Patent Application
20090174109
The invention relates to a composite material as claimed in the precharacterizing part of claim 1, to a process for its production as claimed in claim 14, and to its use as claimed in claim 18.
Various composite materials which comprise plastics and wood have been described.
For example, composite materials composed of wood and thermoplastics are known. EP 1172404 B1 describes composites composed of polypropylene, polyethylene, or polystyrene with content of from 20 to 80% by weight of wood fibers. The disadvantage of composite materials comprising thermoplastics is limited strength and toughness as a consequence of the low compatibility of the apolar polyolefins with the wood component.
Mixtures composed of melamine resins and wood particles have likewise been previously described. For example, JP 52 005 854 A2 describes the use of wood powder as filler in melamine molding compositions. Low flexibility due to the use of melamine resins is a disadvantage in composite materials.
The varying melting behavior and flow behavior of melamine resins also has an effect on the properties of composite materials which comprise melamine resins.
Addition of thermoplastics as lubricants is known for improving the viscosity and flexibility of composite materials using melamine resins.
For example, WO 2005/009701 describes a composite material composed of from 55 to 90% by weight of wood particles and from 45 to 10% by weight of crosslinked plastics, where the crosslinked plastics are either crosslinked melamine resin ethers composed of melamine resins etherified using alcohols (MER type) or composed of melamine resins transetherified using alcohols (MPER type), or are a mixture composed of partially crosslinked thermoplastics and of crosslinked melamine resin ethers. Examples of preferred partially crosslinked thermoplastics are partially crosslinked ethylene-vinyl acetate copolymers, and partially crosslinked polyethers and/or polyesters.
Addition of partially crosslinked thermoplastics can give a homogeneous melt of the composite material with good flow properties, the melt being suitable for thermoplastic processing, e.g. in extruders. However, a disadvantage for the use of this type of composite material is the poor mechanical properties of the admixed thermoplastics.
An object on which the invention is based is therefore to provide a composite material which has good flow behavior and good compactability between melamine resin and wood, but at the same time exhibits good mechanical properties.
A composite material with the features of claim 1 achieves this object.
The inventive composite material with a proportion of wood and a proportion of crosslinked melamine resins is characterized in that the crosslinked melamine resins are formed from melamine resins which in essence have linear structure and have shear-dependent viscosity.
The melamine resins which in essence have linear structure take the form of linear or weakly crosslinked chain molecules whose structure in essence corresponds to that of the melamine resins described in a parallel application (easy-flow melamine resins). These chain molecules can flow past one another if the temperature is sufficiently high, and this makes the resin fusible and makes its viscosity shear-rate-dependent. This property is also termed non-newtonian behavior. Since these resins have very good flow behavior in the melt phase, the wood particles can be homogeneously dispersed in the resin matrix in the inventive composite materials. It is no longer necessary to add partially crosslinked thermoplastics as lubricants. The inventive composite material features not only good thermoplastic processability but also improved mechanical properties.
The inventive composite material advantageously encompasses a proportion of wood of from 40 to 85% by weight, a proportion of crosslinked melamine resins of from 15 to 60% by weight, and a proportion of additives of from 0 to 20% by weight. The composite material preferably has from 50 to 80% by weight of wood, from 18 to 48% by weight of crosslinked melamine resins, and from 2 to 10% by weight of additives.
Advantageously, the molecular weights of the melamine resins which in essence have linear structure and have shear-dependent viscosity are from 1000 to 200 000.
The inventive composite material preferably comprises melamine resins synthesized from triazine rings of (B2N)b—X—(NHA)a type, where a+b=3 and 0≦b≦2, X is a triazine ring, and each of A and B is a —CH2OR group having a moiety R composed of any desired alkanol, diol, or polyol. Additives that can be used with advantage are uncrosslinked thermoplastics, lubricants, or further additives, such as flame retardants, pigments, stabilizers, catalysts, UV absorbers, and/or free-radical scavengers, individually, or a mixture of these.
The additive used preferably comprises a mixture composed of uncrosslinked thermoplastic and lubricant, where the amount of uncrosslinked thermoplastic is at most 20% by weight, based on the melamine resin in the composite material. This corresponds to thermoplastic content of at most 12% by weight, based on the composite material. At higher thermoplastics concentrations, based on the melamine resin, the thermoplastic functions as binder matrix. This means that the melamine resin becomes included by the thermoplastic, which determines the mechanical properties of the composite.
The additive used particularly preferably comprises a mixture composed of uncrosslinked thermoplastic and lubricant, the amount of additive being at most 5% by weight and the amount of uncrosslinked thermoplastic being at most 2% by weight, based in each case on the composite material.
In principle, a very wide variety of uncrosslinked thermoplastics can be used as additive. Uncrosslinked thermoplastics used in the composite material preferably comprise ethylene-vinyl acetate (EVA) or polycaprolactone.
The lubricants used preferably comprise hydrocarbon waxes, oxidized hydrocarbon waxes, zinc stearate, calcium stearate, magnesium stearate, or other metal soaps and/or mixtures composed of these.
