RU2703539C2 - Method of producing fire-resistant wood-polymer composites based on secondary polyolefins - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to production of highly filled fire-resistant wood-polymer composite materials used in construction, furniture industry, machine building and other industries. Method involves drying components of the composite, mixing and thermoforming by extrusion in an extrusion apparatus of the Co-Kneader type at processing temperature of 120 °C to 150 °C with a screw rotation speed of 350–450 rpm and subsequent granulation. Composite contains from 5.0 to 10.0 pts.wt of secondary polyolefin, from 29.5 to 38.5 pts.wt. of wood filler from 5.0 to 10.0 pts.wt. of flame retardant and synergetic nanosized additive and from 0.5 to 1.5 pts.wt. of process additive. Flame retardant and synergetic nanosized additive contains a phosphorus-containing flame retardant, an organically modified synthetic clay based on Mg-Al layered double hydroxides and nanosized zinc borate.

EFFECT: obtained fire-resistant DPC based on secondary polyolefins has high operational characteristics.

5 cl, 1 dwg, 17 tbl, 6 ex

Description

The invention relates to a technology for producing fire-resistant wood-polymer composite materials (WPC) and can be used in construction, automotive, shipbuilding, mechanical engineering, furniture and other industries.

A known method of obtaining fire-resistant duodenum (Patent CN No. 101851362, 2010). Fire-resistant WPC includes the following components in wt. %: 25-70 polyolefin resin, 5-50 plant fibers, 0.5-20 compotibilizer, 0-30 plasticizer, 0.5-8 dispersant, 5-40 flame retardant and senergetic additives, 0-1 antioxidant. WPC is produced in a one-step method for injection molding. The main disadvantages of this invention are the relatively low level of physico-mechanical properties and fire resistance, low manufacturability, limiting the technology of processing composites into products only by pressing and / or injection molding.

A patent is known for the production of fire-resistant WPC (Patent CN No. 100374493 C, 2008), the claimed composite contains in wt. %: 15-32 polyolefins or mixtures thereof; 5-70 natural fibers; 7-40 ammonium polyphosphate; 0-20 carbon agent; 3-10 foaming agent; 1-10 technological additives. The above components are mixed by extrusion and processed into finished products. The disadvantages of this invention are the discrepancy with the modern requirements of the fire resistance of the material, a large amount of flame retardant ammonium polyphosphate in the composition of the composite, which decomposes during processing and absorbs moisture.

A known method for producing highly filled WPC based on polyvinyl chloride (Patent RU 2527468, 2013). A method of obtaining a highly filled WPC consists in pretreating wood flour with an aqueous solution of a binder — silica sol, followed by thorough mixing and drying to constant weight at a temperature of 100 ± 2 ° C and further mixing of treated wood flour, PVC, a complex thermal stabilizer, and impact modifier. In this case, PVC is pretreated with a binding agent containing 0.1-2.5 weight. including silica sol, thoroughly mixed, dried to constant weight at a temperature of 60 ± 2 ° C, and wood flour is treated with a binder, containing 0.1-4.9 weight. including silica sol. The disadvantages of this invention are low rates of fire resistance, the use of PVC in the composition of composites, the combustion of which is accompanied by the release of toxic compounds and the complexity of the technological process for producing duodenum.

Closest to the technical nature of the achieved technical result is fire-resistant WPC based on polyolefins and the method for its production (Patent CN No. 102321374, 2012). Fire-resistant duodenum contains, in weight. including: 30-70 lignocellulosic material, 2-8 technological additives, 0.5-4 silane compounds, 20-50 polyolefins, 0.01 antioxidant, 8-30 nanometer inorganic flame retardants, 0-5 mineral fillers. Lignocellulosic material, processing aids, silane compounds and polyolefins are mixed in a high-speed mixer at a temperature of 40-120 ° C for 3-10 minutes, then the temperature is reduced to 40-60 ° C, antioxidants, nanosized flame retardants and mineral fillers are added, and then 5 more are mixed -20 minutes. Next, the resulting mixture goes through an extrusion stage (processing temperature - 140-190 ° C) on a twin-screw extruder and a granulation stage. The main disadvantages of the invention are the complexity of the technological design of the process of obtaining the duodenum and low fire resistance.

The technical result to which the claimed invention is directed is to obtain a flame retardant WPC based on secondary polyolefins with high performance characteristics and to simplify the process for its preparation.

The technical result is achieved by the fact that a method of obtaining a fire-resistant duodenum, which contains in weight. including components:

- secondary polyolefins 5.0-10.0,

- wood filler 29.5-38.5,

- flame retardants 5.0-10.0,

- technological additives 0.5-1.5,

includes drying of the components, their mixing and high-speed extrusion with the following parameters:

- temperature of processing zones - 120-150 ° C,

- screw rotation speed - 350-450 rpm.

A characteristic feature of the claimed technical solution is the presence in the composition of the composite secondary polyolefins, in particular, high density polyethylene, low density polyethylene, polypropylene and / or mixtures thereof. The secondary polyolefins included in the fire-resistant WPC in accordance with the present invention have a density of 0.89-0.96 g / cm ³ and a melt flow rate (MFR) (measured in accordance with GOST 11645-73, at a load of 2.16 kg, at 190 ° C) 4 -40 g / 10 min.

