RU2440234C1 - Method of producing insulation composite plates from vegetable wastes - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to woodwork industry, particularly, to compacted articles from particles of vegetable origin. Proposed method comprises preparing, prior to hot forming, a mix of wood substance hydrolysed overheated steam. Said substance represents chips of birch and larch, saw dust of pine, and inert filler from particles of pine or birch bark, not processed by overheated steam, in the form of particles of outer coat, phellem, leptome taken in amount of 30÷70% of total amount of mass to be compacted. Compaction conditions: temperature - 120÷140°C, pressure - 50 kg/cm², process rate - 1 min/mm of plate thickness.

EFFECT: efficient wood material with low heat conductivity.

3 ex

Description

The invention relates to the woodworking industry, in particular to the production of pressed articles from particles of vegetable origin (crushed wood, sunflower husk, wood bark, etc.), and can be used to obtain insulating composite slab materials without the use of synthetic binders. Products can be used as heat and sound insulating, structural, finishing materials in construction.

Known methods for producing composite materials based on particles of plant origin. Mostly these materials consist of two parts: wood filler and polymer binder. Synthetic thermosetting resins based on phenols, urea, formaldehyde, and isocyanates are used as polymer binders.

The disadvantage of the described compositions is that they are toxic to humans: in the manufacture and subsequent operation of finished products, pairs of phenol, formaldehyde and other substances that irritate the skin and mucous membranes are released. Another serious drawback of such compositions is that synthetic binder roads, since the main raw material for their production are petrochemical products. An important drawback of such materials is their low performance (strength, water resistance), which imposes restrictions on the field of application or leads to the need for additional protective coatings, the introduction of reinforcing additives or the creation of multilayer structures in which each of the layers has specific properties. The use of traditional technologies for the manufacture of composite materials based on wood and vegetable waste does not imply the possibility of obtaining materials in a one-stage process of pressing with a combination of both high strength and hydrophobic properties and thermal insulation characteristics. Typically, such materials are characterized by either high strength and density with a high thermal conductivity, or low thermal conductivity (insulation plate) with an extremely low density and strength.

A known composition based on particles of lignified raw materials for the manufacture of extruded plates without adding binders from the outside and a method for producing extruded products from wood material without adding binders to it [RF patent No. 2033319].

The disadvantage of the described composition and method is that required grinding of raw materials to a size of 2 ÷ 3 mm is required, and pressing is carried out in harsh conditions: at high pressure (up to 30 MPa) and high temperature (200 ÷ 220 ° C), exceeding the temperature of the onset of thermal degradation wood. The proposed composition and method for producing plates are based on the physical effect on wood (temperature, pressure), as a result of which hydrogen bonds are predominantly formed. The high density of composites (1300 ÷ 1400 kg / m ³ ) provides them with very high strength properties, but cannot provide high water resistance. Due to the high density and high thermal conductivity, the plate material manufactured in accordance with this description cannot be used in heat and sound insulation structures without additional modification.

Known structural heat-insulating panel [RF patent on PM No. 82240], made in the form of two outer layers of approximately chipboard (OSB) and located between them a heat-insulating layer of polystyrene foam or polyurethane foam bonded with polymer compounds. The presence of a heat-insulating layer of synthetic materials allows to obtain a material with high heat and sound insulation characteristics. Moreover, the need to form a multilayer composition using OSBs based on synthetic thermosetting resins and the use of compounds make such a panel expensive and environmentally unsafe.

Of the known technical solutions, the closest in purpose and technical nature to the claimed object is a method for producing composite materials from particles of lignocellulosic material, comprising cellulose, lignin, hemicellulose containing free sugars obtained from the carbohydrate part of plant material when treated with a catalyst and steam [RF patent No. 2075384, RF patent No. 2152966].

Composite material is obtained by hot pressing of lignocellulosic material treated with steam at a temperature of 170 ÷ 260 ° C with or without a catalyst, without additional introduction of any binding substances. The pressing temperature lies in the range 160 ÷ 250 ° C [RF patent No. 2075384] and 120 ÷ 160 ° C [RF patent No. 2152966].

The disadvantage of the method for producing composite materials based on the described press compositions is that the claimed methods practically do not allow to obtain an insulating composite material with a thermal conductivity of less than 0.25 W / m × K and at the same time high strength and hydrophobic characteristics.

The aim of the invention is to obtain an inexpensive durable and moderately hydrophobic composite material with a thermal conductivity of less than 0.15 W / m × K from plant materials without the use of any binders other than those formed in the raw materials during high-temperature steam processing under pressure.

