RU2707936C1 - Method for radiation-chemical modification of wood-polymer composites - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction materials and can be used in woodworking industry to obtain wood-polymer composite materials with improved operational characteristics. Described is a method for radiation-chemical modification of composites, consisting in radiation treatment of filled wood-polymer composite material, characterized by that composite of composition (weight parts): wood filler/polyolefin/process additive containing cross-linking agent (60–80)/(40–20)/(5–10) is subjected to radiation treatment at room temperature by exposure to gamma radiation in the range of absorbed doses of 50–100 kGy.

EFFECT: technical result is longer service life of article.

9 cl, 3 dwg, 3 tbl

Description

1. TECHNICAL FIELD

The invention relates to the field of building materials and can be used in the woodworking industry to obtain wood-polymer composite materials with improved performance characteristics.

2. CHARACTERISTICS OF ANALOGUES OF THE INVENTION

Known [Pesek M] is a method for producing wood-polymer materials (PDM) and products, for example, beech mosaic tiles containing 56% monomer and having 4-5 times higher hardness, and comprising two stages: impregnation of wooden blanks with monomers or synthetic resins, followed by polymerization.

The disadvantages of this method are the high consumption of monomer, complex hardware design, heterogeneity of the properties obtained PDM by volume. These disadvantages are due to the uneven flow of the polymerization process in the volume of the product due to the concentration gradient of monomer over the volume of the product that occurs at the stage of impregnation of the workpiece.

Known [Czvikovszky T.] a method of producing polypropylene (PP) with improved strength properties, allowing to obtain PP with a tensile strength (bending) of 28.8 (51.8) N / mm ² and elastic modulus, respectively 4590 (3870) N / mm ² , containing the stages of polymer modification by irradiated wood fibers with a diameter of 10-50 μm and a length of 100-200 μm at a concentration of 45%, which were then impregnated with polyester resins, mixed with PP granules and subjected to pressing.

The disadvantages of this method are the complex hardware design, low productivity, uneven distribution of strength properties of the modified PP in the volume of the sample. These disadvantages are due to the uneven distribution of polyester resins over the product volume that occurs at the stage of impregnation of the PP / irradiated wood fiber composite material, which entails the uneven reaction between the polyester resins and irradiated wood fibers. As a result, the effect of improving the strength properties of PP can be unstable.

3. PROTOTYPE CHARACTERISTICS AND CRITICISM OF ITS DISADVANTAGES

Closest to the technical nature of the claimed method is a method of producing high strength, multilayer, resistant to acids, alkalis, organic solvents of materials by modification of low-value wood varieties [RF Patent No. 02099154]. The known method involves the impregnation of porous materials with gaseous alkenes or their mixture with monomers and / or oligomers, followed by exposure to accelerated electrons with an energy of 0.4-1 MeV in a constant electric field with a strength of 0.5-1.5 kV / cm

The disadvantages of this method are the uneven spatial distribution of the properties of the material over the volume of the radiation-modified sample, complex hardware design, the presence of consumables, the need for joint exposure to the electron flow and a constant electric field, as well as the presence of restrictions on the thickness of the irradiated workpiece. These drawbacks are due to the small path length of the electrons in the treated wood with an uneven spatial distribution of the modifying additive over the volume of the sample.

4. TECHNICAL RESULT

The technical result achieved by the proposed method of radiation-chemical modification of WPC is the elimination of the above disadvantages of analogues and prototype, namely: limitations on the thickness of the modified wood-polymer materials, uneven distribution of operational properties over the volume of radiation-modified wood-polymer material, complex hardware design, simultaneous exposure the flow of electrons and external electric fields, the use of gaseous reagents.