The proportion of wood in the inventive composite advantageously takes the form of wood flour, wood particles, wood pellets, wood fibers, and/or wood shavings.
It is preferable that the inventive composite material comprises fillers of the type represented by melamine, urea, cellulose, urea-formaldehyde resins, melamine-formaldehyde resins, polyether polyols, and/or polyester polyols.
The inventive composite material preferably takes the form of a sheet, profile, or tube.
The object of the invention is also achieved via a process for production of a composite material as claimed in claim 1, and its use.
The inventive composite material with a proportion of wood and with a proportion of crosslinked melamine resins is produced by a process where the wood, the melamine resins which in essence have linear structure and have shear-dependent viscosity, and additives are melted, homogenized, and devolatilized at temperatures of about 90 to 170° C.,
Advantageously, the wood, the melamine resins in essence having linear structure and having shear-dependent viscosity, and additives are melted, homogenized, and devolatilized in an extruder, particularly preferably in a conical twin-screw extruder. It is also possible to use a mixer or compounder for the homogenization, melting, and devolatilizing process. The compression of the mixture takes place in the extruder.
It is preferable that the metering of wood, of melamine resins in essence having linear structure and having shear-dependent viscosity, and of additives into the extruder takes place in the form of the individual components or in the form of a flowable mixture prepared from the individual components.
The inventive composite materials are preferably used in windows, in doors, in cladding elements, and in roof elements in the outdoor sector, and also in the sports and leisure sector for garden furniture, and outdoor seating, and for design of childrens' play areas.
The invention is explained in more detail below with reference to a number of inventive examples and figures.
a and 1b: show transmission electron micrographs of a melamine-resin-thermoplastic mixture;
17.6 kg of spruce-wood shavings are compounded in a high-speed mixer with 4.1 kg of melamine resin ether, 0.54 kg of polycaprolactone, and 3% by weight of Naftosafe PHX 369D (CHEMSON), based on the total amount, for 8 min at 90° C.
The melamine resin ethers here are prepared on the basis of an MER (M:F=1:4), these being transetherified using 30% by weight of SIMULSOL® BPPE polyester polyol (Seppic) and compounded using 50% by weight of MER (M:F=1:2.5). The Mw of the melamine resin ethers is ˜8000 g/mol and they have shear-dependent viscosity of 45 Pa*s, measured at 130° C.
A further 4.1 kg of this melamine resin ether are then metered into the premix, and the mixture is mixed for a further 4 min. In the subsequent cooling mixer, this mixture is cooled to about 40° C. and finished.
35 kg/h of the premix prepared in 1.1 is metered into the feed hopper of a Fiberex T58 Cincinnati extruder with conical twin screw, vacuum devolatilization and a sheet die (4.6×160 mm), and melted at 130° C. This material is then homogenized and hardened using a temperature profile of 130/130/130/110/110/110///125/225/225/225° C. in the extruder and the die.
The density of test specimens milled from the extruded wood-melamine-resin composites is 1.32 g/cm3 and their flexural modulus is 72 N/mm2.
16.2 kg of spruce-wood shavings are sintered in a high-speed mixer with 4.7 kg of melamine resin ether, 1.35 kg of polycaprolactone, and 3% by weight of Naftosafe PHX 369D (CHEMSON), based on the total amount, for 9 min at 95° C.
The melamine resin ethers here are prepared on the basis of an MER (M:F=1:4), these being transetherified using 30% by weight of DESMOPHEN 800 polyester polyol (Bayer) and compounded using 50% by weight of MER (M:F=1:2.5). The Mw of the melamine resin ethers is ˜15 000 g/mol and they have shear-dependent viscosity of 90 Pa*s, measured at 130° C.
A further 4.0 kg of this melamine resin ether are then metered into the mixture and the mixture is mixed for a further 6 min. In the subsequent cooling mixer, this mixture is cooled to about 50° C. and finished.
75 kg/h of the premix prepared in 2.1 is metered into the feed hopper of a Fiberex T58 Cincinnati extruder with conical twin screw, vacuum devolatilization and a sheet die (4.6×160 mm), and melted at 125° C. This material is then homogenized and hardened using a temperature profile of 125/125/125/120/120/120///125/225/225/225° C. in the extruder and the die.
The density of test specimens milled from the extruded wood-melamine-resin composites is 1.29 g/cm3 and their flexural modulus is 55 N/mm2.
16.2 kg of spruce-wood shavings are sintered in a high-speed mixer with 6.0 kg of melamine resin ether, 1.5% by weight of Naftosafe PHX 369D, and 1.5% by weight of Naftosafe PHX 369D20 (both CHEMSON), in each case based on the total amount, for 9 min at 105° C.
The melamine ethers here are prepared on the basis of an MER (M:F=1:3), these being transetherified using 15% by weight of CAPA 3091 polyester polyol (SOLVAY). The Mw of the melamine resin ethers is ˜10 500 g/mol and they have shear-dependent viscosity of 60 Pa*s, measured at 130° C.