The essence of the invention lies in the fact that the proposed method for producing insulating composite boards from a press composition containing hydrolyzed lignocellulosic particles and untreated particles of wood bark, providing the formation of the internal fine-porous structure of the composite laminate with a low coefficient of thermal conductivity. Hydrolyzed lignocellulosic particles play the role of a binder component that provides the mechanical strength of the plates, and the bark acts as a low-density environmentally friendly aggregate with a low coefficient of thermal conductivity, which makes it possible to use such plates as heat insulation. It should be noted that the method proposed in accordance with the description [RF patent No. 2075384] also suggests the possibility of using wood bark in the production of composite materials, however, in the process of preparing the press material, it should be subjected to hydrolytic treatment along with the main wood pulp, i.e. in the original, unmodified form in the finished plate material is not present.

The claimed invention allows to obtain an insulating composite material with acceptable physical and mechanical characteristics based on any lignocellulosic raw materials without the use of any binders other than those formed in the lignocellulosic complex during its processing by superheated steam under pressure.

The claimed invention is devoid of the aforementioned disadvantages associated with the need to use phenol, urea-formaldehyde and isocyanate thermosetting binders, and also allows to obtain a material with a thermal conductivity (according to GOST 19592, GOST 7076) of not more than 0.15 W / m × K without creating complex multilayer compositions.

The implementation of the claimed invention is achieved in that the method for producing a heat-insulating composite material according to the invention includes soaking lignocellulosic raw materials with tap water, taken in an amount of 1 parts by weight / 1 parts by weight raw materials, within 20 ÷ 40 minutes and processing (hydrolysis) of the material thus prepared by steam under pressure at a temperature of 180 ÷ 200 ° C for 7 ÷ 10 minutes, sufficient for the decomposition of hemicellulose into free sugars and other products. In order to create a heat-insulating composite boards, in accordance with the claimed invention, it is proposed to hot-press hydrolyzed and dried lignocellulosic particles laid in a mold in a mixture with particles of untreated wood bark. Hot pressing is carried out without the addition of binders. The present invention allows to obtain insulating composite materials, characterized by high strength properties, hydrophobic properties and dimensional stability. In the forming composite structure, gyrolyzed lignocellulose particles play the role of a binder, and untreated bark particles play the role of an inert low-density aggregate, the presence of which leads to a significant decrease in the thermal conductivity of the material. The invention suggests the possibility of using any parts of the bark, regardless of the place of selection from the structure of the tree - the outer cover layer, cork, bast.

The mixing of the components during the formation of the press mass can be carried out in any ratio. An increase in the fraction of crust particles in a composite material leads to a proportional decrease in the thermal conductivity of the material (improvement of thermal insulation properties) and a decrease in strength parameters. Upon receipt of a composite material with acceptable mechanical characteristics, having insulating properties, it is advisable to maintain the mass fraction of the hydrolyzed substance (binder) used in the press mass in the amount of 70 ... 30%, respectively, the fraction of bark particles (filler) - 30 ... 70%.

The thickness of the carpet from a mixture of hydrolyzed lignocellulosic pulp and bark, placed on the mold matrix before pressing (20 ÷ 500 mm), is determined by the degree of dispersion of the hydrolyzed pulp, the size of the bark particles and the required thickness of the finished plate (5 ÷ 80 mm).

In the process of hot pressing of the laid layered composition, several components are softened (free sugars, low molecular weight lignin), their penetration is not shallow (“impregnated”) in the adjacent filler particles, and strong chemical-mechanical bonds between the particles of the pressed material arise in the material due to polycondensation processes.

The pressing of a fibrous carpet, in accordance with the claimed invention, is carried out at a temperature of 120 ÷ 140 ° C and a specific pressure of 50 kg / cm ² . The duration of pressing after heating the entire press mass to a predetermined temperature is 1 min / 1 mm of the thickness of the product.

Example 1. Air-dry birch wood in the form of technological chips is subjected to soaking with tap water, taken in an amount of 1 part by weight / 1 part by weight raw materials, for 40 minutes and treated (hydrolyzed) with saturated steam under pressure at a temperature of 190 ° C for 10 minutes.

Composite material from the obtained pulp (after drying to a moisture content of 7%) and filler from the particles of the outer cover layer of the pine bark was made by hot pressing under pressure in a collapsible mold with a base area of 50 × 150 mm ² . A mixture of hydrolyzed birch wood taken in an amount of 50 g and bark particles of 5 ... 8 mm in an amount of 30 g is placed in the mold. After molding, cold pressing was carried out at a pressure of 20 kg / cm ² and then hot pressing was carried out at 140 ° With a specific pressure of 50 kg / cm ² . Duration of pressing 1 min / mm of the finished plate. After that, the resulting product was cooled to 45 ° C for 15 minutes while gradually relieving pressure to zero.

For comparison, the same hydrolyzed lignocellulosic material, taken in an amount of 80 g, was subjected to hot pressing in the absence of the addition of untreated bark. The pressing conditions were the same.

Composite material pressed from a press composition containing bark has the following characteristics:

density, kg / m ³ - 820;

tensile strength under static bending, MPa - 24;

coefficient of thermal conductivity, W / m × K - 0.12;

water absorption in 24 hours,% - 27.3;

swelling in 24 hours,% - 23.6.

