FI76728C - Process for making composite materials of particles consisting of polymeric lignocellulosic material - Google Patents

Description

1 76728

This invention relates to a process for preparing a composite material from lignocellulose-based particles, wherein the particles are bonded together by a polymeric compound formed by cross-reacting the starting material of the starting material by reacting into a cured mass in a heated state.

Composite materials based on plant raw materials, especially wood parts, fibers, chips, sawdust and the like, are currently prepared by mixing dry and hydrophobicized particles with various binders, mainly heat-curable binders, e.g. urea formaldehyde resin, and then casting at 130 ° C. to the required shape of the component, mainly plates. These materials are produced in a variety of grades that differ in the type of raw material, type of binder, casting pressure and temperature. Their common main disadvantage is the long-term sustained release of resinous binder degradation products, namely form-25 aldehyde, urea-formaldehyde oligomers or phenol, which have carcinogenic or other undesirable metabolic effects on the human body. As these materials, especially particle board, have recently become increasingly important components of living spaces, the disadvantage of the above-mentioned known composite materials made of plant parts or particles has become very serious. The intrusion of these products into the interiors of buildings should be prevented by various measures, which increases construction costs.

35 For the time being, the joining of wooden parts is done with the help of various adhesives, which are applied to the contact surfaces of the 2 76728 parts to be joined. In addition to the need to apply an adhesive layer to the surfaces of the joint to be formed, either cold or heated, depending on the type of adhesive used, the joint should be allowed to stand for a relatively long time to ensure water evaporates from aqueous adhesives, solvent evaporates or monomeric adhesives polymerize, in some cases at elevated temperatures and pressures. Some adhesives are harmful to health during their preparation or during the use of adhesive-bonded parts. This is especially true for adhesives that contain formaldehyde, which has carcinogenic or other undesirable metabolic effects in humans. Thus, the bonding of wood and ligocellulosic materials by gluing is still quite time consuming and often also consumes a lot of energy, especially in the production of wide-area composite parts, namely plywood and veneering of wood or lignocellulosic material bases.

Another disadvantage of such known composite materials 20 is the complexity of the manufacturing process, the preparation of the precondensate, and the precise control of the technical process necessary to achieve the required product quality. Thus, when using these materials, it is not possible to improve productivity by shortening the production cycle. During production, namely during die-casting, large amounts of formaldehyde-containing reaction products are released from the cast material in high concentrations. Another disadvantage is the high cost of the products made of said known materials, which is due to the relatively large amounts of binder which are generally present in the products in an amount of 10 to 30% by weight.

These disadvantages are reduced in the process for preparing a composite material according to the invention, in which particles of polymeric lignocellulosic material are contacted with an activating agent and compressed in a heated state 3,76728 into a cured mass without the addition of a binder, which process is characterized by a reagent selected from the group consisting of sulfuric acid, concentrated nitric acid, concentrated phosphoric acid, concentrated urea sulfate, concentrated ammonium bisulfate and mixtures thereof, are used as an activator only to depolymerize the surface portions of at least a portion of the lignocellulosic moiety. The effect of the activating agent can be increased by means of a catalyst or reduced by a neutralizing agent. If desired, at least one compound selected from furyl alcohol, furyl acetone, phenol, phenol precondensate and thermoplastic is adjusted.

The main advantage of the composite material produced by the method of the invention is the formation of a binder necessary for bonding the individual particles to be joined directly from the material of these particles by means of an activating agent, for example sulfuric acid, applied to the surface of said particles. The products made from the composite material thus obtained contain exclusively the starting material as well as a small amount of inactivated substances which are completely harmless to health, and in addition the cost of producing relatively expensive binders is avoided. The preparation of the material before die casting takes place in one step and consists of the application of an activating agent to the surface of the plant-derived particles.

Another advantage of the method according to the present invention is the possibility to utilize the material actually considered as waste, for example the bark. There is also no need to reduce the water content of the particles, daily as in known methods, so that the energy required to dry the starting material is saved.

In the process of the invention, the activating agent is allowed to act on a portion of the lignocellulosic starting material, whereby the initial high molecular weight polymeric binder of the starting material decomposes into monomer, followed by neutralization of excess activating agent and pressure and heat to particles at least partially covered by the monomer layer. as a derivative that connects the individual parts of the material together.