5. ESSENCE OF TECHNICAL SOLUTION

The claimed method of radiation-chemical modification of wood-polymer composite (WPC) materials and products based on them, consisting of particles of wood filler and polyolefins, additionally containing additives of a mixture of substances commonly used in the manufacture of WPC using pressure mixing and described in a specialized literature, for example, by the applicant in application No. 2016102693/04. Under the technological additives in this application are understood chemicals that improve the quality of the composite, its uniformity, including reducing the surface activity of the particles of the polymer matrix and filler, usually playing the role of a lubricant between the particles and contributing to the compaction of the particles of the components during compression. Such substances usually include various paraffin derivatives, stearates, etc., known under the trademarks, in particular, such as Licowax E, Powersil Paste AP, Polybond 1009, Lotader AX8900, Acrawax C, etc., in addition to the composition of the additives are inhibitors oxidations like Irgafos and the like. The main feature of the application is that a chemical agent with a double bond is necessarily present in the composition of these inactive additives, which induces and sensitizes the crosslinking process under the radiation exposure of a certain energy, which belongs to the class of unsaturated organosilicon compounds, in an amount of about 2 weight. hours in relation to 100 weight. including non-irradiated composite polymer / wood filler. In general, technological additives amount to 10 weight. hours in relation to 100 weight. including composite, improving its quality, but not participating in the process of radiation modification, unlike the crosslinking agent.

In the case under consideration, the gamma radiation of the ⁶⁰ Co isotope with an average energy of 1.25 MeV and with a dose rate of 0.2 to 0.5 Gy / s or taking into account the measurement error using a Fricke dosimeter 0.35 is used for radiation modification ± 0.15 Gy / s.

Specifically, the wood-polymer composite material made by extrusion or thermal pressing of the “wood filler / polyolefin granules sizes from 160 to 330 microns, taken in ratios (60-80) / (40-20) weight, is subjected to radiation modification. o'clock, with a technological additive in an amount, as a rule, from 2 to 10 weight. including containing unsaturated organosilicon compounds as crosslinking agents. An alternative stage of impregnation is carried out in the liquid phase using a 2% (weight) solution of vinyltrimethoxysilane in acetone (or 2 parts by weight after drying and weighing the sample). As a filler, wood flour with a particle size of from 180 to 560 microns or crushed wood waste with a particle size of from 0.005 to 1 mm are used. Radiation modification is carried out in air or in an inert atmosphere at room temperature.

To solve the above problem, in a method involving the impregnation of WPC blanks with substances that cause the process of radiation crosslinking, and the subsequent exposure to ionizing radiation (II), the following new technological operations (TH) are introduced:

MOT No. 1 - the manufacture of a mixture of powders of wood filler, polyolefins (polyethylene (PE), PP), and technological additives containing, including unsaturated organosilicon compounds as initiators, sensitizers of radiation crosslinking; or

MOT No. 2 - liquid-phase impregnation of a mixture of powders of wood filler and granular polyolefins with a solution of a technological additive containing 2% (wt.) Solution of vinyltrimethoxysilane in acetone or using its own solution, and then adding technical additives in an amount of up to 10 weight. hours and subsequent drying of the mixture at room temperature for 24 hours;

MOT 3 - extrusion or thermal pressing of WPC blanks based on a mixture of wood filler (from 60 to 80 parts by weight) and polyolefin granules (from 20 to 40 parts by weight), with technological additives containing unsaturated organosilicon compounds as agents of radiation crosslinking (up to 10 parts by weight);

MOT 4 - radiation-chemical modification of WPC preforms up to doses of 100 kGy by exposure to ⁶⁰ Co gamma radiation with an average energy of 1.25 MeV, dose rate from 0.2 to 0.5 Gy / s (or taking into account the measurement error 0.35 ± 0.15 Gy / s) at room temperature, in an atmosphere of air or inert gas.

Known [Nikolova M.], a method of improving the deformation and strength properties of PE, including the stage of introducing into the polymer filler (chalk) at a concentration of 40% and subsequent crosslinking under the influence of gamma radiation (dose rate 13 kGy / hour), in which the radiation modification allows to improve the properties of the polymer due to the interaction of particles of a functional additive with fragments of the destruction of polymer chains. Moreover, in the absence of irradiation, the filler particles do not form chemical bonds with polymer chains.

In the inventive method, the improvement of the deformation properties of the WPC composition "wood filler / polyolefin / technological additive containing a substance-agent of radiation crosslinking" (60-80) / (40-20) / (up to 10) weight. hours, obtained by extrusion, pressing a mixture of powders of wood filler, polyolefin and a radiation crosslinking agent, and / or pre-impregnation of 2% (wt.) a solution of vinyltrimethoxysilane in acetone of a mixture of wood filler and granules of polyolefins, is achieved through radiation-chemical crosslinking reactions between the radicals or ions of the molecules of initiators, sensitizers of radiation crosslinking with polymer chains of polyolefins and lignin, which is part of wood. In this case, crosslinking reactions may occur in the absence of AI, during post-radiation processes involving active particles (radicals, ions) of the sensitizer agent, polyolefins and wood, which did not have time to recombine during radiation treatment.

