out on the influence of the humidity of the initial press raw materials on the physical and mechanical properties of DP-BS. The results are shown in table. 3.4. It has been established that the higher the initial moisture content of the press raw materials, the lower the physical and mechanical properties, such as bending strength, hardness, and bending modulus of elasticity. In our opinion, this is due to a greater degree of thermohydrolytic destruction of the lignocarbohydrate complex. Table 3.4 - Physical and mechanical properties of DP-BS obtained at different humidity levels of the press material

Thus, the physical and mechanical properties of DP-BS depend on the formulation and conditions of its preparation. So, for plastic with high physical and mechanical properties, the following composition should be used: lignin content 3%, IMTHF content 4%, initial moisture content of press raw materials 6% and hot pressing temperature 1800C. For plastic with low values ​​of water absorption and swelling, it is necessary to use the following composition: lignin content 68%, IMTHFA content 2%, initial moisture content of press raw materials 17% and hot pressing temperature 195 C0.

The influence of chemical modification of wheat husk on the properties of RP-BS

The depth of thermohydrolytic destruction of lignin in wood and plant materials depends on the type of chemical modifier used.

Our studies of the formal kinetics of plastic production show that lignin from coniferous species (pine) has greater reactivity than lignin from annual plants (wheat husks). These results are consistent with the oxidation results of model lignin compounds from softwood, hardwood, and plant-derived lignin. An analysis of the literature showed that theoretical studies of the characteristics of wood transformation under enzymatic influences made it possible to develop the biotechnology of wood plastics based on the partial biodegradation of the lignocarbohydrate complex.

It is known that biotransformed wood particles significantly change their plasticity. Also, the species composition of wood raw materials has significant influence on the physical and mechanical properties of plastic.

Bioactivated treatment of wood waste with various types of ligno-degrading fungi, bacteria, and in our case activated sludge, is promising for the production of press raw materials for DP-BS(Au).

Initially, the laws of the process of obtaining DP-BS(Au) based on wood waste were studied using activated sludge(Figure 5.1) with different periods of bioactivation. 0.5 7 days 14 days

A study of the formation process of DP-BS(Au) by the DSC method showed that there are two exothermic maxima on the w = f(T) curves (Fig. 5.2). This indicates that the process can be represented as two parallel reactions, corresponding to bioactivated and non-activated press raw materials, i.e. A 1 B and C 2 D. In this case, reactions 1 and 2 are n-order reactions).

The kinetic parameters of the formation process of DP-BS(Au) were determined. The results are shown in table. 5.1. Table 5.1 - Kinetic parameters of the formation process of DP-BS(Au)

At the second stage of the process of obtaining DP-BS(Au), the values ​​of the effective activation energy are of the same order as for wood press raw materials (see Chapter 3). This indicates that this exothermic peak corresponds to non-bioactivated wood pulp. Using the kinetic parameters of the process, t50 and t90 (the time required to achieve the degree of conversion of 50 and 90%) of the modified press raw materials were calculated (Fig. 5.3, 5.4).

Figure 5.3 - Values ​​for the conversion time of DP-BS(Au) at different temperatures (bioactivation time 7 days) Figure 5.4 - Values ​​for the transformation time of DP-BS(Au) at different temperatures (bioactivation time 14 days)

In order to establish the influence of activated sludge and cavitation lignin on the physical and mechanical properties of DP-BS(Au), an experiment planning matrix was compiled based on regression fractional mathematical planning of type 25-1 (see Table 5.2).

The following independent factors were used: Z 1 – content of cavitation lignin, %, Z 2 – hot pressing temperature, C, Z 3 – activated sludge consumption, %, Z 4 – duration of exposure (bioactivation), days; Z 5 – initial humidity of press raw materials, %.

The following output parameters were taken: density (P, kg/m3), bending strength (P, MPa), hardness (T, MPa), water absorption (B), swelling (L, %), flexural modulus of elasticity (Ei, MPa ), impact strength (A, kJ/m2).

According to the experimental plan, samples in the form of disks were made and their physical and mechanical properties were determined. The experimental data were processed and a regression equation was obtained in the form of a linear, polynomial of 1st and 2nd degree with an assessment of the significance of the factors and the adequacy of the equations, which are presented in Tables 5.2-5.4. Table 5.2 - Planning matrix and experimental results (three-level five-factor mathematical plan) a) hot pressing temperature and cavitation lignin content; b) consumption of sludge mixture and pressing temperature; c) humidity of press raw materials and duration of bioactivation; d) duration of bioactivation and content of cavitation lignin.

It has been established that the density of DP-BS(Au) with an increase in the content of cavitation lignin in the press raw material is extreme: the minimum density of 1250 kg/m3 is achieved with a CL content of 42%. The dependence of the density of DP-BS(Au) on the duration of bioactivation of press raw materials is also extreme and the maximum value is achieved at 14 days of bioactivation (Figure 5.5c).

Estimation of the cost of finished products

Conducted studies on the production of DP-BS, DP-BS(Au) and RP-BS (see Chapters 3,4,5) show that the physical and mechanical properties of plastic depend on the formulation of press raw materials, the type of chemical modifier and the conditions of its production .

In table Table 6.1 shows the physical and mechanical properties of plastics (DP-BS, DP-BS(Au) and RP-BS) obtained under rational conditions.

From the analysis of the results obtained (Table 6.1) it is clear that for the manufacture of products with high physical and mechanical properties, a press composition of the following composition is recommended: wood waste(pine sawdust), modifier - hydrogen peroxide (consumption - 1.8%), initial humidity - 12%.

