A COMPOSITE MATERIAL AND COMPOSITE PRODUCT

Abstract

The present invention is directed to a composite material comprising a cellulosic material, high impact polystyrene (HIPS) and styrene maleic anhydride (SMA). The cellulosic material may be thermally modified prior to being incorporated into the composite material. The present invention is also directed to a composite product that comprises the composite material according to the invention.

Claims

1. A composite material comprising at least 20% by weight of a cellulosic material, at least 1% by weight and less than 20% by weight of styrene maleic anhydride and from 5% to 50% by weight of a high impact polystyrene.

2. The composite material according to claim 1, wherein the cellulosic material is a thermally modified cellulose material.

3. The composite material according to claim 2 wherein the cellulosic material has been thermally modified by heat treatment at a temperature between 160-250 C.

4. The composite material according to claim 1, wherein the composite material from 2% to 15% by weight of styrene maleic anhydride.

5. The composite material according to claim 4, wherein the composite material from 5% to 10% by weight of styrene maleic anhydride.

6. The composite material according to claim 1, comprising 25-75% by weight of a cellulosic material.

7. The composite material according to claim 6, comprising 40-65% by weight of a cellulosic material.

8. The composite material according to claim 7, comprising 45-65% by weight of a cellulosic material.

9. The composite material according to claim 8, comprising 50-60% by weight of a cellulosic material.

10. The composite material according to claim 1, comprising 35-50% by weight high impact polystyrene.

11. The composite material according to claim 1, wherein the cellulosic material has a particle size below 1 mm.

12. The composite material according to claim 1, wherein the cellulosic material is in the form of a powder.

13. A composite product comprising a composite material according to claim 1.

14. (canceled)

15. Process for producing a composite product which process comprises the steps of: a) providing a cellulosic material, high impact polystyrene (HIPS) and styrene maleic anhydride (SMA); b) feeding said cellulosic material, HIPS and SMA to an extruder; and c) extruding the composite product.

16. The composite material according to claim 2 wherein the cellulosic material has been thermally modified by heat treatment at a temperature between 200-230 C. at atmospheric pressure.

17. The composite material according to claim 2 wherein the cellulosic material has been thermally modified by heat treatment at a temperature above 120 C. at elevated pressure.

Description

DETAILED DESCRIPTION

[0028] The present invention relates to a composite material comprising cellulosic material, high impact polystyrene (HIPS) and styrene maleic anhydride (SMA). It has surprisingly been found that the composite material according to the present invention provides enhanced strength and stiffness properties.

[0029] The process ability of the composite material according to the present invention is suitable for high strength composite profiles for applications such as windows and doors and heavier infrastructure applications where normal wood-polymer composites and plastics are not suitable.

[0030] The improved strength and stability observed is enhanced by an esterification reaction between the cellulosic material and matrix components. In one embodiment of the present invention, the gravimetric density of the composite material and composite product is higher than 1.0 g/cm.sup.3, such as higher than 1.3 g/cm.sup.3.

[0031] Furthermore, by using thermally modified cellulosic material in the composite, it has been found that a composite having particularly advantageous strength properties is achieved.

[0032] With thermally modified cellulosic material, it is meant that the cellulosic material has been thermally treated at an increased temperature between 160-250 C. at atmospheric pressure or at a temperature above 120 C. at an elevated pressure of above 1 bar. The cellulosic material can be thermally treated cellulosic fibers of any kind of cellulosic wood material. The thermally modified cellulosic fibers may be further treated to form said thermally modified cellulosic material, e.g. mechanically treated and/or chemically treated. The mechanical treatment of the thermally treated cellulosic fibers may be done to form a powder and one of the advantages with mechanically treating thermally modified cellulosic fibers are that they easily break into very small particles with unique shape. Size and shape are key parameters influencing numerous composite properties, such as strength and water uptake. Because of the very fine particle size and lack of resin compared to what is found in normal dried wood the risk of fiber bundling is greatly reduced when adding the thermally modified cellulosic material to the polymer to form the composite material, which in turn leads to more even dispersion and distribution. Chemical treatment of the thermally treated cellulosic fibers may be done to improve the reactivity of the material. It may also be possible to thermally treat cellulosic fibers that have been mechanically or chemically treated, e.g. to thermally treat cellulosic fiber that have been ground into a powder.

