IE903558A1

IE903558A1 - Shaped articles of substances containing wood or cellulose¹and processes for their production

Info

Publication number: IE903558A1
Application number: IE355890A
Authority: IE
Original assignee: Peter Pelz
Priority date: 1989-10-05
Filing date: 1990-10-04
Publication date: 1991-04-10
Also published as: CS276387B6; CS479290A3; PL287174A1; WO1991005020A1; DE3933279C1

Abstract

Moulded items like chipboard, fibreboard, mouldings and the like consist of a mixture of 0 to 95 % wt. of chips of wood or cellulose-containing substances; 5 to 100 % wt. of potato pulp with a moisture content of 5 to 95 % wt.; and 1 to 15 % wt. of a binder related to the total weight of the chip and potato pulp mixture. The moulded items have good physical and technological properties.

Description

The present invention relates to shaped articles of substances containing wood or cellulose and a process for their production. The shaped articles are, for example, chipboards, fibre boards, pressed mouldings and the like.

Chipboards are produced from wood shavings and other waste wood, binders being added to bind the wood shavings. The amount of binders is in general about 3 to 15% by weight, based on the absolutely dry wood. It depends inter alia on the nature of the binder and is, for example, about 3 to 5% by weight in the case of isocyanates and about 9 to 13% by weight in the case of formaldehyde resins, based on the absolutely dry wood. The quality of the chipboard depends decisively on the amount of binder employed. If attempts are made to reduce the amount of binder employed, for example for reasons of cost, chipboards which are of low quality, have inadequate physical properties, for example inadequate swelling properties, and display an inadequate dimen20 sional stability, such as, for example, transverse tensile strength and flexural strength, are in general obtained.

Potato pulp is obtained in large quantities as a waste product in the production of potato starch. It has so far been possible to use it only in small amounts as a feedstuff. For this purpose, the potato pulp is either delivered in unchanged form, in which case it rapidly undergoes microbial changes because of its high moisture content of about 90%, or it is dried, to give a product having a moisture content of about 10 to 75% by weight.

Industrial utilization of this product has so far been unsuccessful.

The object of the present invention is to provide a shaped article of substances containing wood or cellu35 lose in which all or some of the content of shavings containing wood or cellulose has been replaced by potato pulp.

This object is achieved by a shaped article according to Patent Claim 1. The subclaims relate to IE 90355« - 3 . preferred embodiments of the invention.

The use of potato pulp instead of wood shavings or the partial replacement of wood shavings by potato pulp considerably improves the physical properties, such as, for example, the swelling properties, the wet strength, the transverse tensile strength and the flexural strength, of chipboards, it being possible for the content of binder to be decreased at the same time. If potato pulp is added and, for example, isocyanates are used as the binder, the DIN values for the swelling time and the transverse tensile strength are improved many times over in comparison with the use of wood shavings alone.

The shaped articles according to the invention in general contain 5 to 100% by weight of potato pulp, preferably 25 to 75% by weight and particularly preferably 30 to 50% by weight. At such contents of potato pulp, the content of binders can be reduced to about 1 to 5% by weight, preferably to about 1 to 3% by weight and particularly preferably to about 2% by weight, for example if isocyanates are used, depending on the requirements of the shaped articles in respect of dimensional stability.

A product having a moisture content of about 5 to 95% by weight, preferably about 5 to 50% by weight, can be used as the potato pulp. At higher moisture contents of more than 90% by weight, in particular more than 95% by weight, pressing of the shaped articles becomes more difficult and the presses must have a possibility for drainage of the water pressed off.

Suitable binders are all the binders usually employed for the production of shaped articles of substances containing wood or cellulose, such as, for example, isocyanate (polyurethane) resins, urea-formalde35 hyde resins, melamine-formaldehyde resins, phenol-formaldehyde resins, tannins, binders prepared from microorganisms, such as described, for example, in DE-PS 3,621,218, and the like.

If wood shavings are used for the shaped articles IE 90355» - 4 according to the invention, the shavings usually employed for this purpose are used. In the production of, for example, chipboards, wood shavings which have approximately the following average dimensions are used for the middle layer: length 10 to 40 mm, width 3 to 17 mm and thickness 0.1 to 0.4 mm. Such shavings are generally called middle layer shavings. Shavings which have approximately the following average dimensions are used for the covering layers: length 0.1 to 0.7 mm, width 0.05 to 0.2 mm and thickness 0.01 to 0.2 mm. Such shavings are generally called covering layer shavings.