To increase productivity, an extrusion method is proposed, which allows the production of molded products.

The dissertation examines the production of plinths. To comply with the conditions determined during hot pressing in closed molds, the extrusion head consists of two parts (a heated part of the head and the second - without heating). In this case, the residence time of the press composition in the heated part of the extrusion head is 10 minutes.

To determine the annual production volume, the extruder productivity was calculated.

For a single-screw extruder with variable (decreasing) depth cutting of a spiral channel, the volumetric productivity (Q, cm3/min) can be calculated as follows:

Here A1, B1, C1 are direct and two constants, respectively. reverse flows with variable screw cutting depth, cm3; Table 6.1 – Physical and mechanical properties of DP-BS, DP-BS(Au) and RP-BS (summary table) No. item 1245 6 Indicator Humidity of press raw materials,% Modifier DP-BS(Au) DP-BS RP-BS 12 % (4%-C6H12N4) 12% (1.8%-H202) CL - 3% Consumption AI-37% Humidity - 10% GL - 3% IMTHFA-4% Humidity - 6% GL - 68% IMTHFFA-2, 5% Humidity - 17.9% Humidity - 12% GL - 3% Hydrogen Peroxide - 0.06% Humidity - 12% GL - 35% Hydrogen Peroxide - 5% Humidity - 12%

Bending strength, MPa 8 12.8 10.3 9.6 12.0 - 8 9.7 Hardness, MPa 29 29.9 27.7 59 69 20 19 34 Flexural modulus of elasticity, MPa 1038 2909.9 1038, 6 732.6 2154 1402 1526 1915 Water absorption, % 59.1 148 121.7 43 59 34 143 139 Swelling, % 6.0 12 8 3 5.0 1.0 7 7.0 1 K – coefficient geometric shape heads, K=0.00165 cm3; n – screw rotation speed, n=40 rpm. where t is the cutting pitch, cm, assumed to be t = 0.8D; - number of auger cutting passes, =1; e – width of the auger ridge, cm; e = 0.08D; - coefficient geometric parameters auger:

Coefficients a, b depend on the geometric dimensions of the screw. They are easy to calculate if you have a drawing of the auger, from which the following values ​​are taken: h1 – depth of the spiral channel at the beginning of the feeding zone, cm; h2 – depth of the spiral channel at the beginning of the compression zone, cm; h3 – depth of the spiral channel in the dosing zone, cm; If the screw dimensions are unknown (with the exception of D and L, which are known from the extruder brand), then take h1 = 0.13D. After this, the remaining parameters are calculated: where L is the length of the screw, cm; L0 – length of the screw to the compression zone, cm; where Lн is the length of the pressure part of the auger, cm; Ln=0.5L. where i is the degree of compression of the material; i=2.1. The obtained calculation results using the above formulas make it possible to calculate some other parameters of the screw.

Wood waste is sorted on vibrating screens (item 1) from large particles, then the wood particles pass through a metal detector (item 3). The coarse fraction enters the hammer crusher (item 2) and then returns to the vibrating sieve (item 1). From the vibrating sieve, small particles are fed by pneumatic transport into a cyclone (item 4), and then into a hopper (item 5), from where they are fed into a drum-type dryer (item 6) using a portioned screw conveyor, and the wood particles are dried to a moisture content of 6%. Shredded wood waste enters the cyclone (item 7), then into the dry crushed waste hopper (item 8) with a screw conveyor, through which it is fed to a belt scale (item 9).

The hydrogen peroxide solution is prepared in a tank (item 10) for mixing with water. Hydrogen peroxide is dosed using a scale (item 11). The supply of the required amount of water is regulated by a flow meter. The hydrogen peroxide concentration should be 1.8%. Belt scales feed required amount crushed wood particles into a continuous mixer (item 12), which also receives a certain amount of modifier solution. The components are thoroughly mixed in the mixer; the moisture content of the press raw materials should be 12%.

Then the press raw materials enter the distribution funnel (pos. 13), from where they enter the hopper (pos. 14) of the finished press raw materials. The bunker is the main buffer warehouse for ensuring uninterrupted operation installations. The hopper (pos. 14) is equipped with a screw dispenser (pos. 15), with the help of which the finished composition is loaded into the hopper of the extrusion plant (pos. 16), with the help of which finished composition fed into the extrusion head.

The channel of the extrusion installation (item 17) is heated to a temperature of 1800C, the residence time in the heated part is 10 minutes, in the unheated part it is also 10 minutes.

The pressed product (item 18) is sent to the stage of trimming, culling and sorting, then enters the stage machining. After the control stage, finished goods sent to the finished goods warehouse. Figure 6.1 Technology system production of a product in the form of a DP-BS plinth from woodworking waste without adding binders using the extrusion method

Table 6.2 shows the calculation of the annual requirement for raw materials for the production of skirting boards. The estimated annual productivity of the production line for this type of product is 1 ton. Table 6.3 – Calculation of the need for raw materials and supplies Type of raw materials Consumption rate (1 t), Cost of 1 kg of raw materials, rub. Amount of costs for 1 ton of products, thousand rubles. Pine sawdust 0.945 8 7.56 Process water 0.048 7 0.33 Hydrogen peroxide 0.007 80 0.56 Total: 8.45 The amount of costs for the purchase of raw materials per ton of finished production products will be 8.456 thousand rubles. Compared to the production of this type of product from DPKT, which amounted to 47.65 thousand rubles. Thus, the production of plinths from DP-BS is economically feasible. With production of 50 t/year, savings on raw materials will amount to 1.96 million rubles.