As is known [Borisov EA, Krasovitskaya TI, Raichuk FZ], the radiation-chemical modification of DPPC at low dose rates allows increasing the crosslinking yield due to a decrease in the likelihood of recombination between the macroradicals of polyolefins, cellulose and a sensitizer. Carrying out the process in an inert environment is preferable to prevent the undesirable effects of oxidative processes developing in the surface layers of the duodenum, which can lead to a change in the color and surface properties of the material and / or product [Vaninskaya Yu.M.]. As a rule, [Raychuk FZ], the radiation modification of the WPC is carried out at room temperature, this allows us to simplify the process design and also to avoid the development of undesirable processes of thermal radiation destruction, which can impair the quality of the product.

Thus, the main technical result of the invention is achieved - radiation-induced improvement in the deformation properties of the WPC material based on mixtures of wood filler, polyolefin granules, a crosslinking sensitizer, introduced into the mixture at the stage of preparation of the technological additive composition containing unsaturated silicon-organic agent, and / or by direct impregnation with a crosslinking silicon-organic agent, such as vinyltrimethoxysilane, a mixture of wood filler and granules of polyolefins with technical additives, cat The other is due to increased intermolecular interaction between the components. The nature of the claimed technical result is associated with the formation in the volume of the material of a three-dimensional “network” of covalent chemical bonds as a result of radiation-initiated crosslinking reactions involving radicals and ions of molecules of unsaturated organosilicon compounds with lignin and macromolecules of polyolefins (table 1) [Charlesby A.].

The applicant has not found solutions that disclose a method of radiation-induced improvement in the deformation properties of WPC made by extrusion, heat pressing from mixtures of wood filler, polyolefin granules and a radiation crosslink sensitizer, introduced into the substrate or at the mixing stage as part of a technological additive containing unsaturated organosilicon compounds either by impregnation with a solution of the agent separately or as part of a technological additive (in both cases, up to 10 wt. h), exposure gamma radiation in doses up to 100 kGy with a dose rate of 0.2 to 0.5 Gy / s (or taking into account the measurement error of this parameter 0.35 ± 0.15 Gy / s) at room temperature, in air and / or in an inert atmosphere. Thus, the claimed solution has significant differences from known from the prior art.

6. LIST OF FIGURES OF GRAPHIC IMAGES

The invention is illustrated by illustrative materials, where:

FIG. 1 - Image of the cross-section of a sample of radiation-modified wood-polymer material produced by extrusion or thermal pressing, based on crushed wood waste (pine) (80 parts by weight), polypropylene granules (20 parts by weight), and a number of chemicals constituting traditional for WPC obtained by mixing with pressing, technological additive (10 wt. h.), and containing including unsaturated organosilicon compounds, image obtained by x-ray computed tomography at the mid-height of the sample. Positions: 1 - fragments of wood waste, 2 - particle impurities, 3 - particles of polypropylene, technological additives and wood flour. The measurements used samples of material with a diameter of 3 mm and a height of 6 mm.

FIG. 2 - Dependence on time of deformation of samples of wood-polymer composites based on mixtures of crushed wood waste (pine) (80 parts by weight) and polypropylene granules, sizes from 160 to 330 microns (20 parts by weight), and additionally a technological additive, containing unsaturated organosilicon compounds in a total amount of up to 10 weight. h. Position: 4 - procurement of non-irradiated wood-polymer material; 5, 6 - wood-polymer composite material, gamma-irradiated up to 50 and 100 kGy with a dose rate of 0.2 to 0.5 Gy / s, respectively, or taking into account the measurement error of this parameter with a Frickke dosimeter 0.35 ± 0.15 Gy / s Irradiation was carried out in air at room temperature. The deformation was investigated in uniaxial compression mode under the following conditions: applied voltage - 18 MPa, test temperature - room