The activating agent can be added to only a part of the particles of the plant-derived starting material, which part is then mixed with the remaining 5 parts, and this mixture is formed into a product in a cohesive form.

The starting material used for the production is parts of plants containing lignocellulosic material consisting of polysaccharides, lignin, tannins, essential oils, etc., for example pieces of wood, chips, sawdust, corn cobs and dry stalks crushed, as well as various fibers. The resulting material is cohesive and is die-casted especially into sheets, ingots, etc., whose strength, other mechanical properties and other parameters depend significantly on the starting material and the manufacturing process. The available material can be used in the form of sheets, ingots and other die-cast products as components of buildings or furniture, for insulation purposes, etc.

The hydrolytic action of acids is used in the manufacturing process to release furylaldehyde and its derivatives and to activate lignocellulosic materials. The monomeric reactive compounds liberated in this way are converted in an acidic medium and at elevated temperature and pressure into a crosslinked polymeric material having a structure similar to that of the original plant mass. The amount of monomer released is controlled by the degree of activation and, together with the casting pressure, determines the properties of the product. However, this fact does not preclude possible modifications to the characteristics of the product by the addition of suitable additives.

Excess acidic activating agent mixed with the particles is neutralized prior to die casting by the addition of basic substances, especially urea, a mixture of urea and ammonium sulfate, time soaps, Lewis bases, or mixtures of these compounds. The Lewis base in this context should be considered to be compounds capable of donating an electron pair. The activator is added to the particles in the form of a gas, aerosol or solution, which can be diluted with inert solvents. The starting ingredients are left at the same moisture content as before they were treated, or a hydrophobic coating can be applied to their surface if desired.

Prior to die casting, so much heat is applied to the particles that their temperature rises to 80-200 ° C, and then particles, at least some of which have activated monomer on their surface, are compressed in a mold with a sealing pressure of 0.2-10 MPa. The properties of the material obtained depend on the casting pressure and also on the quantity and quality of the activating agent.

According to another possible procedure, the particles, at least part of the surface of which is activated, are placed in layers, the at least two layers containing particles mixed with different amounts or grades of activating agent or neutralizing agent.

The method according to the present invention also makes it possible to form adhesive joints of wood or lignocellulosic parts without the use of a special adhesive, since the necessary connecting structure is created on the contact surfaces of the joined parts directly from the material of these parts. Wood and lignocellulosic-25 co-materials include polysaccharides, lignin, tannins, essential oil and the like. Initiation of the surface hydrolysis of wood or the like by acidic or enzymatic means produces adhesive compounds in the wood, which make it possible to form a cohesive bond, as they form pressure-reinforced polymeric molecules extending into the joint and partially attached to the original parts in the structural network of each connected part.

35 Expensive or harmful adhesives are not required to form an adhesive joint, which thus contains only compounds with practically the same composition as the original material. The main advantages are high production capacity, lower price and faster production process.

The method according to the invention can be used for the production of plywood, for gluing veneers to various ligno-5 cellulose bases and for shaping various objects from laminated wood. Such a production of a laminated product is particularly advantageous when the core is formed from die-cast parts or wood bonded with a regenerated polymeric material and covered on both sides with wood veneer or plywood, which is also fixed by means of regenerated active pressure.

The properties of the final product depend on the casting pressure and the amount of binder on the contact surfaces of the cast particles and can be the same for the entire thickness of the product or vary in different layers of the product. The products obtained from the composite material are mainly in the form of sheets, ingots and other cast articles and can be used as various parts used for structural, insulating and other purposes.

The binding effect of the binder formed from the lignocellulosic material can be increased by adding a phenol derivative which partially forms a furylaldehyde sol which is thermosetting.

The die casting 25 of the products made of the parts is made by compressing the particles together at a casting pressure of 0.2 to 10 MPa at a temperature of 80 to 200 ° C under a casting pressure of 5 to 300 s.

The process of this invention can be successfully modified by applying a catalyst that promotes hydrolysis of the original material to the contact surfaces. Examples of such catalysts are potassium permanganate, aluminum, zinc and metal hydrides.

The composition and preparation of the composite material according to the invention are illustrated by the following examples, which, however, do not limit the scope of the invention in any way.