Sawdust or wood flour is used as a wood filler. The size of wood particles is about 60-80 mesh (the number of holes per linear inch), humidity is not more than 12%.

Below are the main components (except for the wood component), which are collectively flame retardant and synergistic additives.

Fire-resistant nanostructured synergistic additive (OSD):

Phosphorus flame retardants:

Exolit OP 1240 is an organic phosphinate.

PhosliteB85AX - metal phosphinate.

Nitrogen-containing flame retardants:

MelapurMC - Melamine cyanurate.

Melapur 200 - melamine polyphosphate.

Nanoscale flame retardants:

PerkaliteF 100 is an organically modified synthetic clay based on Mg-Al layered double hydroxides.

PerkaliteFR 100 is an organically modified flame retardant synthetic clay based on Mg-Al layered double hydroxides.

NZnB is nanoscale zinc borate.

As technological additives use:

Irganox 1010 is a phenolic type antioxidant. Manufacturer: Ciba, Switzerland.

Irgafos 168 is an antioxidant.

Lotader AX8900 is a copolymer of ethylene, acrylic ester and glycidyl methacrylate.

Polybond 1009 is a chemically modified polyolefin.

Acrawax C - N, N’-ethylenebis (stearamide).

Licowax E - lubricant for polymers.

Powersil Paste AP is a lubricant for polymers.

Obtaining WPC is carried out using a high-speed extrusion installation of the type Co-Kneader according to the technological scheme shown in figure 1.

1 - secondary polyolefins; 2 - a mixture of flame retardants and technological additives;

3 - the first zone of the extruder; 4 - the second zone of the extruder;

5 - the third zone of the extruder; 6 - the fourth zone of the extruder;

7 - melt pump; 8 - extruder head;

9 - granulator; 10 - granules of fire-resistant duodenum.

The principle of operation of the extruder is based on the reciprocating movement of the screw, which ensures high quality mixing of the feedstock. The extruder is specifically designed to produce polymer composites with a high content of fillers. The protrusions on the screw have gaps, which allows more efficient work with pins located in three rows on the cylinder walls. The interaction between the rotating slots and the fixed pins provides dispersion and distribution mixing at the same time.

Examples of the invention

Example 1. Take: secondary polyethylene - 5 kg, wood filler - 38.5 kg, organic phosphinate 2 kg, organically modified synthetic clay based on Mg-Al layered double hydroxides - 2 kg, nanosized zinc borate - 1 kg, irganox 1010 - 0.5 kg, maleized polyethylene - 0.5 kg, paraffin - 0.5 kg and pre-mixed mechanically, loaded into dispensers, then with constant stirring, the components are fed into the working area of the extruder. The temperature of zone processing is: in the first zone of the extruder 130 ° C, in the second zone - 140 ° C, in the third zone - 150 ° C, in the fourth - 120 ° C. The screw mixes and squeezes the melt through the filter mesh (die) into the forming head (strand head). The screw rotates at 450 rpm.

Examples 2-6 are similar to example 1, differ in different formulations of the composition of the duodenum.

Tables 14-16 show the compositions of the proposed wood-polymer composites, examples of production modes and the properties of wood-polymer composites by examples.

Thus, the claimed method for producing fire-resistant WPC combines high fire resistance corresponding to class B1, B2 according to GOST 30402-96, class G1, G2 according to GOST 30244-94, manufacturability, environmental safety and high operational properties. WPC materials based on secondary polymer raw materials correspond to the fire safety classes KM1, KM2 according to GOST 30403-96.

Claims (5)

1. A method of producing a wood-polymer composite, including drying the components of the composite, mixing and thermoforming by extrusion in a Co-Kneader type extrusion machine at a processing temperature of 120 ° C to 150 ° C with a screw speed of 350 to 450 rpm and subsequent granulation, while the composite contains from 5.0 to 10.0 parts by weight secondary polyolefin, from 29.5 to 38.5 parts by weight wood filler, from 5.0 to 10.0 parts by weight antipyretic and synergistic nanoscale additives and from 0.5 to 1.5 wt.h. technological additives, and the antipyrating and synergistic nanoscale additive includes a phosphorus-containing flame retardant, an organically modified synthetic clay based on Mg-Al layered double hydroxides and nanoscale zinc borate. 2. The method according to claim 1, characterized in that the secondary polyolefin is selected from the group comprising secondary polyethylene, secondary polypropylene, a copolymer of ethylene and polypropylene, or a mixture thereof. 3. The method according to p. 1, characterized in that as a wood filler using sawdust or wood flour having a moisture content of not more than 12% and a particle size of wood from 60 to 80 mesh. 4. The method according to claim 1, characterized in that organic phosphinate and / or metal phosphinate are used as the phosphorus-containing flame retardant, and the processing aid is selected from the group consisting of antioxidants, maleated polyethylene and paraffin, or mixtures thereof. 5. The method according to claim 1, characterized in that a nitrogen-containing flame retardant selected from the group consisting of melamine cyanurate, melamine polyphosphate or a mixture thereof is additionally added to the composition of the flame retardant and synergistic nanoscale additives.

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