[0033] The composite material may also comprise additives that will enhance the performance and process parameters of the composite. Possible additives may be lubricants, coupling agents, pigments, uv-stabilizers or blockers and/or fillers. In one embodiment of the present invention, the composite material comprises a flame retardant.

[0034] The present invention also relates to a process for producing a composite product which process comprises using an extruder to manufacture the composite product. It is possible to use any kind of extruder.

[0035] The composite material according to the present invention may for example be produced in the form of pellets or granules, using a compounding extruder. Such pellets or granules can be used to manufacture a composite product comprising the composite material. Such composite products can for example be manufactured by extrusion, injection moulding, rota moulding, 3D printing or form pressing. The composite material may also be produced in the form of a shaped composite product, for example by providing a profile die through which a shaped composite product is extruded. Such profiled composite products may be produced in variety of shapes and for multiple purposes.

[0036] The produced composite product can be used for the production of many different products, such as cladding, decking, window and door profiles, light poles, jetties, joinery, furniture etc. The produced composite products may be used for applications such as interior and exterior decorative house moldings, picture frames, furniture, porch decks, deck railings, window moldings, window components, door components, roofing structures, building siding and cladding, and other suitable indoor and outdoor components. The composite material and composite products according to the present invention may also be useful in shoring as well as in marine environments such as submerged structures. Furthermore, cellulosic/polymer composites according to the present invention may replace highly durable and scarce hardwood, e.g. tropical hardwood.

EXAMPLES

[0037] Abbreviations:

SMA: styrene maleic anhydride (Xiran from Polyscope)
TW: thermally modified cellulosic material
HIPS: high impact polystyrene
MOE: modulus of elasticity
STD: standard deviation
WPC: wood-polymer composite
Avg: average
COV: coefficient of variance

Example 1

[0038] In this experiment, the mechanical properties of composite products comprising a composite material according to the present invention were investigated.

[0039] Thermally modified wood (HTW) fibers were used. The fibers were shavings from pine that had been thermally modified by heating to 212 C. for 3 hours and subsequently ground in a hammer mill and passed through a screen.

[0040] The following formulations where prepared:

TABLE-US-00001 TABLE 1 Formulations of samples, % by weight. Content of cellulosic Sample material SMA content HIPS content Control-pine Pine 50% 0% .sup.50% SMA-0% TW 50% 0% .sup.50% SMA-2.5% TW 50% 2.5% 47.5% SMA-5.0% TW 50% 5.0% 45.0% SMA-7.5% TW 50% 7.5% 42.5% SMA-10.0% TW 50% 10.0% 40.0% SMA-12.5% TW 50% 12.5% 37.5% SMA-15.0% TW 50% 15.0% 35.0%

[0041] The specifications of the pilot extrusion system were as follows: with the following process parameters used in the extruder:

TABLE-US-00002 TABLE 2 Extrusion parameters, Woodtruder equipment. The cellulosic fibers were direct fed to the twin screw and the SMA was added via the single screw. Decking board composite products were produced. Die part WT 94 Twin-screw extruder Die 3 Die 2 Die 1 Clamp Zone8 Zone7 Zone6 Zone5 Zone4 Zone3 Zone2 Zone1 RPM Melt P. Melt T. 200 200 200 210 200 190 190 185 180 180 170 165 37 psi 193 Output rate Vacuum T75 Single-screw extruder Lbs/hr inches Hg Clamp Adapt Zone5 Zone4 Zone3 Zone2 Zone1 RPM Melt P. Melt T. 72~75 30 inch 210 210 210 200 195 190 185 17 psi 205

[0042] The flexural properties (flexural strength and flexural modulus) were determined for the samples:

TABLE-US-00003 TABLE 3 Flexural properties of samples and control/comparative samples. Strength MOE Average, Average, Sample MPa STD MPa STD Control-pine 31.07 1.36 4688 425 SMA-0% 31.26 1.17 5849 170 SMA-2.5% 45.71 3.26 6888 268 SMA-5% 49.82 1.80 6865 237 SMA-7.5% 50.26 1.80 6431 237 SMA-10% 50.29 1.99 6110 328 SMA-12.5% 49.85 2.86 5660 083 SMA-15% 49.01 2.14 5531 117 Foamed 24.82 3534 SMA-WPC* Commercially 19.99 1379 available WPC** *data from decking board samples made of NovaChem SMA and pine wood; wood content 30% and specific gravity was 0.85 **commercially available product (polypropylene/polyethylene and 50% by weight of normal sawdust); data from technical data sheet of commercially available WPC

Example 2

[0043] The dimensional stability of the samples was determined.