FIG. 3 - Dependence of the strain rate on the strain value of wood-polymer composites based on mixtures of ground wood waste (80 parts by weight) and polypropylene granules (20 parts by weight) with a technological additive (10 parts by weight) containing unsaturated organosilicon compounds . Positions: 7 - preparation of wood-polymer material; 8, 9 - wood-polymer composite material, gamma-irradiated up to 50 and 100 kGy with a dose rate of 0.2 to 0.5 Gy / s (or taking into account the measurement error of this parameter with a dosimeter 0.35 ± 0.15 Gy / c), respectively. Irradiation was carried out in air at room temperature. The deformation was investigated in uniaxial compression mode under the following conditions: the value of the applied stress is 18 MPa, the test temperature is room temperature. The dashed lines show the strain values corresponding to the value of the limit of forced elasticity.

7. EXAMPLES OF SPECIFIC IMPLEMENTATION

Example No. 1. Improving the deformation properties of gamma-irradiated WPC samples based on mixtures of ground wood waste (pine) and polypropylene granules with a technological additive containing a crosslinking agent, composition 80/20/10 weight. hours obtained by extrusion.

Strain tests of non-irradiated and gamma-irradiated samples of WPC materials based on mixtures of ground wood waste with particle sizes from 0.005 to 1 mm (80 parts by weight) and PP granules with sizes from 160 to 330 microns (20 parts by weight) with technological additives (10 parts by weight) containing unsaturated organosilicon compounds such as vinyltrimethoxysilane (Fig. 1) were carried out using laser Doppler interferometry [Peschanskaya N.N.].

In FIG. Figures 2 and 3 show the experimentally recorded dependences of strain on time (ε ~ t) and strain rate on strain (ε ~ ε) for WPC samples based on mixtures of ground wood waste (pine) (80 parts by weight) and PP granules (20 parts by weight) with a technological additive (10 parts by weight) containing an unsaturated organosilicon compound, vinyltrimethoxysilane, of the source and gamma irradiated in air, at room temperature, to absorbed doses of 50 and 100 kGy with a dose rate of 0.2 up to 0.5 Gy / s or taking into account the error of its measurement, we dose Fricke's measure 0.35 ± 0.15 Gy / s, respectively. As follows from table 1, radiation treatment leads to a noticeable improvement in a number of deformation properties of DPKM, with the exception of a slight decrease in the compression modulus, which can be explained by the well-known fact of an increase in the tendency to embrittlement of polyolefins with increasing absorbed dose [Peschanskaya N.N.].

As a result of gamma irradiation up to 100 kGy, the limit of forced elasticity, i.e., the strain corresponding to the onset of plastic deformation of the material, increases by 25% compared with the initial DPPC. In addition, the durability of DPKM is significantly increased - the period of time required to achieve a strain of 5% increases by 1.62 and 3.46 times when irradiated to doses of 50 and 100 kGy, respectively (table 1). The maximum compression of the investigated PDM samples before failure was characterized through the strain corresponding to the achievement of the strain rate ε ~ 8⋅10 ^-5 s ^-1 : as follows from table 1, this value increases by 6 and 42% for the DPKM samples irradiated to 50 and 100 kGy at a dose rate of the order of 0.2 to 0.5 Gy / s or taking into account the measurement error of 0.35 ± 0.15 Gy / s, respectively.

Thus, the processing of extrusion DPCM based on mixtures of ground wood waste (80 parts by weight) and PP granules (20 parts by weight), with technological additives (up to 10 parts by weight) containing unsaturated organosilicon compounds, by exposure to gamma radiation of ⁶⁰ Co to doses of 50 and 100 kGy with a dose rate of the order of 0.2 to 0.5 Gy / s or taking into account the measurement error of this parameter 0.35 ± 0.15 Gy / s, allows to achieve the technical result disclosed in this invention. The nature of the effect of radiation modification can be associated with a change in the nature of the intermolecular interaction between the molecules of unsaturated organosilicon compounds and cellulose lignin, and PP macromolecules [Charlzby A.].

Example No. 2 Improvement of the deformation characteristics of gamma-irradiated wood-polymer material made by heat pressing of a mixture of powder of ultra-high molecular weight polyethylene (40 parts by weight) and wood flour (60 parts by weight), impregnated with a 2% (weight) solution of vinyltrimethoxysilane in acetone .