A further 4.0 kg of this melamine resin ether are then metered into the mixture and the mixture is mixed for a further 6 min. In the subsequent cooling mixer, this mixture is cooled to about 50° C. and finished.
55 kg/h of the premix prepared in 3.1 is metered into the feed hopper of a Fiberex T58 Cincinnati extruder with conical twin screw, vacuum devolatilization and a sheet die (4.6×160 mm), and melted at 110° C. This material is then homogenized and hardened using a temperature profile of 110/110/110/110/110/110///125/235/235/235° C. in the extruder and the die.
The density of test specimens milled from the extruded wood-melamine-resin composites is 1.34 g/cm3 and their flexural modulus is 68 N/mm2.
18.9 kg of beech-wood shavings are sintered in a high-speed mixer with 0.54 kg of polycaprolactone and 3% by weight of magnesium stearate, based on the total amount, for 8 min at 97° C. 6.75 kg of melamine resin ether are then metered in and the mixture is mixed for a further 5 min.
The melamine ethers here are prepared on the basis of an MER (M:F=1:3.5), these being transetherified using 15% by weight of PEG 1000 polyether polyol. The Mw of the melamine resin ethers is ˜12 000 g/mol and they have shear-dependent viscosity of 73 Pa*s, measured at 130° C.
In the subsequent cooling mixer, the wood-melamine premix is cooled to about 45° C. and finished.
70 kg/h of the premix prepared in 4.1 is metered into the feed hopper of a DS 13.27 Weber extruder with parallel twin screw, vacuum devolatilization and a sheet die (4.6×160 mm), and melted at 125° C. This material is then homogenized at a temperature of 125° C. throughout the extruder and hardened in the die at 240° C.
The density of test specimens milled from the extruded wood-melamine-resin composites is 1.25 g/cm3 and their flexural modulus is 59 N/mm2.
12.2 kg of mixed-wood shavings are sintered in a high-speed mixer with 7 kg of a melamine resin ether and 3% by weight of Naftosafe THX 369D, based on the total amount, for 8.5 min at 103° C.
The melamine ethers used here are prepared on the basis of an MER (M:F=1:4), these being transetherified using 15% by weight of butanediol. The Mw of the melamine resin ethers is ˜8000 g/mol and they have shear-dependent viscosity of 50 Pa*s, measured at 130° C.
A further 7 kg of the melamine resin ethers are then metered into the premix, and the mixture is mixed for a further 6 min. In the subsequent cooling mixer, this mixture is cooled to about 50° C. and finished.
50 kg/h of the premix prepared in 5.1 is metered into the feed hopper of a Cincinnati Proton-25 B extruder with vacuum devolatilization and a sheet die (4.6×160 mm), and melted at 120° C. This material is then homogenized at a temperature of 120° C. throughout the extruder and hardened in the die at 230° C.
The density of test specimens milled from the extruded wood-melamine-resin composites is 1.27 g/cm3 and their flexural modulus is 63 N/mm2.
40 kg/h of the following individual components:
The melamine resin ethers here are prepared on the basis of an MER (M:F=1:4), these being transetherified using 30% by weight of SIMULSOL® BPPE polyester polyol (Seppic) and using 50% by weight of MER (M:F=1:2.5). The Mw of the melamine resin ethers is ˜8000 g/mol and they have shear-dependent viscosity of 45 Pa*s, measured at 130° C.
This material is then homogenized and hardened using a temperature profile of 135/135/120/110/110/-110////125/225/225/225° C. in the extruder and the die.
The density of test specimens milled from the extruded wood-melamine-resin composites is 1.29 g/cm3 and their flexural modulus is 62 N/mm2.
a and 1b show transmission electron micrographs of a melamine resin/thermoplastics mixture prepared using CAPA® 6400 thermoplastic (Solvay), using 3900-times magnification.
a is the micrograph of a melamine resin/thermo-plastics mixture (CAPA® 6400, polycaprolactone, Solvay), where about 33% by weight of CAPA® 6400 were admixed. That corresponds to an MPER:CAPA® 6400 ratio of 2:1. It is clearly seen that CAPA® 6400 (dark regions, lamellar structure) forms the matrix and that melamine resin has been embedded therein (white regions). The melamine resin has therefore been included by the thermoplastic. A consequence of this is that the mechanical and thermal properties of the composite are determined by the thermoplastic, i.e. the composite is characterized by the poor mechanical properties, undesirable here, of the thermoplastics.
b shows the micrograph of a melamine resin/thermo-plastics mixture using about 17% by weight of CAPA® 6400 and using an MPER:CAPA® ratio of 5:1. The phase inversion is clearly discernible, and this means that here the melamine resin forms the matrix and the thermoplastic has been embedded in the melamine resin (CAPA® 6400; dark circles, lamellar structure). The mechanical properties of the composite are therefore determined by the mechanical properties of the melamine resins, and the composite material therefore has improved hardness and strength.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 029 685.8 | Jun 2005 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/006186 | 6/19/2006 | WO | 00 | 2/11/2009 |