Comparative characteristics of a composite material pressed from a bark-free press composition:

density, kg / m ³ - 1208;

tensile strength under static bending, MPa - 41;

coefficient of thermal conductivity, W / m × K - 0.28;

water absorption in 24 hours,% - 22.7;

swelling in 24 hours,% - 20.7.

Example 2. Air-dry pine sawdust is subjected to soaking with tap water, taken in an amount of 1 parts by weight / 1 part by weight raw materials, for 20 minutes and treated (hydrolyzed) with saturated steam under pressure at a temperature of 200 ° C for 7 minutes.

Composite material from the obtained hydrolyzed wood pulp (after it was dried to a moisture content of 8%) and particles of the outer cover layer of pine bark was made by hot pressing under pressure in a collapsible mold with a base area of 50 × 150 mm ² . A mixture of hydrolyzed sawdust in an amount of 50 g and bark particles of 5 ... 8 mm in an amount of 50 g are placed in the mold. After molding the carpet, cold pressing was carried out at 20 kg / cm ² and then hot pressing was carried out at 130 ° C at specific pressure 50 kg / cm ² . Duration of pressing 1 min / mm of the finished plate. After that, the resulting product was cooled to 45 ° C for 15 minutes while gradually relieving pressure to zero.

For comparison, the same hydrolyzed lignocellulosic material in an amount of 100 g was subjected to hot pressing in the absence of the addition of bark particles. The pressing conditions were the same.

Composite material pressed from a press composition containing bark has the following characteristics:

density, kg / m ³ - 680;

tensile strength under static bending, MPa - 18;

coefficient of thermal conductivity, W / m × K - 0.1;

water absorption in 24 hours,% - 17;

swelling in 24 hours,% - 15.

Comparative characteristics of a composite material pressed from a bark-free press composition:

density, kg / m ³ - 1332;

tensile strength under static bending, MPa - 35;

coefficient of thermal conductivity, W / m × K - 0.26;

water absorption in 24 hours,% - 6.3;

swelling in 24 hours,% - 7.4.

Example 3. Air-dried larch wood in the form of technological chips is subjected to soaking with tap water, taken in the amount of 1 parts by weight / 1 part by weight raw materials for 40 minutes and treated (hydrolyzed) with saturated steam under pressure at a temperature of 200 ° C for 10 minutes.

Composite material from the obtained pulp (after it was dried to a moisture content of 7%) and a filler from the particles of the outer cover layer of birch bark was made by hot pressing under pressure in a collapsible mold with a base area of 50 × 150 mm ² . A mixture of hydrolyzed larch wood taken in an amount of 30 g and bark particles of 5 ... 8 mm in an amount of 70 g is placed in the mold. After molding, cold pressing was carried out at a pressure of 20 kg / cm ² and then hot pressing was carried out at 140 ° With a specific pressure of 50 kg / cm ² . Duration of pressing 1 min / mm of the finished plate. After that, the resulting product was cooled to 45 ° C for 15 minutes while gradually relieving pressure to zero.

For comparison, the same hydrolyzed lignocellulosic material, taken in an amount of 100 g, was subjected to hot pressing in the absence of the addition of untreated bark. The pressing conditions were the same.

Composite material pressed from a press composition containing bark has the following characteristics:

density, kg / m ³ - 620;

tensile strength under static bending, MPa - 12;

coefficient of thermal conductivity, W / m × K - 0.08;

water absorption in 24 hours,% - 51.7;

swelling in 24 hours,% - 45.4.

Comparative characteristics of a composite material pressed from a bark-free press composition:

density, kg / m ³ - 1243;

tensile strength under static bending, MPa - 39;

coefficient of thermal conductivity, W / m × K - 0.27;

water absorption in 24 hours,% - 24.7;

swelling in 24 hours,% - 21.5.

Information sources

1. RF patent No. 2033319 dated 10.27.92, MKI 4 B27N 3/02.

2. RF patent for ПМ №82240 dated 04/20/2009, IPC E04C 1/40.

3. RF patent No. 2075384 of 03.20.97, MKI 6 B27K 9/00.

4. RF patent No. 2152966 from 07.20.2000, MKI 7 C08L 97/02, B27K 9/00, B27N 3/04, B27N 3/18.

Claims (1)

The method of producing insulating composite boards without adding a binder from hydrolyzed lignocellulosic material selected from the group: birch chips, larch chips, pine sawdust and thermally untreated particles of pine bark or birch bark in the form of particles of the outer covering layer, cork tissue, bast, characterized in that , in order to reduce the thermal conductivity of the plate, the fibrous press pulp before hot pressing is obtained by mixing hydrolyzed lignocellulosic material and untreated bark particles taken in col honors 30-70% of the total mass of the press:
pressing parameters:
temperature 120 ÷ 140 ° С;
pressure 50 kg / cm ² ;
duration 1 min / 1 mm of plate thickness.