In the production of chipboards it has proved advantageous to add a hydrophobisizing agent to improve the resistance to swelling. The hydrophobisizing agent used is in general an aqueous paraffin emulsion, for example a 50% strength aqueous paraffin emulsion, which is used, in particular, if isocyanates are employed, or an emulsion of 49.6% of paraffin, 49.6% of water and 0.8% of 25% strength ammonia, for example if urea-formaldehyde resins are used.

About 0.5 to 2% by weight of the emulsion of such a hydrophobisizing agent, based on the absolutely dry wood or mixture of wood and pulp (dry matter) is employed.

The shaped articles according to the invention, in particular chipboards, can be produced as follows: If shavings are also used, the potato pulp is mixed with these and the mixture is then mixed with the binder or with a mixture of binder and other additives in a sizing drum, for example by the rotating process, or is sprayed with the binder. To produce chipboards, the sized shavings are sprinkled to form mats and these are pressed.

After about two days, the boards can be squared, abraded and tested for their physical-technological properties.

The invention is illustrated in more detail below with the aid of the examples. The middle layer shavings and covering layer shavings described above are used in - 5 IE 903558 the examples .

Example 1 Middle layer shavings and covering layer shavings having an average moisture content of about 3% together with potato pulp and binder were used to produce chipboards. The binders were mixed and homogenized with a stirrer, with the addition of a hydrophobisizing emulsion consisting of a 50% strength aqueous paraffin emulsion. Sliced-pine shavings were mixed with potato pulp in a laboratory sizing drum by the rotating process and the mixture was sprayed with binder.

To produce single-layered and three-layered chipboards (theoretical thickness 20 mm), the sized shavings were sprinkled manually to form mats 30 x 50 cm in size. Pressed mouldings were pressed from these at a temperature of 190°C under a pressure of 30 kp/cmz for a pressing time of 5 minutes. The boards were removed from the press and cooled in air. After two days, the boards were squared, abraded and investigated for their proper20 ties. Before the investigations, the boards were acclimatized for two days at 20°C and a relative atmospheric humidity of 65%.

The amounts of potato pulp, shavings and binder employed and the results obtained are shown in the following tables.

Table 1 Comparison experiment: single-layered board 2000 g of medium layer shavings sized with 2% by weight of Desmodur, water-emulsifiable diphenylmethane 4,4'-diisocyanate (PMDI), based on the absolutely dry shavings Thickness Bulk density Transverse tensile strength Swelling in thickness mm kg/m3 N/mm2 2 h 24 h 18.50 727 0.53 7.1 22.5 18.60 706 0.42 6.1 23.5 18.70 732 0.31 5.1 25.2 IE 90355b - 6 Covering layers : 500 g of 500 g of 500 g of 500 g of PMDI + 2.

Table 2 Three-layered board Middle layer: 500 g of middle layer shavings pulp, ground and dried, 10% moisture content covering layer shavings pulp as above sized with 2% of PMDI + 2.0% hydrophobisizing emulsion Thickness 19.0 19.0 Swelling in thickness 3.30 13.5 2.81 14.0 Bulk density Transverse tensile strength 669 0.40 651 0.71 Three-layered board Middle layer: 1000 g of middle layer shavings Covering layers: 500 g of covering layer shavings 500 g of pulp as above Binder and emulsion as above Thickness Bulk density Transverse tensile strength mm kg/m3 N/mm2 19.60 634 Swelling in thickness h 11.8 11.4 7.5 h 4.4 3.9 2.7 .10 .30 661 540 The boards (pulp 30% moisture content) produced using potato pulp have considerably better values of the transverse tensile strength and swelling in thickness than boards without potato pulp.

Example 2 Production of the chipboards as in Example 1. Instead of PMDI, the following binder was used: 7.5% by weight of 66.5% strength by weight aqueous urea-formaldehyde resin emulsion, molar ratio of urea:formaldehyde 1:1.3; + 0.5% by weight of 65% strength hydrophobisizing emulsion, + 1.5% by weight of (NH4)2SO4, a 15% strength aqueous solution as a hardener.