[0044] The samples were first conditioned at room temperature and then immersed into water for a total of 28 days. The dimensional measurements were conducted at 24 hours. 7 days, 14 days, 21 days and 28 days for the water absorption and dimensional changes of width, length and thickness.

TABLE-US-00004 TABLE 4 Weight gain percentage of the samples soaked in water. 24 hours 7 days 14 days 21 days 28 days Sample Avg COV Avg COV Avg COV Avg COV Avg COV SMA 0% 0.085 4.47 0.525 2.38 0.822 2.16 1.131 3.54 1.222 3.07 SMA 2.5% 0.056 33.81 0.472 25.59 0.705 18.27 0.936 15.67 0.991 10.6 SMA 5% 0.049 36.39 0.381 16.89 0.613 13.91 0.817 3.35 0.884 9.62 SMA 7.5% 0.044 6.57 0.336 3.13 0.567 3.28 0.793 3.05 0.847 3.01 SMA 10% 0.051 11.07 0.363 8.16 0.568 8.71 0.799 6.12 0.884 7.23 SMA 12.5% 0.055 12.77 0.363 3.47 0.572 2.68 0.811 2.27 0.886 1.62 SMA 15% 0.058 8.70 0.355 1.63 0.603 2.09 0.818 1.83 0.888 1.08 Control-pine 0.300 13.39 1.385 8.59 2.028 7.80 2.646 7.49 2.817 7.61

TABLE-US-00005 TABLE 5 Dimensional change (thickness swelling), percentage, samples soaked in water. 24 hours 7 days 14 days Sample Avg COV Avg COV Avg COV SMA 0% 0.510 12.420 0.742 15.270 0.888 2.080 SMA 2.5% 0.474 19.440 0.612 17.780 0.668 15.610 SMA 5% 0.523 9.750 0.650 13.840 0.706 12.110 SMA 7.5% 0.531 8.470 0.617 9.440 0.690 9.740 SMA 10% 0.479 17.580 0.563 18.340 0.650 14.190 SMA 12.5% 0.420 18.240 0.540 9.840 0.612 7.820 SMA 15% 0.392 10.300 0.532 8.750 0.616 8.410 Control-pine 1.011 6.460 1.518 6.550 1.836 6.680 21 days 28 days Sample Avg COV Avg COV SMA 0% 0.955 9.050 1.041 6.86 SMA 2.5% 0.685 16.800 0.769 21.43 SMA 5% 0.770 13.680 0.809 13.13 SMA 7.5% 0.748 10.750 0.750 10.63 SMA 10% 0.712 12.770 0.768 13.62 SMA 12.5% 0.689 8.090 0.730 7.31 SMA 15% 0.680 9.500 0.728 7.38 Control-pine 2.150 8.440 2.245 8.23

[0045] It was found that the samples with thermally modified cellulosic material had less water absorption (weight gain) and dimensional changes compared to the sample made with regular pine.

[0046] The content of SMA significantly affected the water absorption (weight gain) and dimensional changes of the sample.

Example 3

[0047] The coefficient of thermal expansion (GTE) was determined in accordance with ASTM Standard D 696 and compared to other conventional plastic and composite products. The GTE is measured for two directions, lengthwise (extrusion direction) and widthwise (cross direction to the extrusion).