A mixture of wood flour with an average particle size of 180 to 560 μm (60 parts by weight) and powdered ultra-high molecular weight polyethylene (CBM PE) with an average particle size of 160-330 μm (40 parts by weight) was aged at 2% room temperature (weight.) a solution of vinyltrimethoxysilane in acetone for 24 hours, followed by bringing the content of the components of technical additives to 10 weight. o'clock (together with a crosslinking agent). Then the mixture was dried for 24 hours at room temperature in air. The method of thermal pressing (temperature 170-220 ° C, pressure from 7 to 10 MPa, processing time - 2 hours) were obtained DPKM blanks in the form of disks with a diameter of 60 mm, a thickness of 15 mm Samples for testing a cylindrical shape with a diameter of 3 mm and a height of 6 mm were obtained by microprocessing. Radiation treatment was carried out at room temperature, in a stream of nitrogen, in the range of absorbed doses from 15 to 100 kGy at a dose rate of 0.35 ± 0.15 Gy / s.

Strain tests of manufactured non-irradiated and gamma-irradiated DPKM samples were carried out at room temperature by laser Doppler interferometry [Peschanskaya N.N.]. The value of the applied voltage is 20 MPa.

As follows from table 2, radiation treatment leads to a significant increase in the durability of DPKM (by 5.3 times after gamma irradiation to 100 kGy at a dose rate of 0.35 ± 0.15 Gy / s). This decreases the rate of deformation of the material. However, the dynamics of radiation-induced changes in deformation upon reaching the limit of forced elasticity and actually the limit of forced elasticity is nonmonotonic in nature: in the range of absorbed doses of 15-50 kGy, there are no significant changes in the considered parameters of the DPCM deformation. The technical effect - an increase in the value of deformation during fracture and the limit of forced elasticity - is observed with an increase in the absorbed dose to 100 kGy.

Thus, the processing of DPPC obtained by thermal pressing, the composition of “wood flour / CBM PE" 60/40 weight. hours, impregnated with a solution of vinyltrimethoxysilane in acetone alone (2 parts by weight after drying) or as part of a technical additive (up to 10 parts by weight), by exposure to ⁶⁰ Co gamma radiation in the region of absorbed doses of 15-100 kGy at a dose rate 0.35 ± 0.15 Gy / s, allows to achieve the technical result of the claimed invention.

The nature of the effect of radiation modification is due to the formation of a three-dimensional "network" of covalent chemical bonds as a result of radiation-induced crosslinking reactions involving radicals and ions of vinyltrimethoxysilane molecules with lignin and CBM PE macromolecules (table 2) [Charles A.].

8. TECHNICAL-ECONOMIC OR OTHER EFFICIENCY

The present invention allows to increase the limit of forced elasticity of WPC based on mixtures of wood filler, granular polyolefins and a radiation crosslink sensitizer (table 1, 2), the value of which determines the onset of irreversible plastic deformation of the material, i.e. product service life. An increase in the operating resource allows reducing operating costs - for example, increasing the service life of a product based on DPKM, exposed to ⁶⁰ Co gamma radiation up to 100 kGy, by 1.3-1.5 times, reduces the volume of production from non-irradiated material and, accordingly, , reduces its consumption, equipment wear and so on.

Thus, the decrease in the production volume of PDMs based on radiation-modified mixtures of wood filler and granular polyolefins is taken as the basis for comparison in determining the annual economic effect. The calculation of the annual economic effect is made taking into account the actual costs incurred in the irradiation of the blanks of products or samples DPKM.

We define the value of the annual economic effect as the difference between the volume and cost (price) of production and operation of non-irradiated and radiation-modified DPCM (table 3). The increase in the operational resource allows reducing the output of WPC and products based on mixtures of wood flour and / or ground wood waste and granular polyolefins by an amount corresponding to the value of the effect of radiation-induced increase in the limit of forced elasticity (table 3). Summing up the production costs of a reduced number of products by extrusion technology and radiation treatment, and then comparing with the cost of manufacturing the required amount of unirradiated WPC based on mixtures of wood flour and / or ground wood waste and granular polyolefins, we can estimate the annual economic effect. As follows from table 3, the value of the annual economic effect can reach 3160000 (Three million one hundred sixty thousand) rubles.