Table 3: Comparison experiment Single-layered board 2000 g of middle layer shavings IE 90355» _ 7 Binder: see above Thickness Bulk density Transverse Swelling in tensile strength thickness mm kg/m3 N/mm2 2 h 24 h 5 19.00 724 0.82 7.3 21.6 18.60 723 0.89 8.0 23.9 18.80 719 0.84 8.7 21.2 Table 4 Single-layered board Binder as in Table 3; 7.5%, based on the wood, pressing time of 5 minutes 1500 g of middle layer shavings 500 g of pulp, dried and ground absolutely dry Thickness Bulk density Transverse Swelling in 15 tensile strength thickness 18.60 723 0.88 8.0 24.9 18.00 721 0.91 6.3 27.4 18.40 760 0.92 7.5 27.5 Binder and the like as above 20 1000 g of middle layer shavings 1000 g of pulp, dried and ground Thickness Bulk density Transverse Swelling in tensile strength thickness 18.70 756 0.84 6.2 27.0 25 18.40 741 0.92 6.8 29.1 18.30 65 0.97 6.3 30.9 Example ! 3 Binder: urea-formaldehyde resin as in Example 2, 7.4% of solid resin, based on the absolutely dry wood 2000 g of middle layer shavings (comparison experiment) Pressing time of 5 minutes Table 5 Thickness Bulk density Transverse tensile strength Swelling in thickness mm kg/m3 N/mm2 2 h 24 18.4 736 0.89 6.8 22, 18.3 764 0.95 6.7 23, 18.6 756 0.99 7.2 21, Average 752 0.94 6.9 22, Table 6 Binder and the like as above 1500 g of middle layer shavings 500 g of pulp, dried and ground Thickness Bulk density Transverse Swelling in tensile strength thickness 18.99 729 0.91 8.4 21.9 18.60 720 0.97 8.1 23.9 18.60 658 0.82 5.5 22.1 10 1000 g of middle layer shavings 1000 g of pulp, dried and ground 18.50 783 1.01 6.2 25.6 18.10 801 1.02 5.7 27.6 18.00 768 1.00 5.1 22.5 When shavings are replaced by potato pulp, the properties in respect of transverse tensile strength and swelling in thickness are essentially retained without deterioration.

IE 90355» - 9 Shaped articles of substances containing wood or cellulose and processes for their production

Claims

Patent claims 1. To 15% by weight of binder, based on the total weight of the mixture of shavings and potato pulp.

1. Shaped article of substances containing wood or cellulose, consisting of a mixture of: 0 to 95% by weight of shavings of substances containing wood or cellulose and

2. Shaped article according to Claim 1, characterized in that the moisture content of the potato pulp is 5 to 50% by weight.

3. Shaped article according to Claim 1, characterized in that it contains 30 to 50% by weight of potato pulp having a moisture content of 30 to 50% by weight and 1 to 8% by weight of binder.

4. 4 . Shaped article according to Claim 1, charac- terized in that it contains about 2% by weight of iso- cyanate as the binder. 5. Shaped article according to Claim 1, charac- terized in that it contains isocyanate, urea-formaldehyde resin, melamine-formaldehyde resin or phenol-formaldehyde resin as the binder.

5. To 100% by weight of potato pulp having a moisture content of 5 to 95% by weight, as well as

6. Shaped article according to Claim 1, characterized in that the potato pulp has a moisture content of 10 to 40% by weight.

7. Shaped article according to Claim 1, characterized in that it consists of a single-layered chipboard.

8. Shaped article according to Claim 1, characterized in that it consists of a three-layered chipboard with an outer covering layer, a middle layer and an inner covering layer.

9. Process for the production of shaped articles according to Claims 1 to 7, characterized in that the IE 90355«

10. Shaped article according to Claim 1, substantially as described herein by way of Example. - 10 potato pulp is mixed with the shavings, if appropriate, and the mixture is then mixed with the binder and, if appropriate, with other additives and subsequently pressed.

11. Process for the production of shaped articles according to any of Claims 1 to 7 or Claim 10, substantially as described herein by way of Example.

12. Shaped articles prepared by a process according to Claim 9 or Claim 11.