7 76728

Example 1

To prepare the product from the composite material according to the invention, 100 parts by weight of spruce chips were fed to a drum mixer and the chips were sprayed with concentrated sulfuric acid mist in air by means of a spray device. The total amount of sulfuric acid added was 3 parts by weight. Then, 6 parts by weight of powdered urea was added and mixed with the chips and sulfuric acid to form a castable mixture. The original polymer on the chip surface was activated, i.e., converted to monomeric by sulfuric acid, and the excess sulfuric acid was neutralized in the next step with added ure. The cast mixture was then die-cast at 180 ° C with a sealing pressure of 8.0 MPa for 5 min. The product removed from the press after 5 minutes had a flexural strength of 12.0 MPa and a density of 950 kg / m 3.

Example 2

Crushed dry corn straw waste was placed in a drum mixer in 100 parts by weight and 5 parts by weight of 96% sulfuric acid was added by spraying as homogeneously as possible on the surface of the dry straw. 7 parts by weight of powdered urea were then added with stirring, and the resulting mixture was die-cast at 160 ° C with a sealing pressure of 8.0 MPa. The final properties were formed under pressure for 4 min when the activated monomer formed crosslinks on the surface of the particles to give a polymer substantially similar to the starting polymer; i. the flexural strength was at least 1.2 MPa and the density 700 kg / m.

Example 3

A total of 100 parts by weight of the 3: 1 mixture of wood chips and sawdust was fed to a drum mixer. 4 parts by weight of sulfuric acid were uniformly applied to the surface of the particles as an aerosol. Then 6 parts by weight of powdered urea were added and the mixture was mixed thoroughly. The cast mixture was die-cast in a press at a final pressure of about 2.0 MPa at 170 ° C for 6 min. The product had a flexural strength of at least 10 MPa and a density of more than 800 kg / m 3.

0 76728

Example 4

Birch chips (100 parts by weight) and 8 parts by weight of powdered urea were mixed together in a mixer. Then, 6 parts by weight of 80% phosphoric acid 5 was dispersed in a spray device. The prepared mixture was die-cast at 170 ° C and 8 MPa for 6.5 min. The product obtained had a density of 0.65 g / cm 3 and a flexural strength of at least 1.5 MPa.

Example 5 10,100 parts by weight of softwood chips were mixed with 6.25 parts by weight of powdered urea and then 6.25 parts by weight of 65% nitric acid were applied to the mixture. The material obtained by die casting the mixture at a pressure of 8 MPa and a temperature of 170 ° C for 7 min had a density of 0.65 g / cm 3 and tensile and tensile strengths of at least 1.5 MPa.

Example 6 4 parts by weight of spruce chips were mixed in a mixer with 4 parts by weight of powdered urea and 3 parts by weight of potassium permanganate-binding compounds as a catalyst for accelerating the activation. Then, 4 parts by weight of 96% sulfuric acid was added to the mixture as a fine mist in air.

The mixture was die-cast at 150 ° C and 10 MPa 3 for 2 min. The product had a density of 0.95 g / cm and a flexural strength of 15 MPa.

25 Example 7

The mixture of Example 1 was die casted at the same pressure at 80 ° C for 10 min. The features of the product were the same.

Example 8 The surfaces of the veneers forming the layers of plywood to be made were coated by brushing or spraying a concentrated or diluted acid, especially sulfuric acid, to initiate hydrolysis of the wood surface at the veneer contact surfaces to form the active monomer 35 upon hydrolytic degradation of the original polymer. To neutralize any excess sulfuric acid, powdered urea was sprinkled on the contact surfaces of the veneers.

9,76728

The veneers were then laminated, pressed and pressed at a pressure of 2.0 MPa at 160 ° C for 15 s. The active monomer was converted by pressure and heat to a regenerated polymer with macromolecules bonded to each other and to the original material of the veneers. The tight contact of the contact surfaces is achieved in this way and the product is ready after removal from the press.

Example 9 In order to form an adhesive bond between two 5-10 mm thick wood and / or lignocellulosic parts, for example to form a pin or blade connection or to fasten the corners of galvanizing pins, concentrated acid, in particular sulfuric acid, was applied to the contact surfaces of the parts activated monomers were formed on the contact surfaces of the parts from their own material through acid hydrolysis. The contact surfaces were then pressed together, the joined parts were placed in a press where the contact surfaces were pressed at a pressure of 6.0 MPa at a temperature of 180 ° C for 180 s. The connection was complete when the product was removed from the press.