LIST OF USED SOURCES

Borisov E.A. // Technology of radiation-chemical production of concrete-polymer and wood-plastic materials / Borisov EA, Raichuk F.Z., Shiryaeva G.V. - M .: Energoatomizdat, 1982.

Vaninskaya Yu.M. // Coloring of wood during radiation-chemical modification / Vaninskaya Yu.M., Kuchuk B.C. - Minsk: Science and technology, 1987. - 103 p.

Krasovitskaya T.I. // Experience of wood modification by polymerization of wood-impregnating monomers under the influence of γ-rays / Krasovitskaya TI // In the book: Proceedings of the II All-Union Conference on Radiation Chemistry / Ed. L.S. Polaka. - M.: Publishing House of the Academy of Sciences of the USSR, 1962 .-- S. 511-515.

Peschanskaya N.N. // Changes in the creep of polymethylmethacrylate after radiation exposure / Peschanskaya NN, Smolyanskiy AS, Surova V.Yu. // High molecular weight compounds. - 1992. - T. 34 B, No. 1. - S. 3-10.

Raychuk F.Z. // Radiation-chemical technology for the modification of porous materials / Raichuk F.Z. // Bulletin of the Association of business cooperation "Radtech-USSR." - 1991. - No. 1. - S. 24-30.

Method for the modification of porous materials: Patent No. 02099154 (Russia) dated 12/20/1997 IPC B05D 3/06; B5D 3/10 Application No. 96102366/04 of 02/09/1996 // Ponomarev Alexander Vladimirovich, Makarov Igor Sergeevich, Pohilo Sergey Borisovich.

Charlsby A. // Nuclear Radiation and Polymers / Charlsby A. - M.: Publishing, 1962. - 522 p.

Czvikovszkv T. // Modification of polypropylene with radiation-treated wood / Czvikovszky T., Tapolcai I. // Proceedings 5 ^th Tihany Symposium Radiation Chemistry, Siofok, 19-24 September, 1982. Vol. 2. - Budapest, 1983. - pp. 785-791 (discuss: 791-792).

Nikolova M. // Influence of fillers on the deformation behavior of cross-linked HDPE. Pt. II. Radiation cross-linking / Nikolova M., Mateev M. // Polym. Degrad. and stability. - 1991. - V. 31, No. 2.- pp. 203-210.

Pesek M. // Moznosti vyroby drobnych drevarskych vyrobku z drevoplastickych latek pomoci ruznych postupu / Pesek M. // Radioisotopy. - 1978. - V. 19, No. 1. - pp. 105-117.

Claims (9)

1. The method of radiation-chemical modification of composites, consisting in the radiation treatment of a filled wood-polymer composite material, characterized in that the composite composition (wt. H): wood filler / polyolefin / technological additive containing a crosslinking agent, (60-80) / (40-20) / (5-10) is subjected to radiation treatment at room temperature by gamma radiation in the range of absorbed doses from 50 to 100 kGy. 2. The method according to p. 1, characterized in that the irradiation is carried out at a dose rate of 0.35 ± 0.15 Gy / s. 3. The method according to p. 1, characterized in that the non-irradiated composite material is obtained by extrusion of a mixture of the composition: wood filler / polyolefin / technological additive. 4. The method according to p. 1, characterized in that the non-irradiated composite material is obtained by pre-impregnating a mixture of wood filler / polyolefin with a solution containing a cross-linking agent, either alone or as part of a processing aid, drying, placement in a mold and subsequent thermal pressing. 5. The method according to p. 1, characterized in that as a cross-linking agent use unsaturated organosilicon compounds. 6. A method according to claim 5, characterized in that vinyltrimethoxysilane is used as unsaturated organosilicon compound. 7. The method according to p. 1, characterized in that gamma radiation is carried out in the presence of air or in an inert environment. 8. The method according to p. 1, characterized in that as a wood filler using wood flour with an average particle size of from 180 to 560 microns. 9. The method according to p. 1, characterized in that the wood filler uses ground wood waste with particle sizes from 0.005 to 1 mm.

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