TABLE-US-00006 TABLE 6 CTE values of the samples CTE Sample Avg STD COV Control-pine-length 2.76E05 5.16E06 18.71 Control-pine-width 6.96E05 2.23E07 0.32 SMA-0%-length 4.86E05 3.65E06 7.51 SMA-0%-width 6.94E05 3.07E06 4.42 SMA-2.5%-length 2.40E05 2.13E06 8.88 SMA-2.5%-width 6.62E05 2.16E06 3.26 SMA-5.0%-length 2.51E05 2.61E06 10.42 SMA-5.0%-width 6.68E05 7.61E07 1.14 SMA-7.5%-length 2.30E05 9.67E08 0.42 SMA-7.5%-width 6.65E05 1.32E06 1.98 SMA-10%-length 2.29E05 5.74E07 2.51 SMA-10%-width 6.72E05 4.77E07 0.71 SMA-12.5%-length 2.02E05 2.16E07 1.07 SMA-12.5%-width 6.47E05 1.15E06 1.77 SMA-15%-length 2.07E05 1.75E06 8.47 SMA-15%-width 6.46E05 3.48E06 5.39 PVC profile* 5.0E05 Commercially available WPC** 2.0E05 *the CTE value of the PVC profiles is assumed being lengthwise expansion unless the manufacturers mention the expansion direction. **the CTE value of a commercially available WPC is assumed to be lengthwise expansion

[0048] It was found that the samples according to the present invention showed coefficient of thermal expansion similar to commercially available WPC and about 50% of a PVC profile which is a major advantage.

[0049] It was found that the CTE for extrusion (lengthwise) direction is much less than cross (widthwise) direction.

[0050] It was found that the samples with thermally modified cellulosic material showed lower CTE values than with the normal pine.

[0051] It was found that the content of SMA contributed to lower CTE of the samples.

Example 4

[0052] A study was carried out to estimate the feasibility of painting on the surfaces of composite products according to the present invention.

[0053] The following samples were prepared (weight-%):

TABLE-US-00007 Sample Description Note HIPS-TW-WPC-SMA 2.5% HIPS 47.5% with TW Cut from decking 50%/SMA 2.5% boards HIPS-TW-WPC-SMA 5.0% HIPS 45% with TW Cut from decking 50%/SMA 5.0% boards HIPS-TW-WPC-SMA 10% HIPS 40% with TW Cut from decking 50%/SMA 10% boards HIPS-TW-WPC-SMA 15% HIPS 35% with TW Cut from decking 50%/SMA 15% boards SMA: styrene maleic anhydride (Xiran from Polyscope) TW: thermally modified cellulosic material (*) HIPS: high impact polystyrene (*)_The fibers were shavings from pine that had been thermally modified by heating to 212 C. for 3 hours and subsequently ground in a hammer mill and passed through a screen.

[0054] The painting/coating conditions were as follows:

TABLE-US-00008 Paint brand NuCoat water-based Paint product name Super anti-heat Signal Black & Bar Red Surface preparation Scrubbed with Scotch Brite and wiped down with Zowo-Plast 1120 or used as supplied Spray rate Spray booth 75 with 1.8 nozzle size Spray pressure 55 psi Room condition Room temperature under RH 39% Cure temperature 90.5 F. with RH 21% Cure time 24 hours

[0055] Test method: ASTM D4541, Standard test method for pull-off strength of coatings using portable adhesion testers, was used. The portable adhesion tester was a pull-off tester, Model PosiTest AT-M from DeFelsko.

[0056] The following results were obtained:

TABLE-US-00009 Sample Average pull-off stress HIPS-TW-WPC-SMA 2.5% 237 psi HIPS-TW-WPC-SMA 5.0% 312 psi HIPS-TW-WPC-SMA 10% 335 psi HIPS-TW-WPC-SMA 15% 373 psi

[0057] The pull-off test was conducted on the hard surfaces with and without treatment to evaluate the topological properties of the sample surfaces. The surface treatment was conducted by scrubbing the surface using Scotch Brite sponges and wiped down with Zowo-Plast 1120, a water-based/biodegradable cleaning agent for cleaning and preparing prior to coating.

[0058] The following results were obtained for the treated surfaces:

TABLE-US-00010 Sample Average pull-off stress HIPS-TW-WPC-SMA 2.5% 555 psi HIPS-TW-WPC-SMA 5.0% 463 psi HIPS-TW-WPC-SMA 10% 677 psi HIPS-TW-WPC-SMA 15% 646 psi

[0059] The pull-off stress of all samples are very high which represents the painting-ability of the composite products according to the present invention. As shown above, the SMA content and the surface treatment affect the bonding strength.

[0060] In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art. However, it should be apparent that such other modifications and variations may be effected without departing from the spirit and scope of the invention.