Example 10

In preparing the coated particle board, six chips were first made and fed 100 parts by weight into a rum-25 mixer, where they were coated with 5 parts by weight of 96% sulfuric acid by means of a spray device. To neutralize excess, unreacted sulfuric acid, 7 parts by weight of powdered urea was applied to the mixture. The mixture thus prepared was transferred to a mold on the bottom of which 30 of the sheath layers were placed, for example wood veneer, plywood or fibreboard. The surface of this layer was pre-equipped with a layer of sulfuric acid to effect surface hydrolysis. The overlying sheath layer, for example wood veneer, plywood or fibreboard, as above, with sulfuric acid applied to the contact surface, was then placed on top of the layer containing activated wood chips. The mold was then sealed and the contents compressed at a sealing pressure of 8.0 MPa and a temperature of 180 ° C for 5 min. Thus, a laminate sheet with a las-core was prepared by a single-step 3 process, and the sheet had a density of 950 kg / m 3 and a flexural strength greater than 12 MPa.

Example 11

Wood chips (300 g) mixed with 10 g of phosphorus pentoxide were mixed in a drum mixer. This mixture was compression molded at 1 MPa at 180 ° C for 10 min. The resulting sheet in the form of a sheet had a flexural strength of 11.0 MPa.

Example 12

Wood chips (300 g) and ammonium hydrogen sulfate (30 g) were mixed together in a tumble mixer. The mixture was press-15 poured at 180 ° C for 7 min. The product in the form of a sheet obtained had a flexural strength of 18.0 MPa.

Example 13 38 g of an 80% aqueous solution of urea sulphate was sprayed onto the surface of wood chips (300 g) in a tumble mixer. The mixture 20 was compression molded at 180 ° C for 3 min to give a product in the form of a sheet with a flexural strength of 18.6 MPa.

Example 14

Wood chips (250 g) coated with acid-25 catalyst were mixed in a tumble mixer with a mixture of 150 g wood chips 34 g urea sulphate 20 g furyl alcohol 30 10 g furyl aldehyde.

The mixture was compression molded at a pressure of 0.80 MPa at 80 ° C for 8 h. The compressive strength of the obtained cubic product was 44.5 MPa.

Example 15 35 300 g of sawdust and 14 g of ammonium hydrogen sulphate were mixed in a drum mixer, and to this mixture were added about 76728 20 g of furyl alcohol and 10 g of furyl aldehyde. The mixture was compression molded at a pressure of 0.8 MPa at a temperature of 80 ° C for 8 h. The compressive strength of the cubic cast product was 23.8 MPa.

5 Example 16

To the mixture of Example 1 was added 5 parts by weight of emulsion polyvinyl chloride, and the mixture was compression molded at 180 ° C and 2 MPa for 5 min. The resulting material had a flexural strength of 21.9 MPa and withstood 10 volumes of water without change in volume.

Example 17

To the mixture of Example 1 neutralized with a mixture of urea and ammonium sulfate was added a powder mixture of polyvinyl chloride + chlorinated polyethylene in a weight ratio of 1: 1. The resulting mixture was compression molded at 180 ° C

At a pressure of 6 MPa for 6 min. The resulting material had a flexural strength of 19.6 MPa and was resistant to water without changing the volume.

Example 18

Powdered polypropylene was added to the mixture of Example 3 and injection molded at 180 ° C.

At a pressure of 1.9 MPa for 5 min. The obtained composite material had a flexural strength of 22.3 MPa and good water resistance.

Claims (5)

12,76728 A process for preparing a composite material from particles 5 of polymeric lignocellulosic material by contacting them with an activating agent and pressing them into a cured mass in a heated state without the addition of a binder, characterized in that a reagent selected from the group consisting of concentrated sulfuric acid, concentrated nitric acid, concentrated nitric acid concentrated ureas sulphate, concentrated ammonium bisulphate and mixtures thereof, are used as activator only to depolymerize the surface parts of at least part of the lignocellulosic particles. A method according to claim 1, characterized in that the activating agent is applied to the particles 15 as an aerosol. Process according to Claim 1 or 2, characterized in that concentrated sulfuric acid is used as activating agent. Method according to one of Claims 1 to 3, characterized in that at least one thermoplastic is added to the lignocellulosic particles. Process according to Claim 4, characterized in that polyvinyl chloride is used as the thermoplastic.